Difficult and failed intubation: Incident rates and maternal, obstetrical, and anesthetic predictors

Background: Difficult and failed tracheal intubation may be more common in the obstetrical population. The objective of this study was to determine the incidence of difficult and failed tracheal intubation in a Canadian tertiary care obstetric hospital and to identify predictors. Methods: Maternal, perinatal, and anesthetic information on all pregnant women or recently pregnant (up to three days postpartum) women undergoing general anesthesia (GA) from 1984 to 2003 at the Izaac Walton Killam Health Centre (IWK) was abstracted from the Nova Scotia Atlee Perinatal Database, and the information was augmented by chart review. The incidence and predictors of difficult and failed tracheal intubation were determined. Analyses using logistic regression were performed for the complete GA cohort and for the subgroup that had Cesarean delivery under GA. Results: There were 102, 587 deliveries of ≥20 weeks gestation in the study population, with 3,107 GAs identified, 2,986 records reviewed, and 2,633 GAs (88%) retained in the complete cohort. Difficult tracheal intubation was encountered in 123 of 2,633 (4.7%) women in the complete cohort and 60 of 1,052 (5.7%) women in the Cesarean delivery subgroup. Only two failed tracheal intubations were identified (0.08%) in the complete cohort, and both occurred during GAs for postpartum tubal ligation. The combined rate of difficult/failed tracheal intubation remained stable over the 20 years reviewed despite decreasing GA rates. Amongst the complete cohort, maternal age ≥35 yr, weight at delivery 90 to 99 kg, and absence of labour predicted increased risks; while weight at delivery 90 to 99 kg and absence of labour amongst the Cesarean delivery subgroup predicted difficult/failed tracheal intubation. Conclusion Previously accepted risk factors, such as labour, pre-existing medical conditions and obstetrical disorders, did not predict an increased risk of difficult tracheal intubation, while maternal age ≥35 yr, weight 90 to 99 kg, and absence of active labour were found to predict increased risk.