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At least 253 records · Page 14Linked to original sources
PubMed1997

Different effect of cold storage and rewarming on three pH regulating transporters in isolated rat hepatocytes.

Disturbances in hepatic pH homeostasis are thought to participate in the functional damage to liver grafts caused by the cold preservation and warm reperfusion necessitated by transplantation surgery. We have used an in vitro model of isolated rat hepatocytes suspended in cold University of Wisconsin (UW) solution and subsequently cultured at 37 degrees C to evaluate liver cell pH regulatory mechanisms after cold preservation and rewarming. Cells were kept for up to 72 h in cold UW solution, and at 24-h intervals intracellular pH (pHi) was measured after 60-90 min of warm culture by cytofluorometry using the fluorochrome 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. When challenged with an alkaline load by isohydric HCO(3)(-)-CO(2) steps, hepatocytes exhibited similar maximal pH(i) values and recovered at the same rate, irrespective of cold storage time, indicating that Cl-/HCO(3)- exchange activity is quite resistant to hypothermic storage and subsequent rewarming. In parallel studies, cells were subjected to an acid load by the NH4Cl pulse technique in bicarbonate buffer containing 50 microM ethylisopropylamiloride to block Na+/H+ exchange. Despite similar nadir pH(i) (lowest pH(i) values due to acid load), the subsequent pH(i) recovery rate that reflects Na+-(HCO(3)-)n cotransport activity was increased significantly after hypothermic preservation. Hepatocytes were also perfused with a bicarbonate-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, and Na+/H+ exchange activity was evaluated using the same acid load protocol. Although cells always exhibited similar steady-state initial pH(i) and nadir, the rate of pH(i) recovery decreased significantly as a function of cold storage time in UW solution. Finally, intracellular buffering capacity was calculated from the sudden pH(i) changes induced by HCO(3)(-)-CO(2) steps or NH4Cl pulses and was found to remain stable throughout the 72 h of cold preservation. Therefore, the results strongly suggest that cold preservation and rewarming disturb hepatocellular pH regulatory mechanisms by attenuating Na+/H+ exchange and increasing Na+-(HCO(3)-)n cotransport, whereas Cl-/HCO(3)- exchange is not affected.

Adenosine↗
PubMed1998

Left ventricular dysfunction following rewarming from experimental hypothermia.

This study was aimed at elucidating whether ventricular hypothermia-induced dysfunction persisting after rewarming the unsupported in situ dog heart could be characterized as a systolic, diastolic, or combined disturbance. Core temperature of 8 mongrel dogs was gradually lowered to 25 degreesC and returned to 37 degreesC over a period of 328 min. Systolic function was described by maximum rate of increase in left ventricular (LV) pressure (dP/dtmax), relative segment shortening (SS%), stroke volume (SV), and the load-independent contractility index, preload recruitable stroke work (PRSW). Diastolic function was described by the isovolumic relaxation constant (tau) and the LV wall stiffness constant (Kp). Compared with prehypothermic control, a significant decrease in LV functional variables was measured at 25 degreesC: dP/dtmax 2,180 +/- 158 vs. 760 +/- 78 mmHg/s, SS% 20.1 +/- 1.2 vs. 13.3 +/- 1.0%, SV 11.7 +/- 0.7 vs. 8.5 +/- 0.7 ml, PRSW 90.5 +/- 7.7 vs. 29.1 +/- 5.9 J/m. 10(-2), Kp 0.78 +/- 0.10 vs. 0.28 +/- 0.03 mm-1, and tau 78.5 +/- 3.7 vs. 25.8 +/- 1.6 ms. After rewarming, the significant depression of LV systolic variables observed at 25 degreesC persisted: dP/dtmax 1,241 +/- 108 mmHg/s, SS% 10.2 +/- 0.8 J, SV 7.3 +/- 0.4 ml, and PRSW 52.1 +/- 3.6 m. 10(-2), whereas the diastolic values of Kp and tau returned to control. Thus hypothermia induced a significant depression of both systolic and diastolic LV variables. After rewarming, diastolic LV function was restored, in contrast to the persistently depressed LV systolic function. These observations indicate that cooling induces more long-lasting effects on the excitation-contraction coupling and the actin-myosin interaction than on sarcoplasmic reticulum Ca2+ trapping dysfunction or interstitial fluid content, making posthypothermic LV dysfunction a systolic perturbation.

