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Annual Scientific Meeting, Belfast; November 2000.

Intravenous versus inhalational anaesthesia

(Pro intravenous)

Gavin NC Kenny

Royal Infirmary, Glasgow G31 2ER, UK

Problems with Volatiles

Concern has been expressed over pollution of the operating environment with inhalational agents 1 and Nunn has concluded that if nitrous oxide were introduced as a new drug, there would be concern about its acceptability.2 It has also been suggested that the alertness of the anaesthetist may be decreased by inhalational anaesthetics.3 Many volatile anaesthetics are metabolised to fluoride ions and to trifluoroacetic acid with cross-reactivity reported between different agents [Dale 199]. Studies have shown increased production of fluoride ions occurs after the administration of sevoflurane4 and after the prolonged use of isoflurane.5

There are certain operative procedures such as laryngoscopy, bronchoscopy or thoracic surgery where it may be difficult or impossible to use inhalational anaesthesia and where total intravenous anaesthesia (TIVA) may be a more suitable option.6 In addition, the hypoxic pulmonary vasoconstriction reflex may be affected adversely by volatile compared with intravenous anaesthetics..7. Volatile agents are among those which must be avoided in patients who suffer from malignant hyperpyrexia and TIVA has been reported as a safe alternative.8 Postoperative nausea and vomiting has been consistently reported to occur more frequently after volatile anaesthesia compared with TIVA.9-15 The use of volatile agents to induce anaesthesia would be rejected in up to 24% of those who have experienced it16 and 78% experienced nausea in one study.13

 

Perceived Problems with TIVA

Propofol has a favourable pharmacokinetic profile for TIVA but the use of intravenous agents for maintenance of anaesthesia requires a different technique compared with volatile anaesthetics delivered via calibrated vaporisers. Several manual infusion schemes have been proposed to maintain a constant blood concentration during anaesthesia. However, such schemes cannot respond accurately to changing surgical and anaesthetic requirements. Target-controlled infusion (TCI) systems deliver variable infusion schemes based on a pharmacokinetic model which describes the elimination and redistribution of the drug. The predicted blood concentration of the drug can be changed rapidly in as simple a manner as that for volatile agents to suit varying levels of surgical stimulation and individual patient requirements.

 

Comparison of Measured and Predicted Blood Concentrations

Blood samples were obtained from patients during conditions of zero pump flow to compare measured with predicted blood propofol concentrations. Comparison of propofol concentrations predicted by the target controlled system with measured values showed an acceptable agreement between them for the population studied. While there are variations between the measured and predicted blood concentrations of propofol17, a comparison between the inspired partial pressure of volatile anaesthetics and the blood partial pressure demonstrates wide variation for these agents also.18 Even comparing the end-tidal value with the blood partial pressure shows a similar order of variation.19;20

 

Target-Controlled Infusions

The TCI systems allow the appropriate target blood for any individual patient and level of surgical stimulation to be achieved and maintained at any time. There is no single blood concentration of an intravenous anaesthetic agent which will result in satisfactory anaesthesia for all patients and all surgical conditions. It is necessary to titrate the target concentration against each patient's clinical response. Target-controlled systems provide the best estimate of the blood concentration at any time and permit the required target concentration to be achieved as accurately and a rapidly as possible.

 

References:

1. Halsey MJ: Occupational health and pollution from anaesthetics. A report of a seminar. Anaesthesia 1991; 46: 486-8

2. Nunn JF: Clinical aspects of the interaction between nitrous oxide and vitamin B12. British Journal of Anaesthesia 1987; 59: 3-13

3. Cook TL, Smith M, Starkweather JA, Winter PM, Eger EI: Behavioral effects of trace and subanesthetic halothane and nitrous oxide in man. Anesthesiology 1978; 49: 419-24

4. Smith I, Ding Y, White PF: Comparison of induction, maintenance, and recovery characteristics of sevoflurane-N2O and propofol-sevoflurane-N2O with propofol- isoflurane-N2O anesthesia. Anesthesia and Analgesia 1992; 74: 253-9

