The Shock Index revisited – a fast guide to transfusion requirement? A retrospective analysis on 21,853 patients derived from the TraumaRegister DGU®

Abstract

IntroductionIsolated vital signs (for example, heart rate or systolic blood pressure) have been shown unreliable in the assessment of hypovolemic shock. In contrast, the Shock Index (SI), defined by the ratio of heart rate to systolic blood pressure, has been advocated to better risk-stratify patients for increased transfusion requirements and early mortality. Recently, our group has developed a novel and clinical reliable classification of hypovolemic shock based upon four classes of worsening base deficit (BD). The objective of this study was to correlate this classification to corresponding strata of SI for the rapid assessment of trauma patients in the absence of laboratory parameters.MethodsBetween 2002 and 2011, data for 21,853 adult trauma patients were retrieved from the TraumaRegister DGU® database and divided into four strata of worsening SI at emergency department arrival (group I, SI <0.6; group II, SI ≥0.6 to <1.0; group III, SI ≥1.0 to <1.4; and group IV, SI ≥1.4) and were assessed for demographics, injury characteristics, transfusion requirements, fluid resuscitation and outcomes. The four strata of worsening SI were compared with our recently suggested BD-based classification of hypovolemic shock.ResultsWorsening of SI was associated with increasing injury severity scores from 19.3 (± 12) in group I to 37.3 (± 16.8) in group IV, while mortality increased from 10.9% to 39.8%. Increments in SI paralleled increasing fluid resuscitation, vasopressor use and decreasing hemoglobin, platelet counts and Quick’s values. The number of blood units transfused increased from 1.0 (± 4.8) in group I to 21.4 (± 26.2) in group IV patients. Of patients, 31% in group III and 57% in group IV required ≥10 blood units until ICU admission. The four strata of SI discriminated transfusion requirements and massive transfusion rates equally with our recently introduced BD-based classification of hypovolemic shock.ConclusionSI upon emergency department arrival may be considered a clinical indicator of hypovolemic shock in respect to transfusion requirements, hemostatic resuscitation and mortality. The four SI groups have been shown to equal our recently suggested BD-based classification. In daily clinical practice, SI may be used to assess the presence of hypovolemic shock if point-of-care testing technology is not available.

Erratum to: Shock in the emergency department; a 12 year population based cohort study

“…Moreover, respiratory frequencies and Glasgow Coma Scale were not consistently registered, whereby organ failures related to the respiratory system, and failure of the central nervous system were not included. We used a Shock Index ≥1 to define cardiovascular failure, as this index has been shown to prognosticate outcome across several etiologies of shock and critical illnesses [18,[30][31][32][33][34][35][36][37]. Ideally, cardiac output measurements would have been desirable but not feasible based on the present design.…”

Trauma Resuscitation and Monitoring

“…In 21,853 trauma patients, individuals with an admission SI less than 0.6 had a normal lactate (2.7 AE 1.7 mmol/L) in contrast to patients with severe shock (SI !1.4), who had a lactate of 6.0 AE 8.4. 53 Of note, in this study, the SBP decreased with increasing SI, but on average the SBP was never less than 90 mm Hg, even with an SI greater than or equal to 1.4, demonstrating the benefit of the SI over the SBP as an indication of hypoperfusion.…”

“…For example, if a patient has an HR of 120 and an SBP of 100 mm Hg, the SI is 1.2 beats per mm Hg. More specific SI ranges, 53,54 which are consistent with increasing base deficit (sp) and lactate, are as follows: SI <0.6 (no shock) SI !0.6 to <1.0 (mild shock) SI !1.0 to <1.4 (moderate shock) SI !1.4 (severe shock)…”

Can venous base excess replace arterial base excess as a marker of early shock and a predictor of survival in trauma?

“…It has been shown to be useful in identifying early shock and correlates with mortality. (18)(19)(20) Patients were divided into groups with SIs of ≤ 0.7 ('nonshock' group), > 0.7 to 1 ('early shock' group) and > 1 ('shock' group) based on previous study data. (18,19,21) The ISS was developed by Baker et al in 1974 as a scalar measure of all anatomical injuries sustained during trauma.…”