How Technology Will Secure the Future of Inhalation Anesthesia. How Technology Will Secure the Future of Inhalation Anesthesia. Jan Hendrickx, MD, PhD

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1 How Technology Will Secure the Future of Inhalation Anesthesia Jan Hendrickx, MD, PhD Staff Anesthesiologist, OLV Hospital, Aalst, Belgium Consulting Assistant Professor (alumni), Stanford University, Stanford, CA Immediate Past Chair, ESA Scientific Subcommittee on Equipment, Monitoring, and Ultrasound How Technology Will Secure the Future of Inhalation Anesthesia Jan Hendrickx, MD, PhD Staff Anesthesiologist, OLV Hospital, Aalst, Belgium Consulting Assistant Professor (alumni), Stanford University, Stanford, CA Immediate Past Chair, ESA Scientific Subcommittee on Equipment, Monitoring, and Ultrasound I have received - lecture support - travel reimbursements - equipment loans - consulting fees - meeting organizational support (NAVAt) from basically all companies involved with inhaled agent delivery: AbbVie, Acertys, Air Liquide, Allied healthcare, Armstrong Medical, Baxter, Draeger, GE, Hospithera, Heinen und Lowenstein, Intersurgical, Maquet, MDMS, MEDEC, Micropore, Molecular, NWS, Philips, Quantium Medical 1

2 Note: this lecture may contain more examples of one anesthesia machine than another. This by no means reflects any personal preference - the choices have been made purely for didactical reasons, and also reflect my current research topics. How Technology Will Secure the Future of Inhalation Anesthesia Target controlled low flow anesthesia A means to visualize drug interactions and guide depth 2

Aisys Zeus FLOW-i SmartPilot, Navigator EEG derived? Both?

drug interactions and guide depth (seeing context sensitive

.. Closest to conventional USA machine: Aisys upgraded for

and concentrations EtO2 2 and Measure Et Agent patient F A

3 Aisys Zeus FLOW-i SmartPilot, Navigator EEG derived? Both? Target controlled low flow anesthesia A means to visualize drug interactions and guide depth (seeing context sensitive halftimes at work) The players (others to follow)... Closest to conventional USA machine: Aisys upgraded for target control Adjust vaporizer % FGF 4 Adjust FreshGas flow and concentrations EtO2 2 and Measure Et Agent patient F A Apply algorithm Compare and 3 Calculate Set F 1 Set Et Targets A t O 2 FGF F A t sevo 3

4 Zeus (Draeger) - carrier gas and agent uncoupled - liquid injection Instantaneous mixing Also is ventilator FLOW-i (Maquet) The heart of the system: carrier gas delivery systems act as ventilator 4

5 Injector Volume reflector: physically open, functionally closed How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control 3. Why prediction displays 4. The smartest pilot and the really smartest pilot 5

6 How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control 3. Why prediction displays 4. The smartest pilot and the really smartest pilot Low flow anesthesia makes sense - less waste - less pollution - less costs - heat & humidity Sevo usage 5-6 min (F A = 1.8%) 3 25 ml liquid sevoflurane FGF (L/min) The GAEQ of sevo with the ADU: De Cooman S, data on file Aisys: De Cang, ESA 214 Annual meeting, abstract 3AP1-7 FLOW-i: Carette R,et al. Maquet ESA grant 214, in writing 6

7 How low can you go? Minimum we need? O 2 uptake 18 (37) ml/min N 2 O uptake 2 1 ml/min (1' 1h) Desflurane (6% F A, 1h) 12.5 ml liquid 1.3 ml by patient 2.2 ml circuit + lungs Sevoflurane (2% F A, 1h) 7. ml liquid 6. ml by patient 1. ml circuit + lungs Robinson G et al. J Appl Physiol 24;97:96-66 De Cooman S et al. BMC Res Notes 214 July 23:7:469 Severinghaus J. J Clin Invest 1954;33: Hendrickx J et al. Anest Analg 1997;84:413-8 Hendrickx J et al. Br J Anaesth 1998;81: Lowest you can go Sevoflurane usage (ml) Fresh gas flow (L/min) Aisys sevoflurane, O 2 /air 1 h F A = 2% De Cang M, ESA 214, 3AP1-7 Hendrickx J et al. Br J Anaesth 1998;81:495 7

8 Sevoflurane usage (ml) Aisys 5 ml/min FLOW-i 3 ml/min Zeus closed (O 2 /air) Fresh gas flow (L/min) De Cang M, ESA 214, 3AP1-7 Carette R. J Clin Mon Comp 215 June 14 De Cooman S et al. BMC Res Notes 214 July 23:7:469 Sevoflurane usage (ml) Aisys 5 ml/min FLOW-i 3 ml/min Zeus closed (O 2 /air) Fresh gas flow (L/min) De Cang M, ESA 214, 3AP1-7 Carette R. J Clin Mon Comp 215 June 14 De Cooman S et al. BMC Res Notes 214 July 23:7:469 Low flow anesthesia makes sense - less waste - less pollution - less costs - heat & humidity 8

