The Cardiovascular Effects of Acutely Induced Hypothermia 12

Prec, O.; Rosenman, R. H.; Braun, Karl; Rodbard, Simon; Katz, Louis N.

doi:10.1172/jci102071

Cited by 84 publications

(27 citation statements)

References 15 publications

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“…Heart rate has been reported to fall linearly with decreasing body temperature in anaesthetized dogs [Brendel et al, 1958;Prec et al, 1949]. There was a decrease in heart rate in our hypothermic sheep but only in relation to the elevated rates reached prior to this during exposure.…”

Section: Discussionmentioning

confidence: 43%

Cardiovascular Parameters in Shorn Sheep Prior to and During Their Exposure to a Cold, Wet Environment

Panaretto¹,

Vickery²

1971

Exp Physiol

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When shorn sheep were exposed to ambient temperatures of 30C and the residual fleece was wetted, heart rate and cardiac output increased substantially above levels measured during a control period at 250C. With continued cold exposure and wetting the sheep become hypothermic and heart rate and cardiac output decreased. In most sheep at rectal temperature <32°C cardiac output had fallen below control values while heart rate remained above control. In a minority of hypothermic sheep cardiac output remained above control rates.Our interest in physiological events that occur during cold-stress in sheep originated from deaths of sheep from this cause after shearing in Australia. Hutchinson [1968] reviewed losses suffered by newly-shorn sheep that are exposed to cold, wet conditions and he concluded that approximately one million sheep died annually from cold exposure.Few data on cardiac output during cold exposure and hypothermia have been collected in conscious animals. The majority of results are confounded by anaesthesia of the subjects [Thauer, 1965] and the rates at which anaesthetized subjects were cooled [Brendel et al., 1958]. Data of other indices of cardiac physiology in cold-stressed sheep are also fragmentary. Hutchinson et al. [1960] reported elevated heart rates in sheep exposed to a cold, windy environment that reduced their rectal temperature (Tre) to approximately 37*4°C. In many other studies on newly-shorn sheep, cold exposure has been transient and measurements of body temperature and heart rate have not been concurrent [Slee, 1966; Slee and Sykes, 1967;Sykes and Slee, 1969].We have, therefore, studied cardiovascular parameters in newly-shorn sheep held at a control temperature of 250C and repeated the measurements when the sheep were exposed to a cold (3°C), wet environment. Endocrinological aspects of these experiments are reported elsewhere [Panaretto and Vickery, 1970]. METHODSThe sheep and their pre-experimental treatment. Six adult Merino ewes and one wether (no. 4) each weighing about 30 kg were used; they were accustomed to the presence of the observers. Each animal was given 400 g daily of a mixture of equal parts of lucerne chaff and oats which was sufficient to maintain body weight during the 4-8 weeks prior to the experiments. The same quantity of feed was given during cold exposure.The sheep were shorn and a femoral arterial catheter (clear vinyl, i.d. 1*5 mm, 101

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Section: Discussionmentioning

confidence: 43%

Cardiovascular Parameters in Shorn Sheep Prior to and During Their Exposure to a Cold, Wet Environment

Panaretto¹,

Vickery²

1971

Exp Physiol

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“…3 Slowing of the heart rate and slowing of the spread of excitation with lengthening of PR, QRS, and QT intervals seen on the ECG were subsequently demonstrated in multiple animal models. [4][5][6][7][8][9][10][11][12]15 One of these studies resulted in the adoption of the eponym ''Osborn'' wave for the characteristic deflection at the end of the QRS complex. 7 In 1943, the first description of the deflection at the end of the QRS was reported in dogs.…”

Section: Discussionmentioning

confidence: 99%

A Prospective Evaluation of the Electrocardiographic Manifestations of Hypothermia

