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

Strong experimental evidence links ventricular fibrillation to an increased temporal dispersion of the recovery of excitability. The effect of an overall prolongation of repolarization and an increased basic dispersion of repolarization on premature dispersion was studied on ventricular surface in 10 dogs. Our observations reveal the operation of several fundamental electrophysiologic mechanisms controlling the conduction and the refractoriness in the ventricular myocardium in vivo. Action potential (AP) duration was influenced by the heart rate, the duration of the preceding AP and the proximity to the repolarization of the preceding AP. These effects can both slow, or enhance ventricular conduction, during propagation of premature impulses. This model may be applicable to several clinical situations where APs are prolonged (hypothermia, drug effects, changes in electrolytes) or when dispersion of refractoriness is increased (long QT-time syndrome, neural imbalance of the heart with and without heart disease.
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PMID:Effect of uniformly prolonged, and increased basic dispersion of repolarization on premature dispersion on ventricular surface in dogs: role of action potential duration and activation time differences. 241 50

Knowledge of the effects of cardiopulmonary bypass on the myocardium and on cardiac function is limited. We therefore studied changes in haemodynamics and myocardial metabolism during the initial phase of cardiopulmonary bypass in two patient groups. In one group "normothermia" (34 degrees C) was used while on bypass, with an empty beating heart; in the other group hypothermia (range 27-33 degrees C) with ventricular fibrillation was used. Mean aortic pressure and myocardial oxygen consumption decreased significantly in both groups after instalment of CPB. The arterial-coronary sinus differences in lactate changed to negative values within 5 min of the start of bypass, indicating release instead of uptake of lactate. This release was maintained during the observation period and increased significantly in the hypothermic patient group when the ventricles were fibrillating. Therefore in patients undergoing aorto-coronary bypass surgery, detrimental changes in the myocardium must be anticipated during the initial phase of cardiopulmonary bypass prior to aortic cross clamping.
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PMID:Metabolic and haemodynamic changes in the heart during the early phase of cardiopulmonary bypass: I. Clinical observations. 259 Sep 18

A significant release of lactate instead of uptake was observed during the first 10 min of cardiopulmonary bypass preceding aorto-coronary bypass surgery in human patients. To clarify these findings in more detail, myocardial lactate and oxygen metabolism was studied in healthy dog hearts subjected to a protocol similar to the clinical situation. In one group (n = 11) normothermia at 34 degrees C was used with an empty beating heart, and in the other group (n = 11) hypothermia with ventricular fibrillation was applied. Within the first 10 min of bypass no significant changes in high energy phosphates were observed in myocardial biopsies. However, a marked decrease in mean aortic blood pressure and a simultaneous lowering in oxygen consumption was observed in both groups after instalment of bypass. An initial shift from lactate uptake to lactate release occurred while on bypass in the normothermia group. After 10 min of bypass, lactate uptake was restored in hearts of both groups. Therefore, the lactate release during the initial phase of bypass in patients originates both from the instalment of the bypass and from (local) inadequate perfusion, which is most likely to be due to stenosed coronary arteries.
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PMID:Metabolic and haemodynamic changes in the heart during the early phase of cardiopulmonary bypass: II. Animal experiments. 259 Sep 19