9 All agents impede infrared radiation to outer space (GWP) Global effect cars = 1 coal fired power plant = 1 million passenger Sulbaek Andersen MP. Anesth Analg 212;114:181-5 All agents impede infrared radiation to outer space (GWP) Global effect cars = 1 coal fired power plant = 1 million passenger Low flow = waste reduction by 9% Feldman J. (212) Anesth Analg 114: Sulbaek Andersen MP. Anesth Analg 212;114:181-5 Low flow anesthesia makes sense - less waste - less pollution - less costs - heat & humidity complex combined cost agent + CO 2 absorber does continue to decrease with FGF 9

10 Low flow anesthesia makes sense filter - less waste - less pollution - less costs - heat & humidity CO 2 - CO 2 absorbent reaction = exothermic, H 2 O producing = no need for HME, only Anthony Wilkes Low flow anesthesia makes sense - less waste - less pollution - less costs - heat & humidity Then why - the hesitancy to use low flow fresh gas flows (FGF)? - the intuitive use of L/min FGF? - the ill defined fear of FGF << 1L/min? Teaching alone does not work... Baseline After being taught to use lower FGF And 6 months later... Body SC, Fanikos J, DePeiro D, Philip JH, Segal BS. Anesthesiology 1999;9:

11 Compound A? Hard to believe this continues to be an issue Sevoflurane used routinely with closed-circuit anesthesia If medicolegal issue: use Amsorb Plus, SpiraLith, LithoLyme The reasons for the hesitancy to use FGF << 1L/min explain why we need target control delivery of agents and O 2 How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - LFA more convenient, less distraction - conventional LFA teaching = inconsistent use - safety agent O 2 3. Why prediction displays (drug interactions, times) 4. The smartest pilot and the really smartest pilot 11

12 Clinical Example How to adjust vaporizer setting (F D ) to maintain sevoflurane F A at 1.3% with FGF from.3 to 8 L/min O 2 /N 2 O with conventional machine (ADU )? Hendrickx J, Van Zundert A, et al. Anesthesiology 1998; 89 : A518 Vaporizer setting (= F D ) % sevoflurane n=8 per FGF group only average F D per FGF group presented start at maximum F D = 8% sevoflurane 8 L/min Time (min) Anesthesiology 1998; 89 : A518 F D (%) L/min 8 L/min Time (min) Anesthesiology 1998; 89 : A518 12

13 F D (%) L/min 1 L/min 8 L/min Time (min) Anesthesiology 1998; 89 : A518 F D (%) L/min.5 L/min 1 L/min 8 L/min Time (min) Anesthesiology 1998; 89 : A518 F D (%) 8 Lower FGF = higher F D L/min.5 L/min 1 L/min 8 L/min Time (min) Anesthesiology 1998; 89 : A518 13

14 "High" FGF: FGF > MV Ventilation 5L/min Sevo F D = 2% O 2 2 L/min N 2 O 4 L/min F I F A Bellows fill with fresh gas only Ventilation 5L/min Sevo F D = 2% O 2 2 L/min N 2 O 4 L/min F I F A 14

15 Ventilation 5L/min Sevo F D = 2% O 2 2 L/min N 2 O 4 L/min F I = 2% F A F I = F D «control» "Low" FGF: FGF < MV Ventilation 5L/min Sevo F D = 2% O 2.3 L/min N 2 O.4 L/min F I F A 15

16 Ventilation 5L/min Bellows fills with fresh gas PLUS exhaled gas Sevo F D = 2% O 2.3 L/min N 2 O.4 L/min F A Rebreathing of exhaled gas with vapor concentration < F D causes F I and thus F A Ventilation 5L/min Sevo F D = 2% O 2.3 L/min N 2 O.4 L/min F I < 2% F A To maintain same F I and thus F A, F D has to be increased. Ventilation 5L/min Rx Sevo F D = 3% O 2.3 L/min N 2 O.4 L/min F I = 2% F A 16

17 A difference has developed between F I and F D. Ventilation 5L/min Sevo F D = 3% O 2 2 L/min N 2 O 4 L/min F I = 2% F A F D > F I «loss of control» This "dilutional" effect becomes more prominent with FGF < L/min With lower FGF, we have the impression to lose control" This is why we intuitively use FGF = L/min: F D still matches F I FGF << 1 L/min not frequently used because - more vaporizer adjustments needed 17

