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PubMedDate not supplied

Myocardial rewarming mirrors intraoperative mammary artery graft function.

BACKGROUND: The internal mammary artery (IMA) bypass graft provides a satisfactorily long-lasting blood supply to the myocardium. However, its initial flow capacity can be insufficient with subsequent regional myocardial ischemia. We evaluated a method to assess the IMA graft function intraoperatively. METHODS: Twenty-five patients with three-vessel coronary artery disease underwent coronary artery bypass grafting on cardiopulmonary bypass. The in situ IMA was grafted to the left anterior descending coronary artery (LAD) in combination with two saphenous vein grafts to the left circumflex and right coronary artery. Distal anastomoses were performed during cold intermittent blood cardioplegia. After unclamping of the aorta and of the grafted IMA, the temperature at the cardiac anterior and posterior side was measured during the first 5 minutes of warm reperfusion. RESULTS: A sufficient IMA graft function was expressed by a typical rise in temperature: the cardiac anterior and posterior sides showed a parabolic and exponential course, respectively. The rewarming velocity expressed as the first derivative of temperature over time led to a sharp and early peak for the anterior side, and a smaller and delayed peak for the posterior side. Insufficient IMA graft function could be recognized by an atypical temperature course. CONCLUSIONS: Temperature measurement of the heart during warm reperfusion after hypothermic cardioplegia can help to assess the effectiveness of the IMA-LAD graft function.

Coronary Angiography↗
PubMed2006

Human medullary responses to cooling and rewarming the skin: a functional MRI study.

A fall in skin temperature precipitates a repertoire of thermoregulatory responses that reduce the likelihood of a decrease in core temperature. Studies in animals suggest that medullary raphé neurons are essential for cold-defense, mediating both the cutaneous vasoconstrictor and thermogenic responses to ambient cooling; however, the involvement of raphé neurons in human thermoregulation has not been investigated. This study used functional MRI with an anatomically guided region of interest (ROI) approach to characterize changes in the blood oxygen level-dependent (BOLD) signal within the human medulla of nine normal subjects during non-noxious cooling and rewarming of the skin by a water-perfused body suit. An ROI covering 4.9 +/- 0.3 mm(2) in the ventral midline of the medulla immediately caudal to the pons (the rostral medullary raphé) showed an increase in BOLD signal of 3.9% (P < 0.01) during periods of skin cooling, compared with other times. Overall, that signal showed a strong inverse correlation (R = 0.48, P < 0.001) with skin temperature. A larger ROI covering the internal medullary cross section at the same level (area, 126 +/- 15 mm(2)) showed no significant change in mean BOLD signal with cooling (+0.2%, P > 0.05). These findings demonstrate that human rostral medullary raphé neurons are selectively activated in response to a thermoregulatory challenge and point to the location of thermoregulatory neurons homologous to those of the raphé pallidus nucleus in rodents.

Adult↗
PubMed1990

Hypothermia. Safe and efficient methods of rewarming the patient.

Hypothermia, a relatively common problem in the winter months, can cause significant morbidity. It presents in a variety of situations and affects a wide age range. Diagnosis requires a high index of suspicion, because the symptoms, which are primarily related to the central nervous system, are not distinctive. Appropriate management requires accurate measurement of core body temperature. Treatment is centered on rewarming the patient safely and efficiently while providing other supportive measures. Care should be taken to avoid arrhythmias. Simple precautions greatly reduce the risk of hypothermia.

Aged↗
PubMed1978

Mathematical modeling of rewarming after cold therapy.

Statistical methods are presented for fitting mathematical models to skin temperature data. Three types of regression curves, namely, linear regression (Y = A + BX), second-degree regression (Y = A + BX + CX2), and asymptotic regression (Y = alpha + betapx), are discussed as possible models for the rewarming process following cold therapy. The data for fitting the curves consists of back surface temperature (degrees C) corresponding to various times after cold pack treatment (19 degrees C, administered for 20 minutes) was terminated.

