Therapeutic efforts to minimize brain injury after a stroke seek to use a multi-pronged approach aimed at controlling blood clots while preserving brain tissue. So far, most of the effective stroke treatments have focused on restoring cerebral blood flow. Neuroprotection remains a challenge.
Hypothermia for cerebral hypoxic damage
Over 100 years ago, it was first observed that stroke induced alterations in metabolic activity in the brain contribute to cerebral damage, and thus exacerbate long-term disability. Warmer body temperature increases metabolic activity, while cooler body temperatures decrease metabolic activity. Therefore, the idea that warmer body temperatures could intensify the cerebral damage of a stroke or that cooler body temperature could reduce or stabilize cerebral damage makes sense in theory.1
A number of animal studies have looked at the effects of hypothermia on cerebral hypoxic damage. For example, a research study using mice2 has demonstrated protection against stroke-induced damage by inducing controlled episodes of hypothermia. When the mice were intermittently cooled down for at least 1.5 hours per session, there were measurable improvements in neurological function. Similarly, continuous hypothermia lasting for 12 hours was found to be neuroprotective, while continuous hypothermia lasting for only 6 hours was not found to have a sufficient protective effect.
Hypothermia in humans
Several challenges to the practical use of hypothermia have prevented it from becoming an established stroke treatment over the years. Body temperature ranges between 34 degrees C and 35 degrees C are considered to be hypothermic, but studies still need to identify which target temperatures are most efficient in preventing brain damage from hypoxia. The optimal timing and duration of effective hypothermia administration as well as the best methods for cooling down patients without causing damage to the brain or other organs are not clearly established.
A recent meta-analysis using 9 studies showed that therapeutic hypothermia significantly reduced delayed cerebral ischemia compared with controls.3 However, it did not did not significantly reduce mortality or serious complications such as re bleeding, pneumonia, sepsis, arrhythmia, or hydrocephalus.
Therapeutic hypothermia: Future directions
The use of controlled temperature regulation may hold potential as a complementary method of treating stroke, along with blood thinners, fluid management, electrolyte regulation, blood pressure maintenance, and prevention of infection. Despite the long-standing interest in hypothermia, however, the application of this approach has not turned out to be practical in preventing damage from cerebral ischemia.