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PubMed2003

Cooling and rewarming for brain ischemia or injury: theoretical analysis.

A three-dimensional model is developed in this study to examine the transient and steady state temperature distribution in the brain during selective brain cooling (SBC) and subsequent rewarming. Selective brain cooling is induced through either wearing a cooling helmet or packing the head with ice. The ischemic region of the brain is simulated through reducing the blood perfusion rate to 20% of its normal value. The geometric and thermal properties and physiological characteristics for each layer, as well as the arterial blood temperature, are used as the input to the Pennes bioheat equation. Our data suggest that rapid cooling of the brain gray matter can be achieved by SBC on the head surface (26 min for adults versus 15 min for infants). Suboptimal thermal contact between the head surface and the coolant in most commercially available cooling helmets is suspected to be the main reason for delayed cooling in SBC as compared to the ice packing. The study has also demonstrated that the simulated 3 degrees C/h passive rewarming rate by exposing the head to room temperature after removing the source of cooling may be too rapid.

Adult↗
PubMed2003

Effect of blood flow on thermal equilibration and venous rewarming.

In this study we have explored the feasibility of using an isolated rat limb as an animal model for studying countercurrent arterial thermal equilibration and venous rewarming in muscle tissue. Unlike in vivo experiments in which animal models have been used for studying thermoregulation or temperature response in tissue under various physiological conditions, isolated organ or tissue provides for better control and more accurate measurement of the blood perfusion rate. It has been shown that the induced perfusion rate in the rat limb can vary from 3 ml/(min x 100 g) at normal physiological conditions to 25 ml/(min x 100 g) during hyperemic conditions. Temperature distributions along the countercurrent arteries and veins have been measured using fine thermocouple wires. We observed a 25%-78% thermal equilibration along the femoral artery and its branches in intermediate size vessels between 700 and 300 microm diameter. This equilibration depends strongly on the local perfusion rate. In comparison, local perfusion rate plays a minor role in determining the overall venous rewarming in the rat hind limb. Approximately 70%-80% of the heat leaving the artery is recaptured by the countercurrent vein. This agrees well with our previous theoretical and experimental results, which show a dramatic shift in thermal equilibration between the supply artery and vein tissue cylinder and the secondary vessel tissue cylinder as the flow rate changes.

Adaptation, Biological↗
PubMed1984

Cardiac arrhythmias during rewarming of patients with accidental hypothermia.

Accidental hypothermia has a high mortality and is associated with cardiac arrhythmias. To determine the incidence of arrhythmias and their importance 22 patients with accidental hypothermia (core temperature less than 35 degrees C) were studied by 12 lead electrocardiography and continuous recording of cardiac rhythm. Although 14 of the patients died (64%), only six died while hypothermic. Prolongation of the Q-T interval and the presence of J waves were related to the severity of the hypothermia. Supraventricular arrhythmias, including atrial fibrillation, were common (nine cases) and benign. Ventricular extrasystoles were also common (10 cases), but ventricular tachycardia or fibrillation did not occur during rewarming. In eight patients who died while being monitored the terminal rhythm was asystole. There was no correlation between the severity of hypothermia or the rate of rewarming and the clinical outcome. In the absence of malignant arrhythmias there is no indication for using prophylactic antiarrhythmic treatment in patients with accidental hypothermia. The presence or absence of severe underlying disease is the main determinant of prognosis.

Adult↗
PubMed1985

Respiration during hypothermia: effect of rewarming intermediate areas of ventral medulla.

We studied respiration (phrenic nerve activity) during progressive hypothermia to as low as 30.5 degrees C in five anesthetized, paralyzed, glomectomized, and vagotomized cats. PCO2 was maintained at a constant level throughout the experiments. We confirmed the results of a previous study (J. P. Kiley, F. L. Eldridge, and D. E. Millhorn, J. Appl. Physiol. 58: 295-312, 1985) in which respiratory minute output decreased progressively with cooling and respiratory frequency decreased markedly. In addition we show that focal rewarming to normal temperature (37.5 degrees C) of the structures in the intermediate areas on the ventral surface of the medulla resulted in a significant reversal of the depressed respiratory minute activity observed with hypothermia. Respiratory frequency, however, was unaffected by intermediate area rewarming. We conclude that the decreased respiratory activity during hypothermia is due to a generalized interference with neural function. A major portion of these effects is due to cooling of the intermediate areas, but the slowing of respiratory frequency appears to be an independent effect.

