Risk factors for hypotension in regional spinal anesthesia for cesarean section. Role of the Waist-to-Hip Ratio and Body Mass Index

Abstract

Introduction:

Because of its incidence, hypotension under spinal anesthesia has been the subject of study and debate. Studies have been aimed at defining risk factors, clarifying pathophysiology, and creating prophylaxis and management protocols. There are no studies of anthropometric measurements, such as waist-to-hip ratio (WHR) and body mass index (BMI), associated with maternal hypotension. The higher the content of the abdominal cavity, the greater the likelihood of aorto-caval compression syndrome and the higher the risk of hypotension.

Objective:

To determine if the WHR and the BMI correlate with the probability of developing hypotension in pregnant women undergoing cesarean section under subarachnoid anesthetic block.

Materials and methods:

A prospective cohort study of 231 women undergoing cesarean section under regional anesthesia. Anthropometric measurements were made before anesthesia, and vital signs were recorded during the procedure at predetermined time points to analyze the hemodynamic status. Hypotension was defined as a systolic blood pressure below 90 mm Hg.

Results:

The incidence of hypotension was 38%; 45.8% of the women had a WHR >0.99, with an incidence of 21.7% versus 15.2%, and a nonsignificant risk ratio of 2.12 (95% confidence interval [CI] 1.52-3.54, P = 0.021). Women with a BMI >29 had an incidence of 42.8% versus 57.14%, without a significant difference (P = 0.576). There was a significant association between the weight of the newborn >3900g and the risk of hypotension (relative risk 2.12, 95% CI 1.52-3.54, P = 0.021).

Conclusion:

There was no positive correlation between WHR and BMI, and the risk of developing hypotension. The weight of the newborn must be further analyzed in future studies.