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Glutathione content during the rinsing and rewarming process of rat hepatocytes preserved in University of Wisconsin solution.

The addition of glutathione (GSH) to University of Wisconsin (UW) solution increases the intracellular content of GSH and decreases the release of lactate dehydrogenase used here as a measure of cell viability. However, we found a depletion of GSH when the cells were transferred from UW solution to the rewarming solution. This could sensitize the cells to various forms of oxidative injury. In this study we examined how different compositions of rinsing and rewarming solutions affected the GSH content and the viability of hepatocytes after 72 h of cold storage. For both the rinsing and the rewarming steps we used a Krebs-Henseleit solution with the addition of GSH, methionine, or both GSH and methionine. We found no loss of GSH when the hepatocytes were rinsed in the presence of 3 mM GSH. During the rewarming step we observed a loss of GSH in all of the study groups, but the cells that were incubated with 1 mM methionine showed a lesser depletion of GSH and improved viability. This finding may have valuable applications in hepatocellular transplantation and in the development of bioartificial liver support devices.

Adenosine↗

Accidental hypothermia: core rewarming with partial bypass.

Three patients with profound hypothermia were treated by rewarming on partial bypass. Two surivived and have normal mental and metabolic functions. The resuscitation of the hypothermic patient should be approached with enthusiasm since the outcome is often much better than expected from initial vital signs and neurologic examination. To avoid ventricular fibrillation the patient should be handled gently and an effort should be made to keep the patient well oxygenated and the pH normal. Blood gases should be measured often and corrected for temperature. The potassium concentration and hydration status of the patient should also be monitored closely. The rewarming of profoundly hypothermic patients can readily be accomplished with a pump oxygenator and heat exchanger. The indications for this method are not established from our small experience and the few cases reported in the literature. Certainly ventricular fibrillation is a compelling indication. Patients with frozen extremities might also benefit from this method since theoretically tissue salvage would be increased. Finally, those patients who do not respond rapidly to external rewarming may be at less risk of ventricular fibrillation if rewarmed on bypass.

Accidents↗

A comparative rewarming trial of gastric versus peritoneal lavage in a hypothermic model.

A comparison of gastric lavage versus peritoneal lavage rewarming was studied in a hypothermic rabbit model. The gastric lavage group (n = 5) had a mean rewarming time of 136 +/- 25.1 minutes versus the peritoneal lavage group (n = 6) mean rewarming time of 131.7 +/- 27.9 minutes (p = .795). Good correlation was found between tympanic membrane temperature readings and both rectal temperature readings (r = .69) in the gastric lavage group and esophageal temperature readings (r = .90) in the peritoneal lavage group. Gastric lavage and peritoneal lavage have the same rewarming rates in the present hypothermic model.

Animals↗

Is cerebral blood flow/metabolic mismatch during rewarming a risk factor after profound hypothermic procedures in small children?

The relation between cerebral blood flow and oxygen consumption was studied in six children during cardiac operations with profound hypothermia. A combination of topical cooling and core cooling was used to reduce the nasopharyngeal temperature to 15 degrees C. The alpha-stat principle for pH management was used. Blood flow and oxygen consumption decreased significantly with temperature. At a nasopharyngeal temperature of 15 degrees C, blood flow was reduced to 25% of the awake level, corresponding to 34% of the asleep value obtained 15-30 min after intubation. Oxygen consumption decreased to 25% of the asleep value. During stable profound hypothermia, venous saturation in the jugular bulb was at the same level as 15 min after intubation (70%). Markedly lower values were observed during topical cooling, and particularly during rewarming (down to 21%), indicating a mismatch between cerebral blood flow and oxygen consumption. The speed of rewarming correlated with the fall in venous oxygen saturation (rs = 0.82, P less than 0.05). It is suggested that periods of cerebral blood flow/metabolic mismatch during topical cooling and rewarming may explain postoperative cerebral dysfunction after deep hypothermic procedures. A moderate speed of rewarming is advocated.

Blood Flow Velocity↗

Accidental deep hypothermia with cardiopulmonary arrest: extracorporeal blood rewarming in 11 patients.

