Dynamic changes in lactate and blood acid–base status during cardiopulmonary resuscitation and clinical outcomes in adult cardiac arrest patients: a prospective study

• Serial point-of-care blood testing every 10 minutes was used to track metabolic changes during CPR. • Dynamic changes in lactate and blood pH during CPR were significantly associated with clinical outcomes. • Decreasing lactate levels during CPR was associated with higher likelihood of sustained ROSC and survival. • Increasing blood pH during CPR was associated with higher likelihood of sustained ROSC. Dynamic physiological changes during cardiopulmonary resuscitation (CPR) may provide useful information about resuscitation outcomes. Lactate and blood pH levels change during cardiac arrest because of altered metabolism and perfusion. This study evaluated whether these changes during CPR were associated with clinical outcomes in patients with cardiac arrest. Adult patients with out-of-hospital or emergency department cardiac arrest who underwent CPR with repeated peripheral venous point-of-care testing (POCT) were included. Blood samples were obtained as soon as possible after recognition of cardiac arrest and at approximately 10-minute intervals during ongoing CPR. Dynamic changes in lactate and pH were analysed using mixed-effects models, and associations with clinical outcomes were evaluated using multivariable logistic regression. A total of 160 patients were included. Patients with sustained return of spontaneous circulation (ROSC) showed stable or decreasing lactate levels and increasing pH over time, whereas those without sustained ROSC showed rising lactate levels and worsening acidosis. Each 1 mmol/L decrease in lactate was independently associated with sustained ROSC (adjusted OR 1.16, 95% CI 1.05–1.28) and survival to hospital discharge (adjusted OR 1.16, 95% CI 1.01–1.32). Increases in pH were also associated with sustained ROSC. No metabolic parameter was associated with favourable neurological outcome. Serial changes in lactate and blood pH during CPR were associated with resuscitation outcomes in adult patients with cardiac arrest. More favourable metabolic trends were associated with sustained ROSC and survival to hospital discharge, but not with favourable neurological outcome.