Reverse shock index (RSI) as a predictor of post-intubation cardiac arrest (PICA)

Endotracheal intubation (ETI) in critically ill patients is a high-risk procedure due to the increased risk of cardiac arrest, and several factors may predict poor outcomes in these patients. The aim of this study was to investigate the role of some factors, especially newly introduced vital signs such as the reverse shock index (RSI), in predicting post-intubation cardiac arrest (PICA) in critically ill adult patients.

This cross-sectional study was conducted on critically ill patients over 18 years of age who were admitted to the emergency department (ED) and underwent ETI within 1 year. Patients who developed PICA and those without this event were included in the study, and their features were compared. The primary outcome was cardiac arrest.

Of 394 patients, 127 patients were included, of whom 95 (74.8%) developed PICA, and 32 (25.2%) did not experience cardiac arrest after intubation. In multivariate analysis, age, RSI, oxygen saturation, and total bilirubin were significantly associated with PICA. In addition, patients with RSI < 1 had a significantly higher risk of developing PICA (odds ratio = 5.22, 95% CI 1.83-14.86, p = 0.002). The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for predicting PICA were 51.11%, 83.33%, 90.2%, 36.23%, and 59.17%, respectively. The ROC curve for RSI showed an area under the curve (AUC) of 0.66.

RSI may be useful in predicting PICA with higher diagnostic accuracy compared to the shock index. Furthermore, advanced age, hypoxia, and hyperbilirubinemia may increase the risk of PICA in patients admitted to the ED.