Shock index and heart rate standard reference values in the immediate postpartum period: A cohort study

To determine Shock Index (SI) reference values in the first two hours of the postpartum period after objectively measuring postpartum bleeding.

A complementary analysis using data from a prospective cohort study at Women's Hospital of the University of Campinas, Brazil, between 1 February 2015 and 31 March 2016. It included women giving birth vaginally unless they had one of these conditions: gestational age below 34 weeks, hypertension, hypo- or hyperthyroidism without treatment, any cardiac disease, infections with fever or sepsis, history of coagulopathy or delivery by C-section. Blood loss was measured by adding the blood volume collected in the drape placed under the women's buttocks and the weight of gauzes and compresses used (excluding the dry weight). Vital signs were measured every 5-15 min after delivery. Exploratory data analysis was performed to assess the mean, standard deviation, median, and percentiles (5th, 10th, 25th, 50th, 75th, 90th, 95th). To identify variation among the periods after delivery, the mean SI and heart rate (HR) values observed for the following intervals were used in the analysis: 0-20 min, 21-40 min, 41-60 min, 61-90 min and 91-120 min.

One hundred eighty-six women were included. The mean age ± SD was 24.9 ± 6.1 years and the mean gestational age at birth was 39.2 ± 1.8 weeks. At the puerperal period, the mean SI values ranged from 0.68 ± 0.14 to 0.74 ± 0.15. The percentile distribution ranged from 0.46 (5th percentile) to 1.05 (95th percentile). The mean HR values ranged from 80.8 ± 12.7 bpm to 92.3 ± 14.4 bpm. The percentile distribution ranged from 62.0 bpm (5th percentile) to 117 bpm (95th percentile).

Reference ranges were established for SI and HR values which showed small variations throughout the postpartum period.