**2. Cardiac arrest**

Despite advances in ICU care, cardiac arrest remains a significant cause of death in many countries. Mortality reports vary from 65 to 95% for out-of hospital cardiac arrest. I is a class –I recommendation now that after return of spontaneous circulation in out-of-hospital VF cardiac arrest , patients that remain comatose should be subjected to hypothermia at 32°C to 34°C for 12 to 24 hours. This may also be applied to comatose adult patients with spontaneous circulation after OHCA from a non VF rhythm or in-hospital cardiac arrest.1

Therapeutic Hypothermia: Adverse Events, Recognition, Prevention and Treatment Strategies 5

Hypothermia may decrease infarct size in patients with acute myocardial infarction after

Intraoperative hypothermia is used during neurological surgery but without strong evidence from randomized controlled trials. Indications are being studied in the areas of

Both Invasive and non invasive cooling methods have been developed and used to induce hypothermia. The ideal cooling technique should offer efficacy, speed of cooling for target organs, and offer ease of use and transport. It should also have the ability to provide

Surface cooling as a noninvasive method to induce hypothermia is easy to use, on the other hand requires more time to achieve the target temperature. There are two described

Generalized cooling is achieved through the use of cooling blankets, ice packs, and cooling pads. Care should be paid to prevent cold injury to the patient's skin. This method has variability in time to cooling, ranging from 0.03 to 0.98 °C per hour and difficulty in titration

Pads that provide direct thermal conduction through the skin are also used; these are unlike conventional water blankets or wraps where heat transfer is by convection. The cooling rate is reported to be 1.5°C/hour or more. Hydrogel-coated pads in these circulate temperaturecontrolled water under negative pressure, and are placed usually on the patient's abdomen,

Selective brain cooling is another non invasive method. The most commonly used methods are cooling caps and helmets that contain a solution of aqueous glycerol to facilitate heat exchange. Helmet devices do not appear to provide particularly significant protection to the

Several other limitations exist in surface cooling methods. Through vasoconstriction, shivering, redirection of blood flow away from extremities, they create thermal energy. Overcooling occurs. In a study involving 32 patients where surface cooling was used to induce hypothermia, 63% of patients were overcooled, increasing the risk for adverse events. Another problem with surface cooling is cold injury, causing pressure ulcers and

**5. MI** 

**Methods 6** 

controlled rewarming.

of temperature.

back and thighs.

**Surface cooling: Dine et al** 

**6. Other indications** 

**7. Induction of hypothermia** 

emergency percutaneous coronary intervention

SAH, Neurosurgery, liver failure, Spinal cord injury.

methods: generalized cooling, and selective brain cooling.

brain, but they reduce core temperature slowly.

Several unanswered questions however remain, due to lack of randomized studies. These in part, relate to time from initiation of therapy to achieving target temperature, and whether this is a significant predictor of outcome. The optimal rate of cooling is also an unanswered question, so is the optimal duration of TH in some settings, albeit in the setting of cardiac arrest, improved outcomes have been demonstrated with 12 and 24 hrs of TH at 32°C to 34°C. Hypothermia for neonatal asphyxia is commonly performed for 72 hrs, while hypothermia for cerebral edema associated with liver failure has been reported for as long as 5 days. 2

#### **3. TBI**

Traumatic brain injury (TBI) is a leading cause of death and disability in young people in Western countries. The neuroprotectant effects are thought to be related to decreased metabolic rate, cerebral blood flow, decreased release of excitatory neurotransmitters, decreased apoptosis, cerebral edema, decreased cytokine response etc.3

While studies have shown that Hypothermia is clearly effective in controlling intracranial hypertension (level of evidence: class I); it has been difficult to show that lowering ICP definitely improves outcomes. Few positive studies with regard to survival and improved neurological outcome have been shown mainly in tertiary referral centers with experience in use of hypothermia. Here again, as in cardiac arrest, more unanswered questions remainduration, time of cooling and rewarming, type of rewarming. Currently, most centers perform it for at least 48 hours. Rewarming is typically done slowly, over at least 24 h (level of evidence: class IIa). 4 If there is evidence of ICP elevation during rewarming, again no definite recommendations are available, but most experts will proceed with repeat cooling. It could be that in traumatic brain injury, other therapies, including cerebrospinal fluid drainage, osmolar therapies, sedation, barbiturate coma, and decompressive craniectomy may confer additional benefits that may make it more difficult to prove that Therapeutic hypothermia is superior.

#### **4. Stroke**

Similar to Cardiac arrest and TBI there is evidence from animal studies that show benefits of therapeutic hypothermia in stroke. Use of hypothermia in stroke remains experimental, until large prospective randomized human clinical trials using hypothermia in acute stroke are completed. 5
