MONA or just ONA?

The age old acronym of "MONA" used in the management of acute coronary syndrome has recently come under some criticism after a study published in 2005 in the American Heart Journal noted that patients treated with morphine had a higher mortality rate than those who did not recieve morphine. Two subsequent letters to the editor differed in their reception of this information (as good science would have it). So, what is the gist?

The study itself - "Association of intravenous morphine use and outcomes in acute coronary syndromes: Results from the CRUSADE Quality Improvement Initiative" - was a non-randomized, retrospective, observational trial. It enrolled patients presenting with non-ST-segment elevation acute coronary syndromes and ultimately noted an increased odds ratio of death of about 1.5. Considering its limitations, the study was well done and run through several re-assessments, including risk adjustment (i.e. comparing the sickest patients given morphine to the sickest patients not recieving morphine) and matching on propensity score for treatment (most basically, an attempt to minimize the influence of confounding variables). Ultimately, there needs to be a randomized control trial on the issue, but this is still concerning.

The letters to the editor (December 2005; American Heart Journal):

#1: Observation that morphine supresses ("paralyzes") cortisol production in the opioid-naive, potentially dropping levels as much as 75% or more within 3 hours. Occasional Addisonian crises. Notes that some reports suggest improved survival in MI patients treated with corticosterooids (I am personally not familiar with this information), possibly due to a replacement effect rather than the oft cited anti-inflammatory hypothesis.

#2: Although the original article cites a source that suggests morphine increases infarct size in animal models, this author notes that in his own lab, morphine reduces infarct size. He does note, however, that the effect is largely dose-dependent and time-dependent, showing no effect at higher doses and being effective only when given before and ischemic event and just before reperfusion, losing their cardioprotective effect when administered after reperfusion. How this compares to the other study that suggests that morphine not only does not work but is harmful, I haven't figured out yet. I'll update when I do.