Association of serum lactate with outcome after out-of-hospital cardiac arrest treated with therapeutic hypothermia.

Aims: Lactate reflects hypoxic insult in many conditions and is considered as a prognosis factor. But, after cardiac arrest, its interest is still debated. Our study aimed to assess the prognosis value of lactate in out-of-hospital cardiac arrest patients treated with therapeutic hypothermia.

Methods: This retrospective observational study included out-of-hospital cardiac arrest patients treated with therapeutic hypothermia in four ICUs. Lactate levels were compared at different times during the first 24 hours according to outcome at ICU discharge and to the type of death (multiorgan or neurologic failure).

Results: Two hundred and seventy-two patients were included, 89 good outcome and 183 poor outcome. In the latter group, 171 patients died, from multiorgan failure in 30% and neurologic failure in 70%. Lactate levels were higher in the poor compared to the good outcome patients at admission (5.4 (3.3-9.4) vs. 2.2 (1.5-3.6) mmol/L; p<0.01), 12 hours (2.5 (1.6-4.7) vs. 1.4 (1.0-2.2) mmol/L; p<0.01) and 24 hours (1.8 (1.1-2.8) vs. 1.3 (0.9-2.1) mmol/L; p<0.01). Patients succumbing from multiorgan failure exhibited higher lactate levels compared to those dying from neurologic failure at admission (7.9 (3.9-12.0) vs. 5.2 (3.3-8.8) mmol/L; p<0.01), H12 (4.9 (2.1-8.9) vs. 2.2 (1.4-3.4) mmol/L; p<0.01) and H24 (3.3 (1.8-5.5) vs. 1.4 (1.1-2.5) mmol/L; p<0.01). Initial lactate levels showed an increasing proportion of poor outcome from the first to fourth quartile.

Conclusions: After out-of-hospital cardiac arrest treated with therapeutic hypothermia, lactate levels during the first 24 hours seem linked with ICU outcome. Patients dying from multiorgan failure exhibit higher initial lactate concentrations than patients succumbing from neurological failure.