In 1951 in our laboratory in Stockholm, we successfully used our experimental pump oxygenator: the first dogs survived 40 minutes of total cardiopulmonary bypass with right ventricular cardiotomy. In the same year extracorporeal circulation was combined with hypothermia (26 degrees to 28 degrees C) to allow lower perfusion flows, thus diminishing blood trauma and the risk of perfusion complications. To avoid air emboli during cardiotomies, the heart was "arrested" with electrically induced ventricular fibrillation (1952). Our standard perfusion technique used cooling and rewarming with left ventricular bypass, the oxygenator was used only during intracardiac manipulations and when the right ventricle was unable to maintain a sufficient pulmonary circulation. Left ventricular bypass was continued until normal body temperature was reached and the heart could be weaned off the pump. In July 1954 we successfully extirpated a left atrial myxoma in our first patient undergoing open heart surgery, a 40-year-old woman, who is still alive today. Other successful applications of open heart surgery involved resection of a huge left ventricular aneurysm after infarction in 1955, correction of supracardiac total anomalous venous return in 1956, and the first hemodynamic correction of transposition of the great arteries by atrial switch method in 1958. Also in 1958, the first totally implantable pacemaker was inserted in a patient with total atrioventricular block to eliminate the infections that occurred along the percutaneous pacemaker leads. In October 1958, we also operated on a patient with severe angina pectoris with stenosis of the left anterior descending and circumflexed arteries and occluded right coronary artery. Endarterectomy of the left coronary arteries was performed, and the arteriotomies were repaired with saphenous vein patches.
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PMID:Developments in cardiac surgery in Stockholm during the mid and late 1950s. 268 18

High concentrations of bupivacaine and profound hypothermia individually cause intraventricular conduction disturbances and reentrant arrhythmias. The effects of the combination of relatively low concentrations of bupivacaine and mild hypothermia are unknown and are the subject of this study. Three groups (n = 10-12) of dogs anesthetized with thiopental-chloralose were treated as follows: group 1, bupivacaine + hypothermia; group 2, bupivacaine alone; group 3, hypothermia alone. Bupivacaine was administered as a 4 mg/kg iv bolus followed by an iv infusion of 0.1 mg.kg-1.min-1. Hypothermia, i.e., a 4 degrees C reduction in core temperature, was produced by cooling the blood with an extracorporeal circuit. The peripheral ECG was recorded to determine the duration of QRS complexes and the QT interval. Conduction time and effective refractory period (ERP) of ventricular contractile tissue were measured with right ventricular endocavitary electrodes. Measurements were made with the heart paced at 180 beats/min and without pacing. In group 1 dogs, bupivacaine (plasma level, 2.8 +/- 0.3 microgram/ml) initially caused a prolongation of conduction time and QRS duration, which were further lengthened (approximately doubled) by a temperature decrease of 4 degrees C from baseline. The QT interval and ERP also were increased but to a lesser degree. In dogs in which the effects were most pronounced, rhythm disorders, such as wave burst arrhythmias (most common), premature systoles, ventricular tachycardia, and even ventricular fibrillation, occurred either spontaneously or during pacing. Bupivacaine alone (group 2) increased QRS duration and conduction time significantly, whereas hypothermia alone (Group 3) did not cause changes in any conduction variables. In neither group were dysrhythmias observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Potentiation by mild hypothermia of ventricular conduction disturbances and reentrant arrhythmias induced by bupivacaine in dogs. 271 14

The authors present an account, based on their clinical material, of 15 endarterectomies of the coronary arteries, which from the chronological aspect are divided into two groups. The first six were performed in 1972-1974 without the use of cardioplegia, total cardias arrest, only with ventricular fibrillation, with a 50% rate of success. The series of the remaining nine patients was operated during the period between October 1987 and the end of 1988 under far more favourable conditions, using cold cardioplegia, hypothermia and total cardias arrest. Only one patient died 24 hours after operation, the remaining eight patients are being followed up for one to 14 months after operation. In six patients endarterectomy of the right coronary artery was performed and in three instances in the area of the r. interventricularis of the left coronary artery. There was no case of perioperative myocardial infarction. The immediate postoperative development of the patients is promising and encourages us to proceed with this surgery (endarterectomy of the coronary artery) which is the only alternative method in the group of patients with diffuse distal arteriosclerosis of the coronary arteries.
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PMID:[Endarterectomy of the coronary arteries]. 277 45

