The rhythmic contraction of the diaphragm facilitates continuous pulmonary ventilation essential for life. Adequate blood flow to the diaphragm is critical to continuously support contractile function, as an imbalance in nutritive supply and demand can lead to diaphragm insufficiency, patient morbidity, and mortality. Given oxygen supply to the diaphragm is key to its function, it is no surprise that more than 200 animal studies have investigated diaphragm blood flow ([Formula: see text]) regulation over the past century. This work has advanced our understanding of the diaphragm's circulatory control (i.e., regional blood flow heterogeneity and mechanical impediment) and response to a variety of conditions, including eupnea, exercise, hypoxia, hypercapnia, hemorrhage, mechanical ventilation, and pharmacological interventions. However, due to the relative inaccessibility of the diaphragm, few studies have been conducted in humans since [Formula: see text] measurements have historically required highly invasive and technically challenging techniques that are not conducive to routine use. Thus, our current understanding of [Formula: see text] is informed almost exclusively by animal work with conflicting findings, and its translation to humans is hindered by species-dependent variability in diaphragmatic structure and function. Novel approaches have been developed to quantify respiratory muscle blood flow in humans using minimally invasive techniques. More recently, contrast-enhanced ultrasound (CEUS) is a promising approach for quantifying [Formula: see text] in humans, independent from other respiratory muscles. Using novel approaches to quantify [Formula: see text] in humans, future research can aim to advance our understanding of [Formula: see text] in humans in health and disease, including exercise, sex-based comparisons, and critical care.

Systemic hypertension is a strong risk factor for cardiovascular, neurovascular, and renovascular diseases. Central artery stiffness is both an initiator and indicator of hypertension, thus revealing a critical relationship between the wall mechanics and hemodynamics. Mice have emerged as a critical animal model for studying effects of hypertension and much has been learned. Regardless of the specific mouse model, data on changes in cardiac function and hemodynamics are necessarily measured under anesthesia. Here, we present a new experimental-computational workflow to estimate awake cardiovascular conditions from anesthetized data, which was then used to quantify effects of chronic angiotensin II-induced hypertension relative to normotension in wild-type mice. We found that isoflurane anesthesia had a greater impact on depressing hemodynamics in angiotensin II-infused mice than in controls, which led to unexpected results when comparing anesthetized results between the two groups of mice. Through comparison of the awake simulations, however, in vivo relevant effects of angiotensin II-infusion on global and regional vascular structure, properties, and hemodynamics were found to be qualitatively consistent with expectations. Specifically, we found an increased in vivo vascular stiffness in the descending thoracic aorta and suprarenal abdominal aorta, leading to increases in pulse pressure in the distal aorta. These insights allow characterization of the impact of regionally varying vascular remodeling on hemodynamics and mouse-to-mouse variations due to induced hypertension.

The bispectral index (BIS) is an anaesthesia monitoring technique able to assess the level of central nervous system depression in humans and various animal species. In birds, it has been validated in chickens undergoing isoflurane anaesthesia. The aim of this study was to evaluate in an avian species the influence of isoflurane and sevoflurane on BIS, each at different minimum anaesthetic concentrations (MAC) multiples, alone or combined with butorphanol or medetomidine. Ten chickens (5 males and 5 females) underwent general anaesthesia with isoflurane or sevoflurane alone, and combined with either intramuscular administration of butorphanol (1 mg/kg) or medetomidine (0.1 mg/kg), in a prospective and cross-over study (i.e., 6 treatments per animal). BIS measurements were compared to heart rate (HR), non-invasive blood pressure (NIBP) and to a visual analogue scale (VAS) of anaesthesia depth.

HR was significantly increased, and both NIBP and VAS were significantly reduced, with higher gas concentrations. NIBP (but not HR or VAS) was additionally affected by the type of gas, being lower at higher concentrations of sevoflurane. Butorphanol had no additional effect, but medetomidine led to differences in HR, NIBP, and in particular a reduction in VAS. With respect to deeper level of hypnosis at higher concentrations and the absence of difference between gases, BIS measurements correlated with all other measures (except with HR, where no significant relationship was found) The difference in BIS before (BISpre) and after stimulation (BISpost) did not remain constant, but increased with increasing MAC multiples, indicating that the BISpost is not suppressed proportionately to the suppression of the BISpre values due to gas concentration. Furthermore, neither butorphanol nor medetomidine affected the BIS.

The difference of degree of central nervous system depression monitored by BIS compared with neuromuscular reflexes monitored by VAS, indicate that BIS records a level of anaesthetic depth different from the one deducted from VAS monitoring alone. BIS provided complementary information such as that medetomidine suppressed spinal reflexes without deepening the hypnotic state. As a consequence, it is concluded that BIS improves the assessment of the level of hypnosis in chickens, improving anaesthesia monitoring and anaesthesia quality in this species.

Current guidelines for rheumatoid arthritis (RA) management recommend early treatment with disease modifying antirheumatic drugs (DMARDs). However, DMARD treatment fails in 30% of patients and current monitoring methods can only detect failure after 3 to 6 months of therapy.

We investigated whether joint blood flow (BF), quantified using dynamic contrast-enhanced time-resolved near-infrared spectroscopy, can monitor disease activity and treatment response in a rat model of RA.

Ankle joint BF was measured every 5 days in eight rats with adjuvant-induced arthritis (AIA) and four healthy controls. Arthritis was allowed to progress for 20 days before rats with AIA were treated with a DMARD once every 5 days until day 40.

Time and group had separate significant main effects on joint BF; however, there was no significant interaction between time and group despite a notable difference in average joint BF on day 5. Comparison of individual blood flow measures between rats with AIA and control group animals did not reveal a clear response to treatment.

Joint BF time courses could not distinguish between rats with AIA and study controls. Heterogeneous disease response and low temporal frequency of BF measurements may have been important study limitations.

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.

Isoflurane is a widely used anesthetic, but its effects with increase in inspired concentration on cardiovascular function have not yet been clarified in rodents. Additionally, there are only a few studies comparing isoflurane-induced cardiorespiratory effects between rat strains. Thus, we investigated the differences in cardiorespiratory responsiveness to increasing concentration of inspired isoflurane in SHR/Izm, WKY/Izm and Crl:CD (SD) rats, by increasing the setting values of vaporizer's dial indicator. The rats were anesthetized with 1.5% isoflurane, and electrocardiograms, blood pressure, and respiratory rate were recorded simultaneously. Thereafter, the inspired concentration was increased stepwise to 2%, 3%, 4%, and 5%, and cardiorespiratory parameters were obtained at each concentration. Under anesthesia at more than 4%, although prolongation of the RR and PR intervals was observed in all strains, shortening of the QT_C interval was found only in SHR/Izm rats. From frequency domain analysis of heart rate variability, an increase in LF/HF ratio and a decrease of HF components were observed in SHR/Izm and WKY/Izm rats, respectively, with 5% isoflurane anesthesia. Blood pressure and heart rate were remarkably reduced in SHR/Izm rats at higher concentrations, whereas the reduction was smallest in WKY/Izm rats among the three strains examined. Respiratory rate was inspired concentration-dependently decreased in all strains. These results suggested that SHR/Izm rats are more sensitive to suppressive effects of isoflurane anesthesia on cardiovascular function among these rat strains.

The present study tested the hypothesis that the anesthetic technique will influence the changes in regional blood flow (RBF) during intraoperative cardiac tamponade.

Twenty-four dogs were divided into three equal groups: Group I, anesthesia was maintained with ketamine (25 mg.kg(-1).hr(-1)); Group II, with fentanyl and midazolam (F-M; 10 mug.kg(-1).hr(-1) and 0.5 mg.kg(-1).hr(-1), respectively); Group III with 1 minimum alveolar concentration (MAC; 1.4%) isoflurane. Radioactive microspheres were used to measure RBF in myocardium, brain, spinal cord, abdominal viscera, skeletal muscle and skin. Cardiac output (CO) was measured by thermodilution and arterial pressure with a catheter situated in the thoracic aorta. Catheters were introduced into the pericardial cavity to infuse isotonic saline and to measure intrapericardial pressure (IPP). Measurements were obtained under control conditions and during tamponade, as defined by an increase in IPP sufficient to reduce mean arterial pressure by 40%.

