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

A new method of myocardial protection, profound selective myocardial hypothermia has been employed in order to avoid the effects of cardiac ischaemia during aortic cross clamping in the course of operations undertaken under extracorporeal circulation. It consists of the irrigation of the aortic root immediately after cross clamping with 4 liters of Ringer Lactate at 4 degrees C which perfuses the entire coronary bed and induces complete uniform profound coling of the intrapericardial mass to a temperature of approximately 10 degrees C with resultant flat electrocardiogram and cessation of all electrical activity of the myocardium. This inactivity remains complete until the aorta is unclamped permitting reoxygenation and rewarming of the heart with resumption of its function. This method has been used in the course of 250 cardiac procedures involving the use of extracorporal circulation including 177 valve replacements, either aortic or mitral and aortic, 54 saphenous vein bypass procedures, either simple or with valve replacement and 19 other assorted procedures including cardiac transplantation and complex congenital malformations. Thermal, electrocardiographic, hemodynamic, histologic, histochemical and enzymatic observations have proven the minimal significance of the ischemic lesions produced in hearts protected in this manner. The total mortality was 6.4% which proves the value of this method and its superiority over the 2 techniques most often used at the present time, coronary perfusion or topical myocardial hypothermia according to Shumway's method.
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PMID:The prevention of myocardial ischaemia by the method of profound selective myocardial hypothermia during open heart surgery. 37 37

There are 2 competing methods for cooling the kidney in situ during surgical ischemia: from without by applying ice to the renal surface and from within by perfusing the renal artery. The latter procedure is said to be superior in protecting renal function. Herein the protective effect on renal function of both methods are compared. Pigs of 15--25 kg weight underwent nephrectomy on one side. The remaining kidney was subjected to cold ischemia during 90 minutes while perfusion- or surface cooling was performed. For perfusion cooling the aorta was punctured and the catheter introduced into the renal artery. The perfusing liquid consisted of a physiologic electrolyt solution (Ringer-Lactate) with heparin kept at a temperature of 3--5 degrees C. The initial perfusion lasted 10 minutes and resulted in a median renal core temperature of 23 degrees C. Then the kidney was put on a cooling pad and every 15 minutes again perfused for one minute. For surface cooling sterile melting ice made of glucose solution 5% was applied directly to the kidney. The renal core temperature could be kept at 15--20 degrees C. The two methods of hypothermia were judged by comparing the serum creatinine levels and the I131-hippuran clearances one month after surgery. There was no difference whatever as analysed by the t-test. Hypothermia by applying ice to the renal surface therefore proved to be equivalent to hypothermia by perfusion. Moreover it is much simpler.
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PMID:[Renal hypothermia in situ. Comparison between surface and perfusion cooling concerning renal function in pigs (author's transl)]. 41 41

Myocardial protection by a combination of cardiac hypothermia and chemical cardioplegia (high concentration of K+ and Mg++, hyperosmolarity, acid pH), was studied during 20 valve replacements. Essentially assessed on the basis of repeated measurements of postoperative cardiac output, the results were compared with those obtained previously using local hypothermia only (20 patients) and hypothermic cardioplegia using Ringer Lactate (20 patients). Analysis of haemodynamic data, which thus involved 60 patients, indicated the superiority of physicochemical cardioplegia, and this for clamping periods of up to 2 hours, but also showed the desirability of changes in the protection protocol during the ischaemia phase and during reperfusion which might improve the results.
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PMID:[Postoperative haemodynamic evaluation of myocardial protection by physicochemical cardioplegia. Hyperkaliemic, hyperosmolar and acid solution at 4 degrees C (author's transl)]. 48 1

Total body washout (hct less than 1%) in hypothermia was performed in 31 dogs using either a crystalloidal or a colloidal perfusate. Blood exchange and cooling was achieved by means of partial bypass and heat exchanger. Short lasting blood exchange for crystalloids without cardiac arrest resulted in 66% survival of the animals. When in addition circulatory arrest was established for 30 min at 14 degrees C oesophageal temperature blood exchange for crystalloids was not tolerated. All four animals of this group died within 19 hours presenting massive interstitial edema. Replacement of the crystalloidal perfusate by a colloidal solution (2.5 g% Dextran 60 at Ringer's Lactate) and establishing circulatory for 30 or 60 min resulted in survival rates of 71% and 50% respectively. The use of the colloidal perfusate effectively prevented edema formation. Death could not be correlated with the parameters controlled.
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PMID:[Hypothermic circulatory arrest after total blood exchange in dogs (author's transl)]. 68 88

