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PubMed2006

Effect of a short period of abstinence from smoking on rewarming patterns of the hands following local cooling.

The purpose of the study was to examine the effect of a 12 h period of abstinence from smoking in young and old habitual smokers, on skin rewarming patterns of a hand following local cooling. This was done by comparing changes in peripheral circulation, measured indirectly by monitoring changes in skin surface temperatures of the hand with both infrared (IR) thermography and thermocouples before, during and after immersing the right hand for 2 min in water at 10 degrees C. Included in the study were young male non-smokers (n = 14) and smokers (n = 13), and elderly non-smokers (n = 12) and smokers (n = 14). The results showed no statistically significant difference between young non-smokers and smokers when comparing their response to the local cold challenge. The elderly smokers had a significantly higher hand skin temperature prior to cooling (34.0 +/- 0.2 degrees C) and after 80% rewarming (32.1 +/- 0.2 degrees C) (i.e. when the skin temperature in the "cooled" hand has regained 80% of the cold induced drop in temperature), compared to elderly non-smokers (33.3 +/- 0.2 and 31.3 +/- 0.2 degrees C, respectively). The elderly smoking subjects also had a faster recovery after cooling (9.7 +/- 0.8 min) than the elderly non-smoking subjects (16.7 +/- 2.6 min). A follow-up study with seven elderly smokers, who had smoked as usual until 2 h before the experiment, showed responses lying between the non-smokers and smokers who had had a longer period of abstinence (12 h) from smoking. In conclusion, we have demonstrated using IR-thermal imaging that elderly subjects who have smoked for many years have slightly warmer hand skin temperature when they abstain from smoking. Even a period of abstinence from smoking of a few hours can affect the way in which elderly subjects respond to a local cold challenge, recovering more rapidly then their non-smoking counterparts.

Adaptation, Physiological↗
PubMed1991

Perfusion without systemic heparinization for rewarming in accidental hypothermia.

We report on a patient with accidental deep hypothermia (23.3 degrees C) and cardiorespiratory arrest resulting from severe craniocerebral injury. Systemic anticoagulation was contraindicated, and the decision was reached to rewarm the patient with cardiopulmonary bypass without systemic heparinization using heparin-coated perfusion equipment. The patient was successfully rewarmed, was weaned from cardiopulmonary bypass, and recovered.

Adolescent↗
PubMed1987

Dielectric measurements for the design of an electromagnetic rewarming system.

The work described in this paper is intended to provide a basis for the design of a controlled rewarming system for cryopreserved tissues and organs using electromagnetic energy. For rapid rewarming (say, greater than 10 degrees C/min), the temperature distribution in the organ is effectively determined by the uniformity (or otherwise) of the power deposition, which is in turn controlled by the electrical properties of the perfused tissue. In this contribution, we describe the measurement system we have used to characterize the electrical properties of perfusates and perfused rabbit kidney tissue from -30 to +20 degrees C. Measurements have been made on three perfusates using an open-ended coaxial probe sensor over a continuous range of radio and microwave frequencies covering 50 MHz to 2.6 GHz. Results show that the behavior of the electrical properties with increasing temperature is unfavorable at either end of the frequency range investigated--either the power absorption has a positive temperature coefficient or the penetration depth is too shallow. However, there is a compromise frequency range, determined in part by the perfusate composition, where these factors are much less serious. In this frequency range, the electrical properties of the perfused tissue are dominated by the properties of the perfusate. Modifications to the perfusate composition, e.g., reducing the concentration of electrolytes by adding sucrose, can further improve the temperature dependence of the electrical properties.

Animals↗
PubMed1977

Adrenergic mechanism in cold stored taenia caecum after rewarming.