Cryotherapy↗
PubMed1980

The detrimental effects of prolonged hypothermia and rewarming in the dog.

The authors had previously observed a deleterious cerebrovascular effect of prolonged hypothermia in primates and cats. In this study they examined the systemic as well as cerebral hemodynamic and metabolic effects of 24 hours of hypothermia in the dog. With decreases in temperature to 29 C, cardiac output (Q) and whole-body oxygen consumption (VO2) initially decreased 52 and 42 per cent, respectively. Thereafter, despite a stable temperature, both Q and VO2 continued to decrease, and at 24 hours values were 7 and 28 per cent of control, respectively, Cerebral blood flow (CBF) and cerebral oxygen consumption responded similarly. At 24 hours inhomogeneous perfusion of both brain and skeletal muscle was observed. With rewarming, cardiovascular collapse with severe tissue hypoxia and acidosis developed; CBF became grossly inadequate, resulting in depletion of brain energy stores.

Animals↗
PubMed1996

Resuscitation of severe hypothermia by extracorporeal rewarming in a child.

We report a case of accidental severe hypothermia from cold exposure in a 31-month-old girl. The rectal temperature was 14.2 degrees C on presentation, and was accompanied by cardiac arrest. Other ominous laboratory markers for poor prognosis were also present. The child was successfully rewarmed by median sternotomy and full cardiopulmonary bypass. An amputation of one leg was required, but neurologic recovery was full. We emphasize the importance of timely, aggressive management in victims of severe hypothermia because of the tremendous potential for salvage despite catastrophic presentation.

Cardiopulmonary Bypass↗
PubMed1976

A device for surface cooling and rewarming in operations on the "dry" heart in babies and children during moderate, deep and profound hypothermia.

Following a clinical experience of 100 cardiac operation in infants durind deep hypothermia, as low as 15C, the authors have designed a new bath for the procedure which incorporates several improvements over those used previously. The device described allows continuous cooling or rewarming of the patient at any stage of the operation by addition of more cold or hot water as required. It is possible to operate with the patient prone or on the side at any level of hypothermia, and while using heart lung bypass. The construction facilitates the even distribution of the circulating water, and a thermostatic control allows the temperature to be fixed at any level required.

Cardiac Surgical Procedures↗
PubMed1982

Respiratory heat transfer in cold water and during rewarming.

Respiratory heat loss was measured during cold water (5-6 degrees C) excursions to depths of 300 m. Losses were computed with and without respiratory gas heating when wearing a diving helmet in current commercial and Service use. A magnitude of heat loss, sufficient to cause undue stress to the respiratory tract, was observed even with gas heating provided, particularly at maximum depth. If the hyperbaric gas is both heated and humidified to a maximum comfort level then respiratory gains in the order of 40 W are possible at 250 m. This technique of utilizing warm wet gas introduced into the respiratory tract was tested as a rewarming technique following immersion in cold water (4-5 degrees C) to the limit of peripheral endurance.

Body Temperature Regulation↗
PubMed1981

Locally induced digital vasospasm detected by delayed rewarming in Raynaud's phenomenon of occupational origin.

The rewarming time of fingers after hand cooling to 10 degrees during ischaemia was significantly prolonged in all subjects with Raynaud's phenomenon of occupational origin compared with normal reaction and patients with primary Raynaud's phenomenon. The temperature is faster and easier to record than pressure or pulse volume. Population studies are in progress with the described technique.

Adolescent↗
PubMed1975

Hypothermia and rewarming induced by surface and He-O2 inhalate temperature control.

Hypothermia and rewarming were induced by a combination of temperature-controlled surface and inhalate methods in rabbits. To facilitate respiratory heat exchange, inhalate-respiratory tract temperature and humidity gradients and thermal conductivity were increased. In addition, the upper respiratory tract was bypassed by an endotracheal tube. To aid in maintaining satisfactory circulatory dynamics, hypercapnia and hypoxia were induced. The combined surface and inhalate method produced a markedly more effective rate of cooling than surface temperature-controlled method alone. Animals survived core temperatures as low as 20.9 degrees C with no complications. The noninvasive simplicity of this method suggests its potential applicability in many clinical situations.

