1. Post-Cardiac Arrest Therapeutic Hypothermia Laura Bagley, Cali Roen, Anthony Schuler, Amy Weaver BME 301 March 7, 2008

2. Client:Darren Bean, M.D. UW Emergency Medicine/MedFlight Director UW Level 1 Heart Attack Program Medical Director, Madison Fire Department Advisor:Willis Tompkins Dept. of Biomedical Engineering

3. Background –Post-Cardiac Arrest –Therapeutic Induced Hypothermia –Existing Devices Saline Cooling Device Requirements Preliminary Saline Testing Insulation and Cooling Options Future Work

4. Brain damage occurs after cardiac arrest –Ischemia Anoxic brain injury –Reperfusion damage Restored blood flow reintroduces oxygen to brain Oxygen damages cellular proteins Toxic free radicals released Brain damage Inducing hypothermia slows ischemic cascade

5. Australian study, 2002 –21 of 43 hypothermia patients had good outcome (43%) –9 of 33 standard care patients had good outcome (26%) European study, 2002 –75 of 136 hypothermia patients had good outcome (55%) –57 of 137 standard care patients had good outcome (42%) Increase in survival rate and quality of life

6. Utilizes cold saline –Typically infuse 2L per patient during transport –Average of 1L every 15 minutes –Infused at 4°C –Target core body temperature of 32°C to 34°C Emergency protocol for Dane County –Store saline in refrigerator –Place in cooler with ice for transport

7. Cool saline to 4°C Maintain temperature of saline during transport and infusion Achieve core body temperature of 32°C-34°C

8. All components must be strapped down in helicopter Keep saline at 4°C for up to 40 minutes Saline should not freeze or crystallize Fit into available space in helicopter Easily transportable Cost effective

9. Arctic Sun Temperature Management System® by Medivance –Pads filled with temperature controlled water applied to patient’s skin –Cools by thermal conduction INNERCOOL –Endovascular cooling –Catheter placed in inferior vena cava –Cooled saline from console exchanges heat with circulating blood www.medivance.com

10. Temperature changes –Temperature increased in tubing –Temperature in bag increased exponentially Flow rate –15 minutes to empty bag with 16-gauge needle –Rate slowed as bag emptied

11. Cooling saline below 4˚C would allow for warming −Determine freezing point of saline −Purchase separate refrigerator kept just above freezing point http://www.uthscsa.edu/mw/photogallery/Me dia/biomed/pages/IV_BAG.htm

12. Insulating material surrounds ice pack (neoprene) Opening at top to hook bag View slit on front to see level of saline Also insulate tubing –Coiled versus straight

13. Option 1: Standard Cooler w/ ice –Smaller –More portable –Less reliable cooling Option 2: Peltier Cooler –Thermoelectric –Relies on temperature differential Option 3: Miniature Refrigerator –Maintain constant temperature –Requires power supply http://www.bigfrogmountain.com/engel/Engel% 2015.htm

14. CriteriaWeight Standard Cooler Thermoelectric Cooler Miniature Refrigerator Cooling Ability0.40123 Size0.20321 Power Required0.10321 Client Preference 0.20123 Cost0.10321 Total1.001.82.02.2

15. Further testing –Temperature changes in a warmer environment –Freezing point of saline –Effects of tubing configuration on flow rate Prototype construction Next semester –Test this semester’s prototype –Develop alternative cooling methods for the patient

16. Bernard, S.A., et al. Treatment of Comatose Survivors of Out-of-Hospital Cardiac Arrest with Induced Hypothermia. N Engl J Med. 2002. The Hypothermia after Cardiac Arrest Study Group. Mild Therapeutic Hypothermia to Improve Neurological Outcome after Cardiac Arrest. N Engl J Med. 2002. Kim, F., et al. Pilot study of rapid infusion of 2L of 4 degrees C normal saline for induction of mild hypothermia in hospitalized, comatose survivors of out- of-hospital cardiac arrest. Circulation. 2005.