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Biomedical subjects

C Borst

Publications and source records attributed to C Borst.

At least 127 records · Page 7Linked to original sources
PubMed1987

Biocompatibility of hemodialysis using cuprophane membranes.

In a controlled study of the influence of hemodialysis on hemodynamics, complement system, leucocyte- and thrombocyte concentration was studied in two groups of five non-uremic dogs each. During the initial 30 min of dialysis with the commonly used cuprophane membrane, a transient but significant decrease of the mean aortic pressure and cardiac output occurred while simultaneously heart rate and systemic vascular resistance decreased. Thrombocyte concentration decreased significantly during the initial 60 min of dialysis due to sequestration in the dialyzer. Transient leucopenia due to pulmonary leucostasis occurred without decrease of the arterial oxygen tension. The simultaneous occurrence and transient character of the hemodynamic changes, leucopenia and thrombocytopenia suggest a relationship between these phenomena. These results indicate that the biocompatibility of cuprophane dialysis membranes is of importance not only with regard to changes in the leucocyte- and thrombocyte-count but also with regard to hemodynamic changes.

Animals↗
PubMed1986

Biocompatibility of haemoperfusion.

To evaluate the influence of haemoperfusion on haemodynamics, complement system, leucocyte and thrombocyte concentration, a controlled study was performed in three groups of five dogs each. During the first 30 min of haemoperfusion with columns containing cellulose-coated activated charcoal, a significant decrease of mean aortic pressure, cardiac output and stroke volume was observed, while heart rate and total systemic resistance decreased. A comparable phenomenon, although to a much lesser extent, was observed during perfusion using columns containing polystyrene resin. Perfusion with columns containing cellulose-coated activated charcoal caused a significant decrease in total haemolytic complement, indicating activation of the complement system. A significant decrease in the leucocyte and thrombocyte concentration due to sequestration of granulocytes and thrombocytes in the columns was observed during the first 30 min of perfusion in both groups. Pulmonary leucostasis, without decrease of arterial oxygen tension, occurred during perfusion with columns containing cellulose-coated activated charcoal. Both the simultaneous occurrence and the transient character of the haemodynamic changes, complement activation and sequestration of granulocytes and thrombocytes in the perfusion column suggest a relationship between these various changes. The results stress the importance of close monitoring of the haemodynamic parameters of the intoxicated patient, particularly during the early phase of haemoperfusion.

Animals↗
PubMed1986

Electrical catheter ablation in the left and right ventricular wall in dogs: relation between delivered energy and histopathologic changes.

Electrical catheter ablation of arrhythmogenic sites is now being used for the treatment of ventricular tachycardias. However, the extent and type of the ablation lesion in relation to energy level are controversial and not well known. In 10 beagles, single cathodal shocks of 30 (4 dogs), 80 (2 dogs) or 250 J (4 dogs) were delivered to the endocardial ventricular wall (5 dogs left ventricular, 5 dogs right ventricular). One week after ablation the dogs were killed for histopathologic examination. In the left ventricular wall, ablation lesion volumes calculated from measured extensions in three perpendicular directions were 0.4 and 0.9 cc at 30 J, 1.9 cc at 80 J and 2.8 and 3.4 cc at 250 J; in the right ventricular wall they were 0.4 and 0.5 cc at 30 J, 1.3 cc at 80 J and 2.5 and 4.2 cc at 250 J. In the right ventricular wall all 30 to 250 J lesions were transmural, whereas in the left ventricular wall only 250 J lesions were transmural. All lesions showed a necrotic area surrounded by granulation tissue with degenerated myofibrils. Thus, the size of the ablation lesion depends on delivered energy, whereas the pattern of histopathologic change is identical in the 30 to 250 J energy range. These results suggest that with accurate localization of the arrhythmogenic site one low energy shock may be successful with less myocardial damage.

Animals↗
PubMed1986

Arterial pressure and heart period in the conscious rabbit: diurnal rhythm and influence of activity.