Tamponade caused decreases in CO and RBF that were comparable under the three anesthetics, except that RBF in subcortical regions of the brain and in the spinal cord were maintained under isoflurane but decreased under ketamine or F-M.

In dogs, intraoperative cardiac tamponade caused comparable changes in RBF under the different anesthetic techniques except that autoregulation was effective in maintaining RBF within the central nervous system only under isoflurane anesthesia. Our findings provide no compelling reason to recommend one anesthetic over the others for maintenance of anesthesia in situations with increased risk for intraoperative cardiac tamponade. However, they cannot be extrapolated to anesthesia induction in the presence of cardiac tamponade.

Splanchnic vascular hypocontractility with subsequent increased portal venous inflow leads to portal hypertension. Although the renin-angiotensin system contributes to fibrogenesis and increased hepatic resistance in patients with cirrhosis, little is known about its effects in the splanchnic vasculature, particularly those of the alternate system in which angiotensin (Ang) II is cleaved by the Ang-converting enzyme-2 (ACE2) to Ang-(1-7), which activates the G-protein-coupled Mas receptor (MasR). We investigated whether this system contributes to splanchnic vasodilatation and portal hypertension in cirrhosis.

We measured levels of renin-angiotensin system messenger RNA and proteins in splanchnic vessels from patients and rats with cirrhosis. Production of Ang-(1-7) and splanchnic vascular reactivity to Ang-(1-7) was measured in perfused mesenteric vascular beds from rats after bile-duct ligation. Ang-(1-7) and MasR were blocked in rats with cirrhosis to examine splanchnic vascular hemodynamics and portal pressure response.

Levels of ACE2 and MasR were increased in splanchnic vessels from cirrhotic patients and rats compared with healthy controls. We also observed an ACE2-dependent increase in Ang-(1-7) production. Ang-(1-7) mediated splanchnic vascular hypocontractility in ex vivo splanchnic vessels from rats with cirrhosis (but not control rats) via MasR stimulation. Identical effects were observed in the splanchnic circulation in vivo. MasR blockade reduced portal pressure, indicating that activation of this receptor in splanchnic vasculature promotes portal inflow to contribute to development of portal hypertension. In addition, the splanchnic effects of MasR required nitric oxide. Interestingly, Ang-(1-7) also decreased hepatic resistance.

In the splanchnic vessels of patients and rats with cirrhosis, increased levels of ACE2 appear to increase production of Ang-(1-7), which leads to activation of MasR and splanchnic vasodilatation in rats. This mechanism could cause vascular hypocontractility in patients with cirrhosis, and might be a therapeutic target for portal hypertension.

Hemorrhagic shock (HS) is known to induce an inflammatory response by activating the immune system. This response is mainly caused by primed polymorphonuclear granulocytes (PMNs). Trauma patients often require mechanical ventilation (MV), which can cause additional pulmonary and systemic inflammation. The aim of this study was to evaluate the role of MV in the development of systemic and pulmonary inflammation in a HS model in rats.

In male Sprague-Dawley rats, the effect of MV and HS on the systemic and pulmonary inflammatory responses was measured and compared. In five groups (control, sham, MV, HS, and MV + HS), the inflammation was measured at time point 300 min after the start of the experiment.

The systemic inflammatory response, expressed in absolute numbers of PMNs in blood and blood growth related oncogene (GRO-KC) levels, was significantly higher in MV rats compared with that in other groups. The pulmonary inflammatory response, expressed by PMNs in bronchoalveolar lavage fluid (BALF), BALF interleukin 6, BALF GRO-KC, and myeloperoxidase activity, was significantly higher in all ventilated rats compared with that in the controls or HS rats. There was, however, no additional effect of HS in MV as the inflammatory indices were similar in both groups.

Our data show that HS alone has minimal effect on the development of inflammation. MV (alone or in combination with HS) is the determining factor in inducing an inflammatory response. These results emphasize the importance of local (pulmonary) ventilation-induced damage in the development of systemic inflammation.

Colorectal surgery is commonly performed for colorectal cancer and other pathology such as diverticular and inflammatory bowel disease. Despite significant advances, such as laparoscopic techniques and multidisciplinary recovery programs, morbidity and mortality remain high and vary among surgical centers. The use of scoring systems and assessment of functional capacity may help in identifying high-risk patients and predicting complications. An understanding of perioperative factors affecting colon blood flow and oxygenation, suppression of stress response, optimal fluid therapy, and multimodal pain management are essential. These fundamental principles are more important than any specific choice of anesthetic agents. Anesthesiologists can significantly contribute to enhance recovery and improve the quality of perioperative care.

Mean arterial pressure (MAP) and specific regulation of penile blood flow are the primary determinants of an erection. While this concept is well recognized, the differential relationship between systemically acting vasoactive factors on arterial pressure and erectile responses is not well described.

The aim of this study was to determine how the modification of systemic levels of neurohumoral factors impacts on the magnitude and efficiency of the erectile response.

The main outcome measures for this study are changes in MAP and intracavernosal pressure (ICP) following electrostimulation of the cavernous nerve.

Anesthetized adult, male Sprague-Dawley rats were catheterized for measuring MAP (carotid), ICP, and drug administration (vena cava). Erections were induced via cavernous nerve electrostimulation. Vasoactive drug infusions were used to produce changes in MAP levels including: hexamethonium, angiotensin II (ANGII)±hexamethonium, methoxamine±hexamethonium, losartan, MAHMA NONOate, and terbutaline.

In general, ICP and MAP were linearly correlated regardless of treatment. Hexamethonium markedly dropped MAP and proportionately decreased the magnitude of the erectile response. ANGII or methoxamine given to hexamethonium-pretreated or untreated rats increased MAP similarly, but produced contrasting effects on erectile responses. ANGII-induced pressor responses were associated with increased erectile responses whereas all methoxamine treatments markedly decreased erectile responses. Depressor changes with losartan or terbutaline, but not MAHMA NONOate, also impacted negatively on the efficiency of the erectile responses at lower arterial pressures.

In general, the magnitude of the erectile responses was found to be dependent upon the level of MAP, although the mechanism by which arterial pressure was changed impacted substantially on the characteristics of the relationship. The major finding was that circulation-wide α-adrenoceptor stimulation was extremely deleterious to erectile responses whereas global stimulation of ANG II receptors was actually proerectile. Overall, the results indicate that neurohumoral specificity in systemic hemodynamic control is also critical in establishing the optimal erectile environment in rats.

Increased intrahepatic resistance and splanchnic blood flow cause portal hypertension in liver cirrhosis. Nonselective beta-adrenoceptor (beta-AR) antagonists have beneficial effects on hyperdynamic circulation and are in clinical use. In this context, the role of the beta(3)-AR is undefined. Here we investigated their expression and role in portal hypertension in patients and rats with liver cirrhosis. We analyzed cirrhotic human and rat tissues (liver, splanchnic vessels) and primary rat cells. Protein expression of beta(3)-AR was determined by western blot and messenger RNA (mRNA) levels by reverse-transcription polymerase chain reaction (RT-PCR). Activities of Rho-kinase and the nitric oxide (NO) effector protein kinase G (PKG) were assessed by way of substrate phosphorylation (moesin, vasodilator-stimulated phosphoprotein [VASP]). Cyclic 3',5' adenosine monophosphate (cAMP) accumulation was determined by an enzyme-immunoassay kit. The effects of selective beta(3)-AR agonists (CGP12177A, BRL37344) and antagonist (SR59230A) were investigated by collagen matrix contraction of hepatic stellate cells (HSCs), in situ liver perfusions, and in vivo hemodynamic parameters in bile duct ligation and carbon tetrachloride intoxication in cirrhotic rats. In cirrhosis of humans and rats, beta(3)-AR expression is markedly increased in hepatic and in splanchnic tissues. Stimulation of beta(3)-AR leads to relaxation of HSCs by way of cAMP accumulation, and by inhibition of Rho-kinase activity; any role of NO and its effector PKG was not observed. beta(3)-AR agonists decrease intrahepatic resistance and portal pressure in cirrhotic rats.

There is a marked hepatic and mesenteric up-regulation of beta(3)-ARs in human cirrhosis and in two different animal models of cirrhosis. The beta(3)-AR-agonists should be further evaluated for therapy of portal hypertension.

