Facing the challenge of venous thromboembolism prevention in patients undergoing major abdominal surgical procedures for gastrointestinal cancer

Table 1 Diagnostic modalities applied for deep vein thrombosis detection

Deep vein thrombosis	U/S (B-mode)	U/S (Doppler)	Venography	Impedance plethysmography	CTV	MRI	Radiolabeled peptides
Mechanism of action	Veins with thrombi do not compress	Absent or abnormal blood flow when a thrombus is present	Pedal vein cannulation and injection of contrast material	Measures electrical resistance of the calf reflecting blood volume change	Spiral multidetector CT venography from popliteal fossa to the pelvis	-	Radiolabeled peptides that bind to various components of a thrombus
Sensitivity and specificity	95%	95%	100%	Sensitive and specific in proximal vein thrombosis	-	-	-
Advantages	Non-invasiveness Absence of radiation or contrast material	Non-invasiveness Absence of radiation or contrast material	High sensitivity and specificity	-	-	Ileac vein or inferior vena cava thrombosis, when CT venography is contraindicated or technically inadequate	Apcitide, a technetium-labeled platelet glycoprotein IIb/IIIa receptor antagonist
Disadvantages	Obesity, small peripheral thrombi, asymptomatic disease	Obesity, small peripheral thrombi asymptomatic disease	Invasiveness Hypersensitivity reactions Renal toxicity	-	Correlation with sonographic findings	-	Expensive

CTV: Computed tomography venography; MRI: Magnetic resonance imaging.

Table 2 Imaging modalities for pulmonary embolism verification

PE	ECG	CTPA	V/Q Scan	MRA
Findings	Sinus tachycardia Non-specific ST-T disorders S1Q3T3 pattern Atrial fibrillation Right heart strain	Intraluminal filling defect of pulmonary artery after injection of contrast material	Ventilated area not perfused	Increased signal intensity of pulmonary thrombi within pulmonary artery after injection of gadolinium
Advantages	Immediate Costless	Criterion standard for diagnosis	Radiation dose lower than CTPA	High sensitivity and specificity for central, lobar, and segmental emboli
Disadvantages	Low sensitivity and specificity	Invasiveness Hypersensitivity reactions Renal toxicity	-	Inadequate for subsegmental emboli

CTPA: CT pulmonary angiography; V/Q: Ventilation/perfusion; MRA: Magnetic resonance angiography.

Table 3 Comparative evaluation of mechanism of action and contra-indications of novel oral anticoagulants

Novel oral anticoagulants	Dabigatran	Rivaroxaban	Apixaban	Edoxaban
Mechanism of action	Direct thrombin (factor IIa) inhibitor	Direct factor Xa inhibitor	Direct factor Xa inhibitor	Direct factor Xa inhibitor
Route of administration	Per os	Per os	Per os	Per os
Half-life	12-14 h	7-11 h	12 h	8-10 h
Bioavailability	3%-7%	80%-100%	50%	62%
Metabolism	P-glycoprotein	P-glycoprotein Cytochrome P450 system (CYP3A4)	P-glycoprotein Cytochrome P450 system (CYP3A4)	P-glycoprotein Cytochrome P450 system (CYP3A4)
Excretion	Urine (80%)	Urine and HBR	Urine (25%)	Primarily: HBR Secondarily: Urine
Contraindication	CrCl < 30 mL/min	CrCl < 30 mL/min Hemodialysis Child Pugh B and C stage cirrhosis	CrCl < 15 mL/min
FDA approval	VTE prophylaxis after hip and knee arthroplasty, Non valvular atrial fibrillation VTE treatment	VTE prophylaxis after hip and knee arthroplasty, Non valvular atrial fibrillation VTE treatment	Non valvular atrial fibrillation VTE treatment and prevention after major orthopedic surgery	Non valvular atrial fibrillation VTE treatment and prevention after major orthopedic surgery
Clinical trials	Non-inferiority to warfarin Superiority to placebo	Non-inferiority to VKA/LMWH Superiority to placebo	-
Dosage	100-150 mg × 2/24 h	10-30 mg × 1/24 h	2.5-5 mg × 2/24 h	15-30 mg × 1/24 h

HBR: Hepatobiliary route; VTE: Venous thromboembolism; VKA: Vitamin K antagonists; LMWH: Low molecular weight heparin.