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

One hundred seven patients undergoing coronary artery bypass grafting were randomized to receive warm antegrade (n = 21), warm retrograde (n = 22), cold antegrade (n = 20), cold retrograde (n = 22), or intermittent cold antegrade (n = 22) blood cardioplegia. Myocardial oxygen consumption and lactate production, adenine nucleotides, and adenine nucleotide degradation products were measured during the operation, and creatine kinase-MB release was assessed postoperatively. Warm cardioplegia resulted in greater myocardial lactate production than cold cardioplegia (p = 0.048). Retrograde cardioplegia was associated with greater lactate production than antegrade cardioplegia (p = 0.015). Adenosine triphosphate depletion was similar among groups. However, poorly diffusible metabolites of adenosine triphosphate accumulated to the greatest extent in the intermittent cold group. Levels of hypoxanthine were highest after warm retrograde cardioplegia. Operative mortality and morbidity were low and were not different among groups. In summary, none of the five techniques of cardioplegia evaluated in this study was able to completely prevent myocardial ischemia. Anaerobic lactate production was minimized with cold cardioplegia and with antegrade cardioplegic delivery. Hypothermia may have impaired regeneration of adenosine triphosphate, however, particularly in association with inadequate or intermittent cardioplegic flow.
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PMID:Which techniques of cardioplegia prevent ischemia? 823 94

Both clinical and laboratory studies are being undertaken to investigate the deleterious neurologic and developmental effects associated with cardiopulmonary bypass, hypothermia, and circulatory arrest in the neonate and infant. A prospective, randomized clinical study of 171 neonates and young infants compared circulatory arrest with low-flow bypass (50 mL.kg-1.min-1). Circulatory arrest was associated with a higher incidence of early postoperative seizures as well as greater release of creatine kinase-BB. There was a strong correlation between duration of circulatory arrest and seizures (p = 0.004). The late consequences of these findings will be known at the completion of developmental assessment of all patients at 1 and 4 years of age. Laboratory studies have used a miniature piglet model that closely replicates clinical circulatory arrest. High-energy phosphate stores determined by magnetic resonance spectroscopy were maintained in animals undergoing 1 hour of low-flow bypass but became undetectable after 32 minutes of a 1-hour period of circulatory arrest. However, they returned to baseline within 3 hours of reperfusion as did cerebral blood flow and metabolism determined by microsphere studies. Piglets undergoing 1 hour of circulatory arrest showed more rapid recovery of cerebral adenosine triphosphate content and intracellular pH when managed with the pH-stat strategy during hypothermic bypass than with the more alkaline alpha-stat strategy. Other laboratory studies have examined pharmacologic methods of reducing cerebral injury associated with circulatory arrest including aprotinin, anti-CD18, neuronal receptor antagonists (MK801, NBQX), and blockade of glutamate release with adenosine in a cerebroplegia solution. These studies have suggested a number of promising approaches to improving the technique of circulatory arrest.
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PMID:Review of current research at Boston Children's Hospital. 826 70

Potassium loss may cause arrhythmias and cardiac injury in patients undergoing heart surgery with cardiopulmonary bypass (CPB). In a prospective, randomized trial two different methods of potassium substitution were investigated regarding their influence on cardiac rhythm following reperfusion. Patients received either potassium chloride (Group I, n = 102) or potassium magnesium aspartate (Inzolen, group II, n = 105) to achieve intraoperative serum potassium concentrations of 4.5 mmol/l. St. Thomas cardioplegic solution was used. CPB was performed in moderate hypothermia (28-32 degrees C) with a non-pulsatile pump flow, a membrane oxygenator and a single two-stage venous catheter. The two study groups were comparable with regard to biometric data, preoperative state, duration of operation, ischemia and clinical outcome. In 6 patients in group I and in 3 patients in group II perioperative myocardial infarction was diagnosed based on ECG and CK-MB findings. One patient in each group died during the postoperative hospital stay. At the time of declamping mean serum potassium concentration was 4.9 +/- 0.7 mmol/l in group I and 4.8 +/- 0.5 mmol/l in group II (n.s.). The concentration of magnesium was significantly lower in the potassium chloride substitution group (1.48 mmol/l) compared to the other group (2.33 mmol/l) (p < 0.05). No significant differences in cardiac electric activity were observed between the two groups. The incidence of ventricular fibrillation in the early reperfusion period was 37% versus 45% (n. s.). In both groups patients with a potassium value of < 4.5 mmol/l showed a significantly higher incidence of ventricular fibrillation. Five percent of the patients had bradycardia requiring temporary pacing.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Potassium substitution during coronary surgery: K(+)-Mg+(+)-aspartate-complex (Inzolen) versus potassium chloride]. 829 48

