ABSTRACT
Following administration of 0.6 mg kg-1 rocuronium, the pharmacokinetics and the pharmacodynamics were studied in six obese and six control (normal weight) patients receiving balanced anaesthesia. Twelve gynaecological patients were allocated into two groups, according to body mass index (normal weight: body mass index: 20-24, obese weight: body mass index > 28). Venous plasma concentrations were determined by high-pressure liquid chromatography before administration of rocuronium, at 1, 2, 4, 6, 8, 10, 15, 20, 25, 30, 35, 40, 48, 60, 75, 120, 180, 240, 300, 360 and 420 min after administration of rocuronium and at recovery of single twitch to 25% and 75% of control twitch height. Onset time was shorter (NS) in the obese compared with normal weight (obese weight: 65 +/- 16, normal weight: 100 +/- 39 s, mean +/- SD). Duration 25% (obese weight: 29.5 +/- 5.3, normal weight: 28.4 +/- 5.3 min) and spontaneous recovery time (obese weight: 12.6 +/- 2.7, normal weight: 12.5 +/- 2.3 min) did not show any differences between the two groups. The pharmacokinetics of rocuronium were comparable in the two groups. The volume of distribution at steady state Vss (mL kg-1) was 208 +/- 56 in normal weight and 169 +/- 37 in obese weight. Distribution (T1/2 alpha) and elimination half-life (T1/2 beta) as well as mean residence time were 15.6 +/- 3.7, 70.3 +/- 23.9 and 53.2 +/- 9.8 min in normal weight and 16.9 +/- 3.8, 75.5 +/- 25.5 and 51.1 +/- 18.9 min in obese weight, respectively. Also, no differences were observed in plasma clearance (3.89 +/- 0.58 in normal weight and 3.62 +/- 1.42 mL kg-1 min-1 obese weight). This study indicates that the pharmoacodynamics and pharmacokinetics of rocuronium are in female patients not altered by obesity.
Subject(s)
Androstanols/pharmacokinetics , Anesthesia , Neuromuscular Nondepolarizing Agents/pharmacokinetics , Obesity/metabolism , Adult , Androstanols/blood , Androstanols/pharmacology , Body Height , Body Mass Index , Body Weight , Female , Gynecologic Surgical Procedures , Half-Life , Humans , Neuromuscular Nondepolarizing Agents/blood , Neuromuscular Nondepolarizing Agents/pharmacology , Rocuronium , Skin Temperature/drug effects , Synaptic Transmission/drug effectsABSTRACT
We have assessed the effect of anaesthetic technique on intubating conditions after rocuronium 0.6 mg kg-1 in four groups (n = 25 each) of unpremedicated patients in whom anaesthesia was induced with either thiopentone 5 mg kg-1 or propofol 2.5 mg kg-1 alone, or supplemented with alfentanil 20 micrograms kg-1. Fifty control patients were anaesthetized with thiopentone followed by suxamethonium. Laryngoscopy was commenced at 45 s. Overall intubating conditions after rocuronium were similar to those after suxamethonium (good and excellent > or = 96%) only when alfentanil was part of the induction regimen. However, intubation time was similar in all five groups and averaged 55 (SD 3.2) s, and the tube could be passed through open vocal cords within 70 s. After rocuronium the response of the diaphragm to intubation was more pronounced in the two groups of patients not receiving alfentanil (P < 0.0001) and in patients anaesthetized using propofol with alfentanil (P < 0.01) than in the control group. Opioids (in doses equivalent to alfentanil 20 micrograms kg-1) constitute an integral part of an induction regimen containing rocuronium 0.6 mg kg-1, regardless of whether or not thiopentone or propofol is used, in order to achieve overall intubating conditions similar to those after suxamethonium.