Sixteen patients (age 13-53 years) with accidental deep hypothermia have been rewarmed in our clinic during the last 10 years, 14 by femoro-femoral cardiopulmonary bypass (CPB) of whom 11 had a cardiopulmonary arrest (asystole in 5 and ventricular fibrillation in 6). On admission, the latter were clinically dead showing wide non-reactive pupils and being supported by ventilation and external heart massage. In the survivors, the mean length of cold exposure was 4.4 h (2-5.5 h) and mean arrest interval until initiation of CPB was 2.5 h (1.4-3.7 h). Rectal temperature on admission ranged from 17.5 degrees C to 26 degrees C (mean 22.5 degrees C). The causes for hypothermia were fall into a crevasse (5), avalanche (1), drowning (2) and cold exposure (3) including 2 suicide attempts. Results are summarized in the following table: [table: see text] Eight of the 11 patients with deep hypothermia and cardiac arrest were rewarmed and resuscitated successfully with CPB. Three patients, including 2 cases of asphyxia (avalanche and drowning), could not be weaned from CPB despite adequate rewarming. The other drowned patient (53 years) died on the 3rd postoperative day (POD) from ARDS. The main complication was pulmonary edema (57%) and transient neurological deficits. All survivors became conscious during the first POD and resumed, their professional activity. We conclude that patients with accidental deep hypothermia and even prolonged cardiopulmonary arrest should be rewarmed and resuscitated rapidly by cardiopulmonary bypass. These measures are very promising particularly if the cause of accident and the circumstances suggest that cardiopulmonary arrest was induced by hypothermia alone without other asphyxiating mechanisms.

Adolescent↗

Temperature gradients and rewarming time during hypothermic cardiopulmonary bypass with and without pulsatile flow.

Pulsatile perfusion during cardiopulmonary bypass (CPB) has been reported to have a number of beneficial effects, including attenuation of hormonal stress responses and improved organ blood flow and function. To determine the effect of pulsatile perfusion on temperature gradients and the time required for cooling and rewarming during CPB, we studied 21 patients scheduled for elective coronary artery operations. The patients were divided into two comparable groups: Group 1 (N = 11) had standard nonpulsatile perfusion, while in Group 2 (N = 10), a pulsatile pump was used. Rectal and esophageal temperatures were monitored, as were deltoid muscle temperatures and upper arm and finger skin temperatures in the same extremity. Ambient temperature, bypass flow and pressure, and bypass time were similar in both groups. Time required to cool to the lowest esophageal temperature was virtually identical for both groups (Group 1, 17 +/- 3 min; Group 2, 17.6 +/- 5 min), as was rewarming time (Group 1, 26.8 +/- 11 min; Group 2, 27.2 +/- 6 min). There were no significant differences in temperature measurements between groups except briefly during rewarming when finger skin temperature rose more rapidly in Group 1 (p less than 0.05). Temperature changes following CPB were the same for both groups, with rectal and esophageal temperatures showing an inverse relationships. These data demonstrate that pulsatile flow does not substantially alter rewarming time or temperature gradients during hypothermic CPB.

Aged↗

Improved prognosis in severely hypothermic newborn infants treated by rapid rewarming.

We introduced a rapid rewarming technique as part of standard therapy in 16 newborn infants with effects of severe environmental hypothermia. On admission, mean rectal temperature was 31.0 +/- 2.7 degrees C, mean gestational age was 33.4 +/- 4.5 weeks, and mean birth weight was 1.76 +/- 0.71 kg. Thirteen infants were admitted within 30 hours of delivery, and the remainder at 2 to 3 weeks of age. Infants were rewarmed under a radiant warmer. The mean time required to reach a rectal temperature of 36.5 degrees C was 3.96 +/- 2.37 hours. Major medical entities encountered included thrombocytopenia (eight patients), metabolic acidosis (eight), respiratory distress (eight), renal failure (six), apnea (four), patent ductus arteriosus (four), seizures (four), intracranial hemorrhage (three), infection (three), and necrotizing enterocolitis (two). No complications could be attributed to the rapid rewarming technique. Of three infants who died, all weighed less than 1.25 kg at birth. This 81% survival is in contrast to the high mortality (25% to 50%) noted previously among infants treated by gradual rewarming.

Apnea↗

The relationship between intramuscular temperature, skin temperature, and adipose thickness during cryotherapy and rewarming.

