Inducing Therapeutic Hypothermia. Sarah Byce

Transcription

1 Inducing Therapeutic Hypothermia Sarah Byce Herrington CHM November 2012

2 Byce 2 Statement of Question How many instant cold packs will it take to induce therapeutic hypothermia on a patient who has suffered from a heart attack? Background For this lab, instant ice packs were cut open; the ammonium nitrate crystals were mixed with water to determine the amount of heat given off. This would help calculate the number of ice packs needed to cool the body to therapeutic hypothermia. To do these calculations, a basic understanding of the heat equation is needed (Appendix: Equation 1). Procedures In this experiment, 100mL of tap water was poured into a plastic graduated cylinder. The temperature was taken of this water while in the cylinder. The entire contents, minus the water bag, of the instant cold pack were weighed. The total weight of the ammonium nitrate crystals was then divided by three to get three trials (Appendix: Calculation 1). A third of ammonium nitrate was then weighted out and poured into a Styrofoam coffee cup. The coffee cup was used to keep in as much as the heat as possible as opposed to a glass beaker. The water from the graduated cylinder was poured into the coffee cup. A thermometer was immediately placed in the coffee cup while the mixture was continuously being stirred. Once the thermometer temperature leveled off, the temperature was recorded (Appendix: Table 1) and the experiment was repeated two more times. After all the trials were completed calculations needed to be done to calculate the heat given off by the entire ice pack. Data and Observations *see Appendix Calculations *see Appendix Analysis and Discussion 1. The energy change in Joules when one gram of ammonium nitrate is dissolved: total energy change of 1 bag (Appendix: Equation 2) total mass of ammonium nitrate 10,460 J g J 2. The energy change in Joules of the entire cold pack using 100 ml of water (Appendix: Equation 2): (3, J) + (3, J) + (3, J) 10,460 J

3 Byce 3 3. The number of our cold packs needed to induce therapeutic hypothermia on the patient: body heat (J)(Appendix: Calculation 2) heat of one cold pack (J) 840,000 J 10,460 J 80 cold packs 4. The cold packs on the plane have 200 grams of ammonium nitrate, because of this less cold packs would be needed: weight of our ammonium nitrate energy of cold pack 40.11g 10,460 J weight of plane ammonium nitrate X 200 g 40.11X 2,092,000 X 52, J X body heat (J)(Appendix: Calculation 2) energy of plane ice pack 840,000 J 16 cold packs 52, J 5. When compared to the class data, when sorted by amount of energy change for one gram of ammonium nitrate (Appendix: Table 2), our data was on the high end of the scale. There was only one group that had a higher value for energy being released. When the data was sorted by the number of our cold packs needed, our data was fairly in the middle (Appendix: Table 3). From this sort, it was clear to see the lower the energy change for ammonium nitrate the more ice packs needed to induce hypothermia. It was also clear to see a direct relationship between the number of plane cold packs needed compared to the number of your cold packs needed, which only makes sense, the less of your cold packs, the less plane cold packs needed. There were a couple outliers however; one group said there should be 61 cold packs where another said 1,043 packs were needed. 6. Some of the things that could contribute to the calculation differences are inconsistent or incorrect measuring. There were different procedures for determining energy change and number of cold packs. A major difference was the size of the ammonium nitrate crystals; some had white crystals where others had small brown balls. 7. Some things that could improve the experiment would be, having more cold packs to test. If this was done, my group wouldn t have had to divide by three, we could have used an entire packet. After doing the experiment, I realized we should have measured the amount of water in the pack, to know for sure how the cold pack would have reacted.

4 Byce 4 This could also affect how cold the pack gets. Maybe the more water the colder or warmer the ice pack gets. Conclusion In conclusion, it was determined, from our procedure, it takes about 261 J to cool one gram of ammonium nitrate. It would take 80 of our cold packs to induce therapeutic hypothermia and about 16 plane cold packs to induce the hypothermia. Based on the class data, the greater the energy change the greater the number of cold packs needed. The goal for this experiment was met when the conclusion, or understanding, about how many cold packs would be needed to induce hypothermia as well as how this is happening. This lab taught that when water is added to ammonium nitrate it becomes colder and there is an energy change between these two substances. This concept is important for understanding temperature regulation, as well as how a cold pack works. The experiment went smoothly, but could be improved upon. It may have been better to get a few cold packs to work with so know a better idea of the energy change.

5 Byce 5 Appendix A: Tables, Calculations, and Equations Equation 1: Determining Heat q mc T q heat (Joules); m mass (grams); c specific heat (J/g* C); T change in temperature ( C) Calculation 1: Trial Weights Trial Weight 40.11g g total weight of ice pack (g) 3 Table 1: Individual Data Equation 2: Total Energy Change Total Energy Change Trial One + Trial Two + Trial Three Calculation 2: Heat Removed from the Body q mc T q?; m 60kg; c 3.5 J/g* C; T (37 C-33 C) q (60,000g)(3.5 J/g C)(37 C 33 C) 840,000 J 840 kj

6 Byce 6 Table 2: Sorted Class Data- Energy Change Table 3: Sorted Class Data- Number of Our Cold Packs Needed