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General Toxicology

A lecture for emergency medicine residents
by

Patrick Lank

on 10 June 2016

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Transcript of General Toxicology

General Management of the Poisoned Patient
Thank you for your attention!
A: Airway
B: Breathing
C: Circulation
Sympathomimetic

Sedative-Hypnotic

Opioid

Anticholinergic

Cholinergic
Tests to order on every suicide attempt:
CBC
BMP
(UHCG)
EKG
Ethanol level
Salicylate level
Acetaminophen level
General Approach
Toxidromes
Tox Labs
Patrick Lank, MD MS
Northwestern University
Department of Emergency Medicine
Toxikon Consortium
Ipecac
Decontamination
Common Methods
Enhanced Elimination
Guess the Poison!
Some "Antidotes"
D: Decontamination
E: Enhanced Elimination
F: Focused Therapy (antidotes)
G: Get Help! (Poison Center)
Sympathomimetics:

Hypertension
Tachycardia
Hyperthermia
Agitation
Mydriasis
Diaphoresis
Sedative-Hypnotics:

Hypopnea
Ataxia
Hypotension
Normal/bradycardia
Opioids:

Hypopnea
Hypothermia
Miosis
Hypotension
Bradycardia
Decr Bowel Sounds
Anticholinergic
:

Delirium
Tachycardia
Flushing
Dry
Mydriasis
Urinary retention
Tachycardia
Decr Bowel Sounds
Cholinergic:

Diarrhea
Diaphoresis
Urination
Miosis
Bronchorrhea
Bronchospasm
Bradycardia
Emesis
Lacrimation
Salivation
History

How much? (# pills, mg dose)
When? Over what time period?
What? (extended vs. immediate)
Intent?
Their medications?
Exposure to other medications?
Physical:

Vital signs
Mental status
Eyes (pupils, nystagmus)
Abdomen (bowel sounds)
Skin (color, diaphoresis)
Neuro (rigidity, reflexes, clonus)
(Things to consider in OD patients)
Focused tests:
LFTs/Coags
Ammonia
CPK
Drug-specific levels
Head CT
CXR
Labs that deserve discussion:

Urine Drug Screen

Serum osmolality
Urine Drug Screens
NMH UDS:
Amphetamines
Barbiturates
Benzodiazepines
Cannabis
Cocaine
Opiates
Phencyclidine
Some at other institutions:
Methadone
TCAs
Acetaminophen
Propoxyphene
Limitations:
- Substance-specific fluctuations
in specificity, sensitivity, NPV, PPV
- Differences in analyzers used
- Very rarely guides management decisions
- Expensive!
Specific Issues:

Amphetamines:
False-positives: decongestants, bupropion, promethazine
MDMA, MDA variably detected

Benzodiazepines:
Detect oxazepam
May not pick up many benzos (e.g., alprazolam, clonazepam)

Cannabis (THC):
False positives: efavirenz, PPIs (pretty rare)
Will not pick up synthetic cannabinoids

Cocaine - pretty freakin' reliable

Opiates:
False-positives: quinolones, ?poppy seeds?
Will miss most synthetic/semi-synthetics: methadone, fentanyl, hydrocodone, oxycodone, hydromorphone, buprenorphine

Phencyclidine:
False--positives: venlafaxine, dextromethorphan
Serum Osmolality
Definitions:
Osmolarity - # particles in 1 L solution
Calculated
Osmolality - # particles per kg solution
Measured
Annoying Formula

2[Na+] + ([glucose]/18) + ([BUN]/2.8)

Chemistry and serum osmolality MUST be drawn at the same time!!
Normal Range

Depends who you ask
Quite different for each person
Generally accepted range: 10 6 mOsm/L
Things that raise your osm gap:

Osmotically active medications (e.g., ativan, etomidate)
Lactate
Alcoholic ketoacidosis
Renal failure
Shock
Toxic alcohols
In a sick tox patient with no history of toxic alcohol ingestion...

Essentially useless...

(Unless there is an incredibly high gap [>50])
ZERO role in the hospital setting
Essentially zero role in pre-hospital
Gastric Lavage
Use has fallen out of favor
But utility still academically debatable
IF done:
Must be a life-threatening ingestion
Can be performed within 60 minutes of TOI
Risk of the procedure is minimized
Whole Bowel Irrigation
Method

Polyethylene glycol-electrolyte lavage solution (PEG-ELS)

Children: 25 mL/kg/h
Adults: 1.5-2 L/h

Can really only be performed w/ NGT
Continued until clear rectal effluent
Limitations

Really hard to perform correctly
Decreases effectiveness of AC if given at same time
Few and specific indications
Indications

Ingestion of large amount of something that is not adsorbed well by AC and is associated with high morbidity.

Pediatric lead
Large iron overdoses
Other oral metal ingestions
Body PACKERS (not stuffers)
Sustained-release products??
Activated Charcoal
What is it?

1) Pyrolysis of carbonaceous materials:
Wood, coconut, petroleum, and/or peat

2) High temperature treatment with steam and/or carbon dioxide to form an internal maze of pores
Indications

Shortly after ingestion
Much longer after if one of a few substances that readily adsorbs: ASA, APAP, theophylline, TCAs
Must be adsorbable by charcoal
Contraindications

Not adsorbed by AC
Presumed GI perforation
When need endoscopy
Unprotected airway in a patient at risk for aspiration
Decreased bowel sounds
Simply Not Helpful
(And sometimes harmful)
Dosing

Unknown adult ingestion/amount: give at least 50g
Weight-based widely taught but makes no sense
Ideal = AC:drug ratio of 10:1
BE CAREFUL with sorbitol - good for first dose but NOT to be repeated
Hemodialysis/hemofiltration
Urinary alkalinization
Multi-dose activated charcoal
Chelation
Xenobiotic-specific antibody fragments
Less Common Methods
Charcoal hemoperfusion
Exchange transfusion
Nasogastric suction
Plasmapheresis
Hemodialysis
Favorable Characteristics:
Water soluble
Small molecular weight
Low protein binding
Small volume of distribution
Classic Best Drugs to Dialyze:
Toxic alcohols (including ethylene glycol, methanol, diethylene glycol, and propylene glycol)
Salicylate
Theophylline
Rare Drugs Amenable to Dialysis:
Bromide
Selenium
Disopyramide
Fluoride
Early paraquat
Dialyzable Drugs, Questionable Clinical Utility:
Lithium
Valproate
Isopropanol (essentially never necessary)
Atenolol
Phenobarbital
Phenytoin
Advice on Consulting Renal to Dialyze a Toxin:
Offer to place the Quinton yourself
Not really a consult, simply a procedure that needs to happen
Rarely anything to trend - usually a yes/no decision
Specifically if Fomepizole is given, you cannot trend acid/base status!
Multi-Dose Activated Charcoal
Enhanced elimination, not decontamination
Entero-enteric or entero-hepatic circulation
Only certain drugs:

A - aminophylline (aspirin?)
B - barbiturates
C - carbamazepine
D - dapsone
Q - quinine
Urinary Alkalinization
For drugs that are weak acids
Weak acids are ionized at alkaline urine pH
It's harder for ionized drugs to cross cell membranes
Ion trapping: "trapping" the ionized drug in the renal tubular lumen, preventing systemic re-absorption
Used For:
Salicylates
Phenobarbital
Methotrexate
Rare others
How to Do It!
3 amps of sodium bicarb in 1L D5W
Infusion at 1.5x maintenance
Full transcript