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

Little is known about postnatal changes in myocardial purine metabolism. We therefore studied how ATP catabolism was affected by hypothermia and ischaemia in neonatal and adult hearts. Hypothermia during ischaemia protected isolated adult and newborn hearts against ATP decline. Reperfusion after normothermic ischaemia resulted in higher ATP levels in newborn hearts with less release of ATP-catabolites. During normoxia adult hearts released mainly urate (80% of total purine release), while newborns released mainly hypoxanthine (64%). During early reperfusion adult and newborn hearts released mainly inosine (50-60%). The very low xanthine oxidase activity in the neonatal heart could be an important factor in the observed ATP preservation during reperfusion.
Basic Res Cardiol 1987
PMID:Developmental differences in myocardial ATP metabolism. 366 14

Three infants developed greatly accelerated junctional ectopic tachycardia with a heart rate greater than 200 beats/min after open heart surgery. When the heart rate exceeded 200 beats/min for 5 hours, all the infants had congestive heart failure and clinical signs of low cardiac output. Conventional therapy (cardioversion, lidocaine, verapamil, digoxin and ice to face) has been shown in the past to be unsuccessful in controlling the heart rate. Because hypothermia is known to decrease automaticity of the heart, these patients were treated with induced hypothermia. The goal was to arbitrarily decrease the junctional ectopic rate to less than 180 beats/min to increase cardiac filling time. The duration of the junctional ectopic tachycardia greater than 180 beats/min ranged from 0.5 to 17 hours after cooling began. The duration of the hypothermia ranged from 4 to 24 hours. Spontaneous reversion to sinus rhythm occurred either during the hypothermia or shortly thereafter in all three patients. The blood pressure and urinary output remained stable during hypothermia. Hypothermia is an effective means of controlling the rate of greatly accelerated junctional ectopic tachycardia after open heart surgery in infants. Although hypothermia does not convert junctional ectopic tachycardia to sinus rhythm, it slows the rate to a more acceptable level, allowing the infants' survival and eventual recovery of sinus rhythm.
J Am Coll Cardiol 1987 Nov
PMID:Hypothermia for the treatment of postsurgical greatly accelerated junctional ectopic tachycardia. 366 5

Postoperative supraventricular tachyarrhythmia may occur more often in patients with persistent atrial activity during hyperkalemic hypothermic cardioplegic arrest. Cannulation of both venae cavae with simultaneous right atrial intra-cavitary cooling reduces atrial activity but is cumbersome. To evaluate pharmacologically-induced atrial arrest using verapamil, bipolar ventricular and right atrial electrograms were recorded in 12 dogs during one hour of hyperkalemic hypothermic cardioplegic arrest and cardiopulmonary bypass using single caval cannula. Group I (n = 6) received hyperkalemic hypothermic cardioplegic solution (4 degrees C) (20 mEq/1 K+) with verapamil (1 mg/L) by intermittent intra-aortic infusion during systemic hypothermia (28 degrees C). Group II (n = 6) received hyperkalemic hypothermic cardioplegia without verapamil. The percentage of time atrial activity was present (greater than 10 beats/min) in Group I, was significantly less than in Group II. Similarly the total number of atrial beats in Group I was less than in Group II. Recovery of normal sinus rhythm during reperfusion was prolonged in Group I in comparison to Group II. Verapamil induces significant and persistent atrial suppression during hyperkalemic hypothermic cardioplegic arrest but prolongs recovery of normal sinus rhythm during reperfusion. It remains to be established clinically whether verapamil-induced atrial suppression is associated with less postoperative supraventricular tachyarrhythmia. The potential disadvantage of prolonged sinus node recovery time must also be assessed.
Can J Cardiol
PMID:Persistent atrial activity during cardioplegic arrest: suppression by verapamil. 376 89

