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Biomedical subjects

J F Coetzee

Publications and source records attributed to J F Coetzee.

10 recordsLinked to original sources
PubMed2002

Fresh gas flow is not the only determinant of volatile agent consumption: a multi-centre study of low-flow anaesthesia.

METHODS: Seven academic centres studied 302 patients, using desflurane, enflurane, halothane, or isoflurane using circle-systems and Dräger Julian anaesthetic machines, with fresh gas flows (V(F)) of 3, 1, and 0.5 litre min(-1). Volatile agent partial pressures in the breathing system were recorded and agent consumptions measured by weighing. RESULTS: At these flows, desflurane consumption depended on V(F). In contrast, halothane consumption was not influenced by V(F). Isoflurane and enflurane showed differences in consumption between flows of 0.5 and 3 litre min(-1). Stepwise linear regression suggested that besides V(F), other factors influenced consumption of the more soluble agents (sex, age, weight, height, altitude, and temperature). The partial pressure ratios were independent of V(F) for desflurane (end-tidal to fresh gas=0.8), but the ratios of the more soluble agents varied with V(F) (end-tidal to fresh gas=0.3-0.7). CONCLUSIONS: At V(F) that involves significant re-breathing, consumption of soluble agents depends only partially on V(F). These results can be explained using Mapleson's hydraulic analogue model.

Adolescent↗
PubMed2000

Reduction of postischemic contractile dysfunction of the isolated rat heart by sevoflurane: comparison with halothane.

Our aims were to evaluate the effect of sevoflurane on postcardioplegic functional recovery of the isolated rat heart including the role of the adenosine triphosphate regulated potassium (K(ATP)) channels and to compare the cardioprotective effects of equipotent concentrations of halothane and sevoflurane. Isolated perfused rat hearts were subjected to 45 or 60 min normothermic cardioplegic arrest and 30 min reperfusion. Sevoflurane (0.9% and 1. 7%), halothane (0.4% and 0.8%), or sevoflurane (0.9%) plus glibenclamide (10 microM) (a K(ATP) channel blocker) were administered at different time intervals. Measurements of mechanical activity were made before and after arrest. Function during reperfusion after cardioplegic arrest was significantly depressed in both untreated and treated hearts. However, sevoflurane administered both before and after arrest, or before only, significantly improved functional recovery after 45 min of cardioplegia. This protective effect was abolished by simultaneous administration of glibenclamide, suggesting a role of the K(ATP) channel. Sevoflurane was as effective as halothane in improving postcardioplegic functional performance. After 45 min of arrest, hearts exposed to either anesthetic at both concentrations had a significantly higher work performance on discontinuation of their administration than untreated controls. After 60 min of arrest, neither anesthetic elicited protection.

Adenine Nucleotides↗
PubMed1998

Tramadol or morphine administered during operation: a study of immediate postoperative effects after abdominal hysterectomy.

Tramadol may cause awareness and EEG activation during anaesthesia. We compared tramadol with morphine, administered during wound-closure, surmising that tramadol may cause earlier awakening, more rapid recovery, less respiratory depression and equivalent pain relief. Forty patients received nitrous oxide-enflurane for abdominal surgery. At wound closure, patients received tramadol 3 mg kg-1 or morphine 0.2 mg kg-1 and end-tidal enflurane concentrations were maintained at 0.5 kPa until skin closure, whereupon anaesthesia was discontinued. Times to spontaneous respiration, awakening and orientation were similar in the two groups, as were blood-gas tensions, ventilatory frequency, pain scores and incidence of nausea. Half of each group required supplementary analgesia during their 90-min stay in the recovery room. P-deletion counts improved more rapidly in the tramadol group. This study confirms previous reports that tramadol did not antagonize the hypnotic effects of volatile anaesthetics. Tramadol, administered during operation, was as effective as morphine in providing postoperative analgesia while permitting more rapid psychomotor recovery.

Adult↗
PubMed1996

Effect of tramadol on depth of anaesthesia.

