STERNOMENTAL DISTANCE AS THE SOLE PREDICTOR OF DIFFICULT LARYNGOSCOPYIN OBSTETRIC ANESTHESIA

Sternomental distance and view at laryngoscopy were documented in 523 parturients undergoing elective or emergency Caesarean section under g eneral anaesthesia. Eighteen (3.5%) had a grade III or IV laryngoscopi c view (Cormack and Lehane's classification) and were classified as po tentially difficult tracheal intubations. There was a significant diff erence between sternomental distance in those patients with a grade II I or IV laryngoscopic view compared with those with a grade I or II (1 3.17 (SD 1.54) cm vs 14.3 (1.49) cm; P = 0.0013). A sternomental dista nce of 13.5 cm or less with the head fully extended on the neck and th e mouth closed provided, using discriminant analysis, the best cut-off point for predicting subsequent difficult laryngoscopy. A sternomenta l distance of 13.5 cm or less had a sensitivity, specificity, positive and negative predictive values of 66.7%, 71.1%, 7.6% and 98.4%, respe ctively. While there was no association between sternomental distance and age, weight, height or body mass index (BMI), there was a signific ant association between grade of laryngoscopy (III and IV) and older ( P = 0.049) and heavier (P = 0.0495) mothers. The results suggest that while sternomental distance on its own may not be an adequate sole pre dictor of subsequent difficult laryngoscopy the measurement should be incorporated into a series of quick and simple preoperative tests.