The dose of succinylcholine required for excellent endotracheal intubating conditions.

In this prospective, randomized, double-blind, placebo-controlled study, we attempted to define the dose of succinylcholine that provides excellent intubation conditions in patients within 60 s during simulated rapid-sequence induction of anesthesia. Anesthesia was induced in 180 patients with 2 microg/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.3, 0.5, 1.0, 1.5, or 2.0 mg/kg succinylcholine or saline solution (control group). Tracheal intubation was performed 60 s later. A blinded investigator performed all laryngoscopies and graded intubating conditions. Intubating conditions were excellent in 0.0%, 43.3%, 60.0%, 63.3%, 80.0%, and 86.7% of patients after 0.0, 0.3, 0.5, 1.0, 1.5, and 2.0 mg/kg succinylcholine, respectively. The incidence of excellent intubating conditions was significantly more frequent (P < 0.001) in patients receiving succinylcholine than in the controls and in patients who received 2.0 mg/kg succinylcholine (P < 0.05) than in those who received 0.3 mg/kg succinylcholine. The calculated doses of succinylcholine (and their 95% confidence intervals) that are required to achieve excellent intubating conditions in 50% and 80% of patients at 60 s are 0.39 (0.29-0.51) mg/kg and 1.6 (1.2-2.0) mg/kg, respectively. It appears that there are no advantages to using doses of succinylcholine larger than 1.5 mg/kg.

The effect of positive pressure ventilatory patterns on post-bypass lung functions.

BACKGROUND: This study aimed at evaluating the effect of application of different patterns of positive ventilatory pressure either during or after cardiopulmonary bypass (CPB), on lung functions. METHODS: 30 patients undergoing coronary artery revascularisation under the management of CPB were randomly allocated into 3 groups. Group I (VCM) 10 patients were subjected to manual vital capacity manoeuvre (VCM) before weaning off the CPB. Group II (CPAP) 10 patients were subjected to continuous positive airway pressure (CPAP) of 10 cmH2O during CPB. Group III (PEEP) 10 patients were subjected to positive end expiratory pressure (PEEP) of 7 cmH2O after weaning off the CPB. Measurements included the PO2, PCO2, together with derived calculated parameters as the alveolar-arterial oxygen difference [P (A-a) DO2] and shunt fraction, as well as the dynamic lung compliance being recorded directly from the anesthetic and ventilatory equipments. All readings were taken on closed chest and on FiO2 of 0.5. Intraoperative anesthetic and surgical data as well as postoperative extubation time and length of ICU stay were also evaluated. RESULTS: Statistical analysis of ventilatory parameters showed no significant differences for both PO2 and PCO2 in between the studied groups. Alveolar-Arterial oxygen difference mean values were comparable in the 3 studied groups. The mean values of intrapulmonary shunt fraction showed a significant difference in relation to the baseline values in Group I (VCM) and Group III (PEEP) at 30 minutes after ICU admission and 4 hours post CPB with estimated P value < 0.01 and < 0.05 respectively, while in Group II (CPAP) mean values started to be significant after chest closure with a P value < 0.05, but there was no significant intergroup differences with a P value > 0.01. Dynamic lung compliance mean values showed no intergroup statistical significance. CONCLUSION: Maintenance of ventilatory parameters was achieved in all the positive pressure ventilatory methods applied, either being applied during or after CPB.