Comparison of rocuronium and suxamethonium for use during rapid sequence induction of anaesthesia.

This study was designed to compare the tracheal intubating conditions during a rapid sequence induction of anaesthesia using rocuronium 0.6 (n = 61) or 1.0 mg.kg-1 (n = 130) or suxamethonium 1.0 mg.kg-1 (n = 127) as the neuromuscular blocking drugs. Anaesthesia was induced with fentanyl 1-2 micrograms.kg-1 and thiopentone 5 mg.kg-1 (median dose) and intubating conditions were assessed 60s after the administration of the neuromuscular blocking drug by an observer unaware of which drug had been given. Intubating conditions were graded on a three-point scale as excellent, good or poor, the first two being considered clinically acceptable. The study was carried out in two parts. At the end of the first part a comparison between the two doses of rocuronium was carried out when at least 50 patients had been enrolled in each group. The results showed the intubating conditions to be significantly superior with the 1.0 mg.kg-1 dose of rocuronium (p < 0.01). Final comparison between the 1.0 mg.kg-1 doses of rocuronium and suxamethonium showed no significant difference in the incidence of acceptable intubations (96 and 97%, respectively). The incidence of excellent grade of intubations was, however, significantly higher with suxamethonium (80% vs. 65%; p = 0.02). It is concluded that rocuronium 1.0 mg.kg-1 can be used as an alternative to suxamethonium 1.0 mg.kg-1 as part of a rapid sequence induction provided there is no anticipated difficulty in intubation. The clinical duration of this dose of rocuronium is, however, 50-60 min.

Dose-response and concentration-response relation of rocuronium infusion during propofol-nitrous oxide and isoflurane-nitrous oxide anaesthesia.

The dose-response and concentration-response relation of rocuronium infusion was studied in 20 adult surgical patients during propofol-nitrous oxide and isoflurane (1 MAC)-nitrous oxide anaesthesia. Neuromuscular block was kept constant, initially at 90% and then at 50% with a closed-loop feedback controller. At 90% block the steady-state infusion of rocuronium was 0.55 +/- 0.16 mg kg-1 h-1 and the corresponding concentration 1714 +/- 281 ng mL-1 in patients receiving propofol. At 50% block the corresponding infusion rate was 0.27 +/- 0.11 mg kg-1 h-1 and the concentration 1077 +/- 244 ng mL-1, respectively. At 50% block isoflurane reduced the rate of infusion by 52% (P < 0.005) and the concentration by 59% (P < 0.001); at 90% block both the mean infusion rate and the concentration of rocuronium were reduced by 35% (P < 0.005). The mean rocuronium clearance at 50% block was unaffected by the type of anaesthesia; it was 4.1 +/- 1.6 and 4.9 +/- 2.7 mL kg-1 min-1 in the groups receiving propofol and isoflurane anaesthesia, respectively. We conclude that isoflurane reduces the infusion requirements of rocuronium by changing the pharmacodynamic behaviour.

The effect of halothane on mivacurium infusion requirements in adult surgical patients.

BACKGROUND: The extent of interaction between volatile anaesthetics and neuromuscular blocking agents depends both on the inhalational anaesthetic and the muscle relaxant. Halothane has the weakest potentiating effect on neuromuscular blocking drugs and previous studies of the interaction between halothane and mivacurium have been contradictory. We were interested in determining the effect of different levels of halothane-nitrous oxide anaesthesia on infusion requirements of mivacurium. METHODS: Sixty adult surgical patients were studied. Anaesthesia was induced with thiopentone and fentanyl and intubation facilitated with mivacurium 0.15 mg.kg-1. The patients were randomly assigned to one of four study groups. The control group received nitrous oxide in oxygen (2:1) supplemented with fentanyl, while in the other groups halothane was administered at different end-tidal concentrations: 0.19% (group 2), 0.37% (group 3), 0.74% (Group 4), corresponding to 0.25, 0.5 and 1.0 MAC of halothane. Neuromuscular block was kept at 95% with a closed-loop feedback infusion of mivacurium and monitored with electromyography. Plasma cholinesterase concentrations and dibucaine numbers were determined. RESULTS: Mivacurium infusion requirements (mean +/- SD) were 7.5 +/- 3.1 micrograms.kg-1.min-1 with nitrous oxide-fentanyl anaesthesia. In the groups receiving 0.25, 0.5 or 1.0 MAC of halothane the steady-state infusion rates of mivacurium were reduced to 6.3 +/- 2.8, 5.6 +/- 1.4 and 5.7 +/- 2.5 micrograms.kg-1.min-1 (P < 0.05), respectively. There was a linear relationship between mivacurium infusion requirements and plasma cholinesterase activity. CONCLUSIONS: Halothane anaesthesia reduces mivacurium infusion requirements by 15-25% compared to nitrous oxide-fentanyl anaesthesia. Interindividual differences in the extent of this interaction are great.

