The most reliable evidence on which to base decisions comes from the randomised trials assessing thrombolysis and thrombectomy. These have clearly shown that both treatments can improve selected patient’s functional outcomes and that the interval from stroke onset to treatment is the major determinant of the size of the potential benefit:
Thrombolysis within 3 hours produced 10 additional good outcomes /100 treated, if the delay was 3-4.5 hours only about 5 good outcomes /100 were achieved – so 5 fewer patients have a good outcome per 100 treated:
Thrombectomy within 6 hours produced 40 patients with less disability /100 treated but for every additional hour of delay to thrombectomy – 7 fewer patients have a good outcome per 100 treated.
Many factors have been associated with worse outcomes after treatment –e.g. increasing age, increasing stroke severity, high blood sugar, very low or high BP, but they are often associated with poor outcomes even in the absence of treatment and may not influence the size of the treatment effect.
The presence of some factors such as oral anticoagulation, very high blood pressure, recent trauma or operation excluded patients from RCTs so that we have little robust evidence on which to judge the extent to which they might reduce the effectiveness of the treatments. We often have to rely on uncontrolled observational studies which have a high risk of producing biased results.
Page last reviewed: 05 Aug 2023
