1. Agent Monitoring For CEs and BMETs

2. Ready

3. Anesthetic Agent Monitoring James H. Philip, M.E.(E.), M.D. Anesthesiologist and Director of Technology Assessment Brigham and Women's Hospital Medical Liaison, Department of Biomedical Engineering Partners HealthCare System Associate Professor of Anaesthesia Harvard Medical School I have a financial interest in Gas Man ® and Med Man Simulations, Inc. I have performed research on some of the drugs or devices described © 1984 - 2003, James H Philip, all rights reserved.

4. 1991, a year I taught this course

5. Sevo Iso Des Best Vaporizer Order

6. Piezoelectric measure of rubber absorption Infrared absorption (IR) Acoustic spectroscopy (IR variant) Raman spectroscopy (RASCAL) Mass spectrometry (Mass Spec) Agent Monitor Technologies

7. Piezoelectric measure of rubber absorption Offshoot of “Narkotest” Rubber band in a box with lever and pointer Rubber absorbed anesthetic and stretched Needle indicated concentration Piezoelectric measure Measure piezoelectric crystal resonant frequency Deposit Lipid (rubber) on surface of crystal Measure new resonant frequency as reference Expose to agent Lipid gets heavier, slows oscillation Frequency change is proportional to anesthetic agent

8. IR Absorption Monitor

9. Acoustic Spectroscopy Variant of IR No longer on market

10. RASCAL Raman Spectrometer

11. RASCAL™ in OR

12. Mass Spectrometer (usually multiplexed)

13. Only the RASCAL or Mass Spec monitor nitrogen

14. Piezoelectric measure of rubber absorption Infrared absorption (IR) [BWH] Acoustic spectroscopy (IR variant) Raman spectroscopy (RASCAL) [BWH] Mass spectrometry (Mass Spec) Agent Monitor Technologies

15. Infrared absorption (IR) at BWH Ohmeda RGM Ohmeda Central Display ADS Datex Ultima (two varieties) GEMS IT (Marquette) SAM

16. Many monitors Don’t have agent identification (Agent ID) Won’t detect incorrect agent Won’t detect mixed agents

17. Several Views of Sevoflurane

18. Reset agent choice on RGM

19. Several Views of Sevoflurane RGM Sev Des Iso Enf Hal Reading I 1.4 1.9 2.4 2.9 15.0 Reading E 1.1 1.7 2.0 2.3 11.7 Ratio I 1.0 1.4 1.7 2.1 10.7 Ratio E 1.0 1.5 1.8 2.1 10.6 Average 1.0 1.5 1.8 2.1 10.7 RGM Sev Des Iso Enf Hal Reset agent choice on RGM

22. Vapor spectra overlap 3.2  Sevo Des Iso Enf Hal IR Wavelengh

23. Agent ID (identification) and Mixed Agents

24. Agent ID ?

25. Agent Code

26. Vapor spectra overlap 3.2  Sevo Des Iso Enf Hal IR Wavelengh

27. Vapor spectra overlap 3.2  Sevo Des Iso Enf Hal 2nd wavelength can quantify two agents 1st wavelength IR Wavelengh

29. IDENTIFIES AGENT by name

30. and detects mixtures

32. Mixed Agent Alarm

33. Other Monitor Anomalies

34. RGM hits the “rails” for agent if off scale

35. RGM hits the “rails” for oxygen, too < 21% I or E

36. Sevo Iso Des Best Vaporizer Order

37. Temporal Agent Mixing Isoflurane, then desflurane last 1 hr. Poor and poor. Isoflurane doesn’t clear from body. Eger EI, Anesthesiol Jan 1998. Philip JH, Gas Man 1996. Isoflurane doesn’t clear from circuit. Philip JH, Gas Man 1996.

38. Temporal Agent Mixing Another Example Sevoflurane induction followed by Low flow desflurane maintenance Sevoflurane leaves patient Sevoflurane doesn’t leave circuit Sevoflurane returns to patient Philip JH. Inspired Sevoflurane remains after switching to desflurane with 2 L/Min FGF. Proc. STA Annual Meeting, January 16, 1998.

39. Switch Graph 30 min Sevo N 2 O ------> Des Air Switch Marquette SAM

40. Philip JH. Inspired Sevoflurane remains after switching to desflurane with 2 L/Min FGF. Proc. STA Annual Meeting, January 16, 1998. Conc (% insp)4.41.00.50.250.1< 0.1 Time (min)0712285176 SEM (min)0113127

41. Mean of 5 patients 0 1 2 3 4 050100150 Sevo vap. on Inspired Sevoflurane % Time (minutes)

42. Semi-Log plot of Inspired Sevoflurane Concentration versus time (5 patients).01.1 1 10 050100150 Time (minutes) Inspired Sevoflurane Conc % Sevoflurane vaporizer on MAC 7 12 28 51 -7 0 4.5 76 2

43. Physical Gas Monitoring Limitations Sensitivity Specificity Precision Accuracy

44. Physical Gas Monitoring Limitations Sensitivity - how low it will measure Specificity - what won’t confuse it Precision - change it can detect Accuracy - the exact value it measures

45. Physical Gas Monitoring Limitations Sensitivity - usually easy Nitric Oxide 1ppm - hard Specificity - differentiate agents Support agent switch Precision - detect changes Need not be accurate 1.0 + 0.1% is not OK Accuracy - measure exact value

46. Physical Gas Monitoring Limitations Accuracy is rarely a problem. We seek changes and patterns, not values Thus precision, or resolution of reading, is the most important

47. Physiological Gas Monitoring Limitations The Continuum of V-Q mismatch Alveolar Dead Space Inhaled gas mixes with alveolar Shunt V/Q distribution

48. Clinical Gas Monitoring Limitations How to use the data The time course of change is key Need good trend display Why use the data Better control and better care Lower flow and cost for same care When to use the data Every General Anesthetic Soon in ICU for CO 2

49. Summary Vaporizers are mounted L->R: Sevo, Iso, Des Agent monitoring can be done in many ways BWH uses IR absorption and a few Ramon Spectrometers Don’t set the agent monitor to the wrong agent Don’t mix agents without a multi-agent monitor with graphs

50. Thank you