Therapeutic Hypothermia, Research Paper Example

Therapeutic Hypothermia –the act of quickly reducing the core temperature of a human body to halt the damage caused by cardiac arrest or other conditions- has been in use for over half a century. Doctors and researchers have spent the intervening years attempting to perfect the techniques involved in lowering body temperature and in discovering other conditions for which TH many be helpful. This paper will examine the history of TH, the processes and equipment involved, and look to the future of this exciting approach to saving lives.

Therapeutic Hypothermia as we think of it today has only been in use for a few decades, though the idea of cooling the human body for a variety of medical purposes has been in practice for centuries. Reports exist of Russian doctors freezing patients in snow in preparation for amputations, and historians recount that a physician in Napoleon’s army used TH on the battlefield before amputating limbs (Weglinski, 2005). A doctor in the U.S. in the early 20^th century attempted to slow the progression of cancer cells in a patient by inducing hypothermia; while the idea was understandable, the results were not positive (Weglinksi, 2005). More recently TH has been used for everything from treating patients in cardiac arrest to preparing patients for cranial surgery, where TH is used to reduce blood flow in the brain.

TH is most often used to protect the brain from injury and damage after a patient undergoes cardiac arrest. The primary source of injury in the brain after cardiac arrest involves the processes of ischemia and reperfusion (Harden, 2011). Cardiac arrest causes limited or interrupted blood flow to the brain; when the blood flow is restored (reperfusion) too quickly, delicate brain tissues can become damaged (Alzaga, 2005). During I/R the lack of an adequate blood supply leads to interruptions in normal cellular activity. Initially the cells functions overcompensate for the lack of blood supply; as reperfusion occurs these overcompensating cells cannot respond quickly enough to the sudden influx of blood. This discordant cellular activity is untenable and quickly leads to cellular death (Alzaga, 2005).

Inducing TH in comatose patients who have suffered cardiac arrest allows the cell functions to slow, and then to respond to reperfusion more slowly (Arica and Bissonnette, 2007). As the body temperature lowers the cellular activity and demand for oxygen are both reduced, stabilizing the cell functions and helping to maintain adequate levels of Adenosine Triphosphate, which is a critical component in cellular function (Arica and Bissonnette, 2007). When induced in a timely fashion, TH can help to prevent death in many patients. Some debate exists about how quickly TH must be induced to be effective; while most experts agree that it is best to induce TH as quickly as possible, studies have shown that TH can be helpful even when induced 10 hours after the ischemic event (Henkelman, 2011).

There are several ways in which TH can be induced, though they generally fall into one of two primary categories: surface cooling and invasive cooling (Alzaga, 2005). Surface cooling is typically a slower process, and can take anywhere from a few hours up to eight hours to reach optimal cooling levels. Surface cooling can be accomplished by using a hose and tub apparatus to pour cold water over the body; the body can be submerged into cold water with a controlled temperature mechanism in place; specially-designed blankets with a network of internal, water-filled chambers can be wrapped around the body; or variations or combinations of these processes can be used. In the case of infants, selective induction of hypothermia in the head can be achieved through the use of specially-designed blankets or caps that are applied to the head (Alzaga, 2005).

Invasive TH is induced in a number of ways. Cold fluids can be pumped through the body intravenously, rectal lavage of chilled fluids may be used, and in some cases, blood may be pumped from the body, passed through a cooling mechanism, and returned to the body. In some cases a combination of techniques is used; for example, extracorporeal blood may be cooled while at the same time cold fluids and medications are fed into the body intravenously. As the blood returns to the body, both the cooling effect and the medications are delivered rapidly to the impaired systems (Henkelman, 2011).

One common problem associated with TH is the body’s natural tendency to shiver. Shivering can increase metabolic activity, so sedatives are typically used during TH to reduce the potential for shivering and to limit the negative effects of shivering. For the typical patient who is unconscious after cardiac arrest, TH is induced and then maintained for a period of 12-24 hours on average. Rewarming the body after TH is usually accomplished with warming blankets; the body temperature is raised only a few degrees an hour to ensure the smooth return of typical cellular functions (Alzaga, 3005).

TH is being used for a variety of conditions besides those of post-cardiac arrest. A variety of injuries and conditions that can interrupt or alter cerebral blood flow may benefit from the application of TH such as “near-drowning, anoxic brain injury, traumatic head injury, traumatic cardiac arrest, stroke, newborn hypoxic-ischemic encephalopathy, hepatic encephalopathy, bacterial meningitis, cardiac failure, post-operative tachycardia and the acute respiratory distress syndrome” (Alzaga et al, 2005).

While patients with out-of-hospital cardiac arrest are the most likely to receive treatment with TH, doctors and researchers are beginning to explore its use in patients with in-hospital cardiac arrest. Some researchers are suggesting the use of TH in combination with induced comatosis for patients whom are not unconscious after cardiac and ischemic events but are considered likely to suffer from post-incident cerebral damage (Harden, 2011). TH is has been seen to be an effective treatment in many potentially deadly situations, and its use is only likely to increase as doctors and researchers continue to refine the techniques and widen the scope of applicability for this fascinating treatment.

It is clear from both the clinical research and from the practical application of the technique in hospitals and other treatment settings that TH is powerful tool for doctors treating an array of conditions. The ability to slow, and even halt, cerebral blood flow gives doctors several advantages. The first, of course, is in the treatment of post-cardiac-arrest patients who are at risk of cerebral damage during reperfusion.  Another use of TH affords doctors the opportunity to work in critical areas of the brain without the risk that the patient’s blood flow will disrupt surgery. As research into TH advances, new techniques for lowering body temperature are discovered; where cooling blankets and chilled-water applications were the only methods available, doctors now have several invasive procedures that have been shown to work more quickly and with greater control and efficiency than was previously possible. New uses for TH are discovered every day, and it is clear that it has earned its reputation as an important life-saving treatment for many patients who might otherwise not survive.

Bibliography

Alzaga, Ana G. “Therapeutic hypothermia.” Resuscitation. V70 I3 September 2006

Arrica,Mauro; Bissonnette, Bruno. “Therapeutic hypothermia.” Seminars in Cardiothoracic and Vascular Anesthesia. V11 N1. March 2007.

Harden, Jaqueline. “Take a cool look at therapeutic hypothermia.” Nursing. V41 N9. September 2011

Henkelman, Wallace. “Therapeutic hypothermia.” Nevada RNformation. V20 N4 November  2011

Weglinski, Margaret. “Therapeutic hypothermia.” Anesthesiology V3 N103. September 2005.