Blood lactate levels, base excess values and lactic acidosis predict short-term and long-term survival in patients admitted to the ICU after and out-of-hospital cardiac arrest

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Background Global hypoperfusion causes tissue hypoxia, resulting in overproduction of lactate because of impaired mitochondrial oxidation, causing lactic acidosis (LA). Base excess (BE) is defined as the amount of acid or base required to return the pH to 7.4 in the setting of a normal Paco2 and is therefore related to the degree of acid production following injury. Purpose Our hypothesis was that lactate levels, BE levels and occurrence of LA on admission could help in early risk stratification in patients admitted to the ICU after an out-of-hospital cardiac arrest (OHCA). Methods we enrolled 171 consecutive patients resuscitated from an OHCA and admitted to ICU at our center from September 2017 to April 2021. Blood gas analysis on admission was available for 140 patients [77%male, mean age 60 (18-90) years, 54% with first shockable rhythm, median number of shocks delivered 1 (0-14), median dose of adrenaline administered 3 mg (0-12), 26% received amiodarone, median cardiac arrest duration 38 min (IQR 22-74 min)]. Patients with low lactate levels were compared with patients with high lactate levels (cutoff 2 mmol/l as per standard practice), patients with low BE levels were compared with patients with high BE levels (cutoff -8.5 mmol/l, median value) and patients with LA were compared with patients without LA (defined as pH <7.36 and lactate>2mmol/). Survival with good neurological outcome (CPC 1-2) at ICU discharge and 30-day survival were investigated for each group with chi-squared test. Then, one-year survival was investigated for each group with Kaplan-Meier analysis. Results Patients with low BE (< -8.5 mmol/l) had a significantly lower survival with good neurological outcome at ICU discharge (p=0.0017), lower survival at 30 days (p < 0.0001) and 365 days (p<0.0001) compared to patients with high BE (> - 8.5 mmol/l). Low lactate levels (< 2 mmol/L) were associated with higher survival with good neurological outcome at ICU discharge (p< 0.0001), higher survival at 30 days (p < 0.0001) and 365 days (p = 0.0002) compared to higher lactate levels (> 2 mmol/l). The occurrence of LA on admission was significantly associated with lower survival with good neurological outcome at ICU discharge (p=0.001), lower 30-days survival (p=0.001) and 365-days survival (p<0.0001). Conclusion high blood lactate levels, low base excess and lactic acidosis predict short-term and long-term survival in patients admitted to the ICU after an OHCA. These results could help clinician in the identification of populations with different risk profile with the first blood gas analysis obtained at ICU admission.