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

To determine the normal range of shock index (SI), blood pressure (BP), mean arterial pressure (MAP) and heart rate (HR) among postpartum women in a low-resource setting.

In a prospective cohort study, vital signs were recorded 1 hour after delivery among postpartum women with normal blood loss who delivered in Abakaliki, Nigeria, from April to July 2019.

Among 225 women, the median (95% reference range) was 120 (100-155.8), 70 (60-94), and 90 (66.5-116.6) mm Hg for systolic BP, diastolic BP, and MAP, respectively; 82 (65-102) bpm for HR; and 0.69 (0.48-0.89) for SI. The upper SI limit of 0.89 supported the current value of 0.9 as the upper limit; however, the lower SI limit of 0.48 corresponded to the current lower limit for a non-obstetric population (0.5). The SI of more than half of the study women (n=126; 56.0%) was within the normal range for non-obstetric women (0.5-0.7).

Although hemodynamic changes in pregnancy widen the SI range, 56.0% of women maintained SI within the non-obstetric reference range. In low-resource settings, the current normal obstetric SI range of 0.7-0.9 should be revised to 0.5-0.9 to accommodate this lower threshold.