The predictive value of the ratio of neck circumference to thyromental distance in comparison with four predictive tests for difficult laryngoscopy in obstetric patients scheduled for caesarean delivery.

BACKGROUND: Preoperative assessment of anatomical landmarks andclinical factors help detect potentially difficult laryngoscopies. The aim of the present study was to compare the ability to predict difficult visualization of the larynx from thefollowing preoperative airway predictive indices, in isolation and combination: Neck circumference to thyromental distance (NC/TMD), neck circumference (NC), modified Mallampatitest (MMT), the ratio of height to thyromental distance (RHTMD), and the upper-lip-bite test (ULBT). MATERIALS AND METHODS: We collected data on657 consecutive patients scheduled for elective caesarean delivery under general anesthesia requiring endotracheal intubation and then evaluated all five factors before caesarean. An experienced anesthesiologist, not informed of the recorded preoperative airway evaluation, performed the laryngoscopy and grading (as per Cormack and Lehane's classification). Sensitivity, specificity, and positive and negative predictive values for each airway predictor in isolation and in combination were determined. RESULTS: Difficult laryngoscopy (Grade 3 or 4) occurred in 53 (8.06%) patients. There were significant differences in thyromental distance (TMD), RHTMD, NC, and NC/TMD between difficult visualization of larynx and easy visualization of larynx patients (P < 0.05). The main end-point area under curve (AUC) of the receiver-operating characteristic (ROC) was lower for MMT (AUC = 0.497; 95% Confidence Interval = CI,0.045-0.536) and ULBT (AUC = 0.500, 95% CI, 0.461-0.539) compared to RHTMD, NC, TMD, and NC/TMD score ([AUC = 0.627, 95% CI, 0.589-0.664], [AUC = 0.691; 95% CI, 0.654-0.726], [AUC = 0.606; 95% CI, 0.567-0.643], [AUC = 0.689;95% CI, 0.625-0.724], respectively), and the differences of six ROC curves were statistically significant (P < 0.05). CONCLUSION: The NC/TM Discomparable with NC, RHTMD, and ULBT for the prediction of difficult laryngoscopy in caes are an delivery.

Comparing the effects of three different additional doses of propofol infusion on intubation condition and hemodynamic changes during general anesthesia under elective surgery: A randomized, placebo-controlled, double blind clinical trial.

BACKGROUND: Laryngoscopy and endotracheal intubation can induce unfavorable hemodynamic changes as propofol itself can induce hypotension. The aim of this study was to compare the effects of three different additional doses of propofol infusion on intubation conditions and hemodynamic changes occurred after intubation. MATERIALS AND METHODS: This double-blinded prospective study was performed on 140 patients aged 18-60 who received different additional doses of propofol and were randomly allocated into 4 groups as follows: A: Received additional dose of propofol 0.5 mg/kg infused after an initial dose 1.5 mg/kg. B: Received additional dose of propofol 1 mg/kg infused after an initial dose 1 mg/kg. C: Received additional dose of propofol 1.5 mg/kg after an initial dose 1 mg/kg. D: Received propofol 2 mg/kg as a bolus with no additional dose. RESULTS: Intubation conditions were acceptable in 91.4% of Group A patients, 94.2% of Group B patients, 97.1% of Group C patients and 68.5% of Group D patients. There were no significant differences in the mean of heart rate between four groups at any time before and after laryngoscopy. Mean arterial pressure (MAP) 3 min after laryngoscopy was significantly lower in Group D versus Group A (P = 0.015) while MAP was not different at any time between other groups. CONCLUSION: Infusion of propofol 1.5 mg/kg added to initial bolus dose of propofol 1 mg/kg improves intubation conditions significantly without inducing hemodynamic changes.