Risk of Difficult Airway in Obstetric Patients in a Teaching Institution
Abstract Number: 87
Abstract Type: Original Research
The decision to perform general vs. regional anesthesia requires understanding the risk of failed intubation in parturients. We aim to determine the incidence of difficult and failed intubations, and to correlate pre-operative airway evaluation findings with the intra-operative encounter.
Methods: From June 2001 through February 2006, pre- and post-operative airway evaluations and intra-operative encounters were studied in 2,158 patients undergoing pregnancy-related surgical procedures requiring general anesthesia. A difficult airway was defined as needing three or more direct laryngoscopy (DL) attempts, or use of the additional airway equipment after the DL attempts, or conversion to regional anesthesia due to inability to intubate. Airway characteristics were compared between patients with and without a difficult airway.
Results: Of the 2,158 obstetric patients who underwent general anesthesia, 1,026 (47.5%) were for emergency Caesarian section (C/S), 610 (28.3%) were for non-emergency C/S, and 522 (24.2%) were for non-C/S procedures, such as dilatation and curettage, tubal ligation, and exploratory laparotomy following C/S. A total of 12 patients (0.56%) were identified as having a difficult airway. Of these 12 patients, four (33.3%) had emergency C/S, two (16.7%) had non-emergency C/S, and six (50.0%) had non-C/S procedures. Four patients were intubated with further DL attempts, one required a gum-elastic bougie, and one required Ambu bag ventilation. Two patients were intubated via an intubating laryngeal mask airway (iLMA), two with a fiberoptic scope via the iLMA, and two were ventilated through the iLMA with cricoid pressure without further intubation attempts. Ten of the 12 difficult airway cases were encountered by residents during their first year of clinical anesthesia training. There was one case of possible maternal aspiration who recovered uneventfully without treatment, and there were no other maternal or fetal complications. There were no cases of conversion to regional anesthesia. There were no difference in the incidence of difficult airway between C/S and non-C/S procedures, nor between emergency and non-emergency C/S. Poor view during DL was associated with a difficult airway (p < 0.01) but there were no pre-operative airway exam variables that could predict a poor laryngoscopic view upon DL and a subsequent difficult airway. There were no significant changes in airway characteristics postoperatively.
Conclusions: Difficult airway is a relatively uncommon, accounting for 0.56% of all pregnancy-related surgical patients. Even with this incidence of difficult airway, over 99.9% of all obstetric patients could be intubated. The incidence of difficult airway appears to be lower among experienced operators. Proper use of LMA or iLMA may provide adequate ventilation in patients who are not ventilated. Emergency C/S did not add an additional level of difficulty over non-emergency C/S.