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At least 235 records · Page 13Linked to original sources
PubMed1998

Changes in myocardial ultrastructure induced by cooling as well as rewarming.

The aim of the present study was to investigate if hypothermia and rewarming, without accompanying cardiac ischaemia or cardioplegia, causes myocardial damage. Anaesthetized rats were subjected to a cooling procedure (4 h at 15-13 degrees C) where spontaneous cardiac electromechanical activity was maintained, followed by rewarming. Control rats, hypothermic rats and posthypothermic rats were perfusion-fixed, the hearts removed and the ventricles examined using an electron microscope. Based on morphometric methodology volume fractions as well as absolute volumes of cellular and subcellular components of the ventricles were assessed. In hypothermic hearts capillary volume fraction was significantly decreased, which was probably due to a decrease in perfusion pressure. The cytosolic volume increased in both absolute values and as a fraction of the myocyte: from 25 +/- 11 in controls to 43 +/- 8 microliters and from 0.067 +/- 0.023 to 0.102 +/- 0.013, respectively. There was a corresponding relative decrease in the volume fraction of myofilaments from 0.598 +/- 0.030 to 0.548 +/- 0.024. In posthypothermic hearts significant tissue swelling was apparent, dominated by a significant increase in myocyte volume from 372 +/- 66 in controls to 522 +/- 166 microliters. Similar changes were measured in mitochondrial and cytosolic volumes. In conclusion, the myocardial ultrastructure was altered during hypothermia as well as after rewarming. Posthypothermic myocardium showed generalized cellular swelling and areas of cellular necrosis.

Animals↗
PubMed1990

Experimental frostbite: freezing times, rewarming times, and lowest temperatures of pig skin exposed to chilled air.

Frostbite was produced in the skin of five Hanford Miniature Swine by exposing local areas to chilled air (-75 degrees C) for 1, 3, 5, 10, or 20 min. A copper-constantan thermocouple was inserted into the dermis to measure the temperature. The mean freezing time (the time required to reach 0 degrees C) was approximately 1.9 min. The mean lowest temperatures were 8.8, -15.7, -20.9, -22.5, and -23.4 degrees C for the 1-, 3-, 5-, 10-, and 20-min freezes, respectively. The mean times to rewarm the skin to 25 degrees C were 3.1, 4.5, 5.5, 7.0, and 8.6 min for the 1-, 3-, 5-, 10-, and 20-min freezes, respectively. Significant linear correlations existed between duration of freeze and rewarming times, duration of freeze and lowest temperature, and lowest temperature and rewarming times.

Animals↗
PubMed1976

Rewarming from immersion hypothermia: a comparison of three techniques.

Rewarming from immersion hypothermia has been assessed in sheep by the use of three techniques--hot bath, body insulation and airway warming. Though the hot bath was the fastest of the methods of rewarming studied, consideration of temperature gradients and therefore total body heat diminished its advantage in comparison with central body rewarming via the airway (CBRW), which in turn showed considerably advantage over body insulation alone. CBRW did not have any thermal advantage gained on assisting the ventilation as compared with spontaneous breathing. The results illustrate the importance of adequate insulation of the body to prevent further heat loss and this was found to be true whether or not airway warming was being used. The site of heat uptake with CBRW was determined and observations were made on the physical behaviour of temperature gradients.

Animals↗
PubMed1986

Rewarming in immersion hypothermia: radio-wave and inhalation therapy.

Anesthetized random source dogs were cooled by ice water immersion (1 degree C) to a stable core temperature of 25 degrees C, and subsequently rewarmed with warm humidified inhalation (43 degrees C, 450 cc of min ventilation/kg), radio wave induction hyperthermia (4-6 W/kg) or both therapies simultaneously. The mean time required for core rewarming to 30 degrees C was 262 +/- 29 min for humidified ventilation, 68.5 +/- 6 min for radio wave therapy (P less than 0.01), and 74.8 +/- 12 for both therapies combined (P less than 0.3 vs. radio wave). There was no tissue damage with these protocols. These data suggest radio wave heating alone is the most rapid non-invasive method for core rewarming in immersion hypothermia.

Animals↗
PubMed1984

Controlled comparison of humidified inhalation and peritoneal lavage in rewarming of immersion hypothermia.