Animals↗
PubMed2002

Immediate treatment of frostbite using rapid rewarming in tea decoction followed by combined therapy of pentoxifylline, aspirin & vitamin C.

BACKGROUND & OBJECTIVES: Frostbite, the severest form of cold injury is a serious medical problem for our Armed Forces operating in the snow bound areas at high altitude. Effects of treatment by rapid rewarming in tea decoction followed by combined therapy of pentoxifylline, aspirin and vitamin C were evaluated in amelioration of tissue damage due to experimentally induced frostbite in rats. METHODS: Experiments were conducted in 2 groups (25 each) of albino rats (control i.e., untreated and experimental i.e., treated). Frostbite was produced experimentally in all the animals by exposing one of the hind limbs at -12 +/- 1 degree C with wind flow 25-30 lit/min for 30 min in a freezing-machine, with simultaneous recordings of rectal and ambient temperatures. The degree of tissue damage was assessed after 10 days. Following cold exposure, neither external thawing nor any medication was given to the animals of the control group; while the exposed limb of the experimental animals was rewarmed in tea decoction maintained at 37-39 degrees C for 30 min immediately after cold exposure, with simultaneous oral ingestion of warm tea decoction. These animals were also given pentoxifylline (40 mg/kg), aspirin (5 mg/kg) and vitamin C (50 mg/kg) twice daily orally for the next 7 days. RESULTS: In the control group, 68 per cent animals suffered from severe (56%) to very severe (12%) frostbite, while the remaining 32 per cent had moderate frostbite. No animals of this group could escape injury or suffered anything less than moderate frostbite; whereas 52 per cent of experimental animals escaped injury (no frostbite) and 32 and 16 per cent suffered only with primary and moderate degree of injury, respectively. None from this group suffered from severe or very severe frostbite. INTERPRETATION & CONCLUSION: It is evident from the study that this combined therapy resulted in significant improvement in the degree of tissue preservation and proved to be highly beneficial as an immediate treatment of frostbite in rats. The combined pharmacological properties of these drugs might have altered the haemorrheologic status of blood and produced curative beneficial effect in improving tissue survival. Clinical studies are required for confirmation of these beneficial effects in humans, which has already been taken up.

Animals↗
PubMedDate not supplied

The effect of rewarming media composition on the ammonia detoxification ability of cold preserved rat hepatocytes.

We examined how different media composition of rewarming solutions affected ammonium detoxification function, urea synthesis and the viability of hepatocytes after 72 hs of cold storage in UW solution. Freshly isolated rat hepatocytes were incubated at 37 C in a cell culture medium (MEM-E) with 3 mM glycine, 5 mM fructose and 2.5 mM adenosine (group 1) and in Krebs-Heinseleit buffer with 3 mM glycine, 5 mM fructose, 2 mM ornithine, 10 mM lactate and adenosine, that was used in two different concentrations: 2.5 mM (group 2) and 10 mM (group 3). We found that freshly isolated cells produced ammonium in group 1 and 2 but the cells were able to diminish ammonium extracellular concentration in group 3. Urea synthesis and ammonium extracellular concentration in group 1 was higher than in group 2. As a result of this observations, we used the Krebs-Heinseleit solution with addition of 10 mM adenosine to determinate the effect of hypothermic preservation on ammonium detoxification and urea synthesis ability of cells. In conclusion the addition of 2.5 mM adenosine into the rewarming medium interfered with the detection of ammonium detoxification of hepatic cells.

Adenosine↗
PubMed2000

Exercise after cryotherapy greatly enhances intramuscular rewarming.