5. Breheny FX: Inorganic fluoride in prolonged isoflurane sedation. Anaesthesia 1992; 47: 32-3

6. Milligan KR, Coppel DL, Johnston JR, Cosgrove J: Propofol anesthesia for major thoracic surgery. Journal of Cardiothoracic Anesthesia 1990; 4: 323-5

7. Spies C, Zaune U, Pauli MH, Boeden G, Martin E: A comparison of enflurane and propofol in thoracic surgery. Anaesthesist 1991; 40: 14-8

8. Cartwright DP: Propofol in patients susceptible to malignant hyperpyrexia. Anaesthesia 1989; 44: 173-

9. Raftery S, Sherry E: Total intravenous anaesthesia with propofol and alfentanil protects against postoperative nausea and vomiting. Canadian Journal of Anaesthesia 1992; 39: 37-40

10. Borgeat A, Wilder Smith OH, Wilder Smith CH, Forni M, Suter PM: Adjuvant propofol for refractory cisplatin-associated nausea and vomiting (letter). Lancet 1992; 340: 679-80

11. Borgeat A, Wilder Smith OH, Saiah M, Rifat K: Subhypnotic doses of propofol possess direct antiemetic properties. Anesthesia and Analgesia 1992; 74: 539-41

12. Smith I, Thwaites AJ: Target-controlled propofol vs. sevoflurane: a double-blind, randomised comparison in day-case anaesthesia. Anaesthesia 1999; 54: 745-52

13. Philip BK, Lombard LL, Roaf ER, Drager LR, Calalang I, Philip JH: Comparison of vital capacity induction with sevoflurane to intravenous induction with propofol for adult ambulatory anesthesia. Anesthesia and Analgesia 1999; 89: 623-7

14. Weir PM, Munro HM, Reynolds PI, Lewis IH, Wilton NC: Propofol infusion and the incidence of emesis in pediatric outpatient strabismus surgery. Anesthesia and Analgesia 1993; 76: 760-4

15. Tang J, Chen L, White PF, Watcha MF, Wender RH, Naruse R, Kariger R, Sloninsky A: Recovery profile, costs, and patient satisfaction with propofol and sevoflurane for fast-track office-based anesthesia. Anesthesiology 1999; 91: 253-61

16. Thwaites AJ, Edmends S, Smith I: Inhalation induction with sevoflurane: a double-blind comparison with propofol [see comments]. British Journal of Anaesthesia 1997; 78: 356-61

17. White M, Kenny GN: Intravenous propofol anaesthesia using a computerised infusion system. Anaesthesia 1990; 45: 204-9

18. Frei FJ, Zbinden AM, Thomson DA, Rieder HU: Is the end-tidal partial pressure of isoflurane a good predictor of its arterial partial pressure? British Journal of Anaesthesia 1991; 66: 331-9

19. Carpenter RL, Eger EI: Alveolar-to-arterial-to-venous anesthetic partial pressure differences in humans. Anesthesiology 1989; 70: 630-5

20. Dwyer RC, Fee JP, Howard PJ, Clarke RS: Arterial washin of halothane and isoflurane in young and elderly adult patients. British Journal of Anaesthesia 1991; 66: 572-9

 

TIVA or Not TIVA

Dr Terry McMurray MD, MA, MEd

The debate between the protagonists for intravenous or inhalational anaesthetic techniques continues to generate a lot of "hot air" but this presentation will seek to illuminate issues, relevant to practising anaesthetists.

While most analyses seek to focus mainly on patient factors, opportunity costs, health and safety issues and the anaesthetists' responsibilities to society must not be ignored. Consequently, this presentation will analyse the real costs and benefits associated with both approaches and in particular to identify hidden costs that many enthusiasts have sought to ignore or dismiss.

 

Costs versus Benefits of Intravenous / Inhaled Anaesthesia

(Pro Inhalation)

 

Ian Smith

Department of Anaesthesia

Keele University, North Staffordshire Hospital, Stoke-on-Trent

The direct costs of intravenous anaesthetics are generally higher than those of inhaled anaesthesia, especially when the wastage of the latter is minimised by low fresh gas flows. Since the advent of generic propofol, the difference has reduced somewhat (although the price of isoflurane has also decreased sharply), but remifentanil and propofol by TCI still involve the use of more expensive branded products.

