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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To assess the effects of moderate potassium cardioplegia (37 mEq/l KCl) on the severity of myocardial ischemia during arrest and on post arrest ventricular function, 32 isolated, isovolumic feline hearts were studied before, during and 1 hour after ischemic arrest. Normothermia (37 degrees C) was maintained in the remaining 16 hearts, eight without KCl and eight with KCl. Hypothermia (27 degrees C) was maintained in the remaining 16 hearts, eight with KCl and eight without KCl. Myocardial oxygen (PmO2) and carbon dioxide tensions (PmCO2) were measured by mass spectrometry. Maximum developed intraventricular pressure (max DP) and max dP/dt were used as indices of performance. Compared with normothermic or hypothermic arrest alone, the addition of potassium cardioplegia resulted in a significant reduction in the peak PmCO2 measured during the arrest period. Hypothermia alone resulted in morphologic evidence of improved myocardial preservation and a significant reduction in peak PmCO2 compared with normothermia. Post arrest ventricular function was best with the combination of hypothermic arrest and potassium cardioplegia (max DP = 96 +/- 6% of control and max dP/dt = 99 +/- 5% of control). These data suggest that the beneficial effects of postassium cardioplegia and 27 degrees hypothermia are additive, and that reduction in myocardial ischemia as evidenced by a reduction in peak PmCO2 correlated with improvement in ventricular performance in the post arrest period and with preservation of myocardial structure.
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PMID:Effect of potassium cardioplegia on myocardial ischemia and post arrest ventricular function. 30 60

The authors analyze the results of 220 applications of internal cold cardioplegia in 136 patients with ischaemic heart disease, treated surgically by aortocoronary bypass. The operation was performed under neuroleptanalgesia and artificial circulation with hypothermia (27.9 +/- 0.2 degrees C) and haemodilution (24.9 +/- 0.3%). On the basis of clinical examination, electron microscopy of the myocardial ultrastructure, and investigation of the myocardial metabolism (contents of glucose, lactate, pyruvate, free fatty acids, catecholamines, and oxygen in arterial and venous blood flowing out of the myocardium), they come to the conclusion that internal cold cardioplegia efficiently protects the myocardium during aortocoronary bypass and secures favourable conditions for the development of anastomoses between coronary arteries and venous shunts.
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PMID:Myocardial protection during aortocoronary bypass. 31 79

Cardiac output, venous admixture, physiological dead space, blood gas tensions, inspired gas distribution, and other respiratory variables were measured in 10 patients breathing both air and oxygen before and on five occasions up to 10 days after coronary artery vein-graft operations under cardiopulmonary bypass with moderate hypothermia. Cardiac output was unchanged at 8 hours but fell 8 percent by 22 hours. Thereafter it progressively increased and at 10 days was higher than before the operation. Venous admixture rose to a maximum at 28 to 48 hours, postoperatively, but the increase was inversely related to the magnitude of preoperative admixture. The part played by airway and alveolar closure in determining venous admixture is discussed. While admixture increased, the nitrogen-clearance curve improved, presumably due to progressive "dropout" of the worst-ventilated regions. Physiological dead space fell to a minimum at 28 hours after operation; this was attributed to a fall in the end-inspiratory position consequent upon a reduction in both functional residual capacity and tidal volume. There was an increase in ventilation after operation, and this persisted at 10 days; it appeared to be due to reflex stimulation from the lungs and chest wall.
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PMID:The effects of cardiopulmonary bypass upon pulmonary gas exchange. 33 1

37 canine kidneys were intermittently perfused with Collins- or Sacks-solution every 2--6 h. 32 of these kidneys were transplanted after 12--24 h storage time. Additionally, 24 kidneys were stored under hypothermia for 12--24 h and then transplanted (control group). During perfusion the oxygen consumption of the kidneys and the enzyme and lactate release were measured. It was impossible to improve the results of hypothermic storage preservation by intermittent perfusion of the kidneys, on the contrary kidney function deteriorated by the number of perfusion processes. The failure of intermittent perfusion is caused by the increase of renal vascular resistance during perfusion. From the oxygen consumption and lactate release measurement it was concluded, that the washout solutions for kidney preservation should contain more substrate which can be utilized under anaerobic conditions to improve the results of hypothermic storage preservation.
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PMID:[Canine kidney preservation by intermittent perfusion with hypothermic Collins- or Sacks-solution (author's transl)]. 39 64

