Aanesthetic Agents for Day Surgery - NIHR Health Technology ...

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Results of the paediatric economic evaluation
TABLE 60 Costs and outcomes by anaesthetic regimen in the
paediatric study
Anaesthetic Total variable No. of
regimen cost for group patients with
(mean per PONV
patient) (£)
Propofol/halothane 556.5 (3.5) 9 (5.6%)
Sevoflurane/
sevoflurane
2021.2 (12.4) 24 (16.5%)
Sensitivity analysis
Uncertainty: CESA RCT data
Clinical outcomes
The impact of uncertainty around clinical
outcomes was tested using a deterministic
sensitivity analysis on the observed rate of
PONV. In the deterministic sensitivity analysis,
extreme values are taken for a named parameter
individually, in order to examine the effects
on the ICER found in the baseline analysis
of the empirical study.
The extreme (lower and upper) values for the
probability of PONV were defined using 95% CIs
around the observed PONV rate.
Table 61 shows the results of a deterministic
sensitivity analysis on the observed rate of PONV.
The modelled baseline values for the ICERs
TABLE 61 Deterministic sensitivity analysis on the rate of PONV
in the paediatric study
Parameter Anaesthetic regimen
Propofol/ Sevoflurane/
halothane sevoflurane
(n = 159) (n = 163)
Mean cost per patient 4.6 14.8
with PONV (£)
Mean cost per patient 3.5 12.0
with no PONV (£)
Probability of PONV 0.06 0.15
(low 0.02; (low 0.10;
high 0.10) high 0.20)
Probability of no PONV 0.94 0.85
(= 1 – probability of
PONV)
Expected variable cost 3.69 12.42
per patient (£) (low 3.64; (low 12.28;
high 3.74) high 12.56)
closely match the values found in the empirical
study. The two sets of values do not match exactly
due to arithmetic rounding. This sensitivity analysis
shows that the results of the empirical study are
robust in terms of the observed PONV rate.
Bootstrapped distributions of ICERs
Bootstrapped distributions of the ICERs were
generated for propofol/halothane compared with
sevoflurane/sevoflurane (Figure 25). The costeffectiveness
plane generated (2.5% and 97.5%
percentiles –£32 and –£5, respectively) confirms
the conclusion that propofol/halothane is the
dominant arm.
Substitution of isoflurane or sevoflurane
for halothane
The national survey suggested that the use of
halothane in paediatric maintenance anaesthesia
has declined (see chapter 3). It is likely that halothane
will be, or is being, superseded by isoflurane
or sevoflurane. Therefore, the impact of substituting
isoflurane or sevoflurane in the propofol/
halothane regimen was investigated through
simple modelling.
It was not satisfactory to assume that a quantity
(in millilitres) of one anaesthetic was equivalent
to another (i.e. 5 ml sevoflurane is not equivalent
to the administration of 5 ml halothane). To
mirror actual practice as closely as possible, it
was assumed that the clinical endpoint aimed for
by administration of a volatile anaesthetic in the
anaesthetic room or in the operating theatre determined
the quantity of volatile anaesthetic given.
It was thus assumed that an equivalent MAC of
anaesthetic would be given to achieve that clinical
endpoint, irrespective of the particular anaesthetic
given. MACs of oxygen for children were obtained
from the product datasheets and were used to
provide a standard measure of the dose of volatile
anaesthetic administered. The MACs used were
1.08% for halothane, 260 1.6% for isoflurane 260
and 2.4% for sevoflurane 260 (values for children).
The following relationship was assumed:
% Concentration of halothane administered/
MAC halothane =
% Concentration [volatile 2] administered/
MAC [volatile 2]
where volatile 2 was either isoflurane or sevoflurane.
This relationship was used to convert the percentage
concentration of halothane administered
to the percentage concentration of sevoflurane
and percentage concentration of isoflurane at
each time interval.