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

The purpose of this study was to investigate the value and to identify any deleterious effects of antishock trouser use during hypothermic cardiovascular depression. Thirteen mongrels were made hypotensive by cooling to a core temperature of approximately 27 degrees C. Eight dogs had antishock trousers inflated for one hour and five dogs served as controls. Metabolic and hemodynamic variables were measured at regular intervals during cooling, during trouser inflation, and after trouser deflation. No study animal experienced ventricular fibrillation. Neither central temperature, pH, or serum potassium nor mean arterial BP or systemic vascular resistance were significantly affected by trouser inflation or deflation. Antishock trouser use during the early phase of hypothermia before rewarming does not appear to result in a central bolus of cold, acidotic, hyperkalemic blood or the precipitation of ventricular fibrillation. There appears to be no significant hemodynamic benefit of antishock trouser use early in the management of hypotension caused by moderate hypothermia.
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PMID:The effects of antishock trouser inflation during hypothermic cardiovascular depression in the canine model. 317 51

This study reviews the outcome of 17 hypothermic patients air evacuated by a civilian helicopter transport service. Age (33 +/- 23), type and duration of exposure, and rewarm methods were examined for each patient. Temperature (T), heart rate (HR), blood pressure (BP), respiratory rate (RR), Glasgow coma score (GCS), trauma score (TS), CRAMS score (CS), and cardiac rhythm in the pre-hospital setting and in the emergency department (ED) were compared to outcome. Eight of the patients had extensive exposure to a cold environment ranging from 4 h to 10 d. The remaining 9 patients were exposed to cold water ranging from 15 min to 4.5 h. By severity of hypothermia as measured in the ED, 6 patients who were hypothermic at the scene were normothermic (t greater than 35 degrees C), 5 patients were classified as mild (t = 35-31.5 degrees C), 3 as moderate (T less than 31.5-25.5 degrees C), and 3 patients were severely hypothermic (T less than 25.5 degrees C). The GCS, TS, and CS were not indicative of outcome. During rewarming, 3 patients had paradoxical temperature drops, and 5 patients had atrial fibrillation. Three patients required cardiopulmonary resuscitation in the field. Two were discharged with resolving disabilities, and 1 expired. No ventricular fibrillation or J waves occurred. All patients were effectively rewarmed without incident. All patient disabilities and the single fatality were not directly related to hypothermia. There were no long-term adverse consequences of helicopter transport in these hypothermic patients.
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PMID:A retrospective analysis of air-evacuated hypothermia patients. 320 89

We investigated the relationship between electrical alternans and cardiac electrical stability in a series of 20 dog experiments and in a pilot clinical study. Electrical alternans was detected in both the QRS complex and the ST-T wave by use of a novel multidimensional spectral technique. The magnitude of the alteration was expressed as the alternating electrocardiographic morphology index (AEMI), expressed as parts per million of waveform energy. Electrical stability in the dog preparations was assessed via the ventricular fibrillation threshold measurement, and in the clinical studies via programmed stimulation. In 10 dog experiments, systemic hypothermia resulted in a 60% decrease in ventricular fibrillation threshold (VFT) (p less than .0001) and a significant increase in both AEMI(QRS) form 3.7 +/- 3.0 to 1448 +/- 548 (p less than .0001) and AEMI(ST-T) from 43.9 +/- 18.4 to 19,178 +/- 5579 (p less than .0001). In 10 dog experiments, transient coronary artery ligation also resulted in a 60% decrease in VFT (p less than .0001), an increase from 76.3 +/- 46.5 to 245 +/- 11 in AEMI(QRS) (p less than .05), and an increase from 842 +/- 505 to 1365 +/- 392 in AEMI(ST-T) (p less than .002). In 119 observations in 20 animal experiments, the rank correlation between VFT and AEMI(QRS) was -.30 (p less than .001), with that between VFT and AEMI(ST-T) being -.55 (p less than .0001). In a double-blind pilot clinical trial consisting of 23 studies in 19 patients, the result of electrophysiologic testing was used as an independent measure of cardiac electrical stability. Alternation in waveform morphology identified the inducible patient population with a sensitivity of 92%, a positive predictivity of 70%, and a specificity of 50% (p less than .05). We conclude that analysis of subtle beat-to-beat variability in electrocardiographic morphology may provide a noninvasive measure of cardiac electrical stability.
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PMID:Electrical alternans and cardiac electrical instability. 333 62