Reperfusion of an isolated heart with a calcium-containing solution after a short calcium-free perfusion may result in irreversible cell damage: the calcium paradox. In this investigation the effect of hypothermia during reperfusion with calcium-containing solution on the calcium paradox damage in the isolated rat heart was studied. In addition, the effect of pre-cooling the heart during the calcium-free period was investigated. Creatine kinase release was used to define cell damage. Normothermic (37 degrees C) calcium-free perfusion followed by normothermic reperfusion with calcium-containing solution resulted in a massive release of CK. When the normothermic calcium-free perfusion was followed by hypothermic (10 degrees C) calcium-containing reperfusion, CK release was reduced by 20% (P less than 0.005). This CK release during reperfusion was further reduced by 55% and 80% when the normothermic calcium-free perfusion was followed by 5 or 10 min respectively of hypothermic calcium-free perfusion prior to the hypothermic calcium-containing reperfusion. The results show that hypothermia during the period of calcium repletion retards the sequence of events which ultimately results in release of large amounts of intracellular components.
Basic Res Cardiol
PMID:The effect of hypothermia during the period of calcium repletion on the calcium paradox. 377 21

New 2-site labeled monoclonal antibody techniques were used to measure serially plasma levels of brain-type creatine kinase (CK-BB), heart-type creatine kinase (CK-MB) and muscle-type creatine kinase (CK-MM) during a 20-hour postoperative period in 24 infants after deep hypothermia and total circulatory arrest used in pediatric cardiac surgery. A control group of 7 children undergoing cardiovascular procedures without extracorporeal circulation or circulatory arrest also were studied. There were marked increases in CK-MB and CK-BB levels in the circulatory arrest group but not in the closed group. CK-BB increased from 3.2 +/- 0.5 to 27 +/- 10 ng/ml and CK-MB from 5.9 +/- 2.1 to 137 +/- 12 ng/ml. The CK-MM concentrations increased from 299 +/- 91 and 194 +/- 49 ng/ml to 1,220 +/- 274 and 1,322 +/- 142 ng/ml in the closed and circulatory arrest groups, respectively. Peak levels of CK-MB and CK-BB occurred an average of 133 and 127 minutes, respectively, after reperfusion. The half-time of CK-BB differed significantly from that of CK-MB (149 +/- 15 vs 359 +/- 20 minutes). The arrest time had a more marked effect on CK-BB concentration than on CK-MB and CK-MM concentrations. Arteriointernal jugular venous concentration differences were consistently negative for CK-BB in the circulatory arrest group, but not for CK-MM and CK-MB.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Cardiol 1986 Dec 01
PMID:Detection of cerebral injury after total circulatory arrest and profound hypothermia by estimation of specific creatine kinase isoenzyme levels using monoclonal antibody techniques. 378 13

We report a patient presenting with a pseudo-aneurysm arising from the extra-cardiac conduit and dehisced intra-cardiac patch following the Rastelli procedure. Since the aneurysm was adherent to the sternum, re-operation was facilitated by establishing extra-thoracic cardio-pulmonary bypass and hypothermia before opening the chest.
Int J Cardiol 1986 Nov
PMID:Pseudo-aneurysm formation complicating the Rastelli procedure. 379 82

The post-operative review of 81 patients operated for a large interventricular communication before the age of two years reveals excellent results: the mean age at operation was 7 months, extracorporeal circulation was performed in 25 patients for a mean duration of 77 minutes and profound hypothermia to 18 degrees C was induced in 56 patients. The atrial approach was used in 30% of cases. The mean follow-up period is 26 months. There was one case of complete bundle branch block, which was subsequently fitted with a pacemaker, 7 cases of bifascicular branch block and a right bundle branch block in the majority of cases. The pulmonary vascular resistance was virtually normal (a mean of 3.2 U.m-2 prior to the operation and a mean of 1.9 U.m-2 after the operation). The left ventricular volume, which was markedly increased in all patients preoperatively, returned to normal with maintenance of a normal ejection fraction. The neuro-psychomotor behaviour was abnormal in 13 of the 63 patients tested. These abnormalities are not related to the correction procedure, but to pre-existing pathology (small birth weight). 52 patients from a series of 63 cases operated for tetralogy of Fallot before the age of 2 years (median age 12 months) were also reviewed. Extracorporeal circulation lasting a mean of 115 minutes was performed in 31 patients, cardiac arrest under profound hypothermia was induced in the other cases, for a mean duration of 61 minutes. The mean follow-up period was 29 months.(ABSTRACT TRUNCATED AT 250 WORDS)
Ann Cardiol Angeiol (Paris) 1985 Jan
PMID:[Results of the intracardiac repair of tetralogy of Fallot and interventricular communication before the age of 2 years]. 397 71

