Sternomental distance as the sole predictor of difficult laryngoscopy in obstetric anaesthesia

Abstract

Sternomental distance and view at laryngoscopy were documented in 523 parturients undergoing elective or emergency Caesarean section under general anaesthesia. Eighteen (3.5%) had a grade III or IV laryngoscopic view (Cormack and Lehane's classification) and were classified as potentially difficult tracheal intubations. There was a significant difference between sternomental distance in those patients with a grade III or IV laryngoscopic view compared with those with a grade I or II (13.17 (SD 1.54) cm vs 14.3 (1.49) cm; P = 0.0013). A sternomental distance of 13.5 cm or less with the head fully extended on the neck and the mouth closed provided, using discriminant analysis, the best cut-off point for predicting subsequent difficult laryngoscopy. A sternomental 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%, respectively. While there was no association between sternomental distance and age, weight, height or body mass index (BMI), there was a significant 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 predictor of subsequent difficult laryngoscopy the measurement should be incorporated into a series of quick and simple preoperative tests.

Modified Mallampati Test, Sternomental Distance, and Thyromental Distance for Prediction of Difficult Intubation in Patients Undergoing General Anaesthesia

“…Sensitivity was 81.5%, Specificity 93.9%, PPV 56.4%, NPV 98.1% and Accuracy 92.8% .The study of Savva, in a largely non-obstetric population, found sternomental distance to be the most sensitive (82.4%) and specific (88.6%) determinant of difficult intubation and the results were almost same as our study [15] . The study of S.A.L Ramdhani, A. Mohamed etal, a SMD of 13.5 cmor less had a sensitivity, specificity, positive and negative predictive valueof 66.7%, 71.1%, 7.6%and 98.4% respectively, which were different from our study [16] . This may be due to difference in cut-off value of SMD.…”

Using temporomandibular joint mobility to predict difficult tracheal intubation

“…Cormack-Lehane grade III or IV is generally regarded as difficult [4,5]. The ASA Task Force describes endotracheal intubation as difficult when proper insertion of the tracheal tube with conventional laryngoscopy requires more than three attempts or more than 10 min [6].…”

Prediction of difficult tracheal intubation in Turkish patients: a multi-center methodological study

“…Mallampati classification [6], mouth opening (interincisor gap) [7], head extension [8], thyromental distance [9], sternomental distance [10], protrusion of the mandible [11], tooth morphology [7], radiographic evaluation of head and neck [8], ratio of height to thyromental distance [12], indirect laryngoscopy [13] and a history of difficult intubation have all been used to evaluate the airway. Nevertheless, the diagnostic accuracy of these screening tests has varied from trial to trial [14], probably because of different test thresholds or differences in patient characteristics [15].…”