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Stephenson and colleagues have written a clear and well referenced article, taking the view that urban prehospital thrombolysis is unlikely to be either clinically or cost effective.1 Some of their arguments in support of this assertion, such as the idea that urban prehospital times are very short or that complications are a significant concern, I have already addressed. We both agree that one of the main problems in this field is a lack of research, and until adequately powered studies of paramedic administered urban prehospital thrombolysis are published we must rely upon educated guesswork and extrapolation. Such studies will also allow us to address the issue of cost effectiveness. I have already emphasised the potential benefits of investment in prehospital, rather than inhospital, interventions, and while there is some evidence of cost effectiveness for the prehospital ECG,2 this has yet to be investigated for prehospital thrombolysis.
There are two aspects of the article by Stephenson et al that I feel particularly compelled to respond to. The first concerns the relation between clinical benefit and the “pain to needle” time. As Stephenson and colleagues acknowledge, there is disagreement as to whether this relation is linear or exponential,3 but if exponential then the arguments for urban prehospital thrombolysis are considerably strengthened. In fact, there is good evidence that thrombolysis within about 90 minutes of infarction can have a dramatic, and disproportionate, effect on outcome.4,5 There are many clinical examples of the principle that early reversal of tissue ischaemia, before irrevocable damage occurs, can be followed by excellent recovery. Indeed, nobody suggests that the relation between skeletal muscle death and surgical tourniquet time is linear: why then should it be so for the heart? Our efforts therefore need to be directed towards the attainment of very short pain to needle times, and these will only be achieved by intervention in the prehospital phase of care.
Secondly, Stephenson and colleagues state that the most likely model for prehospital thrombolysis in the UK is administration by paramedics without online support. I disagree. As outlined in my article, most paramedics do not yet feel ready to administer prehospital thrombolysis without support, and in regions where this new technique is currently being adopted transmission of the ECG to hospital for physician authorisation and guidance is the norm. While this may change in years to come, remote physician support is a common, and relatively well researched, model at present.
Stephenson et al rightly draw attention to the importance of addressing the delay between symptom onset and calling for help, and invoke the exponential model of thrombolysis benefit to support this. However, the other measures that they propose, which are designed to reduce the inhospital “door to needle time”, are all inferior to effective prehospital thrombolysis.
Regardless of medical opinion, there is now a clear government commitment to introduce prehospital thrombolysis throughout the UK.6 I hope that this also provides an opportunity for properly conducted research and evaluation, to govern policy and more fully inform this interesting and important debate.
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