What is the normal range of obstetric shock index in the immediate postpartum period in a low resource setting?

Abstract

Objective: To determine the normal range of shock index (SI), blood pressure (BP), mean arterial pressure (MAP) and heart rate (HR) among postpartum women and to compare shock index with the normal range in the current literature.Methods: This is a prospective cohort study evaluating vital signs collected at one hour of delivery in women with normal blood loss delivered in Abakaliki, Nigeria. Results: The median (95% reference range) was 120 (100 - 155.8) for systolic BP, 70 (60 - 94) for diastolic BP, 90 (66.5 - 116.6) for MAP, 82 (65 - 102) for HR, and 0.69 (0.48 - 0.89) for SI. The upper limit of SI of 0.89 in this study did support the current literature suggesting a threshold of 0.9 as upper limit of normal. However, the lower limit of SI of 0.48 in this study corresponds to the lower limit of 0.5 for non-obstetric population. Over half (56%) of the study cohorts maintained shock index values within the normal range (0.5 - 0.7) for non-obstetric population. Conclusion: Although haemodynamic changes of pregnancy widens the range of shock index in obstetric population, 56% of the participants maintained normal shock index within the reference range for non-obstetric population. We recommend that the normal obstetric shock index range of 0.7 - 0.9 in current literature be changed to 0.5 - 0.9 to accommodate this lower threshold.