There is an overwhelming amount of literature out there regarding therapeutic hypothermia and the benefits that it offers to patients, post-cardiac arrest. Below you will find the links to many of these articles, and a simple Google search will give you more information than you could ever need. Here is a VERY basic explanation of why we do it.
As previously discussed, cardiac arrest precludes very fragile heart muscles and brain cells from getting the blood supply that they need to survive. This injury is concentrated primarily on the mitochondria – the powerhouse of the cells – and when the damage gets to a certain point, the membranes around the mitochondria rupture and spill their contents into the cells. While bad, at this point the damage is still reversible if oxygen is re-supplied to the cells. The catch is if circulation returns and freshly oxygenated blood is brought to these cells, oxygen reacts with the spilled mitochondrial contents to form oxygen radicals, evil oxygen particles which wreak havoc on the other structures of the cells.
Then there is the second assault. During cardiac arrest, the tissues that aren’t getting oxygen are doing the best they can to perform their roles through other processes called anaerobic metabolism, but these processes produce some very nasty by-products on their own. When blood flow returns, these agents are brought from the peripheral circulation back to the heart and brain cells already damaged by oxygen radicals. It is because of these cellular processes that patients who experience cardiac arrest and then return of spontaneous circulation have historically had very poor survival rates, or even if these patients had survived, their neurologic outcomes were very poor.
This is where therapeutic hypothermia comes into the picture. First introduced way back in the 1960’s, cooling of post-arrest patients began to truly gain traction in the early 2000’s. Hypothermia of post-arrest patients can be best understood as the induction of a hibernation-like state – the goal being to slow the metabolism of the most fragile/damaged organ by decreasing their overall need for oxygen. By decreasing the demand of these organs for fuel, blood is sent to other parts of the body where the oxygen radicals and products of anaerobic metabolism cause less damage. Then, after the body has cleared these dangerous agents from the blood, the patient is slowly re-warmed to normal temperatures and normal blood flow returns to the previously protected vital organs.
Therapeutic hypothermia has shown incredible results in post-arrest patients and has changed the outcomes of these catastrophic events in numerous ways. Without a doubt, the most important benefit of this treatment is the neuro-protection – the fact that patients who have been without a pulse can walk out of the hospital and return to their families and careers as professors, engineers, and entrepreneurs with little to no lasting effects. Hypothermia has proven to be of such benefit, protocols in some cities around the country require Emergency Medical Services to by-pass hospitals that do not offer therapeutic hypothermia post-cardiac arrest, even if CPR is in process!
Detroit Receiving Hypothermia Protocol
