Use of the "obstetric shock index" as an adjunct in identifying significant blood loss in patients with massive postpartum hemorrhage

Objective: To establish the normal range for the "obstetric shock index" (OSI) after birth and to determine its usefulness as an aid to estimate blood loss in postpartum hemorrhage (PPH). Methods: A retrospective case-control analysis was conducted involving pregnant women admitted to St Georges Hospital for delivery: 50 with no PPH (control group) and 50 with massive PPH (> 30% loss of blood volume; case group). The OSI was calculated at 10 and 30 minutes from PPH onset. Results: Mean OSI in the control group at 10 and 30 minutes was 0.74 (range, 0.4-1.1) and 0.76 (range, 0.5-1.1), respectively. In the case group, mean OSI at 10 and 30 minutes was 0.91 (range, 0.4-1.5) and 0.90 (range, 0.5-1.4), respectively, with 64% requiring blood products. In the case group, 89% of women with an OSI of 1.1 or more at 10 minutes required transfusion; 75% with an OSI of 1.1 or more at 30 minutes required transfusion. Conclusion: We recommend that the normal OSI range should be 0.7-0.9. An OSI of more than 1 seems to be a useful adjunct in estimating blood loss in cases of massive PPH and in predicting the need for blood and blood products.