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Biomedical subjects

T M Runge

Publications and source records attributed to T M Runge.

13 recordsLinked to original sources
PubMed1992

Tubing spallation in extracorporeal circuits. An in vitro study using an electronic particle counter.

The roller pump is the most common pumping device used in extracorporeal circulation (ECC). The interaction between the roller and tubing causes tubing spallation. Spallation has been associated with complications in ECC. Previous spallation studies present mixed results, including a decrease in the number of circulating particles. The objective of this work is to perform an in vitro study of tubing spallation which elucidates the causes of the particle sequestration, and the effect of tubing material, blood flow rate and duration of the procedure upon spallation. A sampling method minimizing background counts was devised. Silicone and PVC tubing were tested under normal and tight occlusion pressure at typical cardiopulmonary bypass and hemodialysis flow rates, for circulating times up to 4 h. Occlusion pressure and flow rate highly influenced the amount of spallation produced. Particle sequestration was noted and aggregation of the plastic particles was demonstrated. We conclude that, at least in vitro, aggregation causes the decrease in the particle counts and the misleading results obtained in most spallation studies using a Coulter counter.

Biocompatible Materials↗
PubMed1991

Comparison of a steady flow pump to a preload responsive pulsatile pump in left atrial-to-aorta bypass in canines.

A unique preload responsive pulsatile pump was compared to a centrifugal pump in total cardiac support in 25-kg canines (n = 6, each group) in the left atrial-to-aorta mode during 5 h of ventricular fibrillation. With steady flow, there was immediate drop in output from 2.1 +/- 1.0 L/min to 1.4 +/- 0.3 L/min, followed by further reduction to 0.9 +/- 0.2 L/min during 5 h of ventricular fibrillation. With a pulsatile pump, there was no significant reduction from control of 2.4 +/- 0.6 L/min and no decline during 5 h of ventricular fibrillation. With steady flow, systemic vascular resistance (SVR) rose significantly from 1,762 dyne-s-cm-5 immediately on pump to 3,013 dyne-s-cm-5 at 5 h. With physiologic pulsatile flow, significant elevation of SVR did not occur. When stressed, due to diminished left atrial return, the centrifugal pump displayed line chatter and streaks of microbubbles, whereas the pulsatile pump did not. Crystalloid volume replacement with the centrifugal pump was 6.5 +/- 1.9 L, and with the preload responsive pulsatile pump, 5.6 +/- 1.3 L. It is concluded that in the left atrial-to-aorta mode during 5 h of ventricular fibrillation and with comparable volume replacement, total cardiac support of canines is associated with lower SVR with physiologic pulsatile flow and is not accompanied by line chatter and cavitation with this preload responsive pump.

Animals↗
PubMed1989

Preload-responsive, pulsatile-flow, externally valved pump: cardiopulmonary bypass.

Currently two pumps are used for cardiopulmonary bypass, the roller pump and the centrifugal or vortex pump. Both are steady-flow pumps. The procedure of cardiopulmonary bypass possesses a finite morbidity and mortality. The degree to which steady flow is responsible for this morbidity and mortality remains to be clarified, but investigators have established the fact that a physiologic degree of pulsatile flow must be achieved before its beneficial results, such as normal systemic resistance and absence of lactate production, can be demonstrated. Availability of a satisfactory pulsatile pump for cardiopulmonary bypass has been a problem in the past but the pump presented here may satisfy this need. It produces physiologic pulsatility with rate dependent ejection time equal to or less than that of humans (413 microseconds minus 1.7 times heart rate), and it is preload-responsive, varying its pumping rate and output with filling pressure. The pump is externally valved to minimize hemolysis, which has been demonstrated in two laboratory studies to be significantly less than with the roller pump. It produces pulsatile flow through membrane oxygenators. The pump is thought to have potential for several clinical applications in addition to (1) pulsatile-flow cardiopulmonary bypass, including (2) left, right, or combined transthoracic QRS synchronized ventricular assist, (3) femoral vein to femoral artery QRS synchronized left ventricular assist, (4) adult or infant ECMO, (5) pulsatile flow hemodialysis. In the latter, spallation and embolization of hemodialysis tubing particles should not be a problem as has proved to be the case with the present hemodialysis pump.

Cardiopulmonary Bypass↗
PubMed1986

Difference in degree of A-V block and QS2 abbreviation of ouabain digoxin and digitoxin in cats.

