1. Does every overdose patient need an ASA and APAP level? Rob Hall MD, PGY4 FRCPC Emergency Medicine Oct 31, 2003

2. 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?

3. My “tox screen”  Lytes, BUN, Cr, Glucose  EtOH, osmolarity  ASA, APAP  ECG  BUT WHAT IF I WORKED IN TIM BUCK TWO!!

4. 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?

5. 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

6. 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

7. 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)

8. Does every patient need an ASA level? NO!

9. 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

10. 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

11. Acetaminophen  Universal testing of APAP makes sense if readily available  What does the literature say?

12. Routine APAP levels? StudyMethodsAPAP ingestion suspected APAP ingestion NOT suspected Chan 1995All cases were APAP was measured N=294 49/864/208 (1.9%) Dargan 2001 All cases were APAP was measured N=296 94/1600/136 (0%)

13. 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

14. 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

15. Retrospective studies are problematic! Is there any prospective evidence?

16. 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

17. 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