1. POST-CARDIAC ARREST THERAPEUTIC HYPOTHERMIA Laura Bagley, Calista Roen, Anthony Schuler, Amy Weaver Client: Dr. Darren Bean Advisor: Willis Tompkins References Future Work Maintain saline temperature between 4°C and 8°C for at least 40 min. Function effectively in ambient temperatures up to 45 °C Fit in small available space Able to be secured within helicopter Independent of external power source Maintain temperature above saline freezing point Low manufacturing cost Design Specifications Prototype Prototype Testing Acknowledgements : We would like to thank Professor Jay Martin, Emmanuel Millet, Denise DeSerio and the MedFlight staff for their assistance. Abstract Research proved that inducing hypothermia in post-cardiac arrest patients is an effective treatment to reduce brain damage that results from ischemia and blood reperfusion. In Dane County, the method for inducing hypothermia in a post-cardiac arrest patient during transport to a hospital involves infusing chilled saline into the patient. Saline is stored in a refrigerator at the hospital and is placed in a soft-sided cooler with ice for transport to the patient’s location. The main problem with this protocol is cooling the saline and keeping it cold, especially when the ambient temperature is high. Optimally, the saline should be at a temperature of 4°C when it is infused into a patient. The cooler currently in use does not sufficiently maintain the required saline temperature. The goal of this project was to design a device that can be used to cool the saline and keep its temperature at 4°C during infusion. The device will be used in ambulances and helicopters so space constraints, as well as power availability, needed to be considered. [1] Bernard, S.A., et al. 2002. Treatment of Comatose Survivors of Out-of-Hospital Cardiac Arrest with Induced Hypothermia. New England Journal of Medicine, 346 (8):557-563. [2] The Hypothermia after Cardiac Arrest Study Group. 2002. Mild Therapeutic Hypothermia to Improve Neurological Outcome after Cardiac Arrest. New England Journal of Medicine, 346 (8): 549-556. [3] Kim, F., et al. 2007. Pilot Randomized Clinical Trial of Prehospital Induction of Mild Hypothermia in Out-of-Hospital Cardiac Arrest Patients With a Rapid Infusion of 4° C Normal Saline. Circulation, 115 (24): 064-3070. Our device maintained a saline temperature necessary for inducing hypothermia at elevated ambient temperatures, but there is still additional work that can be done. We would like our client to use the device and provide us with feedback on the ease of use and on-site effectiveness. We would also like to do more tests to ensure repeatable results. It may also be beneficial to investigate the feasibility of initially cooling the saline to around 0°C. Background Anoxic brain injury is common after cardiac arrest. When oxygen is restored to the brain, toxic free radicals are released, causing reperfusion damage. Inducing hypothermia slows brain damage. Two studies, one in Australia and one in England, have shown that induction of hypothermia after cardiac arrest improves both survival rates and quality of life. Currently in Dane County, hypothermia is induced during transport to the hospital by infusing cold saline. Typically, 2 liters of 4˚C saline are infused in the patient at a rate of 1 liter every 15 minutes. The target body temperature for hypothermia is 32°C to 34°C. Saline is stored in a refrigerator and placed in a cooler with ice for transport. The bag of saline is inserted into an insulating sleeve constructed of neoprene. The sleeve includes a pocket on the back for a removable ice pack. The tubing is coiled and insulated with a neoprene pocket. The saline was run from the bag at an ambient temperature of 28˚C. The temperature in the bag and at the end of the tubing was recorded every minute. To test the effectiveness of the device, the test was performed with and without the insulating sleeves in place. Preliminary Testing This test showed the effectiveness of neoprene as an insulator. The graph shows that temperature increases linearly over time when no saline is run out of the bag. The insulated bag warmed at a slower rate reaching a maximum temperature 3.5°C after 15 minutes. The uninsulated bag reached a maximum temperature of 7.5°C after 15 minutes. The graph shows that temperature increases exponentially over time when saline is run out of the bag. As the volume of saline in the bag decreases, more heat is lost to the surroundings. The saline in the bag reached a maximum temperature of 10°C and the saline in the tubing reached a maximum temperature of 13°C. The graph shows the effectiveness of the insulating sleeves. The saline in the bag reached a maximum temperature of 6.5°C and the saline in the tubing reached a maximum temperature of 8.5°C. 11” 6” On the left is the neoprene sleeve to insulate the saline bag. The pocket to insulate the tubing is shown on the right.