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Biomedical subjects

W Wilhelm

Publications and source records attributed to W Wilhelm.

88 records · Page 5Linked to original sources
PubMed1994

[Effects of propofol and fentanyl on the baroreceptor reflex in geriatric patients].

OBJECTIVE: Increasing age and anaesthetics diminish the baroreflex response to acute changes in blood pressure. This study was designed to investigate the effects of propofol and the combination of propofol with fentanyl on the baroreflex activity in geriatric patients. METHODS: Baroreflex sensitivity was studied by the method of Smyth et al. in 10 elderly (72 +/- 6 yrs) and in 10 younger (48 +/- 6 yrs) patients. Nitroprusside (depressor test) and phenylephrine (pressor test) were used to induce changes in blood pressure of 20 mmHg each to alter the stimulation of the baroreceptor sites. Anaesthesia was induced with propofol, 2 mg x kg-1 b.w.m, and maintained by a continuous infusion of 12 mg x kg-1 x h-1 for 10 min and thereafter with 6 mg x kg-1 x h-1. Then a bolus of fentanyl, 7 micrograms x kg-1 b.w. was injected. Haemodynamic parameters and baroreflex activity were measured in the awake state, 10 min after induction of anaesthesia and 10 min after the administration of fentanyl. Plasma propofol concentrations were determined by HPLC 10 min after induction of anaesthesia with propofol and 10 min after injection of fentanyl. The slope of the linear regression changes in RR-interval [ms] per changes in systolic pressure [mmHg] was used as an index of the baroreflex sensitivity. RESULTS: In the awake state the depressor slopes were significantly reduced by 60% in the elderly patients when compared to the younger patients. In both groups propofol decreased reflex sensitivity by 38% and 41% respectively; this effect was enhanced by the addition of fentanyl in the younger patients, while there was no further effect in the elderly. The pressor slopes did not change significantly in both groups neither with propofol nor with the combination of fentanyl, but again reflex response was significantly less in the elderly patients. CONCLUSION: Our data demonstrate that in geriatric patients the baroreflex control of heart rate already is attenuated in the awake state. Propofol produces a further reduction in reflex sensitivity to an acute decrease in blood pressure; this effect is more pronounced in elderly patients as compared to younger individuals. Acute changes in posture or circulating blood volume during propofol anaesthesia may result in greater cardiovascular instability in older patients due to the greater impairment of circulatory control mechanisms.

Adult↗
PubMed1993

[The hemodynamic effects of atracurium in geriatric patients during intravenous anesthesia using propofol].

OBJECTIVE: Neuromuscular blocking drugs may produce cardiovascular effects by virtue of drug-induced release of histamine or other vasoactive substances from circulating mast cells, effects at cardiac muscarinic receptors or effects at nicotinic receptors at autonomic ganglia. These haemodynamic reactions may be more pronounced in elderly patients, since cardiovascular compensating mechanisms are attenuated with advancing age. The present study was designed to investigate the cardiovascular effects of atracurium with special regard to the reactions in younger adults and in elderly patients. METHODS: 20 patients, ASA class I-II, who underwent a neurosurgical operation (posterior fossa surgery) were studied. The patients were divided into two groups including patients below (group A) and above (group B) 65 years of age. Anaesthesia was induced with propofol (2.5 mg/kg) and maintained with a Propofol/O2/N2O sequence. Under steady state conditions with propofol every patient received 0.5 mg/kg atracurium besylate. Haemodynamic parameters were recorded and plasma concentrations of epinephrine and norepinephrine were determined before (control) and 2, 5 and 10 minutes after the injection of the neuromuscular blocking agent. All measurements were performed before surgical stimulation in supine position. RESULTS: In the younger adults diastolic blood pressure and systemic vascular resistance decreased significantly 2 minutes after injection of atracurium and reached control level 5 minutes after application of the muscle relaxant. In the elderly patients peripheral vascular resistance decreased significantly after 5 minutes and returned to control 10 minutes after the application of atracurium. In both groups cardiac index, systolic and mean arterial pressure, central venous pressure and the parameters related to the pulmonary circulation were not affected. Plasma concentrations of epinephrine and norepinephrine remained essentially unchanged. Side effects due to a release of histamine such as facial or body blush or bronchial spasms were not noted. CONCLUSION: Since the results of the present study suggest that haemodynamic reactions in younger adults and in the elderly are rare, atracurium can be recommended for neuromuscular blockade in elderly patients under propofol anaesthesia.

Adult↗
PubMed1992

Influence of stepwise uncoupling and temporary anoxia on pancreatic enzyme secretion by isolated rat acini.