Animals↗
PubMed1983

Morphine and postoperative rewarming in critically ill patients.

Morphine sulfate (MSO4) has been demonstrated to attenuate the stress response. MSO4 might be useful in minimizing the stress associated with the perioperative period, particularly that due to awakening from anesthesia and rewarming. Two groups of critically ill patients who developed hypothermia (35.8 degrees C) during a surgical procedure were studied. The control group was observed during routine medical management. Group II received 1 or 4 mg/kg MSO4 followed by an infusion of 0.2 or 0.5 mg/kg/hr. During the postoperative rewarming period the control group patients demonstrated a major increase in metabolic demand and myocardial work. In group II patients the infusion of MSO4 resulted in a lower metabolic rate. This was associated with a significantly longer rewarming time and a significant reduction in shivering, heat loss, heart rate, mean arterial pressure, and rate-pressure product. Infusion of MSO4 in critically ill patients during the perioperative period suppressed metabolic demands and myocardial work while preserving cardiovascular function.

Aged↗
PubMed1992

Airway cooling and rewarming. The second reaction sequence in exercise-induced asthma.

To determine if a relationship exists among the magnitude and rate of airway rewarming, and the severity of bronchial obstruction in thermally induced asthma, we had seven subjects perform three- to four-point stimulus response curves with isocapnic hyperventilation of frigid air with and without pretreatment with inhaled norepinephrine. The latter was employed to alter the heat supplied to the airway walls by producing vasoconstriction. 1-s forced expiratory volume (FEV1) was measured before and 5 min after the cessation of each bout of hyperpnea and before and after norepinephrine. On a separate day, the subjects repeated the above challenges while the temperatures of the airstream in the intrathoracic airways were measured. Prenorepinephrine, FEV1 progressively decreased in a stimulus response fashion as ventilation rose, while norepinephrine shifted this curve to the right. As the level of ventilation increased, the size of the temperature difference between the cooling of hyperpnea and the rewarming of recovery followed suit, and their magnitude was linearly related to the severity of bronchial narrowing. Reducing the mucosal blood supply of the airways with norepinephrine limited rewarming and attenuated the obstructive response. These data demonstrate that the airway narrowing that develops following hyperpnea and the magnitude of the thermal differences are related, and that alterations in blood supply directly affect bronchial heat flux and influence obstruction.

Adult↗
PubMedDate not supplied

Room temperature ADP-induced first-stage hyperaggregation of human platelets: the cause of rewarming deaths by thrombocytopenia in neonatal cold injury.

No satisfactory explanation has been proposed to explain the rewarming deaths common in neonatal cold injury (NCI). Since thrombocytopenia exists in NCI, aggregation studies were performed on human platelets at the relevant temperatures to search for a mechanism that would link thrombocytopenia with this complication. At the temperatures found in infants suffering from NCI, an increased sensitivity to ADP was noted: room-temperature ADP-induced first-stage hyperaggregation. Evidence exists to suggest that adequate release of ADP from erythrocytes occurs in vivo to cause such aggregation. Hypothermic platelets on being rewarmed undergo a second stage of irreversible aggregation that correlates well with the postwarming drop in platelet count seen in NCI and offers an explanation of the massive pulmonary hemorrhage and other bleeding phenomena seen in infants who die while being rewarmed.

Adenosine Diphosphate↗
PubMed1992

Radiofrequency energy for rewarming of cold extremities.

Radiofrequency (RF) coils, developed to resonate at 27.12 MHz, were evaluated for effectiveness in rewarming thermally unprotected extremities of 5 male subjects. Bare hands or bare feet were exposed to 10.0 degrees C air during a total of four exposures for each subject. Deposition of RF energy for two of the exposures (one for the hands and one for the feet) began when a predetermined surface skin temperature was achieved. Rewarming continued for 10 min while fiber-optic sensors recorded surface skin temperatures at eight locations for each hand and four locations for each foot. Results were compared to data from identical exposures but without RF rewarming. Statistically significant (P less than 0.01) warming occurred at all of the monitored locations. Our results clearly demonstrate the ability of RF energy to warm hands and feet in cold environments.

Adult↗
PubMed1991

Rewarming postoperative patients: lights, blankets, or forced warm air.