Mean-arterial pressure (MAP), heart period (HP) and the level of physical activity were measured in conscious rabbits and averaged over one-hour periods during 14 consecutive days. Serial autocorrelation coefficients and serial crosscorrelation coefficients were computed, to analyse periodicity. Measurements were started immediately after implantation of the cannula (group A, n = 11) or 10-46 days after implantation of the cannula (group B, n = 6). In the course of 14 days, in group A, MAP decreased 9 mmHg and HP increased 21 ms (P less than 0.05). In group B, MAP decreased and HP increased in a similar way. Percentage activity did not show a trend. Significant diurnal rhythms were found. MAP and percentage activity reached the lowest values at noon, and the highest late in the evening. HP reached the highest values at noon and the lowest late in the evening. MAP and HP fluctuated exactly in antiphase. This suggests a common origin for both rhythms. During physical activity MAP was 10-15 mmHg higher and HP was 35-40 ms shorter than during rest. These differences did not show a trend or a diurnal variation. In individual animals MAP and HP varied greatly from hour to hour. These biological variations in MAP and HP as well as the influence of activity should be taken into account when conclusions are drawn from short-term measurements.

Animals↗
PubMed1986

Endocardial catheter mapping: validation of a cineradiographic method for accurate localization of left ventricular sites.

To guide surgical therapy for ventricular tachycardia by preoperative endocardial catheter mapping, accurate anatomic localization of arrhythmogenic sites is mandatory. For this reason we developed a mathematical cineradiographic method to compute left ventricular sites relative to three anatomic reference points: the centers of aortic and mitral valve ostia and the left ventricular apex. To validate the method 14 epicardial left ventricular markers were implanted in four dogs to simulate arrhythmogenic sites. Distances between markers and the anatomic references were calculated and the results were compared with postmortem measurements. The difference between calculated and measured distances was 0.5 +/- 3.1 mm (mean +/- SD), confirming accurate localization of anatomic marker sites. However, in surgery the results have to be displayed in a practically applicable, unambiguous way. Therefore, wire skeletons were constructed to represent calculated endocardial marker sites relative to the anatomic reference points. To validate this approach, 14 markers were implanted in the left ventricular subendocardium in four dogs. Wire skeletons were constructed, one for each marker site, and inserted postmortem into the left ventricular cavity via a 2 cm incision. In all cases the correct indication of a marker site by the corresponding wire skeleton was confirmed by fluoroscopic inspection in multiple projections. This wire skeleton technique may enhance the practical usefulness of preoperative endocardial catheter mapping.

Animals↗
PubMed1985

Financial analysis of an inner city trauma center: charges vs collections.

The changes in the economy and in tax rules have caused hospitals to assess the financial viability of different areas within their institutions. While emergency departments generally have become recognized as a cost-effective portal of entry for patients, trauma centers, particularly those located in the inner city, usually are seen as areas of large investment and small financial return. This study looks at a large, inner-city trauma service and the charges, collections, and demographics of the trauma population it serves. For patients admitted to the trauma service, total collections were 77% of charges. There was no difference in collections between those patients with blunt injuries and those with penetrating injuries; violent vs nonviolent injuries; patients transferred in vs primary receivals; or patients transferred out after stabilization vs those retained at the trauma center.

Accounting↗
PubMed1985

Post-extra systolic potentiation: influence of calcium and verapamil in rat and rabbit hearts.

The interactions of the inotropic effects of verapamil (0.05-2.0 mumol l-1), calcium (0.33-5.2 mmol l-1) and post extra systolic potentiation (PESP) as induced by paired stimulation were studied in isolated rabbit and rat hearts under isovolumic and isotonic conditions. At low doses of verapamil, contractions were depressed, but those elicited by paired stimulation showed less depression than contractions of the same rate during single stimulation and even exceeded the unpotentiated contractions without verapamil. At high doses of verapamil contractility could not be restored by paired stimulation. Although contractions were restored to control level by an increase in extra-cellular calcium they were still abnormal in the sense that PESP could not be elicited. The excitation-contraction (e-c) uncoupling due to low calcium perfusion could be counteracted by paired stimulation but e-c uncoupling due to high dose verapamil could not be reversed by paired stimulation. Our results support the view that PESP does not only depend on augmented slow channel calcium influx but also on an enhanced calcium shift within the sarcoplasmic reticulum. We are doubtful about the idea that PESP can be used clinically to counteract the negative inotropic effect of high doses of verapamil.

Animals↗
PubMed1985

Dopamine and isoproterenol in imipramine intoxication in the dog.

