Hypothermia After Cardiac Arrest Jimmy Hall, RN, MSN

Objectives Identify goal of Hypothermia Therapy List methods of invasive and non-invasive hypothermia Identify side effects of hypothermia therapy

History The first case report describing the clinical use of mild hypothermia after cardiac arrest was reported by Williams and Spencer in At this time, it was recommended that “patients who show evidence of central nervous system damage following cardiac resuscitation should be promptly cooled to 32°C to 34°C” – the current guideline. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Why Hypothermia After Cardiac Arrest?

Why Hypothermia Therapy? The only therapy that has been shown to improve survival and neurological outcome after sudden cardiac arrest is the induction of mild therapeutic hypothermia for 12 to 24 hours. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Controlled hypothermia has many protective barriers:  Reduction of Brain Metabolism  Reduction of Reactive Oxygen Species Formation  Inhibition of Excitatory Amino Acid Release  Lessening of the Immune Response During Reperfusion  Inhibition of Apoptosis Why Hypothermia Therapy? Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Hypothermia leads to a progressive reduction of metabolism, reflected by depression of electrical activity in the brain and therefore of Oxygen demand and Carbon Dioxide production. Metabolism is reduced by 5% to 8% per degree Celsius reduction of core temperature. Why Hypothermia Therapy? Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

What is the Temperature Goal? The temperature should be maintained between 32°C (89.6°F) and 34°C (93.2°F). It is recommended that the temperature stay within this range for 12 – 24 hours. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Which Patients Need It? Comatose survivors after out-of-hospital cardiac arrest with a primary rhythm of ventricular fibrillation Hypothermia should also be considered for non-VF rhythms and in-hospital cardiac arrest. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Who Should Not Receive?  Patients with:  Trauma or Severe Bleeding  Terminal Disease  Patients with Coagulopathy (except therapeutically induced) Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Methods of Cooling

Cooling Methods There are various forms of cooling  Invasive Ice-Cold IV Fluids Intravascular Cooling Catheters Body Cavity Lavage  Noninvasive Ice Packs Cooling Blankets Body Immersion into Ice Water Head/Brain Cooling Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Invasive Methods Ice-Cold IV Fluids – A bolus of cold saline alone is effective in inducting hypothermia (but not sufficient for maintaining mild therapeutic hypothermia after its induction). – Its great value is primarily the ability to initiate hypothermia and the compatibility with other cooling devices. – Typically given by using a pressure bag – for rapid infusion. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Endovascular Cooling – A catheter containing circulating saline at a controlled temperature is placed in a large vein (usually into the inferior vena cava via the femoral vein). – The fluid is pumped through the catheter by a bedside heat exchanger using temperature feedback of the patient to accurately control core temperature. Invasive Methods Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Non-Invasive Methods Surface Cooling – Ice packs – applied to head, neck, torso, and extremities of the patient provide a slow cooling rate – Cooling Blanket – operate with feedback control to circulate cold water in pads/blankets – Body Immersion – immersion of body in ice water; allows direct contact of water to the skin and is a fast method of surface cooling Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Ice Packs Ice packs are placed in anatomic areas that have large heat-exchange capability:  Head  Neck  Axilla  Groin The use of fans often accompanies the use of ice packs to promote evaporative cooling. Adler, J. (2010). Therapeutic Hypothermia. Retrieved from

Cooling Blanket The pad contains coils that circulate a chilled solution. Lippincott Williams & Wilkins. (2010). Hyperthermia-hypothermia blanket use.

Cooling Blanket The blanket's temperature can be adjusted to help keep the patient's temperature in the ordered range. In automatic operation, insert the thermometer probe in the patient's rectum and tape it in place to prevent accidental dislodgment. – If rectal insertion is contraindicated, tuck a skin probe deep into the axilla, and secure it with tape. Use a sheet or bath blanket as insulation between the patient and the blanket. Keep the patient's skin, bedclothes, and blanket cover free of perspiration and condensation Lippincott Williams & Wilkins. (2010). Hyperthermia-hypothermia blanket use.

Head Cooling – Selective head cooling has been tried in adults but promises best results in children because of favorable relation of head-to-body surface area. – New devices, primarily the RhinoChill Non-Invasive Device, use nasopharyngeal evaporative cooling to cool basal brain regions Non-Invasive Methods Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

RhinoChill Non-Invasive Head Cooling System The RhinoChill System uses a non-invasive nasal catheter that sprays a rapidly evaporating, inert coolant liquid into the nasal cavity, a large area situated beneath the brain that acts as a heat exchanger. As the liquid evaporates, heat is directly removed from the base of the skull and surrounding tissues via conduction and indirectly through the blood via convection.

RhinoChill Non-Invasive Head Cooling System Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Helmet Cooling Device Hachimi-Idrissi et al used a helmet cooling device in their human clinical study. The soft bonnet-like helmet contained a solution of aqueous glycerol that facilitated heat exchange. This method works, but it may be slower than other methods. Adler, J. (2010). Therapeutic Hypothermia. Retrieved from

Temperature Monitoring

Unintentional overcooling or rewarming may worsen outcome and put the patient at risk for lethal arrhythmias – Temperature measurements from various sites do not differ significantly when slow cooling is performed. – With rapid cooling, direct blood temperature or esophageal temperature should be obtained. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Central Temperature Probe should be used – Such as: Esophageal Intravasal/intravascular Bladder Tympanic (ear) and Rectal temperatures are insufficient. Temperature Monitoring Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Side Effects of Hypothermia Therapy

Complications Complications of Mild Therapeutic Hypothermia Include:  Shivering  Changes in the Immune System  Electrolyte Changes  Effects on the Clotting System  Cardiovascular and Hemodynamic Effects  Drug Metabolism Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Shivering Shivering could counteract the beneficial effects of hypothermia by raising energy and Oxygen demands. In studies, muscle paralysis is used to prevent shivering. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Electrolyte Changes Minor electrolyte changes that can be expected include: – Hypernatremia – Hypokalemia – Hypomagnesemia – Hypophosphatemia – Hypocalcemia Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Cardiovascular Effects Hypothermia leads to bradycardia and a rise in systemic vascular resistance. The risk of arrhythmias rises with temperatures below 30°C (86°F) but is very low at 33°C (91.4°F). Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Drug Metabolism Hypothermia reduces the systemic clearance of certain medications between 7% and 22% per degree Celsius. Fentanyl concentration has been found to rise at body temperatures below mild hypothermia. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Other Side Effects Hypothermia has an anti-coagulatory effect proportional to its depth. The detection of infections might be delayed because fever as an indicator of infection is suppressed by hypothermia therapy. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52( ).

Summary Mild therapeutic hypothermia for 12 to 24 hours has been shown to improve survival and neurological outcome after sudden cardiac arrest Many methods are used, invasive and non- invasive Close monitoring of temperature is needed Many side effects can occur as a result of the hypothermia therapy