Utility of triage shock index in predicting patient outcome in calcium channel blocker poisoning

Introduction: Shock index is defined as heart rate divided by systolic blood pressure. It is reported as a predictor of morbidity and mortality in trauma and acute myocardial infarction in previous studies. It may be valuable in evaluation of calcium channel blocker poisoning. The objective of this study is to examine the probability of serious outcome based on first measured shock index in patients who presented to emergency department with calcium channel blocker poisoning. Methods: A retrospective chart review was conducted on calcium channel blocker poisoning cases in Hong Kong Poison Information Centre from 1 July 2008 to 30 June 2017. Shock index was calculated with blood pressure and pulse measurement at emergency department triage. Odds ratios of various variables for major outcome, mortality, intensive care unit admission, length of stay in acute hospital were calculated by multivariate analysis or negative binomial regression where appropriate. The performance of shock index in predicting major outcome was evaluated with receiver operating characteristic curve. Results: A total of 390 cases were identified, of whom 25.1% developed major outcome and 5.6% died. Shock index showed significant association with major outcome (odds ratio: 17.017, 95% confidence interval: 5.521–52.455). The area under the receiver operating characteristic curve for shock index in predicting major outcome was 0.7008 (95% confidence interval: 0.64–0.76). Conclusion: Higher shock index is associated with worse patient outcome in calcium channel blocker poisoning. However, shock index alone is not reliable in predicting patient outcome. Further research is needed before shock index can be incorporated for use in patient management in poisoning with calcium channel blocker or other anti-hypertensives.