Therapeutic hypothermia applicable to cardiac surgery

Ischaemia and reperfusion injury: when cells almost die

“…The report went on to state that "for most cardiac surgical procedures, mild to modest (32-36 °C) hypothermia will be sufficient to assure neuroprotection." 23 While still in its infancy in veterinary medicine, therapeutic hypothermia is used widely in human surgical cases as well as in the emergency room.…”

A Comprehensive Update of Current Anesthesia Perspectives on Therapeutic Hypothermia

“…TH works to maintain and preserve the integrity and survival of these neurons by reducing extracellular levels of excitatory neurotransmitters, e.g., dopamine and glutamate, thereby reducing central nervous system hyperexcitability. The release of both is temperature dependent with lower temperatures inhibiting their release [18, 20]. Glycine is required for NMDA receptors to be activated, so an increase in glycine accelerates the function of NMDA receptors.…”

“…Hypothermia also protects organs from ischemic injury by reducing cerebral blow flow, the metabolic rate, and oxygen and glucose consumption. The decrease in cerebral metabolic demands results in slower enzyme activity allowing for ATP stores to be preserved [20]. Normally when ischemic injury occurs, cells can partially or fully recover, become necrotic, or can enter into a programmed cell death called apoptosis.…”

“…Studies in the past have shown that TH is able to interrupt apoptosis as early as initiation. TH exerts its effects on apoptosis by inhibiting caspase activity, increasing anti-apoptotic Bcl-2 expression, and preventing mitochondrial dysfunction [18–20]. Another mechanism by which TH provides neuroprotection is through the reduction of free radical formation that follows ischemia [18–20].…”

“…With less free radicals and the presence of antioxidants, the body is able to mitigate the oxidative damage that free radicals induce, allowing more cells to repair and recover [19]. It has been shown that TH may interfere with the activity of superoxide dismutase, leading to less hydrogen peroxide and fewer hydroxyl radicals [20]. The last proposed mechanism that TH works by is preserving collagen integrity by decreasing interstitial collagen fragmentation, increasing protein survival, and promoting signals to allow for cell survival.…”