Joel A. Bennett

Difficult or Impossible Ventilation after Sufentanil-induced Anesthesia Is Caused Primarily by Vocal Cord Closure

Introduction: Opioid‐induced rigidity often makes bag‐mask ventilation difficult or impossible during induction of anesthesia. Difficult ventilation may result from chest wall rigidity, upper airway closure, or both. This study further defines the contribution of vocal cord closure to this phenomenon. Methods: With institutional review board approval, 30 patients undergoing elective cardiac surgery participated in the study. Morphine (0.1 mg/kg) and scopolamine (6 micro gram/kg) given intramuscularly provided sedation along with intravenous midazolam as needed. Lidocaine 10% spray provided topical anesthesia of the oropharynx. A fiberoptic bronchoscope positioned in the airway photographed the glottis before induction of anesthesia. A second photograph was obtained after induction with 3 micro gram/kg sufentanil administered during a period of 2 min. A mechanical ventilator provided 10 ml/kg breaths at 10/min via mask and oral airway with jaw thrust. A side‐stream spirometer captured objective pulmonary compliance data. Subjective airway compliance was scored. Pancuronium (0.1 mg/kg) provided muscle relaxation. One minute after the muscle relaxant was given, a third photograph was taken and compliance measurements and scores were repeated. Photographs were scored in a random, blinded manner by one investigator. Wilcoxon signed rank tests compared groups, with Bonferroni correction. Differences were considered significant at P <0.05. Results: Twenty‐eight of 30 patients exhibited decreased pulmonary compliance and closed vocal cords after opioid induction. Two patients with neither objective nor subjective changes in pulmonary compliance had open vocal cords after opioid administration. Both subjective and objective compliances increased from severely compromised values after narcotic‐induced anesthesia to normal values (P = 0.000002) after patients received a relaxant. Photo scores document open cords before induction, progressing to closed cords after the opioid (P = 0.00002), and opening again after a relaxant was administered (P = 0.00005). Conclusion: Closure of vocal cords is the major cause of difficult ventilation after opioid‐induced anesthesia.

Activated coagulation time : One tube or two ?

Abstract Objectives: To compare activated coagulation time (ACT) management directed by a single ACT determination to that of the average of two simultaneously obtained ACT values Design: Prospective study. Setting: Cardiac operating rooms of a university hospital. Participants: Patients undergoing surgery requiring cardiopulmonary bypass. Interventions: All ACT determinations were performed in duplicate; patients were managed based on the average of the duplicate values, as is customary. Results of all tests were recorded on a spreadsheet, and the management dictated by a randomly chosen single result of each pair was compared with the management directed by the average value of each pair. Predetermined criteria were set for preference of one testing method over the other. Patients were grouped according to preoperative heparin exposure, and results of the two groups were compared. Measurements and Main Results: One hundred patients underwent 683 paired celite ACT determinations. In 565/683 tests (83%), both methods called for identical heparin management responses. Management by the single-tube method would have resulted in supplemental heparin administration 34% more often than management by the average method. The single-tube method would have resulted in withholding supplemental heparin 13 times when the average method called for supplemental heparin administration, a 16% occurrence. The results of the patients with and without preoperative heparin exposure were not significantly different. Conclusions: The results of this study suggest the use of a two-tube average method to guide heparin administration for cardiopulmonary bypass. Preoperative heparin exposure did not influence this outcome.