In compensation for these higher direct costs, it has often been claimed that iv anaesthesia reduces indirect costs by way of improved outcome, reduced PONV and improved patient satisfaction. The subject of differential equipment costs is sometimes also raised. Determining the true cost of anaesthesia is a complex exercise and one which will yield different results depending on how staff are employed.

To put the issue into context, anaesthetic drugs comprise less than 5% of the hospital pharmacy budget and about 0.25% of the overall budget [1]. They account for approximately 3–4% of the cost of a surgical procedure [2, 3]. In contrast, surgical disposables for a common day case procedure, such as laparoscopic sterilisation, cost 4.5 times as much as anaesthetic drugs [3]. Nevertheless, anaesthesia departments are under enormous pressure to control their budgets. Elimination of drug waste is always beneficial, since it saves money without affecting patient outcome. Reducing waste is easier with inhaled anaesthetics than with iv drugs. Using a cheaper drug appears superficially attractive and will reduce costs provided that patient outcome is not affected. This is rarely the case, but how much do the altered outcomes increase indirect costs?

A commonly-quoted study is that of Rowe, who compared five anaesthetic techniques based on propofol or enflurane [3]. He noted that the technique with the lowest direct costs became the most expensive when "all costs" were included. This turnaround was due to the costs of surgical disposables and increased time in the operating room, neither of which may have been consequential on the choice of anaesthetic! More fundamentally, the cost of operating room time was calculated by multiplying average costs by time. This is a common error and what is important is the marginal cost of spending more or less time in the theatre [4]. How time relates to cost depends on how staff are paid. For full time staff on a salary, changes in time worked have no effect on costs until enough time is aggregated that one fewer person needs to be employed [5]. Money may be saved with part-time, hourly paid staff, but even here it has been argued that the timekeeping system is insensitive enough to detect small increments of just a few minutes [6, 7]. In addition, nurses in the operating or recovery rooms often perform tasks in parallel; a reduction in recovery time (or time spent treating PONV) may not save time overall if instruments have to be put away and records and paperwork need completing.

It has also been suggested that faster recovery will permit additional cases to be operated on or prevent congestion in the recovery room. In fact, it has been shown that eliminating induction and emergence time would not permit an additional case to be reliably completed without overrunning [8]. In addition, most recovery rooms typically have more than the theoretical minimum staff required [9]. Even if staff costs are cut, the savings may not necessarily be credited to the anaesthesia department’s budget!

How expensive is PONV? Some disposable items will be used and have been costed at $0.85–$2.503 per patient [10, 11]. Some, but not all patients will require drug therapy. With PONV at levels as high as 30%, drugs and disposables combined will add less than £1 per case. The other indirect costs are problematic, as previously mentioned. Delayed recovery may not increase costs, although admission probably will. Figures on unplanned admissions were not included in a large meta-analysis comparing PONV after propofol and inhaled agents,[12] perhaps since such data are lacking. Although PONV is unpleasant, there is little evidence that antiemetic prophylaxis improves patient satisfaction [13] and some to suggest that it does not [14]. Similarly, any dissatisfaction with inhalation anaesthesia does not appear to correlate with the occurrence of PONV [15]. Perhaps inhalation anaesthesia is not associated with so many indirect costs after all!

 

References:

1. Hawkes C, Miller D, Martineau R, Hull K, Hopkins H, Tierney M. Evaluation of cost minimization strategies of anaesthetic drugs in a tertiary care hospital. Canadian Journal of Anaesthesia 1994;41:894–901.

2. Macario A, Vitez TS, Dunn B, McDonald T. Where are the costs in perioperative care? Analysis of hospital costs and charges for inpatient surgical care. Anesthesiology 1995;83:1138–44.

