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Biomedical subjects

B Dirks

Publications and source records attributed to B Dirks.

31 records · Page 2Linked to original sources
PubMed1992

Adrenaline: relationship between infusion rate, plasma concentration, metabolic and haemodynamic effects in volunteers.

The present study investigated the relationship between supraphysiological plasma concentrations of adrenaline and the resulting haemodynamic and metabolic effects. Adrenaline was administered at five infusion rates (0.01-0.2 micrograms kg-1 min-1) in an escalating sequence to eight volunteers. The arterial plasma concentration of adrenaline increased from 53 +/- 44 to 4349 +/- 818 ng litre-1 during the highest infusion rate. Typical haemodynamic responses, such as increase in blood pressure and heart rate, were seen. The plasma concentrations of glucose and lactate increased from 5.2 +/- 0.4 to 13.7 +/- 1.3 mmol litre-1 and from 0.9 +/- 0.3 to 4.7 +/- 2.6 mmol litre-1, respectively, during the highest infusion rate without a significant increase in insulin concentration. Non-esterified fatty acids increased from 379 +/- 97 to 1114 +/- 331 mumol litre-1 during the 0.06 microgram kg-1 min-1 infusion rate. Adrenaline had no selective haemodynamic effect. If similar metabolic effects occur in patients during treatment with adrenaline or other sympathomimetics, they may further increase breakdown of energy stores in a situation of increased catabolism, and impair utilization of parenteral nutrition.

Adult↗
PubMed1991

[In vitro drug interactions and their importance in anesthesiologic practice].

The potential for in vitro drug interactions is great in anaesthesiology because of routine intravenous comedication. When the drug is applied directly into (via) the injection port of the cannula most of these interactions are overlooked, whereas others show no visible signs. Chemical interactions depend on pH changes, formation of insoluble salts, oxidation and reduction, complex formation, or hydrolysis. Physical interactions are caused by changing of solvent system polarity, salting out, emulsion cracking or sorption. Solving the problem requires information (1) and precautions in respect of the mode of application (2). (1) Anaesthesiologists should know the most frequent mechanisms. Glucose infusions cannot be considered as safe carrier solutions for admixtures. Pharmacological databases should offer as much information as possible on incompatibility. (2) Injections into a separate line or lumen with a sodium chloride infusion are safe. Admixture is recommended only if compatibility is known.

Anesthesiology↗
PubMed1990

The role of alpha 1-adrenoceptors in adrenaline-induced hyperkalaemia.

The hyperkalaemic action of adrenaline was investigated in 44 anaesthetized domestic pigs. Plasma and epicardial concentrations of K+ were measured, in the latter case with an ion-selective electrode. Adrenaline 10 micrograms kg-1 caused a rapid increase in the plasma concentration of K+ from 4.2 to 5.9 mmol litre-1. The magnitude and the time course of epicardial concentration of K+ were similar. Alpha-adrenoceptor block with either phentolamine 5 mg kg-1 (non-selective block) or prazosin 0.1 mg kg-1 (selective alpha 1-adrenoceptor block) abolished the hyperkalaemic effect of adrenaline in the plasma and on the epicardium. The alpha 1-adrenoceptor agonist phenylephrine increased the K+ concentration, but the alpha 2-adrenoceptor agonist UK 14.304 did not cause any change in concentration. These results suggest that the hyperkalaemia induced by adrenaline occurs in the interstitial fluid of the myocardium and is mediated by alpha 1-adrenoceptors. These findings may be important in patients at risk of hyperkalaemia, with implications, for example, in the use of suxamethonium during induction of anaesthesia.

Adrenergic alpha-Agonists↗
PubMed1989

[Lidocaine levels in the plasma following peripheral or central venous administration during cardiopulmonary resuscitation. Results of an experimental animal study].

A review of the literature indicates that the intravenous bolus dose of lidocaine should be reduced in all conditions where cardiac output is diminished. During external cardiac compression the cardiac output is only approximately 20-40% of the normal resting value. Various routes of drug administration are currently used during CPR. The routine use of a central venous line is not recommended as a first-line procedure for resuscitation. This route of administration is favored by some authors, however, because it is presumed to result in a more rapid onset of drug action and higher peak concentrations of the drugs used. The aim of this study was to determine the aortic plasma concentration of lidocaine after central venous as compared to peripheral venous administration under the conditions of external cardiac compression. Twelve pigs were allocated to two groups of 6 animals each using random numbers. Ventricular fibrillation was induced by applying an alternating current via two needle electrodes placed subcutaneously. Cardiac arrest was allowed to continue for a period of 1 min before mechanical measures were applied. Cardiac massage was carried out using a pneumatic piston device set to a compression rate of 80/min. Sixty seconds after mechanical CPR had been initiated, a bolus of 1.5 mg/kg lidocaine was given to 6 animals via a central venous line. The remaining 6 animals were treated with the same dose given into a vein of the earlobe. The 2% lidocaine solution was diluted to 20 ml with physiological saline in all animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Caries, oral hygiene and periodontal disease in handicapped adults.