After cold storage of guinea-pig taenia strips for 4 days at 2 degrees C, structures with specific catecholamine fluorescence were not observed. Upon incubation in Krebs Ringer medium (37 degrees C) the fluorescence in the cold stored tissue reappeared and the density of fluorescence was comparable to that of fresh preparations. The specific fluorescence was affected following reserpine or 6-hydroxydopamine treatment; however, the rewarming process restored fluorescence only in the reserpine-treated tissue. The cold storage treatment (4 and 7 days) also decreased the tissue noradrenaline and dopamine contents and dopamine-beta-hydroxylase activity and inhibited the [3H-noradrenaline release from the tissue, all of which were not restored by the incubation procedure. Moreover, in these cold stored taenia the inhibitory effect to nicotine and perivascular nerve stimulation were not manifested. Therefore, the reappearance of specific fluorescence in the cold stored taenia strips after rewarming does not assure functional recovery of adrenergic nerve activity.

Animals↗
PubMedDate not supplied

The effects of convective cooling and rewarming on systemic and central nervous system physiology in isoflurane-anesthetized dogs.

Recent studies have demonstrated that small (i.e., 2-5 degrees C) reductions in temperature may protect the brain and spinal cord from ischemic injury. The present study evaluated the physiologic response of anesthetized animals to convective-based cooling and warming. Six shaved, isoflurane-anesthetized (1.50% end-expired; 1 MAC), pancuronium-paralyzed dogs were subjected to temperature manipulation. The flow of cool (13-14 degrees C) or warm (39-41 degrees C) air was uniformly applied to the the dorsal and lateral surfaces of the dog using an inflatable blanket with perforations in the interior surface. Convective cooling reduced pulmonary artery temperature (Tpa) from 37.0 +/- 0.2 degrees C (Mean +/- S.D.) to 33.0 +/- 0.0 degrees C over a 93 +/- 18 min period. Thereafter, the active cooling was discontinued and passive cooling resulted in a further reduction in Tpa to 32.4 +/- 0.3 degrees C over the next 60 min. Institution of convective warming resulted in an increase in Tpa from 32.4 +/- 0.3 to 33.0 +/- 0.0 degrees C in 23 +/- 14 min and from 33.0 to 37.0 +/- 0.0 in an additional 137 +/- 26 min. During the periods of active cooling, passive cooling and active warming, there were strong correlations between Tpa and temperature within the brain, cisterna magna, parietal epidural space, lumbar subarachnoid space and other commonly used temperature measurement sites non-invasively monitored (e.g. tympanic membrane, esophagus, rectum) r greater than or equal to 0.97; P less than 0.0001). The combination of isoflurane anesthesia (a potent EEG-suppressor) plus mild hypothermia (less than 34 degrees C) resulted in an EEG attenuation in five dogs, two of which progressed to burst suppression. The magnitude of EEG changes correlated with the degree of temperature reduction. Upon rewarming to 37 degrees C, all dogs had normal EEG activity and normal brain concentrations of high energy phosphates, glucose and lactate. Blood pressure and cardiac output did not change during the study and no dog exhibited acid-based anomalies or blood lactate accumulation. Whole body oxygen consumption and heart rate decreased in a temperature-dependent fashion. Cardiac rhythm disturbances were rare. The authors conclude that convection-based corporeal cooling and rewarming are efficacious methods for non-invasively and uniformly altering CNS temperatures without adversely affecting cerebral or systemic physiology.

Anesthesia↗
PubMedDate not supplied

Rewarming by hemodialysis for hypothermia: failure of heparin to prevent DIC.

Disseminated intravascular coagulation (DIC) is an infrequent but known complication of hypothermic injury. Previous work with a dog model had indicated that DIC could be prevented if the animals were treated with heparin prior to rewarming. We report here the case of a young man treated with core rewarming by hemodialysis who developed DIC despite the use of heparin during dialysis.

Adult↗
PubMed1988

Effects of systemic morphine and epidural bupivacaine on postoperative oxygen consumption during rewarming.

