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At least 19 recordsLinked to original sources

PubMed1991

Efficacy and safety of prehospital rewarming techniques to treat accidental hypothermia.

STUDY OBJECTIVE: Evaluation of inhalation rewarming and peripheral rewarming for reducing the body core temperature afterdrop and accelerating rewarming rates. DESIGN: Prospective, randomized human experimentation. SETTING: Physiology laboratory with cooling during ice water immersion and rewarming in rescue sleeping bags in a windy, cold (2 C) air environment. TYPE OF PARTICIPANTS: Eight experimental subjects who were cooled to clinical hypothermia (35.0 C), rectal or esophageal temperature (Tr or Te). MEASUREMENTS AND MAIN RESULTS: Afterdrop was characterized as minimum Tr and Te plus recovery time to the Tr and Te levels at the onset of rewarming. Rewarming rates 30 and 60 minutes after maximum afterdrop for Tr and Te were measured. By analysis of variance, inhalation rewarming and peripheral rewarming evaluated separately or in combination did not significantly influence afterdrop duration, afterdrop recovery, or rewarming rates. CONCLUSION: With no physiological benefit and hazards identified (inhalation rewarming burning the face, peripheral rewarming eliminating carbon monoxide equal to 300 to 600 ppm), inhalation rewarming and peripheral rewarming are not recommended for the prehospital treatment of mild hypothermia.

Accidents↗

PubMed1979

Accidental hypothermia and rewarming in dogs.

1. Twenty lightly anaesthetized dogs were cooled to 29 degrees C by cold-water immersion. Ventilation was spontaneous and the animals were allowed to shiver freely. Metabolic heat production and respiratory heat exchange were measured during rewarming. 2. The animals were divided into four groups each of five dogs and each group was rewarmed by a different technique. The control group was allowed to rewarm spontaneously; a second group was given warm (45-50 degrees C) fully humidified air to breathe in addition; a third group was rewarmed in a hot-water bath (42-44 degrees C) and the remaining group was given in muscle relaxant to abolish shivering and rewarmed by warm inspired air only. 3. The group rewarmed in hot water achieved normal core temperature most rapidly but there was no difference in the rewarming rates of the group rewarmed spontaneously and of the group given warm air to breathe in addition. 4. The group given a muscle relaxant and rewarmed with warm inspired air required 12 h to achieve the same core temperature as the shivering groups achieved in 2 h. Compared with the heat produced by shivering the amount of heat which it was possible to transfer across the respiratory tract was so small that it did not materially influence the rate of rewarming.

Animals↗

PubMed1992

Comparison of four noninvasive rewarming methods for mild hypothermia.

Four noninvasive rewarming techniques for mildly hypothermic subjects were compared. Seven subjects were cooled in a water bath of 15 degrees C for 2 h to an average esophageal temperature (Tes) of 36 degrees C. Thereafter, the subjects were rewarmed by immersion of the body in a water bath of 42 degrees C (Method 1), the body but not the extremities in water of 42 degrees C (Method 2), only the extremities in water of 42 degrees C (Method 3), or spontaneous rewarming in blankets (Method 4). Method 1 showed the highest rewarming rate in Tes (10.1 degrees C/h) and an afterdrop in Tes of 0.18 degrees C. Method 2 showed the same afterdrop, but a lower rewarming rate (7.5 degrees C/h). In Method 3, the heat uptake of the extremities was too low to rewarm the subjects effectively. The afterdrop and rewarming rate were 0.38 degrees C and 0.8 degrees C/h, respectively. Method 4 had the lowest rewarming rate (0.2 degrees C/h), and an afterdrop (0.14 degrees C) which was not significantly lower than that of Method 1 or 2. Therefore, Method 1 is recommended for rewarming mild hypothermic subjects because of its high rewarming rate and small afterdrop.

Adult↗

PubMed1978

Laboratory comparison of technique for rewarming hypothermic casualties.

