Blood Lactate

Failing oxygen delivery leads to anaerobic respiration which generates lactate [22].

A lactate level of greater than 4mmol/l is associated with increased ICU admission and mortality in normotensive patients with sepsis. Those with higher lactate clearance at 6 hours have an improved outcome [23].

It is unclear whether or not lactate levels on admission are a useful predictor of outcome in trauma patients [24-25]. Normalisation of lactate with resuscitation does correlate with improved survival in trauma [26], surgical [27] and post-cardiac arrest patients [28] but the timescale over which normalisation occurred in these studies (24-48 hours) makes the existing evidence less relevant to initial resuscitation in the ED setting.

Base excess and bicarbonate levels offer some guidance to the degree of compromise and adequacy of resuscitation but they can be normal in a proportion of patients with significantly abnormal lactate levels in sepsis [29]. Similarly, anion gap has been shown to be a poor marker for lactic acidosis in the ED [30].

Learning bite

Blood lactate is a useful marker of severity in shock states.