Date of Award

7-9-2009

Document Type

Thesis

Degree Name

Medical Doctor (MD)

First Advisor

Charles Wira

Abstract

INTRODUCTION. Sepsis is considered to be a leading cause of non-coronary death in hospitals across the United States. Early identification and risk stratification is difficult because there is limited research characterizing patients at risk for disease progression who will require an escalation of care. Furthermore, patients often present with stable vital signs, masking the severity of illness at presentation. The aim of our study is to evaluate whether an elevated Shock Index (SI) >0.8 (heart rate / systolic blood pressure) is a predictor of short-term vasopressor dependence in Emergency Department (ED) patients with severe sepsis. METHODS: Retrospective study using patients from the Yale New Haven Hospital sepsis registry who presented to the YNHH Emergency Department between July 1, 2005 and July 30, 2007. ED patients were included if they had all of the following criteria; (1) At least 2 of 4 Systemic Inflammatory Response Syndrome (SIRS) criteria, (2) a documented or presumed source of infection and (3) signs of end-organ dysfunction at presentation. Exclusion criteria were age <18 years old, presenting in extremis, being discharged home from the ED, not meeting severe sepsis criteria, or receiving comfort care at initial presentation. Patients were stratified into two groups: (1) Sustained SI elevation defined as a SI >0.8 for 80% or more of vital sign measurements and (2) Nonsustained SI group with no SI elevation or a SI elevation for less than 80% of vital sign measurements. The principle outcome measure was the administration of vasopressors within 72 hours of initial presentation. Secondary outcomes included hospital mortality rate, organ failure scores, interventional therapies, and ED disposition. RESULTS: 295 of 359 patients met inclusion criteria for the study. 18% (n = 64) were excluded. The mean age was 62.5 years (SD ± 18.54), with a difference between the sustained and non-sustained SI groups (56.5 vs. 67.9 years, respectively) [p<0.05]. 64.1% (n = 189) presented with an initial elevated SI, while 47.5% (n=140) maintained an elevated SI >80% of the time. A total of 24.4% (72 of 295) received vasopressors within 72 hours of presentation. Among patients with a sustained SI elevation, 38.6% (54 of 140) required vasopressors within 72 hours, contrasted to 11.6% (18 of 155) in the group without a sustained elevated SI [p < 0.05]. The percentage of time patients maintained an elevated SI >0.8 was associated with vasopressor use. The mean number of organ failures was (4.0 ± 2.1 vs. 3.2 ± 1.6, respectively) [p <0.05], and was associated with mortality. Overall mortality for patients with a sustained SI was 19.3% (27 of 140) compared to 12.3% (19 of 155) in the non-sustained SI group [p >0.05]. Patients with an elevated SI were more likely to be admitted to the Intensive Care Unit or Step down Unit (53 vs. 41%, respectively) [p<0.05]. CONCLUSION: ED patients with severe sepsis and a sustained SI elevation have a significantly higher rate of vasopressor use within 72 hours of initial presentation, contrasted to patients without a sustained SI elevation. Patients with an elevated SI also have a greater number of organ failures and a higher percentage of ICU admissions, both of which have been shown to correlate with higher in-hospital mortality rates. An elevated SI may be a useful modality for identifying patients with severe sepsis at risk for requiring escalation of care.

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