Pediatric Therapeutic Hypothermia After Cardiac Arrest
Therapeutic hypothermia is the deliberate lowering of the body's temperature, intended to reduce the body's need for oxygen. It is particularly designed to preserve the brain in cases of ischemia -- a restriction of blood flow usually caused by cardiac arrest, ischemic stroke, or generalized brain trauma. And there are numerous other applications of this medical practice.
Pediatric therapeutic hypothermia after cardiac arrest is a little documented practice. Given the intended use of therapeutic hypothermia in general it's an interesting theory to work with. The lack of documentation is probably more a reflection of the rare instances where it was used than anything else.
Therapeutic hypothermia has been used since ancient times. Hippocrates advocated the packing of wounded soldiers in snow and ice. A Napoleonic surgeon, Baron Dominque Larrey, noted that wounded officers, who were kept closer to the camp fire, fared less well than enlisted men who were not so pampered.
In the 1950s, deep hypothermia (defined as body temperature of 20 to 25 degrees Celsius) was used to create a bloodless surgical field in cases of intracerebal aneurysm. However, a host of side effects attending such an extreme drop in body temperature caused deep therapeutic hypothermia to decline.
Mild hypothermia, defined as body temperature between 32 and 34 Celsius, was sporadically investigated as a neuroprotectant beginning in the 1950s. Responding to this research, in 2003 the American Heart Association (AHA) and the International Liaison Committee on Resuscitation (ILCOR) endorsed the use of therapeutic hypothermia following cardiac arrest. Currently, a growing percentage of hospitals include mild hypothermia as part of their standard treatment following cardiac arrest and resuscitation.
One study published by the New England Journal of Medicine focused on people who were resuscitated within 5 to 15 minutes following cardiac arrest. Some patients were then cooled for 24 hours with a target temperature of 32-34 degrees Celsius. Fifty-five percent of the cooled patients experienced favorable outcomes, versus only 39 percent for the uncooled group. Death rates in the hypothermia group were 14 percent lower, meaning that for every 7 patients treated one life was saved.
Pediatric use of therapeutic hypothermia is relatively uncharted water. In the 1970s therapeutic hypothermia was used to reduce secondary brain injury in children with severe anoxic/ischemic insults. The practice was abandoned in the 1980s after a retrospective study of near-drowning victims reported that children treated with hypothermia were at an increased risk for death, neutropenia, and sepsis compared with children treated without hypothermia. However, this study had several limitations, including sample size and selection, that render its results suspect. Currently, doctors are advised to use therapeutic hypothermia on children based on their assessments of risks and potential benefits.
There is little evidence that therapeutic hypothermia benefits children who experience cardiac arrest. However, this statement should not be interpreted to mean that therapeutic hypothermia is ineffective in pediatric cardiac arrest cases. The lack of evidence may be due to the extreme rarity of pediatric cardiac arrest cases in which therapeutic hypothermia is applied. It is reasonable to tentatively conclude that because therapeutic hypothermia produces more favorable outcomes in adults, it should have similar favorable effects in pediatric cardiac arrest cases.