Model-driven closed-loop feedback infusion of atracurium and vecuronium during hypothermic cardiopulmonary bypass.

OBJECTIVE: This study was designed to investigate the performance of a computer-controlled infusion of atracurium and vecuronium during cardiac surgery requiring hypothermic cardiopulmonary bypass. DESIGN: Prospective, randomized study. SETTING: A single university hospital. PARTICIPANTS: Twenty patients scheduled for cardiac surgery. INTERVENTIONS: After induction of anesthesia with fentanyl and diazepam, 10 patients were randomly allocated to receive a bolus of atracurium and 10 patients a bolus dose of vecuronium to facilitate endotracheal intubation. The initial bolus was followed by a computer-controlled closed-loop feedback infusion of atracurium or vecuronium until the patients were transferred to the postoperative intensive care unit. The desired level of neuromuscular blockade, as measured by EMG, was set to 90%. Anesthesia was maintained with a mixture of oxygen and air and either enflurane or halothane. MEASUREMENTS AND MAIN RESULTS: The groups were similar with respect to patient characteristics. Except during hypothermic CPB, the controller kept the neuromuscular blockade near the set point in both groups. During hypothermic CPB the maximal oscillation of muscle relaxation was within 10% from the set point. When CPB was initiated, the mean rates of infusion of the muscle relaxants increased from the pre-CPB values, but the change of the infusion rate was not statistically significant for atracurium. During the remainder of CPB, the infusion requirements of both muscle relaxants were greatly reduced, but rewarming essentially returned the infusion requirements to pre-CPB values. CONCLUSIONS: The computer-controlled infusion can be used for the administration of atracurium and vecuronium during CPB.

Performance assessment of an adaptive model-based feedback controller: comparison between atracurium, mivacurium, rocuronium and vecuronium.

The performance of an adaptive model-based controller for the administration of atracurium, mivacurium, rocuronium and vecuronium was compared in 159 adult surgical patients. The degree of neuromuscular block was set to 90% for atracurium, rocuronium and vecuronium and to 95% for mivacurium. Performance was assessed by calculating the median prediction error (bias), median absolute performance error (inaccuracy), divergence, wobble, the mean offset and the mean standard deviation from the setpoint. All indices of controller performance showed minimal deviation of the actual neuromuscular block from the setpoint. Although the controller appeared to be able to control rocuronium induced block at 90% and mivacurium induced block at 95% better than atracurium and vecuronium block at 90%, the differences in the controller performance between the four studied relaxants were small and have hardly any clinical significance. We conclude that a model-based adaptive controller is useful in the administration of atracurium, mivacurium, rocuronium or vecuronium.

Quantifying the effect of isoflurane on mivacurium infusion requirements.

We evaluated the effect of different concentrations of isoflurane in a nitrous oxide/oxygen mixture on the infusion requirements of mivacurium in 60 adult surgical patients. Anaesthesia was induced with thiopentone and fentanyl, and intubation was facilitated with mivacurium 0.15 mg.kg-1. The patients were randomly assigned to one of four study groups. The control group received nitrous oxide in oxygen (2:1) anaesthesia supplemented with fentanyl. In the other groups, isoflurane was administered at different end-tidal concentrations: 0.29%, 0.58% and 1.15%, corresponding to 0.25, 0.5 and 1.0 MAC of isoflurane, respectively. Neuromuscular block was maintained at 95% with a computer-controlled infusion of mivacurium and monitored with electromyography. The mean (SD) steady-state infusion requirements of mivacurium in patients receiving nitrous oxide-fentanyl anaesthesia or isoflurane 0.25-0.5 MAC were similar, ranging from 6.1 (2.2) to 5.1 (2.1) micrograms.kg-1.min-1. Isoflurane 1.0 MAC reduced mivacurium infusion requirements by 32% (p < 0.01). Interindividual differences in mivacurium infusion requirements were large.

