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How Therapeutic Hypothermia Works

        Health | ER

You Should Put Some Ice on That
A research assistant from the Hospital of the University of Pennsylvania demonstrates how a patient receiving therapeutic hypothermia might have his or her leg wrapped.
A research assistant from the Hospital of the University of Pennsylvania demonstrates how a patient receiving therapeutic hypothermia might have his or her leg wrapped.
© Tim Shaffer/Reuters/Corbis

In the previous section, we described the biochemical rioting and looting that sweeps through your brain cells when oxygen is lacking, and the further injury that accumulates after blood flow returns. We also identified a rogue's gallery of troublemakers: starving mitochondria, wandering electrolytes, destructive enzymes, programmed cell death, runaway neuron excitability, unwanted inflammation and poorly timed clotting.

Therapeutic hypothermia blunts the force of all of these factors. First and foremost, it slows the cerebral metabolic rate, thereby reducing oxygen demand by brain cells and staving off mitochondrial meltdown [sources: Adler at al.; Delfin; Gibson and Andrews; Winslow]. By stabilizing glutamate release, it also put the brakes on damage-boosting cell excitation [sources: Adler et al.; Deckard and Ebright; Delfin; Merck Manual]. TH also shores up the blood-brain barrier by making small blood vessels called arterioles less leaky [sources: Deckard and Ebright; Gibson and Andrews].

Remember how runaway calcium levels generally wrecked brain cells and set off a self-feeding chain reaction? Hypothermia calms that down too, thereby lowering the rate of mitochondria damage, cell death and all that typically follows, including destructive free radical production and brain inflammation [sources: Adler et al.; Deckard and Ebright; Delfin; Gibson and Andrews; Merck Manual]. TH also reduces the inflammation response by tamping down on the release of cell-signaling proteins called cytokines, which can contribute to clotting, blood vessel breakdown and cell death [sources: Adler at al.; Delfin; Gibson and Andrews; Merck Manual]. Finally, studies have shown that therapeutic hypothermia reduces seizure activity, an important factor governing the chances of positive neurological recovery [source: Gibson and Andrews].

But don't take the polar plunge just yet. There are good reasons our bodies try to maintain a constant temperature. More to the point, therapeutic hypothermia comes with a number of side effects that might occur during the cooling, maintenance and rewarming stages of the process. These can include shivering, cardiovascular problems, mild coagulation problems, issues with blood glucose, electrolyte imbalances and, rarely, pneumonia [sources: Deckard and Ebright; Gibson and Andrews]. During warming, the patent may experience a rise in intracranial pressure and, occasionally (and somewhat ironically), hyperthermia (elevated body temperature) [source: Adler at al.].

Consequently, TH requires careful monitoring of a variety of vital signs during both the procedure and recovery. Let's take a closer look at the actual procedure of therapeutic hypothermia to see how this plays out.


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