Prospective validation of a new airway management algorithm and predictive features of intubation difficulty.

BACKGROUND: Some patients have features that indicate possible difficulty with direct laryngoscopy for tracheal intubation. Prediction of the likely outcome and selection of patients for an enhanced management algorithm would reduce the possible harm from failed intubation attempts. METHODS: Adult elective patients were assessed for seven features associated with difficult direct laryngoscopy, ranked in difficulty from 0 to 3. For a patient with at least one Class 3 feature, or two or more features of class 1 or higher, the enhanced management used a channelled videolaryngoscope Airtraq™ instead of a Macintosh laryngoscope. A long flexible angulated stylet and a flexible fibrescope would be used as the second and third steps. For patients with lesser difficulty scores, a Macintosh laryngoscope was used. Outcomes of enhanced management were analysed. Logistic regression and Random Forest algorithm, using the ranks of the predictive features, were used to predict difficulty during enhanced management. RESULTS: We prospectively studied 16 695 patients. We selected 1501 (9%) for enhanced management, and tracheal intubation was successful in all of them. Of these, 73% were intubated in less than 30 s, and only 4.5% required more than 4 min for intubation. Progression to the second and third steps of enhanced management was predicted by restriction of mouth opening and reduced cervical spine mobility. CONCLUSIONS: An enhanced management algorithm allowed successful tracheal intubation of all patients with anticipated difficult laryngoscopy. The need to combine the use of a stylet and a fibrescope with the Airtraq™ could be predicted with a high degree of certainty.

Halothane and isoflurane decrease alveolar epithelial fluid clearance in rats.

BACKGROUND: Active sodium transport is the primary mechanism that drives alveolar fluid clearance. In the current study, the effects of exposure to halothane and isoflurane on alveolar fluid clearance in rats were evaluated. METHODS: Rats were exposed to either halothane (0.4% for 6 h or 2% for 2 h) or isoflurane (0.6% for 6 h or 2.8% for 2 h). Reversibility of halothane effects was assessed after 2 h of exposure to 2% halothane. Alveolar and lung liquid clearance were measured by intratracheal instillation of a 5% albumin solution with 1.5 microCi of 125I-albumin, during mechanical ventilation with 100% FiO2 and the halogenated agent. The effect of terbutaline (10(-4) M) added to the albumin solution was tested after 2 h of exposure to 2% halothane. The increase in protein concentration in the airspaces over 1 h was used to evaluate alveolar liquid clearance. Lung liquid clearance was calculated gravimetrically. RESULTS: Alveolar liquid clearance rates were decreased by 24%, 30% and 40% compared with controls (P < 0.05) after 2 h of exposure to halothane, 6 h of exposure to halothane, and 6 h of exposure to isoflurane, respectively. After 2 h of exposure to isoflurane, alveolar liquid clearance did not change. In the 2-h halothane exposure group, alveolar liquid clearance returned to the control value 2 h after withdrawal of halothane. Terbutaline increased alveolar liquid clearance by 50% and 89% in the control and 2-h halothane exposure groups, respectively. In all experiments, the same results were obtained for alveolar and lung liquid clearance. CONCLUSIONS: Halothane and isoflurane caused a reversible decrease in alveolar epithelial fluid clearance. Two hours of exposure to halothane did not alter the stimulatory effect of terbutaline on alveolar liquid clearance.