Animals↗
PubMed1986

Postexertional airway rewarming and thermally induced asthma. New insights into pathophysiology and possible pathogenesis.

To determine if postexercise thermal events play a role in exercise-induced asthma (EIA), nine normal and eight asthmatic subjects on three occasions exercised while they inhaled frigid air. During the recovery period, either cold air, air at room temperature and humidity, or air at body conditions was administered in a random fashion. On a fourth occasion, body-condition air was given during exercise. Pulmonary mechanics were measured before and after each challenge. No changes in mechanics developed when air at body conditions was inhaled during exercise, however, increasing the heat content of the air during recovery produced progressively greater obstruction in both groups. On a separate occasion, seven asthmatics hyperventilated frigid air and either recovered spontaneously or had their ventilation slowly reduced. Controlling ventilation markedly attenuated the obstructive response. These data demonstrate that the severity of EIA is dependent not only on airway cooling but also upon the rapidity and magnitude of airway rewarming postchallenge.

Adult↗
PubMed1975

Erythrocyte 2,3-diphosphoglycerate concentrations in hibernating, hypothermic, and rewarming hamsters (38589).

Hematocrit, hemoglobin and erythrocyte 2,3-DPG concentrations were examined in normothermic control, hibernating, and helium-cold hypothermic hamsters. Hematocrit was not signigicantly different (P greater than 0.05) between groups, but did reflect alterations reported for hemoglobin. Hemoglobin concentration did not change from control values during 12 hr at Tre 7 degrees; however, approximately a 20% decrease occurred in hibernators (48 hrs) and animals hypothermic (24 hr). 2,3-DPG concentrations declined 39.1 and 33.9% from control values in the hibernating and 24 hr hypothermic groups, respectively. No change was observed in animals hypothermic for 12 hr. Both parameters were studied in the aroused animal. Hemoglobin returns to control values immediately after the animals reached a stable Tre approximately equal to 37 degrees. Although 2,3-DPG levels increased during arousal, they were still 10% lower than control values in both metabolically depressed groups. 2,3-DPG remained approximately 10% less than controls in rewarmed hypothermic animals studied 2 hr after reaching stable Tre approximately equal to 37 degrees. The data are discussed in terms of cold depression of erythrocyte glycolysis.

Animals↗
PubMed1985

A new efficient method of topical cooling and rewarming of the myocardium.

Profound myocardial hypothermia (below 17 degrees C, and more often around 12 degrees C) is imperative in myocardial protection while the aorta is cross-clamped. Based on our experience in more than 800 open-heart operations, profound myocardial hypothermia can be achieved by very efficient topical cooling despite mild systemic hypothermia (30 to 33 degrees C) and a small, single dose of crystaloid K + cardioplegia. Very efficient topical cooling is achieved by a high flow (1 to 1(1/2) L/min) of continuously cooled fluid (+ 0.5 to + 2 degrees C). The great temperature-reducing capacity of the cooling system is due to a 10 to 15 meter long metal coil tube that is immersed in an ice-salt cold bath. The water pump placed in the bath makes heat exchange even more efficient. The described method of myocardial protection with stable profound myocardial hypothermia safely prolongs the ischemic time during operation to more than 2 hours. By repositioning the coil into the warm bath (39 to 40 degrees C), the whole system can be used for topical rewarming of the heart.

Journal Article↗
PubMed1985

Rewarming rate of the myocardium during aortic cross-clamp time: variations with different levels of body hypothermia.