The efficacy of inhalation, hot bath, piped suit and spontaneous rewarming have been directly compared under controlled conditions. Hot bath rewarming was significantly more effective at raising deep body temperature than the piped suit technique and both were more effective than the other two methods. The effect of inhalation rewarming was not significantly different from that of spontaneous rewarming. All techniques gave rise to afterdrops of core temperature of widely varying degrees and durations. It is concluded that inhalation rewarming should not be employed if it entails a delay in transporting a patient to a facility for rapid external rewarming. Piped suit rewarming is a convenient field alternative to the use of a hot bath and a simple apparatus for carrying this out is described. The sluggish response of rectal temperature to cooling and rewarming in this study suggests that it should not be relied upon as the sole indicator of a patient's thermal state during treatment. Auditory canal temperature is a more valid substitute.

Adolescent↗

PubMed1975

Accidental hypothermia: an experimental study of inhalation rewarming.

Inhalation rewarming of hypothermic humans with heated, humidified oxygen was compared to rewarming by immersion in a hot bath. In 10 subjects cooled to approximately 35 degrees C core temperature, there was no significant difference in the amount of temperature "afterdrop" with the two rewarming procedures. Inhalation rewarming provided rapid commencement of increase in tympanic and esophageal temperatures, indicating effective rewarming of critical core regions, especially heart and brain. This method of core rewarming avoids the physiological hazards associated with the peripheral vasodilation which accompanies external rewarming. Moverover the simplicity of application of this method suggests its greater use in both first-aid and hospital treatment of accidental hypothermia.

Accidents↗

PubMed1991

Hemodynamic and metabolic effects of hypothermia and rewarming.

There is a lack of detailed knowledge of the pathophysiologic mechanisms initiated during and after rewarming. To study cardiac function after rewarming from hypothermia sodium pentobarbital anesthetized open chest-dogs were cooled to 25 degrees C and rewarmed. Myocardial blood flow was measured at different temperatures, and blood samples were drawn from the aorta and the coronary sinus for metabolic measurements. Mean aortic blood pressure (AOP) and aortic blood flow were recorded. Compared to precooling, AOP and heart rate were both significantly reduced during hypothermia. During rewarming stroke volume (SV) decreased significantly. At the end of rewarming AOP and SV were significantly lower than before cooling and myocardial blood flow, as well as oxygen and lactate uptake were only 50% of precooling levels. The present study demonstrated that hypothermia and rewarming depress cardiovascular function. Changes in peripheral vascular function, myocardial metabolism and contractility, may lead to the observed reduction in recovery upon rewarming.

Animals↗

PubMed1991

[Successful rewarming technique of isolated rat hearts following a long term preservation--calcium increase in a step-wise fashion].

This study was designed to evaluate the successful rewarming technique of isolated rat hearts which was preserved for 24 hour. Isolated rat hearts preserved with hydroxy ethyl starch (3g/dl) solution at 15 degrees C, was rewarmed and calcium concentration of the perfusate was increased in a step-wise fashion from 0.25 to 2.5mM every 5 minutes. Other hearts were also rewarmed and perfused with normal calcium (2.5mM) solution, throughout the rewarming period. The hearts perfused with normal calcium solution contracted a few times, and then severely contractured. The heart lost its color and acquired a pale and mottled appearance. On the other hand, the hearts perfused low calcium solution started beating spontaneously, and their heart rate and left ventricular pressure was increased gradually according to the calcium increase. In addition, re-introduction of normal calcium concentration did not change the cardiac parameters. This results indicated that step-wise increase of calcium concentration of the perfusate prevented heart contracture after rewarming and was a useful rewarming technique.

Animals↗

PubMed1992

Effects of hypothermia and rewarming on phospholipase C-evoked glycerol output in rat myocardial cells.

