[Continuing and discontinuing measurement of bioparameters (tissue pH, blood pH, arterial and venous pO2, lactates) in acute animal experiment].
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Animals↗
Biomedical subjects
U Mittmann
Publications and source records attributed to U Mittmann.
Regional myocardial blood flow after hypothermic arrest and cardioplegia.
Malperfusion due to increased coronary vascular resistance is presumably one of the factors responsible for incomplete functional recovery of the heart after aortic cross-clamping. Myocaridal blood flow (MBF, radioactive microspheres) was measured before and after 60 min of hypothermic ischemia in 16 dogs on cardiopulmonary bypass. After ischemia the hearts were reperfused for 30 min. MBF was measured in the empty beating heart and in the isovolumetrically contracting ventricle loaded with enddiastolic volumes (EDV) of 10, 20 and 30 ml (intraventricular latex balloon).
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[Comparative studies on pulsatile and continuous flow during extracorporeal circulation. Effects on liver function and endocrine pancreas secretion].
The effects of pulsatile and nonpulsatile flow pattern on pancreas and liver blood flow were studied in nine dogs on cardiopulmonary bypass (CPB). Furthermore, plasma levels of glucose, insulin, glucagon, growth hormone, and cholinesterase were compared in 20 patients subjected to open heart surgery with either pulsatile or nonpulsatile perfusion. Impairment of liver and pancreas function was significantly greater at the end of CPB and 48 h afterwards with nonpulsatile flow as compared with the pulsatile flow pattern. A decrease of intestinal blood flow that was demonstrated in dogs subjected to nonpulsatile perfusion could at least in part be responsible for the difference in postoperative organ function observed in patients after CPB.
Animals↗
[Subendocardial jeopardy of the hypertrophied myocardium].
In moderate hypertrophy (+35%) of the canine left ventricle (LV), resting myocardial blood flow (MBF, tracer microspheres) was not significantly altered when compared with controls. The endo/epi flow ratio of the LV was, however, significantly smaller (0.82-0.9) than in controls (1.02-1.17). After coronary dilatation with dipyridamole, coronary flow reserve was smaller in hypertrophied hearts. This became particularly obvious when acute coronary constriction (70%) was induced. There was, however, no indication that after coronary constriction in early hypertrophy the subendocardium was more jeopardized than in controls.
Animals↗
[Femoral head blood flow in dogs subjected to intra-articular pressure increase and to pressure release].
In six beagles femoral head blood flow is measured with radioactive microspheres. When intra-articular pressure of the hip joint is increased by 50 mm Hg, blood flow is diminished to 48%. Reducing intra-articular pressure to the initial level increases femoral head blood flow to 78%. The results support the demand for immediate pressure relief of hemarthrosis.
Animals↗
[Animal experiments on the hemodynamics of prehepatic portal hypertension before and following various methods of portacaval anastomosis].
In 24 dogs (29 +/- 5,7 kg) general and intestinal hemodynamics were measured during acute prehepatic portal hypertension before and after mesentericocaval, splenorenal, and splenocaval (SCA) shunt. From the hemodynamic point of view the SCA is superior because of its complete venous decompression of the region of the spleen and cardia and a greater blood flow to the liver. Furthermore shunt flow, and consequently volume load imposed on the general circulation, is significantly smaller in SCA.
Animals↗
[Regional myocardial blood flow and ventricle function following hypothermic ischemia and cardioplegia].
Regional myocardial blood flow (MBF) and left ventricular (LV) function were measured in 18 dogs after 60 min hypothermic (14-16 degrees C) arrest with (group I) and without cardioplegia (group II). Regardless whether postischemic LV function was severely (group II) or only moderately (group I) impaired, the amount of MBF and its transmural distribution was not significantly altered after 30 min reperfusion. In contrast to topical hypothermia, additional cardioplegia maintained metabolic regulation of coronary flow.
Animals↗
[Extravascular albumin and water content of the lungs in traumatic-hemorrhagic shock].
