Predictive ability of shock index in survival of ICU admitted emergency surgery patients: A retrospective cohort study

BACKGROUND: Shock index (SI) is defined as the ratio of heart rate to systolic blood pressure and is a feasible and reliable tool to assess patients’ circulatory status in emergency conditions. Its efficiency was shown in hemorrhagic shock, sepsis, trauma, and emergency triages. This study was planned to evaluate predictive ability of SI on 28-day survival of intensive care unit (ICU) admitted emergency surgery (eSurg) patients. METHODS: The study was conducted in a 20-bed capacity ICU of a University Hospital. Medical records of patients who were admitted to ICU after an eSurg between January 1, 2017, and December 31, 2019, were retrospectively scanned. Patients with age <18 and >90, elective surgeries, no written consents, missing data, and lost to follow-up were excluded from the study. Patients age, gender, surgery type, associated medical comorbidity, ICU mechanic ventilatory (MV) length, length of stay (LOS), and 28-day survival status were recorded. Selected pre-operative (pre-op) and post-operative (post-op) laboratory parameters (hemoglobin [Hb], platelet count, international normalized ratio [INR], and pH) were collected, sequential organ failure assessment and SI scores were calculated. Data were statistically processed with 95% confidence interval and p<0.05 significance in relation to survival. RESULTS: Patient survival rate was 95%. Abdominal and gastrointestinal surgeries constituted 47% of the cases. The most frequent comorbidities were cardiovascular and pulmonary diseases. In statistical analyses, neither surgery type nor associated medical condition was related to patient outcome. The mean LOS was 2.3 days. The mean MV length was about 23 h and significantly shorter in survived patients (p<0.001, t=−7.5). The higher post-op Hb levels were related to the higher survival (p=0.020, t=2.4). Post-op higher INR levels were found as a negative prognostic factor for survival (p=0.025, t=−2.3). Both pre-op and post-op pH levels were significantly related to patient survival (p=0.001, t=1.9 and p<0.001, t=7.1). The lower post-op SI scores were predictive to the shorter MV lengths (p=0.010, t=1.9). A significant relation was presented between lower pre-op and especially post-op SI scores and patients’ survival (p=0.001, t=−1.6 and p=0.001, t=−2.9). CONCLUSION: This study presented that SI scores successfully predicted patients’ survival in ICU admitted eSurg patients. We believe that the SI forgotten in the dusty shelves of the literature does not get the importance it deserves. SI is a simplistic, reliable, and highly cost-effective assessment tool. Larger prospective RCTs should be planned to assess feasibility and reliability of SI in different patient populations.