Revisiting acute kidney injury outcomes in traumatic brain injury

Table 1 Common biomarkers for acute kidney injury in traumatic brain injury

Biomarker	Specimen sample	Remarks
Neutrophil gelatinase-associated lipocalin	Plasma and urine	Released from damaged tubular epithelial cells
Kidney injury molecule 1	Urine	Transmembrane glycoprotein released from damaged tubular epithelial cells
Liver-type fatty acid-binding protein	Plasma and urine	14 kDa cytoplasmic transporter for free fatty acids in proximal tubular epithelial cells
Interleukin-18	Urine	Pro-inflammatory cytokine released from stressed proximal tubular epithelial cells
Tissue inhibitor of metalloproteinases-2; insulin-like growth factor-binding protein 7 (NephroCheck™)	Urine	Metalloproteinases released from stressed tubular epithelial cells during cell cycle arrest

Table 2 Risk-stratification tools for acute kidney injury in traumatic brain injury

Risk-stratification tool	Components	Cut-off/range	Remarks
Haines model	Key variables: First serum creatinine (around ICU admission), first phosphate (around ICU admission), units of blood transfused in the first 24 hours, age, Charlson comorbidity index	Range: 0-31	This model was developed specifically for trauma patients admitted to critical care
RAI	RAI = risk score × injury score. Risk score (patient context/risk strata), point values are assigned to various risk factors, such as: Admission to an ICU, solid organ or stem cell transplantation, use of mechanical ventilation, use of inotropes or vasopressors, other severe comorbidities (in modified adult versions). Injury score (early signs of loss of function). It usually incorporates the worse of two parameters: Change in serum creatinine and extent of fluid overload	Cut-off ≥ 8: Renal angina positive. Range: 1-40	The RAI is designed for pediatric critically ill patients. The modified RAI is used for critically ill adults
McMahon score	Key variables at admission: Age (years), sex, initial creatinine (mg/dL), initial calcium (mg/dL), initial creatine kinase (U/L), initial phosphate (mg/dL), initial bicarbonate (mEq/L), etiology (rhabdomyolysis secondary to seizure, syncope, exercise, statin, or myositis)	Cut-off ≥ 6: Indicates a higher risk of serious adverse outcomes, including AKI requiring RRT	This score is to predict the risk of severe AKI requiring RRT or mortality in patients with rhabdomyolysis

AKI: Acute kidney injury; ICU: Intensive care unit; RAI: Renal angina index; RRT: Renal replacement therapy.