Tox Craze - The Original Kings of County

Written by Alex Brevil

A 52 y/o woman w/ fibromyalgia is found alone in her room in a confused state by her maid. She recently lost all of her retirement money and constantly “Blames Obama.” She is then rushed to the emergency room where she is found to be disoriented x2 (oriented to the president only) w/ flushed skin. The patient begins to seize just after the nurse takes her vitals (and the med student faints).

VS- pulse- 130bpm, BP- 95/60, RR- 24, T-101.5

PE- Pupils 6mm b/l, distended lower abdomen, absent bowel sounds

What is the most likely diagnosis?

TCA (or TC-Eh? in Canadian) toxicity!!

Derived from synthetic antihistamines in the 1940’s whose psychiatric effects were noted in the 1950’s

Common Drugs– Amitriptyline, Imipramine. Clomipramine, Nortriptyline

Indications– Depression, panic disorder, obsessive compulsive disorder, chronic pain syndromes (fibromyalgia, neuropathic pain, migraine ppx)

TOXICITY…..

Cardiovascular

Effects are similar to Class 1 antiarrhythmics…. Via sodium channel inhibition.

Which can cause: QRS, QT, PR prolongation…. And can lead to VT, VF.
Other signs: Large terminal R wave in avR.
Also sinus tachycardia and hypotension can occur.

CNS Effects

Mental status changes such as obtundation (due to antihistaminic effects)
Delirium (due to anticholinergic effects)
Seizures (GABA-A receptor antagonist)

Anticholinergic effects… You guys remember the pneumonic…

Blind as a Bat (Mydriasis)

Mad as a Hatter (CNS symptoms)

Red as a Beet (Flushing)

Hot as a Hare (Cannot sweat)

Dry as a Bone (urinary retention, decreased bowel sounds, dry mucous membranes).

TREATMENT

ABC’s first…

Intubation, Supplemental O2, Crystalloid
Get an EKG – If QRS > 100 msec —intravenous sodium bicarbonate (for sodium load)
If pressors needed, use NE or neosynephrine
If patient develops Torsades, treat w/ MgSO4

Then…

Hyperventilate w/ pH goal 7.5-7.55
Treat seizures w/ benzos (GABA agonist)
Gastric Lavage?
- May be effective in the setting of decreased gastric emptying.

What about Physostigmine (Cholinesterase Inhibitor)?

Not recommended in patients w/ known or suspected TCA overdose 2/2 association with cardiac arrest… It was previously part of the coma cocktail and was associated with cardiac arrest in a couple of case reports in the 80’s.

Remember CO = HR x SV (Alpha antagonist effects cause low bp and HR is keeping up the cardiac output, therefore, slowing this down with a cholinergic drug theoretically can cause a dangerous drop in cardiac output!!!!!

Meds CONTRAINDICATED in TCA overdose:

All class Ia, Ic and III antiarrhythmic agents
- (lidocaine (class Ib) can be used as a third line treatment for cardiac toxicity).
β-blockers
Calcium channel blockers

Summary

1. Take a good medical history and physical exam

2. Early intervention (ABC’s, EKG!!!!!)

3. Early correction of conduction abnormalities w/ Sodium Bicarb.

4. No physostigmine…

References:

Lynch R. Tricyclic antidepressant overdose. Emerg Med J 2002; 19:596

Kerr GW, McGuffie AC, Wilkie S. Tricyclic antidepressant overdose: a review. Emerg Med J 2001; 18:236.

Liebelt, EL, Francis, PD. Chapter 57: Cyclic Antidepressants. In Goldfrank LR et al [eds], Goldfrank’s Toxicologic Emergencies (7th Edition). New York, McGraw-Hill, 2002.

Tran TP, Panacek EA, Rhee KJ, Foulke GE. Response to dopamine vs norepinephrine in tricyclic antidepressant-induced hypotension. Acad Emerg Med 1997; 4:864

Pentel P, Peterson CD. Asystole complicating physostigmine treatment of tricyclic antidepressant overdose. Ann Emerg Med 1980; 9:588.

Mills KC. Chapter 171. Cyclic Antidepressants. In: Tintinalli JE, Stapczynski J, Ma O, Cline DM, Cydulka RK, Meckler GD, T. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7e. New York, NY: McGraw-Hill; 2011

The views expressed on this blog are the author's own and do not reflect the views of their employer. Please read our full disclaimer here. Any references to clinical cases refer to patients treated at a virtual hospital, Janus General Hospital.