SEIZURE PROPHYLAXIS IN HYPERTENSIVE PREGNANCIES - A FRAMEWORK FOR MAKING CLINICAL DECISIONS

Objective To describe a framework for generating therapeutic recommend ations using seizure prophylaxis in hypertensive pregnancies as an exa mple. Design A decision-making framework was built using: 1. evidence of therapeutic benefit, with number needed to treat as the effect meas ure; 2. baseline rates of the target disorder that the treatment was d esigned to prevent; and 3. a treatment threshold, determined by weight ing the potential risks against the potential benefits of the treatmen t. Methods Evidence of therapeutic benefit (i.e. reduction in eclampti c seizures associated with magnesium sulphate therapy in hypertensive pregnancies) was determined by a systematic quantitative overview of c ontrolled clinical trials. Baseline rates of seizures without magnesiu m sulphate therapy were derived from a recent cohort study. A treatmen t threshold was generated using estimates of treatment associated morb idities which were weighted against the potential reduction in seizure s from magnesium sulphate therapy considering the relative values assi gned to these outcomes by obstetricians practising in our hospital.Res ults The number of hypertensive women needed to be treated with magnes ium sulphate to prevent a single case of eclamptic seizures varied in a curvilinear fashion dropping from 1000 to 14 as the baseline rate of seizures increased from 0.1% to 10%. The treatment threshold as measu red by number needed to treat was 64 (range 57-77). The number needed to treat for nonproteinuric hypertension was 1000 (95% CI 180-40,000), whereas it was 32 (95% CI 20-57) for proteinuric hypertension. Consid ering the uncertainty in estimation of the numbers needed to treat and treatment threshold, magnesium sulphate therapy may be recommended fo r women at high risk of eclampsia (e.g. severe pre-eclampsia) while it should be withheld in cases at low risk (e.g. nonproteinuric hyperten sion and mild pre-eclampsia). Conclusion While awaiting further resear ch obstetricians intuitively make decisions about seizure prophylaxis in hypertensive pregnancies. Our decision-making framework generated t herapeutic recommendations by explicit consideration of the available evidence.