A marked increase in left ventricular diastolic pressure ( PLVD ) relative to volume is regularly observed during angina pectoris and may contribute to further deteriorations of myocardial perfusion in the ischemic myocardium and to pulmonary congestion as well. A possible simultaneous increase in myocardial oxygen consumption (MVO2) due to a reversible diastolic tone during transient ischemia has not been taken into consideration in previous studies on alterations in ventricular diastolic properties. 13 closed-chest experiments were carried out in clinical catheterization technique with situations of high PLVD (18-50 mm Hg) relative to volume induced by right ventricular pacing (n = 19; 172 +/- 5 beats/min) and catecholamine-induced reversible diastolic tone (n = 17) in moderate hypothermia (31 degrees C). MVO2 was directly measured and indirectly calculated from its hemodynamic determinants using Bretschneider's equation (Et) that does not consider ventricular diastolic pressure. In addition, an energy demand for maintenance of active diastolic wall tension (E5) was calculated from PLVD , mean ventricular diastolic volume estimated from endsystolic and stroke volume, diastolic time and heart rate in ml O2/min X 100 g. During pacing tachycardia with high PLVD (27.4 +/- 1.8 mm Hg) the MVO2 (12.49 +/- 0.50 ml O2/min X 100 g) exceeds Et (10.11 +/- 0.25 ml O2/min X 100 g) (p less than 0.001), partly due to neglect of E5 (1.39 +/- 0.11 ml O2/min X 100 g). During catecholamine-induced high PLVD (31.1 +/- 2.5 mm Hg) the MVO2 (12.29 +/- 0.83 ml O2/min X 100 g) increases significantly (p less than 0.001) over Et (10.43 +/- 0.81 ml O2/min X 100 g). Addition of E5 (1.76 +/- 0.14 ml O2/min X 100g) to Et abolishes the differences between MVO2 and Et yielding non-significantly different values. Results indicate by means of indirect energetic evidence the occurrence of a diastolic tone of the heart under unphysiologic conditions. Acute increases in PLVD during angina pectoris are supposed to increase MVO2 markedly due to an additional energy demand for maintenance of reversible active diastolic wall tension.
Basic Res Cardiol
PMID:Increase of myocardial oxygen consumption due to active diastolic wall tension. 614 4

The effect of diltiazem on creatine kinase release and tissue adenosine triphosphate content was investigated during calcium paradox in the isolated perfused rat heart. Creatine kinase loss was minimal during the calcium-free phase, but there was a 100-fold increase in creatine kinase release after reperfusion with normal calcium-containing medium. Diltiazem reduced creatine kinase loss by 35 percent when added to calcium-free medium and by approximately 80 percent when added to both calcium-free and reperfusion media. Adenosine triphosphate content was significantly increased from 2.98 mumol in untreated calcium paradox hearts to 5 mumol/g dry weight in diltiazem-treated hearts. With hypothermia the calcium paradox injury was completely inhibited if the temperature of calcium-free perfusion was maintained at 15 degrees C. Diltiazem appears to exert its protective effect through its ability to prevent the cellular separation and alterations in the gap junctions during calcium deprivation of cells and to limit calcium entry into the cells after reperfusion with calcium-containing medium.
Am J Cardiol 1982 May
PMID:Prevention of calcium paradox-related myocardial cell injury with diltiazem, a calcium channel blocking agent. 628 3

Recently, the use of calcium antagonists has been proposed as a new cardioplegic principle. At high doses (e.g. 10(-6)M nifedipine [3]) these drugs can be used for induction of reversible cardiac arrest. Apart from their effect on coronary flow, calcium antagonists seem to be beneficial to ischemic tissue because of their negative inotropic effect at high doses [6, 9]. Ionic cardioplegic solutions are commonly used in an advantageous combination with hypothermia. In the case of calcium antagonists, there is an indication that the specific cardioprotective effect is lessened at low temperatures [3]. Nifedipine is known to reduce contraction force without abolishing the generation of action potentials even at excessive doses [2]. To quantify the suppressing effect of nifedipine on the generation of contractions, we determined the maximal possible contraction frequency (Fm) under electrical stimulation at different temperatures. In isolated myocardial cells, Fm can be determined from the cell contour movements even with an almost complete force reduction and therefore it represents a measure for effective contractile refractoriness.
J Mol Cell Cardiol 1984 Mar
PMID:Temperature dependence of nifedipine action. 671 93


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