We determined the influence of perfusate composition and reinfusion during ischemia upon myocardial protection in the immature rabbit heart. Isolated "working" hearts (n = 6 per group) from 7-10-day-old New Zealand White rabbits were perfused with Krebs bicarbonate buffer and function measured. Hearts were then arrested with 3 minutes cold (14 degrees C) perfusion with bicarbonate buffer (as hypothermia-alone group) or St. Thomas' II cardioplegic solution (as hypothermia-plus-cardioplegia group). Hearts were then subjected to hypothermic (14 degrees C) global ischemia for 2 or 6 hours, with and without multiple reinfusion of the coronary vasculature. Following 2 hours ischemia impaired recovery of aortic flow occurred after multiple reinfusion in comparison with a single infusion with the cardioplegic solution (64 +/- 3% versus 72 +/- 4%) but not with bicarbonate buffer (79 +/- 3% versus 83 +/- 4%). However after 6 hours ischemia impaired recovery of function occurred after multiple reinfusion in comparison with single infusion both with the cardioplegic solution (60 +/- 3% versus 68 +/- 3%) and with bicarbonate buffer (57 +/- 4% versus 75 +/- 5%). There were no differences in post-ischemic creatine kinase leakage or myocardial water content between groups. These results suggest (i) that reinfusion itself, regardless of the composition of the perfusate, caused decreased recovery of function after an extended period of ischemia, and (ii) protection of the ischemic immature heart with St. Thomas' II solution remains inadequate and requires improvement.
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PMID:Protection of the ischemic immature heart--effect of perfusate reinfusion and composition. 830 94

The effects of diltiazem, a sarcolemmal Ca2+ channel blocker, and ryanodine, an inhibitor of sarcoplasmic reticulum function, were investigated in isolated newborn rabbit hearts (2 to 5 days old) subjected to ischemia and reperfusion. After cardioplegic arrest with St. Thomas' Hospital solution, global ischemia was induced at 37 degrees C (normothermia) for 45 minutes or at 20 degrees C (hypothermia) for 180 minutes. The hearts were then reperfused at 37 degrees C for 30 minutes. Diltiazem or ryanodine, at concentrations that have minimal to moderately negative inotropic effects under nonischemic conditions, was added to the cardioplegic solution. After normothermic ischemia, reperfusion of untreated hearts resulted in recovery of left ventricular developed pressure to 52.9% +/- 2.5% of the preischemic level. In hearts treated with diltiazem, recovery of left ventricular developed pressure was significantly improved (84.2% +/- 2.9% at 3 x 10(-8) mol/L; p < 0.01). Comparable improvement was achieved with ryanodine (90.5% +/- 4.1% at 10(-9) mol/L; p < 0.01). Creatine kinase leakage and structural derangement of mitochondria were also reduced by both agents. With hypothermic ischemia, left ventricular developed pressure recovered in untreated hearts to 72.7% +/- 3.3% of preischemic values. Treatment with diltiazem improved the recovery of left ventricular developed pressure to 96.9% +/- 3.5% at 3 x 10(-8) mol/L and reduced creatine kinase leakage and mitochondrial damage. Ryanodine also improved the recovery of left ventricular developed pressure and attenuated ultrastructural damage. These findings suggest that Ca2+ handling by the sarcoplasmic reticulum, like transsarcolemmal Ca2+ influx, plays an important role in the pathogenesis of myocardial ischemia-reperfusion injury in the neonatal heart despite the morphologic and functional immaturity of the sarcoplasmic reticulum in the neonate.
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PMID:Protective effects of diltiazem and ryanodine against ischemia-reperfusion injury in neonatal rabbit hearts. 832 Oct 5

Retrograde cerebral perfusion (RCP) is used to prolong the safe period of circulatory arrest under profound hypothermia. However, this technique now varies in some maneuvers at different institutions. This study investigated the effects on cerebral metabolism of clamping blood flow through the IVC cannula during RCP using fourteen adult mongrel dogs. During circulatory arrest, RCP by way of the bilateral internal maxillary vein was performed. In seven dogs, blood flow was drained through IVC cannula (IVC-drained group) and in the other seven dogs, the blood flow was clamped during RCP (IVC-clamped group). During RCP, the percent of returned blood volume, oxygen consumption, exudation of carbon-dioxide, and oxygen saturation of the returned blood were significantly higher in the IVC-clamped group than in the IVC-drained group, and the concentration of serum CK-BB in the IVC-clamp group was significantly lower than in the IVC-drained group. However, there was no statistical difference between the two groups concerning the regional cerebral blood flow or water content of the cerebral tissue. Concerning about these results, a part of perfused blood passed through not only the extra cranial veno-venous connection but also the intra cranial veno-capillary-venous connection. We concluded that clamping of the venous blood flow through the IVC cannula during RCP is a more protective procedure for cerebral tissue.
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PMID:[Experimental studies on retrograde cerebral perfusion: efficacy of clamping of the venous blood flow through IVC cannula]. 837 33

