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

The physiological effects and certain aspects of cardiac metabolism were studied in 14 patients undergoing primary aortic valve replacement. The operations were performed under moderate hypothermia (30 degrees +/- 2 degrees C) and blood for coronary perfusion was taken from a sidebranch of the arterial line. The majority of the hearts went spontaneously into ventricular fibrillation at some stage of the operation. In spite of the high resistance measured in the coronary perfusion cannulae, an intraluminar coronary blood flow of 380 ml/min was recorded. The myocardial oxygen uptake decreased to 6.0 ml/min at 29 degrees C compared with 20.0 ml/min at 36 degrees C. The elevated coronary sinus lactate throughout the period of coronary perfusion and the increasing level of ASAT-enzyme indicated that this technique could not fully protect the myocardium from ischaemic changes. One patient died of myocardial infarction and two others needed vasopressor support postoperatively, in spite of documented effective coronary perfusion throughout the procedure. Cannulation of the coronary sinus is a valuable adjunct for the study of cardiac metabolism during ECC and it was accomplished without complications.
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PMID:Myocardial protection during aortic valve replacement. Physiological and metabolic effects of selective coronary perfusion on the fibrillating heart. 3 82

The results in 80 patients undergoing simultaneous aortic valve replacement and aorta-coronary saphenous vein bypass grafting were analyzed to assess the effect of operative technique. The over-all operative mortality rate of 6.3% (five of 80) did not differ significantly from our results with aortic valve replacement alone. All patients who had isolated aortic valve replacement were operated upon with moderate hypothermia. The combined operation was performed in two ways. Thirty-one patients had aortic valve replacement prior to bypass grafting with intermittent coronary ostila perfusion. There were two deaths (6.5%), and five myocardial infarctions (16.1%) were diagnosed by standard electrocardiographic and enzyme criteria. More recently, 49 patients have undergone bypass grafting prior to aortic valve replacement. The proximal ends of the grafts were either anastomosed high on the aortic root or else individually cannulated to provide continuous distal perfusion during subsequent aortic valve replacement, with continuous coronary ostial perfusion. There were three operative deaths (6.1%) and one myocardial infarction (2.0%). The risk of combined aortic valve replacement and coronary bypass need be no greater than the risk of aortic valve replacement alone. Our experience suggests that myocardial perfusion distal to significant coronary artery stenoses reduces the risk of myocardial infarction in patients with coronary artery disease requiring aortic valve replacement.
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PMID:Aortic valve replacement and aorta-coronary bypass surgery. Results with perfusion of proximal and distal coronary arteries. 30 89

During a 7.5-year period ending in June 1977, 220 patients underwent combined aortic valve replacement and myocardial revascularization. Early (30-day) mortality was 5.4% (12 patients), and was significantly affected by the development of perioperative myocardial infarction. For 23 patients with electrocardiographic and enzymatic evidence for definite infarction, hospital mortality was 17%; for 66 patients with probable infarction mortality was 5%; and for 116 patients without evidence for infarction mortality was 3%. The difference in mortality between the definite and no infarction groups was significant (p less than 0.01). The incidence of perioperative infarction was influenced by the type of myocardial protection employed during the operative procedure. Definite infarction occurred in 24% of 41 patients who had mild (28-32 degrees C), intermittent hypothermic coronary perfusion, in 9% of 142 patients with hypothermic ischemic arrest (myocardial temperature 20 to 27 degrees C) and in none of 22 patients with hypothermic, potassium-induced cardioplegia (myocardial temperature 8--18 degrees C). The difference in the rate of infarction between the coronary perfusion and the two hypothermic ischemic arrest groups was significant (p less than 0.01). The mean duration of followup for 100% of the hospital survivors was 22.5 months. Cumulative survival was 88% at 1 year and 77% at 3 years. These figures do not differ significantly from those for patients without coronary artery disease having isolated aortic valve replacement in our institution, and are superior to those reported for patients with coronary and aortic valve disease undergoing only aortic valve replacement. We conclude that combined aortic valve replacement and myocardial revascularization should be performed in all patients in whom the lesions coexist. Hypothermic ischemic arrest, preferably in combination with potassium-induced cardioplegia, provides the most myocardial protection during operation.
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PMID:Combined aortic valve replacement and myocardial revascularization: results in 220 patients. 30 65

