What causes cardiac arrest


A large randomized study to clarify the controversial importance of adrenaline administration in cardiac arrest ended with an ambivalent result: the survival rate was moderately improved - but at the expense of a higher proportion of patients with severe neurological impairments.

In the largest randomized study to date on the benefit of this measure, intravenous administration of adrenaline in cardiac arrest slightly increased the proportion of patients who were still alive after 30 days. In the rate of patients who could be discharged from the clinic with a favorable neurological result, the result did not differ from that in the placebo group, since significantly more patients in the adrenaline group had severe neurological dysfunction.

Consortium called for placebo-controlled study

As an alpha-adrenergic vasoconstrictor, adrenaline increases aortic diastolic pressure and thus increases coronary blood flow. This increases the likelihood that the heart will return to normal. At the same time, however, there is an increased risk that the microvascular blood flow in the brain will be affected by the alpha-adrenergic stimulation and that cerebral ischemia with severe neurological damage will occur during resuscitation and after returning to normal circulation.

Observational studies have shown that adrenaline increased the chances of spontaneous circulation returning, but was also associated with lower rates of good neurological status in patients treated with it. The International Liaison Committee on Resuscitation (ILCOR), a consortium of seven specialist organizations for cardiopulmonary resuscitation, assessed the current data on the benefit of adrenaline administration as inconclusive and called for a randomized placebo-controlled study to clarify the question of how safe and effective this measure is in cardiac arrest.

Test on 8,000 people with cardiac arrest

A British research group led by Dr. Gavin Perkins from the Warwick Clinical Trials Unit in Coventry in the recently published study PARAMEDIC2 (Prehospital Assessment of the Role of Adrenaline: Measuring the Effectiveness of Drug Administration in Cardiac Arrest).

In the context of this study, 8014 people with cardiac arrest received parenteral injections of either adrenaline or saline solution (placebo) in addition to standard pre-hospital care. In the short term, this measure showed a positive clinical effect, albeit a relatively minor one. A return to normal circulation was achieved with adrenaline in significantly more cases (36.3% vs. 11.7%) - even if this did not prevent death in most cases.

Higher survival rate after 30 days ...

Nevertheless, there was an advantage for adrenaline in the primary endpoint - survival rate after 30 days - while 3.2% of all patients in the adrenaline group were still alive at this point in time, the proportion was significantly lower at 2.4% in the placebo group (unadjusted odds ratio 1.39; 95% confidence interval [CI], 1.06 - 1.82; p = 0.02). The absolute difference of 0.8 percentage points means that 112 patients must receive adrenaline in order for one patient to survive the first 30 days (number needed to treat: 112).

... but also more severe brain damage

However, this very moderate survival advantage is put into perspective when looking at the neurological results of the study: At the time of discharge from the hospital, the proportion of patients with severe neurological impairments according to the modified Rankin point scale was almost twice as high in the adrenaline group as in the placebo -Group (39 of 126 patients [31.0%] vs. 16 of 90 patients [17.8%]). Accordingly, there was no significant difference between the two groups (87 of 4007 patients [2.2%] vs. 74 of 3994 patients [1.9%]) with regard to the proportion of patients who had survived in good neurological condition to hospital discharge (secondary endpoint). ; naOR, 1.18; 95% CI 0.86 - 1.61).

It remains to be seen how the results of the PARAMEDIC2 study will be evaluated - not least by the ILCOR. The relevant evidence for the assessment on the benefit / risk profile of adrenaline administration in cardiac arrest is now provided by this large randomized study. Their results show that this treatment slightly improves the chances of survival for those affected without leading to neurological improvements. In the case of survival, however, the risk of severe brain damage associated with permanent addiction doubles.