For special studies on pancreatic diseases a parameter is needed to record alterations of the cellular energy metabolism. In the in vitro model of isolated pancreatic acini, we investigated whether or not at standardized cholecystokinin stimulation the energy-consuming process of enzyme secretion can be used to monitor changes of the energy-supplying capacity. Rat pancreatic acini were isolated via collagenase digestion and characterized by basal and stimulated release of amylase and trypsin, oxygen uptake under resting and maximally uncoupled conditions and by their ability to accumulate actively rhodamine-6G, as a measure of the mitochondrial membrane potential. The stimulation of enzyme release did not find a measurable reflection in rhodamine-6G accumulation and in the respiratory rat. Stepwise uncoupling of oxidative phosphorylation by 2,4-dinitrophenol (DNP) and temporary anoxia were used to simulate disturbances of the pancreatic energy metabolism in vitro. With increasing DNP concentration the enzyme release was significantly reduced. While after 30 min anoxia the enzyme release still exceeded that of unstimulated control, after 60 min anoxia there was no further response to hormonal stimulation. At standardized stimulation and after suitable calibration the enzyme release by acini may be used to monitor alterations of the pancreatic energy metabolism in vitro.

2,4-Dinitrophenol↗
PubMed1991

Influence of anoxia, reoxygenation, and uncoupling on survival, respiration, and trypsin-inhibiting capacity of isolated pancreatic acinar cells.

In the pathogenesis of acute pancreatitis, the events and mechanisms increasing the digestibility of the pancreatic acinar cells are widely unknown. Therefore, the possible contribution of a disturbed energy supply (provoked by anoxia or partial uncoupling) to the induction of autodigestion was studied in experiments on acinar cells isolated from the pancreas. During incubation viability, respiration under normal and maximally stimulated conditions, and trypsin-inhibiting capacity (TIC) of these cells were determined. With increasing duration of anoxia, the portion of surviving cells was strongly diminished, and the number of cells with blebs and vesicularly transformed endoplasmic reticulum was increased. Although the endogenous respiration was not influenced up to 1.5 h of anoxia, 30 min of anoxia substantially decreased the capacity of oxidative energy production. The survival curves were characterized by a self-accelerating course of cell destruction. The alteration of the cellular energy metabolism found its reflection in the decreased TIC of the cells.

2,4-Dinitrophenol↗
PubMed1989

Effects of trypsin, chymotrypsin, and uncoupling on survival of isolated acinar cells from rat pancreas.

To improve the knowledge of the very complex pathogenesis of acute pancreatitis, separated exocrine pancreatic cells were used as an experimental tool. Intact acinar cells were isolated from rat pancreas and the time course of their damage was studied in the presence of increasing activities of trypsin, chymotrypsin and, after, stepwise uncoupling of oxidative phosphorylation, by 2,4-dinitrophenol (DNP). With an increasing degree of uncoupling the half-life period of cells incubated was remarkably reduced. Extracellular trypsin, present in activities comparable with the endogenous trypsinogen content, was not effective in cell killing. Only when the trypsin activity was drastically enhanced was the rate of cell destruction accelerated. Compared with chymotrypsin, isolated acinar cells revealed some resistance to extracellular trypsin. But when the energy production was altered by partial uncoupling the susceptibility of these cells toward the action of trypsin was increased and their life time was remarkably reduced. The potentiation of the effects of trypsin and uncoupling on cell viability demonstrates the contribution of an intact energy metabolism to the protective potential of acinar cells against further noxae.

2,4-Dinitrophenol↗
PubMed1988

The physical attractiveness of facially deformed patients before and after craniofacial surgery.

The present experiment investigated whether the physical attractiveness of craniofacially deformed children and adolescents could be improved by surgical procedures. Twenty patients between the ages of 5 months and 17 years were randomly selected from patient files. Patient diagnoses included facial clefts, hypertelorism, Treacher Collins syndrome, and craniofacial dysostosis (Crouzon's and Apert's syndromes). Rigorously standardized photographs of patients taken before and after surgery were shown to 40 "naive" raters ranging in age from 17 to 52 years. Raters analyzed the photographs with regard to global physical attractiveness. These ratings indicated that the patients' physical attractiveness was reliably (62 percent) improved following surgery. The results are discussed in light of recent evidence that untreated craniofacial patients may be at risk for psychosocial disorders and in terms of the growing evidence of the importance of physical appearance for the development of cognitive and social-emotional competence. In addition, a standardized assessment system is described that can be used to facilitate the compilation of actuarial data predicting surgical outcomes. Finally, the importance of empirically evaluating the effectiveness of surgical procedures and practitioners on a continuing basis is emphasized.

Adult↗
PubMed1987

Short-term inhibition of cardiac cellular autophagy by isoproterenol.

It is shown in the present study by means of quantitative electron microscopy that the volume fraction of autophagic vacuoles is significantly reduced to about half the control value within a short time interval (about 10 min) after low dose administration of isoproterenol. The data suggest that stimulation of cardiac work is accompanied by an immediate anticatabolic reaction which can be assumed to represent an early contribution to the adaptative increase in myocardial mass known to result from long-term stimulation of cardiac work.

Animals↗
PubMed1976

[Atypical vagal Wenckebach period in a high performance athlete].

A 27-year-old man, engaged in heavy physical training, exhibited sinusbradyarrhythmia with atrial abnormality and second degree av-block (atypical Wenckebach period). Since abnormal sinusrhythms was established with exercise and following parasympathetic blockade, this rhythm disorder was considered consequential exaggerated vagal tone. With the aid of His-bundle electrocardiography the block was localized in the av-node (AH).

Adult↗