OBJECTIVE: To determine the effect of moderate-intensity walking on rewarming of the triceps surae muscle group after a 20-minute application of a crushed-ice pack. DESIGN AND SETTING: Subjects were randomly assigned to either the ice-rest or the ice-exercise group. All subjects were treated on the left calf for 20 minutes with a 1.8-kg ice pack. The ice-exercise group walked on a treadmill at 5.63 km/h for 10 minutes and then assumed a prone position on an examining table for 20 minutes. The ice-rest group assumed a prone position on an examining table for 30 minutes after the cryotherapy treatment. SUBJECTS: Twenty-eight (19 men and 9 women) college-student volunteers. MEASUREMENTS: Intramuscular temperature was recorded at 10-second intervals for 50 minutes at 1 cm below the subcutaneous fat with a thermocouple implanted via a 21-gauge sterile hypodermic needle. Differences were analyzed within and between groups at pretreatment (T(0)), the end of the ice treatment (T(20)), 11 minutes after the end of ice treatment (T(31)), and 30 minutes posttreatment (T(50)). RESULTS: We found no differences at T(0) and T(20) but significant differences at T(31) and T(50). At T(31), the ice-exercise group was only 0.61 degrees C colder than at pretreatment levels, while the ice-rest group was 8.05 degrees C colder. By T(50), the temperatures were 0.93 degrees C and 6.95 degrees C colder, respectively, than at pretreatment levels. CONCLUSION: Moderate walking significantly enhanced rewarming of the triceps surae.

Journal Article↗
PubMed1991

Continuous arteriovenous rewarming: report of a new technique for treating hypothermia.

Survival is rare after major trauma if core temperature falls below 32 degrees C. Available rewarming methods are often ineffective. We utilized arterial and venous catheters to create a circulatory fistula through the heating mechanism of a modified commercially available counter-current fluid warmer to achieve simple, rapid extracorporeal rewarming.

Adult↗
PubMed1990

The effects of rewarming hypothermic postanesthesia patients using Thermadrape covering, heat lamps, and warmed cotton blankets.

The following article includes a brief review of hypothermia and describes contributing factors that cause hypothermia in the operating room as well as the methods used to rewarm patients in the PACU. Thermadrape coverings (OR Concepts, Inc, Roanoke, TX) were studied to determine if they were effective in maintaining body temperature within a normothermic range. Of 55 patients evaluated in the PACU, 18 (32%) who received Thermadrape coverings in the perioperative period remained normothermic. The methods used to rewarm postanesthesia patients included three combinations: Thermadrape and warmed cotton blankets, warmed cotton blankets and heat lamps, and warmed cotton blankets alone.

Bedding and Linens↗
PubMed1989

[A drowning accident of long duration with deep hypothermia and rewarming with extracorporeal circulation. A report of 2 patients].

Two nearly drowned, 2 9/12 and 3 6/12 years old boys with profound hypothermia were admitted to our pediatric intensive care unit with all signs of clinical death. Both patients could be rewarmed and oxygenated by extracorporeal circulation. One of them died 36 hours after the accident with severe brain edema. The second one survived without any defect. Rewarming of cold-water nearly-drowned patients by extra-corporeal circulation seems to be a very effective way of treatment.

Accidents↗
PubMed1986

Micropipette aspiration of human platelets: influence of rewarming on deformability of chilled cells.

