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  • Open Access

Shock index: blunt clinical predictions

Critical Care201317:468

https://doi.org/10.1186/cc13125

  • Published:

Keywords

  • Emergency Department
  • Trauma Patient
  • Injury Severity Score
  • Hemorrhagic Shock
  • Abbreviate Injury Scale

We appreciate the work of Mutschler and colleagues regarding shock index (SI) in trauma patients [1]; however, we would like to discuss a few points of interest. The SI obtained at the scene differed from the SI obtained in the emergency department (ED). Patients with SI category III had a SI at the scene of 0.7 to 1.5. This indicates that SI can vary with time and vary with changes in medical condition. Patients classified as ‘no shock’ still had a 10.9% mortality rate, a 12.5% risk of multi-organ failure, and a 6.3% risk of sepsis. We do not know when the onset of sepsis occurred in these trauma patients. Thus, a single SI taken within ‘the first hours’ of ED admission might not accurately reflect a patient’s condition, especially if the initial SI is category I or II.

Other studies have shown that SI may also lead to an undertriage of those patients most likely to develop early and progressive hemorrhagic shock [2]. In addition, prehospital SI alone was found to have diminished accuracy for patients aged over 60 years [3]. SI may be of limited value in the assessment of systemic oxygen transport [4], which is a more direct measurement of end-organ perfusion and tissue viability than the SI. Finally, the results of this study can best be applied to male patients with blunt trauma injuries who develop hypovolemic shock, but not to every trauma patient on presentation to ED with high risk of other types of shock.

Authors’ response

Li and colleagues note that SI may vary with time and changing medical condition; therefore, a single SI may not accurately reflect a patient’s condition. We fully agree that a single SI represents only a ‘snapshot’ depending partly on actual treatment. However, previous independent reports have demonstrated that SI correlated best with the transfusion of ≥4 blood units within the first 48 hours after hospital admission [5, 6] and that patients with a SI between 0.7 and 0.9 had a two-fold increased risk for massive transfusion [7]. Li and colleagues further criticize that SI may lead to an undertriage of patients and cite a corresponding study [2]. In this study, however, the low sensitivity of the SI was observed only in healthy individuals with low tolerance to artificial progressive lower-body negative-pressure. The mortality and multi-organ failure/sepsis rates in our ‘no shock’ group may be attributable to initial trauma load (Injury Severity Score group I 19.3 (±12.0)), including relevant (Abbreviated Injury Scale ≥3) brain (45.9%) and thoracic injuries (36.1%). Lastly, Li and colleagues criticize that SI may not be accurate in the elderly. The cited study, however, suggests that the number of blood products transfused in patients aged between 16 and 80 years correlates significantly with the SI [3]. The authors acknowledge that SI is inferior to direct perfusion measurements and should not be used inconsiderately in clinical routine. However, SI may serve as a fast and easy alternative to assess the extent of hypovolemia in trauma patients when advanced technology is unavailable.

Abbreviations

ED: 

Emergency Department

SI: 

Shock index.

Declarations

Authors’ Affiliations

(1)
Internal Medicine Division, Department of Medicine, Rutgers Robert Wood Johnson Medical School, 1 Robert Wood Johnson Place, 08903-0019, PO Box 19, New Brunswick, NJ, USA
(2)
Pulmonary and Critical Care Division, Department of Medicine, Rutgers Robert Wood Johnson Medical School, 1 Robert Wood Johnson Place, 08903-0019, PO Box 19, New Brunswick, NJ, USA
(3)
Divisions of Nephrology and Pulmonary/Critical Care, Department of Medicine, Rutgers Robert Wood Johnson Medical School, 1 Robert Wood Johnson Place, 08903-0019, PO Box 19, New Brunswick, NJ, USA

References

  1. Mutschler M, Nienaber U, Münzberg M, Wölfl C, Schoechl H, Paffrath T, Bouillon B, Maegele M: The shock index revisited - a fast guide to transfusion requirement? A retrospective analysis on 21,853 patients derived from the TraumaRegister DGU(R). Crit Care 2013, 17: R172. 10.1186/cc12851PubMed CentralView ArticlePubMedGoogle Scholar
  2. Schafer K, Van Sickle C, Hinojosa-Laborde C, Convertino VA: Physiologic mechanisms underlying the failure of the “shock index” as a tool for accurate assessment of patient status during progressive simulated hemorrhage. J Trauma Acute Care Surg 2013, 75: S197-S202.View ArticlePubMedGoogle Scholar
  3. McNab A, Burns B, Bhullar I, Chesire D, Kerwin A: An analysis of shock index as a correlate for outcomes in trauma by age group. Surgery 2013, 154: 384-387. 10.1016/j.surg.2013.05.007View ArticlePubMedGoogle Scholar
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  5. Zarzaur BL, Croce MA, Fischer PE, Magnotti LJ, Fabian TC: New vitals after injury: shock index for the young and age x shock index for the old. J Surg Res 2008, 147: 229-236. 10.1016/j.jss.2008.03.025View ArticlePubMedGoogle Scholar
  6. Zarzaur BL, Croce MA, Magnotti LJ, Fabian TC: Identifying life-threatening shock in the older injured patient: an analysis of the National Trauma Data Bank. J Trauma 2010, 68: 1134-1138. 10.1097/TA.0b013e3181d87488View ArticlePubMedGoogle Scholar
  7. Vandromme MJ, Griffin RL, Kerby JD, McGwin G, Rue LW, Weinberg JA: Identifying risk for massive transfusion in the relatively normotensive patient: utility of the prehospital shock index. J Trauma 2011, 70: 384-388. 10.1097/TA.0b013e3182095a0aView ArticlePubMedGoogle Scholar

Copyright

© BioMed Central Ltd. 2013

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