PREDICTION OF DIFFICULT LARYNGOSCOPY IN PREGNANT WOMEN UNDERGOING CESAREAN SECTION USING THE HYOMENTAL DISTANCE IN FULLY EXTENDED AND NEUTRAL POSITION OF NECK, IN COMPARISON WITH FOUR USUAL BEDSIDE TESTS: A PROSPECTIVE BLINDED STUDY

Background: Unexpected difficult intubation that maybe considered to failed intubation is a major factor to be related to mortality and morbidity following general anesthesia. We aimed to elucidate the role of hyomental Distance in fully extended and neutral position of neck with other prevailing test and their possible correlation in predicting difficult laryngoscopy in parturient undergoing cesarean section. Materials and Methods: After institutional approval and obtaining inform consents, 716 consecutive parturient ASA physical status I and II scheduled for elective cesarean section under general anesthesia, were enrolled to this study. Each patient was evaluated regarding Hyomental distance in extended (HMDe) and neutral position of neck(HMDn), Neck circumference to Thyromental Distance(NC/TMD), Ratio of height to Thyromental Distance(RHTMD), Modified Mallampatti Test (MMT) and Upper Lip Bite Test(ULBT) before induction. Laryngoscopic result was graded according to Cormack-Lehane Classification. Sensitivity, specificity, positive predictive value and AUC or ROC for each airway predictor in isolation and in comparison with each other was established. Results: The sensitivity of HMDe and HMDn was 49.2 and 47.7% respectively. Sensitivity of MMT as an old predictive test was 79.3% in comparison with sensitivity of NC/TMD, RHTMD and ULBT (58.3%, 41.6% and 50.7% respectively). The differences of Area under Curve in all tests except ULBT were statistically significant (P < 0.05). Conclusion: In addition to MMT (as an ancient predictor), NC/TMD and HMD in neutral position and fully extended of the neck; in parturient are good and reliable predictors of difficult laryngoscopy and intubation.