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Vomiting after strabismus surgery in children: ondansetron vs propofol |
Splinter W M, Rhine E J, Roberts D J |
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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 Two different anaesthetic regimens, intended to reduce the rate of post-operative emesis, namely inhaled halothane combined with oral ondansetron, or propofol plus intra venous lidocaine.
Economic study type Cost-effectiveness analysis.
Study population The study population consisted of children between the ages of 2 and 14 undergoing elective strabismus surgery.
Setting The study setting was hospital. The economic analysis was conducted in Ottawa, Ontario, Canada.
Dates to which data relate Dates for collection of effectiveness and resource data do not appear to have been provided. The base price year used in the analysis was not stated.
Source of effectiveness data Effectiveness data were derived from a single study
Link between effectiveness and cost data Resource data were collected prospectively using the same patient sample as in the effectiveness analysis.
Study sample Power calculations were used prospectively to determine the sample size. (165 patients per group was estimated based on a 15% difference in the incidence of vomiting (alpha = 0.05, power 80%)). 330 patients were included in the study. The method of sample selection was not stated. The patient group selected appears to have been appropriate for this study. There were 144 patients in Group 0 and 156 patients in group P. 30 patients (9%) were excluded from the analysis. 16 patients assigned to Group O ultimately required anaesthesia to be induced by propofol, 7 were excluded as ASA physical class was 3, 4 were excluded for protocol violations, and 3 because parents decided to withdraw from the study.
Study design The study was a single blind, stratified, randomised controlled trial carried out in a single centre. Patients were placed in blocks of 10 and stratified based on the number of muscles to be operated on and whether pre-medication was required. Patients were then randomised between the two groups using a random numbers table. Patients were followed up for a period of 24 hours after surgery. There was no loss to follow up.
Analysis of effectiveness The analysis of effectiveness was based on intention to treat. The primary health outcome used was the incidence of post-operative vomiting in the two groups. At baseline analysis both groups were similar in demographic and clinical characteristics.
Effectiveness results The rates of post-operative vomiting in the two groups were similar, with a rate of 27% in Group O compared with 26% in Group P. In all patients the rate of vomiting was significantly lower in those patients who had only one muscle operated on; 21% compared with 45% for 3 or 4 muscles (p<0.02).
Clinical conclusions The authors concluded that the study demonstrated that ondansetron and propofol were of similar effect in controlling post-operative emesis.
Measure of benefits used in the economic analysis Since the clinical analysis had shown no difference in clinical effectiveness between the two interventions, the economic analysis was based on the difference in costs only (cost-minimisation).
Direct costs The costs of anaesthetic drugs and administration tubing were included in the analysis. Costs of anaesthesia machines, circuits and drug infusion devices were excluded from the analysis. The amount of drugs and tubing used was measured. Unit cost estimates for each drug used were provided, although the source of these unit costs was not provided. Price years used in the analysis do not appear to have been stated. Costs were not discounted, which was appropriate given the short duration of the study.
Statistical analysis of costs A statistical analysis of costs (variable) was conducted, although details of the actual test used were not given. P values were reported.
Indirect Costs Indirect costs were not included.
Sensitivity analysis No sensitivity analysis was conducted.
Estimated benefits used in the economic analysis Not applicable due to the cost-minimisation approach adopted. The reader is referred to the effectiveness results.
Cost results Average costs per patient were significantly lower for Group O patients, Can$17.15 +/-8.10 compared with Can$20.71 +/-10.05 for Group P patients, (p<0.01).
Synthesis of costs and benefits Not applicable (due to the cost-minimisation approach).
Authors' conclusions Ondansetron treatment was equally effective, but less expensive than propofol treatment in the study setting. However, the economic analysis was very limited, as the costs of anaesthesia drugs make up only a small part of the total costs of treatment.
CRD COMMENTARY - Selection of comparators A justification was provided for the comparator used. Propofol is a drug therapy that has previously been shown to be effective in reducing the rate of post-operative emesis in children undergoing strabismus surgery. You, as a user of the database, should consider whether this is appropriate within your own setting.
Validity of estimate of measure of effectiveness The analysis was based on a randomised controlled trial which was appropriate for this study, although practitioners were not blinded to allocation of patients, which the authors acknowledged could have introduced bias. The study sample selected appears to have been appropriate for the study population under examination and its size was determined by power calculations. Patient groups were shown to be comparable at analysis, and results were based on the intention to treat. The validity of the results was also enhanced by appropriate statistical analyses.
Validity of estimate of measure of benefit The estimate of benefits used in the economic analysis, the incidence of post-operative vomiting, was taken directly from the effectiveness analysis. This was appropriate.
Validity of estimate of costs The cost perspective adopted in the analysis was never clearly stated in the paper. The authors acknowledged that their cost analysis was very limited, as only the costs of drugs used in anaesthesia and administration tubing required were included in the analysis. The authors also acknowledged that, in addition to many direct costs being omitted, the economic analysis should also have included indirect costs such as lost productivity (for parents) and educational attainment (for children). They implicitly noted that the results of their analysis could have been affected by these factors, when acknowledging that the costs of drugs represented only a small fraction of total costs. Costs and quantities were reported separately. Resource use in the analysis was taken from the clinical study, but no statistical analysis of quantities to test against uncertainty was reported in the paper. The source of unit cost data for anaesthetic drugs used in the analysis does not appear to have been stated. The base price year used in the analysis does not appear to have been stated, which limits the generalisability of the results to other settings.
Other issues The authors made appropriate comparison of their findings with those of other studies but the issue of generalisability of findings to other settings was not really addressed, although the authors acknowledge that their findings were specific to their own setting. The authors did not present their results selectively; they did however acknowledge that, in addition to non blinding of staff, bias could have been introduced during the co-intervention phase of the study when some patients required a rescue anti-emetic. The lack of reporting concerning dates restricts the replicability of the results.
Implications of the study Within the caveats stated above, the study findings support the use of ondansetron for this patient domain.
Bibliographic details Splinter W M, Rhine E J, Roberts D J. Vomiting after strabismus surgery in children: ondansetron vs propofol. Canadian Journal of Anesthesia 1997; 44(8): 825-829 Indexing Status Subject indexing assigned by NLM MeSH Adolescent; Antiemetics /therapeutic use; Child; Child, Preschool; Female; Health Care Costs; Humans; Male; Ondansetron /therapeutic use; Postoperative Complications /prevention & Propofol /therapeutic use; Single-Blind Method; Strabismus /surgery; Vomiting /chemically induced /prevention & control; control AccessionNumber 21997001157 Date bibliographic record published 31/01/2002 Date abstract record published 31/01/2002 |
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