Shunichi Nitta

Predicting difficult intubation with indirect laryngoscopy

Background It is not always possible to predict when tracheal intubation will be difficult or impossible. The authors wanted to determine whether indirect laryngoscopy could identify patients in whom intubation was difficult. Methods Indirect laryngoscopy was done in 2,504 patients. The Wilson risk sum score and the modified Mallampati score were also studied in a different series of 3,680 patients for comparison. These predictive methods were compared according to three parameters: positive predictive value, sensitivity, and specificity. Results Of 6,184 patients studied, the trachea proved difficult to intubate in 82 (1.3%). Positive predictive value (31%) and specificity (98.4%) with indirect laryngoscopy were greater than the other two predictive methods (P < 0.01), whereas sensitivity with indirect laryngoscopy (69.2%) was greater than that of the Wilson risk sum score (55.4%) (P < 0.01). Conclusions Although in 15% of patients indirect laryngoscopy could not be performed because of excessive gag reflex, indirect laryngoscopy can serve as an effective method to predict difficult intubation.

Sensitivity to vecuronium in seropositive and seronegative patients with myasthenia gravis.

Patients with myasthenia gravis (MG) are hypersensitive to nondepolarizing neuromuscular blocking drugs. Although antibodies to the acetylcholine receptor (AChR) often are observed in MG patients, 10% to 30% of patients do not show an anti-AChR antibody. Little is known about differences in sensitivity to nondepolarizing neuromuscular blocking drugs between MG patients with and without anti-AChR antibody. Hypothesizing that seronegative patients are as sensitive to vecuronium as seropositive patients, we assessed sensitivity in seropositive and seronegative MG patients and in non-MG patients (n = 8 each). During anesthesia with sevoflurane (2.5%) and nitrous oxide (60%) in oxygen, neuromuscular transmission was monitored by measuring the twitch tension of the adductor pollicis muscle with supramaximal stimulation. After baseline measurements, 10 &mgr;g/kg IV dose increments of vecuronium were administered sequentially until blockade exceeded 90%. The degree of blockade and onset time after the initial 10 &mgr;g/kg of vecuronium were assessed, and doses required to exceed 90% blockade were recorded. In addition, effective doses of 50% and 95% for vecuronium were calculated from a single data point. Both types of MG patients showed increased sensitivity to vecuronium compared with non-MG patients.

Comparison of Respiratory Sparing Effect on Pancuronium, Vecuronium and Rocuronium in Rats in Vivo

Respiratory muscles are more resistant to the action of muscle relaxants (MRs) such as pancuronium (PAN) than peripheral muscles, and this concept has been called respiratory sparing effect (RSE). Regarding to vecuronium (VEC) and rocuronium (ROC), however, the RSE has not been clearly elucidated yet. The aim of the present study was to compare the magnitude of RSE in rats on three steroidal MRs: PAN, VEC and ROC.