The Line is Elegant, but NOT Fail Safe.

Assessing if a patient with acute paracetamol exposure with the Rumack-Matthew nomogram is probably one of the better prediction tool in medicine, but it is not fail safe. As this retrospective study remind us, it can sometime fail to predict late rise in serum paracetamol level crossing into toxic zone, especially when the paracetamol is in mixed formulation with other drugs. Even acute exposure to paracetamol alone sometimes show late rise.

So what are we to do??? Well, my best guess will be, if there is a large ingestion especially in mixed formulation, or when the serum level is really just below the line, we may want to check another level a few hours later.

As far as I know, there is no study to inform if this strategy will make a difference in patient outcome, so no one really knows. Maybe someone wiser have a better plan. Till we know, be mindful...

Dougherty PP, et al. Unexpected late rise in plasma acetaminophen concentrations with change in risk stratification in acute acetaminophen overdoses. J Emerg Med. 2012 Jul;43(1):58-63. Epub 2011 Jun 29.