Search PubMed⌕ Search

Biomedical subjects

C Meistelman

Publications and source records attributed to C Meistelman.

70 records · Page 4Linked to original sources
PubMed1987

Effects of increasing enflurane concentrations on intraocular pressure.

The effects of enflurane at various concentrations on intraocular pressure (IOP) were studied. In 15 healthy patients, intubated and mechanically ventilated, IOP was measured the day before surgery, after premedication and during anaesthesia, after administration of 0.5%, 1.0% or 1.5% enflurane. Enflurane in combination with general anaesthesia and controlled ventilation (PCO2 4.7-5.3 kPa) caused a significant decrease in IOP. The decrease was more marked (44%) with 1% enflurane than with 0.5% enflurane (21%). The change in IOP was comparable with 1.0% and 1.5% enflurane; however, systolic arterial pressure decreased more with enflurane 1.5%. Increasing the inspired concentration of enflurane from 1% to 1.5% did not appear to be associated with any further decrease in IOP.

Adult↗
PubMed1987

A comparison of alfentanil pharmacokinetics in children and adults.

The pharmacokinetics of alfentanil have been studied in eight children aged between 4 and 8 yr and five adults during general anesthesia. All patients were given 20 micrograms/kg alfentanil as an intravenous bolus injection. Plasma concentrations were measured at intervals up to 6 h by radioimmunoassay. Plasma protein binding was measured by equilibrium dialysis using tritiated alfentanil. The optimal pharmacokinetic model for alfentanil was an open two-compartment model. Total apparent volume of distribution (Vdss) was 457 +/- 160 ml/kg in adults and 163 +/- 110 ml/kg in children (P less than 0.01). When recalculated by surface area Vdss was still decreased in children (P less than 0.01). Plasma clearance (Cl) was similar in the two groups. Terminal elimination half-life was significantly shorter in children (40 +/- 9 min) than in adults (97 +/- 22 min; P less than 0.01). The shorter elimination half-life could be due to the smaller total apparent volume of distribution in children. Plasma protein binding was comparable between children and adults and could not explain the smaller volume of distribution in children. It is suggested that the smaller volume of distribution of alfentanil in children is a result of the decreased percentage of fat tissue in children.

Adult↗
PubMed1986

Clinical pharmacology of vecuronium in children. Studies during nitrous oxide and halothane in oxygen anaesthesia.

Forty-seven children (ASA I or II) were studied during nitrous oxide-oxygen, halothane anaesthesia. The dose-response curve for vecuronium was determined after the injection of a single bolus (40, 55 or 70 micrograms kg-1) to 33 patients. The ED50 and ED95 were 31 and 64 micrograms kg-1 respectively. Fourteen children received a larger dose (100 micrograms kg-1); good intubating conditions were obtained in all of these within 2 min. After a single bolus (100 micrograms kg-1) the duration of action was 36.5 min and the recovery index was 9.3 min. In patients who received small maintenance doses (25 micrograms kg-1) after a single bolus (100 micrograms kg-1) the recovery index after the last maintenance dose was not increased. There were no significant changes in heart rate or arterial pressure. In children, vecuronium has a short duration of action and lacks cumulative or cardiovascular side affects.

Anesthesia, Inhalation↗
PubMed1986

Disposition and urinary excretion of vecuronium bromide in anesthetized patients with normal renal function or renal failure.

The effect and plasma concentrations of vecuronium bromide were measured in normal patients after an intravenous dose of 50, 100, or 150 micrograms/kg and in patients with renal failure after 50 or 100 micrograms/kg. Urinary excretion of vecuronium was studied in normal patients after the 150 micrograms/kg dose. Pharmacokinetic parameters of patients with or without renal failure were similar. No metabolites of vecuronium were found in the plasma. Twenty percent of vecuronium was excreted unchanged in the urine; 5% as the 3-hydroxy derivative. No other metabolites of vecuronium were found in the urine. Increasing doses of vecuronium shortened the onset, but prolonged the duration of action and the recovery rate, to a similar extent in patients with or without renal failure. It was concluded that the disposition of vecuronium was best described by a three compartment model. Both the disposition and the effect of vecuronium are only marginally disturbed by renal failure.

Adult↗
PubMed1986

Pharmacokinetics and pharmacodynamics of vecuronium and pancuronium in anesthetized children.