3. Rowe WL. Economics and anaesthesia. Anaesthesia 1998;53:782–8.

4. Sperry RJ. Principles of economic analysis. Anesthesiology 1997;86:1197–205.

5. Dexter F, Macario A, Manberg PJ, Lubarsky DA. Computer simulation to determine how rapid anesthetic recovery protocols to decrease the time for emergence or increase the Phase I Postanesthesia care unit bypass rate affect staffing of an ambulatory surgery center. Anesthesia and Analgesia 1999;88:1053–63.

6. Lubarsky DA. The successful implementation of pharmaceutical practice guidelines? Far from convincing!—In reply (letter). Anesthesiology 1997;87:1584.

7. Lubarsky DA. Pharmaceutical practice guidelines: Do they actually cost money?—In reply (letter). Anesthesiology 1998;89:270–1.

8. Dexter F, Coffin S, Tinker JH. Decreases in anesthesia-controlled time cannot permit one additional surgical operation to be reliably scheduled during the workday. Anesthesia and Analgesia 1995;81:1263–8.

9. Marais ML, Maher MW, Wetchler BV, Korttila K, Apfelbaum JL. Reduced demands on recovery room resources with propofol (Diprivan) compared to thiopental-isoflurane. Anesthesiology Review 1989;XVI:29–40.

10. Carroll NV, Miederhoff P, Cox FM, Hirsch JD. Costs incurred by outpatient surgical centers in managing postoperative nausea and vomiting. Journal of Clinical Anesthesia 1994;6:364–9.

11. Tang J, Wang B, White PF, Watcha MF, Qi J, Wender RH. The effect of timing of ondansetron administration on its efficacy, cost-effectiveness, and cost-benefit as a prophylactic antiemetic in the ambulatory setting. Anesthesia and Analgesia 1998;86:274–82.

12. Sneyd JR, Carr A, Byrom WD, Bilski AJT. A meta-analysis of nausea and vomiting following maintenance of anaesthesia with propofol or inhalational agents. European Journal of Anaesthesiology 1998;15:433–45.

13. Fisher DM. The "big little problem" of postoperative nausea and vomiting. Do we know the answer yet? (Editorial). Anesthesiology 1997;87:1271–3.

14. Scuderi PE, James RL, Harris L, Mims GR, III. Antiemetic prophylaxis does not improve outcomes after outpatient surgery when compared to symptomatic treatment. Anesthesiology 1999;90:360–71.

15. Smith I. Costs of sevoflurane and propofol anaesthesia—in reply (letter). British Journal of Anaesthesia 2000;84:418.

 

 

Intravenous or inhalational anaesthesia:

Costs v. benefits: a pharmacoeconomic view

J M Murray

Department of Anaesthetics

The Queen’s University of Belfast

Concerns about soaring health care costs have generated considerable debate over which methods to contain health care costs are best.1 In this new health care environment, clinical departments and services with high resource utilization, such as operating theatres, are no longer considered "profit centres" for hospitals, but "cost centres."2 The challenge now is to maintain the same high quality of care while utilizing fewer resources.3-5 Clinical practice patterns in anaesthesia, including work-force modifications, are now being examined to determine if they are associated with the best outcome at the most reasonable cost a concept termed "value-based anaesthesia care." 6 Increased value can be obtained by achieving the same outcome at a lower cost, or by achieving, a better outcome at a higher total cost.6

If anaesthetists do not become involved in the process of determining the value obtained for the resources used, the end result may be that non-medical personnel will dictate changes in organizational structure and in the utilization of anaesthetics and other pharmaceutical products, equipment, and supplies in anaesthesia practice.4, 7-9

Like all other specialists, anaesthetists need to examine their clinical practices carefully to reduce excessive costs and waste without compromising patient care or safety.7 While the costs of anaesthetic drugs account for only a small fraction of total health care expenditures, they are highly visible costs, (so-called "low-hanging fruit"), and therefore easy for administrators to scrutinize.' Although cost savings in an individual case may be small, the total savings may be impressive because of the large number of cases performed.3 It is becoming increasingly apparent that better scheduling of cases,10 more efficient processing of patients in the recovery room to optimise admission rates,11 and reduced wastage of anaesthetic and surgical supplies12 will result in greater savings than will reduction in anaesthetic related drug costs.1 Nevertheless, it is still important for anaesthetists to be involved in the ongoing effort to reduce medical costs without compromising the quality of patient care. Indeed, quality patient care and fiscally sound decision-making are not necessarily mutually exclusive.

