Propofol Infusion and Lactic Acidosis

Abstract

We read with interest the retrospective study from Cravens et al. 1about propofol infusion syndrome. The authors reported a high incidence of slight metabolic acidosis during prolonged propofol infusion in patients who received a total dose of approximately 20 mg/kg.The main cause of propofol infusion syndrome would be cumulative high-dose propofol, whereas low doses would be safe.2–5However, there is a lack of studies looking for acidosis related to propofol infusion, and prospective studies are needed to confirm the relation between high-dose propofol and acidosis and to guarantee the safety of low-dose propofol routinely used for sedation or anesthesia. Regarding the latter, our group recently performed a prospective randomized trial in 42 patients scheduled to undergo thoracotomy to evaluate the effects of almitrine and inhaled nitric oxide on oxygenation.6Arterial blood gases and lactic acid were determined in all patients: the former because arterial oxygen tension was the main variable, and the latter to discard lactic acidosis that could be an eventual complication of almitrine administration.7,8All of the patients in the study received intravenous anesthesia with propofol and remifentanil.6The research protocol and the administration of propofol were strictly standardized. In all of the patients, anesthesia was induced with 1 mg · kg−1· h−1propofol and maintained with 3 mg · kg−1· h−1propofol, so that all of the patients received an average dose of 6 mg/kg propofol.Arterial pH and lactic acid concentrations did not significantly change during the study, remaining within the normal range in all patients (7.35–7.45 and 0.5–1.6 mm, respectively).6These results suggest that our patients were not at risk of propofol infusion syndrome after receiving approximately a third of the dose administered by Cravens et al. 1In conclusion, we did not observe lactic acidosis in patients receiving low-dose propofol. These results can be useful to support the safety of short-duration, low-dose propofol, strengthening the hypothesis that acidosis after propofol infusion would be related to cumulative high doses of the drug.*Hospital Universitari del Mar, Institut Municipal d’Investigacions Mèdiques, Universitat Autònoma de Barcelona, Barcelona, Spain. lgallart@imas.imim.es