Six trained domestic cats received a spectrum of polar to nonpolar cardiac glycosides: ouabain, digoxin or digitoxin with medication free intervals of four weeks. Significant (P less than 0.01) rate reduction (-19 +/- 8%) and prolongation of PR interval (+13 +/- 5%) occurred with ouabain and with digoxin (-18 +/- 5% and +13 +/- 3%) but not with digitoxin (-6 +/- 4% and +6 +/- 5%). However, rate corrected QS2 abbreviation was greater with digitoxin (-13 +/- 3%) than with ouabain (-8 +/- 3%) or digoxin (-10 +/- 5%). The findings indicate that in cats the polar cardiac glycosides ouabain and digoxin produce greater prolongation of A-V conduction while the nonpolar glycoside digitoxin produces greater abbreviation of QS2. Previously this finding was reported by the authors in guinea-pigs and in rabbits and has since been reported in intact rats, dogs, and in man by other authors. Investigators using nonintact subjects have not been able to demonstrate the finding. The differences may have clinical significance and suggest new insight into structural/activity relationships within the cardiac glycoside family.

Animals↗
PubMed1977

Clinical implications of differences in pharmacodynamic action of polar and nonpolar cardiac glycosides.

The principal effects of cardiac glycosides probably can be classified as parasympathomimetic or sympathomimetic. Data from animals and from man suggest that polar cardiac glycosides, such as ouabain and digoxin, possess greater parasympathomimetic (vagal) cardiac effect for a given amount of sympathomimetic (positive inotropic) cardiac effect than do less polar cardiac glycosides, such as digitoxin. Polar glycosides therefore offer some advantage in uncomplicated paroxysmal atrial tachycardia and in uncomplicated atrial flutter and atrial fibrillation when the principal desired effect is reduction in the number of atrial impulses reaching the ventricles or conversion to normal sinus rhythm. Non-polar glycosides offer an advantage when positive inotropicity is desired but when there is some degree of atrioventricular block or when inappropriate sinus bradycardia or anorexia, nausea, or vomiting are present. Ecotopic impulse formation when due to cardiac glycosides is a toxic manifestation of excessive sympathomimetic effect, but is aggravated by vagal-induced sinus bradycardia, so that both parasympathomimetic and sympathomimetic capability of cardiac glycosides must be considered when dealing with myocardial electrical instability.

Animals↗
PubMed1975

Pharmacodynamic distinctions between ouabain, digoxin and digitoxin.

Current pharmacologic texts recognize no significant pharmacodynamic differences between the various cardiac glycosides. To reconsider this concept, a special recording device was constructed so that electrocardiograms and phonocardiograms could be obtained in small mammals without anesthesia or premedication, and a spectrum of cardiac glycosides was studied. Utilizing guinea-pigs, cardiac rate reduction of 20% was sought and achieved with 0.07 mg/kg ouabain, 0.34 mg/kg digoxin and 1.12 mg/kg digitoxin. With comparable rate reduction, digitoxin produced significantly greater shortening of electro-mechanical systole than did ouabain or digoxin (P less than 0.05). Other authors have shown that cardiac glycosides produce slowing of cardiac rate prior to onset of positive inotropic effect. Therefore it is probable that for a given amount of vagal effect (sinoatrial slowing) digitoxin possesses greater positive inotropic effect (abbreviation of electromechanical systole) in guinea-pigs than do ouabain or digoxin. A review of the literature suggests that the same holds true for humans.

Animals↗
PubMedDate not supplied

Achievement of physiologic pulsatile flow on cardiopulmonary bypass with a 24 French cannula.

In 1990, the NIH formally recognized the need for investigation of the problem of damaging the effects of cardiopulmonary bypass, issuing RFA HL-90-12-H, which emphasized production of neurologic defects in the very young and the elderly. The authors were at that time involved in comparison of pulsatile flow to steady flow cardiopulmonary bypass in large ungulates. The world literature recognizes five damaging effects of steady flow cardiopulmonary bypass that can be mitigated by pulsatile flow: metabolic acidosis, interstitial fluid accumulation, elevated systemic vascular resistance, arteriovenous shunting, and impaired brain oxygenation. To maximize the beneficial effect of pulsatile flow, however, it is necessary that its morphology be physiologic. It has been stated in the past that this goal may not be possible using standard size aortic cannulas. The purpose of this publication is to describe a method by which this feat has been achieved in 150 pound ungulates undergoing prolonged cardiopulmonary bypass.

Animals↗