Quantifying the interaction of vecuronium with enflurane using closed-loop feedback control of vecuronium infusion.

The influence of different levels of enflurane anaesthesia on infusion requirements of vecuronium was studied in 40 adult surgical patients. Ninety percent neuromuscular block was maintained by computer controlled infusion of vecuronium. During the first 90 min study period all patients received fentanyl-nitrous oxide-oxygen (2:1) anaesthesia. For the following 90 min the patients were randomly assigned to receive enflurane at different end-tidal concentrations: group I, control, fentanyl-nitrous oxide anaesthesia; group II, enflurane 0.3%-nitrous oxide; group III, enflurane 0.6%-nitrous oxide; group IV, enflurane 0.9%-nitrous oxide. Every patient served as his/her own control and the changes of vecuronium infusion requirements were determined individually. When the administration of enflurane was started, vecuronium infusion requirements decreased progressively until 90 min. In group II the infusion rate lowered from 80 +/- 28 to 56 +/- 20 micrograms.kg-1.h-1, in group III from 61 +/- 29 to 34 +/- 17 micrograms.kg-1.h-1 and in group IV from 65 +/- 20 to 30 +/- 14 micrograms.kg-1,h-1. In the control group the infusion rate decreased during the three hour study period from 69 +/- 17 (first 90 min period) to 59 +/- 16 micrograms.kg-1.h-1 (second 90 min period). Enflurane reduces the dose requirements of vecuronium administered by continuous infusion in a dose- and time-dependent manner.

Early detection of CO2 pneumothorax with continuous spirometry during laparoscopic fundoplication.

In two patients, operated on because of gastroesophageal reflux, carbon dioxide pneumothorax developed during laparoscopic Nissen fundoplication. In both instances, decrease of lung compliance and a change of pressure-volume loop configuration, computed and illustrated with on-line spirometry, led quickly to diagnosis of this complication. We conclude that continuous spirometry is valuable as an early indicator of intraoperative pneumothorax.

Quantifying the effect of enflurane on atracurium infusion requirements.

The present study was designed to evaluate the interaction between atracurium and enflurane in 40 adult surgical patients using closed-loop feedback control of infusions of atracurium. Anaesthesia was induced with thiopentone and fentanyl and intubation was facilitated with atracurium 0.5 mg.kg-1 lean body mass. During the first 90 min, anaesthesia was maintained with nitrous oxide in oxygen (2:1) and fentanyl. For the following 90 min the patients were randomly assigned to receive enflurane at different end-tidal concentrations: Group I, control, fentanyl-nitrous oxide anaesthesia; Group II, enflurane 0.3%-nitrous oxide; Group III, enflurane 0.6%-nitrous oxide; Group IV, enflurane 0.9%-nitrous oxide. The possible interaction of atracurium with enflurane was quantified by determining the asymptotic steady-state rate of infusion (ISS) of atracurium necessary to produce a constant 90% neuromuscular block. This was accomplished by applying nonlinear curve fitting to data on the cumulative dose requirements. Every patient served as his/her own control and the changes in the infusion rates were determined individually. Patient characteristics and controller performance, i.e., the ability of the controller to maintain the neuromuscular blockade constant at the setpoint, did not differ among groups. In Group II ISS decreased from 0.33 +/- 0.12 to 0.26 +/- 0.08 mg.kg-1.hr-1 (P < 0.01), in Group III from 0.32 +/- to 0.12 to 0.24 +/- 0.08 mg.kg-1.hr-1 (P < 0.001) and in Group IV from 0.29 +/- 0.09 to 0.21 +/- 0.09 mg.kg-1.hr-1 (P < 0.001). In the control group atracurium requirements remained unchanged throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)