Hypothermia to less than 30 degrees C is associated with significant harmful effects, including ventricular fibrillation. None of the currently used techniques for core rewarming is entirely satisfactory. Continuous perfusion of the pleural space with warm saline solution has been studied as a method of core rewarming. Pigs were cooled to 28 degrees to 30 degrees C. The pleural space was continuously perfused with fluid at a temperature of 42 degrees C. Five hypothermic control pigs did not achieve a temperature of 32 degrees C in 3 hours of spontaneous rewarming. The rise in 1 hour was 0.34 degrees C. In 10 pigs that underwent continuous pleural perfusion the temperature exceeded 32 degrees C in a mean time of 56 minutes. The rise in temperature in the first hour of rewarming was 5.05 degrees C. Continuous pleural perfusion is a rapid and effective technique for core rewarming of the hypothermic pig.
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PMID:Correction of hypothermia by continuous pleural perfusion. 336 90

A case of cardiac arrest following hypothermia due to cold-water immersion is presented. Following rescue and initiation of cardiopulmonary resuscitation, the patient was transported by helicopter to a facility where rewarming using cardiopulmonary bypass was possible. Initial rectal temperature in the emergency department was 28 degrees C. Initial prehospital rhythm was ventricular fibrillation persisting approximately 1.5 hours until the patient was successfully cardioverted after 25 minute of femoral artery/femoral venous partial cardiopulmonary bypass rewarming. Temperature at the time of cardioversion was 30 degrees C (esophageal). Despite extended cardiac arrest and profound metabolic acidosis (pH = 6.41 at 37 degrees C), he recovered uneventfully and is neurologically normal. A protocol for the management of a patient with hypothermic cardiac arrest is included.
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PMID:Resuscitation of the hypothermic patient. 341 44

Current basic life support (BLS) protocols do not address the physiologic effects of accidental hypothermia in prehospital care. The extreme levels of bradycardia, bradypnea, and peripheral vasoconstriction that often accompany profound hypothermia may complicate the accurate diagnosis of cardiopulmonary arrest in the unmonitored patient. Although CPR is indicated in the truly pulseless, apneic victim of hypothermia, chest compressions may convert nonpalpable but adequately perfusing sinus bradycardia to ventricular fibrillation. This dilemma had led to disagreement among clinicians and researchers in hypothermia about prehospital care protocols for the severely hypothermic patient. This article reviews the controversy and recommends the application of a normal BLS protocol to hypothermic patients presenting in apparent cardiopulmonary arrest.
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PMID:Cardiopulmonary resuscitation and hypothermia. 353 62

Canoeing and kayaking are upper-body sports that make varying demands on the body, depending on the type of contest and the distance covered. The shorter events (500 m) are primarily anaerobic (2 minutes of exercise), calling for powerful shoulder muscles with a high proportion of fast-twitch fibres. In contrast, 10,000 m events call for aerobic work to be performed by the arms. Such contestants need a high proportion of slow-twitch fibres, and an ability to develop close to 100% of their leg maximum oxygen intake when paddling. In slalom and whitewater contests, the value of physiological testing is somewhat limited, since performance is strongly influenced by experience and the ability to make precisely judged rapid paddling efforts under considerable emotional stress. Paddlers face dangers from their hostile cold water environment; causes of fatalities (drowning, cardiac arrest, ventricular fibrillation and hypothermia) are briefly reviewed. Medical problems include provision of adequate nutrition and a clean water supply, effects of repeated immersion (softening of the skin, blistering, paronychial infections, sinusitis, otitis), varicose veins (secondary to thoracic fixation) and hazards of exposure to fibreglass and polystyrene in the home workshop. Surgical problems include muscle sprains and mechanical injuries (haemotomas, lacerations, contusions, concussion, and fractures).
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PMID:Science and medicine of canoeing and kayaking. 354 36

