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Robert Walton a ICRF General Practice Research Group,
University of Oxford, Department of Public Health and Primary Care,
Institute of Health Sciences, Oxford OX3 7LF, b Department of Health
Sciences and Clinical Evaluation, Alcuin College, York YO1 5DD, c Centre for
Health Economics, University of York, York YO1 5DD
Correspondence
to: Dr Walton
robert.walton{at}public-health.oxford.ac.uk
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Abstract |
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Objective:
To review the effectiveness of computer
support for determining optimum drug dose.
Design:
Systematic review of comparative studies where computers gave advice to clinicians on the most appropriate drug dose.
Search methods used were standard for the Cochrane Collaboration on
Effective Professional Practice.
Subjects:
Comparative studies conducted worldwide and published between 1966 and 1996.
Main outcome measures:
For qualitative review,
relative percentage differences were calculated to compare effects of
computer support in different settings. For quantitative data, effect
sizes were calculated and combined in meta-analyses.
Results:
Eighteen studies met the inclusion criteria. The drugs studied were theophylline, warfarin, heparin,
aminoglycosides, nitroprusside, lignocaine, oxytocin, fentanyl, and
midazolam. The computer programs used individualised pharmacokinetic
models to calculate the most appropriate dose. Meta-analysis of data from 671 patients showed higher blood concentrations of drug with computer support (effect size 0.69, 95% confidence interval 0.36 to
1.02) and reduced time to achieve therapeutic control (0.44, 0.17 to
0.71). The total dose of drug used was unchanged, and there were fewer
unwanted effects of treatment. Five of six studies measuring outcomes
of care showed benefit from computer assistance.
Conclusions:
This review suggests that using computers to determine the correct dose of certain drugs in acute hospital settings is beneficial. Computers may give doctors the confidence to
use higher doses when necessary, adjusting the drug dose more accurately to individual patients. Further research is necessary to
evaluate the benefits in general use.
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Key messages
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Introduction |
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Maintaining therapeutic drug concentrations is a complex task requiring knowledge of medicine and pharmacokinetics, a good rapport with the patients, and some skill in calculating dose. Harm can be caused by miscalculating doses because many drugs have a narrow "window" in which therapeutic benefits can be obtained at a low risk of unwanted effects.
Monitoring drug treatment to optimise effects and minimise dangers can be time consuming and requires meticulous attention to detail. Doctors sometimes make errors of judgment because their capacity to process information is exceeded,1 and their computational skills may be inadequate to perform calculations about drug dose.2 For example, 82 of 150 hospital doctors were unable to calculate how many milligrams of lignocaine were in a 10 ml ampoule of 1% solution.3
Computers, however, are very good at gathering information and
performing repetitive calculations. Several computer systems have been
designed to help doctors to determine the optimum dose of drugs. We
assessed the benefits of these systems to establish whether they should
be used more widely.
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Methods |
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Inclusion criteria
We identified all comparative studies in which computers
were used to help determine the most appropriate drug dose. The
criteria for entry into the review were standard for reviews undertaken
by the Cochrane Collaboration on Effective Professional Practice
and include methodological and quality criteria for rigorous design
of experimental and quasi-experimental studies.4
Search strategy
Relevant studies were located from the specialised register of
studies of the Cochrane Collaboration on Effective Professional
Practice.5 This register is updated by electronic searches
and hand searches of relevant journals. We also located references
through bibliographies of related topics and contact with experts and
pharmaceutical companies. We made specific searches of Medline and
Embase from 1966 to June 1996 to identify relevant references. The
search terms were "computer assisted decision making"
or (prescr* and comput*)
and ("randomised controlled trial" or
"random allocation" or "double blind method").
Search strategies were modifications of those designed to give a high
yield of randomised controlled clinical trials.6 In
addition, we hand searched issues of Therapeutic Drug
Monitoring published from January 1993 to July 1996.
Outcomes
Outcome measures, determined in advance, were
Data extraction
Two researchers reviewed each study independently and, using a
standard form, extracted data on methodology, outcomes, and quality
criteria.4 We recorded the unit of allocation and analysis, concealment of allocation, blinding, statistical power, follow up of patients and professionals, baseline measurements, and
protection of the control group from contamination by the intervention.
We calculated the mean difference in outcome with computer support, as
a percentage of the mean value without support for all outcomes fitting
our criteria for inclusion. These relative percentage differences were
used in the narrative part of the review.