In cirrhosis, portal hypertension is maintained by splanchnic vasodilation owing to overproduction of the vasodilator nitric oxide (NO) and defective contractile signalling by Rho-kinase. NO overproduction is partially caused by bacterial translocation from the gut to mesenteric lymph nodes. However, the effects of intestinal bacterial decontamination on hyperdynamic circulation or vascular contractility are unknown. We investigated the haemodynamic and vascular effects of norfloxacin in rats with secondary biliary cirrhosis.

Cirrhosis was induced by bile duct ligation (BDL). One group was treated with norfloxacin (20 mg/kg/day, 5 days, orally). Bacterial growth in the lymph nodes was determined on blood agar plates. Invasive haemodynamic measurements were combined with coloured microspheres. Aortic contractility was assessed myographically. Protein expression/phosphorylation was examined by Western blot analysis.

Norfloxacin treatment of BDL rats abolished bacterial translocation to mesenteric lymph nodes. BDL rats had hyperdynamic circulation, including portal hypertension and splanchnic vasodilation. None of these parameters was changed by norfloxacin, although norfloxacin reduced endothelial NO synthase expression and phosphorylation. The latter was associated with a diminished activity of protein kinase G (PKG), which mediates NO-induced vasodilation. However, norfloxacin had no effect on aortic contractility to methoxamine or Ca2+, or the aortic expression of RhoA, Rho-kinase and beta-arrestin 2, or the phosphorylation of the Rho-kinase substrate moesin.

Short-term treatment of BDL rats with norfloxacin does not change hyperdynamic circulation or vascular contractility, despite reduction of PKG activity.

Extrahepatic vasodilation and increased intrahepatic vascular resistance represent attractive targets for the medical treatment of portal hypertension in liver cirrhosis. In both dysfunctions, dysregulation of the contraction-mediating Rho kinase plays an important role as it contributes to altered vasoconstrictor responsiveness. However, the mechanisms of vascular Rho kinase dysregulation in cirrhosis are insufficiently understood. They possibly involve mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK)-dependent mechanisms in extrahepatic vessels. As the multikinase inhibitor sorafenib inhibits ERK, we tested the effect of sorafenib on haemodynamics and dysregulated vascular Rho kinase in rats with secondary biliary cirrhosis.

Secondary biliary cirrhosis was induced by bile duct ligation (BDL). Sorafenib was given orally for 1 week (60 mg.kg(-1).d(-1)). Messenger RNA levels were determined by quantitative real time polymerase chain reaction, protein expressions and protein phosphorylation by Western blot analysis. Aortic contractility was studied by myographic measurements, and intrahepatic vasoregulation by using livers perfused in situ. In vivo, haemodynamic parameters were assessed invasively in combination with coloured microspheres.

In BDL rats, treatment with sorafenib decreased portal pressure, paralleled by decreases in hepatic Rho kinase expression and Rho kinase-mediated intrahepatic vascular resistance. In aortas from BDL rats, sorafenib caused up-regulation of Rho kinase and an improvement of aortic contractility. By contrast, mesenteric Rho kinase remained unaffected by sorafenib.

Intrahepatic dysregulation of vascular Rho kinase expression is controlled by sorafenib-sensitive mechanisms in rats with secondary biliary cirrhosis. Thus, sorafenib reduced portal pressure without affecting systemic blood pressure.

In cirrhosis, splanchnic vasodilation contributes to portal hypertension, subsequent renal sodium retention, and formation of ascites. Urotensin II(U-II) is a constrictor of large conductive vessels. Conversely, it relaxes mesenteric vessels, decreases glomerular filtration, and increases renal sodium retention. In patients with cirrhosis, U-II plasma levels are increased. Thus, we investigated hemodynamic and renal effects of U-II and its receptor antagonist, palosuran, in cirrhotic bile duct-ligated rats (BDL). In BDL and sham-operated rats, we studied acute effects of U-II (3 nmol/kg; intravenously) and palosuran (10 mg/kg; intravenously) and effects of oral administration of palosuran (30 mg/kg/day; 3 days) on hemodynamics and renal function. We localized U-II and U-II-receptor (UTR) in livers and portal veins by immunostaining. We determined U-II-plasma levels by enzyme-linked immunosorbent assay (ELISA), and mesenteric nitrite/nitrate-levels by Griess-reaction. RhoA/Rho-kinase and endothelial nitric oxide synthase (eNOS) pathways were determined by western blot analysis and reverse transcription polymerase chain reaction (RT-PCR) in mesenteric arteries. U-II plasma levels, as well as U-II and UTR-receptor expression in livers and portal veins of cirrhotic rats were significantly increased. U-II administration further augmented the increased portal pressure (PP) and decreased mean arterial pressure (MAP), whereas palosuran decreased PP without affecting MAP. The decrease in PP was associated with an increase in splanchnic vascular resistance. In mesenteric vessels, palosuran treatment up-regulated expression of RhoA and Rho-kinase, increased Rho-kinase-activity, and diminished nitric oxide (NO)/cyclic guanosine 3',5'-monophosphate (cGMP) signaling. Moreover, palosuran increased renal blood flow, sodium, and water excretion in BDL rats.

In BDL rats, U-II is a mediator of splanchnic vasodilation, portal hypertension and renal sodium retention. The U-II-receptor antagonist palosuran might represent a new therapeutic option in liver cirrhosis with portal hypertension.

In cirrhosis, increased RhoA/Rho-kinase signaling and decreased nitric oxide (NO) availability contribute to increased intrahepatic resistance and portal hypertension. Hepatic stellate cells (HSCs) regulate intrahepatic resistance. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) inhibit synthesis of isoprenoids, which are necessary for membrane translocation and activation of small GTPases like RhoA and Ras. Activated RhoA leads to Rho-kinase activation and NO synthase inhibition. We therefore investigated the effects of atorvastatin in cirrhotic rats and isolated HSCs. Rats with secondary biliary cirrhosis (bile duct ligation, BDL) were treated with atorvastatin (15 mg/kg per day for 7 days) or remained untreated. Hemodynamic parameters were determined in vivo (colored microspheres). Intrahepatic resistance was investigated in in situ perfused livers. Expression and phosphorylation of proteins were analyzed by RT-PCR and immunoblots. Three-dimensional stress-relaxed collagen lattice contractions of HSCs were performed after incubation with atorvastatin. Atorvastatin reduced portal pressure without affecting mean arterial pressure in vivo. This was associated with a reduction in intrahepatic resistance and reduced responsiveness of in situ-perfused cirrhotic livers to methoxamine. Furthermore, atorvastatin reduced the contraction of activated HSCs in a 3-dimensional stress-relaxed collagen lattice. In cirrhotic livers, atorvastatin significantly decreased Rho-kinase activity (moesin phosphorylation) without affecting expression of RhoA, Rho-kinase and Ras. In activated HSCs, atorvastatin inhibited the membrane association of RhoA and Ras. Furthermore, in BDL rats, atorvastatin significantly increased hepatic endothelial nitric oxide synthase (eNOS) mRNA and protein levels, phospho-eNOS, nitrite/nitrate, and the activity of the NO effector protein kinase G (PKG).

In cirrhotic rats, atorvastatin inhibits hepatic RhoA/Rho-kinase signaling and activates the NO/PKG-pathway. This lowers intrahepatic resistance, resulting in decreased portal pressure. Statins might represent a therapeutic option for portal hypertension in cirrhosis.

To compare the cardiorespiratory changes induced by equipotent concentrations of halothane (HAL), isoflurane (ISO) and sevoflurane (SEVO) before and after hemorrhage.

Prospective, randomized clinical trial.

Twenty-four healthy adult dogs weighing 15.4 +/- 3.4 kg (mean +/- SD).

Animals were randomly allocated to one of three groups (n = 8 per group). In each group, anesthesia was maintained with 1.5 minimum alveolar concentration of HAL (1.3%), ISO (1.9%) and SEVO (3.5%) in oxygen. Controlled ventilation was performed to maintain eucapnia. Cardiorespiratory variables were evaluated at baseline (between 60 and 90 minutes after induction), immediately after and 30 minutes after the withdrawal of 32 mL kg(-1) of blood (40% of the estimated blood volume) over a 30-minute period.