Twenty patients underwent elective cardiac valve replacement at 20 degrees C of body hypothermia. Temperatures of the ventricles of both walls were monitored on 12 different sites. Distribution of myocardial temperature ranged between 24.3 and 29.3 degrees C for patients of Group I before cardioplegia delivery and 13.2 degrees C in the septum after cardioplegic infusion. Average temperatures for the anterior and posterior wall were 13.6 C and 15 degrees C in the left ventricle and 14.7 and 15 degrees C in the right ventricle. Myocardial temperatures ranged from 26 to 28.7 degrees C for patients of Group II. After cardioplegic arrest, septal temperatures averaged 14.9 degrees C. The recorded sites of the anterior and posterior left ventricle were 14.1 and 13.1 degrees C. The effects of rewarming on the different myocardial areas occurred according to a logarithmic equation, which is faster in the first 10 minutes. The data suggest that the myocardium can be adequately protected with 25 degrees C hypothermia when the cross-clamp period is shorter than 60 minutes. When longer ischemic periods are expected, myocardial protection is best accomplished with 20 degrees C hypothermia.

Journal Article↗
PubMed1992

Effects of two types of head coverings in the rewarming of patients after coronary artery bypass graft surgery.

In this experimental study we examined the effects of two types of head coverings in the rewarming of patients who have had coronary artery bypass graft surgery during the initial 8-hour postoperative period. A third group with no head coverings served as a control. Eighty-one patients were randomly assigned to one of the three treatment groups; rectal temperatures were recorded on admission and hourly for the next 8 hours. An analysis of variance between the three groups revealed no statistically significant differences (p less than 0.05) in the length of time for patients to reach normothermia and in the net temperature gain achieved. Irrespective of the groupings, however, patients who took 5 hours or less to reach normothermia exhibited statistically significant differences (p less than 0.05) compared with patients who took longer: the former patients tended to be younger, the lowest induced operating room temperature tended to be higher, their admission temperatures tended to be higher, and minutes of cardiopulmonary bypass tended to be fewer.

Analysis of Variance↗
PubMed1990

Rewarming after cardiopulmonary bypass--a comparison of two methods.

Patients returning to the Intensive Care Unit following cardiac surgery with cardiopulmonary bypass are almost always hypothermic despite having been rewarmed prior to termination of bypass. The study compared the effect of an overhead radiant heat source with a reflective metallised blanket. Both groups received warmed humidified gases. Rectal, tympanic membrane and great toe temperatures were measured. Patients nursed under the radiant heat source had higher temperatures at the end of the study period as compared to those nursed with conventional means (p less than 0.05).

Aged↗
PubMed1989

[Accidental drowning with extreme hypothermia--rewarming with extracorporeal circulation].

A 3 1/2 year old boy had fallen into a fishpond. After about one hour the boy was brought to our hospital. He was cyanotic and bloated, the rectal temperature was 18.4 degrees C. There was no heart beat, the pupils were wide without reaction to light. Via a sternotomy the heart lung machine was connected and core rewarming was achieved. After 7 days of artificial respiration the boy could be extubated, after 16 days the boy left our hospital without neurological consequences.

Acid-Base Equilibrium↗
PubMed1984

The effect of chilling, freezing, and rewarming on the postmortem chemistry of vitreous humor.

The effect of chilling at the time of death on the postmortem chemistry of the vitreous humor was studied by using sheep heads obtained immediately following decapitation. One group of heads was kept at room temperature, while the remainder were chilled on ice or in ice water, then refrigerated or frozen. Vitreous humor specimens were taken at intervals over a 48-h period. Chilling inhibited the fall in the glucose concentration and the total carbon dioxide content and lessened the increase in lactic acid, compared to the room temperature group. Rapid glycolysis resumed when the heads rewarmed to room temperature starting at 6-h postmortem, but did not resume at later points. The rate of rise of the potassium and magnesium concentrations was also diminished in the chilled eyes. Freezing and thawing caused an abrupt increase in the potassium and magnesium levels, but other solutes were unaffected.

Animals↗