The combined action of phosphatidylcholine preferring phospholipase C (PC-PLC) and intracellular lipases has recently been shown to cause glycerol output in energy deprived rat cardiomyocytes. In the present study we examined the effect of hypothermia and rewarming on PC-PLC evoked glycerol output in freshly isolated, calcium-tolerant myocytes. The cells were preincubated for 60 min at hypothermic (5 degrees C) or normothermic (37 degrees C) conditions in Krebs-Henseleit bicarbonate buffer (pH 7.4) supplemented with 1 mM DL-carnitine, 1% B.S.A. and 5 mM glucose. Addition of PC-PLC resulted in a significantly higher (P less than 0.05) output of glycerol in myocytes undergoing rewarming than in myocytes kept constantly at 5 degrees C or 37 degrees C. The values obtained for PC-PLC induced glycerol output (difference in glycerol output between incubations with and without PC-PLC) were 6.77 +/- 2.6 (37 degrees C), 4.54 +/- 1.7 (5 degrees C) and 22.85 +/- 5.9 (5-37 degrees C) nmol/10(6) cells.h. Rewarming in addition caused a significantly higher (P less than 0.05) leakage of lactate dehydrogenase (LDH) from the rewarmed cells as compared to cells at constant temperatures (5 degrees C or 37 degrees C). However, there was no additional effect of PC-PLC on LDH leakage. The elevated PC-PLC induced glycerol output in rewarmed myocytes was not related to a fall in the percentage of rod-shaped cells or a reduced cellular content of ATP, since no differences could be detected between the various myocyte preparations with respect to these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1979

Thermal increment provided by inhalation rewarming from hypothermia.

To quantify the core temperature gain derived from inhalation rewarming, 10 subjects were immersed in seawater (mean temperature 12 degrees C) until a 2 degree C drop in rectal temperature occurred, and were then rewarmed by breathing hot saturated air at 45 degrees C for 30 min. Each subject was rewarmed once breathing air and once rebreathing a controlled fraction of expired air adjusted to produce a hyperventilation of 50 l/min. After 30 min of rewarming mean rectal temperature had increased 0.39 degrees C in subjects breathing air compared with 0.77 degrees C in those hyperventilating (P less than 0.01). Corresponding gains in tympanic temperatures were 1.1 and 1.5 degrees C, respectively. Calculations indicate that the additional heat input with hyperventilation yielded a core (rectal) temperature gain of 5.1 X 10(-4) degrees C/l. It is concluded that each additional 10 l/min of ventilation of hot saturated air will increase the rate of core rewarming from hypothermia by approximately 0.3 degrees C/h.

Adult↗

PubMed1979

An improved method for inducing hypothermia and rewarming.

A hypothermia and rewarming system combining body surface and ventilatory heat exchange is described. The method utilizes body surface heat exchange through conduction, convection, and black body radiation, and ventilatory heat exchange across the lung surface through conduction, convection, and water evaporation. The system consisted of a chamber in which the temperature was maintained at a desired level (+/- 2.5 degrees C) using a refrigeration-heat pump unit. Chamber temperatures during cooling and rewarming were -15.5 +/- 2.7 degrees C and 43.2 +/- 2.3 degrees C, respectively. Inhalate temperatures during cooling were -8.2 +/- 6.5 degrees C and during rewarming they were 41.5 +/- 0.3 degrees C. Helium (100%) was supplied to the chamber, while the animal was ventilated with 20% O2 + 80% He. Under these conditions, the cooling and rewarming rates were 0.33 +/- 0.06 degrees C/min and 0.20 +/- 0.04 degrees C/min, respectively, at 38--21 degrees C. The system provided for rapid cooling and rewarming with no evidence of any untoward effects.

Animals↗

PubMed1978

Effect of rewarming at various water bath temperatures in experimental frostbite.

Studies have been conducted on 72 rats to determine the most suitable temperature at which rapid rewarming should be done as an immediate treatment for frostbite. Animals were put in a harness containing arrangements for warming the body. Their hind limbs were left out of the harness. They were then exposed to -15 degrees +/- 1 degrees C in a deep freeze for 60 min, during which paw temperature was recorded every 5 min. After this, the animals were taken out, the left hind limb was rapidly rewarmed in a water bath maintained at 35 degrees, 37 degrees, 39 degrees, 41 degrees, 43 degrees, or 45 degrees C for different batches and the right hind limb was left free for slow rewarming at room temperature (27 degrees -29 degrees C). The severity of cold injury in the two limbs was compared. The paw temperature showed a drop on cold exposure, followed by a rapid rise and then a second fall. The degree of injury was related to the duration of exposure after the rise in the paw temperature. The rapid rewarming was effective only at water bath temperature of 37 degrees-39 degrees C and was harmful at 45 degrees C. This shows that rewarming at about body temperature is most effective as immediate treatment for frostbite.