During baseline conditions, ISO and SEVO resulted in higher cardiac index (CI) than HAL. Heart rates were higher with SEVO at baseline, while mean arterial pressure (MAP) and mean pulmonary arterial pressure did not differ between groups. Although heart rate values were higher for ISO and SEVO after hemorrhage, only ISO resulted in a higher CI when compared with HAL. In ISO-anesthetized dogs, MAP was higher immediately after hemorrhage, and this was related to better maintenance of CI and to an increase in systemic vascular resistance index from baseline.

Although the hemodynamic responses of ISO and SEVO are similar in normovolaemic dogs, ISO results in better maintenance of circulatory function during the early period following a massive blood loss.

Inhaled anesthetics should be used judiciously in animals presented with blood loss. However, if an inhalational agent is to be used under these circumstances, ISO may provide better hemodynamic stability than SEVO or HAL.

Electromagnetic fields at millimeter wave lengths are being developed for commercial and military use at power levels that can cause temperature increases in the skin. Previous work suggests that sustained exposure to millimeter waves causes greater heating of skin, leading to faster induction of circulatory failure than exposure to environmental heat (EH). We tested this hypothesis in three separate experiments by comparing temperature changes in skin, subcutis, and colon, and the time to reach circulatory collapse (mean arterial blood pressure, 20 mmHg) in male Sprague-Dawley rats exposed to the following conditions that produced similar rates of body core heating within each experiment: (1) EH at 42 degrees C, 35 GHz at 75 mW/cm, or 94 GHz at 75 mW/cm under ketamine and xylazine anesthesia; (2) EH at 43 degrees C, 35 GHz at 90 mW/cm, or 94 GHz at 90 mW/cm under ketamine and xylazine anesthesia; and (3) EH at 42 degrees C, 35 GHz at 90 mW/cm, or 94 GHz at 75 mW/cm under isoflurane anesthesia. In all three experiments, the rate and amount of temperature increase at the subcutis and skin surface differed significantly in the rank order of 94 GHz more than 35 GHz more than EH. The time to reach circulatory collapse was significantly less only for rats exposed to 94 GHz at 90 mW/cm, the group with the greatest rate of skin and subcutis heating of all groups in this study, compared with both the 35 GHz at 90 mW/cm and the EH at 43 degrees C groups. These data indicate that body core heating is the major determinant of induction of hemodynamic collapse, and the influence of heating of the skin and subcutis becomes significant only when a certain threshold rate of heating of these tissues is exceeded.

Portal hypertension is associated with arterial hypotension and vascular hypocontractility, which persists despite elevated plasma levels of vasoconstrictors. We investigated the role of the RhoA/Rho-kinase pathway in vascular smooth muscle hypocontractility of rats with secondary biliary cirrhosis.

Aortic expressions of RhoA and Rho-kinase were analyzed in sham-operated and BDL rats by reverse-transcription polymerase chain reaction (RT-PCR) and immunoblots. Activation of aortic RhoA was examined by pull down of guanosine triphosphate (GTP)-RhoA and membrane translocation of RhoA. Rho-kinase activity was assessed as phosphorylation of its substrate, moesin. Contractility of isolated aortic rings was determined myographically. The hemodynamic effect of the Rho-kinase inhibitor (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632) was determined in vivo by measuring changes in mean arterial pressure and systemic vascular resistance (SVR) (microspheres).

Contraction of aortic rings from BDL rats was impaired in response to the alpha(1)-adrenergic receptor agonist methoxamine but not to high molar KCl. Aortic expression of RhoA was unchanged in cirrhotic rats, whereas Rho-kinase was down-regulated posttranscriptionally. Methoxamine-induced activation of RhoA as well as basal and methoxamine-induced phosphorylation of moesin were strongly reduced in aortas from cirrhotic rats. Aortic rings from cirrhotic rats precontracted with methoxamine showed an increased sensitivity to relaxation with Y-27632. The drop in SVR induced by Y-27632 was larger in cirrhotic rats than in sham-operated rats.

An impaired vascular activation of RhoA and a down-regulation of Rho-kinase might contribute to vasodilation and vascular hypocontractility in BDL-induced cirrhosis.

The aim of this study was to investigate the imipenem distribution in muscle and lung interstitial fluids by microdialysis in rats and to compare the free concentrations in tissue with the free concentrations in blood. Microdialysis probes were inserted into the jugular vein, hind leg muscle, and lung. Imipenem recoveries in these three media were determined in each rat by retrodialysis by drug period before drug administration. Imipenem was infused intravenously at a dose of 120 mg . kg-1 over 30 min, and microdialysis samples were collected for 150 min. The whole study was conducted with nonhydrated rats (n=4) and hydrated rats (n=6) while the animals were under isoflurane anesthesia. The decay of free concentrations in blood, muscle, and lung with time were monoexponential; and the concentration profiles in these three media were virtually superimposed in both groups. Accordingly, the ratios of the area under the curve (AUC) for tissue (muscle or lung) to the AUC for blood were always virtually equal to 1. Compared to values previously determined with awake rats, clearance was reduced by 2 and 1.5 in nonhydrated and hydrated rats, respectively, but the volume of distribution was unchanged. By combining microdialysis in blood and tissues, it was possible to demonstrate that free imipenem concentrations were virtually identical in blood, muscle, and lung.

Halothane, a volatile anaesthetic, produces systemic hypotension and significantly alters organ blood flow. Isometric force was recorded in isolated rat small mesenteric arteries to investigate its action on contractile response to noradrenaline, the sympathetic neurotransmitter. Halothane (1-5%) enhanced contractile response to noradrenaline in the endothelium-intact arteries, but had little influence in the endothelium-denuded arteries. However, halothane consistently inhibited the noradrenaline response in the endothelium-denuded arteries pretreated with ryanodine (10 microM). The enhancement of the contractile response to noradrenaline in the endothelium-intact arteries was unaffected by treatment with N(G)-nitro L-arginine, tetraethylammonium, apamin, charybdotoxin, indomethacin, diclofenac, nordihydroguaiaretic acid, BQ-123, BQ-788, losartan, ketanserin, or superoxide dismutase. Halothane prolonged vasorelaxation after washout of noradrenaline in the endothelium-denuded arteries. Both ryanodine and vanadate (0.1-0.3 mM), a putative inhibitor of the plasma membrane Ca2+-ATPase, also prolonged the vasorelaxation. Halothane still prolonged the vasorelaxation in the ryanodine-treated arteries, but not in the vanadate-treated arteries. Halothane decreased the pD2 value for the pCa-force relation in the beta-escin-permeabilised, endothelium-denuded arteries. Halothane appears to influence contractile response to noradrenaline through multiple actions including endothelium-dependent enhancing, endothelium-independent enhancing, and endothelium-independent inhibitory actions. Nitric oxide, endothelium-derived hyperpolarising factor, cyclooxygenase products, lipoxygenase products, endothelin-1, angiotensin-II, serotonin, and superoxide anions are not involved in the endothelium-dependent enhancement. The endothelium-independent enhancement is presumably due to its ability to stimulate Ca2+ release from the ryanodine-sensitive intracellular stores, while the endothelium-independent inhibition is due, at least in part, to depressed Ca2+-activation of contractile proteins. Halothane may inhibit the plasma membrane Ca2+-ATPase of vascular smooth muscle cells.

In cirrhosis, splanchnic and systemic vasodilatation induce a hyperdynamic circulatory dysfunction, portal hypertension and renal sodium retention. This vasodilatation is in part because of an impaired vascular response to alpha1-adrenoceptor agonists. Recently, the angiotensin II type 1-receptor antagonist losartan has been shown to attenuate portal hypertension. We hypothesized that losartan decreases portal pressure by counteracting the impaired vascular responsive to alpha1-adrenoceptor agonists.

We studied, in rats with secondary biliary cirrhosis and sham-operated rats, the effect of 0.5 and 10 mg losartan/kg x day on aortic responsiveness to alpha1-adrenoceptor stimulation with methoxamine and angiotensin II (myograph), splanchnic and systemic hemodynamics (colored microspheres), plasma noradrenaline levels and kidney function.

In cirrhotic rats, 10 mg losartan/kg x day completely inhibited aortic contractility to angiotensin II, decreased vascular resistance and arterial pressure and induced renal failure. In contrast, 0.5 mg losartan/kg x day only partially inhibited aortic contractility to angiotensin II, but improved aortic contractility to methoxamine, increased splanchnic and systemic vascular resistance, decreased portal pressure, decreased plasma norepinephrine levels and induced natriuresis.