Recent studies using micropipette elastimetry have shown that the circumferential microtubule supporting the discoid form of resting platelets has a direct influence on the resistance of the cell to deformation. However, the findings did not resolve whether the mere presence of microtubules, their organization into coils, or location under the cell wall was responsible for resistance to aspiration into micropipettes. In the present study platelets were cooled to 2 degrees to 4 degrees C to remove microtubules completely. The chilled cells were then rewarmed to 37 degrees C, and the influence of microtubule reassembly on resistance to deformation in micropipettes measured at intervals up to 1 hour. Chilled platelets without microtubules were aspirated more than twice as far as control platelets at all negative pressures from 1 to 10 cm H2O (tensions 4 to 41 X 10(-2) dynes/cm). At negative tensions beyond 32.5 X 10(-2) dynes/cm (8 cm H2O), the aspirated lengths of control platelets plateaued until the cells finally fragmented. Aspirated segments of chilled platelets continued to increase in length on exposure to greater negative pressure. Twenty minutes after rewarming at 37 degrees C, chilled cells began to return toward normal resistance to aspiration when only 6% had recovered discoid shape. The range of deformability at this time was narrow, indicating that partial recovery was not caused by development of two cell populations, one with and one without microtubules. The return toward normal resistance continued at 30 minutes when 75% of platelets were discoid, and was identical to that in control platelets after 1 hour at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗
PubMed1989

[The role of the heart in rewarming the body of hibernating animals upon arousal].

The heart of ground squirrels is covered by a large amount of brown adipose tissue during the whole period of hibernation. During arousal and rewarming of heterothermal rodents, the highest temperature is detected in the brown adipose tissue and in the heart. During hibernation the heart rate is 10-12/min. On arousal, beginning from the early stage when the heart temperature is still low, a significant increase in the heart rate occurs followed by acceleration of the body rewarming of heterothermal animals.

Adipose Tissue, Brown↗
PubMed1986

Effects of local convective cooling and rewarming on skin blood flow.

Local areas of the thighs, palms and fingertips of ten healthy subjects were exposed to cold (10 degrees C) and warm (40 degrees C) air flows of three different velocities, 0.25, 0.50 and 0.75 m/s. The rewarming followed immediately after the cooling. Each climatic condition was applied for 45 min. Skin blood flow and skin temperature were continuously measured by laser Doppler flowmetry and thermometry, respectively. Significant (p less than 0.01 or less) reductions in both skin blood flow and skin temperature, compared to the levels recorded in the room climate, were observed at all the test sites and for all the cooling climates. During cooling no significant differences were obtained between skin blood flow levels reached for the different air velocities, except for the palm (p less than 0.01). Rewarming by the air velocities 0.25 and 0.50 m/s could not even bring the palm skin blood flow back to the precooling levels, while the fingertip (except for the low air velocity) and the thigh showed a hyperaemic reaction. The discrepancies in response pattern between the test sites are interpreted to be due to their different microvasculature and vasomotor innervation. The relationship between skin blood flow and skin temperature was found to be exponential. The correlation coefficients were 0.84, 0.72 and 0.85 for the thigh, palm and fingertip, respectively.

Adolescent↗
PubMed1985

[The effect of rewarming of stored blood on plasma value and erythrocytes].

30 units of stored blood of different age were rewarmed from 4 degrees C to 32 degrees C by microwave blood-warmer Infusotherm 407. The resulting damage to blood components and change of function of erythrocytes were compared with those caused by storage of CPD-blood. Dependent on the age of stored blood we found considerable increases in the plasma-levels of potassium, lactate, and free haemoglobin. Compared with cold CPD-blood rewarming of stored blood produced a 7% increase in lactate and a 8% increase in free haemoglobin. There were no changes in platelet and erythrocyte counts, haematocrit, plasma-levels of haemoglobin, electrolytes, cholesterol, blood viscosity, osmotic resistance, and oxygen-binding capacity. As damage of stored blood produced by warming is minimal compared with that produced by storage, the Infusotherm 407 is considered to be a clinically useful blood-warmer.

Blood Cell Count↗
PubMed1978

Effects of hypothermia and rewarming on the neonatal circulation.

