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    Shock Index

    May be a more sensitive indicator of occult shock, especially in trauma or acute hemorrhage.
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    When to Use
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    Why Use

    Consider in the following scenarios:

    • Patients presenting with hemorrhage and trauma, to identify patients at increased risk for transfusion.

    • Patients requiring endotracheal intubation, to help identify groups of patients at risk of post-intubation hypotension.

    • Patients with suspected sepsis (found to be as sensitive as the SIRS criteria to identify patients at risk for sepsis, Berger 2013); however, note that a large RCT showed that use of the Shock Index to guide fluid resuscitation in sepsis did not demonstrate a mortality improvement (ProCESS Investigators 2014).

    • There are currently no large scale prospective studies validating the use of the Shock Index to guide resuscitative intervention.

    • Shown to correlate with higher risk of mortality (likelihood ratio 5.67) and hospitalization (LR 6.64) at a cutoff of >1.3 (Al Jalbout 2019).

    • A pediatric age-adjusted Shock Index (SIPA) better differentiates severely injured children (up to 16 years of age) (Acker 2015).

    • Blood pressure and heart rate, when used individually, fail to accurately predict the severity of hypovolemia and shock in major trauma.

    • Massive transfusion of blood products can be associated with significant risk if initiated on the wrong patient. Identifying patients at risk for massive transfusion can be difficult, and objective measures like the Shock Index can help.

    • Shown to be more sensitive than the ABC Score for Massive Transfusion (Schroll 2018).
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    Accuracy of Shock Index in identifying trauma patients in need of massive blood transfusion has not yet been prospectively investigated.

    Formula

    Shock Index = HR/SBP

    Evidence Appraisal

    The shock index (SI, calculated as heart rate divided by systolic blood pressure) was first proposed in the literature as a measure of shock severity by Allgöwer and Burri in 1967. More recently, the shock index has been further studied with modern protocols.

    In large retrospective study by Mutschler et al (2013), 21,853 patients were identified in a trauma registry, and SI was calculated based on emergency department arrival vital signs. The degree of shock was found to correlate with increasing SI value. The need for blood products, fluids and vasopressors was also found to increase with higher SI values.

    A retrospective study by Cannon et al (2009), performed at a single level I trauma center, identified 2,445 patients admitted over a five year period. Patients with SI >0.9 were found to have a significantly higher mortality (15.9%) when compared with patients with normal SI (6.3%)

    In a retrospective registry study by Vandromme et al (2011), the authors identified 8,111 blunt trauma patients admitted at a single level I trauma center over an eight-year period. The shock index was calculated from recorded prehospital vital signs, and patients with SI >0.9 were found to have a 1.6-fold higher risk for massive transfusion.

    In a retrospective study of 542 patients who underwent emergency intubation, Heffner et al (2013) identified a pre-intubation SI ≥0.9 to be independently associated with peri-intubation cardiac arrest.

    A retrospective study of 2,524 patients that were screened for severe sepsis at a single center found that SI ≥0.7 performed as well as SIRS in NPV and was the most sensitive screening test for hyperlactatemia and 28-day mortality (Berger 2013).

    Of note, in the ProCESS trial (2014), a large multicenter prospective randomized control study that enrolled 1,341 patients, the investigators compared different protocols of resuscitation of septic patients, and one of these protocols included SI ≥0.8 as a fluid resuscitation goal. There was no significant difference in mortality between the three intervention groups.

    Literature

    Other References

    Research PaperHeffner AC, Swords DS, Neale MN, Jones AE. Incidence and factors associated with cardiac arrest complicating emergency airway management. Resuscitation. 2013;84(11):1500–1504.Research PaperBerger T, Green J, Horeczko T, et al. Shock Index and Early Recognition of Sepsis in the Emergency Department: Pilot Study. WestJEM. 2013;14(2):168–174.Research PaperProCESS Investigators, Yealy DM, Kellum JA, et al. A randomized trial of protocol-based care for early septic shock. N Engl J Med. 2014;370(18):1683–1693.Research PaperAcker SN, Ross JT, Partrick DA, Tong S, Bensard DD. Pediatric specific shock index accurately identifies severely injured children. J Pediatr Surg. 2015;50(2):331-4.Research PaperSchroll R, Swift D, Tatum D, et al. Accuracy of shock index versus ABC score to predict need for massive transfusion in trauma patients. Injury. 2018;49(1):15-19.Research PaperAl Jalbout N, Balhara KS, Hamade B, Hsieh YH, Kelen GD, Bayram JD. Shock index as a predictor of hospital admission and inpatient mortality in a US national database of emergency departments. Emerg Med J. 2019;36(5):293-297.
    Dr. Manuel Mutschler

    About the Creator

    Manuel Mutschler, MD, is a practicing physician in the Department of Trauma and Orthopedic Surgery at the Cologne-Merheim Medical Center, affiliated with University of Witten/Herdecke. He is an active researcher with interests including hypovolaemic and hemorrhagic shock.

    To view Dr. Manuel Mutschler's publications, visit PubMed

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    About the Creator
    Dr. Manuel Mutschler
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