In cirrhotic rats, losartan at a very low dose increases splanchnic vascular resistance, decreases portal pressure and improves kidney function, possibly by an increased vascular responsiveness to alpha1-adrenoceptor agonists.

In pre-clinical studies, investigation of oral formulations often necessitates the use of general anesthesia to facilitate deposition of material directly into the stomach. Since the effectiveness of intestinal drug absorption is dependent on gastric emptying (GE) and intestinal motility, drugs that influence either will also influence drug absorption. This study investigated gastrointestinal motility in rats after brief exposure to Isoflurane (ISO) general anesthesia for orogastric gavage. The use of metochlopramide was also evaluated. Twenty-five fasted rats were induced with brief ISO anesthesia (<6 min). Rats were gavaged a gelatin capsule (8mm (L) x 2.0mm (o.d.)) containing 9 mg of activated charcoal powder (gastrointestinal marker) and rapidly recovered. Gavage was performed using a 15 cm feeding device with a soft hollow tip to hold the capsule. Study included three groups (60 and 120 min recovery, metochlopramide pre-treatment with 60 min recovery) and control. Animals were sacrificed for exposure and examination of the gastrointestinal tract following the allocated recovery period. Gastrointestinal transit of charcoal was reduced approximately 50% 120 min after brief ISO anesthesia. Metochlopramide pre-treatment did not increase gastrointestinal propulsion despite increased GE. These data warrant consideration in intestinal drug absorption studies where ISO is the anesthetic of choice.

Plasma levels of adrenomedullin, a potent vasodilator peptide, are increased in cirrhotic patients, whereas its role in vascular hyporeactivity in cirrhosis has not been clarified.

Adrenomedullin expression was evaluated by radioimmunoassay and reverse-transcription polymerase chain reaction. Vascular reactivity to phenylephrine, alpha-adrenoceptor agonist, was investigated in the aortic rings from control rats and CCl-induced cirrhotic rats with ascites in the presence of the neutralizing antibody against adrenomedullin, human adrenomedullin and/or N-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor.

Plasma adrenomedullin levels were significantly higher in cirrhotic rats than in controls (16.3 +/- 2.9 versus 7.4 +/- 1.7 fmol/mL, P < 0.05) and correlated negatively with systemic arterial pressure (r = -0.62, P < 0.05). Gene expression of adrenomedullin in various organs (liver, kidney, lung) and vessels (portal vein, aorta) was enhanced in cirrhotic rats compared with controls. Neutralizing antibody against adrenomedullin ameliorated the blunted contractile response to phenylephrine in cirrhotic aorta (Rmax: 1.5 +/- 0.1 versus 1.0 +/- 0.1 g/mg tissue, P < 0.05), whereas contraction remained unchanged in control aorta (Rmax: 1.9 +/- 0.2 versus 1.9 +/- 0.2 g/mg tissue). Intravenous infusion of human adrenomedullin induced a reduction of mean arterial pressure together with an increase of serum nitrate levels, which was abolished by neutralizing antibody against adrenomedullin. Human adrenomedullin caused a blunted contractile response to phenylephrine in both control and cirrhotic aortas, which was not observed in the presence of N-nitro-L-arginine methyl ester.

These findings indicate that the overproduction of adrenomedullin may contribute to vascular hyporeactivity in cirrhosis via a release of nitric oxide.

Portal hypertension in cirrhosis is the result of increased intrahepatic vascular resistance to portal outflow as well as increased portal tributary blood flow. The angiotensin II type 1 receptor antagonist losartan has been suggested as a portal pressure-lowering drug in patients with cirrhosis.

To investigate the systemic and splanchnic haemodynamic effects of different doses of losartan.

In 35 anaesthetized rats with secondary biliary cirrhosis, 3, 10 or 30 mg of losartan kg(-1) or solvent were administered intravenously. Ten sham-operated rats served as controls. Mean arterial pressure and portal pressure were measured by catheters in the femoral artery or portal vein. Systemic and splanchnic haemodynamics and mesenterico-systemic shunt rate were determined by the coloured microsphere method.

Losartan reduced portal pressure (sham: 9.1 +/- 0.4. cirrhosis: 19.3 +/- 1.1, after 3 mg kg(-1) of losartan 16.4 +/- 0.4, after 10 mg kg(-1) of losartan 15.6 +/- 0.6, after 30 mg kg(-1) of losartan 14.9 +/- 0.6 mmHg) without reducing portal sinusoidal resistance. However, in cirrhotic rats it reduced portal tributary blood flow (sham: 4.3 +/- 0.6. cirrhosis: 8.6 +/- 1.4, after 3 mg kg(-1) of losartan 3.8 +/- 0.7, after 10 mg kg(-1) of losartan 4.7 +/- 0.5, after 30 mg kg(-1) of losartan 5.9 +/- 0.9 mmHg). This was owing either to an increase in splanchnic vascular resistance at the 3 mg kg(-1) dose or to a reduction in the splanchnic perfusion-pressure gradient secondary to a reduction in mean arterial pressure at the 10 and 30 mg kg(-1) doses (mean arterial pressure: sham: 109.7 +/- 4.8. cirrhosis: 109.4 +/- 2.8, after 3 mg kg(-1) of losartan 99.7 +/- 2.9, after 10 mg kg(-1) of losartan 89.9 +/- 3.4, after 30 mg kg(-1) of losartan 81.0 +/- 2.9 mmHg).

Low doses of losartan reduce portal hypertension by an increase in splanchnic vascular resistance without hypotensive side-effects on arterial pressure.

To characterize halothane and sevoflurane anesthesia in spontaneously breathing rats.

16 healthy male Sprague-Dawley rats.

8 rats were anesthetized with halothane and 8 with sevoflurane. Minimum alveolar concentration (MAC) was determined. Variables were recorded at anesthetic concentrations of 0.8, 1.0, 1.25, and 1.5 times the MAC of halothane and 1.0, 1.25, 1.5, and 1.75 times the MAC of sevoflurane.

Mean (+/- SEM) MAC for halothane was 1.02 +/- 0.02% and for sevoflurane was 2.99 +/- 0.19%. As sevoflurane dose increased from 1.0 to 1.75 MAC, mean arterial pressure (MAP) decreased from 103.1 +/- 5.3 to 67.9 +/- 4.6 mm Hg, and PaCO2 increased from 58.8 +/- 3.1 to 92.2 +/- 9.2 mm Hg. As halothane dose increased from 0.8 to 1.5 MAC, MAP decreased from 99 +/- 6.2 to 69.8 +/- 4.5 mm Hg, and PaCO2 increased from 59.1 +/- 2.1 to 75.9 +/- 5.2 mm Hg. Respiratory rate decreased in a dose-dependent fashion from 88.5 +/- 4.5 to 58.5 +/- 2.7 breaths/min during halothane anesthesia and from 42.3 +/- 1.8 to 30.5 +/- 4.5 breaths/min during sevoflurane anesthesia. Both groups of rats had an increase in eyelid and pupillary aperture with an increase in anesthetic dose.

An increase in PaCO2 and a decrease in MAP are clinical indicators of an increasing halothane and sevoflurane dose in unstimulated spontaneously breathing rats. Increases in eyelid aperture and pupil diameter are reliable signs of increasing depth of halothane and sevoflurane anesthesia. Decreasing respiratory rate is a clinical indicator of an increasing dose of halothane.

The present study is aimed toward a comparative real-time analysis of organ-specific characteristics of the liver, kidney and brain blood supply in the dynamics of acute massive hemorrhage in rats with different resistance to circulatory hypoxia. The survival time of experimental animals after the arrest of bleeding was used as a criterion of their resistance to acute blood loss. The rats with high resistance (HR) to hypoxia had the survival time not less than 3 h, while the rats with low resistance (LR) to hypoxia lived not more than 1.5 h. A marked decrease in arterial organ blood flow velocity and tissue perfusion of the liver, kidney and brain in LR and HR rats was observed at the end of acute massive hemorrhage in ultrasonic and Doppler flowmetry. In the post-hemorrhagic period the organ hemodynamics and microcirculation showed a tendency to a further decrease in LR rats. In HR animals the blood flow velocities in hepatic, renal and common carotid arteries were temporarily restored to 115-120, 85-90 and 60-65%, respectively, following the bleeding arrest. In the compensated phase of the post-hemorrhagic period the brain blood flow was maintained at this new post-hemorrhagic level due to autoregulatory changes in the carotid resistance. Such a response of brain blood vessels of HR rats is considered to be an adaptive response which protects the brain from autoreperfusion- and reoxygenation-induced injuries under conditions of posthemorrhagic autorestoration of tissue circulation.

