Postoperative Respiratory Compromise following Cesarean Birth: The Impact of Obesity and Systemic Opioids.

 The aim of this study was to measure the effect of obesity and systemic opioids on respiratory events within the first 24 hours following cesarean.  Opioid-naive women undergoing cesarean between January 2016 and December 2017 were included in this retrospective cohort study. The primary outcome was the proportion of women experiencing at least one composite respiratory outcome (oxygen saturation less than 95% lasting 30+ seconds or need for respiratory support) within 24 hours of cesarean. The impact of obesity and total systemic opioid dose in 24 hours (measured in morphine milligram equivalents [MMEs]) on the composite respiratory compromise outcome were evaluated.  Of 2,230 cesarean births, 790 women had at least one composite respiratory event. Predictors of the composite respiratory outcome included body mass index (BMI) as a continuous variable (odds ratio = 1.063 for every one unit increase in BMI [95% confidence interval (CI): 1.021-1.108],  = 0.003), and MME (odds ratio = 1.005 [95% CI: 1.002-1.008],  = 0.003), adjusting for magnesium sulfate use. The interaction between obesity and opioid dose demonstrated an odds ratio of 1.000 (95% CI: 0.999-1.000,  = 0.030).  The proportion of women experiencing respiratory events following cesarean birth increases with the degree of obesity and opioid dose. Respiratory events increase with obesity.Respiratory events increase with systemic opioid use.Odds ratio of respiratory events is 1.063/unit BMI increase.