Toxicology

Question 1

Causes of toxic airway obstruction and symptoms ?

Answer 1

1) Toxic coma: may cause posterior displacement of the tongue
(1st
cause of death in impaired conscious level)
2) Foreign bodies aspiration (e.g., Button batteries, seeds as nut meg, castor oil seeds)
3) Mucosal swelling: hypersensitivity or corrosive irritation, or smoke inhalation
4) ↑↑ Secretions: organophosphorus insecticides.
—————————-
 Dyspnea
 Dysphonia
 Air hunger
 Hoarseness of voice
 Cyanosis
 Tachypnea
 Intercostal retraction

Question 2

General approach to pensioned patient

Answer 2

-Emergency stabilization
-Clinical evaluation
-Decontamination
-Elimination
-Antidotal therapy
-Supportive therapy

Question 3

Toxic causes of hypotension/shock and arrhythmias

Answer 3

 Excessive fluid loss: arsenic.
 Depression of myocardial contractility: tricyclic antidepressants.
 Post- arteriolar dilatation: iron.
 Hypoxia: carbon monoxide, cyanide.
—————
digitalis, theophylline, phenytoin, anti arrhythmic,
electrolyte imbalance.

Question 4

Treatment of hypotension/shock

Answer 4

Lower than 4 and 12 cmH2O (CVP IS 2 to 6 mmHg)
1) Fluid replacement therapy.
2) Vasopressor drugs as dopamine and noradrenaline.
3) Cardiotonic as digoxin.
4) Treatment of the cause and correction of complicationsas metabolic acidosis.

Question 5

Drugs that alter the content of consciousness

Answer 5

1. Anticholinergics as atropine.
2. Withdrawal syndromes as with alcohol and sedative hypnotics.
3. Drugs causing encephalopathy as lead and arsenic.
4. Hallucinogenic and designer drugs

Question 6

Clinical picture of qualitative impairment

Answer 6

(confusion and delirium):
1. In- alertness: the patient can’t repeat 5 digits.
2. Disorientation of persons, time and place.
3. Loss of short-term memory.
4. Delusions, illusions or hallucinations.
5. Dementia: 1, 2 are usually not present.

Treatment of the cause.
 Benzodiazepines &/ or major tranquilizers in severe cases.

Question 7

Causes of coma

Answer 7

1) Traumatic. (concussion &compression)
2) Medical as diabetic comas, cerebrovascular accidents, hepatic encephalopathy.
3) Toxic causes as:
 CNS depressants as alcohol and sedative- hypnotics.
 Hypoxic causes as carbon monoxide, organophosphates.
 Heavy metals.
 Narcotics.
 Causes of hypoglycemia as oral hypoglycemic toxicity.
 Causes of acid- base disorders as iron and salicylates.

Question 8

treatment of coma

Answer 8

 Stabilization, patent airway, O2 therapy, i.v line.
 All comatose patients should be given a triad of (Coma Cocktail)
1) naloxone,
2) Dextrose 50 or 25% &
3) thiamine (Coma Cocktail)
 Treatment of the cause.
 Supportive measures are very important to minimize complications in
comatose (see symptomatic & supportive therapy)

Question 9

Ways of removing ingested poison from GIT?

Answer 9

1. Gastric evacuation (emesis or gastric lavage).
2. Intra-gastric binding (single or multiple dose activated charcoal).
3. Speeding transit of toxins to decrease total absorption time(whole bowel irrigation or
   cathartics).
4. Endoscopic/surgical decontamination.

Question 10

Emesis by syrup of ipec (I/CI)

Answer 10

Considered in conscious patients presenting very shortly after
ingestion (<1 hour).

Not routinely administered in management of poisoned patients

Question 11

Gastric lavage (I/CI)

Answer 11

It may be useful within 4 hours of large, lethal doses of drug. However, the efficacy of gastric lavage decreases as the time between ingestion and treatment increases. AC is better.

Not used with corrosive, caustic, acids or petroleum ingestion.

Question 12

Activated charcoal (CI)

Answer 12

A super-heated carbonaceous material that works as a non specific adsorbent for most intoxicants. Treat an overdose.

Not used in:
 Patients who present when poison absorption is considered complete.
 Poisons poorly adsorbed to AC (e.g., cyanide, DDT, ethanol,methanol, heavy metals,
hydrocarbons, iodide, iron, and lithium).
 Patients whose risk of complications is un acceptably high (e.g.,aspiration).

Question 13

Whole bowel irrigation technique and (I/CI)

Answer 13

Enteral administration of a polyethylene glycol balanced electrolyte solution (PEG-ELS) in order to rapidly clean the GI tract and prevent absorption of toxin by decreasing transit time. By mouth in co-operative patients or naso-gastric tube.

Indication
 Ingested tablets that don’t bind well to charcoal (e.g., iron).
 Large ingestion of sustained released or enteri coated preparations.
 Patients with suspected drug concretions (pharmacobezoars)
 Body packers orstuffers with concurrent administration of AC to adsorb drug that may escape the ingested packets.
 Patients who have ingested toxic foreign bodies.

CI
 Unprotected airway.
 Gastrointestinal obstruction, absent bowel sound, or perforation.
 Recurrent, unstoppable vomiting.
Complications:
 Nausea, vomiting, bloating, and rectal irritation.
 Pulmonary aspiration

Question 14

Cathartics technique and (CI/C)

Answer 14

They are intended to decrease poison absorption by enhancing rectal evacuation of the poison-activated charcoal complex. The osmotic retention of fluid within the GI tract stimulates bowel motility and enhances expulsion of contents.