Hemorrhage and volume restitution with commercially available solutions is followed by reduced blood viscosity. Consequent hemodynamic changes may arise not only from the reduced viscosity itself but also from changes in vascular geometry induced by autoregulation processes. Vascular hindrance reflects the contribution of vascular geometry to flow. Our aim was to explore the possible effects of blood volume restitution with Haemaccel or blood, on regional blood flow and vascular geometry.

Under ketamine anesthesia, blood was withdrawn at a rate of 0.3 ml/min for 15 min followed by 15 min of stabilization. The shed blood or Haemaccel was infused at the same rate and volume as used for withdrawal. Hemodynamic measurements were performed using radioactive microspheres. Blood viscosity was measured with an Ostwald viscometer. Vascular hindrance was calculated as the resistance/viscosity ratio.

Volume replacement with Haemaccel (n=10), compared to blood (n=10), was followed by increased cardiac output and portal venous inflow (37.1 +/- 9.0 and 3.1 +/- 0.5 vs 25.9 +/- 6.8 and 2.2 +/- 0.9 ml x min(-1) x 100 g bw(-1), respectively; P<0.05), decreased viscosity (2.8 +/- 1.3 vs 3.7 +/- 1.3, respectively; P<0.01) and decreased peripheral and splanchnic arteriolar resistance (3.8 +/- 1.1 and 40.9 +/- 7.6 vs 5.2 +/- 1.7 and 61.1 +/- 29.5 mmHg x ml(-1) x min x 100 g bw, respectively; P<0.05). No significant differences between the groups were observed in vascular hindrance and cardiac output distribution.

Volume replacement with Haemaccel, compared to blood, induced increase in systemic and splanchnic blood flows, reflecting mainly changes in viscosity and not in blood vessel geometry. These results suggest no significant difference in overall activation of autoregulation process between volume restitution with blood or Haemaccel.

This study aimed to evaluate the hemodynamic effects of endothelin-1 or mixed endothelin receptor antagonist, SB209670 in cirrhotic rats, and to elucidate the role of endothelin in cirrhotic portal hypertension.

Secondary biliary cirrhosis was induced by bile duct ligation. Hemodynamics were studied using the radioactive microsphere technique.

Plasma and hepatic endothelin levels in cirrhotic rats were significantly higher than those in normal rats (plasma, 9.0+/-1.3 vs. 2.6+/-0.5 pg/ml, p<0.001; liver, 74.8+/-13.3 vs. 12.6+/-2.5 pg/g wet tissue, p<0.001). Intraportal administration of endothelin-1 (3 nmol/kg) progressively raised portal pressure without an initial transient reduction, which was observed in systemic arterial pressure, in both cirrhotic and normal rats. SB209670 (5.4 micromol/kg) reduced portal pressure in cirrhotic rats (-19+/-5%, p<0.01) without modifying systemic arterial pressure and renal blood flow, but not in normal rats. This reduction was associated with reduced portal venous system resistance (vehicle, 2.5+/-0.2 vs. SB209670, 1.7+/-0.1 mmHg x min x 100 g bw/ml, p<0.01), but not with change in portal venous inflow and collateral blood flow.

Mixed endothelin antagonist, SB209670, decreased portal pressure by reducing portal venous system resistance without modifying systemic arterial pressure and renal blood flow in cirrhotic rats. This result, together with the findings that plasma and hepatic endothelin levels were elevated in cirrhotic rats and that exogenous endothelin-1 increased portal pressure, provides further support for a role of endothelin in portal hypertension and suggests a potential use of mixed endothelin antagonist in the pharmacological treatment of portal hypertension.

To examine the effect of halothane on the cytosolic Ca2+ concentration ([Ca2+]i)-tension relationship of rat aortic smooth muscle.

Rat aortic rings without endothelia were loaded with the fluorescent Ca2+ indicator, Fura PE3-AM, and then mounted in organ baths. The changes in isometric tension and [Ca2+]i were measured simultaneously. In one series ionomycin (10 nM-3 microM) was added to normal Krebs' solution cumulatively in the absence and presence of halothane (1.5%, 3%). In the other series, CaCl2 (0.3-3 mM) was added to Ca2+-free Krebs' solution including high KCl (50 mM), phenylephrine (100 nM) or prostaglandin F2alpha (PGF2alpha, 1-3 microM) in the absence and presence of halothane (1.5%, 3%). The linear part of [Ca2+]i-tension relationship was analyzed by a linear regression.

Halothane, 1.5%, had no effect on the normal [Ca2+]i-tension relationship obtained with the calcium ionophore, ionomycin (10 nM-3 microM), but halothane 3% decreased the slope of the relationship (0.239 +/- 0.037 for control and 0.110 +/- 0.010 for halothane 3%, P < 0.05). Halothane, 1.5% and 3%, did not change the [Ca2+]i-tension relationship obtained with CaCl2 (0.3-3 mM) in the presence of high KCl (50 mM) or phenylephrine (100 nM). In contrast, halothane, 3%, inhibited the intercept of [Ca2+]i-tension relationship obtained with CaCl2 (0.3-3 mM) in the presence of prostaglandin F2alpha (PGF2alpha, 1-3 microM) (45.708 +/- 4.233 for control and 26.997 +/- 2.522 for halothane 3%, P < 0.01).

Halothane decreases the Ca2+ sensitivity and that in the presence of PGF2.

Previous studies have indicated that freely transferred osteomyocutaneous flaps may fail despite anastomotic patency. While microvascular dysfunction is thought to be one of the major causes for this type of flap failure, little is known of its underlying mechanisms, probably due to the lack of adequate experimental models allowing detailed intravital microcirculatory analysis. Herein we report quantitative analysis of the microcirculation of periosteum, muscle, subcutis and skin by intravital fluorescence microscopy using an osteomyocutaneous free flap model in the hindlimb of rats. The microcirculation of the different tissues was studied after microanastomotic transfer (free flap), and was compared to that after solely elevating the tissue, mimicking a pedicled osteomyocutaneous flap. Transferred flaps, which were exposed to 1 h of ischaemia during the anastomotic procedure, showed a slight but significant decrease (P< 0.05) of functional capillary density in muscle, subcutis and skin when compared with the microcirculation of pedicled flaps, while capillary diameters, red blood cell velocity and blood flow of perfused capillaries remained almost unaffected. The decrease of functional capillary density was associated by a significant (P< 0.05) inflammatory response, as indicated by the increased number of leukocytes adherent to the endothelial lining of postcapillary venules. While the functional capillary density of periosteum was not affected by the free transfer procedure, the inflammatory response was found similar when compared with that observed in muscle and subcutis. Thus, our study indicates that even after a short 1-h ischaemic time period, capillary perfusion failure and leukocyte-endothelial cell interaction are the main events, characterising microvascular dysfunction after free transfer of osteomyocutaneous flaps. Using the model described herein, intravital microscopic analysis of the microcirculation proved an appropriate tool to study the individual microvascular response after free tissue transfer, and may thus be used to evaluate the effectiveness of novel therapeutic regimens which aim at counteracting microcirculatory dysfunction in free osteomyocutaneous flaps.

The aim of this study was to examine, in a portal hypertensive rat model, the hemodynamic changes following hemorrhage and volume restitution with blood and Haemaccel (a low viscosity, volume expander).

Portal hypertension was induced by portal vein constriction. Under ketamine anesthesia, blood was withdrawn at a constant rate of 0.3 ml/min, for 15 min followed by 15 min of stabilization. The shed blood or Haemaccel was infused at the same rate and volume used for withdrawal. Hemodynamic measurements were performed using radioactive microspheres. Blood viscosity was measured with an Ostwald viscometer. Vascular hindrance was calculated as the resistance/viscosity ratio.