The alterations in hemodynamics and oxygen consumption as a consequence of continuous epidural infusions of bupivacaine at room temperature and conventionally administered morphine were studied during recovery from general anesthesia for total hip replacement. Twenty-four patients were randomized to receive either bupivacaine or morphine in the recovery room. The bupivacaine group received from 6 to 12 ml per hour of 0.25% bupivacaine epidurally. Patients in the morphine group received 0.1 mg/kg of morphine intramuscularly no more frequently than every 4 hours. A pulmonary artery flotation catheter was inserted into each patient to determine hemodynamics and oxygen consumption at three instances: before analgesia, when pulmonary artery blood temperature reached 36 degrees C, and when it reached 37 degrees C. During the rewarming there was a decrease in mean arterial blood pressure and the systemic vascular resistance index and an increase in heart rate. The whole body oxygen consumption index increased in the bupivacaine group at the last measuring point but was stable in the morphine group. There was no effect on the arterial-venous oxygen content difference in either group. At 37 degrees C, the cardiac index and oxygen consumption index were significantly higher in the bupivacaine group than in the morphine group. In contrast to regional analgesia, systemic morphine administration can partially antagonize cardiovascular response to postoperative rewarming because it induces a stable oxygen demand.

Aged↗
PubMed1975

Electrocardiographic changes during surface-induced deep hypothermia. The influence of ether, halothane, carbon dioxide, and perfusion rewarming.

The influence of halothane, ether, carbon dioxide, and perfusion rewarming on the electrocardiogram was studied in 37 dogs subjected to surface-induced deep hypothermia. Significant anesthetic-related differences in P-R, QRS, Q-T and R-R intervals during cooling were not apparent; however, reduced arterial pressure, ventricular fibrillation, and a greater tendency for bradycardia requiring supportive measures were noted at low temperatures with halothane anesthesia. The use of 95% O2/5% CO2 significantly reduced the QTc at low temperatures; Other phenomena, including the occurrence and significance of J waves, are discussed. The relationship of the electrocardiogram to clinical and pathological results was evaluated and indicates that (1) properly managed resuscitation (manual massage and defibrillation) is not a serious hazard, (2) ether in 100% oxygen is the agent of choice for surface-induced deep hypothermia with prolonged circulatory arrest, and (3) halothane may be used in a procedure combining surface cooling and perfusion rewarming if given in a mixture of oxygen and carbon dioxide.

Anesthesia, Inhalation↗
PubMed1997

Effects of cold preservation and rewarming on rat liver cell volume regulation and concentrative amino acid uptake.

BACKGROUND & AIMS: Liver graft dysfunction is related to hypothermic preservation and may implicate altered cell volume homeostasis. The aim of this study was to evaluate how cold preservation and rewarming affect hepatocellular volume regulation and concentrative amino acid uptake. METHODS: Rat hepatocytes suspended for variable times in cold preservation solution were subsequently cultured at 37 degrees C. Cell viability was assessed by trypan blue exclusion. Cell volume was measured by videoplanimetric analysis of microscopic images. Amino acid uptake was assessed by measuring Na+-dependent cell swelling. RESULTS: Cell viability decreased as a function of cold storage time even as early as 4 hours. Upon hypotonic stress, cells swelled similarly irrespective of preservation time. However, the rate of subsequent regulatory volume decrease diminished significantly with increasing preservation time. Upon return to isotonic perfusate, cells shrunk to a similar extent, but the rate of regulatory volume increase was halved by cold storage beyond 24 hours. The rate of proline-induced cell swelling was diminished greatly after cold storage, unlike that induced by aminoisobutyric acid and glutamine. CONCLUSIONS: Hepatocellular volume regulatory mechanisms and concentrative proline uptake are significantly impaired after cold preservation and rewarming, unlike alpha-aminoisobutyric acid and glutamine uptake. This may favor chronic cell swelling after transplantation and participate in liver graft dysfunction.

Amino Acids↗
PubMed1989

Early extubation after coronary artery surgery in efficiently rewarmed patients: a postoperative comparison of opioid anesthesia versus inhalational anesthesia and thoracic epidural analgesia.