Artificially ventilated anesthetized dogs were given imipramine 7.5 mg/kg/hr i.v. In the first group (n = 6) mechanical cardiac activity was no longer detectable after a cumulative dose of 20.0 +/- 6.6 mg/kg (mean +/- sd). When aortic flow had decreased to 75% of its initial value, in a second group (n = 5) of experiments dopamine 10 micrograms/kg/min and in a third group (n = 5) isoproterenol 1 microgram/kg/min were administered i.v.. The doses of dopamine and isoproterenol were doubled when aortic flow had again decreased to 75% and 100%, respectively, of the original values. Cardiac mechanical activity was not detectable after a cumulative dose of 43.8 +/- 13.3 in the dopamine and 42.5 +/- 8.0 mg imipramine/kg in the isoproterenol group. These values differed significantly from that in the reference group (both 0.01 greater than p greater than 0.001). In the first group plasma imipramine concentrations at the end of the experiments were 3.06 +/- 0.66, in the second 3.36 +/- 0.66 and in the third 3.32 +/- 1.10 mg/1. Desipramine concentrations were 0.078 +/- 0.06, 0.162 +/- 0.076 and 0.383 +/- 0.09 mg/1 respectively. Dopamine induced a hemodynamic profile of low output and high pressure and isoproterenol one of low pressure and high output. It is concluded that dopamine combined with isoproterenol might be effective in counteracting the cardiodepressant action of imipramine.

Animals↗
PubMed1984

Nonrandom ventricular rhythm in horses with atrial fibrillation and its significance for patients.

RR interval sequences during spontaneous atrial fibrillation in eight horses were analyzed as in previous studies in patients and dogs using histograms and serial auto-correlograms. In patients and dogs with spontaneous atrial fibrillation, ventricular rhythms were always random. In the horses, the histograms were skewed with median RR intervals of approximately 1,000 ms. A striking finding in these animals was the presence of long RR intervals up to 5,000 ms in duration. The shortest RR intervals lasted 400 to 600 ms. In contrast to findings in dogs and patients, the serial autocorrelograms showed periodicity that was reenforced by digitalis (n = 3), but eliminated by quinidine (n = 2) and atropine (n = 2). Quinidine and atropine eliminated the longer RR intervals, whereas digitalis increased the number of long RR intervals. In one horse, it was possible to measure intraarterial pressure, and large fluctuations in pressure were observed as the RR intervals varied from over 3,000 to less than 500 ms. It is postulated that these changes in blood pressure are associated with baroreceptor responses that may alter the electrophysiologic behavior of the atria and atrioventricular node. These changes cause the nonrandom patterns of ventricular rhythm in the horse. Because such very long RR intervals do not occur in human beings or dogs during atrial fibrillation, the random ventricular rhythm in these groups is maintained even during digitalis treatment.

Animals↗
PubMed1984

Mechanisms of initial blood pressure response to postural change.

The influence of supine rest on the blood pressure response to standing and 70 degrees head-up tilt was studied in detail for the first 30 s after the change of posture. Following 20 min of supine rest, the active transition to standing was accompanied by an immediate increase in systolic pressure of 29 +/- 6 mmHg (mean +/- SEM). This was followed by large fluctuations in systolic pressure: to -28 +/- 2 mmHg below control after 7 s and to 22 +/- 2 mmHg above control after 22 s (17 mmHg in excess of the systolic pressure level after head-up tilt). Following 1 min of supine rest, there was no difference in the immediate increase in systolic pressure. However, the magnitude of the subsequent changes was significantly diminished. With head-up tilt the immediate increase in blood pressure was absent and afterwards small changes were found that were also significantly influenced by the period of prior rest. Taken in conjunction with earlier studies, the following mechanisms are suggested. The immediate blood pressure increase resulted from compression of arteries by the contracting postural muscles. The subsequent blood pressure fall was caused by at least two mechanisms: (a) the fall was predominantly of reflex origin, because the immediate pressure increase stimulated the systemic baroreceptors; (b) supine rest possibly augmented the translocation of blood from the thorax which contributed, approx. 5 s from standing, to the reflex fall of blood pressure.

Adult↗
PubMed1984

Baroreflex modulation of ventricular rhythm in atrial fibrillation.

The influence of bilateral carotid sinus nerve stimulation was studied in a patient with atrial fibrillation. Stimulation resulted after approximately 1.5 s in abrupt prolongation of the minimum, median and maximum RR-interval, and in greater RR-interval dispersion. Virtually no change was observed in the random character of the ventricular rhythm. The absence of demonstrable baroreflex modulation of the ventricular rhythm in atrial fibrillation is probably due to the relatively long latency of the reflex effect on atrioventricular conduction in relation to the duration of the RR-intervals.

Atrial Fibrillation↗