Random source dogs were anesthetized and cooled by immersion in ice water to a stable core temperature of 25 degrees C and subsequently rewarmed with either normal saline peritoneal lavage (43 degrees C, 175 ml/kg/h) or warmed humidified inhalation (43 degrees C, 450 ml/kg/min ventilation). The time required for core rewarming to 30 degrees C was 192 +/- 61 minutes for lavage and 331 +/- 96 minutes for inhalation therapy (P less than 0.03). These data suggest that peritoneal lavage is superior to inhalation therapy for core rewarming of rapidly induced immersion hypothermia.

Animals↗
PubMedDate not supplied

Accidental hypothermia with cardiac arrest: recovery following rewarming by cardiopulmonary bypass.

A 22-year-old man eventually had a good neurologic recovery following prolonged coma after extracorporeal rewarming from profound hypothermia (24 degrees C) due to exposure. The patient was in full arrest for 60 minutes prior to institution of cardiopulmonary bypass (CPB). Total bypass time was 50 minutes. Cardiopulmonary bypass is the current rewarming method of choice for severe hypothermia associated with a persistent nonperfusing cardiac rhythm. CPB provides the most rapid core rewarming with the additional benefit of circulatory support during the period of cardiac instability.

Adult↗
PubMed1994

Rewarming and sweating during cardiopulmonary bypass.

The hypothesis was tested that facial sweating at the end of cardiopulmonary bypass (CPB) is a thermoregulatory phenomenon. Twenty-two patients undergoing cardiac surgery with fentanyl anesthesia were studied. Nasopharyngeal temperature, nasal skin temperature, rectal temperature, and mean skin temperature were monitored for 90 minutes after the start of rewarming on CPB. Calf-toe and forehead-nose skin temperature gradients were followed as a measure of peripheral and facial thermoregulatory vasoactive responses. Facial sweating was defined as grade 1 (noticeable) or grade 2 (obvious droplets). Fourteen patients (64%) sweated during rewarming at the end of CPB. In 11 cases the onset of sweating was preceded by a dramatic increase in nasal skin temperature (mean +/- SEM, 4.6 +/- 0.3 degrees C in 5 min), suggesting facial vasodilation. The maximum rate of increase (degree C/5 min) in nasal skin temperature was significantly greater in patients who sweated than in those who did not, 4.1 +/- 0.4 degrees C versus 2.6 +/- 0.3 degrees C (P < 0.015). There was no difference in the age, weight, or BSA between patients who sweated during CPB and those who did not. The nasopharyngeal temperature threshold for the onset of sweating was not elevated (grade 1, 36.4 +/- 0.5 degrees C; grade 2, 37.6 +/- 0.4 degrees C), but there was a 5 to 6 degrees C interpatient variation. It was concluded that facial sweating during rewarming on CPB is typical of a thermoregulatory response. Absence of sweating in one third of patients may be due to pharmacokinetic or pharmacodynamic differences in the response to anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Rewarming in accidental hypothermia: radio wave versus inhalation therapy.

Anesthetized random-source dogs were cooled by refrigeration (3 C) to a stable core temperature of 25 C, and subsequently were rewarmed with warm, humidified inhalation (43 C, 450 mL of minute ventilation per kilogram) or radio frequency induction hyperthermia (4 to 6 watts/kg). The mean time required for core rewarming to 30 C was 231 +/- 3 minutes for warm, humidified ventilation and 106 +/- 32 minutes for radio wave therapy (P less than .01). These data suggest that radio wave heating is a more rapid noninvasive therapy for core rewarming of accidental hypothermia.

Animals↗
PubMed2003

Reduced jugular venous oxygen saturation during rewarming from deep hypothermic circulatory arrest: cerebral overextraction?

