Hypothermia as a therapeutic tool

Despite hypothermia or loss of normal temperature is a detrimental to human in most cases, medically controlled hypothermia has been used as a life-saving therapeutic tool in many cases. Therapeutic hypothermia have been tried for decades in the field of cardiac surgery, cardiac arrest, acute traumatic brain and spinal injuries, ischemic stroke, perinatal hypoxic encephalopathy, intracranial hypertension, acute liver failure, malignant hyperthermia, heat stroke and etc. Recently therapeutic hypothermia is mostly aimed to protect acute brain or nerve injury from various types of insults in which pharmacologic therapy is hard to achieve a successful result. Conventional cooling methods such as cold water immersion, gastric or bladder lavage with cold saline are used for decades but these methods have the limitation of fine temperature control and higher adverse effects. With the advance of cooling devices, therapeutic hypothermia can be performed in a more sophisticated manner. Currently used cooling methods include surface cooling and core cooling depending on the primary place of heat exchange. Surface cooling method uses cold water solution or air to reduce body temperature by transferring the heat from human body surface. Core cooling or intravascular cooling devices are placed in the large vascular system to cool down the blood circulation and then the whole body from inside. The mechanism of therapeutic hypothermia is not elucidated clearly so far. But many experimental studies and some clinical studies demonstrate that hypothermia reduces oxygen needs and metabolic demands by slowing down the general metabolism, inhibits excitotoxicity, modulates inflammatory reactions, reduces free radical production, inhibits apoptosis or cell death, and preserves the intactness of blood brain barrier which prevents from brain edema formation and so on. These hypothermic effects are derived from the interference of signal transduction, gene regulation and protein structure/function regulation directly or indirectly by hypothermia. Even though therapeutic hypothermia is one of the robust therapies against acute brain injury, its adverse effects put restriction in using hypothermia as a common therapeutic tool. Hypothermia produces reduced immunity and increased infection, blood coagulation abnormality, cardiac abnormalities, metabolic disturbances and so on. Most of the adverse effects are observed in system cooling since lowered temperature of the body is not physiological and even detrimental as we can observe in hypothermic accidents. Therefore the development of better cooling methods which can reduce the adverse effects but maintain the beneficial aspects is needed.