Dear Professor Tierney,
I enjoyed reading the article by Thompson and Kagan (2011). The difficulty their respondents had in describing the difference between hyperthermia and fever is in my experience (neuro and general intensive care) true in the UK also. Therefore, it might be helpful to clarify that fever is a regulated rise in temperature, whereas hyperthermia is a rise in temperature above the range specified as normal for a species (Commission for Thermal Physiology of the International Union of Physiological Sciences 2001). Hyperthermia may be regulated, as in fever, or forced, when heat production exceeds heat loss, for example, in heat stroke.
Thompson and Kagan cite the most recent edition of the Brain Trauma Foundation Guidelines (BTF/AANS 2007) in support of fever avoidance and maintenance of normothermia in patients with traumatic brain injury. While these guidelines do have chapters on therapeutic hypothermia (not recommended as standard care) and infection prophylaxis, they do not include any guidance on fever thresholds and management of increased temperature. The only mention of increased temperature is a comment, with regard to sedatives and analgesics, that
It is felt beneficial to minimize painful or noxious stimuli as well as agitation as they may potentially contribute to … body temperature elevations … (BTA/AANS 2007; S-71).
In the previous edition of the guidelines ‘control of body temperature’ (BTF 2000, p. 139) is recommended as one of the interventions for established intracranial hypertension and infection is noted as a secondary insult (BTF 2000, p. 55), but again fever thresholds and temperature management are not discussed.
This could be interpreted as supporting the view that fever after traumatic brain injury is so unarguably detrimental that treating it should be taken as read! Indeed there are many published articles which take this stance. However, a more nuanced view is probably warranted (Childs et al. 2010) because the evidence for treating raised temperature is limited and associational. There is one systematic review of the impact of fever on outcome which includes traumatic brain injury among a very heterogeneous neurological population (Greer et al. 2008). Four of the eight studies in adults with traumatic brain injury showed no significant relationship between raised temperature and outcome. There is as yet no good evidence that controlling temperature to normothermia (or thereabouts) improves outcome in this patient group (Saxena et al. 2008).