Twenty-eight patients were studied after uncomplicated aortocoronary bypass surgery with hypothermic cardiopulmonary bypass (CPB). In all patients residual hypothermia was effectively treated by the use of extended rewarming during CPB and postoperatively by an external heat source. This treatment almost eliminated postoperative shivering, and it resulted in the lowering of oxygen uptake, carbon dioxide production, and required ventilatory volumes to stable levels where spontaneous breathing could be used safely. The patients were divided into two groups. In group I (n = 12), intraoperative anesthesia was based on an intravenous (IV) opioid (phenoperidine), which caused persistent respiratory depression and made mechanical ventilation necessary for a mean postoperative time period of 10.7 +/- 3.8 hours even with the rewarming. In group II (n = 16), thoracic epidural analgesia and intraoperative general anesthesia with enflurane were used. In this group, postoperative metabolic and ventilatory requirements were stable and low, finger skin temperature was normalized earlier, systemic vascular resistance was lower, and stroke index was higher. Emergence from anesthesia was uneventful and was achieved early postoperatively in Group II. The patients had good pain relief and were mentally alert. Adequate spontaneous breathing was resumed quickly and endotracheal extubation was performed within the first two postoperative hours (1.6 +/- 0.5 hours). No complications or increased morbidity occurred, and no patient needed to be reintubated in Group II.

Analgesia, Epidural↗
PubMed1995

Methods of rewarming the hypothermic patient in the accident and emergency department.

Hypothermia, occurring when the core body temperature falls below 35 degrees C, gives rise to life threatening physiological changes, and may present in the Accident and Emergency (A & E) department with varying aetiology and implications for nursing management. Rewarming the hypothermic patient is a priority of nursing care, and several different ways of achieving this are practised. This review of relevant literature aims to evaluate current methods of rewarming hypothermic patients commonly employed, their associated difficulties, and considers their potential implementation in the A & E setting.

Emergency Nursing↗
PubMed1975

The cooling, analgesic, and rewarming effects of ice massage on localized skin.

The study was designed to produce objective data on the rate of local cooling following the ice massage technique of cold application and the rate of rewarming following termination of the ice application. More importantly, the onset of skin analgesia and its duration were evaluated. Sixteen normal subjects participated in four testing sessions, two of which were control session. A thermistor unit with probes monitored skin temperature and a standardized pain-evoking stimulus was used to verify analgesia. Analgesia was elicited by the ice massage only after the localized region had been cooled to, and maintained below, 13.6 degrees Celsius. The rate of cooling for the localized skin was more rapid than the rate of rewarming. The ten-minute ice massage was an effective procedure in achieving analgesia and, thus, may be sufficient to permit therapeutic exercise of selective painful conditions during, and for approximately three minutes immediately following, application.

Adolescent↗
PubMed1997

Spinal anesthesia speeds active postoperative rewarming.

BACKGROUND: Redistribution of body heat decreases core temperature more during general than regional anesthesia. However, the combination of anesthetic- and sedative-induced inhibition may prevent effective upper-body thermoregulatory responses even during regional anesthesia. The extent to which each type of anesthesia promotes hypothermia thus remains controversial. Accordingly, the authors evaluated intraoperative core hypothermia in patients assigned to receive spinal or general anesthesia. They also tested the hypothesis that the efficacy of active postoperative warming is augmented when spinal anesthesia maintains vasodilation. METHODS: Patients undergoing lower abdominal and leg surgery were randomly assigned to receive general anesthesia (isoflurane and nitrous oxide; n = 20) or spinal anesthesia (bupivacaine; n = 20). Fluids were warmed to 37 degrees C and patients were covered with surgical drapes. However, no other active warming was applied during operation. Ambient temperatures were maintained near 20 degrees C. After operation, patients were warmed with a full-length, forced-air cover set to 43 degrees C. Shivering, when observed, was treated with intravenous meperidine. RESULTS: The mean spinal analgesia level, which was at the sixth thoracic level during surgery, remained at the T12 dermatome after 90 min after operation. Core temperatures did not differ significantly during surgery and decreased to 34.4 +/- 0.5 degrees C and 34.1 +/- 0.4 degrees C, respectively, in patients given spinal and general anesthesia. After operation, however, core temperatures increased significantly faster (1.2 +/- 0.1 degrees C/h vs. 0.7 +/- 0.2 degrees C/h, mean +/- SD; P < 0.001) in patients given spinal anesthesia. Consequently, patients given spinal anesthesia required less time to rewarm to 36.5 degrees C (122 +/- 28 min vs. 199 +/- 28 min; P < 0.001). CONCLUSIONS: Comparable intraoperative hypothermia during general and regional anesthesia presumably resulted because the combination of spinal anesthesia and meperidine administration obliterated effective peripheral and central thermoregulatory control. Vasodilation increased the rate of core rewarming in patients after operation with residual lower-body sympathetic blocks, suggesting that vasoconstriction decreased peripheral-to-core heat transfer after general anesthesia.

