PHARMACOKINETICS OF ALFENTANIL DURING AND AFTER A FIXED RATE INFUSION

Twenty-nine patients (age range 14–81 yr) undergoing orthopaedicsurgery received alfentanil 100 µg kg^–1 given astwo i.v. boluses followed by a fixed rate infusion of 1 µgkg^–1 min^–1 for 44–445 min. Additional 1-mgbolus doses of alfentanil were administered as required. Plasmasamples were assayed for alfentanil using radio-immunoassay.Pharmacokinetic parameters were estimated by a model-independentapproach and by curve-fitting. Regression analysis showed nostatistical relationship between T, CI or Vd and the durationof the infusion, total dose or body weight. We found no significantcorrelation between age and T of alfentanil for patients youngerthan 40 yr. For patients older than 40 yr, T increased linearlywith age. There was no significant decrease in Cl with age,although the lower values for CI (100–200 ml min^–1)were generally found in subjects older than 60 yr. The presentstudy demonstrated that a 100-µg kg^–1 loading doseand a 1-µg kg^–1 min^–1 infusion may be appropriatefor analgesia in general surgical procedures.     

INVASIVE V. NON-INVASIVE MEASUREMENT OF ARTERIAL PRESSURE: Comparison of Two Automatic Methods and Simultaneously Measured Direct Intra-Arterial Pressure

Two indirect arterial pressure monitors, the Finapres and theAccutorr, were investigated and compared with the direct measurementof intra-arterial pressure. Pressures in patients in a varietyof circulatory states were measured and analysed in relationto two types of random error: first, the "intra-individual standarderror" (within one session of measurement) and second, the "inter-individualstandard error" (between sessions). (This distinction is important,since in routine monitoring of arterial pressure one is usuallydealing with the first type of error only.) This study showedthat sudden changes in pressure were closely followed by theFinapres. A pressure reading of the Accutorr takes about 15–20s, meaning that, within this period, variations will not beobserved. The accuracy or reproducibility of each method, asexpressed in intra-individual variance, diminished in the orderIntra-Arterial-Line, Finapres, Accutorr. The inter-individualvariation decreased in the order Intra-Arterial-Line, Accutorr,Finapres. Most of the inter-individual variance of the Finapresis probably real because of the more peripheral position ofits cuff. A correlation between malfunctioning of the Finapresand vasoconstriction or hypothermia of the finger could notbe demonstrated.     

Comparison of etomidate and propofol for anaesthesia in microlaryngeal surgery

Propofol and etomidate were compared as hypnotics in total intravenous anaesthesia for microlaryngeal surgery combined with jet ventilation. Two groups of 15 patients were studied. In group 1, propofol 2.0 mg/kg was used for induction. For maintenance a continuous infusion of 12 mg/kg/hour was used for the first 10 minutes, followed by 9 mg/kg/hour for the next 10 minutes and 6 mg/kg/hour thereafter. In group 2, the induction dose of etomidate was 0.3 mg/kg followed by continuous infusion of 1.8 mg/kg/hour for 10 minutes, 1.5 mg/kg/hour for the next 10 minutes and 1.0 mg/kg/hour thereafter. Alfentanil was given for analgesia and suxamethonium for muscle relaxation. The propofol group showed better surgical conditions, more stable anaesthesia and better recovery according to the Steward score. Recovery times to opening eyes on command were comparable for both groups.     

SOME EFFECTS OF DIISOPROPYL PHENOL (ICI 35 868) ON THE PHARMACODYNAMICS OF ATRACURIUM AND VECURONIUM IN ANAESTHETIZED MAN

The effects of a bolus injection of diisopropyl phenol 2 mgkg–1 i.v. and an infusion (150 µg kg–1 min–1for 30 min and 75 µg kg–1 min–l thereafter)on the pharmacodynamics and dose-response curves of atracuriumand vecuronium were studied in 52 healthy (ASA I or II) patients.Under anaesthesia with diisopropyl phenol, the cumulative dose-responsecurves of both myoneural blocking drugs were shifted to theleft when compared with previously reported results. However,there was no clinically significant change in the pharmacodynamicsof either drug after the bolus injection of the blocking drug.Diisopropyl phenol 2 mg kg–1 i.v. administered duringsteady-state infusions of vecuronium and atracurium increasedthe depth of the constant neuromuscular blockade. When diisopropylphenol alone was given to four patients there was no changein the twitch height. These results show that diisopropyl phenol,given according to the regimen in this study, potentiates bothof the neuromuscular blockers studied but does not prolong theduration of action of either drug. During the infusion of diisopropylphenol, vecuronium was found to be five times more potent, tohave a more rapid onset time, and to be shorter acting thanan equipotent dose of atracurium. ^*Present address: Department of Anaesthesia, Royal Infirmary,Glasgow     

Anaesthesia for laparoscopy

This is a report about five anaesthetic techniques for laparoscopy. Propofol and etomidate were used for total intravenous anaesthesia. Propofol, etomidate and thiopentone were used as induction agents prior to inhalational anaesthesia with isoflurane and nitrous oxide. Fentanyl was used for analgesia. Induction with propofol and thiopentone was rapid. Etomidate induction was characterised by myoclonus. Maintenance was smooth with inhalational anaesthesia. Of the groups that received total intravenous anaesthesia, propofol provided stable anaesthesia but required extra bolus doses. Recovery was the most rapid following total intravenous anaesthesia with propofol. Postoperative side effects were much lower after propofol. No difference was observed between the groups with regard to changes in arterial blood pressure and heart rate.     

FACTORS AFFECTING MAGNITUDE AND TIME COURSE OF NEUROMUSCULAR BLOCK PRODUCED BY SUXAMETHONIUM

This study was designed to identify factors that significantlyalter the magnitude and duration of suxamethonium-induced neuromuscularblock in patients with an apparently normal genotype for pseudocholinesterase.One hundred and fifty-six adults (ages 18–65 yr) wereallocated to 13 subgroups. Patients in each subgroup receivedsuxamethonium 50–2000 ug kg^–1. The mechano-graphicresponse of the adductor pollicis brevis muscle to ulnar nervestimulation was recorded. The ED so was found to be 167 figkg^–1, EDX was 316 ng kg^–1 and ED₉₅ was 392 µgkg^–1. The duration of action (