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.

Appearance and evolution of calcium currents and contraction during the early post-fusional stages of rat skeletal muscle cells developing in primary culture.

Primary cultures from enzymatically dissociated satellite cells of newborn rat skeletal muscles enabled developmental in vitro studies of mechanical and electrical properties during the first steps of myogenesis. The present work focused on the appearance, evolution and roles of two types of calcium currents (ICa,T and ICa,L) and of depolarization-induced contractile activity during the early stages of muscle cell development in primary culture. Prefusional mononucleated cells (myoblasts), young myotubes of 1 day (with less than 10 nuclei) or 2-3 days (more than 9 nuclei) and myoballs from 4-6, 7-9, 10-12 and 13-16 days cultures were patch-clamped (whole-cell configuration), and calcium currents and contraction simultaneously recorded. Sodium but not calcium currents could be recorded at the myoblast stage. In young myotubes (1 day), ICa,L was present with high incidence as compared to ICa,T, which was poorly expressed. Contractile responses appeared at the next stage (2-3 days) while the occurrence of ICa,T progressively increased. This developmental evolution of the calcium currents and contraction expression was accompanied by some changes in their characteristics: the ICa,T/ICa,L amplitudes ratio progressively increased and the time-to-peak of contraction progressively decreased with the age of myoballs. Physiological functions for calcium currents in developing muscle are suggested and discussed: ICa,T, which is transiently expressed, could be involved in the pacemaker-like activity while ICa,L could serve as an early contraction triggering mechanism and/or initially to fill and then to maintain the intracellular calcium stores.