Twelve rats were studied in each group. During blood withdrawal, significant reductions in arterial pressure and portal pressure were observed. Volume replacement with blood was accompanied by increased mean arterial pressure and portal pressure to baseline. Arterial pressure following volume replacement with Haemaccel was lower and portal pressure was higher than baseline (128+/-16 and 17.1+/-3.9 vs 146+/-13 and 15.9+/-3.0 mmHg, respectively; p<0.05). Volume replacement with Haemaccel, compared to blood, was followed by increased cardiac output and portal venous inflow (39.3+/-11.6 and 4.4+/-1.5 vs 28.9+/-3 and 2.9+/-0.8 ml x min(-1) x 100 g bw(-1), respectively; p<0.05), decreased hematocrit and viscosity (29.3+/-3.8% and 2.8+/-1.3 vs 35.7+/-3.4% and 4.0+/-1.3, respectively; p<0.01) and decreased peripheral and splanchnic arteriolar resistance (3.6+/-1.4 and 29.2+/-14.0 vs 5.0+/-1.4 and 43.9+/-12.7 mmHg x ml(-1) x min x 100 g bw, respectively; p<0.05). There were no significant changes in vascular hindrance in any vascular beds between the two groups.

In this model, volume replacement with Haemaccel induced an increase in cardiac output and portal venous inflow, thus preventing the reduction in portal pressure which might be expected when viscosity is reduced.

To review the effects of halogenated and intravenous anaesthetics on arterial vasoreactivity.

Articles were obtained from a MEDLINE review (search terms: 'vascular smooth muscle, endothelium' used separately or associated with following anaesthetic agents: 'halothane, isoflurane, enflurane, desflurane, sevoflurane, thiopentone, propofol, ketamine, etomidate'. Other sources included review articles and textbooks.

All experimental studies published since 1975 were analysed and pertinent data extracted.

Within the vascular wall, arterial vasoreactivity involves the endothelium and the vascular smooth muscle. In vivo, arterial vasoreactivity is regulated by neuronal, hormonal, and metabolic factors. In vitro, the direct action of anaesthetic agents on the vessel can be studied in the absence of such factors. In vitro studies with arterial rings have shown that inhalational anaesthetics directly decrease endothelium-independent contraction induced by various pharmacological agents. This direct effect of anaesthetics results from a decrease in intracellular calcium, mainly caused by an inhibition of transsarcoplasmic calcium influx. Volatile anaesthetics decrease endothelium-dependent vasorelaxation at a site(s) within the nitric oxide (NO) signalling pathway, located downstream from the NO-related receptors and upstream from guanylyl cyclase. They may also decrease endothelium-independent vasorelaxation by inhibiting NO activation of guanylate cyclase. Intravenous anaesthetics, such as propofol, barbiturates, ketamine and etomidate also decrease vasoconstriction by various degrees. Propofol is the most potent inhibitor of vasoconstriction and thiopental the least one. All these IV anaesthetics have been shown to inhibit in some circumstances both endothelium-dependent and -independent vasorelaxation. Further studies are required to enable a better understanding of the mechanism and the site of action of these vascular effects of anaesthetics. For example, the investigation of the effects of anaesthetic agents on vascular reactivity in diseases associated with endothelial dysfunction may indirectly provide insight into the role of endothelium.

Herein, we report a new model, which allows comparative study of the microcirculation of different peripheral tissues, i.e., periosteum, skeletal muscle, subcutis, and skin. Using dextran-insensitive Wistar rats gracilis and semitendinosus muscles of the left hindlimb were prepared in association with their appertaining tibial fragments, subcutis, and skin. Blood supply was guaranteed by the femoral artery via the saphenous vessels. High-resolution intravital epi-illumination microscopy of the two muscles displayed the typical microvascular architecture with the capillaries running in parallel to each other (capillary density (CD) 128.4 +/- 4.5 cm-1). In subcutis and skin, capillaries were found arranged as interconnecting mesh-like networks with a density, which was significantly higher (P < 0.05) in subcutis (191.0 +/- 5.5 cm-1) compared with skin (108.9 +/- 3.3 cm-1). Analysis of periosteal tissue revealed two distinct types of arrangements of microvascular architecture. Adjacent to the major feeding and draining vessels of the periosteum, capillaries were organized in densely meshed shunt-like networks, revealing the highest capillary density (242.7 +/- 13.2 cm-1; P < 0.05) of all tissues studied. Periosteal capillaries distant from the major feeding and draining vessels were arranged in parallel to the longitudinal axis of the tibial bone and presented with a density similar to that of the skeletal muscle (128. 6 +/- 9.4 cm-1). Topical application of acetylcholine for analysis of physiological reactivity of the microvasculature showed dose-dependent arteriolar dilation. Moreover, a 3-min upstream femoral artery occlusion demonstrated an appropriate hyperemic response in all tissues studied, indicating intact myogenic control. A prolonged period of ischemia (120 min) followed by reperfusion (60 min) caused massive (P < 0.05) leukocyte-endothelial cell interaction in postcapillary venules, similarly as reported in other microvascular tissue preparations. We propose that the model presented provides a good approach to all peripheral tissues for both the analysis of the physiology of tissue-confined microvascular control and the development of novel therapeutic strategies to counteract manifestation of nutritional dysfunction and inflammatory response in disease.

Hemoglobin-based oxygen carriers are designed to replace blood volume and to increase oxygen delivery to tissues after blood loss. The goals of the present study were two-fold: a) to determine the systemic and regional vascular effects of resuscitation with recombinant human hemoglobin (rHb1.1) in rats during controlled hemorrhage; and b) to determine whether nitric oxide (NO) or prostaglandins were involved in the observed responses.

Paralyzed, ventilated rats were hemorrhaged (18 mL blood/kg body weight) during halothane anesthesia and allowed to stabilize for 30 mins. Systemic and regional hemodynamics and oxygen delivery were monitored at three time points, using the radioactive microsphere method. Microspheres were first infused at the end of the hemorrhage stabilization period (t=0 min). rHb1.1 (1 g/kg body weight) or rHb1.1 diluent (phosphate buffered saline, 36 mL/kg body weight) were infused over 20 mins and microspheres were administered again, 30 mins later (t=50 mins). Saline (0.5 mL), indomethacin (5 mg/kg to inhibit cyclooxygenase), or NG-monomethyl-L-arginine (L-NMMA, 100 mg/kg, to inhibit NO synthase) were then infused in rHb1.1-treated rats and microspheres injected once more (t=80 mins).

Research laboratory.

Male Wistar rats (n=37).

Recombinant human hemoglobin (rHb1.1), rHb1.1 diluent (phosphate buffered saline) resuscitation of hemorrhaged rats. Saline, L-NMMA, or indomethacin treatment after resuscitation.

Resuscitation with rHb1.1 increased mean arterial pressure (MAP), cardiac output, and systemic oxygen delivery significantly when compared with diluent. After rHb1.1 resuscitation, regional blood flows were significantly increased in skin, kidney, spleen, and heart compared with diluent resuscitation. Compared with saline treatment after rHb1.1 resuscitation, L-NMMA increased MAP and regional resistances in virtually all tissues; indomethacin did not alter MAP, but increased resistance in the brain.

These data indicate that rHb1.1 resuscitation was more effective than diluent in improving systemic and regional hemodynamics and oxygen delivery, suggesting that rHb1.1 may be of benefit in the treatment of acute blood loss. Increased resistance after L-NMMA in the presence of rHb1.1 indicated that rHb1.1 resuscitation did not eliminate NO dependent circulatory control. Increased resistance after indomethacin in brain indicated that vasodilator prostanoids were important in regulating vascular resistance in these tissues after rHb1.1 resuscitation.

