Adrenergic, respiratory, and cardiovascular effects of core cooling in humans

Abstract

The adrenergic, respiratory, and cardiovascular responses to isolated core cooling were assessed in awake human subjects. Mild core hypothermia was induced by intravenous infusion of 30 or 40 ml/kg of cold saline (4 degrees C) on 2 separate days. A warm intravenous infusion (30 ml/kg, 37 degrees C) was given on a third day as a control treatment. Mean norepinephrine concentration increased 400% and total body oxygen consumption increased 30% when core temperature decreased 0.7 degrees C. Mean norepinephrine concentration increased 700% and total body oxygen consumption increased 112% when core temperature decreased 1.3 degrees C. Core cooling was associated with peripheral vasoconstriction and increased mean arterial blood pressure, whereas heart rate was unchanged. Plasma epinephrine and cortisol concentrations were unchanged during core cooling. There were no changes in any measured parameter with the warm infusion. These findings suggest that mild hypothermia induced by isolated core cooling is associated with an adrenergic response characterized by peripheral sympathetic nervous system activation without a significant adrenocortical or adrenomedullary response. The respiratory and cardiovascular responses to core cooling are characterized by a shivering-induced increase in metabolic rate, norepinephrine-mediated peripheral vasoconstriction, and increased arterial blood pressure.

Effects of environmental hypothermia on hemodynamics and oxygen dynamics in a conscious swine model of hemorrhagic shock

“…It is inferable that environmental hypothermia inevitably causes surface temperature reduction. Although changes in the surface temperature contribute only about 20% to the cold response, [18][19][20] we found animals in group B shivering all the time. Even if O 2 ER had increased to a high level, oxygen equilibrium could not be maintained because shiver increased oxygen demand greatly.…”

Effects of Hypothermia on Energy Metabolism in Mammalian Central Nervous System

“…Hence, anesthetized experimental animals and patients subjected to moderate and deep hypothermia may require fluid replacement and even pharmacological support. By contrast, in conscious mammals such as humans (Frank et al, 1997) peripheral vasoconstriction caused by coldtriggered sympathetic stimulation may lead initially to an increase in blood pressure.…”

“…Values for two are listed in Table 2 whereas the third, who was only very lightly anesthetized, shivered during cooling and his cerebral CMRO 2 did not decrease but increased substantially. This observation indicates that the effects of hypothermia per se can be overridden by other factors that independently activate metabolism, such as sympathetic stimulation (Carlsson et al, 1977;Frank et al, 1997). (4) During selective brain surface cooling (Laptook et al, 2001) and after bicarotid perfusion of the head with extracorporally cooled blood (Walter et al, 2000) CMRO 2 was reported to decrease with a Q 10 very similar to that with whole-body cooling.…”

Comparison of Ondansetron in Two Different Doses in the Reduction of Post Anesthetic Shivering After General Anesthesia

“…7,8,9 Prevention and treatment of Post Anesthetic Shivering (P.A.S) is an important aspect of patient care, as it may be associated with a number of deleterious sequelae, including sympathoadrenal stimulation, increased oxygen consumption, and carbon dioxide production which may lead to increased incidence of surgical wound infection, prolonged hospitalization, morbid cardiac events, increased blood loss and prolonged postoperative recovery. 10,7,11 Various observations suggest that the serotonergic system has a role in the control of post anesthesia shivering. It has been shown that a 5-Hydroxytryptamine-3 (5-HT3) antagonist, Ondansetron has anti-shivering effects.…”