Determinants of heat generation in patients treated with therapeutic hypothermia following cardiac arrest.

BACKGROUND: Therapeutic hypothermia (TH) is recommended to reduce ischemic brain injury after cardiac arrest. The variables that predict heat generation by patients receiving TH are uncertain, as is how this heat generation relates to neurologic outcome. We hypothesized that patient characteristics, medication use, inflammation, and organ injury would be associated with heat generation. We further hypothesized that neurologic outcome would be most strongly associated with heat generation. METHODS AND RESULTS: Surface and intravascular cooling devices were used to provide TH in 57 consecutive cardiac arrest patients. Device water temperatures during the maintenance (33°C) phase were collected. Patient heat generation was quantified as the "heat index" (HI), which was the inverse average water temperature over a minimum of 2 hours of maintenance hypothermia. Variables measuring reduced ischemic injury and improved baseline health were significantly associated with HI. After controlling for presenting rhythm, a higher HI was independently associated with favorable disposition (OR=2.2; 95% CI 1.2 to 4.1; P=0.014) and favorable Cerebral Performance Category (OR=1.8; 95% CI 1.0 to 3.1; P=0.035). Higher HI predicted favorable disposition (receiver-operator area under the curve 0.71, P=0.029). HI was linearly correlated with arteriovenous CO2 (r=0.69; P=0.041) but not O2 (r=0.13; P=0.741) gradients. CONCLUSIONS: In cardiac arrest patients receiving TH, greater heat generation is associated with better baseline health, reduced ischemic injury, and improved neurologic function, which results in higher metabolism. HI can control for confounding effects of patient heat generation in future clinical trials of rapid TH and offers early prognostic information.

Therapeutic hypothermia for cardiovascular collapse and severe respiratory distress after amniotic fluid embolism.

Amniotic fluid embolism (AFE) is one of the most catastrophic complications that can occur during pregnancy or in the immediate postpartum period, frequently complicated by profound shock and cardiovascular collapse as well as severe respiratory distress. Therapeutic hypothermia (TH) is now commonly used to improve neurological outcomes after various types of hypoxic injury and is widely used in the treatment of postanoxic injury after cardiac arrest (CA). To our knowledge, no studies have evaluated whether TH could be effectively used in AFE, and its use for this indication has not been described previously. We describe the case of a 32-year-old woman, who developed clinical manifestations of AFE and suffered a CA in the 29th week of her pregnancy. She received prolonged CPR (40 minutes until ROSC) and remained comatose. TH was induced and maintained for a total of 60 hours using an endovascular device, followed by controlled rewarming and maintenance of strict normothermia. The patient survived and was neurologically intact (CPC 1) at 6 months of follow up.