Quantitative analysis
Studies with comparable outcomes were divided into groups for
meta-analysis according to outcome measure. Of the six predefined
outcome measures, only four provided suitable data for meta-analysis:
dose of drug; blood concentrations of drug; time to reach therapeutic
concentration or effect; and difference between patients' drug
concentration and target concentration. Four separate meta-analyses
were performed.
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Results |
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Characteristics of included studies
We identified 23 relevant studies, of which 16 randomised
controlled clinical trials8-23 and one non-randomised controlled clinical trial24 met the inclusion criteria.
All used reliable outcome measures with adequate blinding of
assessment. No interrupted time series or studies controlled at a
second site were identified. Sixteen studies used patients as the unit
of allocation; one allocated medical firms to intervention and
control.9 Three studies did not use the same unit for
allocation and analysis.
9 12 16
Only two studies
reported a power calculation.
11 15
Six studies reported
adequate concealment of allocation (for example, random numbers in
opaque envelopes),8-13 12 followed up more than 80% of
patients,
8 12 13 15-20 22 24 25
12 reported similar
baseline measures between intervention and control
groups,
8-14 16 19 20 23 24
nine recorded that
patient consent had been
obtained,
8-10 15 18-20 22 23
and eight reported
gaining approval from an ethics
committee.
8 10 12 18-20 22 24
In one study the
reviewers thought that there was little room for improvement because
the performance of the health professional was adequate without the
intervention.23
Types of computer support systems
used
Most of the computer systems used a mathematical model of the
pharmacokinetics of the drug in question to predict the required dose
(table). These models represent the compartments in the body in which
the drug is distributed. Rate constants are used to describe the
movements of the drug between different compartments. The models ranged
from a simple, one compartment model for theophylline14 to
a more complex, three compartment model for fentanyl.24
The starting values for the rate constants were estimated from
population data but could then be adjusted as data accumulated from an
individual patient. The systems allowed the operator to specify a
target blood concentration of drug, which the computer then attempted to achieve. When the effect of the drug was more important than its
blood concentration, pharmacodynamic parameters based on population data were added to the model.22
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Effects of computer support on outcome
The table shows the effects of computer support on the process and
outcome of care.
Eleven studies examined change in the drug dose when computer support was
used,
8 9 11 13 14 17-19 21 23 24
and seven found
significant changes.
8 13 14 17 19 21 24
Studies on
theophylline showed increases in initial dose
14 21
and in
maintenance dose.
13 14
Studies on intravenous anaesthesia showed a reduction in total dose of fentanyl used24 and a
reduction in initial dose and maintenance dose of
midazolam.19
Drug concentrations within desired range
Of the seven
studies that measured changes in drug concentrations in the body two
found significant increases in the proportion of patients with drug
concentrations in the therapeutic range with computer
support.
9-11 13 14 17 21
Physiological control
Eight studies measured changes in
control of a physiological parameter with computer
support,
8 15 16 18 20 22-24
of which six showed
significant benefit.
8 15 18 20 22 24
Computer support
for anticoagulant control resulted in significant reductions in the
time taken to achieve the desired prothrombin time22 and
activated partial thromboplastin time.15 In postoperative control of blood pressure with sodium nitroprusside, a computer assisted pump was more effective at keeping blood pressure in the
target range than a manually controlled infusion. Babies delivered to
women treated with computer controlled oxytocin had a lower lactate
concentration in the umbilical cord blood.8
Unwanted effects of drug treatment
Six studies measured the
unwanted effects of drugs,
11 12 14 15 22 24
and four
found significant reductions associated with computer
support.
14 15 22 24
Fewer patients treated with
theophylline reached toxic drug concentrations when computer advice was
used.14 In studies on anticoagulation both the number of
patients given too much anticoagulant22 and the total
number of adverse events15 were reduced in the
intervention groups. The number of hypotensive episodes during cardiac
surgery was reduced when fentanyl and midazolam were given via a
computer controlled pump.24
Cost of drug treatment
Only two studies reported economic
data, and both looked at computer support for aminoglycoside
dose.