Vassallo

Delaney

Hoffman

et al. 1999

Academic Emergency Medicine

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Abstract. Objective: To determine the effects of body temperature, ethanol use, electrolyte status, and acid-base status on the electrocardiograms (ECGs) of hypothermic patients. Methods: Prospective, two-year, observational study of patients presenting to an urban ED with temperature Յ95ЊF (Յ35ЊC). All patients had at least one ECG obtained. Electrocardiograms were interpreted by a cardiologist blinded to the patient's temperature. J-point elevations known as Osborn waves were defined as present if they were at least 1 mm in height in two consecutive complexes. Results: 100 ECGs were obtained in 43 patients. Presenting temperatures ranged between 74ЊF and 95ЊF (23.3ЊC-35ЊC). Initial rhythms included normal sinus (n = 34), atrial fibrillation (n = 8), and junctional (n = 1). Osborn waves were present in 37 of 43 initial ECGs. Of the six initial ECGs that did not have Osborn waves present, all were obtained in patients whose temperatures were Ն90ЊF (Ն32.2ЊC). For the entire group, the Osborn wave was significantly larger as temperature decreased (p = 0.0001, r = Ϫ0.441). The correlation between temperature and size of the Osborn wave was strongest in six patients with four or more ECGs (range r = Ϫ0.644 to r = Ϫ0.956, p = 0.001). No correlation could be demonstrated between the height of the Osborn waves and the serum electrolytes, including sodium, chloride, potassium, bicarbonate, BUN, creatinine, glucose, anion gap, and blood ethanol levels. Conclusions: The presence and size of the Osborn waves in hypothermic patients appear to be a function of temperature. The magnitude of the Osborn waves is inversely correlated with the temperature. Key words: hypothermia, electrocardiograph; Osborn waves. AC-ADEMIC EMERGENCY MEDICINE 1999; 6:1121-1126 T HE EFFECTS of hypothermia on cardiac conduction were first described in 1892.1 Since then, observations of the physiologic changes that occur with cooling of the heart have been reported in animals 2-14 and in humans undergoing craniotomy for subarachnoid hemorrhage, 15 surgery for cardiac anomalies, [16][17][18][19] and anti-cancer therapy. 20,21The first observation of the changes in the electrocardiogram (ECG) in a patient with unintentional hypothermia was reported in 1938. 22 In the following study, the changes in the ECGs of patients with unintentional hypothermia presenting to a large urban hospital ED are described, and the relationship of these changes to common laboratory parameters are analyzed. A review of the literature focuses on the development of the understanding of the effects of cold on the electrical conduction system of the heart and the resultant physiologic and ECG alterations. METHODSStudy Design. This was a prospective, two-year observational study of hypothermia patients presenting to an urban ED. The study was approved by the institutional review boards of New York University School of Medicine, Bellevue Hospital, and the New York City Health and Hospital Corporation.Study Setting and Population. For the purposes of this study, patients were sele...

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“…Body temperatures were reduced during the following one-to two-hour periods by using cold wet cloths applied to the body and by draft-producing electric fans. (1). Measurements similar to the above were also obtained in a series of three dogs heated by short wave diathermy,5 but unless specified, the results given below refer only to those experiments in which radiant heat was employed.…”

Section: Methodsmentioning

confidence: 91%

“…The decreased venous return is probably an early result of redistribution of blood which may later be accentuated by the markedly reduced blood volume resulting from the fluid loss consequent to heating. Some decrease in cardiac output was noted in the controls due partly to the anesthetic and partly, perhaps, to the spontaneous fall in body temperature of one to two degrees (1).…”

Section: Cardiac Outputmentioning

confidence: 92%

The Circulatory Responses to Hyperthermia Induced by Radiant Heat 1

Prec¹,

Rosenman²,

Braun³

et al. 1949

J. Clin. Invest.

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An elevation of the body temperature evokes many physiological changes, as a direct result of the increased rate of metabolism and the greater demand for oxygen and substrate, and indirectly in warm blooded animals because of the elicitation of thermolytic mechanisms. An understanding of the interrelationships between these factors is of obvious importance in an appreciation of the dynamics of hyperthermia and in the establishment of a rationale for its treatment. Despite many important contributions to this problem, there is a paucity of information concerning the effect of hyperthermia on the cardiac output and the right intracardiac pressures. We have therefore undertaken an analytical study of the circulation in hyperthermia in an effort to assay these adjustments more satisfactorily. Our present experiments have been limited to a study of the changes which occur following exposure to radiant heat since this method of producing hyperthermia seemed to be the simplest, being free from incidental effects produced by pyrogens and by other methods. A few experiments were done with short wave diathermy. METHODHyperthermia was induced in nine dogs. Six dogs, anesthetized with sodium pentobarbital, were exposed to radiant heat from several light bulbs until the body temperatures (about 380 C) gradually increased to 42°C during a two-hour interval. Body temperatures were reduced during the following one-to two-hour periods by using cold wet cloths applied to the body and by draft-producing electric fans. (1). Measurements similar to the above were also obtained in a series of three dogs heated by short wave diathermy,5 but unless specified, the results given below refer only to those experiments in which radiant heat was employed. Similar measurements were made on three control anesthetized dogs kept at room temperature. DISCUSSION OF RESULTS Oxygen consumptionMany studies have demonstrated a close parallel between the rise in body temperature and the increased oxygen consumption (2-4) which accompanies the acceleration of cellular metabolism during fever. In our experiments (Figure 1) an average increase of 57% was observed at a body temperature of 420 C, the greatest increase being 100%o in one instance. During the cooling period oxygen consumption decreased simultaneously with the fall in body temperature and returned to control levels as the temperature of the animal again reached 380 C. In the control series only slight and insignificant changes in oxygen consumption took place.Respiration and content of blood gases The production of hyperthermia was accompanied by an increase in respiratory rate and 5 The Burdick Corporation generously supplied the short wave equipment. 301

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The Cardiovascular Effects of Acutely Induced Hypothermia 12

Cited by 84 publications

References 15 publications

Cardiovascular Parameters in Shorn Sheep Prior to and During Their Exposure to a Cold, Wet Environment

Cardiovascular Parameters in Shorn Sheep Prior to and During Their Exposure to a Cold, Wet Environment

A Prospective Evaluation of the Electrocardiographic Manifestations of Hypothermia

The Circulatory Responses to Hyperthermia Induced by Radiant Heat 1

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