Thirteen unanesthetized lambs, aged 1-3 days, were cooled from 40 degrees to 30 degrees C and then rewarmed. During cooling, heart rate dropped from 196 +/- 47 to 140 +/- 42 beats per minute, a 29% change; cardiac output, femoral arterial and pulse pressures did not change significantly; but inferior vena cava pressure (IVC) increased from 5 to 9 mm of mercury, and left ventricular end diastolic pressure (LVEDP) increased from 8 to 25 mm/Hg. Mean pulmonary arterial pressure increased from 29 to 40 mm/Hg. Metabolic acidosis and hypoxia developed during the cooling. There were marked changes in the distribution of cardiac output; the proportion of cardiac output increased by 450% to brown fat, 66% to the skeletal muscles, and 30% to the right ventricular myocardium and atria. No significant change in the distribution to the left ventricule and septum was observed. Distribution to the other organs decreased markedly. After rewarming, all the previous parameters returned to normal except CVP and LVEDP, which remained elevated.

Acidosis↗
PubMedDate not supplied

[The relationship between oxygen consumption and the the rate of rewarming during extracorporeal circulation with induced hypothermia].

This study was performed to investigate the relation between total oxygen consumption (VO2) and the velocity of reheating in patients undergoing cardiopulmonary bypass with hypothermia. A total of 17 males undergoing this procedure were studied prospectively (mean age: 63 years, range: 52-72); during surgery they were cooled at 28 degrees C whole-body temperature. Before rewarming, patients were divided at random in two groups. Group A (n = 8) was reheated between 10 and 25 minutes, and group B (n = 9) between 26 and 50 minutes. In group A, VO2 expressed in ml.min-1 x m-2 increased from 76.6 +/- 6.99 at 28 degrees C until 100.0 +/- 6.72 at 34 degrees C; in group B increased from 68.4 +/- 4.55 until 129.1 +/- 4.73 at similar temperatures (analysis of variance: p < 0.01 at 28 degrees C). A greater VO2 in group B could indicate that slow rewarming would cause an even distribution of temperature with enough time for tissues to rid of their oxygen debt.

Aged↗
PubMed1976

[Rewarming of infusions with the haemotherm].

A rewarming device for blood called Haemotherm from the firm Bosch was proofed for efficiency. This device working on the base of microwaves was able to warm up cold solutions to a certain temperature within two to three minutes. The effect of rewarming disappeared during the passage through the infusion tube. To get bodywarm solutions at the end of the infusion tube was impossible with this arrangement.

Body Temperature↗
PubMed1995

Contribution of true cold and rewarming ischemia times to factors determining outcome after orthotopic liver transplantation.

The role of true cold ischemia times (CIT) and rewarming ischemia times (WIT) in determining outcome after liver transplantation was investigated in 230 adult recipients. Using multivariate analysis, WIT (time from the start of implantation until restoration of arterial and portal blood supply) and donor intensive care stay (P = .04 and .0004, respectively) but not CIT (the time from donor portal vein flushing until the graft was removed from University of Wisconsin solution; P > .30) emerged as independent determinants of graft survival. In the small number of patients with a WIT of greater than 180 minutes, there were reductions in graft survival (58% v 80% for WIT greater than 180 minutes) but these just failed to reach significance (P = .055). CIT had no influence on graft survival using cut-offs of 12 or 18 hours. A WIT of greater than 180 minutes was associated with an increased median area under the curve of day 1 through 7 serum bilirubin (1,370 v 915 mumol/L.day; P = .048) and trends towards an increased incidence of primary graft nonfunction or dysfunction (22.2% v 6.2% for WIT of less than 180 minutes; P = .065) and the day 1 through 7 area under the curve of serum aspartate aminotransferase (3,310 v 1,440 IU/L.day; P = .092). A prolonged CIT (greater than 18 hours) led to a prolonged hospital stay (69 v 31 days; P = .03), an increased area under the curve of day 8 through 14 serum bilirubin (2,500 v 995 mumol/L.day; P = .003), and a trend towards an increased incidence of initial poor graft function (33.3% v 6.3% for less than 18 hours; P = .092). The incidence of acute rejection increased (to 64.3% from 53.4%; P = .04) in patients with preservation injury (serum aspartate aminotransferase greater than 1,500 IU/L during the first 2 postoperative days). True CIT and WIT are important determinants of outcome after liver transplantation.

Adenosine↗