OBJECTIVE: To describe the relationships among muscle temperature, skin temperature, room temperature, body core temperature, time, and subcutaneous adipose thickness during cryotherapy and rewarming. DESIGN: A multiple linear regression with 5 independent variables (skin temperature, body core temperature, subcutaneous adipose thickness, room temperature, time) predicting intramuscular (IM) temperature. SETTING: A sports injury research laboratory. PARTICIPANTS: Fifteen volunteers with thigh skinfold measurements smaller than 40 mm. INTERVENTIONS: Thirty-minute cryotherapy treatment (ice bag) followed by a 120-minute rewarming period. MAIN OUTCOME MEASURES: The relationship between skin and IM temperature was described, and an equation predicting IM temperature by using room temperature, skin temperature, body core temperature, time, and adipose thickness was developed. RESULTS: Pearson's correlations between each predictor variable of IM temperature during cryotherapy were skin temperature, r = .46; skinfold, r = .37; time, r = -.59; core temperature, r =.21; and room temperature, r = -.47. During rewarming, the correlations were skin temperature, r = .71; skinfold, r = .27; time, r = .76; core temperature, r = - .05; and room temperature, r = - .21. A multiple regression equation (R(2) = .76) was developed to predict IM temperature during cryotherapy. A separate equation (R(2) =.81) was developed to predict muscle temperatures during rewarming. CONCLUSIONS: During and after ice application, no single predictor adequately explained the change in IM temperature. Skin surface temperature was a weak predictor of IM temperature during cryotherapy and should not be used as the sole dependent measure in cryotherapy efficacy studies.

Adult↗

Hand skin temperature variations for work in moderately cold environments and the effectiveness of periodic rewarming.

An investigation of skin surface temperature variations under actual work conditions for four locations on the hand studied the utility of hot water immersion sinks for restoring heat to the hands during exposure to moderately cold temperatures in a food processing plant. Hand skin temperature was recorded for 15 subjects in 2 jobs with an ambient temperature of 13.3 degrees C (56 degrees F) and 1 job with an ambient temperature of 23.9 degrees C (75 degrees F). Averaged over all jobs, the mean temperature for the dorsal and palmar third finger was 17.7 degrees C (63.9 degrees F), which was significantly (p < 0.01) cooler than the mean dorsal and palmar hand temperature of 28.9 degrees C (84.0 degrees F). There was no significant difference between dorsal and palmar temperatures for either the finger or the hand (p > 0.05). In the warm environment there were no significant differences in skin temperature for any of the four hand locations (p > 0.05). An exponential model of digital warming and cooling was empirically derived using 12 subjects for predicting finger skin temperature when periodically rewarming the hands using a hot water immersion sink. The dorsal and palmar finger had a mean time constant of 151 sec for warming during immersion, 640 sec for initial cooling after a 15- to 30-min rest break at room temperature, and 198 sec for cooling after rewarming in the hot sink. The sink did not appreciably raise minimum finger skin temperature after subjects rewarmed the hands for as long as 2 min and then worked for more than 10 min without a rewarming session.

Adult↗

Limited recovery of meiotic spindles in living human oocytes after cooling-rewarming observed using polarized light microscopy.

BACKGROUND: Spindles are formed from microtubules and are exquisitely sensitive to changes in temperature. An orientation-independent polarized light microscope, the Polscope, can be used to image spindles in living oocytes allowing analysis of spindle kinetics in the living state. This study examined the effects of cooling on spindle disassembly in living human oocytes and spindle recovery after rewarming. METHODS: Oocytes were imaged continuously with the Polscope during cooling and rewarming. The quantity of microtubules in the spindles was measured by its birefringence using the Polscope. RESULTS: Spindles had completely disassembled by 5 min after cooling and recovered by 20 min after rewarming to 37 degrees C if rewarming started soon after the oocyte's temperature dropped to room temperature. However, when oocytes were cooled and kept at 33, 28 or 25 degrees C for 10 min and then warmed, it was found that warming allowed 5/5, 2/5 and 0/5 oocytes of the spindles to recover respectively. CONCLUSIONS: These results indicate that human meiotic spindles are exquisitely sensitive to alterations in temperature. The maintenance of temperature at 37 degrees C during in-vitro manipulation is important for spindle integrity and, therefore, is likely to be important for normal fertilization and subsequent embryo development.

Cold Temperature↗

Oxygen delivery and consumption during hypothermia and rewarming in the dog.