The goals of this study were to determine the effects of recombinant human hemoglobin (rHb1.1, 1 g/kg i.v.) on systemic hemodynamics, regional blood flows, and regional vascular resistances in rats. Cardiac output (CO) and regional blood flow in 13 tissues were determined by using the radiolabeled-microsphere method during halothane anesthesia. Microspheres were injected at three time points: before (control, t = 0), t = 30 [10 min after a 20-min infusion of vehicle (diluent) or rHb1.1], and at t = 120 min. Infusion of diluent did not alter CO, heart rate (HR), mean arterial pressure (MAP), or systemic vascular resistance (SVR) and had minimal effects on regional blood flows. Infusion of rHb1.1 did not alter CO or HR but did increase MAP and SVR compared with diluent. Infusion of rHb1.1 increased blood flow to the heart and decreased blood flow to the gastrointestinal tract (GIT) and liver. Compared with the corresponding values in the diluent-treated rats, resistance was increased after rHb1.1 in spleen, kidney, and hepatic artery. In conclusion, rHb1.1 administration increased MAP and SVR. The vasoconstriction was heterogeneous and was associated with increased coronary blood flow and with increased regional resistance in kidney, spleen, and hepatic artery, compared with diluent-infused controls.

During nicardipine induced hypotension, different inhalational anaesthetics may have different effects on haemodynamic variables, sympathetic function and drug metabolism. Therefore, the haemodynamic effects and pharmacokinetics of nicardipine were studied in the presence of the three inhalation anaesthetics enflurane, isoflurane and sevoflurane.

Thirty patients scheduled for neurosurgery were randomly assigned to one of three anaesthetic techniques: enflurane, isoflurane or sevoflurane. Nicardipine (0.017 mg.kg-1) was administered during stable anaesthesia and the following measurements made for 30 min: blood pressure, heart rate, and plasma concentration of norepinephrine, epinephrine and nicardipine.

With sevoflurane, plasma concentrations of nicardipine, five minutes after administration, (39.8 +/- 3.5 ng.ml-1, mean +/- SEM) were higher (P < 0.05) than in the other two groups (28.3 +/- 2.9 ng.ml-1, 32.6 +/- 4.3 ng.ml-1, enflurane and isoflurane, respectively). With isoflurane, the approximated half-life of nicardipine (14 +/- 4 min) was shorter and clearance (2.1 +/- 0.3 l.min-1) more rapid. Peak heart rates were similar in all groups but elevated rates continued longer with isoflurane (> 30 min). Nicardipine-induced reduction in blood pressure was greater with sevoflurane but low pressures persisted for longer with isoflurane. Plasma catecholamine concentrations increased with isoflurane and enflurane, but not with sevoflurane: considerably higher epinephrine concentrations were seen with isoflurane.

This study showed that the action of nicardipine is modified by different inhalational anaesthetic agents. Nicardipine has a prolonged duration of action in the presence of isoflurane and produces greater initial hypotension with sevoflurane.

We studied the effects of halothane versus isoflurane on the phosphoenergetic state and intracellular pH (pHi) of the rat liver using in vivo 31P nuclear magnetic resonance (NMR) spectroscopy during and after hemorrhagic shock. Seventeen rats were anesthetized with 1 minimum alveolar anesthetic concentration of halothane or isoflurane. The mean arterial blood pressure was reduced to 40 mm Hg and maintained at this level for 45 min by withdrawing blood from the common carotid artery. The shed blood was then returned slowly. In vivo 31P NMR spectra were consecutively collected throughout the study. The phosphoenergetic state of the liver was evaluated from the changes in adenosine triphosphate (ATP) and inorganic phosphate (P(i)) levels. pHi was calculated from the chemical shifts of P(i) and alpha-ATP peaks. During hemorrhagic shock, beta-ATP decreased to 35% and 45%, and P(i) increased to 300% and 230% of their initial values in the halothane and isoflurane groups, respectively. Intracellular acidosis was more severe in the halothane group. The recoveries of beta-ATP and P(i) were better in the isoflurane group. Halothane showed a more detrimental effect than isoflurane on the hepatic phosphoenergetic level during and after hemorrhagic shock.

The distribution of tritiated dihydromicrocystin [3H]2H-MCLR was studied in anesthetized specific-pathogen-free pigs. Two doses were administered i.m. and one dose was given via an isolated ileal loop. At 4 hr after i.v. administration of the toxin at 25 micrograms/kg, 64.6% of the total dose (%TD) was located in the liver, with smaller amounts distributed to the kidneys (1.2% TD), lungs (1.75% TD), heart (0.22% TD), ileum (0.13% TD) and spleen (0.04% TD). A similar distribution was found at 4 hr postdosing in pigs given 75 micrograms/kg, although the liver contained a lower fraction of the total dose, at 46.99% TD, and the kidneys had somewhat more, at 2.19% TD, than the low dose. At the high dose, the fractions of the amount given accounted for by the lungs (0.55% TD), heart (0.23% TD), ileum (0.20% TD) and spleen (0.07% TD) were similar to those at the low dose. The livers of the pigs given 75 micrograms/kg via the ileal loop, at 5 hr postdosing, contained 49.5% TD and the ileum had 33.94% TD. Smaller amounts were distributed to kidneys (1.04% TD), lungs (0.65% TD), heart (0.81% TD) and spleen (0.16% TD). The livers of both groups dosed at 75 micrograms/kg contained higher concentrations of toxin, but lower percentages of the total dose, than the livers of pigs dosed at 25 micrograms/kg. Larger increases in serum arginase in the two 75 micrograms/kg groups were associated with histological evidence of more severe liver damage than at the 25 micrograms/kg dose. Analysis of radiolabeled compounds from hepatic tissue using fast atom bombardment mass spectrometry determined that the primary constituent was [3H]2H-MCLR, but two minor radioactive components were also isolated. These findings indicate that [3H]2H-MCLR is rapidly concentrated in the liver of swine, whether given i.v. or via an isolated ileal loop, that at extremely toxic doses uptake is slowed, and that it is as toxicologically active as the parent compound.

The toxicokinetics of tritiated dihydromicrocystin-LR ([3H]2H-MCLR) were studied in anesthetized, specific-pathogen-free pigs. Pigs were dosed with radiolabeled plus non-labeled 2H-MCLR at 25 or 75 micrograms/kg i.v., or via an isolated ileal loop at 75 micrograms/kg. The i.v. doses were rapidly removed from the blood. At either i.v. dose, more than half the radiolabel from [3H]2H-MCLR present in the blood at 1 min postdosing was cleared by 6 min. The blood clearance at the 75 micrograms/kg dose was slower than at the 25 micrograms/kg dose. Accordingly, at the high dose, the concentrations of the toxin in blood were disproportionately higher from 10 min after dosing until the study ended 4 hr later. The decreased clearance is presumably due to decreased elimination from the blood as a consequence of the hepatic injury that was observed histologically. Following administration of [3H]2H-MCLR at 75 micrograms/kg via the ileum, the maximal toxin concentration in blood was achieved at 90 min after dosing. At that time the [3H]2H-MCLR concentration in portal venous blood was 3.6 times higher than in peripheral venous blood. Although bile production varied, following i.v. dosing radioactivity was detected in bile as early as 12 min postdosing in one animal. This study demonstrated that [3H]2H-MCLR is rapidly removed from the blood of anesthetized swine and that excretion of the radiolabel into bile may begin within 30 min of dosing.

Intrinsic regulation of hepatic blood flow is mediated only through the hepatic artery because the liver is not able to directly regulate portal vein blood flow. Hepatic metabolic activity does not affect hepatic artery flow. Although the hepatic artery is affected by sympathetic nerves and blood-borne agents, the intrinsic regulation of the hepatic artery can be demonstrated if these factors are controlled. The primary intrinsic regulator of the hepatic artery is the hepatic arterial buffer response, which is the inverse response of the hepatic artery to changes in portal vein flow. The hepatic arterial buffer response is sufficiently powerful that doubling portal vein flow leads to maximal constriction in the hepatic artery, while low portal vein flow can result in maximal dilation. The mechanism of the hepatic arterial buffer response is based on adenosine washout, whereby adenosine is produced at a constant rate, independent of oxygen supply or demand, and secreted into a small fluid compartment that surrounds the hepatic arterial resistance vessels. If portal vein flow decreases, less adenosine is washed away into the portal blood and the accumulated adenosine leads to hepatic arterial dilation. Similarly, hepatic arterial autoregulation operates by the same mechanism, whereby a decrease in arterial pressure leads to a decrease in hepatic arterial flow, thus resulting in less adenosine washout into the hepatic artery blood. The accumulated adenosine leads to hepatic artery dilation. These intrinsic regulatory mechanisms tend to maintain total hepatic blood flow at a constant level, thus stabilizing hepatic clearance of hormones, venous return, and cardiac output.