This study was designed to determine if the forced warm air system is more effective than warmed cotton blankets or radiant heat lamps for rewarming postoperative patients. PACU admission temperatures were taken on 370 adult patients. The study population of 90 patients with admission temperatures of 35 degrees C (95 degrees F) or less was randomly assigned to one of three intervention groups: (b) warmed cotton blankets, (L) radiant heat lamps, or (A) forced warm air. Oral or axillary temperatures were monitored every 15 minutes and the warming intervention continued until the patient reached the discharge criteria of 36 degrees C (96.8 degrees F). The three groups were comparable for sex, age, admitting temperature, OR time, and OR fluid. The mean rewarming times for patients who shivered were similar for all groups. For those patients who did not shiver, those treated with forced warm air rewarmed significantly faster than patients in the other groups. Nonshivering patients treated with forced warm air were ready for discharge somewhat sooner than those treated with either of the other two interventions.

Body Temperature Regulation↗
PubMed1990

Evaluation of the patient having cardiac surgery in the postoperative rewarming period.

Ensuring adequate oxygen delivery to the tissues with respect to oxygen demand is the treatment goal in patients undergoing coronary artery surgery (CAS). In this study we examined changes in temperature, arterial oxygen saturation (SaO2), cardiac index (CI), oxygen consumption (VO2), and mixed venous oxygen saturation (SvO2) over the initial 4-hour rewarming period in 36 patients having CAS. When patients were admitted to the intensive care unit the mean temperature was 36.27 degrees C, and it increased to 37.50 degrees C; SaO2 was 97.67% at the beginning and end of the 4-hour period; CI was 2.88 L/min/m2 and rose to 3.00 L/min/m2; VO2 was high at 0.320 L/min on admission and remained high at 0.290 L/min at the end of the 4-hour rewarming period; and SvO2 was 70.83% initially and declined to 66.53% in the same period of time. Continuous SvO2 monitoring was valuable in the ongoing assessment and management of the patients in stable, mildly hypothermic condition after CAS during the 4-hour postoperative rewarming period.

Aged↗
PubMed1988

Reduced temperature afterdrop in rhesus monkeys with radio frequency rewarming.

Rhesus monkeys were anesthetized and rendered hypothermic by icewater immersion. Rewarming by radio frequency (RF) energy at 13.56 MHz or by a surgical heating pad was initiated either immediately after removal from the icewater or after a delay of 20-26 min. Rectal temperature (Tre) was monitored during each experiment, and RF energy, initially applied at a specific absorption rate (SAR) of 10 W.kg-1, was able to raise Tre an average of 3 degrees C in 20 min. For an equivalent period of rewarming with the heating pad, Tre had not yet recovered from the immersion-induced afterdrop. It is concluded that RF rewarming offers a special advantage when applied to the treatment of immersion hypothermia.

Animals↗
PubMed1988

The use of extracorporeal rewarming in a child submerged for 66 minutes.

A 2 1/2-year-old girl had a good neurologic recovery after submersion in cold water for at least 66 minutes; as far as we know, this is the longest time ever reported. Cardiopulmonary resuscitation was maintained for more than two hours before the initiation of extracorporeal rewarming in this child who had a core temperature of 19 degrees C. To our knowledge, this is the first successful use of extracorporeal rewarming in a child suffering from accidental hypothermia. Extension of this technique to children offers rapid rewarming and cardiovascular support for pediatric victims of severe hypothermia. We emphasize the importance of a coordinated response by the entire emergency medical system integrated with hospital-based personnel. Where it is geographically feasible, regionalization of triage and care for the pediatric victim of severe accidental hypothermia should be considered.

Child, Preschool↗
PubMed1979

Pulsatile perfusion versus conventional high-flow nonpulsatile perfusion for rapid core cooling and rewarming of infants for circulatory arrest in cardiac operation.