18 F D (%) 8 FGF,3L/min (% sevoflurane) FGF,5L/min FGF 1L/min FGF 8L/min Time (min) Anesthesiology 1998; 89 : A518 F D (%) 8 FGF,3L/min (% sevoflurane) FGF,5L/min FGF 1L/min FGF 8L/min Time (min) Anesthesiology 1998; 89 : A518 FGF << 1 L/min not frequently used because - more vaporizer adjustments needed - it becomes harder to predict F D in the individual patient 18

19 ... F D variability increases with lower FGF % sevo vaporizer 8 6 FGF (L/min) Time (min) A&A1999; 88:S344;Anesthesiology 1998; 3A, A518, 1998 FGF << 1 L/min not frequently used because - more vaporizer adjustments needed - it becomes harder to predict F D in the individual patient - choice of carrier gas effect F D more pronounced Hendrickx et al. Anesthesiology 22;97:4-4 Clinical implication: more attention needed potentially more distractive especially right after induction over- and under- dosing 19

20 Even with high flows we under-dose many of our patients... Prospective study Target:.7 MAC 15.2% was underdosed 2

Obvious solution: target F A Let machine

1.1.1 5 1 15 Time (min) Liquid injection rate

21 Obvious solution: target F A Let machine manage FGF and F D to get target F A Target control makes the use of low flow very simple, so we now use it routinely Zeus FGF Time (min) Liquid injection rate Time (min) Personal observations 21

22 Rate of rise of end-expired % (F A ) End-expired sevoflurane (%) Aisys Zeus FLOW-i Time (min) Aisys De Cang, ESA 214 abstract; unpublished data ( - 5 min) Zeus De Cooman, BMC Res Notes 214 July 23;7:469 FLOW-i Unpublished data How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - teaching alone insufficient - more convenient, less distraction consistent use - safety agent (over and under dosing) O 2 3. Why prediction displays (drug interactions, times) 4. The smartest pilot and the really smartest pilot How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - teaching alone insufficient - more convenient, less distraction consistent use - safety agent (over and under dosing) O 2 3. Why prediction displays (drug interactions, times) 4. The smartest pilot and the really smartest pilot 22

23 Movie Ventilation 5L/min Air O 2 N 2 O F I F A Ventilation 5L/min Air O 2 N 2 O F I F A Ensuring 21 % O 2 at the common gas outlet does not ensure F I O 2 = 21%! 23

24 Ventilation 5L/min Air O 2 N 2 O F I F A Anesthesia circle breathing system alters relationship between delivered and inspired O 2 % if FGF < MV: rebreathing kinetics! Protection Against Accidental Delivery of Hypoxic Gas Mixtures ANSI Standard The anesthesia workstation shall be provided with - a device to protect against an operator selected delivery - of a O 2 /N 2 O mixture - having < 21 % O 2 in the fresh gas or in the inspired gas Air O 2 N 2 O Hypoxic Guard 24

Examples of hypoxic guard systems Ohmeda Link 25 a chain that links N 2 O and O 2 mechanical Dräger S-ORC Sensitive Oxygen Ratio Controller pneumatical - mechanical www.navat.

25 Examples of hypoxic guard systems Ohmeda Link 25 a chain that links N 2 O and O 2 mechanical Dräger S-ORC Sensitive Oxygen Ratio Controller pneumatical - mechanical F D O 2 (%) S-ORC limits = lowest possible F D O 2 % the S-ORC allows us to use with a certain FGF Total O 2 /N 2 O FGF (L/min) S-ORC limits = lowest possible F D O 2 % the S-ORC allows us to use with a certain FGF F D O 2 5 (%) Always > 25 % O 4 2 J! Total O 2 /N 2 O FGF (L/min) 25

26 F D O 2 (%) S-ORC limits = lowest possible F D O 2 % the S-ORC allows us to use with a certain FGF Always > 25 ml/min % J 2! (= VO 2 of awake adult) Total O 2 /N 2 O FGF (L/min) F D O 2 (%) But do these F D O 2 limits ensure F I O 2 21 %? De Cooman S, Schollaert C, Hendrickx JF, et al. J Clin Mon Comput, 214, Oct Total O 2 /N 2 O FGF (L/min) O 2 % These hypoxic guard limits did ensure F I O 2 21 % Total O 2 /N 2 O FGF (L/min) F D O 2 F I O 2 26

27 O 2 % but these did NOT: this is NOT a safe zone! F I O 2 < 21% Total O 2 /N 2 O FGF (L/min) F D O 2 F I O 2 % of patients with F I O 2 < 21 % 1 % of patients Total O 2 /N 2 O FGF (L/min) 4 Time after which F I O 2 < 21 % (baseline = 25%) Time (min) Total O 2 /N 2 O FGF (L/min) 27

