Laryngeal injuries and intubating conditions with or without muscular relaxation: an equivalence study.

PURPOSE: The need for muscular relaxation to improve intubating conditions and to reduce the incidence of laryngeal morbidity is still controversial. The aim of this study was to determine the incidence of symptomatic laryngeal injuries (SLI) and of acceptable intubating conditions (including both good and excellent conditions), both with and without cisatracurium during induction of anesthesia, along with moderate doses of remifentanil and propofol. METHODS: In this prospective, randomized double-blind equivalence trial, the intubating conditions were compared in 130 ASA I or II female patients. All subjects received remifentanil 2 microg x kg(-1) i.v. and propofol 2.5 mg x kg(-1) i.v., with either cisatracurium 0.15 mg x kg(-1) i.v. (group Cisatracturium), or saline (group Placebo). Tracheal intubating conditions were assessed with the Copenhagen Score. A systematic screening for postoperative hoarseness and sore throat was performed 24 and 48 hr after anesthesia, followed by a nasofibroscopic examination when laryngeal symptoms persisted at 48 hr. RESULTS: Twenty-four hr after anesthesia, the incidence of postoperative hoarseness and sore throat in the Cisatracurium and Placebo groups was 26.5% and 21.5%, respectively, and 48 hr after anesthesia, the incidence was 7.8% and 6.1%, respectively (P = 0.32 and P = 0.50 between groups, respectively). In the clinically evaluable population, the incidence of SLI, assessed at 48 hr by nasofibroscopy, was equivalent in both groups, 1.6% vs 1.5% in group Placebo and group Cisatracurium, respectively (P < 0.001 for equivalence test), as was the occurrence of acceptable intubating conditions (95.4% vs 100%, P < 0.05 for equivalence test). However, the occurrence of excellent intubating conditions was more frequent in group Cisatracurium than in group Placebo (P = 0.0003). CONCLUSION: Following induction of anesthesia with propofol and moderate-dose remifentanil, cisatracurium did not confer a higher rate of good-to-excellent conditions for tracheal intubation, nor did muscle relaxation with cisatracurium decrease the rate of SLI after tracheal intubation.

Use of a pharmacokinetic-dynamic model for the automatic feedback control of atracurium.

A control algorithm for the closed-loop control of atracurium-induced neuromuscular blockade based on pharmacokinetic-dynamic model-based adaptive feedback is described. Mean offset from setpoint at 90% neuromuscular block was 0.04% and the mean standard deviation from mean neuromuscular block was 1.9%. The mean average atracurium requirement was 0.37 mg.kg-1.h-1. The model-based adaptive closed-loop control of atracurium infusion provided reasonable control of muscle relaxation. It offers a solution to the problem of adapting pharmacokinetic and pharmacodynamic data to individuals when using mean data as starting values for drug therapy.

The use of muscle relaxant to supplement local anaesthetics for Bier's blocks.

In searching for the 'ideal' muscle relaxant for use with intravenous regional anaesthesia, muscle relaxation was assessed with and without the addition of Atracurium to Bier's Block in four volunteers. This was followed by a clinical study of 36 patients with wrist fractures to confirm the drug's safety and examine the possible clinical advantages of using a muscle relaxant. The addition of 2 mg of Atracurium to the Bier's Block improved the ease of reduction (P less than 0.025) and the quality of analgesia (P less than 0.05) (Mann-Whitney U test). The authors conclude that the addition of Atracurium to a Bier's Block is useful in selected patients with a wrist fracture.