Defeating Normal Thermoregulatory Defenses

Abstract

Abstract-Therapeutic hypothermia may be useful in various circumstances including stroke. However, core body temperature is normally tightly regulated. Even mild hypothermia in conscious subjects thus provokes vigorous thermoregulatory defenses which are potentially harmful in fragile patients. Furthermore, thermoregulatory responses are effective, which reduces the rate at which hypothermia can be induced. Drugs are thus often given to blunt normal thermoregulatory defenses. General anesthetics profoundly impair thermoregulatory control, but prolonged general anesthesia is rarely practical or appropriate. A variety of other drugs have therefore been evaluated. Most opioids only slightly impair thermoregulatory defenses, but meperidine is considerably more effective than equipotent doses of other opioids. The central ␣-2 agonists clonidine and dexmedetomidine are also useful. However, the best overall approach to inducing thermal tolerance appears to be a combination of buspirone and meperidine, which reduces the core temperature triggering shivering to about 33.5°C in doses that maintain adequate ventilation. (Stroke. 2009;40:e614-e621.)

Induction of therapeutic hypothermia by pharmacological modulation of temperature-sensitive TRP channels: theoretical framework and practical considerations

“…A broad suppression of the central nervous system is a natural consequence of a comatose state, which is a typical occurrence in patients resuscitated after out-of-hospital cardiac arrest. 52 Further inactivation of the thermoregulatory system may be achieved by general anesthetic drugs, such as midazolam and fentanyl. 10,11 Thus, patients in coma and under general anesthesia are very prone to reduction in core temperature and much of the successful experience with therapeutic hypothermia has been obtained in such patients by exposing them to the physical cooling methods discussed above.…”

Shivering management during therapeutic hypothermia in patients with traumatic brain injury: protocol from the Eurotherm3235 trial

“…Effective hypothermia in critical care requires a strategy to prevent and manage shivering. Core body temperature in mammals is highly regulated [ 1 ]. Hypothermia leads to the activation of measures to counteract this, reducing heat loss through vasoconstriction and increasing heat generation through increased metabolism and shivering.…”

Experimental and Clinical Use of Therapeutic Hypothermia for Ischemic Stroke: Opportunities and Limitations

“…Selectively cooling the brain, for example with an extracranial cooling coil, is becoming more popular in experimental rat models [63]. In the clinical situation, however, surface cooling combined with endovascular cooling is commonly used [26, 27, 37, 38, 64, 65]. …”