Although many studies of the protective effects of cardioplegic solutions using hypothermia have been conducted, it is also necessary to examine their protective effects under normothermia as regional increases in myocardial temperature during hypothermic arrest are often reported. For this purpose myocardial protection was investigated in the isolated perfused rabbit heart exposed to 60 minutes of normothermic global ischemia during which Krebs-Henseleit, blood with heparin, Tyers', and St. Thomas' Hospital solutions were infused at 0.2 mL/min. Percent functional recovery dP/dtmax (mm hg/sec) at 5 minutes relative to pre-ischemic values using Tyers' (12 +/- 5)% was significantly less (p less than 0.05) than recovery using Krebs-Henseleit (57 +/- 13)% and St. Thomas' Hospital solution (47 +/- 5)%. Recovery using blood (79 +/- 7)% was significantly better than all other solutions. Following 25 minutes reperfusion, 4/6 hearts perfused with Tyers' experienced left ventricular fibrillation, while recovery of developed pressure with Krebs-Henseleit (74 +/- 5.8)%, St. Thomas' Hospital (66 +/- 3.4)% and blood (98 +/- 2.9)% was again significantly improved relative to Tyers', (p less than 0.05). Time to develop 5 mm contracture during the ischemic period was significantly shorter using Tyers' than with the other solutions. Using these indices of function, whereas Tyers' solution provided poor protection, blood provided excellent protection in rabbit hearts under normothermic conditions.
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PMID:Myocardial protection during ischemia in the isolated perfused rabbit heart. 359 93

To evaluate mechanisms behind the difference in susceptibility to ventricular fibrillation (VF) between the guinea pig and hedgehog heart, the cardiac electrophysiology of the two species was studied at normal body temperature and at different hypothermic levels by simultaneous recording of the monophasic action potential (MAP) and the external electrocardiogram (ECG). At normal body temperature, the duration of the ventricular MAP was significantly shorter in the hedgehog (93 +/- 8.1 ms) than in the guinea pig (138 +/- 2.6 ms). There was a distinct plateau phase in the guinea pig, whereas no such phase could be detected in the hedgehog. During hypothermia, a similar increase in MAP duration at full repolarization was noticed for both species. However, the prolongation of the MAP at lower repolarization levels was much less in the hedgehog. Besides, hypothermia-induced slow conduction and dispersion of ventricular repolarization was much more apparent in the guinea pig heart compared with the hedgehog heart. These differences may be important factors in the resistance to VF in the hedgehog, at normal body temperature and during hypothermia.
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PMID:Monophasic action potentials during induced hypothermia in hedgehog and guinea pig hearts. 368 52

Six cases of treatment of severe accidental hypothermia using cardiopulmonary bypass for core rewarming are reported and eleven cases from the literature are analyzed. Thirteen patients survived. Overall survival was more likely in patients who had vital signs initially. Initial mean core temperatures in the new cases was 22.8 C. Surface and conventional core rewarming methods resulted in an average temperature increase of 2.4 C per hr. Electrical defibrillation was generally without success until the core temperature had been raised to above 30 C. Between one and six hours after admission, partial femoral-femoral cardiopulmonary bypass (CPB) for core rewarming was started, causing a mean temperature increase of 9.5 C per hr. Four patients required a thoracotomy. Two patients had a massively dilated heart with contusions, and could not be weaned off bypass. None of the four long-term survivors had a demonstrable central nervous system (CNS) deficit. All patients developed temporary pulmonary problems; two developed wound infections. The average hospital stay was 21 days. CPB for core rewarming allows circulatory support while avoiding myocardial damage from prolonged external cardiac massage; rapidly increases the myocardial temperature and counteracts myocardial temperature gradients so that DC electroversion is successful; avoids "rewarming shock"; and improves microcirculatory flow. A prospective randomized trial to compare rapid surface rewarming and CPB rewarming is suggested. Immediate CPB for rewarming is recommended for patients in ventricular fibrillation with core temperatures below 30 C. Prolonged external cardiac massage (ECM) should not be used. The value of surface rewarming and non-CPB core rewarming methods remains undefined.
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PMID:Partial cardiopulmonary bypass for core rewarming in profound accidental hypothermia. 372 78


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