By the time, the results of surgical treatment for total anomalous pulmonary venous return have been unsatisfactory. From 1981, we changed a surgical procedure fro Gersony-Malm procedure to the posterior approach method, and a surgical technique from the deep hypothermia and the circulatory arrest to the moderate hypothermia and the pump perfusion. Consequently, the results of surgical treatment was improved. From 1981 to 1987, 18 neonates with total anomalous pulmonary venous return underwent corrective operations in our institute. This diagnosis was decided by echocardiography without cardiac catheterization, because the preoperative status of these neonates were poor. Under the cardiopulmonary bypass, we performed the posterior approach method for type I and III, the cut-back method and Van Praagh procedure for II and IV without aortic clamping. According to the posterior approach method, the atrial septal defect was closed through the left atrial incision and the left atrium was anastomosed to the common pulmonary trunk during ventricular fibrillation. The incision was limited within the common pulmonary trunk or the vertical vein and was not extended into the pulmonary veins. According to cut-back method and Van Praagh procedure, the coronary sinus was closed internally so as to avoid the postoperative conduction disturbance. There were four hospital deaths (22.2%). The causes of deaths were pulmonary hypertension in two, low cardiac output in one, and intracranial bleeding in one. From the results of our institution, we concluded that the primary factors determining the outcome were the condition of the patients prior to repair and the severity of pulmonary hypertension.
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PMID:[The results of surgical treatment of total anomalous pulmonary venous return in neonates]. 280 87

The article reviews pathophysiology and clinical problems. During deep hypothermia, criteria for death are obscured. Prehospital treatment should be vigorous resuscitation on broad indications. Asystole or ventricular fibrillation is common. Drugs are contraindicated, with the possible exception of bretyllium. Electro-conversion of the heart is usually impossible below 28-30 degrees Centigrade. Hypothermic victims must be handled with the utmost care. Rewarming may cause life-threatening arrythmias, afterdrop and "rewarming collapse". Rewarming should take place in hospital only. Different methods of rewarming are discussed. Probably the best way to treat deeply hypothermic victims is by cardiopulmonary bypass.
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PMID:[Accidental hypothermia. Physiopathology, clinical manifestations and treatment]. 281 43

Trauma to the heart and mediastinum is associated with external cardiac massage. A patient had undergone a redo mitral valve replacement and experienced an uneventful postoperative course. During a visit to her physician 6 weeks after operation, she experienced ventricular fibrillation that required external cardiac massage and subsequent defibrillation. Postresuscitation evaluation revealed a posterior pseudoaneurysm of the ventricle. This was repaired via a transthoracic approach with the use of profound hypothermia.
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PMID:Ventricular pseudoaneurysm associated with cardiopulmonary resuscitation 6 weeks after mitral valve replacement. 281 68

Forty-one patients who underwent cardiac surgery under conditions of systemic hypothermia and intermittent cold crystalloid potassium cardioplegia were studied, in order to elucidate the effects of ventricular fibrillation and reperfusion on the myocardium, by using the intramyocardial pCO2 and temperature sensor. All patients were assigned to 2 groups, namely; group A (21 cases), in which the time between the aorta declamping and defibrillation was under 10 minutes, and group B (20 cases) in which the time was over 10 minutes. In both groups A and B, myocardial pCO2 increased at the rate of 3.58 +/- 1.70 and 2.16 +/- 0.62 mmHg/min (p less than 0.05) after aorta declamping, respectively and the myocardial pCO2 decreased at the rate of 5.59 +/- 0.60 and 4.18 +/- 0.76 mmHg/min (p less than 0.05) after defibrillation, respectively. In group A, the myocardial calcium content, pre-CPB (cardio pulmonary bypass) was 10.98 +/- 1.62 nmol/mg/dry weight and at the time of aorta declamping it was 15.90 +/- 1.81 nmol/mg/dry weight (p less than 0.05). In group B, the myocardial calcium content, pre-CPB, was 14.62 +/- 2.15 nmol/mg/dry weight and at the time of aorta declamping it was 18.23 +/- 4.36 nmol/mg/dry weight (p less than 0.05). At both three and six hours after the operation, the left ventricular work index per minute (LVWI) in group A showed better cardiac pump function than that in group B. We therefore conclude that when reperfusion is encountered, acidosis can be minimized by prompt defibrillation.
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PMID:Myocardial tissue pCO2 and calcium content during ventricular fibrillation and reperfusion periods. 314 51


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