Thirty consecutive infants undergoing hypothermia and circulatory arrest for repair of ventricular septal defect, transposition of the great vessels, or atrioventricular canal defects were alternately selected for conventional high flow nonpulsatile perfusion or pulsatile perfusion during core cooling and rewarming. All received morphine anesthesia, 30 mg/kg of Solu-Medrol, and 10 to 15 mcg/kg of phentolamine. Those receiving nonpulsatile flow were perfused at a rate of 160 to 180 cc/kg/min with a roller pump and oxygenator with arterial pressure of 50 to 55 mm Hg. In the pulsatile flow group, a roller pump and oxygenator were used, and an especially constructed Datascope PAD (pulsatile assist device) was interposed in the arterial line to provide pulsatile perfusion with 75/40 mm Hg pressure at slightly reduced flow (150 cc/kg/min). The average rectal, esophageal, and tympanic membrane temperatures were reduced to approximately 16 degrees C prior to circulatory arrest. Following repair, perfusion was resumed until these temperatures returned to 37 degrees C. Cooling and rewarming were enhanced by pulsatile perfusion, with over 30% reduction in total pump time. Additionally, the larger patients in the pulsatile group cooled almost as rapidly as the smaller. The rates of decline and subsequent rise of rectal, esophageal, and tympanic membrane temperatures were equal in the pulsatile group, but the rectal temperature lagged far behind in the nonpulsatile group. Urine production during bypass was 100% greater in the pulsatile group. The plasma free hemoglobin was similar in both groups. The average postrewarming pH was 7.31 in the nonpulsatile group and 7.42 in the pulsatile group. Infants receiving pulsatile flow awakened more quickly, were more alert, and required less postoperative mechanical ventilation. We suggest that pulsatile perfusion for core cooling and rewarming of infants is safe and is more rapid and physiological than conventional high-flow nonpulsatile perfusion.

Acid-Base Equilibrium↗
PubMed1983

Serum chemical values in hypothermic and rewarmed young calves.

Serum chemical values were determined in cold-stressed Holstein bull calves ranging from 1 to 7 days of age. The animals were anesthetized and cold-stressed until their core body temperature (colonic) was lowered 10 C. Animals were then rewarmed in warm water, with heat pads or heat lamps, or were allowed to recover naturally (unassisted) at room temperature. Blood samples were collected at selected intervals during cooling and recovery. Increases (P less than 0.05) were observed in the concentrations of glucose, calcium, phosphorus, iron, alkaline phosphatase, aspartate aminotransferase, lactate dehydrogenase, total protein, albumin, total globulin, serum urea nitrogen, uric acid, total bilirubin, indirect bilirubin, and cholesterol in the cold-stressed calves during cooling. Concentrations of chloride and insulin decreased (P less than 0.05) during the same period. Changes observed in many of the serum chemical values during rewarming were generally the reverse of the respective changes that occurred during cooling, although insulin values became exceedingly high in some cases midway or near the end of recovery. Serum enzyme values also remained high during most of recovery. Data did not indicate a clear advantage of one method of rewarming over the other methods used in terms of return of the serum chemical values to normal.

Animals↗
PubMed1984

Comparison of rewarming by radio wave regional hyperthermia and warm humidified inhalation.

Anesthetized random source dogs were cooled by ice water immersion to a stable core temperature of 25 degrees C and subsequently rewarmed with warm humidified inhalation (43 degrees C, 450 cc of min ventilation X kg-1) or radio-frequency induction hyperthermia (4-6 watts X kg-1). The mean time required for core rewarming to 30 degrees C was 280 +/- 114 min for ventilation and 58 +/- 13 min for radio wave therapy (p less than 0.001). There was no evidence of tissue damage with either modality. These data suggest radio wave heating is superior to warm humidified inhalation therapy for core rewarming of rapidly induced immersion hypothermia.

Animals↗
PubMed1983

Hematologic values in hypothermic and rewarmed young calves.

Hematologic values were determined in cold-stressed and rewarmed 1- to 7-day-old Holstein bull calves. The animals were anesthetized and then cold-stressed by immersion in water until their core body temperature (colonic) had decreased by 10 C. They were kept at the hypothermic state for an additional 1 hour and then were rewarmed by 1 of 3 external rewarming methods or by natural (unassisted) recovery. Changes observed in the hematologic values of the cold-stressed calves during cooling represented a trend, rather than a direct effect of cold exposure because the values did not differ (P greater than 0.05) from those obtained from the noncold-stressed animals. Nevertheless, a linear decrease (P less than 0.05) in the total number of leukocytes was observed in the cold-stressed calves during cooling when compared with preimmersion values. The leukopenia resulted primarily from a neutropenia (P less than 0.05) and secondarily from decreases in the number of other leukocytes. Minor increases were noticed in the total number of erythrocytes, hemoglobin concentration, and PCV, whereas mean corpuscular values generally remained unchanged during cooling. A rapid and linear increase in the total number of leukocytes was noticed in all cold-stressed calves during recovery. The increase in total leukocytes occurred in all types of leukocytes and particularly in segmented and nonsegmented neutrophils.