Fifteen mongrel dogs are subjected to a standardized traumatic hemorrhagic shock. Plasma albumin, measured by J-125-albumin distribution, decreases to 58% of its original level after trauma and hemorrhage. Lung albumin content increases to 53% of the blood level. Lung water content is studied in vivo using the double indicator technique, post mortem by gravimetric methods. None of these methods shows an augmentation of lung water. The massive albumin loss occurs, particularly in the lungs, due to capillary leakage. The constant pulmonary water content can possibly be explained by early artificial respiration and by the fact that in contrast to clinical situations no infusion therapy was performed.
Animals↗
In vivo performance of the pH tissue electrode during acute acid-base changes in the dog.
The ROCHE tissue pH-electrode was tested in acute animal experiments under various metabolic conditions. In anesthetized dogs an electrode was placed in the subcutaneous tissue of the scalp, neck, and axilla. Simultaneous with the continuous measurement of tissue pH, the overall acid-base balance of the animal was measured discontinuously at 5-min intervals by means of indwelling arterial and venous catheters. Various forms of acidosis and hypoxia were produced in the experimental animal and the sensitivity of the electrodes in relation to their site was tested. A high correlation between the continuously measured tissue pH values and the corresponding arterial and venous actual blood pH values were found in the physiologic pH range. With acute changes of acid-base balance no correlation could be found in the acidotic range.
Acid-Base Imbalance↗
[Coagulation inhibition caused by selective thrombin blockade with hirudin].
Hirudin causes a rapid inhibition of blood coagulation as shown by in vitro and in vivo experiments in the dog. The substance appears to be a rather specific antithrombin. Its inhibitory action is linearly dose related and therefore easy to control and reproduce. Side effects can be expected to be abolished after further purification of the substance.
Animals↗
[Experimental model of protracted traumatic-hemorrhagic shock. I. Organ blood flow].
Experimental trauma and hemorrhage acutely reduce capillary blood flow in all organs except the heart. After reinfusion of the withdrawn blood a long-lasting increase of pulmonary bronchial blood flow and hepatic and renal blood flow is observed parallel to a rise in cardiac output. However, blood flow in the intestines, pancreas, and spleen remains significantly reduced. Particularly, renal and pulmonary bronchial blood flow is significantly higher in animals surviving for 72 hr than in animals succumbing after an average of 32 hr.
Animals↗
[Experimental protracted shock. II. Blood coagulation and histological changes].
Twenty mongrel dogs are subjected to a standardized traumatic hemorrhagic shock. After reinfusion of the dogs' own blood the animals are continuously observed for the 72 hr. Deterioration of general hemodynamics and activation of intravascular coagulation is more pronounced in the nonsurviving animals. Correspondingly, histologic alterations particularly of the liver and intestine are more marked in the nonsurvivors. Increase of partial thromboplastin time and long-lasting increase of the prothrombin time (Quick) appear to be early signs of a fatal prognosis.
Animals↗
[Experimental coronary bypass operation: distribution of myocardial blood flow early and after one year].
In 10 dogs a stenosis greater than 75% of the left circumflex coronary artery is induced (Ameroid) in the course of 40 days. Within 1 hour after coronary artery bypass operation (n = 6) maldistribution of myocardial blood flow (MBF), consisting of a subendocardial perfusion deficit, is improved but not completely abolished. One year after coronary bypass operation (n = 4) MBF and its endo/epi-distribution is normal. Bypass flow and its flow profile are useful indicators of MBF and its intramyocardial distribution only when coronary dilation is induced.
Animals↗
[Myocardial blood flow distribution immediately following experimental aortocoronary bypass and 1 year postoperatively].
A 75--90% stenosis of the left circumflex coronary artery (CCA) was induced over a period of 40 days in 11 mongrel dogs. Coronary blood flow and the distribution of myocardial blood flow (MBF, tracer-microspheres) was measured at rest and after maximal coronary dilatation in 8 dogs before and within 1 hour after coronary bypass. In 3 dogs these measurements are performed 1 year after bypass op. During coronary stenosis distribution of myocardial blood flow in the area supplied by the CCA was unhomogeneous, the subendocardium receiving less. Within 1 hour after opening the graft, MBF to the subendocardium was improved but the unequal distribution not completely abolished. One year after bypass op, however, the quantity and distribution of MBF appear to be normal although revascularized myocardium was perfused in part via coronary collaterals.