We compared moderate (29 degrees C.) and profound (5 degrees C.) (ice chips) cardiac hypothermia for myocardial preservation during aortic cross-clamping for 30 or 60 minutes in a canine right heart bypass preparation. Ventricular function deteriorated significantly at 29 degrees C. but not at 5 degrees C. Maximum dp/dt declined only after 60 minutes of ischemia at 29 degrees C., and Vmax decreased after one hour at either temperature. Lactate and pyruvate washout were greater after 29 degrees C., and pyruvate production persisted after 60 minutes of ischemia at 29 degrees C. Reactive hyperemia was greater after 30 minutes of ischemia at 29 degrees C. Reactive hyperemia was greater after 30 minutes of ischemia at 29 degrees C., and total coronary flow remained elevated after 60 minutes of ischemia at 29 degrees C. Coronary flow distribution was not altered by hypothermia. Ultrastructural changes were primarily time dependent and not temperature dependent. Ice-induced subepicardial injury was not evident in the ultrastructure or by flow distribution. Sixty minutes of profound topical cardiac hypothermia is moderately well tolerated by the canine heart, but functional and structural alterations are evident.
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PMID:Topical cardiac hypothermia for myocardial preservation. 87 Jul 64

Difficulties persist in providing optimum myocardial protection to neonatal hearts undergoing congenital cardiac repair. Controversy on actual ischemic sensitivity of neonatal hearts compared to adult hearts may depend on species, age selected, and conditions of the experimental protocol. In 1985, our laboratory began to investigate this area using the time to ischemic contracture (TIC) model popularized by Hearse and Wechsler and reported that neonates developed TIC in a significantly shorter time than adult hearts. The neonatal heart had rapid lactate accumulation and early rapid decline in glycogen that was not sustained. This led to ATP decline and triggered TIC. The adult heart had a more gradual lactate accumulation with complete glycogen utilization. As a result ATP stores were maintained longer, which prolonged TIC. Neonatal hearts demonstrated sensitivity to alterations in extracellular calcium and only minimal additional detrimental effects of ventricular fibrillation (VF) on TIC. More complete glycogen utilization and a greater tolerance to ischemia was noted in the neonates when constant washout was provided by removing tissue metabolites (Lactate). In neonates moderate hypothermia (25 degrees C) and deep hypothermia of varying levels (19 degrees C, 12 degrees C) demonstrated that lactate accumulation was significantly less than normothermia and ATP decline was slowed. A subgroup of hearts had 40%-50% lower ATP stores before ischemia and significantly shorter TIC. These "at risk" hearts do not have the same safe time for surgical repair. Further developments will result in improved outcomes for this young patient population.
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PMID:Age-related differences in myocardial metabolism affects response to ischemia. Age in heart tolerance to ischemia. 152

Levine-prepared, female Sprague-Dawley rats were used to investigate the effects of carbon monoxide (CO) and cyanide (CN) on heart rate, blood pressure, hematocrit, body temperature, blood glucose, lactate, and neurologic function. Rats were exposed to either 2400 ppm CO, 1500 ppm CO, 4 mg/kg NaCN, or both 1500 ppm CO and 4 mg/kg NaCN for 90 min, followed by 4 h of room air recovery. Following exposure to 2400 ppm CO, rats exhibited a significant bradycardia which normalized by 2 h of recovery. All groups exhibited an initial hypotension which was either maintained or exaggerated during exposure in all but the rats exposed to CN, and which returned to pre-exposure values by 90 min. All groups experienced a significant hypothermia during the exposure period, with those in the 1500 ppm CO or the CN returning to initial values over the recovery period. The only significant change in hematocrit was due to 2400 ppm CO (4.1% increase). During exposure, all groups experienced an initial surge in glucose concentration which was maintained in all but rats exposed to 2400 ppm CO. The greatest hyperglycemic response resulted from the combination of CO and CN, whereas 2400 ppm CO produced the smallest. CN alone produced no significant rise in lactate concentration. However, lactate concentration in all other groups was significantly elevated during the exposure period, returning to initial values by 4 h of recovery. Lactate concentrations and neurologic deficit in rats exposed to 1500 ppm CO, when added to those rats treated with CN, closely approximated the lactate and neurologic deficit of the combination treatment. Neurologic deficit was greatest in rats exposed to 2400 ppm CO. While in most cases the responses of the rats to CO and CN differed whether the substances were administered alone or in combination, a synergistic relationship is not suggested. An additive or less than additive relationship is more likely.
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PMID:Cardiovascular, metabolic and neurologic effects of carbon monoxide and cyanide in the rat. 164 71

