Out-of-hospital cardiac arrest (CA) is a leading public health problem causing nearly one third of a million deaths annually in the US, accounting for half of all cardiovascular deaths and surpassing deaths from stroke, heart failure, and breast and lung cancer combined. Twenty to fifty percent of CA patients (pts) can be resuscitated initially but many die before hospital discharge or suffer permanent neurologic damage. Therapeutic hypothermia (TH) improves survival and neurological outcomes. Despite aggressive, targeted post arrest management, including TH, approximately 50% of pts die before leaving the hospital due to global ischemia-reperfusion injury (IRI) known as the "post arrest syndrome", 1 which is a sepsis-like state characterized by elevated markers of cellular inflammation and injury. It is believed that TH works by decreasing the body's basal metabolic rate (BMR) and attenuating the systemic inflammatory response (SIR). However, specific triggers of the intense pro-inflammatory response are unclear. This "gap" in knowledge must be closed to identify targeted therapy to decrease IRI and improve outcomes.

Blood flow to the gut is decreased markedly and intestinal tissue becomes ischemic during CA and CPR, particularly when vasoconstrictor drugs such as epinephrine, are given. IRI of the intestine increases intestinal permeability leading to intestinal microbial translocation and endotoxin release that can stimulate and perpetuate systemic inflammation and cause subsequent multi-organ dysfunction. Endotoxin also increases body temperature and energy expenditure and may attenuate TH induced reductions in BMR and hence, decrease efficacy. The purpose of this novel pilot study is to detect systemic endotoxin release following CA in humans and determine association with cytokine activation, and BMR alterations during TH.

Hypothesis 1 Intestinal ischemia during and following Caridac Arrest leads to increased gut permeability and endotoxin release that stimulates the Systemic Inflammatory Response that is responsible for subsequent death and disability after resuscitation.

Hypothesis 2: Different degrees of systemic endotoxin activity variably affect Basic Metabolic Rate during Therapeutic Hypothermia

Serial samples of blood, stool and expired gas will be measured at predetermined timepoints after ROSC from cardiac arrest.

Inclusion Criteria:

Adult, Cardiac Arrest with ROSC receiving Therapeutic Hypothermia-

Exclusion Criteria:

• Age < 18
• Cardiac Arrest of traumatic etiology
• Known to be pregnant
• Prisoner

All adult patients resuscitated from Cardiac Arrest successfully and undergoing therapeutic hypothermia will be evaluated for potential inclusion