In a prospective study, patients who had an ejection fraction of 40% or more and who were undergoing elective coronary artery operation were randomly divided into three groups that differed in the method of anaerobic substrate enhancement during cardiopulmonary bypass. Group 1, the controls (n = 157), received no additional glucose, insulin, and potassium solutions and experienced immediate spontaneous defibrillation (10%), transmural myocardial infarction (10.3%), malignant ventricular arrhythmias (26%), and severe atrial arrhythmias (20%). Group 2 (n = 120) received a bolus of hypertonic glucose, insulin, and potassium in the pump perfusate before aortic cross-clamping. In this group, the rate of spontaneous defibrillation was 41%, of transmural infarction, 8.3%, of malignant ventricular arrhythmias, 31%, and of severe atrial arrhythmias, 19%. Group 3 (n = 114) had the aortic root continuously infused with glucose, insulin, and potassium solution at 4 degrees C during aortic cross-clamping. This group was significantly improved; the rate of spontaneous defibrillation was 60%, there were no transmural myocardial infarctions and the incidence of severe atrial arrhythmias was 6% and that of malignant ventricular arrhythmias, 5%. It is proposed that the superior clinical results in Group 3 resulted from better myocardial preservation achieved by more efficient means of providing continuous anaerobic substrate, coronary washout, and elution of lactic acidosis, uniform global hypothermia, and direct supplemental myocardial potassium in addition to mere cardioplegic effects.
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PMID:Reduction of intraoperative myocardial infarction by means of exogenous anaerobic substrate enhancement: prospective randomized study. 31 65

In 63 patients with either acute transmural or nontransmural myocardial infarction, the Q-T interval was prolonged beyond normal limits on at least 1 of the 5 days after infarction in 27 patients (8 with transmural and 19 with nontransmural infarction). The time-related changes in the corrected Q-T (Q-Tc) interval were defined for the entire sample and showed significant expansion, maximal on day 2, from a preinfarction control value. By day 5, the Q-Tc interval was no longer significantly prolonged and was not expanded beyond normal limits in any patient. Various possible causes of Q-T prolongation in myocardial infarction are local hypothermia, local conduction delay, neurogenic effect and local hypocalcemia. Collateral evidence suggests that the letter may contribute significantly to prolongation.
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PMID:Time-related changes in the Q-T interval in acute myocardial infarction: possible relation to local hypocalcemia. 64 72

Analysis of recorded monthly deaths in England and Wales shows a close association of death rates with external temperature in most diseases other than the cancers. Analysis of daily deaths in England and Wales and in New York shows the following relationships between temperature and deaths from myocardial infarction, strokes and pneumonia. Between -10 degrees and +20 degrees C mimimum temperature there is a nearly linear fall in deaths as the temperature rises. Above 20 degrees C deaths rise steeply as the temperature rises and below -10 degrees C rise steeply as temperature falls. These associations of deaths with temperature are much stronger in the elderly than in younger subjects. Detailed analysis of the daily deaths in England and Wales from myocardial infarction, strokes and pneumonia show that short-term (1--2 days) temperature changes have little effect on death rates but medium-term (7--10 days) and longer-term (three or more weeks) changes associated with very significant changes in death rates. The three diseases vary in the time relations between temperature change and change in death rates. In all three there is an interval between the change in temperature and death and this is shortest in the case of myocardial infarction (1--2 days before death), longest in the case of pneumonia (about a week before death) and intermediate in the case of strokes (about 3--4 days before death). At low temperatures death rates increase as the duration of temperature change increases, while at high temperatures (but below +20 degrees C) death rates decrease as the period of temperature change is longer. The implications of these findings are discussed and it is postulated that there is probably causal relationship between temperature change and deaths from a wide variety of diseases. A proximal link in the chain is probably a failure of autonomic control of body temperature in the elderly leading to a change in body temperature and some humoral change which in turn leads to death. It is not appropriate to concentrate on hypothermia as the relationship between temperature and death is seen at all temperatures.
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PMID:Environment, temperature and death rates. 72 71

