Relationship between Nonhepatic Serum Ammonia Levels and Sepsis-Associated Encephalopathy: A Retrospective Cohort Study

Abstract

Objectives. Nonhepatic hyperammonemia often occurs in patients with sepsis. Ammonia plays an essential role in the occurrence of hepatic encephalopathy. However, the relationship between nonhepatic serum ammonia levels and sepsis-associated encephalopathy (SAE) remains unclear. Thus, we aimed to evaluate the association between serum ammonia levels and patients with SAE. Methods. Data of critically ill adults with sepsis who were admitted to the intensive care unit were retrieved from the Medical Information Mart for Intensive Care IV (MIMIC IV) between 2008 and 2019 and retrospectively analyzed. Data of patients with sepsis patients and serum ammonia not related to acute or chronic liver disease were not included. Results. Data from 720 patients with sepsis were included. SAE was found to have a high incidence (64.6%). After adjusting for other risk factors, a serum ammonia level of ≥45 μmol/L (odds ratio (OR): 3.508, 95% confidence interval (CI): 2.336–5.269, $p<0.001$ ) was found to be an independent risk factor for patients with SAE; moreover, as the serum ammonia level increased, the hospital mortality of SAE gradually increased in a certain range (serum ammonia <150 μmol/L). Serum ammonia levels of ≥45 μmol/L were associated with higher Simplified Acute Physiology Score II and Sequential Organ Failure Assessment (SOFA) scores in patients with SAE. Besides, our study found that patients with SAE used opioid analgesics (OR:3.433, 95% CI: 1.360–8.669, $p=0.009$ ) and the SOFA scores of patients with SAE (OR: 1.126, 95% CI: 1.062–1.194, $p<0.001$ ) were significantly higher than those without SAE. Conclusions. Nonhepatic serum ammonia levels of ≥45 μmol/L evidently increased the incidence of SAE. Serum ammonia levels should be closely monitored in patients with sepsis.