Supraventricular tachyarrhythmias following coronary artery bypass grafting are a common cause of postoperative morbidity, with a reported incidence of 10-40%. Two techniques of myocardial protection were assessed to determine their influence on the occurrence of postoperative supraventricular tachyarrhythmias. Group I (n = 82) received cold potassium cardioplegia combined with topical hypothermia and systemic cooling to 28 degrees C. Group II (n = 88) were protected by intermittent aortic cross-clamping with a systemic temperature of 32 degrees C. The overall incidence of atrial fibrillation/flutter was 22.3%. No significant difference was detected in the incidence of clinically important atrial fibrillation/flutter between the two groups [21/82 (25.6%) in group I versus 17/88 (19.3%) in group II, P > 0.25]. There was a positive association with age: in patients over 60 years the incidence of arrhythmias (31.8%) was significantly greater than in those less than 60 years (12.9%), P < 0.01. Sex, cardiopulmonary bypass times, aortic cross-clamp times, number of coronary grafts, end-operative creatine kinase myocardial band isoenzyme, right coronary endarterectomy and perioperative myocardial infarction had no association with the occurrence of postoperative atrial tachyarrhythmias.
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PMID:Atrial fibrillation after coronary artery bypass grafting: a comparison of cardioplegia versus intermittent aortic cross-clamping. 843 Dec 98

Isolated canine hearts were preserved for 6 h at 5 degrees C followed by normothermic reperfusion for 2 h. The dogs were divided into two groups of nine hearts each; group 1 received a nondepolarizing preservation solution in multidose, and group 2 received a single flush of University of Wisconsin (UW) solution. Serum MB-CK and mitochondrial aspartate aminotransferase (m-AAT) concentrations and calcium overload during reperfusion were lower in group 1 than in group 2. At the end of reperfusion, myocardial ATP and total adenine nucleotide concentrations were higher and mitochondrial morphology appeared more intact in group 1 than in group 2. Left ventricular diastolic function was preserved better in group 1 than in group 2. These results suggest that in 6-h heart preservation, a nondepolarizing solution applied in multidose fashion protects the myocardium from the deleterious effects of hypothermia and cardioplegia better than a single flush of UW solution.
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PMID:Comparison of intermittent injection of nondepolarizing solution with a single flush of UW solution for donor heart preservation. 844 26

Deficiency of the enzymes of mitochondrial fatty acid oxidation and related carnitine dependent steps have been shown to be one of the causes of the fasting-induced hypoketotic hypoglycemia. We describe here carnitine-acylcarnitine translocase deficiency in a neonate who died eight days after birth. The proband showed severe fasting-induced hypoketotic hypoglycemia, high plasma creatine kinase, heartbeat disorder, hypothermia, and hyperammonemia. The plasma-free carnitine on day three was only 3 microM, and 92% of the total carnitine (37 microM) was present as acylcarnitine. Treatments with intravenous glucose, carnitine, and medium-chain triglycerides had been tried without improvements. Measurements in fibroblasts confirmed deficient oxidation of palmitate and showed normal activities of the carnitine palmitoyltransferases I and II and of the three acyl-CoA dehydrogenases. A total deficiency of the carnitine-acyl-carnitine translocase was found in fibroblasts using the carnitine acetylation assay (1986. Biochem. J. 236:143-148). This assay has been further simplified by seeking conditions permitting application to permeabilized fibroblasts and lymphocytes.
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PMID:Carnitine-acylcarnitine translocase deficiency with severe hypoglycemia and auriculo ventricular block. Translocase assay in permeabilized fibroblasts. 845 53

Hypothermic alkaline pharmacologic cardioplegia used in pediatric cardiac surgery may be less than satisfactory despite its benefits in adults. We determined whether the pH (7.8) of standard St. Thomas' II cardioplegic solution contributes to inadequate protection of the ischemic immature heart and whether the effect is age-related. Modified hypothermic St. Thomas' II solution (pH range, 4.8 to 8.8) was compared with hypothermic bicarbonate buffer alone (pH 7.25) in protecting the ischemic immature (7 to 10 days old) and mature (12 months old) rabbit heart. Isolated hearts (n = 6 per group) were perfused with bicarbonate buffer, and aortic flow was measured before hypothermic (14 degrees C) ischemia (immature hearts: 4 hours; mature hearts: 3 hours). Hearts were reperfused, and enzyme leakage and recovery of function were measured. In the immature heart, a bell-shaped dose-response profile was observed for pH and recovery of aortic flow but not for postischemic creatine kinase leakage. Optimal recovery of aortic flow (98% +/- 3%) occurred at pH 6.8, which was greater than protection with hypothermia alone (82% +/- 4%; p < 0.05) and standard St. Thomas' II solution (72% +/- 2%; p < 0.05). In the mature heart, a bell-shaped dose-response curve existed for recovery of aortic flow and a U-shaped curve existed for creatine kinase leakage. Again, optimal recovery of aortic flow (84% +/- 5%), which was superior to that with standard St. Thomas' II solution (60% +/- 8%; p < 0.05), and minimal enzyme leakage also occurred at pH 6.8, as did the least enzyme leakage (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Age and protection of the ischemic myocardium: is alkaline cardioplegia appropriate? 845 42


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