28 In some patients < 6 seconds! 4 Time (min) Total O 2 /N 2 O FGF (L/min) Machine standards are outdated: - effect of rebreathing not taken into account - no requirements for O 2 /air mixtures Machine standards are outdated: - effect of rebreathing not taken into account - no requirements for O 2 /air mixtures Worse still: hypoxic guards perform worst with FGF many of us are comfortable working with:1-2 L/min! 28

29 Solution? Solution = target F I O 2 or F A O 2 directly Aisys Zeus FLOW-i Solution = target F I O 2 or F A O 2 directly Aisys Zeus FLOW-i 29

30 O 2 Guard need back-up = override inadequate settings if F I O 2 < 21% O 2 Guard need back-up = override inadequate settings if F I O 2 < 21% O 2 Guard need back-up = override inadequate settings if F I O 2 < 21% 3

31 How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - LFA more convenient, less distraction - conventional LFA teaching = inconsistent use - safety agent O 2 Solved. We use it in every OR How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - LFA more convenient, less distraction - conventional LFA teaching = inconsistent use - safety agent O 2 Solved. We use it in every OR How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - LFA more convenient, less distraction - conventional LFA teaching = inconsistent use - safety agent O 2 3. Why prediction displays (drug interactions, times) 31

Why prediction displays (drug interactions, times) We use it every

32 How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - LFA more convenient, less distraction - conventional LFA teaching = inconsistent use - safety agent O 2 3. Why prediction displays (drug interactions, times) We use it every day in 1 OR. Work in progress. This is the future. Target controlled low flow: what target sevo to select? You have to pick a number 32

33 MACawake MAC MACBAR 33

will help ensure a fast emergence, as guided by the prediction. Drug combinations possible.

34 Propofol Sevoflurane MACawake 5 MACawake 9 MAC5 MAC9 Opioid Time Depending on which drug is eliminated faster, you might want to choose more hypnotic or opioid to maintain a certain anesthetic depth - this will help ensure a fast emergence, as guided by the prediction. Drug combinations possible. The orange circle/black circle/white circle navigates you. Propofol Sevoflurane MACawake 5 MACawake 9 MAC5 MAC9 Opioid Time 34

Optimizing desflurane in terms of drug interactions/contextsensitive t 1/2 guided by SmartPilot FA desflurane (%) 1 8 6 4 2 Desflurane usage for same depth (NSRI = 5) - 53% ` 2 4 6 8 1 Ce

35 Optimizing desflurane in terms of drug interactions/contextsensitive t 1/2 guided by SmartPilot FA desflurane (%) Desflurane usage for same depth (NSRI = 5) - 53% ` Ce remifentanil (ng/ml) Carette R. Submitted, ESA 216 Input info readily available: - infusions: from injector, pump - bolus: enter yourself or via bar codes in future - "freebee": no need for electrodes Jelacic S et al. Anesth Analg 215;121:41-21 Road to more consistent and predictable wake-up Vastly under-used and under-appreciated Johnson KB et al. Anesth Analg 21:111:

36 Technology Has Secured the Future of Inhalation Anesthesia We need to embrace it and implement it Don't let technology pass you by Smartest Pilot Enter - patient covariates - surgeon's covariates (procedure, duration) - costs of drugs, CO 2 absorbent, other - adjust anticipated wake-up time Machine will steer drug adminstration Margin of error for inhaled agents: can be washed-out Smartest Pilot Enter - patient covariates - surgeon's covariates (procedure, duration) - costs of drugs, CO 2 absorbent, other - adjust anticipated wake-up time Machine will steer drug adminstration Margin of error for inhaled agents: can be washed-out 36

37 Really Smartest Pilot Us! Biological variability Equipment failure Still: "One of the most important reasons we need anesthesiologists (at least for now) is that only anesthesiologists can determine what drugs and especially what combination of drugs (and their proportioning) will be used in a specific patient. This is something that can (will) be taken over by smart equipment, but not quite yet..." Andre De Wolf Northwestern University Chicago, IL, USA How Technology Will Secure the Future of Inhalation Anesthesia 1. Why low flow (LFA) 2. Why target control - LFA more convenient, less distraction - conventional LFA teaching = inconsistent use - safety agent O 2 3. Why prediction displays (drug interactions, times) 4. The smartest pilot and the really smartest pilot How Technology Will Secure the Future of Inhalation Anesthesia Jan Hendrickx, MD, PhD Staff Anesthesiologist, OLV Hospital, Aalst, Belgium Consulting Assistant Professor (alumni), Stanford University, Stanford, CA Immediate Past Chair, ESA Scientific Subcommittee on Equipment, Monitoring, and Ultrasound 37

Understanding Rebreathing Kinetics

Understanding Rebreathing Kinetics James H Philip, ME(E), MD, CCE Anesthesiologist and Director Bioengineering, Brigham and Women's Hospital Professor of Anaesthesia, Harvard Medical School Boston Massachusetts