Acetaminophen and self poisoning: There is a role for a level drawn less than 4 hours.

In this podcast, Dr. Rita McKeever and I try to use some recent evidence to see if we can hasten the throughput of self-poisoning patients in the ED.

First let’s look at:

Can a serum acetaminophen concentration obtained less than 4 hours post-ingestion determine which patients do not require treatment with acetylcysteine? Mark C. Yarema, Jason P. Green, Marco L. A. Sivilotti, David W. Johnson, Alberto Nettel-Aguirre, Charlemaigne Victorino, Daniel A. Spyker & Barry H. Rumack

The short answer is NO! If you suspect acetaminophen overdose then you should properly identify a time or range for a 4 hr level and obtain the specimen at that time.

However – “Only very low to undetectable acetaminophen concentrations prior to 4 hours reliably excluded a subsequent concentration over the treatment line.” We can use this to our advantage for patients who we do NOT suspect to have an acetaminophen overdose!

In this UK study, none of the 136 patients who denied taking acetaminophen had a detectable level at 4 hours.

Dargan PI, Ladhani S, Jones AL Measuring plasma paracetamol concentrations in all patients with drug overdose or altered consciousness: Does it change outcome? Emergency Medicine Journal 2001;18:178-182.

In another UK study, less than 10% (13 of 155) of patients who denied taking acetaminophen had any detectable level and none required antidote.

Hartington, K., Hartley, J., & Clancy, M. (2002). Measuring plasma paracetamol concentrations in all patients with drug overdoses; development of a clinical decision rule and clinicians willingness to use it. Emergency Medicine Journal : EMJ, 19(5), 408–411.

So although you can lower the prior probability of acetaminophen poisoning when the patient denies ingestion, you cannot completely exclude the diagnosis without an acetaminophen level. However, you can save a few hours of ED time – here’s how:

When you do NOT suspect an acetaminophen overdose (prior probability is close to zero!) , an undetectable level before 4 hrs (at 2 hours and even as soon as 1 hour) post ingestion will reliably exclude acetaminophen toxicity (likelihood ratio of zero!). If you draw a < 4hr level and it shows detectable acetaminophen  – it must be repeated at 4 hours to determine if it needs treatment.

If you DO suspect an acetaminophen overdose, obtain only a 4 hour level to guide NAC therapy.

Hopefully this will help with a more rapid throughput of patients with self poisoning who need to be medically cleared for further psychiatric evaluation. Of course, this represents one opinion based on a review of the literature. A prospective trial would be needed to prove this conclusively.

Enjoy the Podcast!


Heroin overdoses and naloxone reversal: ok for discharge or mandatory observation?

In this podcast Dr. Rita McKeever and I review the recent article entitled Do heroin overdose patients require observation after receiving naloxone? from our toxicology friends at Washington University – Michael W. Willman, David B. Liss, Evan S. Schwarz & Michael E. Mullin.  They reviewed the literature to try and answer the following questions:

(1) What are the medical risks to a heroin user who refuses ambulance transport after naloxone?

(2) If the heroin user is treated in the emergency department with naloxone, how long must they be observed prior to discharge?

(3) How effective in heroin users is naloxone administered by first responders and bystanders? Are there risks associated with naloxone distribution programs?

We also take a look at Ed Boyer’s article Management of Opioid Analgesic Overdose and an important but older article entitled Early discharge of patients with presumed opioid overdose: development of a clinical prediction rule.

The clinical prediction rule that may predict safe discharge is as follows:

1) can mobilize as usual; 2) have oxygen saturation on room air of >92%; 3) have a respiratory rate >10 breaths/min and <20 breaths/min; 4) have a temperature of >35.0 degrees C and <37.5 degrees C; 5) have a heart rate >50 beats/min and <100 beats/min; and 6) have a Glasgow Coma Scale score of 15

We conclude that if the patient demonstrates all six features carefully applied WITH the caveat that there be no verbal or tactile stimulation prior to the evaluation, then the patient  is likely to be safe to discharge after reversal with naloxone. This concept has not been strictly tested in the literature, but the article in Clinical Toxicology supports this practice. And now on to the podcast … let us know what you think!

Receiver Operator Characteristic Curves explained!

Warning: statistics ahead!! Actually, this very short VODcast is designed to keep it simple and help you understand ROC curves, sensitivity, specificity, positive predictive value, negative predictive value, and prevalence. Here is the paper I use to discuss this:

Glasgow Coma Scale Motor Component (“Patient Does Not Follow Commands”) Performs Similarly to Total Glasgow Coma Scale in Predicting Severe Injury.


Synthetic cannabinoids: how science manufactured a drug epidemic and how to treat it


In this vodcast I discuss endocannabinoids, phytocannabinoids, and synthetic cannabinoids. I review the cannabinoid receptor physiology and how it leads to the  chaotic clinical course seen in synthetic cannabinoid overdoses, such as the profound hypotension and bradycardia we call the K2 Krash. Hopefully at the end of the broadcast you will have a sufficient understanding of all things cannabinoids to treat this growing epidemic. Enjoy!