Simple and effective cost containment measures that all anaesthetists can implement include the use of low fresh gas flow rates with inhalation agents and keeping sterile packages and drug ampoules sealed unless the contents will actually be used. The choice of an anaesthetic agent for routine use will depend not only on its demonstrated efficacy and side effect profile, but also on economic factors. It is therefore important to evaluate the pharmacoeconomics of these newer drugs and carefully assess all aassociated costs and benefits for subsets of patients undergoing different types of surgical procedures. Such evaluations should also include patient preferences. Undue emphasis on the acquisition costs of drugs should be avoided insofar as possible since it may lead to blanket bans on the use of new drugs because of their higher costs instead of permitting doctors to individualize therapy according, to their clinical experience and the perceived needs of a given patient. Institutional and individual variations in clinical practices, associated costs, and outcomes may alter the conclusions about the acceptability and pharmacoeconomic evaluation of a particular drug or technique. This presentation will examine the rational basis for incorporating cost considerations into the decision-making process regarding the drugs and techniques used in anaesthesia. 7

 

Acquisition cost of anaesthetic induction drugs

IV DRUGS

Dosage Cost Cost/dose Wastage

Thiopentone

4.0

0.001

0.3

0.3

Methohexitone

2.0

0.002

0.96

3.0

Etomidate

0.2

0.93

9.5

5.7

Propofol

2.0

0.034

4.3

2.6

INHALED

       

Sevoflurane

5%

0.2

1.46

0

N2O

67%

0.1

0.04

0

 

Costs of maintenance of anaesthesia

Inhaled

£/bottle

Cost (£/ml)

£/L vap

O2:N2O

Cost (£/hr)

Halothane

9.9

0.04

0.17

1:2

0.28

Enflurane

81

0.3

1.6

1:2

4.9

Isoflurane

52

0.53

2.6

1:2

4.4

Desflurane

50

0.2

0.97

1:2

5.7

Sevoflurane

120

0.46

2.6

1:2

5.8

IV

         

Propofol

 

3.90/amp

 

1:2

20.2

 

References:

1. Vitez T. Principles of cost analysis .J Clin Anesth 1994;6:357-363

2. Rutter TW, Brown ACD. Contemporary operating room management. In Lake CL (ed). Advances in Anesthesia. Vol 11, St Louis, CV Mosby, 1994, pp 173-214

3. White PF, White LD. Cost containment in the operating room: who is responsible? J Clin Anaesth 1994; 6: 351-356

4. Eddy DM. Health system reform: will controlling costs require rationing service? JAMA 1994; 272: 324-328

5. Iglehart JK. Health care reform: The role of physicians. N Engl J Med 1994;330:728-731.

6. Orkin FK. Moving towards value based anesthesia care. J Clin Anesth 1993;5:91-98.

7. Lanier WL, Warner MA. New frontiers in anesthesia research. Assessing the impact of practice patterns on outcome, health care delivery and cost. Anesthesiology 1993;78:1001-1004.

8. Tuman KJ, Ivankovich AD. High-cost high-tech medicine: Are we getting our money's worth? J Clin Anesth 1993;5:168-177.

9. Fisher DM. Right, wrong and surrogate endpoints (reply). Anesthesiology 1995;82:1085.

10. Mazzei WJ. Operating room start times and turnover times in a university hospital. J Clin Anesth 1994;6:405-408.

11. Dexter T, Tinker JH. Analysis of strategies to decrease postanesthetic care unit costs. Anesthesiology 1995; 82:94-101.

12. Rosenblatt W-H, Silverman DG. Cost-effective use of operating room supplies based on REMEDY database of recovered unused materials. J Clin Anesth 1994;6:400-404.

 

Page last revised: January 29, 2012.

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