Among patients who survived out-of-hospital cardiac arrest (OHCA), relatively high levels of serum sodium 24 hours after the return of spontaneous circulation (ROSC) were associated with adverse long-term neurological outcomes, according to study findings published in The American Journal of Emergency Medicine.
Swelling of the brain following cardiac arrest often leads to poor neurological outcomes. Such swelling may be altered by increased serum osmolarity. Researchers sought to examine the association between long-term neurological outcomes and serum sodium levels in patients who survived OHCA.
To accomplish this, they conducted a retrospective, observational study of data collected between December 2013 and February 2018 from a multicenter prospective cohort registry of 277 patients who survived OHCA. Analysis was conducted to assess the association of serum sodium levels at the ROSC and at 24 hours following ROSC with neurological outcomes after 1 year in this patient population.
Of the patients analyzed, 84 (mean aged 54 years, interquartile range [IQR], 47-62; 28.6% female; pre-existing: hypertension 41.7%, diabetes mellitus 16.7%, hyperlipidemia 9.5%) experienced good outcomes and 193 (mean aged 64 years, IQR, 49-75; 30.6% female; pre-existing: hypertension 44.6%, diabetes mellitus 34.2% , hyperlipidemia 8.8%) experienced poor outcomes.
The good outcome group had 24-hour ROSC sodium levels of median 137.4mEq/L (IQR, 135-139) and the poor outcome group had 24-hour ROSC sodium levels of median 140mEq/L (IQR, 136-144), interpreted by researchers as being significantly higher in the poor outcome group (P<.001). They asserted that the risk of poor 1-year cerebral performance categories was increased by 13% (adjusted odds ratio, 1.13; 95% CI, 1.04-1.23; P = .004) with increased serum sodium levels per 1 mEq/L.
Study limitations included the retrospective nature of the study, selection bias, brain edema was never identified, the effect of crystalloid sodium levels on neurological outcomes, and swelling of the brain was never directly examined.
Researchers concluded that “Relatively high serum sodium levels at 24 hours post-ROSC were associated with poor long-term neurological outcomes in OHCA survivors.”
Cho EJ, Lee MS, Kwon WY, et al. Hypernatremia is associated with poor long-term neurological outcomes in out-of-hospital cardiac arrest survivors. Am J Emerg Med. Published online June 20, 2022. doi:10.1016/j.ajem.2022.06.014