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Biomedical subjects

B Biber

Publications and source records attributed to B Biber.

At least 109 records · Page 6Linked to original sources
PubMed1982

Anaesthesia and cardiovascular regulation.

Cardiovascular homeostasis is dependent on the efficient performance of the effector organs, i.e. the vascular smooth muscle and the heart. Besides inherent activity and local control mechanisms, these effector organs are regulated by circulatory control centres within the central nervous system, which in turn receives information from receptors inside and outside the cardiovascular system. All these components of the circulatory systems, i.e. receptors, afferent and efferent pathways, control centres and effector organs, are possible sites for interactions by anaesthetics. Since different anaesthetics have different potencies and special predilections, there are a large variety of interaction patterns, as is discussed in the paper. Another way of evaluating circulatory effects of drugs used in anaesthesia is to analyse how these drugs may modify circulatory reflexes associated with surgery and trauma. For example, pain, hypoxia and/or hypovolaemia may evoke circulatory adjustments which correspond to and are functionally related to, from experimental physiology, well-known reflex patterns such as the somatosympathetic reflex, the chemoreceptor reflex and the baroreceptor reflex. These reflex adjustments are liable to modification by anaesthetics, as exemplified in the paper. Due to the complexity of circulatory control and the varying effects of different anaesthetic agents, it is difficult to draw general conclusions. It can, however, be stated that most general anaesthetics depress cardiovascular reflexes in proportion to the depth of anaesthesia, and that suprabulbar centres are more easily depressed than bulbar ones. Opiates seem to have a specific inhibitory effect on circulatory adjustments induced by noxious stimuli. Transmission in efferent and afferent pathways is liable to modification by local anaesthetics, ganglionic blockers or alpha- and beta-receptor antagonists.

Anesthesia↗
PubMed1982

Beta-receptor blocker withdrawal. A preoperative problem in general surgery?

A prospective randomized study was performed in 91 patients scheduled for general surgery on 99 occasions. The patients were chronically (greater than 3 months) treated with beta-receptor blockers because of ischaemic heart disease and/or hypertension and the beta-receptor blockade was either gradually withdrawn (n = 51) during 4 days preoperatively or continued until surgery (n = 48). The effects on arterial blood pressure (BP), heart rate (HR) and rate-pressure product (RPP) at rest and the incidence of chest pain during daily activities were registered. A withdrawal of the beta-receptor blockade was associated with increases of HR (in eight patients greater than 30 beats min-1) and RPP and in patients treated for hypertension there were also increases of systolic and diastolic BP (in five patients greater than or equal to 30/15 mmHg). Patients who continued the beta-receptor blockade until surgery showed no changes. Nine out of 23 patients with a previous history of ischaemic heart disease had an increase of chest pain after withdrawal of the beta-receptor blockers, whereas none of the corresponding 25 patients who continued the therapy suffered from an increased chest pain. Due to the severity of symptoms after beta-receptor blocker withdrawal, surgery had to be postponed in 4 patients. The observations suggest that a 4-day preoperative withdrawal of long-term beta-receptor blockade is potentially hazardous in ischaemic and/or hypertensive patients.

Adrenergic beta-Antagonists↗
PubMed1982

Beta-receptor blockade and spinal anaesthesia. Withdrawal versus continuation of long-term therapy.

A prospective study was performed in 43 men scheduled for transurethral resections under spinal anaesthesia. All patients were on chronic beta-receptor blockade because of hypertension and/or ischaemic heart disease. The patients were randomly subjected to either a gradual preoperative withdrawal or a continuation of the beta-receptor blockade. Haemodynamics were measured non-invasively. Spinal anaesthesia was performed and an i.v. injection of atropine given. The patients were then placed in a lithotomy position. Mean anaesthetic level included T6. After beta-receptor blocker withdrawal consistently elevated heart rates, a high incidence of arhythmias, angina pectoris and postoperative ST-T changes indicating myocardial ischaemia were seen. These changes were not seen in patients with continued beta-receptor blockade. Withdrawal of beta-receptor blockers was also associated with an increased total peripheral vascular resistance in connection with spinal anaesthesia. These results suggest that patients on long-term beta-receptor blockade should continue the therapy during and after spinal anaesthesia.

