(938) Vital signs associated with Class I-IV blood loss within 24 hours of birth

Friday, February 10, 2023

3:30 PM – 5:00 PM

Objective: The American College of Surgeons Advanced Trauma Life Support (ATLS) training program classifies blood loss in shock classes from I to IV, defined as loss of < 15%, 15-< 30%, 30-< 40%, and 40% of total blood volume. Per ATLS guidelines, shock class is associated with substantial differences in vital signs (Class I vs. IV, heart rate < 100 vs. >140; respiratory rate 14-20 vs. > 35). The degree of vital sign abnormality observed in obstetric patients with blood loss class is not well characterized. We sought to quantify vital signs changes associated with shock class in obstetric patients.

Study Design: We analyzed data from birth hospitalizations at a southeastern quaternary care hospital between January 2018 and June 2021. Cumulative blood loss, determined with the Triton system after August 2019, maternal weight at delivery, height, and vital signs in the 4 hours after birth were extracted from the Electronic Health Record. We estimated total blood volume based on maternal weight and body mass index (BMI) [TBV = weight in kg * (130 - 1.372 * BMI)]. We used linear regression to quantify associations between ATLS shock class and systolic blood pressure (SBP), heart rate (HR), shock index (HR/SBP), pulse pressure (PP), and respiratory rate (RR) in the first 4 hours after birth.

Results: Maternal weight, height, blood loss, and vital sign data were available for 8,948 pregnancies, among whom 1,095 (12.2%) lost >15% of their blood volume. A total of 318,151 vital sign values were obtained for these patients during the 4 hours after birth. As expected, greater blood loss was associated with lower SBP, higher HR, higher shock index, lower PP and higher RR (p< .0001 for all indicators); however, absolute differences were small, and there was substantial overlap between shock class categories (Figure). For nadir SBP, the median for ≥40% blood loss was 5 mmHg lower than for < 15% blood loss.

Conclusion:

We found small differences in postpartum vital signs between birthing people with blood loss ranging from < 15% to ≥ 40% blood loss. Stable vital signs do not exclude life-threatening postpartum hemorrhage.

Primary Author(s)

Alison M. Stuebe, MD, MSc (she/her/hers)
Professor of Obstetrics and Gynecology
University of North Carolina
Chapel Hill, North Carolina, United States

Presenting Author(s)

Alison M. Stuebe, MD, MSc (she/her/hers)
Professor of Obstetrics and Gynecology
University of North Carolina
Chapel Hill, North Carolina, United States

Coauthor(s)

Katharine Bruce, MPH (she/her/hers)
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina, United States
CB
Clara Busse
Gillings School of Global Public Health
Chapel Hill, North Carolina, United States
Johanna Quist-Nelson, MD
Attending Physician
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina, United States
CM
Christine McKenzie, MD
University of North Carolina
Chapel Hill, North Carolina, United States
EP
Emily Patterson, PhD
The Ohio State University
Columbus, Ohio, United States
KT
Kristin P. Tully, PhD
Research Assistant Professor
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina, United States