Deep hypothermic circulatory arrest may impair cerebral cellular functions, and physiological parameters following circulatory arrest may deviate from the normal. The intention of this study was to monitor jugular venous oxygen saturation during cardiopulmonary bypass before and after deep hypothermic circulatory arrest. Jugular venous oxygen saturation were obtained on 18 patients by using a retrograde jugular vein catheter during replacement of the ascending aorta. Indications for operations were ascending aortic dilatation (n=15) and acute aortic dissection (n=3). Hypothermic cardiopulmonary bypass (233+/-60 min), cardioplegic arrest (105+/-37 min) and circulatory arrest (22+/-7 min) were utilized during the operations. Jugular venous oxygen saturation increased during hypothermia and decreased during rewarming. Compared with cooling, jugular venous oxygen saturation during the initial part of rewarming were significantly lower (87+/-5% vs. 97+/-1%, 89+/-4% vs. 95+/-2%, 81+/-4% vs. 87+/-5% at 16, 20 and 24 degrees C respectively, p<0.05). One patient required re-exploration because of bleeding. All patients were found neurologically normal before being discharged from the hospital (mean 14+/-7 days). In conclusion, jugular venous oxygen saturation is inversely related to the body temperature in patients undergoing hypothermic cardiopulmonary bypass. Significantly decreased jugular venous oxygen saturation during the initial part of rewarming may signify an increased cerebral extraction of oxygen.

Adult↗
PubMed1995

Haemodynamic and metabolic effects of surface rewarming after coronary revascularization.

Cardiac surgery is often associated with a postoperative increase in the patient's metabolic rate; surface rewarming has been suggested to decrease the energy expenditure by preventing hypothermia. Thirty patients, undergoing coronary revascularization, were randomly divided into two groups; after surgery group A was rewarmed by a new device that acts by both conduction and convection, while group B was just covered with cotton blankets. Blood, oesophagus and skin (thigh and foot) temperatures were recorded on admission to the intensive care unit (ICU) and 30, 60, 90, 180, 270, and 450 min later. Haemodynamic parameters, oxygen delivery, calculated oxygen consumption, and plasma lactate concentration were assessed as well. Group A warmed up quicker than group B as far as the skin was concerned while the core temperature was unaffected. Group A was also characterized by lower cardiac indices and oxygen consumption. As the occurrence of a dependence of oxygen consumption on delivery could be reasonably ruled out in warmed patients because blood lactate levels were lower than in the controls, we conclude that surface rewarming might have some positive effect in decreasing metabolic demand after cardiac surgery even if the patient's core temperature is little affected. The inhibition of skin temperature receptors could possibly explain this finding.

Bedding and Linens↗
PubMed2003

A critique of a UK standardized test of finger rewarming after cold provocation in the diagnosis and staging of hand-arm vibration syndrome.

BACKGROUND: Accurate diagnosis and staging of hand-arm vibration syndrome (HAVS) is important in health surveillance of vibration-exposed workers and the substantial number of related medico-legal cases. The measurement of the rewarming rate of fingers after cold provocation to the hands (CPT) has been suggested as a useful test in diagnosing HAVS. AIM: To investigate the diagnostic value of a standardized version of the CPT test using a 15 degrees C cold challenge for 5 min applied in the recent compensation assessment of UK miners. METHODS: Analysis of a subset of UK miners assessed at our unit, together with data from a small repeatability study of the standardized CPT in normal subjects. RESULTS: Rewarming time in the CPT was significantly lower in those subjects classified as vascular Stockholm stage 0 compared with Stockholm stages 1-3 combined, but did not discriminate between the stages of abnormality. Using the suggested cut-off in the CPT test, the sensitivity and specificity were calculated as 43 and 78%, respectively. Receiver operator characteristic analysis suggested that the rewarming time of highest accuracy gave a sensitivity of 66% and specificity of 59%. In 10 miners who reported unilateral hand blanching, there was no significant difference in CPT measurements between blanching and non-blanching hands. Repeat CPT measurements in normal subjects suggested mean differences of 52 and 107 s for each hand, and the Bland-Altman coefficient of repeatability was approximately 600 s for all fingers. CONCLUSION: Single application of this standardized CPT test may have limited value in diagnosing the vascular component of HAVS in an individual.

Adult↗
PubMed1980

Hypothermia after cardiopulmonary bypass in man: amelioration by nitroprusside-induced vasodilation during rewarming.