Adrenergic beta-Antagonists↗
PubMed1982

Bupivacaine for intercostal nerve blockade in patients on long-term beta-receptor blocking therapy.

Possible cardiovascular side effects of a local anaesthetic in patients on long-term beta-receptor blocking therapy were studied in 26 patients given postoperative intercostal nerve blockades (ICB) with 18-28 ml of plain bupivacaine 0.5% (1.30-1.82 mg kg-1). The patients had a history of hypertension and/or ischaemic heart disease and were scheduled for gall bladder surgery. Thirteen patients were randomized to a gradual preoperative withdrawal of the beta-receptor blockers and the other 13 continued the beta-receptor blockade until surgery. Cardiovascular changes were measured noninvasively and 11 patients were also monitored with pulmonary artery catheters. Blood pressure and heart rate (HR) were stable in all patients although those in whom the beta-receptor blockade was withdrawn had the highest HR and most frequent arrhythmias both before and after ICB. The ICB was associated with a decrease in the overall postoperative arrhythmia incidence, but seemed most efficient (P less than 0.02) concerning the ventricular arrhythmias in the beta-receptor-blocked patients (even including idionodal rhythm). The bupivacaine blood levels did not modify other cardiovascular changes except in one beta-receptor-blocked patient with cardiac failure in whom signs of a slight transient cardiodepression were observed. It is concluded that bupivacaine does not negatively affect cardiovascular stability in long-term beta-receptor-blocked patients. In the presence of cardiac failure, however, an additive cardiodepression may be elicited.

Adrenergic beta-Antagonists↗
PubMed1982

Measurement of stroke volume with impedance cardiography.

Simultaneous determination of stroke volume with impedance cardiography and the dye dilution technique was compared in 11 healthy men before and after exercise. The correlation coefficient for all measurements was 0.82. Mean stroke volume determined by impedance cardiography was significantly (P less than 0.001) lower than mean stroke volume calculated by the dye dilution technique. However, there was no significant difference in the mean change in stroke volume determined by the two techniques during serial measurements. The reproducibility of single impedance-determined stroke volumes (6.9 ml) was not significantly different from single values obtained by dye dilution (7.3 ml). Impedance cardiography was found to be a safe, reliable, non-invasive method for the measurement of changes in stroke volume in healthy individuals before and after exercise. At present, direct estimation of absolute values of stroke volume is not recommended using impedance cardiography. Calibration of the impedance technique against other established techniques in a given application is necessary.

Adult↗
PubMed1982

The continuous thermodilution method for measuring high blood flows.

The continuous thermodilution method for the measurement of blood flow from 300 to 1500 ml/min was evaluated in vitro and in vivo. In vitro experiments indicated that thermotransport within the catheter, causing a temperature measurement error, can occur. Flow model measurements were used for consequent modification of the original thermodilution formula for calculation of flow. In the in vivo investigations the thermodilution and electromagnetic methods were compared for measurement of pig portal blood flow. Using the modified formula for the flow calculations, good agreement was found between the two methods (r = 0.958). For the continuous thermodilution method in vivo the standard deviation of a single measurement was 19 ml/min and the coefficient of variation 1.6%.

Animals↗
PubMed1981

Hemodynamic consequences of defence area stimulation and afferent somatic nerve stimulation during fentanyl-nitrous oxide anesthesia. Modifying effects of droperidol.

Stimulation of the hypothalamic defence area and activation of somatic afferents in combination with carotid baroreceptor unloading was performed in cats anesthetized with fentanyl-nitrous oxide in order to investigate the circulatory consequences in terms of regional blood flow changes. These stimulation procedures, suggested to mimic activation of central neurogenic cardiovascular control mechanisms caused by anesthesia and surgical stress, were found to induce pronounced reductions in intestinal and renal blood flow as well as in diuresis. However, administration of droperidol markedly diminished the renal vasoconstriction as well as the reduction in diuresis in the dose range 0.025--0.10 mg/kg b.w. Doses of 0.15--0.25 mg/kg b.w. virtually abolished any stimulation-induced increase in renal vascular resistance, whether elicited through activation of the defence area or somatic afferents. This dose also partly blocked the neurogenic increment of intestinal vascular resistance.

Animals↗