Toxicology

ToxicologyPaleerat Jariyakanjana, MD

Faculty of Medicine

Naresuan University

5 Jan 2015

Scope

General Management of Poisoned Patients

Acetaminophen

Organophosphorus and CarbamateInsecticides

Diagnosis of Poisoning

History

Physical examination

Lab

Toxicology screening

Abdominal x-rays

http://sketchymedicine.com/2012/01/toxidromes/

Essential clinical laboratory tests

1. Serum osmolality and calculation of the osmolar gap

2. e’: Na, K & AG

3. Serum glucose

4. BUN/Cr

5. LFT

6. CBC

7. UA: crystalluria, hemoglobinuria, or myoglobinuria

8. ECG

9. Stat serum acetaminophen level and serum ethanol level

10.UPT

Tintinalli's Emergency Medicine, 7e


Decontamination

Surface decontamination

Skin

Eyes

Inhalation

GI decontamination

Emesis

Gastric lavage

Activated charcoal

Cathartics

Whole-bowel irrigation

Other oral binding

agents

Surgical removal

Gastric lavage

not necessary for small-moderate ingestions of most substances if activated charcoal can be given promptly

Gastric lavage

Indications

massive overdose or particularly toxic substance + within 30–60 minutes

several hours after ingestion of agents that slow

gastric emptying (eg, salicylates or anticholinergic

drugs)

Contraindications

A. Obtunded, comatose, or convulsing patients

B. Ingestion of sustained-release or enteric-coated tablets

C. Use of gastric lavage after ingestion of a corrosive substance

Activated charcoal

Indications

≤4 hr

Drugs and Toxins Poorly Adsorbed by Activated Charcoal

AlkaliCyanideEthanol and other alcoholsEthylene glycolFluorideHeavy metals

Inorganic saltsIronLithiumMineral acidsPotassium

Activated charcoal

Contraindications

drowsy patient

Technique

60–100 g (1 g/kg), orally or by gastric tube


Indications

A. iron, lithium, or other drugs poorly adsorbed to activated charcoal

B. sustained-release or enteric-coated tablets

C. foreign bodies or drug-filled packets or condoms


Contraindications

A. Ileus or intestinal obstruction.

B. Obtunded, comatose, or convulsing patient unless the airway is protected.


Technique

bowel preparation solution (polyethylene glycol)

2 L/h by gastric tube (children: 500 mL/h or 35 mL/kg/h), until rectal effluent is clear

Enhanced Elimination

Urinary manipulation

Hemodialysis

Hemoperfusion

Peritoneal dialysis

Continuous renal replacement therapy

Repeat-dose activated charcoal

Urinary manipulation

Forced diuresis

Alkalinization

sodium bicarbonate: 1-2 mEq/kg IV bolus or

3-4 mEq/kg IV infusion over 1 hour

Keep urine pH 7.5-8.5


Repeat-dose activated charcoal

20–30 g or 0.5–1 g/kg every 2–3 hours

interrupting enterohepatic or enteroenteric recirculation of the drug or toxin

Disposition of the Patient

Emergency department discharge or intensive care unit admission?

Psychosocial evaluation

Acetaminophen

Toxic dose

Acute ingestion

>200 mg/kg in children or 6-7 g in

adults

Chronic toxicity

>200 mg/kg within 24-hr period

>150 mg/kg/d (or 6 g/d) x ≥2 d

>100 mg/kg/d (or 6 g/d) x ≥3 d

Diagnosis

many clinicians routinely order acetaminophen levels in all overdose patients regardless of the history of substances ingested

Diagnosis

Specific levels

1. acute overdose: 4-hour postingestionacetaminophen level

Obtain a second level at 8 hours if the 4-hour

value is borderline or if delayed absorption is

anticipated.

2. The nomogram should not be used to assess chronic or repeated ingestions.

Diagnosis

Other useful laboratory studies

electrolytes

glucose

BUN, creatinine

liver transaminases, bilirubin

PT/INR

Treatment

Emergency and supportive measures

Specific drugs and antidotes


ABC

Observe 4-6 hour


Acute single ingestion

Above the “possible toxicity” line

NAC

Maximum benefit if start within 8-10 hr

Extended-release tablets

Repeat the serum acetaminophen level at 8 &

12 hr





Duration of NAC treatment

If evidence of liver injury develops, NAC is

continued until liver function tests are

improving.

Decontamination

Activated charcoal

Gastric lavage

Enhanced elimination

Hemodialysis

effectively removes acetaminophen from the

blood

not generally indicated because antidotal

therapy is so effective

considered for massive ingestions with very

high levels (eg, >1000 mg/L) complicated by

coma and/or hypotension

Organophosphorus and Carbamate Insecticides

Clinical presentation


Clinical presentation

Nicotinic effects

muscle weakness and tremors/fasciculations

Central nervous system manifestations

agitation, seizures, and coma

Diagnosis

Specific levels

RBC AChE (red blood cell acetylcholinesterase)

PChE (plasma pseudocholinesterase)

blood, urine, gastric lavage fluid, and excretion for specific agents and their metabolites

Diagnosis

Other useful laboratory studies to consider

ABG

pulse oximetry

ECG

electrolytes, glucose, BUN, creatinine, lactic acid, CK, lipase and LFT

CXR

Treatment




ABC

Observe asymptomatic patients for ≥8–12 hours


atropine

2-5 mg IV initially, and double the dose administered every 5 minutes until respiratory secretions have cleared


Pralidoxime

Loading dose (30-50 mg/kg, total of 1–2 g in adults) over 30 minutes, followed by a continuous infusion of 8-20 mg/kg/h

continue 2-PAM for 24 h after the patient becomes asymptomatic, or at least as long as atropine infusion is required

not recommended for carbamateintoxication

if the exact agent is not identified and the patient has significant toxicity, pralidoxime should be given empirically

Decontamination

Skin and mucous membranes

Ingestion

activated charcoal

gastric lavage

Enhanced elimination

not indicated

Take home message

A: airway

B: breathing

C: circulation

D: decontamination

E: enhance elimination

Reference

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Documents

Toxicology