The incidence, time course, and magnitude of hypothermia following apparently adequate rewarming from hypothermic cardiopulmonary bypass (defined as a nasopharyngeal temperature [NPT] of 37 C) were studied in 20 adult patients (Group I). In each patient a decrease in NPT (averaging 2.6 +/- .2 C) occurred during the 80-min intraoperative postbypass period. The NPT had stabilized approximately 45 min after the end of bypass. Eight additional patients (Group II) received pharmacologic vasodilation with nitroprusside during the rewarming period. Pump flow was increased as nitroprusside was infused to maintain mean arterial pressure greater than or equal to 70 torr. Group II patients maintained NPT significantly better in the postbypass period than did Group I patients (NPT decrease of 1.5 +/- .4 C, P < 0.01, a 42 per cent improvement). As in Group I, NPT in Group II had stabilized 45 min after bypass. Ambient air temperatures between 18 and 23 C had no effect on NPT decrease. Presumed peripheral heat delivery was found to be greater in Group II. It is concluded that postbypass NPT decreases occurred in all patients, but that these decreases were significantly lessened by pharmacologic vasodilation plus deliberately increased pump flow during rewarming on bypass.

Cardiopulmonary Bypass↗
PubMed1981

Hemodynamic effects of inotropes during hypothermia and rapid rewarming.

The hemodynamic effects of propranolol, lidocaine, and dopamine were studied in anesthetized, mechanically ventilated dogs, cooled to 25 degrees C with a venovenous shunt through a heat exchanger. After 1 h at 25 degrees C, the shunt was converted to an arteriovenous shunt which remained functional until the study was completed. Before rewarming, the authors treated each group of 8 dogs with intravenous doses of the drugs: group 1: 10 ml saline as control; group 2: propranolol 0.3 mg/kg; group 3: 50 mg lidocaine initially, followed with continuous infusion of 40-50 microgram/kg.min; group 4: dopamine infusion at 12 microgram/kg.min; and group 5: lidocaine as in group 3 and dopamine as in group 4. For the dopamine-treated groups, 2 min of infusion was allowed; in all other groups, 5 min elapsed after injection before the hemodynamic data were recorded. The hemodynamic data were collected at esophageal temperatures of 25, 30, and 37 degrees C. The findings were: (1) hypothermia impaired cardiovascular function; (2) lidocaine and propranolol had minimal hemodynamic effects during hypothermia; lidocaine was physiologically more desirable than propranolol; (3) dopamine, alone or combined with lidocaine, reversed the cardiovascular depression from hypothermia; the improvement was equivalent to rewarming by as much as 5 degrees C; and (4) at the completion of rewarming, cardiovascular recovery was more complete with dopamine/lidocaine-treated animals compared to untreated and propranolol-treated animals. Based on these findings, these inotropes appear to be safe adjuncts to resuscitation during hypothermia.

Animals↗
PubMed1985

Controlled comparison of radio wave regional hyperthermia and peritoneal lavage rewarming after immersion hypothermia.

Anesthetized random source dogs were cooled by ice-water immersion to a stable core temperature of 25 degrees C and subsequently rewarmed with normal saline peritoneal lavage (43 degrees C, 175 ml/kg/hr) or radio frequency electromagnetic-induced regional hyperthermia (4-6 watts/kg). The mean time required for core rewarming to 30 degrees C was 183 +/- 79 minutes for lavage and 58 +/- 13 minutes for radio wave therapy (p less than 0.01). There was no evidence of tissue damage with either modality. These data suggest radio wave regional hyperthermia is superior to peritoneal lavage for core rewarming of rapidly induced immersion hypothermia.

Animals↗
PubMed1991

Comparison of three methods of rewarming from hypothermia: advantages of extracorporeal blood warming.

We developed a new technique, extracorporeal venovenous rewarming (EVR), to rewarm hypothermic patients in the intensive care unit or operating room. We compared this method with the active external (standard) techniques of warming blankets; heated ventilator circuits, intravenous fluids, and gastric and peritoneal lavage; and cardiopulmonary bypass. The EVR technique warmed patients' blood or additional blood products and crystalloids to 40 degrees C at 150-400 mL/min and allowed survival from a core temperature of 31.1 degrees C after massive injury. The EVR technique rewarming patients more rapidly than standard techniques and may be most appropriate in patients with multisystem trauma when rapid correction of hypothermia-related hypovolemia, coagulopathy, and arrhythmia is necessary. Cardiopulmonary bypass is required in severely hypothermic patients with cardiac arrest. Standard techniques can be used when these immediately life-threatening conditions are not present.

