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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.
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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 1958. • 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(168-179).
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 for12 to 24 hours. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52(168-179).
Why Hypothermia Therapy? • 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 Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52(168-179).
Why Hypothermia Therapy? • 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. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52(168-179).
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(168-179).
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(168-179).
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(168-179).
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(168-179).
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(168-179).
Invasive Methods • 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. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52(168-179).
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(168-179).
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 http://emedicine.medscape.com/article/812407-overview#aw2aab6b6
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.
Non-Invasive Methods • 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 Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52(168-179).
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. http://medgadget.com/2011/02/rhinochill_noninvasive_head_cooling_system_poised_for_european_market_introduction.html
RhinoChill Non-Invasive Head Cooling System Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52(168-179). http://medgadget.com/2011/02/rhinochill_noninvasive_head_cooling_system_poised_for_european_market_introduction.html
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 http://emedicine.medscape.com/article/812407-overview#aw2aab6b6
Temperature Monitoring • Unintentional overcooling or rewarmingmay 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(168-179).
Temperature Monitoring • Central Temperature Probe should be used • Such as: • Esophageal • Intravasal/intravascular • Bladder • Tympanic (ear) and Rectal temperatures are insufficient. Janata, A. & Holzer, M. (2009). Hypothermia after cardiac arrest. Progress in Cardiovascular Diseases: 52(168-179).
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(168-179).
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(168-179).
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(168-179).
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(168-179).
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(168-179).
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(168-179).
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