The rapid infusion system (RIS), which can deliver fluids/blood products rapidly at precise rates and normothermic conditions, was compared with conventional fluid administration (CFA) in a randomized study of 36 hypovolemic trauma patients. Admission stratification criteria of the groups were similar relative to age, Glasgow Coma Score (GCS), Injury Severity Score (ISS) and plasma lactate. Despite the lack of difference in blood loss between the 24-h survivors of the two groups, the CFA group required greater total fluids (23.6/20.21), red blood cells (5.5/4.61), fresh frozen plasma (FFP) (2.8/1.91), platelets (523/204 ml), and crystalloids (12.9/10.61). Lactate levels were lower in the RIS group at virtually all times from hours 1 to 24 (4.3/5.3 mM/l, t-value = 3.3, DF = 279, P = 0.001). Post-admission hypothermia was greater in the CFA group at all times during the first 24 h (35.2/36.4 degrees C, t-value = 5.6, DF = 250, P = 0.001). The mean partial thromboplastin time was significantly higher in the CFA group (47.3/35.1 s, t-value = 3.1, DF = 279, P = 0.002). The PTT and PT were related to the degree of lactic acidosis (P = 0.0001) and hypothermia (P = 0.001) but not to the amount of FFP given (P = 0.14). The hospital costs, days in the ICU, and days on the ventilator were greater for the CFA group, as was the incidence of pneumonia (0/11 vs. 6/17; P = 0.03). Hypovolemic trauma patients resuscitated with the RIS needed fewer fluid/blood products and had less coagulopathy; more rapid resolution of hypoperfusion acidosis; better temperature preservation; and fewer hospital complications than those resuscitated with conventional methods of fluid/blood product administration.
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PMID:The rapid infusion system: a superior method for the resuscitation of hypovolemic trauma patients. 165 23

Despite various techniques of hypothermia it is still difficult to provide optimal myocardial preservation in neonatal cardiac surgery. The early effects of moderate and deep hypothermia were examined in neonatal pig hearts by studying metabolism over time and the tolerance of the hearts to global ischemia. The latter was measured by the time to onset of ischemic contracture, an indicator of irreversible ischemic damage. After control right ventricular biopsies were done, 56, 3-day-old neonatal hearts were excised and placed in one of four temperature-regulated baths (37 degrees C, 25 degrees C, 19 degrees C, 12 degrees C). A compliant left ventricular balloon measured onset time to ischemic contracture (TIC) (2 mm Hg increase in pressure). Biopsies were also done at 15 and 30 minutes of ischemia. Progressive hypothermia significantly (p less than 0.001) prolonged TIC but resulted in an increased standard error of the mean (SEM). Lactate accumulation was the least in deep hypothermia (12 degrees C, 19 degrees C) (p less than 0.05) and intermediate with moderate hypothermia (25 degrees C), and all were less (p less than 0.01) than that at normothermia. The decline of adenosine triphosphate was slowed more by hypothermia than normothermia. These observations can be used to improve current methods of myocardial preservation in neonatal hearts.
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PMID:Comparison of mild and deep hypothermia: do they provide similar protection in all neonatal hearts? 186 86

Hypothermia often occurs in association with clinical conditions involving severe hypoglycemia, but its effect on embryonic development has not been well evaluated. Thus, the whole embryo culture method was used to expose day 9 (neurulating) and day 10 (early limb bud stage) mouse embryos to physiologic levels of hypothermia (35 degrees C and 32 degrees C) for 4 and 24 hr. Embryos were evaluated after 24 hours for growth and malformations and compared with controls grown at 37 degrees C. Lactate production was measured in embryos cultured for 4 hr at 32 degrees C and compared with those cultured at 37 degrees C. A 4-hr exposure to hypothermia produced little effect morphologically but reduced the rate of lactate production at both embryonic stages. A 24-hr exposure to hypothermia at 35 degrees C or 32 degrees C produced growth retardation and dysmorphogenesis in embryos undergoing neurulation. Early limb bud stage embryos were less sensitive to this treatment, with growth retardation produced only at the lower temperature. Since hypothermia is commonly associated with severe hypoglycemia in cases of diabetic insulin overdose, day 9 (neurulating) mouse embryos were exposed concurrently to short periods of hypothermia and hypoglycemia and compared with embryos cultured in hypoglycemic medium at normal temperature. The results demonstrate that hypothermia partially protects embryos against the dysmorphogenic effects of hypoglycemia. A balance of metabolic rate and available substrate is discussed as a possible mechanism for this protective effect.
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PMID:Hypothermia: teratogenic and protective effects on the development of mouse embryos in vitro. 188 54


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