Animals↗
PubMed1979

Use of athrombogenic tubing for perfusion rewarming following surface-induced deep hypothermia.

A method of heparinless, oxygenatorless, left heart bypass perfusion rewarming following surface hypothermia, with the use of a closed circuit with 130 ml. prime volume including heat exchanger, has been devised. The use of polyurethane-polyvinyl-graphite (PPG)-coated tubing has previously been reported. In this text, the use of an athrombogenic coating with cetyl-pyridinium chloride (CPC) as a regional heparin carrier was studied in dogs, comparing groups with PPG tubing and total systemic heparinization or plain polyvinyl tubing without systemic heparinization. Heparin compounded in the CPC coating eluted into the blood and caused mild transient whole-body heparinization during rewarming from 20 degrees to 25 degrees C., as evidenced by prolongation of the thrombin time. Alterations of hematologic parameters in all three groups were similar to those during surface rewarming except for those affected by heparinization. The left heart bypass method was found useful for hypothermic open-heart surgery when utilized with an athrombogenic surface coating or total body heparinization. It was concluded that the CPC coating is superior to the PPG coating since no cracking surface develops, it is translucent, and it provides a more effective athrombogenic surface.

Animals↗
PubMed1993

Hypothermia and rewarming after cardiac surgery.

Ensuring adequate oxygen delivery to the tissues with respect to oxygen demand is an important operative challenge during cardiac surgery. The state of the art in myocardial preservation in the 1990s has evolved to include pretreatment of the myocardium; intraoperative use of systemic hypothermia with cardiopulmonary bypass (CPB), topical cooling of the myocardium, cold cardioplegia, and myocardial reperfusion; and postoperative oxygen transport support. These techniques optimize myocardial preservation while providing adequate cardiac surgery operative times by decreasing the myocardial ischemic period, decreasing cellular metabolic requirements, and preserving energy stores. Awareness of the physiologic consequences of hypothermia in the postoperative cardiac patient improves nursing assessment of the hypothermic patient. Appropriate temperature monitoring and reporting support timely medical and nursing interventions for hypothermia, such as internal and external rewarming techniques or drug administration to facilitate the rewarming process and suppress or treat shivering. This article addresses the physiologic condition of hypothermia, the elective hypothermia techniques used during cardiac surgery, and the medical or nursing rewarming and management techniques for the postoperative cardiac surgery patient.

Aged↗
PubMed1977

Accidental hypothermia: an experimental study of practical rewarming methods.

Five rewarming techniques, appropriate for first-aid use in the nonhospital setting, were applied to each of nine subjects whose body temperatures had been lowered to 35 degrees C in a stirred tank of 7.5 degrees C water. The rewarming techniques were: a) inhalation of heated, water-saturated oxygen; b) placement of heating pads over areas of high heat transfer; c) combination of methods a) and b); d) hot whirlpool bath; and e) shivering. Inhalation of heated, water-saturated oxygen was significantly better than the shivering control in minimizing temperature "afterdrop" and is, therefore, preferred over the other techniques as it avoids the physiological hazards of the peripheral vasodilation from external rewarming.

Adult↗
PubMed1996

[Severe, accidental hypothermia: active rewarming with a simple extracorporeal veno-venous warming-circuit].

We report the case of a 35-year-old male who was admitted to the intensive care unit because of somnolence due to accidental hypothermia. Initial examination showed a Glasgow coma score of 10 and a rectal temperature of 27.4 degrees C. Because of stable circulatory conditions, there was no mandatory indication for rewarming by means of cardiopulmonary bypass. We rewarmed the patient with an extracorporeal veno-venous haemofiltration device combined with a countercurrent fluid warmer. An average increase in body temperature of 1.34 degrees Ch-1 could be obtained. We conclude that the described technique represents an effective and well-controllable method for treatment of hypothermia in patients with stable haemodynamic conditions. Because of the availability of the required equipment, this method can also be practised in hospitals without cardiac surgical departments and cardiopulmonary bypass facilities.

Adult↗