Caries, periodontal disease, oral hygiene and treatment needs were assessed in a group of handicapped adults. The study group comprised 199 individuals aged 17-64 yr, most of whom were mentally subnormal. The mean DMFT values ranged from 17.4 in the 17-24-yr-old age group to 26.9 in the 55-64-yr-old age group. Tooth loss increased rapidly with advancing age. In all age groups the F component was less than 20% and high numbers of untreated carious lesions were found. Of the group studied, 90% needed some conservative treatment. Oral hygiene was poor and a high prevalence of periodontal disease was found. Of the dentulous persons, 49% needed scaling and 34% complex periodontal treatment. The percentage of study group patients requiring dental treatment was very high, so that it can be concluded that dental care for the handicapped is insufficient. This situation must be improved and a suitable system for the delivery of preventive measures must be devised for this group of the population.

Adolescent↗
PubMed1984

[Comparison of the effects of piracetam and methohexital on cerebral energy metabolism].

Several authors suggest an influence of piracetam on brain energy metabolism. Therefore, we examined the effect of this drug on the levels of high-energy phosphates, glucose, some metabolites of glycolysis and free amino acids in the rat brain under normoxic, ischemic and postischemic conditions. In order to eliminate peripheral effects on the cerebral metabolism the isolated perfused rat brain was used as a model for this study. Methohexital was also administered for demonstrating protective effects on energy metabolism under the experimental conditions employed. The barbiturate, not piracetam, reduced the recovery time of the EEG after 1.5 or 2 min of ischemia. The depletion of energy reserves after the ischemic periods was diminished by methohexital but not by piracetam. The substrate and metabolite levels removed faster to the control levels under methohexital in the postischemic period whereas the piracetam treated brains did not differ from the controls. The subchronical treatment of rats in vivo with piracetam only caused a slightly smaller increase in the cerebral lactate concentration after anoxic periods. These results do not suggest an acute effect of piracetam on rat brain energy metabolism whereas the barbiturate methohexital may protect the brain against ischemic damage in a certain extent.

Amino Acids↗
PubMed1980

Fluorocarbon perfusion medium applied to the isolated rat brain.

In order to overcome the disadvantages of erythrocytes and albumin, a totally synthetic medium for the perfusion of the isolated rat brain was developed. the perfusion medium was based upon Krebs-Henseleit solution and contained in addition a fluorocarbon (FC 43) for oxygen transport and a polyol (Pluronic F 68) to furnish emulsifying and oncotic properties. The physico-chemical properties of this fluorocarbon perfusion medium allowed perfusion of an isolated rat brain to continue for more than 7 hr, while the medium could be stored as a stock emulsion for several months. The appropriate function of the isolated perfused rat brain is demonstrated by the EEG and by various substrates of the energy metabolism. The suitability of the fluorocarbon medium for perfusion of an isolated rat brain preparation is discussed.

Animals↗
PubMed1980

Studies on the linkage of energy metabolism and neuronal activity in the isolated perfused rat brain.

An isolated rat brain preparation was perfused using glucose-free (= aglycemic) media. The high-energy phosphates, substrates of the glycolytic pathway, free amino acids, acetylcholine as well as the intracellular distribution of hexokinase activity were determined in brain tissues. The EEG was evaluated visually. The levels of glycolytic substrates, glutamate, and glutamine in cortical tissue decreased after aglycemic perfusion whereas the asparte level increased and the GABA level remained unchanged. The high-energy phosphate content seemed to be unaffected for about 15 min of aglycemic perfusion and fell significantly after 20 min. The EEG of the isolated brain changed rapidly after starting aglycemic perfusion and became isoelectric after 12--15 min. Hyperglycemic perfusion (35 mmol glucose per liter perfusion medium) did not alter the energy metabolism of the isolated brain. The breakdown of cerebral energy metabolism and of EEG activity was postponed when thiopental was added to the perfusion medium. The soluble hexokinase activity measured in cortical tissue was reduced after aglycemic perfusion and was enhanced after thiopental. Hyperglycemic perfusion did not influence the intracellular hexokinase distribution. The acetylcholine level in the striatum of the isolated rat brain was significantly decreased by aglycemia and was increased in hypothalamus by thiopental. It was suggested that hexokinase bound to the mitochondrial membrane may play an important role in the relationship of energy metabolism and neuronal activity.

Acetylcholine↗