Adult↗
PubMed1986

An investigation of factors affecting postoperative rewarming of adult patients.

Aural canal temperature was measured for one hour after arrival in the recovery room in 200 adult patients who underwent one of the following types of major surgery: abdominal, pelvic, vascular, orthopaedic or prostatic. One group of 100 patients was studied in the recovery room of Hammersmith Hospital which was not equipped with a controlled system for constant ventilation and humidification, while the other 100 patients were studied in the recovery room of Edgware General Hospital, which had a constant ambient temperature and controlled relative humidity with 20 air changes/hour. The rate of rewarming was found to be similar in both groups. Within the range of ambient temperatures and relative humidities measured, patients over 60 years of age rewarmed more slowly than did patients under 60 years (p less than 0.05). General anaesthesia was associated with significantly faster rewarming than was local anaesthesia (p less than 0.01).

Age Factors↗
PubMed1987

Postoperative ventilatory and circulatory effects of heating after aortocoronary bypass surgery. Extended rewarming during cardiopulmonary bypass and postoperative radiant heat supply.

Twenty-four patients with stable angina pectoris were studied after aortocoronary bypass surgery with hypothermic cardiopulmonary bypass (CPB). Twelve patients (radiant heat supply group) were rewarmed during CPB to a nasopharyngeal temperature of at least 38 degrees C and a mean rectal temperature of 34.4 degrees C. Postoperatively they received radiant heat supply from a thermal ceiling. In addition, a heating water mattress was used during the end of the operation and heated, humidified inspired gases were administered intra- and postoperatively. The other 12 patients (combination heat supply group) had the rewarming during CPB extended until the rectal temperature exceeded 36 degrees C, but otherwise received the same treatment as the radiant heat supply group. The combination of extended rewarming during CPB and postoperative radiant heat supply significantly reduced oxygen uptake, carbon dioxide production and the required ventilation volumes during early recovery as compared with the values in the radiant heat supply group. The reduced metabolic demands were accompanied by lower cardiac index and oxygen delivery, which, however, were sufficient for adequate tissue perfusion as judged by the similarity in oxygen extraction and arterial base excess values in the two groups. The metabolic demands and ventilatory requirements were reduced to a level at which safe early extubation is possible.

Anesthesia↗
PubMed1993

Substrate preference of isolated perfused rat hearts during hypothermia and rewarming.

Fatty acid and glucose oxidation rates were measured in isolated rat hearts undergoing hypothermia and rewarming. The hearts were perfused in the Langendorff mode with Krebs-Henseleit bicarbonate buffer containing 11.1 mM glucose plus 0.6 mM albumin-bound oleic acid as energy substrates. The hearts were stabilized at 37 degrees C and thereafter cooled progressively to 15 degrees C over a period of 60 min. The hearts were kept at this temperature for 10 min and then rewarmed to 37 degrees C during the next 30 min. Control hearts were perfused at 37 degrees C throughout the whole perfusion period. Trace amounts of [14C]glucose or [14C]oleic acid were included in the perfusate, and the rate of substrate oxidation was determined on the basis of the radioactive CO2 production. In normothermic hearts steady state oxidation rates of glucose and oleate were found to be 0.17 +/- 0.01 and 0.51 +/- 0.07 mumol min-1 g-1 dry wt, respectively (mean +/- SEM). In response to hypothermia (15 degrees C) glucose oxidation was reduced by 76% (from 0.17 +/- 0.01 to 0.04 +/- 0.01 mumol min-1 g-1 dry wt) and oleate oxidation by 47% (from 0.51 +/- 0.07 to 0.27 +/- 0.02 mumol min-1 g-1 dry wt). Upon rewarming glucose and fatty acid oxidation rates returned to essentially the same values (0.12 +/- 0.02 and 0.45 +/- 0.04 mumol min-1 g-1 dry wt) as those observed under steady state normothermic conditions. The molar ratio between glucose and fatty acid oxidation was, however, significantly (P < 0.05) lower in hypothermic than in normothermic hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