(Grade 1B)Rationale Hct example assays are part of the basic diagnostic work-up for trauma patients. The diagnostic value of the Hct for detecting trauma patients with severe injury and occult bleeding sources has been a topic of debate in the past decade [111-113]. A major limit of the Hct’s diagnostic value is the confounding influence of resuscitative measures on the Hct due to administration of intravenous fluids and red cell concentrates [114-116]. In addition, initial Hct does not accurately reflect blood loss because patients bleed whole blood and compensatory mechanisms that move fluids from interstitial space require time and are not reflected in initial Hct measurements. A retrospective study of 524 trauma patients determined a low sensitivity (0.

5) of the initial Hct on admission for detecting those patients with traumatic hemorrhage requiring surgical intervention [113]. The concept of the low sensitivity of initial Hct for the detection of severe bleeding has recently been challenged. In a retrospective study of 196 trauma patients, Ryan et al. [117] found that Hct at admission closely correlates with haemorrhagic shock. However, this study included severe cases requiring emergency surgery only (most with penetrating injuries), and may not be applicable to the general trauma patient population. Two prospective observational diagnostic studies determined the sensitivity of serial Hct measurements for detecting patients with severe injury [111,112]. Decreasing serial Hct measurements may reflect continued bleeding; however, the patient with significant bleeding may maintain his or her serial Hct.

Serum lactate and base deficitRecommendation 11 We recommend either serum lactate or base deficit measurements as sensitive tests to estimate and monitor the extent of bleeding and shock. (Grade 1B)Rationale Serum lactate has been used as a diagnostic parameter and prognostic marker of haemorrhagic shock since the 1960s [118]. The amount of lactate produced by anaerobic glycolysis is an indirect marker of oxygen debt, tissue hypoperfusion and the severity of haemorrhagic shock [119-122]. Similarly, base deficit values derived from arterial blood gas analysis provide an indirect estimation of global tissue acidosis due to impaired perfusion [119,121]. Vincent and colleagues [123] showed the value of serial lactate measurements for predicting survival in a prospective study in patients with circulatory shock.

This study showed that changes in lactate concentrations provide an early and objective evaluation of a patient’s response to therapy and suggested that repeated lactate determinations represent a reliable prognostic AV-951 index for patients with circulatory shock [123]. Abramson and colleagues [124] performed a prospective observational study in patients with multiple trauma to evaluate the correlation between lactate clearance and survival.