Evaluation of the use of shock index in identifying acute blood loss in healthy blood donor dogs.

Abstract

To determine if shock index (SI) would increase following blood donation and if it would be a more sensitive assessment of acute blood loss as compared with heart rate (HR), blood pressure, and plasma lactate. Prospective study. University teaching hospital. Twenty client-owned clinically normal dogs. Peripheral venous blood measurements and blood donation. Data were collected at 3 time points: prior to donation (Tpre ), immediately after donation (T0 ), and 10 minutes following completion of donation (T10 ). HR and systolic blood pressure (SBP) were recorded and used to calculate SI at time points Tpre , T0 , and T10 . Packed cell volume (PCV), total plasma protein (TPP), and plasma lactate were evaluated from a peripheral venous blood sample at Tpre and T10. The mean SI was significantly increased at both time points following blood donation as compared to baseline (SIpre = 0.88±0.19 vs SI0 = 1.17±0.21 vs SI10 = 1.12±0.25 (P = 0.0002 and 0.0003, respectively). Following blood donation, the mean SBP was significantly lower (SBPpre = 149±24 mm Hg, SBP0 = 118±20 mm Hg; P = 0.0001, SBP10 = 133±21 mm Hg; P = 0.011). The mean HR was not significantly different at T0 but was significantly increased at T10 (HRpre = 128±21/min, HR0 = 136±25/min, P = 0.193; HR10 = 146±29/min, P = 0.003). There was no significant difference in mean PCV (PCVpre = 50±4%, PCV10 = 48±4%, P = 0.08). The mean TPP and plasma lactate were significantly different following donation but still within the reference interval (TPPpre = 6.8±0.4 g/dL, TPP10 = 6.4±0.4 g/dL, P = 0.0014; Lacpre = 1.7±0.7mmol/L, Lac10 = 1.9±0.8 mmol/L, P = 0.04). A receiver operating characteristic (ROC) analysis comparing area under the curve (AUC) for SI, HR, and SBP at T0 and T10 compared to Tpre found that SI (AUC at T0 : 0.858, CI: 0.730, 0.984 AUC at T10 : 0.769 CI: 0.617, 0.921) was a better indicator of blood loss than SBP at both T0 (AUC 0.165, CI: 0.0384, 0.292, P<0.0001) and T10 (AUC 0.288, CI: 0.124, 0.451, P<0.001) and better than HR at T0 (AUC 0.574, CI: 0.392, 0.756, P<0.001). An SI cut-off of 1.064 was 80% specific and 85% sensitive at T0 for detecting blood loss. An SI>1.0 is a sensitive and specific tool for detecting acute small volume blood loss in healthy dogs.