Incidence and risk factors for maternal hypoxaemia during induction of general anaesthesia for non-elective Caesarean section: a prospective multicentre study

Background: Pregnant women are at increased risk of hypoxaemia during general anaesthesia. Our aim was to determine the incidence and the risk factors that contribute to hypoxaemia in this setting. Methods: Every woman 18 yr or older who underwent a non-elective Caesarean section under general anaesthesia was eligible to participate in this multicentre observational study. The primary endpoint was the incidence of hypoxaemia defined as the SpO(2) <= 95%. The secondary endpoint was the incidence of difficult intubation defined as more than two attempts or failed intubation. Results: During the study period, 895 women were prospectively included in 17 maternity hospitals, accounting for 79% of women who had general anaesthesia for non-elective Caesarean section. Maternal hypoxaemia was observed in 172 women (19%; confidence interval [CI], 17-22%). Risk factors associated with hypoxaemia in the multivariate analysis were difficult or failed intubation (adjusted odds ratio [aOR]=19.1 [8.6-42.7], P<0.0001) and BMI >35 kg m(-2) (aOR=0.53 [0.28-0.998], P=0.0495). Intubation was difficult in 40 women (4.5%; CI, 3.3-6%) and failed intubation occurred in five women (0.56%; CI, 0.1-1%). In the multivariate analysis, use of a hypnotic drug other than propofol was associated with difficult or failed intubation (aOR=25 [2-391], P=0.02). A propensity score confirmed that propofol was associated with a significant decreased risk of difficulty or failure to intubate (P<0.001). Conclusions: Hypoxaemia during Caesarean sections was observed in 19% of women and was significantly associated with difficult or failed intubation. The use of propofol may protect against the occurrence of difficult intubation.