A B Figure. A (adapted from 11 ), Temperature management with set target of 32°C. For the induction phase, the aim is to get temperature to <34°C and down to the target temperature as quickly as possible. A small overshoot (≤1°C) should be regarded as acceptable provided temperature remains >30°C. For the maintenance phase, the target is tight control of core temperature, with minimal fluctuations (ideally never >0.3°C). The rewarming phase should be slow and controlled (warming rate 0.2°C-0.25°C/h). B, Temperature management with set target of 36°C. For the induction phase, the aim is to get the temperature to 36.0°C as quickly as possible. For the maintenance phase, the target is tight control of core temperature, with minimal fluctuations (ideally never >0.2°C-0.3°C). More shivering is likely, because the target temperature is closer to normal, leading to an enhanced shivering response. There is greater risk of slipping into a supranormal (febrile) temperature range, especially because brain temperature exceeds core temperature by 1.0°C to 2.0°C at this temperature. temp indicates temperature; and TTM, therapeutic temperature management. (attributable to decreased consciousness and diminished protective reflexes), brain injury can directly induce immune dysfunction (mediated through the vagal nerve, with efferent signals inhibiting proinflammatory cytokine production), leading to an immunocompromised state with increased susceptibility to infections. 14 Therefore, patients with acute brain injury may have central fever, infectious fever, or a combination of both, either simultaneously or sequentially. Whatever the cause, the result is that the temperature set point is elevated, triggering the body's mechanisms to increase core temperature, and that the patient develops fever.The effectiveness of heat conservation and heat generation decreases with age; this is attributable to a less effective vascular response (ie, less vasoconstriction), decreased ability to detect small temperature changes (leading to a slower counterregulatory response), and a lower basal metabolic rate.11 This means that, in general, fever control and the induction of hypothermia are easier to achieve and maintain in older patients than in younger ones. In addition, the doses of opiates and sedatives required to effectively suppress the body's warming mechanisms are usually much higher in younger patients. Another important parameter affecting ease and speed of cooling is body mass; obese patients are more difficult to cool, especially with surface cooling, because of the insulating properties of adipose tissue and the greater mass that needs to be cooled.Finally, an issue that often confounds studies dealing with (efficacy of) temperature management is that severe brain injury can significantly diminish or even obviate the thermoregulatory response; it is therefore much easier to cool patients with very severe brain injury (and absent shivering response) than those with less severe injury. Thus, easy temperature control is, paradoxically...