Acute myocardial infarction with shock (AMI/S) was produced in 46 anesthetized "closed-chest" dogs by catheter injection of metallic mercury into the circumflex coronary artery. Twenty-four dogs were kept normothermic and 22 were maintained at 32 degrees C. Nine of the latter were rewarmed to 37 degrees C. and the experiments then were terminated, so that true survival time was arbitrarily shortened. Including these dogs, the survival time was three times longer than in the normothermic series (p less than 0.001). Hypothermia reduced heart rate (HR) by 34 percent, oxygen consumption by 38 percent, and myocardial oxygen consumption by an estimated 30 to 40 percent, while cardiac output (CO), stroke volume, and stroke work were unchanged. Left ventricular end-diastolic pressure (LVEDP) was reduced by 40 percent during hypothermia (p less than 0.05) and increased by 60 percent on rewarming. HR during rewarming increased substantially more than CO and thereby significantly reduced stroke volume.
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PMID:Induced hypothermia in dogs with acute myocardial infarction and shock. 88 82

Anoxic cardiac arrest, as opposed to induced ventricular fibrillation, greatly facilitates accurate distal anastomosis in aortocoronary bypass surgery. In order to diminish the anoxic insult, general and topical hypothermia may be used. In an attempt to establish the value of moderate hypothermia during anoxic cardiac arrest two groups of patients were compared. In group I coronary artery bypass procedures were performed under normothermic conditions with anoxic cardiac arrest. Patients in group II underwent similar procedures but under hypothermic conditions. General body hypothermia to an esophageal temperature of 30 degrees C and topical hypothermia with iced saline lavage were used. Using these techniques, the average intramyocardial temperature was 26 degrees C. Nonfatal cardiac complications did not occur more frequently in the hypothermic group. Operative mortality was decreased from 6.3% in the normothermic group to 1.5% in the hypothermic group. However, in group II, in addition to hypothermia, a second factor in the reduction of mortality was the completeness of the revascularization procedure: 58.5% of the patients had three or more bypass grafts in the hypothermic group. The mean anoxic arrest time was over 50 min for all patients--those who survived as well as those who died with postoperative low cardiac output or myocardial infarction. Therefore, anoxic arrest time should be kept as short as possible and certainly less than 50 min. Intermittent aortic occlusion and performance of the proximal anastomoses using a partial occluding clamp on the aorta are currently being used and, together with moderate hypothermia, provide a further reduction in postoperative myocardial complications.
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PMID:The value of moderate hypothermia during anoxic cardiac arrest for coronary artery surgery. 108 39

Among 3,707 patients who underwent aortocoronary bypass, 302 had preinfarction angina. Coronary angiography revealed single-vessel disease in 43 patients, double-vessel disease in 81, and triple in 178 patients. Plane ventriculography showed contractility to be normal in 178 patients, fair in 88, and poor in 36 patients. Left ventricular end-diastolic pressure was normal in 203 patients, 13 to 23 mm Hg in 73, and larger than or equal to 24 mm Hg in 26 patients. Using cardiopulmonary bypass and moderate hypothermia, single coronary bypass was performed in 45 patients, double bypass in 120 patients, triple in 118 patients, quadruple in 15, and quintuple in 4 patients. Right coronary artery endarterectomy was necessary in 22 patients. The early mortality was 6.6% (20 patients) and was strongly related to poor contractility and congestive heart failure. One- to four-year follow-up data were obtained in 126 patients. Late myocardial infarction occurred in 11 patients and caused 4 late deaths; 3 unrelated deaths occurred. Ten patients experienced no benefit from their operations, 56 are completely asymptomatic, and 53 are significantly improved. Our results show that surgical intervention can improve the poor prognosis of preinfarction angina and appears to be superior to medical treatment.
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PMID:Early and late results after surgical treatment of preinfarction angina. 108 34

Resection of the ascending aorta with or without aortic valve replacement requires prolonged interruption of myocardial blood flow. Profound local cardiac hypothermia was used in 8 patients, 5 of whom had simultaneous aortic valve replacement. Three patients with acute dissections were encountered, one with cardiac tamponade secondary to intrapericardial rupture. The duration of aortic cross-clamp time varied from 43 to 122 minutes. There were no complications related to the cooling technique. There were no operative or hospital deaths. One patient died of myocardial infarction at 6 weeks. These results coupled with the experience of others suggest that coronary perfusion during periods of obligatory anoxia in unnecessary. Local cardiac hypothermia offers a satisfactory alternative for myocardial protection during prolonged aortic crossclamping.
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PMID:Resection of the ascending aorta using profound local hypothermia for myocardial protection. 113 Aug 88


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