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

Furthermore, anaesthetists operate in a resourceconstrained
environment, and newer anaesthetic
agents are invariably more costly than established
agents. Therefore, the anaesthetist has to justify
the use of these agents, even if they are providing
improved clinical outcomes or have increased
patient acceptability. The literature provided little,
poor-quality economic evidence, of which very little
was sufficiently robust to support policy decisionmaking.
Lack of evidence regarding the real comparative
cost of different anaesthetic techniques,
and the pressure to reduce spending on drugs in
NHS hospitals compounds the difficulty faced by
clinical practitioners and decision-makers.
In the absence of clear guidance from the
literature, clinical practitioners have little
choice but to rely on their own experience and
preferences, within local drug budget constraints.
It is not surprising that the national survey carried
out as part of the CESA project (see chapter 3)
and the survey by Simpson and Russell 32 suggest
that clinical practice is extremely variable in
this area.
The CESA project and CESA RCT were designed
in response to a call for proposals from the UK
NHS R&D HTA Programme. The call for proposals
was based on a perceived need for additional
information about the relative effectiveness, costs
and patient acceptability of alternative anaesthetic
agents and techniques for day surgery to inform
practice in the UK NHS. The need for this
information in the UK was confirmed by the
literature review and the survey of national
practice, conducted as part of the CESA project.
The research objectives and questions were
developed to address this need.
Anaesthetic regimens and treatment
protocols
The anaesthetic regimens were initially chosen to
reflect practice in the UK when the trial proposal
was developed in 1997. The literature review and
the national survey of practice suggested that the
agents, techniques and treatment protocol chosen
for the adult RCT reflected current practice.
However, the study did not cover all the regimens
used in the UK. The agents and techniques
used for the paediatric RCT were less reflective
of current practice, with halothane now rarely
being used for maintenance of anaesthesia. In
addition, the survey indicated that prophylactic
anti-emetics were routinely used in UK practice.
This was expressly excluded from the treatment
protocol, to increase the power of the trial to
detect differences in the incidence of PONV
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Health Technology Assessment 2002; Vol. 6: No. 30
and minimise distortion of the relative costs of
the regimens.
To address these problems an extensive sensitivity
analysis was undertaken to estimate the expected
costs and effects if: (i) alternative anaesthetic
agents, identified in the national survey, were
substituted for the agents used in the paediatric
CESA RCT; and (ii) prophylactic ondansetron
was added to the anaesthetic regimens used in
the adult CESA RCT. These analyses confirmed
the results of the primary analysis that induction
with propofol followed by propofol or a volatile
agent for maintenance of anaesthesia is more
cost-effective than induction and maintenance
with sevoflurane.
Trial population
A number of factors may mean that the population
of patients treated in the CESA RCT are
not representative of the general population of
patients receiving the day-surgery procedures used
in this study. These are the eligibility criteria and
willingness of patients to participate in the trial.
The eligibility criteria restrict the generalisability
of the results to patients undergoing the daysurgery
procedures included in the CESA RCT
(adult study – general, including urological
surgery, orthopaedic surgery, gynaecological
surgery; paediatric study – general surgery, ENT
surgery), patients who do not require sedative
premedication and patients who are not expected
to need suxamethonium. The day-surgery procedures
are commonly used and comprise a large
proportion of all day surgery. The national practice
survey indicates that the use of premedication and
suxamethonium in routine UK practice is for less
than 10% of patients. These factors would suggest
that the eligibility criteria were unlikely to lead
to an atypical trial population.
There was no evidence that the demographic
or clinical characteristics of the patients who
refused to participate in the CESA RCT differed
from those who did participate. Approximately
half of the patients/parents who refused to
participate in the CESA RCT did not want an
inhalational anaesthetic. If the patients who
participated in the trial were indifferent to
whether they had intravenous or inhalational
induction, the willingness to pay to have an
intravenous induction found in the trial may
be lower than that of the population treated in
routine practice. Again this would suggest that
the cost-effectiveness of anaesthetic regimens
which use propofol for induction is robust and
applicable to the general population.
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