What has this got to do with cardiology? Sometimes it is necessary to challenge the accepted view and take a closer look to reflect on where truth lies. Take the use of adrenaline in cardiac arrest. Ask anyone and they will tell you that during cardiac arrest you need to give adrenaline. If you have ever given adrenaline in this situation you will testify to its effects on blood pressure. For this reason adrenaline is regarded as essential for successful return of circulation after cardiac arrest. However recently people have started to challenge this idea and ask whether adrenaline is really that useful.
A recent study looked at the relationship between pre-hospital use of adrenaline and survival in people with out-of-hospital cardiac arrest. There were 1,556 patients of which 73% received adrenaline and 17% of these had a good outcome versus 63% of those who did not receive adrenaline. The adverse effects of adrenaline were observed regardless of length of resuscitation or in-hospital interventions performed. The adjusted odds ratio of intact survival was 0.48 for 1 mg of adrenaline, 0.30 for 2 to 5 mg and 0.23 for >5 mg. Therefore in a large group of patients who achieved return of circulation, pre-hospital use of adrenaline was consistently associated with a lower chance of survival.
Taken together with other observational studies there is now a randomised controlled trial called PARAMEDIC2 which will administer adrenaline or placebo to cardiac arrest patients and should help to address the question of whether it is help or harm in cardiac arrest. It is worth remembering that before the 1950's adrenaline and other pressor agents were used as standard treatment for all types of shock and it wasn't until later that there came an understanding that this was harmful and that fluid resuscitation was in fact required in most cases.