This is a report a a new system for freezing human red blood cells in the same polyvinyl chloride plastic container in which the blood is collected and separated into components. This polyvinyl chloride plastic collection bag with integrally attached transfer packs for blood collection, component separation, red blood cell biochemical modification, freezing, storage, and post-thaw dilution before washing, represents a major advancement in the freeze-preservation process. The label with the donor's blood type and identification number affixed to the bag at the time of collection remains in place throughout the freezing and thawing process. The transfused red blood cells are of superior quality, and the processing cost is less than with other methods of freeze-preservation. There is a lower risk of contamination with these red blood cells because manipulation of the product is kept at a minimum. "Rejuvenation", a bioengineering process by which outdated red blood cells can be salvaged, can be incorporated into the preservation process using one of the attached transfer packs of the primary collection bag. This process has been introduced as a possible means of alleviating the dramatic blood shortages which occur periodically. Red blood cells may also be "rejuvenated" after storage in the liquid state to increase their 2,3 DPG and ATP levels to 150 to 200% of normal, and these red blood cells with improved oxygen transport function have been administered to anemic patients with and without cardiopulmonary insufficiency, patients undergoing cardiopulmonary bypass and treatment with hypothermia during cardiac surgery, and in instances where nonhemolytic transfusion reactions might be expected.
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PMID:Human red blood cells with normal or improved oxygen transport function prepared and frozen in the primary polyvinyl chloride plastic blood collection container. 39 73

Hemodynamic and respiratory effects of a 5-hr IV infusion of Ps. aeruginosa at a dose of 10(8) organisms per ml per minute were studied in 6 dogs. Four dogs served as controls. Gramnegative bacteremia, with 70,000 +/- 1,800 organisms per ml of blood, caused a 50% reduction of cardiac output at three hrs. Peripheral vascular resistance increased significantly, but mean heart rate fell below control levels. Decline in mean systemic blood pressure from 150 +/- 5 mm Hg to 88 +/- 6 mm Hg was accompanied by a significant increase in pulmonary arterial wedge pressure with normal right atrial and pulmonary arterial pressures. Pulmonary vascular resistance also remained unchanged. With progression of the low output state and development of hypothermia, arteriovenous oxygen difference (A-V DO(2)) fell significantly. Despite a decline in functional residual capacity, venoarterial admixture diminished in the face of reduced pulmonary capillary perfusion, normal arterial Po(2) values, decline in body temperature and finally very narrow A-V DO(2). Histologically, ventricular myocardium revealed severe interstitial edema. It is concluded that myocardial dysfunction may occur early during gramnegative bacteremia, and formation of myocardial edema appears to be a significant contributing factor in myocardial failure.
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PMID:Cardiac depression in bacteremia. 40 65

The hemodynamic and cardiac biochemical effects of global ischemic arrest during cardiopulmonary bypass (CPB) were studied in 54 animals and compared to seven animals without ischemic arrest. Ischemic arrest alone reduced the first derivative of left ventricular force of contraction (LV dF/dt) to 52 percent of control 10 minutes after resuming function and to 64 percent after 1 hour of reperfusion. Cardiac output was depressed to 52 percent of control after 10 minutes of reperfusion, and to 74 percent of control after 60 minutes of reperfusion. In six animals, moderate hypothermia (26 degrees C.) resulted in no protection of cardiac function from ischemic arrest, whereas profound hypothermia to 18 degrees C. resulted in values of LV dF/dt and cardiac output nearly equivalent to the CPB control group (no arrest). A continuous infusion of a hyperkalemic hypothermic solution slightly improved the degree of protection over hypothermia alone. The sarcoplasmic reticulum (SR) isolated from hearts which had undergone 60 minutes of ischemic arrest bound significantly less calcium when the isolation was done after 10 minutes of reperfusion as well as when it was done after 60 minutes of reperfusion. The time to spontaneous release of calcium from the SR also was significantly longer. Moderate hypothermia did not result in improved SR function, whereas deep hypothermia induced by local cooling or by hypothermic potassium infusion retained SR function at normal levels. Oxidative phosphorylation of mitochondria isolated after 60 minutes of reperfusion was also depressed. The mitochondrial respiration rate after normothermic ischemic arrest was 155 natoms of oxygen per minutes versus 237 natoms for the hypothermic hyperkalemic group. Respiratory control index was 5.5 for the normothermic group versus 9.4 for the hypothermic group. It is concluded that hypothermia, whether effected by surface cooling or by hypothermic potassium infusion, allowed full recovery of hemodynamic and biochemical functions within 1 hour of reperfusion.
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PMID:Myocardial depression after elective ischemic arrest. Subcellular biochemistry and prevention. 42 95

