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Biomedical subjects

D G Selby

Publications and source records attributed to D G Selby.

9 recordsLinked to original sources
PubMed1990

Cardiovascular effects of propofol and of thiopentone anaesthesia in the sheep.

We have examined the effects on the cardiovascular system and on regional blood flow of propofol and thiopentone when administered with IPPV (FIO2 0.4). A longitudinal study design was used in which 16 studies were performed in eight sheep for 30 min before, during the last 30 min of 70 min anaesthesia, and for 6 h after anaesthesia. During anaesthesia with propofol and thiopentone, mean total body oxygen consumption decreased, respectively, by 47% (P less than 0.001) and 24% (P less than 0.01) of pre-anaesthesia baseline values, mean heart rate increased by approximately 50% (P less than 0.05) with both agents, mean arterial pressures increased by approximately 50% (P less than 0.05) with both agents and the mean cardiac output was unaltered with propofol anaesthesia but was decreased by 20% (P less than 0.05) with thiopentone anaesthesia. The changes in arterial pressure and heart rate were unexpected and may have been a result of a species-specific effect. Mean hepatic blood flow decreased consistently by a mean of 17% (P less than 0.01) during propofol anaesthesia, and inconsistently during thiopentone anaesthesia so that it was not significantly different from baseline values. Mean renal blood flow decreased during propofol anaesthesia by 7% (P less than 0.05) and by 27% (P less than 0.001) during thiopentone anaesthesia. Whereas most variables returned to baseline values within 2 h after propofol anaesthesia, this took 5 h after thiopentone anaesthesia.

Anesthesia, Intravenous↗
PubMed1990

Effects of propofol and of thiopentone anaesthesia on the renal clearance of cefoxitin in the sheep.

We have examined the renal extraction ratios and clearances of cefoxitin in three groups of adult merino ewes. One group (n = 3) was studied for 12 h without perturbation; these were designated control studies. The other two groups (n = 4 each) were studied before (baseline values), during and after the induction and 70-min maintenance of anaesthesia with propofol or thiopentone. In the control studies, mean renal extraction ratio and clearance for cefoxitin were, respectively, 0.67-0.92 and 0.66-0.91 litre min-1 and were consistent throughout the entire study period in individual animals. Comparable values were obtained as baseline values in the anaesthesia groups. Compared with individual baseline values, blood concentrations of cefoxitin doubled during anaesthesia with each agent. At the same time, renal extraction ratio and clearance for cefoxitin each decreased significantly to about 50-60% of their control values. Recovery to control values of arterial blood concentrations and renal extraction ratio of cefoxitin took at least 5 h, but recovery of renal clearance was more rapid. The results indicate that renal elimination of an organic anion such as cefoxitin may be affected by changes in renal blood flow and in renal function produced by propofol and thiopentone; these effects may last for several hours after recovery of renal blood flow.

Anesthesia, Intravenous↗
PubMed1990

Effects of propofol and of thiopentone anaesthesia on the regional kinetics of pethidine in the sheep.

We have examined the extraction ratios, net fluxes and clearances of pethidine by the liver, kidneys and hindquarters in sheep before, during and after continuous anaesthesia (70 min) with propofol or thiopentone. Before anaesthesia, the overall mean respective regional pethidine extraction ratios were 0.98 (SD 0.01), 0.20 (0.06) and 0.44 (0.13), the corresponding net fluxes were 47 (7), 5 (2) and 20 (10)% dose min-1 and the clearances 1.44 (0.22), 0.17 (0.07) and 0.80 (0.39) litre min-1. During propofol anaesthesia, arterial blood concentrations of pethidine approximately doubled (P less than 0.05), mean pethidine hepatic extraction ratio was unchanged, flux was increased to 145 (20)% and clearance decreased to 79 (10)% (P less than 0.05) of baseline values; mean pethidine renal extraction ratio, flux and clearance were 73 (34), 112 (43) and 69 (31)% of baseline values; mean hindquarter pethidine extraction ratio decreased to 65 (25)% (P less than 0.05) of baseline values. During thiopentone anaesthesia, arterial blood concentrations of pethidine approximately doubled (P less than 0.01), mean pethidine hepatic extraction ratio was 97 (2)% of baseline values and flux and clearance were unchanged, mean pethidine renal extraction ratios, flux and clearance decreased to 37 (21), 54 (18) and 27 (19)% (all P less than 0.05) of baseline values and mean pethidine hindquarter extraction ratio was 81 (20)% of baseline values. In spite of only modest changes in hepatic and renal blood flow during anaesthesia, blood concentrations of pethidine doubled and pethidine kinetics were disturbed for several hours after anaesthesia. Overall, however, the changes were of smaller magnitude and shorter duration than those that have been described for anaesthesia with the volatile anaesthetic agents.

Anesthesia, Intravenous↗
PubMed1989

Propofol: assay and regional mass balance in the sheep.

1. Pharmacokinetic data for propofol, a new intravenous anaesthetic agent, indicate that there may be extensive extrahepatic clearance. This was investigated during intravenous infusions of propofol in adult merino ewes with chronic intravascular cannulae using a newly developed simple and rapid assay for propofol in blood and other biological samples. 2. The assay was based on organic solvent extraction of pH 4.5 buffered blood, urine or tissue homogenate, followed by reverse-phase h.p.l.c. with fluorescence detection. 3. A mean total body clearance of propofol of 3.15 l/min, (SD 0.87 l/min; n = 8) was found, consistent with a high hepatic extraction ratio (overall mean 0.87, SD 0.19; n = 8) and clearance (overall mean 1.12, SD 0.25 l/min; n = 7). The difference between total and hepatic clearances consisted principally of pulmonary clearance, but its extent was variable. 4. Other regional pharmacokinetic data were consistent with propofol distribution into muscle and brain tissues and propofol 'production' by the kidney, probably from a propofol metabolite formed elsewhere. 5. If these data are confirmed in humans then clinical pharmacokinetic data so far derived from peripheral venous blood sampling will require re-evaluation.

Animals↗
PubMed1989

ACE inhibitors.

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Adult↗
PubMed1987

An evaluation of five carbon dioxide analysers for use in the operating theatre and intensive care unit.

Five commercially available carbon dioxide analysers were assessed with respect to accuracy, response time, stability, the effect of water vapour and the effect of rebreathing. Two side-stream sampling analysers (Datex Normocap and Engstrom Eliza) and one main-stream sampling analyser (Hewlett-Packard Capnoshot) were found to be satisfactory for use both in the operating theatre and intensive care unit. The Instrumentation Laboratory (IL) 200, a side-stream monitor, performed satisfactorily but neither it nor the Siemens Sirecust 404, a main-stream monitor, has the facility to compensate for the presence of nitrous oxide. The Siemens analyser, in the form tested, could not be recommended for clinical use, as it was less accurate than the other monitors, could not detect rebreathing, and was subject to fluctuations when used with gas mixtures saturated with water vapour.

Anesthesiology↗