Changes in oxygen consumption (VO2) and oxygen delivery (DO2) were compared in three groups of paralyzed, sedated dogs: 1) a group (n = 5) cooled to 29 degrees C and immediately rewarmed to 37 degrees C; 2) a group (n = 5) cooled to and maintained at 29 degrees C for 24 h, and then rewarmed; and 3) a group (n = 5) maintained at 37 degrees C for 24 h. During the cooling phase, in both the acute and prolonged hypothermia animals, VO2 and DO2 decreased significantly from control values (P less than 0.05). The decrease in DO2 occurred as a result of a similar decrease in cardiac index (CI; P less than 0.05) that was associated with a significant increase in systemic vascular resistance index (SVRI; P less than 0.05). Arteriovenous oxygen content difference (C(a-v)O2), O2 extraction ratio, mixed venous oxygen tension (PVO2), pH, and base deficit (BD) were not different from control values even during prolonged hypothermia. Normothermic control dogs also demonstrated a significant decrease in CI (P less than 0.05) at 24 h. Surface rewarming increased VO2 back to control values in the acute hypothermia group and to values above control (P less than 0.05) in the prolonged hypothermia group. DO2 remained below control in both groups, resulting in a significant increase in O2 extraction (P less than 0.05) and a decrease in PVO2 (P less than 0.05) in the prolonged hypothermia animals. Following rewarming administration of sodium nitroprusside returned DO2, CI, and SVRI to control values but did not increase VO2. All animals survived the study without need for inotropic support.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Rewarming eliminates the protective effect of cooling against delayed neuronal death.

Mild intra-ischemic hypothermia provides neuroprotection against delayed neuronal death in the hippocampal CA1. It has recently been reported that reduction in the metabolic rate of arachidonic acid (AA) liberated during ischemia might contribute to this neuroprotection. To examine whether rewarming during the early period of recirculation accelerates AA consumption and eliminates the neuroprotection, we measured the levels of AA in the hippocampus after various recirculation times under normothermia and hypothermia with or without rewarming. The tendency for AA to disappear was significantly different between each pair of groups. Histological examination 7 days after ischemia revealed no protection in the rewarmed group. These results suggest that neuronal injury during rewarming after hypothermia may be attributed to the rate of AA metabolism.

Animals↗

Rewarming hypovolemia after aortocoronary bypass surgery.

Coronary bypass performed with moderate systemic hypothermia (25 degrees C) and cold-potassium cardioplegia was associated with a fall and subsequent rise in core (pulmonary arterial) temperature. Serial hemodynamic measurements during rewarming and recovery revealed a decrease in cardiac index (CI) without a decrease in the left atrial pressure (LAP) of 17 patients recovering from uneventful coronary bypass surgery. Nuclear ventriculograms performed during rewarming demonstrated a decrease in left ventricular end-diastolic volume index (EDVI, calculated from the thermodilution stroke index divided by the nuclear ejection fraction) without a change in LAP. Volume loading during both mild hypothermia (35 +/- 5[SD]degrees C) and normothermia revealed that myocardial performance (the relation between CI and EDVI) was unchanged, but diastolic compliance (the relation between LAP and EDVI) decreased with rewarming. LAP was a poor indicator of left ventricular preload (EDVI) during rewarming, and volume loading was required to maintain preload and prevent hypoperfusion.

Atrial Function↗

Finger blood pressure and rewarming rate for screening and diagnosis of Raynaud's phenomenon in workers exposed to vibration.

Both the finger systolic blood pressure (FSP) and the rewarming test of finger skin are measures of circulation in the finger; the first reflects the vasoconstriction phase and the second the vasodilatation phase. The combinations of the specificity and the sensitivity of these methods were evaluated by a receiver operating characteristic curve (ROC). The material included 37 vibration-induced white finger (VWF) cases, five primary Raynaud's cases, and 37 controls. The specificity of the FSP test was high with regard to the anamnesis of white finger and the test was useful for the diagnosis of Raynaud's phenomenon, but the sensitivity was too low for screening. The rewarming test was useful for screening primary Raynaud's case and possibly for screening disorders in peripheral vasodilative function. The connections between the rewarming test and VWF are not clear and according to the present study the rewarming test was not suitable for screening VWF.

Adult↗

Skeletal and cardiac muscle protein turnover during short-term cold exposure and rewarming in young rats.

Young animals exposed to cold environmental temperatures typically have decreased skeletal muscle accretion but increased heart masses. To explore these phenomena, we measured protein synthesis and degradation in vivo in cardiac and skeletal muscle in weanling rats during short-term cold exposure and rewarming. Control rats were housed at 25 degrees C throughout the experiment. Ad libitum-fed and pair-fed (to the intake of controls) rats were housed at 5 degrees C (cold) for 5 days and then at 25 degrees C (rewarmed) for another 5 days. Cold exposure decreased rates of protein accretion and synthesis in skeletal muscle, whereas degradation did not differ. The effects of cold exposure on skeletal muscle were similar in both pair-fed and ad libitum-fed rats, except growth was lower in pair-fed rats. In cardiac muscle, cold exposure increased rates of protein synthesis and degradation and resulted in increased cardiac mass. Results in pair-fed animals generally fell between those of control and ad libitum-fed cold rats. During rewarming, growth rates were not higher in skeletal muscle in ad libitum-fed re-warmed rats, although protein turnover returned toward control values; in pair-fed rats, it remained lower. In heart, growth rates of ad libitum-fed and pair-fed rewarmed rats decreased due to lower protein synthesis rates. These alterations appear to be consistent with a strategy designed to improve survival in cold environments.