The quantitative effects of a combination of hypothermia and phenobarbital on cerebral oxygen uptake (CMRo2) was studied in rats, curarized and artificially ventilated with 70% nitrous oxide in oxygen. Cerebral blood flow (CBF) was measured with a modification of the KETY & SCHMIDT (1948) technique, using 133xenon as a tracer. Arteriovenous difference in oxygen content over the brain was measured and CMRo2 was calculated. Four groups were studied. Group 1 was a control group. The three experimental groups were injected with phenobarbital intraperitoneally: Group 2 with 50 mg/kg body weight; Group 3 with 150 mg/kg; and Group 4 with 50 mg/kg of phenobarbital, and, in addition, body temperature was lowered to 32 degrees C in this group. CMRo2 in groups 2, 3 and 4 was reduced by 22, 37 and 43%, respectively, compared to Group 1. The changes in CBF were of the same magnitude. In a previous study we have found that CMRo2 decreases by 5% per 1 degree C decrease in body temperature. The value for CMRo2 in Group 4 is close to the value obtained if the effect of 50 mg/kg body weight of phenobarbital on CMRo2 is added to the effect of a temperature reduction of 5 degrees C. It is concluded that the effects of barbiturates and hypothermia on CMRo2 are additive.
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PMID:Additive effects of hypothermia and phenobarbitol upon cerebral oxygen consumption in the rat. 42 19

Ventricular fibrillation during normothermic cardiopulmonary bypass is deleterious to the myocardium. This study was undertaken to determine if moderate systemic hypothermia would protect the myocardium during ventricular fibrillation. Fourteen mongrel dogs were subjected to 1 hour, 15 minutes of total cardiopulmonary bypass. Ventricular fibrillation was induced by a continuous electrical alternating current applied at the beginning of bypass and lasting for 1 hour. Six animals were maintained at normothermia (Group I), and eight were cooled to 30 degrees C. for 1 hour (Group II). The hypothermic group (Group II) demonstrated lower myocardial oxygen consumption and metabolism, decreased coronary blood flow, and less myocardial lactate production during ventricular fibrillation than did Group I. It is concluded that hypothermia does offer some protection, although not complete, against the deleterious effects of ventricular fibrillation described previously.
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PMID:Effects of systemic hypothermia on myocardial metabolism and coronary blood flow in the fibrillating heart. 43 25

Nifedipine, a slow-channel calcium blocker, is thought to provide useful myocardial protection during prolonged total ischemia and reperfusion. An isolated, isovolumic, feline heart model was used to asses the effectiveness of nifedipine in both cardioplegic (100 microgram/10 ml) and noncardioplegic (10 microgram/10 ml) doses for providing myocardial preservation during 90 minutes of hypothermic ischemic arrest and 45 minutes of normothermic reperfusion. Use of nifedipine was compared to hypothermia (27 degrees C) alone and to hypothermia with potassium cardioplegia. Ventricular function was assessed by recovery of isovolumic left ventricular developed pressure and dP/dt. Myocardial carbon dioxide tension (PCO2) and myocardial oxygen tension (PO2) were measured by mass spectrometry. Potassium cardioplegia and the higher dose of nifedipine resulted in immediate asystole. The rates of rise of PCO were greatest in the group receiving 10 microgram nifedipine and in the control group. The rates of rise in the two cardioplegic groups were significantly lower. Recovery of ventricular function was significantly lower with low-dose nifedipine than with potassium cardioplegia. Higher dose nifedipine resulted in a return of function, which was no different than with potassium cardioplegia. Morphologic protection was better with higher dose nifedipine and potassium cardioplegia than with either low-dose cardioplegia or hypothermia alone. These results demonstrate that nifedipine in a cardioplegic dose results in preservation of myocardial structure and function that is similar to that obtained with potassium cardioplegia. In lower noncardioplegic dose, nifedipine does not appear to offer additional protection compared to hypothermia alone. Whether persistent depression of ventricular contractility will limit nifedipine's clinical usefulness as a myocardial protection agent will require further study.
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PMID:Comparison of myocardial protection with nifedipine and potassium. 44 71


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