Animals↗
Experimental coronary artery bypass operation. Myocardial blood flow, ventricular performance and regional myocardial function.
Myocardial blood flow and ventricular function was studied in seven dogs with chronic myocardial ischemia before and after coronary bypass grafting. Restoring blood flow in an area of 25% of the anterior wall of the left ventricle did not significantly improve overall ventricular function. Assessment of intramyocardial pressure as an index of regional myocardial function revealed a consistent enhancement of myocardial contraction at rest, and under pharmacological stress of the heart.
Animals↗
[Myocardial blood flow and ventricular function in dependence on the size of myocardial infarct].
In eight dogs three branches of the left anterior descending coronary artery were occluded by successive ligations. Each time coronary flow reserve was measured by injecting dipyridamole (0.4 mg.kg-1). After an infarction of 13% of the left ventricle there was a significant decrease of Vmax and dp/dtmax (p less than 0.05). Measurements of regional myocardial blood flow detected an infarction of 5% of the left ventricle, whereas the total myocardial blood flow was reduced significantly when 17% of the left ventricle was infarcted.
Animals↗
Influence of cinepazide, a vasoactive substance, on canine coronary circulation after acute constriction of the left anterior descending coronary artery.
The left anterior descending coronary artery was variably constricted mechanically in nine dogs. Blood flow in the left anterior descending (LAD) and circumflex coronary arteries (CCA), aortic pressure and peripheral, i.e. post-stenotic coronary pressure were measured. Myocardial perfusion was determined from the clearance of radioactive xenon injected at a depth of 7 mm into the underperfused area supplied by the LAD artery. The vasoactive drug 1-(pyrrolidinyl-1-carbonyl)-methyl-4-(3,4,5-tri-methoxycinnamoyl)piperazine-maleate (cinepazide) was given at doses of 5-10 mg/kg by i.v. route. 1. Blood flow in the LAD was decreased stepwise to 50% of its initial value. There was practically no more coronary reserve. After drug injection, diastolic aortic pressure, that normally falls, was kept constant by clamping. Heart rate, perfusion pressure, post-stenotic pressure, and blood flow and resistance in the LAD showed practically no change. In the CCA, blood flow increased significantly (p less than 0.005) and flow resistance decreased (p less than 0.001). 133Xe clearance showed an increased myocardial perfusion (p less than 0.02) in the territory supplied by the LAD artery. 2. The lumen of the LAD was narrowed by 53%, i.e., coronary reserve was decreased. This constriction was followed by no haemodynamic reaction. After injection of cinepazide, mean and diastolic aortic pressure (p less than 0.02) and post-stenotic coronary pressure (p less than 0.005) decreased. Blood flow increased by 41% in the CCA and by 31% in the LAD. Coronary resistance in these vessels decreased (p less than 0.001 and 0.005, respectively). Here, too, the 133Xe clearance curve showed an increase in myocardial perfusion in the territory supplied by the LAD artery (+78%).
Animals↗
[Regional myocardial blood flow and left ventricular function in critical coronary stenosis and after coronary artery bypass grafting in the dog (author's transl)].
In 7 mongrel dogs myocardial ischemia is produced by means of an ameroid constrictor placed on the left circumflex coronary artery (CCA). Myocardial blood flow (MBF) is diminished by 56% in an area of 25% of the anterior wall of the left ventricle. A decrease in dp/dtmax suggests a small depression of left ventricular function. After bypass operation the slight changes in EDP, dp/dtmax and Vmax indicate no significant improvement of total ventricular function. MBF increases from 42 +/- 10 ml/100 g/min to 67 +/- 21 ml/100 g/min (p smaller than 0.02) in the area supplied by the bypass. In this region intramyocardial pressure rises significantly suggesting improvement of regional myocardial function.
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