Evaluation of shock index on admission as a predictor of mortality in secondary peritonitis

SI is an indicator of hemodynamic instability. It can be used to know the extent of circulatory collapse or non-hypovolemic shock and resuscitate accordingly, in all kinds of patients, despite the etiology. It is a good risk stratification method to guide resuscitative measures and predict early mortality. SI is a useful tool that can alert one to abnormalities even when the patient is vitally stable due to compensation by body.11,12 When compared to blood pressure and heart rate alone, it is a more accurate predictor of outcome in patients with illnesses such pulmonary embolism who are not in shock.13

Patients with acute circulatory failure have been found to have considerably worse outcomes when their SI is above 1.0.14

Compared to pulse or blood pressure alone, a SI ≥ 0.9 indicated urgency in triaging, higher hospital admission rates, and extensive therapy upon admission. This study suggested that SI might be an effective method for identifying and assessing critical illness in the emergency early on.11

In order to determine how well the SI can predict the primary outcome of 28-day mortality and the secondary outcome of hyperlactatemia, which acts as a proxy for the severity of the condition, an observational cohort study was conducted by Berger T et al. If a patient’s SI was 0.7 or greater, three times as many participants as those with a normal SI, were predicted to present with hyperlactatemia. The best predictor of both outcomes was SI ≥ 1.0.15

A retrospective observational study of 50 patients in 2010 showed that SI at 1 hour has low specificity (45.8%) as a predictor of mortality in ED patients with septic shock, but it has a high sensitivity (73.1%). SI at 2 hours has a sensitivity of 80.8% and a specificity of 79.2% for death at a cut-off point of > 1.0. This demonstrates that SI at 2 hours is far more accurate than SI at 1 hour as an early predictor of death in patients with septic shock.16

A one-year cross-sectional study conducted in 2015 included patients with hypotension and septicemia. MAP, SI, and MSI were calculated and requirement of vasopressors was assessed. The greatest sensitivity and specificity were found to be associated with a cut-off SI value of 0.87 or above for predicting how adequately the patient would respond to initial fluid resuscitation given. 17

Liu YC et al showed that a critically ill patient’s DBP would drop sooner than their SBP, so MAP is a more reliable indicator of the severity of their illness.18 Studies have shown linear inverse relationship between”parameters such as cardiac index, stroke volume, left ventricular stroke work, MAP and SI.14 MSI is inversely related to Stroke volume and systemic vascular resistance which means a low MSI is suggestive of a hyperdynamic circulation whereas a high MSI is suggestive of a hypodynamic”circulation.14

A retrospective study from 2009 showed that MSI greater that 1.3 is indicative of higher chances of ICU stay and mortality. MSI >1.3 and <0.7 was a stronger predictor of mortality than SI.18

According”to a retrospective cohort from January 2016 to December 2017, SI ≥1.0 and MSI ≥1.3 were both specific for sepsis prediction In terms of accuracy MSI was better than SI. MSI≥ 1.0 was the most sensitive predictor of mortality (positive predictive value-97.8% and specificity-76.2%) whereas MSI of ≥1.3 was better at predicting sepsis, ICU stay, hyperlactemia and one month mortality. MSI>1.0 was associated with five times higher risk of ICU admissions and death. Sepsis and hyperlactatemia were linked to a SI of ≥1.0, but not ICU admission or death.“When it came to predicting sepsis, a SI of ≥ 0.7 was less sensitive than an MSI of ≥ 1.0 and was not a reliable indicator”of other”outcomes.19

As laboratory tests, various scoring systems and radiological investigations are cumbersome. MSI and SI are very easy to comprehend and non-invasive in nature, which makes them an attractive candidate for early detection of conditions associated with hemodynamic instability even at PHC level. It’s potential use as a prognostic marker in secondary peritonitis may offer a new avenue for early intervention but due to lack of studies it requires further investigation. This research study aims to conduct a comprehensive analysis of existing literature and compare MSI and SI as a predictor of mortality and morbidity, establish a relationship between them, evaluate them as an individual predictor and assess which one is a superior predictor of mortality.