Animals↗

PubMed1976

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↗

PubMed1991

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↗

PubMedDate not supplied

Physiologic effects of deep hypothermia and microwave rewarming: possible application for neonatal cardiac surgery.

Deep hypothermia (20 C) without cardiopulmonary bypass is a valuable technique during cardiac surgery in infants but rewarming of the heart following circulatory arrest and cardiac repair has traditionally been a lengthy and difficult process. In experimental animals rewarming the heart with microwave energy, as reported in this work, warms the heart before warming the periphery. In 18 mongrel dogs that were surface cooled to 20 C, we found that during microwave rewarming the core temperature rose 4.7 C per hour. Whole body oxygen consumption, heart rate, and cardiac output returned to normal at rates equal to the rates at which they decreased during surface cooling. Blood pressure and arterial gases remained adequate. Microwave rewarming appears to be a useful method for reestablishment of cardiac function and normothermia following deep hypothermia.

Animals↗

PubMed1976

Heparinless, oxygenatorless perfusion rewarming following surface-induced deep hypothermia for open-heart surgery.

To facilitate perfusion rewarming without the use of total body heparinization or an oxygenator following open-heart correction with surface hypothermia, we divised a pump circuit. The circuit, totally primed with 100 c.c. of saline, consists of polyurethane-polyvinyl-graphite (PPG) coated Tygon tubes (with one end tapered by heat treatment) and a copper-coil heat exchanger. A roller pump was used to achieve partial bypass from the left atrium to the ascending aorta with flow rates up to 70 c.c. per kilogram per minute. Experiments in dogs resulted in rapid rewarming, immediate return of cardiac function, and hematologic alterations similar to those noted during surface rewarming. The safety of the method was also demonstrated. Prothrombin time, partial thromboplastin time, and platelet values returned to control levels upon rewarming, and no thromboemboli or bleeding problems were noted. Six clinical experiences were accumulated. Details of the method, hematologic and blood chemical analyses in dogs, and the first clinical trial in a 3-month-old infant with transposition of the great vessels are reported.

Animals↗

PubMed1991

Hypothermia and rewarming after cardiac operation.

Those caring for patients who undergo cardiac surgery share a dilemma. Complications associated with hypothermia encourage the care giver to rewarm the patient quickly, but complications associated with rapid temperature changes and hyperthermia can threaten the patient's hemodynamic stability. What are adequate rewarming measures, when to terminate active rewarming measures to avoid hyperthermia, and what is the optimal rate of rewarming are all unanswered questions. Continued nursing research will expand the science of nursing and provide care givers with knowledge for expert care. As the turn of the century approaches and surgical techniques advance, high-risk patients who undergo reoperation and multi-valve cardiac surgery require expert nursing care.

Body Temperature↗

PubMed1991

Membrane phospholipid metabolism of rat myocardial cells during hypothermia and rewarming.

The phospholipid bilayer of the plasma membrane plays an important role in forming a functional barrier against leakage of ions and other cell constituents. We have examined the effect of an exogenously added phospholipase C (PLC) on phospholipid degradation in isolated rat myocardial cells subjected to hypothermia (5 degrees C) and hypothermia followed by rewarming to 37 degrees C. The activity of PLC was measured as glycerol output to the incubation medium since the combined action of PLC and endogenous lipases will result in glycerol production. Addition of PLC resulted in a significantly higher output of glycerol in rewarmed myocytes than in myocytes kept constantly at 5 degrees C and 37 degrees C. Rewarmed cells also showed the highest leakage of lactate dehydrogenase (LDH), but there was no additional effect of PLC on LDH leakage. Normal levels of cellular ATP were maintained in all myocyte groups. These results show that rewarming from hypothermia may cause structural derangements in the phospholipid bilayer of the sarcolemma which in turn could favor attack by endogenous phospholipases.

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↗