Adult↗
PubMed1982

Accidental hypothermia treated with rapid rewarming by immersion.

Eighteen consecutive hypothermia patients were treated with rapid rewarming by immersion. Continous electrocardiographic monitoring, acid-base and central venous pressure measurements, vital signs, and fluid resuscitation with lactated Ringer's solution (tritrated to urine output) were employed as part of the therapeutic regimen. This regimen was associated with a single mortality. Rapid rewarming by immersion appears to be a safe, effective, and relatively simple method for treating accidental hypothermia victims.

Acid-Base Equilibrium↗
PubMed1987

Treatment of hypothermia by extracorporeal circulation and internal rewarming.

The treatment of accidental hypothermia by extracorporeal circulation and internal rewarming can be life saving in patients unconscious from drug overdose or victims of accidental exposure to severe cold. Advantages are the rapidity of treatment, the provision of circulatory support, and a lessened chance of rewarming collapse, since peripheral vasodilation is paralleled by an increase in cardiac output. A premature diagnosis of clinical death was averted in two patients with rectal temperatures of 25 degrees C or below, and their lives were saved by the use of this technique.

Adult↗
PubMed1992

Continuous arteriovenous rewarming: rapid reversal of hypothermia in critically ill patients.

Hypothermia in critically ill patients can be difficult to treat with standard rewarming (SR) techniques. We developed a rewarming method that is significantly faster than SR. Percutaneously placed femoral arterial and venous catheters were connected to the inflow and outflow side of a countercurrent fluid warmer to create a fistula through the heating mechanism (CAVR). Over a 10-month period 34 hypothermic (temperature less than 35 degrees C) patients were treated. Eighteen received SR only; CAVR was added to SR in the remaining 16 patients. Both groups were similar in APACHE II, Injury Severity, and Acute Physiology scores, prewarming blood and fluid requirements, and incidence of coagulopathy. Hypothermia resolved in 39 minutes with CAVR vs. 3.23 hours with SR (p less than 0.001). This was associated with an improved survival after moderately severe injury (p = 0.04), and a significant reduction in blood and fluid requirements, organ failures, and length of ICU stay.

Adult↗
PubMed1992

Design of a UHF applicator for rewarming of cryopreserved biomaterials.

The dielectric properties of cryopreserved biological tissue are discussed in relation to the problems which arise when EM fields are used for rapid rewarming. The UHF band is favored from two aspects: the avoidance of thermal runaway and the uniformity of heating inhomogeneous material. Various resonant cavity applicators are considered for efficient and uniform rewarming. The square-aspect TE 111 cylindrical applicator is favored principally because it allows variation of the E-field orientation as required during the warming profile. An appropriate kidney phantom organ is described. It is used to obtain measured values of the overall efficiency of a TE 111 applicator. The efficiency values are found to fall steadily with increasing temperature from 85% at -40 degrees C to 45% at the phase change, mainly due to the decreasing tan delta value of the phantom material.

Animals↗
PubMed1991

A comparison of patient rewarming devices after cardiac surgery.

Three regimens for rewarming patients after cardiac surgery involving hypothermic cardiopulmonary bypass were studied in 30 patients. The control group (n = 10) received no active rewarming, the oesophageal group (n = 10) was warmed centrally using an oesophageal heat exchanger and the radiant group (n = 10) was warmed peripherally with an overhead radiant heater. There were no statistically significant differences between the groups apart from the higher mean skin temperatures in the peripheral group.

Body Temperature↗