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Ambulatory care pharmacoeconomic evaluation of anesthesia in ambulatory surgery: comparison of desflurane to isoflurane and propofol |
Halberg D L, Russell W, Hatton R C, Segal R, Guyton T S, Paulu D A |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Desflurane, isoflurane and propofol for induction and maintenance of general anaesthesia in adults.
Type of intervention Treatment and anesthesia.
Economic study type Cost-effectiveness analysis.
Study population Patients aged 17 years or more undergoing surgical procedures of less than two hours' duration.
Setting Hospital (ambulatory surgery). The economic study was conducted in the United States.
Dates to which data relate The author did not provide time references for effectiveness data, resources used or the price year.
Source of effectiveness data Effectiveness data were derived from a single study.
Link between effectiveness and cost data Costing was undertaken prospectively on the same patient sample as that used in the clinical study.
Study sample There was no evidence of power calculations to determine the sample size. Adult patients (aged 17 or older) receiving either desflurane, isoflurane and propofol as a maintenance anaesthetic were eligible for the study. Patients maintained on more than one anaesthetic agent other than N?2O were excluded from the study.150 patients were enrolled and 43 were maintained on desflurane, 23 on isoflurane, and 84 on propofol.
Study design This was a single centre non-randomised controlled study.
Analysis of effectiveness The clinical study was based on intention to treat. Clinical effectiveness was measured in terms of time variations on patients' discharge from the ambulatory surgery. Two main time variables were calculated: end of anaesthesia to sit up, and end of anaesthesia to post-anaesthesia care unit (PACU) exit. Additionally eight other time variables were estimated: total anaesthesia, total surgery, incision to end of surgery, start surgery to incision, end of surgery to operating room (OR) exit, total PACU, sit up to PACU exit, and incision to PACU exit. The comparability of the three patient groups on different anaesthetic agents was verified and no statistically significant differences were found in the ANOVA analysis performed on age and weight, nor in the American Society of Anaesthesia classification score (measures differences in physical status of patients among the groups).
Effectiveness results The median values for the two main time variables were:
end of anaesthesia to sit up (V1), 55 mins. (isoflurane), 45 mins. (desflurane) and 40 mins. (propofol);
end of anaesthesia to PACU exit(V2), 110 mins. (isoflurane), 110 mins. (desflurane) and 90 mins. (propofol).
Differences between isoflurane and propofol were statistically significant: p=0.008 and p=0.024 for V1 and V2, respectively. Whereas only the difference between desflurane and propofol was significant, p=0.024 for V2. Of the 8 additional time variables calculated, only 4 were statistically significant: total anaesthesia, end of surgery to OR exit, total PACU time, and incision time to PACU exit.
Clinical conclusions Time savings achieved by desflurane in the early stages of recovery did not translate into accelerated discharge from PACU when compared with isoflurane and propofol. In fact, only propofol resulted in significant time savings over desflurane and Isoflurane.
Measure of benefits used in the economic analysis Given the statistically insignificant differences in effectiveness/clinical benefits between desflurane and isoflurane or propofol reported in the effectiveness analysis, the economic analysis was based on differences incosts only.
Direct costs Costs and quantities were not reported separately. Only hospital charges were considered in the analysis. Direct costs included drug costs for the maintenance anaesthetic, all drugs used during induction, all other drugs used during the maintenance of anaesthesia, and the cost of any drugs used in the PACU. Costs were not discounted since the analysis time horizon was shorter than one year.
Statistical analysis of costs One-way analysis of variance (ANOVA) with alpha equal to 0.05 was used to detect statistically significant differences in costs.
Sensitivity analysis No sensitivity analysis was performed on any of the parameters.
Estimated benefits used in the economic analysis Cost results Total average drug costs of anaesthesia maintenance were:
Desflurane, $53.30 (+/- $23.89), 95% CI: $46.16 - $60.44);
Isoflurane, $42.60 (+/- $20.03), 95% CI: $35.87 - $49.33);
Propofol, $59.66 (+/- $28.63), 95% CI: $53.53 - $65.78).
Of all the possible differences in cost among the three groups, the only one which achieved statistical significance was that between the costs of isoflurane and propofol. An annualised costs analysis of the expected differences when using desflurane instead of isoflurane in the total annual volume of patients, revealed an expected cost increment of approximately $4,800 to $6,500 per year.
Synthesis of costs and benefits Authors' conclusions Given the fact that no time savings were offered by desflurane, and the lack of evidence of improved patient outcomes, the additional cost of desflurane can not be justified.
CRD COMMENTARY - Selection of comparators The selection of comparators was clearly justified. Validity of estimate of measure of effectiveness As cknowledged by the authors, the difficulties in controlling for the various external factors which could have influenced the study's final outcomes obscures its validity. The results should be treated with caution. The authors pointed out the adequacy of the sample size, however there was no evidence that power calculations were used. Validity of estimate of costs Although pertinent comments regarding the various factors that could have biased the estimation of cost were reported, the authors did not attempt, through sensitivity analysis, to explore the uncertainty or range of variation that such factors could have imposed on cost. Other issues The authors made adequate comparisons of their results with those from previously published studies. The single centre nature of the study conveys a higher probability of the introduction of selection bias. Implications of the study Further investigation regarding the cost-effectiveness of desflurane for anaesthetic maintenance is needed. Bibliographic details Halberg D L, Russell W, Hatton R C, Segal R, Guyton T S, Paulu D A. Ambulatory care pharmacoeconomic evaluation of anesthesia in ambulatory surgery: comparison of desflurane to isoflurane and propofol. Pharmacy Practice Management Quarterly 1996; 16(2): 71-85 Indexing Status Subject indexing assigned by NLM MeSH Adult; Ambulatory Surgical Procedures /economics /methods; Anesthetics, Inhalation /economics /standards; Anesthetics, Intravenous /economics /standards; Economics, Pharmaceutical /standards; Florida; Hospital Bed Capacity, 500 and over; Hospitals, University; Humans; Isoflurane /analogs & Pharmacy and Therapeutics Committee; Propofol /economics /standards; derivatives /economics /standards AccessionNumber 21997007390 Date bibliographic record published 30/11/1999 Date abstract record published 30/11/1999 |
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