Does every overdose patient need an ASA

and APAP level?Rob Hall MD, PGY4

FRCPC Emergency Medicine

Oct 31, 2003

Case: Doc, did I take enough??? 40 yo female Multi-drug ingestion 20 tylenol arthritis, 20

gravol, 5 paxil, and “two beers”

HR 115, BP/RR/Sats normal, afebrile, pupils 6mm, slightly flushed, skin dry, reflexes and tone normal, no bowel sound

What tests would you like to order?

What if you are in Tim Buck Two and can’t do an ASA level?

My “tox screen” Lytes, BUN, Cr, Glucose EtOH, osmolarity ASA, APAP ECG

BUT WHAT IF I WORKED IN TIM BUCK TWO!!

Does every patient need an ASA level?------------>Considerations Lytes are a reasonable screen

– Acetyl salicylic acid and salicyclic acid are both acids thus your bicarb will drop in an ASA overdose giving the classic increased AGMA

Treatments: alkalinization +/- dialysis– ? time sensitive

What does the literature say about routine ASA testing?

Literature and Routine ASA testing Wood Abstract

– History of ASA ingestion had a sensitivity of 81% which is not high enough to be used as a rule out test

– 1/5 or 20% of ASA ingestions would thus be missed alone by history

Literature and Routine ASA testing Chan. Vet Human Toxicol 1995

– Retrospective study of 347 patients– Identified all ASA levels from lab data– Patients NOT suspected of having ingested

ASA• 3/264 (~3%) had measurable ASA levels

• Didn’t define what “NOT suspected” meant

– Conclusion: routine ASA levels are not necessary

Literature and Routine ASA testing Sporer. Am J Emerg Med 1996

– Retrospective review of 1820 patients that had either a positive ASA or APAP

– Overall 155 (8.5%) had elevated ASA levels• History was +ve in 44/155 • History was –ve in 111/155• Sensitivity of history was thus 28%

– ANION GAP was > 20 in all patients (except one where it was 17)

Does every patient need an ASA level?

NO!

Indications for ASA levels

– History of ASA ingestion– History of tylenol or other OTC analgesic – Clinical features of ASA toxicity (tinnitis, hearing

deficit, confusion etc, pulmonary edema, cerebral edema, renal failure)

– ALL with anion gap metabolic acidosis– Anyone taking ASA as a regular med (chronic toxicity

often missed in elderly)– Unreliable history, decreased LOC

• Screen with lytes if ASA level not readily available

What about acetaminophen?

Significant difference from ASA!!– Toxic metabolite is NAPQI– There is NO test to detect NAPQI formation– Hepatotoxicity is NOT evident until AST/ALT

rise which occurs usually around 24hrs– If you wait for the AST to rise before starting

NAC, you have missed the BOAT!!• Smilkstein

• Prescott

Acetaminophen

Universal testing of APAP makes sense if readily available

What does the literature say?

Routine APAP levels?

Study Methods APAP ingestion suspected

APAP ingestion NOT suspected

Chan 1995 All cases were APAP was measured

N=294

49/86 4/208 (1.9%)

Dargan 2001

All cases were APAP was measured

N=296

94/160 0/136

(0%)

Universal APAP levels?

Sporer. Am J Emerg Med 1996– Retrospective review of 1820 patients that had

either a positive ASA or APAP– Overall 175 (9.6%) had elevated APAP levels

• History was +ve in 120/175

• History was –ve in 55/175

• History was 68% sensitive

– Conclusion: history not very sensitive for acetaminophen ingestion

Universal APAP levels?

Lucaine 2002– Retrospective review of all overdoses over a 6

month period at a poison center– ONLY looked at patients where acetaminaphen

ingestion was NOT suspected– 300 cases where APAP levels available– 23/320 (7.2%) had +ve levels – Conclusion: routine screening justified

Retrospective studies are problematic!

Is there any prospective evidence?

Universal APAP levels?

Ashbourne 1989– Only prospective study– Looked at all overdoses– Suspected ingestions: 43/114 (38%) had

measurable levels– Not suspected: 7/114 (1.9%) had measurable

levels (none were toxic)– Conclusion: acetaminophen toxicity missed by

history is rare

Summary

APAP– Low risk of missing unsuspected toxic

acetaminophen ingestion– But are we willing to take that risk when there

is an effective treatment?– APAP levels in all overdoses if readily

available– If not readily available -----------> case by case

decision