The pharmacokinetics and pharmacodynamics of vecuronium and pancuronium were determined in 12 children (3-6 yr) undergoing minor surgery under 60% nitrous oxide, 1 MAC halothane anesthesia. When the level of anesthesia and the electromyograph (EMG) recording of the adductor pollicis were stable, an intravenous bolus of vecuronium (100 micrograms/kg) or pancuronium (100 micrograms/kg) was administered. Plasma concentrations of the two muscle relaxants were determined for 6 hr after the administration by means of a fluorimetric assay followed by a thin layer chromatography. Plasma concentrations of vecuronium and pancuronium declined biexponentially in children and no metabolites could be detected in plasma. The elimination half-lives of vecuronium and pancuronium did not differ significantly. The volume of distribution at steady state (Vdss) was greater (P less than 0.05) after vecuronium (320 +/- 181 ml/kg; mean +/- SD) than after pancuronium (203 +/- 36 ml/kg). Plasma clearance of vecuronium (2.8 +/- 0.9 ml X min-1 X kg-1) was greater than that of pancuronium (1.7 +/- 0.2 ml X min-1 X kg-1; P less than 0.05). Plasma concentrations measured at 10%, 50%, or 90% recovery of the EMG response did not differ significantly for vecuronium and pancuronium. Thus the shorter duration of action of vecuronium is probably due to its greater apparent volume of distribution, as well as to its higher plasma clearance. Thus although the elimination half-lives are comparable, the plasma disappearance of vecuronium is more rapid than that of pancuronium.

Anesthesia, General↗
PubMed1986

Pharmacology of vecuronium in patients with end-stage renal failure.

Vecuronium was administered as an intravenous bolus (50 micrograms kg-1) to 10 normal and 10 anephric patients. The elimination half-life was 50.7 +/- 20.3 min in normal patients and 67.826.3 min in anephric patients. The plasma clearance was 3.6 +/- 1.5 ml min-1 for normal patients and 4.5 +/- 2.6 ml min-1 kg-1 for anephric patients. Only the volume of the second compartment was statistically increased (+90%, P less than 0.05) in anephric patients. The duration of action in normal patients (25.3 +/- 9.8 min) was comparable to the duration of action in patients with renal failure (32.8 +/- 10.7 min), but the recovery index was prolonged (+45%, P less than 0.05) in anephric patients.

Adult↗
PubMed1985

[Experimental pharmacology of atracurium dibesylate].

Atracurium dibesylate is a new non depolarizing muscle relaxant, metabolized by a non enzymic pathway, the Hofmann elimination. The potency of atracurium in animals was similar to d-tubocurarine and six times less than that of pancuronium. In the cat, the ED50 was 130 micrograms . kg-1; an intravenous dose of 250 micrograms . kg-1 atracurium was sufficient to cause complete neuromuscular block; its duration was 29 min. Single twitch block was readily antagonized by neostigmine 50-100 micrograms . kg-1 or edrophonium 200 micrograms . kg-1. Halothane potentiated the block given by atracurium. Dose ratio for 50% vagal block (ED50) and 50% neuromuscular block was 24; atracurium had weak ganglioplegic effects. 2,000 micrograms . kg-1 atracurium (eight times the neuromuscular blocking dose) reduced mean aortic pressure, heart rate, cardiac output and peripheral resistance. Such effects could be prevented by giving histamine receptor blockers prior to injecting atracurium.

Animals↗
PubMed1985

[Determination of the dose-response curve for atracurium dibesylate in the anesthetized adult].

The mechanical response of the adductor pollicis to a 0.15 Hz stimulation of the ulnar nerve was studied in 35 unpremedicated adult patients (mean age 38 yr) under general anaesthesia using thiopentone, fentanyl and a N2O/O2 mixture under mechanical ventilation. PaCO2, pH, K, Ca, Mg plasma levels and temperature were in the normal range. Each patient received a single bolus of atracurium dibesylate: 0.10 mg . kg-1 (n = 11), 0.15 mg . kg-1 (n = 10), 0.20 mg . kg-1 (n = 11) or 0.30 mg . kg-1 (n = 4). The dose-response curve was constructed using the log-probit method for 0.10, 0.15, 0.20 mg . kg-1 doses, giving neuromuscular blocks greater than 0% and less than 0.20 mg . kg-1. The 0.20 mg . kg-1 dose had an onset time of 6.1 +/- 0.6 min, duration 0-90% of 34.3 +/- 3.2 min and a recovery index 25-75% of 10.9 +/- 1.0 min. The 0.3 mg . kg-1 dose resulted in onset time of 4.7 +/- 1.3 min, duration of 39.9 +/- 3.7 min and a recovery index of 10.7 +/- 1.8 min. Thus atracurium dibesylate seemed to be an agent of intermediate potency. Onset time was approximately the same as that for other non-depolarizing neuromuscular blocking drugs, but duration of action and recovery index were quite shorter, except for vecuronium bromide.

Adult↗