Acclimatization↗

Myocardial norepinephrine turnover during induced hypothermia and rewarming.

Norepinephrine (NE) turnover in myocardial tissue was measured in male golden hamsters (Mesocricetus auratus) during 1) continuous hypothermia, 2) rewarming from hypothermia initiated by exposure to 22 degrees C ambient, and 3) normothermic control state. Hypothermia was induced by exposure to 80% He-20% O2 atmosphere at 0 to -10 degrees C. At sequential periods after tritiated norepinephrine ([3H]NE) infusion, hamsters were killed by cervical transection and hearts were removed and analyzed for NE and [3H]NE content. Rate constants, turnover times, and turnover rates were determined from regression analysis of [3H]NE/micrograms NE tissue decay. Myocardial concentrations of NE were constant during NE-turnover measurements in each group. However, myocardial NE levels were reduced by 37% in both continuous hypothermia and rewarming from hypothermia compared with normothermic controls. NE turnover was highest during rewarming from hypothermia (0.34 micrograms.g-1.h-1), but no decay in myocardial [3H]NE was detectable during continuous hypothermia. Control animals had turnover values of 0.15 micrograms.g-1.h-1. Turnover data indicate severe depression in myocardial sympathetic nerve activity during hypothermia but a significant increase above normothermic control levels during rewarming from hypothermia.

Adrenergic Fibers↗

Afterdrop of body temperature during rewarming: an alternative explanation.

Afterdrop, the continued fall of deep body temperatures during rewarming after hypothermia, is thought to endanger the heart by further cooling from cold blood presumed to be returning from the periphery. However, afterdrop is not always observed, depending on the circumstances. To explore this phenomenon, mild hypothermia was induced quantitatively with a suit calorimeter, using several patterns of cooling and rewarming. When cooling was rapid and followed immediately by rewarming, there were typical afterdrops in the temperatures measured in the rectum, auditory canal, and esophagus. However, when rewarming was delayed, or when cooling had been slow and prolonged, afterdrop was not seen. Afterdrops were then observed in two physical models that had no circulation: a bag of gelatin and a leg of beef. Central layers continued to give up heat as long as the surrounding layer was cooler. These results, together with recent findings by others that peripheral blood flow is low until afterdrop is complete, make this circulatory explanation of afterdrop improbable. Alternatively, afterdrop can be explained by the way heat moves through a mass of tissue.

Adult↗

Safety and efficacy of endovascular cooling and rewarming for induction and reversal of hypothermia in human-sized pigs.

BACKGROUND AND PURPOSE: Numerous studies indicate that mild hypothermia provides substantial neuroprotection. However, current systems transfer insufficient heat to rapidly vary core temperature. We thus evaluated the safety and efficacy of endovascular cooling and rewarming for the induction and reversal of hypothermia. METHODS: In 10 anesthetized pigs (weight, 66+/-2 kg), a heat-exchange balloon catheter was inserted into the inferior vena cava and used to cool to a core temperature of 32 degrees C and then rewarm to normothermia. Control animals had 38 degrees C saline infused. Venous blood was sampled before, during, and after cooling. Three animals in each group were killed 1 week later, and the lungs and inferior vena cava were removed for gross and microscopic examination. In 5 additional animals, cardiac output was measured during cooling to 32 degrees C. RESULTS: Body temperature in the hypothermic animals decreased at a rate of 4.5+/-0.4 degrees C/h. Animals were subsequently rewarmed to 36.0+/-0.04 degrees C at 2.5+/-0.2 degrees C/h. There was no difference in heart rate between hypothermic and control animals, whereas systolic pressure decreased during cooling. Cardiac output was well maintained during cooling. There were no thermal effects on blood elements or blood vessels. CONCLUSIONS: The endovascular heat-exchange system effectively cooled and rewarmed pigs with large thermal mass without producing any adverse effects on blood elements, blood vessel integrity, or cardiovascular function.

Animals↗