9 11
In one study the mean direct cost of treatment
with computer support was $7102 compared with $13 758 in controls
(P<0.02), with a benefit to cost ratio of 75.11 The other
calculated a cost avoidance (the money potentially saved by the
intervention) of $1311 for each patient treated, with a benefit to cost
ratio of 4.1.9 These cost savings resulted largely from
reduced hospital stays, which was confirmed in one
study,14 although another suggested an increased time
spent in hospital.10 Another study showed that computer
support lengthened the interval between outpatient visits.12
Outcome of medical care
Six studies directly measured
outcomes of care, of which five showed benefits. Three showed
significant benefits in clinical improvement scores for
asthma,21 treating infection,9 and pain
relief after surgery.20 Fewer caesarean sections were
required when oxytocin was given by computer controlled pump to augment
labour.9 With computer support for hospital treatment of
acute asthma, fewer patients subsequently needed convalescent
care,13 and there were fewer deaths.14 One
study on anticoagulation showed an increase in the number of embolisms, but it may be that the computer system used in this study was set to
achieve too low a prothrombin time.12
Overall effect
Eleven studies provided outcomes for
quantitative synthesis,
10 11 13-15 17-19 21-23
and
the figure shows the individual results and meta-analysis for each of
the four outcome measures. Patients treated with computer support had
higher blood concentrations of the drug (effect size 0.69, 95%
confidence interval 0.36 to 1.02) and took less time to reach
therapeutic concentrations (
0.44,
0.71 to 0.17). However,
computer support had no significant effect on the total amount of drug
used (
0.43,
1.00 to 0.15) nor on the difference between the level
of a physiological parameter achieved and the target level (
1.22,
3.31 to 0.87). Although the clinical settings of the trials varied
widely, only in the case of difference from target level was there
evidence of statistical heterogeneity.
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Discussion |
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This review suggests that substantial benefit results from computer support for determining the dose of certain drugs in acute hospital settings. In the studies we identified, unaided doctors were often excessively cautious in estimating drug dose. This caution presumably resulted from an unwillingness to expose patients to adverse effects of drug treatment. Unaided doctors used lower initial doses and maintenance doses than when computer support was available. 14 21 Lower doses lead to lower blood concentrations and often to suboptimal therapeutic effects. Although doses with computer support tended to be higher than those used by unaided doctors, no studies reported an increase in unwanted effects due to overdose. This suggests that the computers helped doctors to tailor drug doses more accurately to individual patients. Higher initial doses with computer support gave more rapid therapeutic control, 20 22 bringing benefits for patients and reducing the time that they spent in hospital. 9 14 22 Unaided doctors tended to exercise caution in checking blood concentrations, which resulted in more blood tests15 and hospital visits.12
The most successful systems were those in which the computer administered drugs directly to patients under medical supervision. Manually controlled infusions resulted in higher doses of anaesthetic agents compared with computer controlled infusions. 19 24 This may result from the doctors' reluctance to expose patients to the risk of unnecessary pain. However, patients treated with computer support experienced less pain,20 suggesting that computer support could help doctors to adjust drug doses more accurately for individual patients.
Methodological issues
Potentially, the most important factor that may undermine our
analysis is publication bias
studies with positive results are more
likely to be published than those with negative results.26
Our search was exhaustive, and it seems unlikely that large numbers of
patients have been randomised to trials that we have not identified.
Orwin's file drawer method suggests that there would need to be 24 unpublished studies showing no benefit from computer support to alter
our results significantly.27
Implications for computer support for drug dose
The scope of computer support systems could be widened to include
other, commonly prescribed drugs with a narrow therapeutic window, such
as anticonvulsants and lithium. A computer might use the same basic
pharmacokinetic model for several different drugs. It is possible that
the model could be extended to predict the likelihood and severity of
some interactions
for example, those caused by competition for protein
binding sites.
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Acknowledgments |
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A parallel version of this review will appear in the Cochrane Library. We thank referees in the Cochrane Collaboration on Effective Professional Practice review group for helpful comments on the protocol for this review. Since this review was conducted, the Cochrane Collaboration on Effective Professional Practice has changed its name to the Cochrane Effective Practice and Organisation of Care Group (EPOC).
Contributors: All the authors contributed to writing the protocol and participated in dual, independent data extraction and in reviewing drafts of the paper. RW developed the hypothesis, initiated the study, coordinated the review process, and wrote the original draft of the paper. RW and NF conducted the meta-analyses with advice from Frederick Wolf. SD constructed the data tables and hand searched Therapeutic Drug Monitoring. Emma Harvey helped to refine the protocol and contributed extensively to revising the paper. Andy Oxman helped to refine the study question. Martin Vessey, Pat Yudkin, and Mike Murphy commented on earlier drafts of the paper. RW is guarantor for the article.
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Footnotes |
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Funding: NHS research and development programme evaluating methods to promote the implementation of research findings. RW is supported by a Royal College of General Practitioners/BUPA training fellowship. SD was supported by the New Zealand Health Research Council.
Competing interest: None reported.
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References |
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an important step towards evidence based health care.
Ann Intern Med
1997;
126:
81-83(Accepted 9 November 1998)
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