Peripheral perfusion index as a predictor of severe shock in trauma patients: a prospective observational study.

BACKGROUND: Early recognition of haemorrhagic shock is critical in trauma care, particularly in low- and middle-income countries where delayed referral is common. Conventional vital signs may remain normal despite ongoing hypoperfusion. The Perfusion Index (PI), derived from pulse oximetry, is a non-invasive and continuously available marker of peripheral perfusion. This study evaluated the ability of PI to identify severe haemorrhagic shock in trauma patients and compared its performance with the Shock Index (SI) and Modified Shock Index (mSI). METHODS: This prospective, single-centre study was conducted at a Level 1 trauma centre between January and May 2024. Adult Priority 1 trauma patients were enrolled and classified as having no/mild shock (ATLS grades 1-2) or severe shock (grades 3-4). PI was recorded during initial assessment. SI, mSI, lactate, injury severity, transfusion requirement, ICU admission, and 24-hour mortality were analysed. Receiver operating characteristic (ROC) analysis and multivariable logistic regression were performed. RESULTS: A total of 120 patients were included (mean age 40.4 ± 17.2 years; 90% male), predominantly with blunt trauma (85% road traffic injuries). Severe shock was present in 35 patients (29.2%). Median PI was significantly lower in severe shock compared with no/mild shock (0.54 [IQR 0.28-1.31] vs. 1.33 [0.71-2.16], p = 0.008). Mean SI (1.24 ± 0.47 vs. 0.72 ± 0.14, p < 0.001) and mSI (1.50 ± 0.49 vs. 0.96 ± 0.18, p = 0.001) were significantly higher in severe shock. On multivariable analysis, PI ≤ 0.78 independently predicted severe shock (OR 3.62, 95% CI 1.41-9.29), along with SI > 1.0, mSI > 1.3, and lactate > 4 mmol/L. PI demonstrated fair discrimination for severe shock (AUC 0.76; sensitivity 72%, specificity 66%) and 24-hour mortality (AUC 0.71). CONCLUSION: PI demonstrated moderate discriminatory ability and may serve as a useful non-invasive adjunct for identifying severe haemorrhagic shock. Its continuous, operator-independent measurement supports a potential role in early triage and resuscitation, particularly in resource-limited settings.