**12. Hypovolemia, fluid balance and electrolytes, glycemia**

A common problem is severe electrolyte disorders hypokalemia, hypomagnesemia, hypophosphatemia during induction of cooling. These may cause further arrhythmias in post-arrest patients. Hypothermia decreases insulin sensitivity and insulin secretion, which often leads to hyperglycemia. Tight control of glucose levels may decrease morbidity and mortality in ICU patients, but the exact levels at which glycemia needs to be maintained is controversial. During rewarming, glucose levels tend to drop, and therefore, insulin may need to be decreased or discontinued. Likewise, hyperkalemia and hypermagnesemia are common during rewarming, and cardiac arrests have occurred when the clinician s unaware of this phenomenon. Hypothermia also induces a metabolic acidosis by increased synthesis of glycerol, free fatty acids, ketones and lactate. These changes are normal metabolic consequences of hypothermia and should not be attributed to complications such as bowel ischemia.4

Hypotension can occur through hypovolemia, the cold diuresis, that occurs in hypothermia, and the use of agents like mannitol in TBI or diuretics in the setting of cardiomyopathies can further exacerbate this. If this is unrecognized, the problem is worse in the rewarming phase when vasodilatation often occurs, and profound shock ensues. Cueni-Villoz N, et al.

#### **13. Summary**

16 Therapeutic Hypothermia in Brain Injury

**9. Coagulation** 

bleeding risk with cooling/PCI.35,36

**11. Gastrointestinal dysfunction** 

resuscitation. *Intensive Care Med* 1988; 14(5):575-7.

**10. Pressure ulcers** 

Many experts recommend continuous intravenous antiepileptic drugs at this stage. Midazolam is the safest anesthetic agent in treating SE. Doses as high as 3 to 5 mg/kg/h may be necessary to maintain seizure suppression in the most refractory cases. Tachyphylaxis is often encountered when prolonged infusions are used. The other agents used to treat SE are propofol, and barbiturates (Thiopental or pentobarbital). Barbiturates produce hypotension, and myocardial depression, this may pose further challenges in the post cardiac arrest setting. Other side effects include ileus, hepatotoxicity, increased susceptibility to infections and very prolonged sedation. Propofol can be associated with propofol infusion syndrome as discussed earlier. Valproic acid, levetiracetam, are emerging as alternative agents. Fosphenytoin is an antiepileptic that is often added in these patients. Fosphenytoin is a prodrug of phenytoin and its preparation does not include propylene glycol. It can be administered faster than IV phenytoin, and has less adverse cardiac events with IV infusion compared to phenytoin. It is much less likely to produce local tissue reactions, and it can be infused faster than phenytoin.34 As with status epilepticus from other causes, it is not clear whether burst suppression on EEG is superior to seizure suppression. No data on seizure

Bleeding diatheses occur in the setting of mild therapeutic hypothermia. For every 1 °C decrease in temperature, coagulation-factor function is decreased by 10%. Watts et al showed that in trauma patients, enzyme activity alteration, platelet dysfunction and changes in fibrin pathways occur. Clinically significant bleeding is rarely a significant problem, even in traumatic brain injury patients. Schefold et al. in a prospective observational study of 31 patients with AMI and mild induced hypothermia and primary PCI found no excessive

Values of standard coagulation tests such as prothrombin time and partial thromboplastin times are usually normal, because these tests are usually performed at 37°C in the lab. Tests

Skin integrity should be assessed carefully and frequently. The surface cooling, vasoconstrictive response to cooling can increase skin breakdown in hypothermic patients.6

Hypothermia patients have GI dysmotility, ileus. Caution needs to be exercised with promotility agents like Erythromycin, metoclopramide, neostigmine, as they can induce arrhythmias. Increased serum amylase levels are common, but patients rarely have significant pancreatitis. Enteral nutrition can help decrease risk of bacterial translocation. Gaussorgues P, et al. Bacteremia following cardiac arrest and cardiopulmonary

will be prolonged only if they are performed at the patient's actual core temperature

prophylaxis after hypoxic ischemic encephalopathy are available

In conclusion, hypothermia is becoming increasingly used across many intensive care units, and the applications could expand well beyond the current indications. It is important to use safe, effective cooling methods, recognize, prevent and treat various adverse events that could occur, so we can improve the survival of these patients.