We have studied 51 patients who were anaesthetized with propofol and suxamethonium followed by 0.7% isoflurane and 66% nitrous oxide in oxygen to see if tramadol caused lightening of anaesthesia. A two-channel EEG was recorded and music was played via headphones. Two groups received tramadol 200 and 100 mg i.v. and the third group received saline. Tramadol caused significant, dose-dependent activation of the EEG, evidenced by increased frequencies and decreased amplitudes, but these changes were small and probably unimportant. Derived EEG variables did not approach values known to be associated with near-awakening during isoflurane anaesthesia. No patient moved on skin incision and there were no incidences of free recall.

Adolescent↗
PubMed1996

Pharmacokinetic behaviour and cardiovascular effects of intravenously administered hypoxoside and rooperol.

This study concerns the pharmacokinetic behaviour and cardiovascular effects of rapid infusions of hypoxoside (CAS 83643-94-1) and rooperol (CAS 83644-00-2) in anaesthetised Chacma baboons. Institutional approval was obtained and animal care conformed to international guidelines. Hypoxoside (500 mg) and rooperol (240 mg) dissolved in isotonic saline were infused during 15 min. Concentration-time data from high performance liquid chromatography of arterial blood samples were subjected to non-linear curve-fitting to obtain two-compartment mammillary pharmacokinetic models. Mean values were: [Table: see text] Hypoxoside was eliminated without significant metabolite formation and it revealed no cardiovascular effects. Rooperol was metabolized rapidly with formation of nine metabolites of which the major three were the diglucuronide, disulphate and mixed glucuronide sulphate. Rooperol caused moderate, transient increased cardiac output, stroke volume and vascular pressures without increased heart rate or filling pressures, suggestive of increased myocardial contractility probably allied to its catechol structure.

Alkynes↗
PubMed1995

Pharmacokinetic model selection for target controlled infusions of propofol. Assessment of three parameter sets.

BACKGROUND: Computer-assisted target controlled infusions (TCI) result in prediction errors that are influenced by pharmacokinetic variability among and within patients. It is uncertain whether the selection of a propofol pharmacokinetic parameter set significantly influences drug concentrations and clinical acceptability. METHODS: Thirty patients received similar propofol TCI regimens after being randomly allocated to one of three parameter sets. Arterial and venous concentrations were measured and prediction errors calculated from pooled and intrasubject data. RESULTS: Arterial propofol concentrations in the Dyck group revealed greater bias (mean 43%) than did those in the Marsh (-1%) and Tackley (-3%) groups. The Dyck group also showed greater inaccuracy (mean:47%) than the Marsh (29%) and Tackley (24%) groups. There was little tendency for measured concentrations to vary from targeted values over time (divergence). Variability about an observed mean in individual patients (wobble) was low. Venous propofol concentrations were initially much less than arterial concentrations, but this difference decreased over time. CONCLUSIONS: Although it may be preferable to administer propofol TCI by using a locally derived parameter set, it is acceptable to use a model from elsewhere. The Marsh and Tackley models produced equally good performance and are appropriate for propofol TCI within the range of 3-6 micrograms/ml. The Dyck model was less accurate at maintaining anesthetic concentrations, possibly because it was derived from low concentrations. Concentrations in blood, the most sensitive indicators of performance, demonstrated differences among the parameter sets. Clinically, TCI worked well, and by clinical criteria, the choice of pharmacokinetic model did not appear to make a difference.

Adult↗
PubMed1991

Intra-ocular concentration-time relationships of subconjunctivally administered gentamicin.

Eighty-nine patients scheduled for cataract removal or lens implantation were divided randomly into three groups. Each received 5, 10 or 20 mg gentamicin subconjunctivally at times varying between 0.2 and 19 hours pre-operatively. At surgery a sample of aqueous humour was obtained and analysed for gentamicin concentration. The data for each group were subjected to non-linear regression analysis to fit an open one-compartment pharmacokinetic model with first-order kinetics. A statistically acceptable fit was obtained. The average values of the pharmacokinetic parameters obtained from the single doses were used to simulate multiple-dose kinetics. The average target intra-ocular gentamicin concentrations and dosage interval were specified in the computer program, which subsequently allowed calculation of the dose required. This allowed the construction of a simple linear nomogram that can be used to read off the dose needed for handling specific clinical situations.

Aged↗