 Cathartics can’t be used as a mono-therapy and are suggested in a single dose as adjunct to AC to prevent constipation.

Contraindications:
 Intestinal obstruction, perforation, and ileus.
 Electrolyte imbalances.
 Hypotension.
 Magnesium cathartics should NOT be administered to patientswith renal failure.
Complications:
 Abdominal cramps, nausea, and vomiting.
 Excessive diarrhea and dehydration.
 Hypotension.
 Hypernatremia and hypermagnesemia (with magnesium cathartics).

Question 15

Endoscopy/surgery indication

Answer 15

It may be indicated only when a life-threatening intoxicant has been ingested and cannot be effectively removed by other less invasive methods.

Indications
Concretions.
 Lethal amounts of heavy metals, which can be visualized on abdominal radiograph and are
refractory to whole bowel irrigation or gastric lavage.
 Cocaine packets.

Question 16

Forced diuresis and pH alteration (I/CI/C)

Answer 16

indication
 Weak acid or weak alkali.
 Has low plasma protein binding.
 Has limited metabolism.
 Has adequate renal excretion.
 Has small volume of distribution.
Contraindication
1. shock,
2. renal failure,
3. heart failure,
4. Pulmonary edema.
Complication
 acid- base and electrolyte disturbances,
 fluid overload,
 pulmonary and / or cerebral edema.

Question 17

Hemodialysis (I/CI/C)

Answer 17

 Ingestion of a lethal dose of the toxin as salicylate, ethanol.
 Large dose of a toxin that is metabolized to a more toxic metabolite as methanol.
 Impaired normal excretion route as renal failure.
 Progressive clinical deterioration and the presence of complications as aspiration
pneumonia.
 Presence of abnormal vital signs not responding to supportive care as apnea, hypotension.

Contraindications:
 none dialyzable toxin,
 presence of antidote,
 cardiogenic shock,
 coagulopathy

Complications:
1. hypotension,
2. hypoxemia,
3. electrolyte imbalance,
4. vessel perforation,
5. pneumothorax,
6. bacteremia,
7. air embolism,
8. anaphylactic reactions,
9. infections as hepatitis C and AIDS.

Question 18

Hemoperfusion(I/C)

Answer 18

Indications:
 the same as hemodialysis but because the toxin passes directly on the adsorbent.
 Hemoperfusion can be done in toxins with:
 high molecular weight (MW),
 protein binding,
 poor water solubility.
Contraindications and complications:
 as hemodialysis with other complications as
 leucopenia,
 thrombocytopenia,
 and hypocalcemia.

Question 19

Peritoneal dialysis

Answer 19

Indications:
1. acute renal failure,
2. coagulopathy,
3. hemodialysis and hemoperfusion are not available or
contraindicated.
Complications:
 pain, , electrolyte imbalance . bacterial peritonitis, hemorrhage
 leakage, . pneumonia , pleural effusion.
 perforation of viscera

Question 20

Multiple dose AC

Answer 20

Indications:
1) Decontamination of the GIT:
 Drugs with enterohepatic recirculation as dapsone, theophylline, carbamazepine,
phenobarbitone.
 Slow release and enteric coated tablets.
2) Gut dialysis:
 In which the drug is adsorbed by activated charcoal while it isin the circulation across the
intestinal mucosa (the intestinal mucosa acts here as a barrier).
 For gut dialysis to be effective the drug must be: adsorbable, more water soluble, less
bound to plasma proteins, has low volume of distribution.
 Gut dialysis is effective for: aspirin, carbamazepine, theophylline, phenobarbitone,
atenolol B- blocker.

Disadvantages of MDAC: bad taste, vomiting, pulmonary aspiration, constipation,
GI obstruction.

Question 21

Exchange transfusion

Answer 21

Indications:
methemoglobinemia not responding to methylene blue,
severe iron toxicity.
It is usually done in young children.

Question 22

Hyperbaric oxygen (HBO) complications

Answer 22

Complications:
traumatic rupture of tympanic membrane,
acute sinusitis,
optic neuritis,
pneumothorax,
O2 toxicity,
seizures.

Question 23

Physical antidote techniques?

Answer 23

a) Adsorbing:
- Adsorption is the adhesion of particles of toxins to a surface.
-The main example is activated charcoal.
b) Demulcents: milk in cases of corrosives to coat and protect the mucosa.
c) Dissolving: 10% alcohol or olive oil for carbolic acid (phenol).

Question 24

Chemical Antidote techniques?

Answer 24

a) Neutralization: weak acids for strong alkalis and vice versa.
- Disadvantages: excessive heat production that may add to the destructive effect of the
corrosive.
b) Oxidation: K+ permanganate 1/5000 for white phosphorus.
c) Reduction: Na+ formaldehyde sulfoxylate for mercuric chloride.
d) Precipitation: tannic acid for alkaloids.

Question 25

Characters of the ideal chelating agent

Answer 25

 Highly soluble in water.
 Ability to penetrate to metal storage.
 The chemical affinity of the chelating agent to the toxic metal ion should be
higher than the affinity of the metal to the sensitive biological molecule.
 Forming complexes with metals that are non-toxic and easily excreted via the kidneys.
 Orally active.
 Doesn’t chelate body metals as calcium and zinc.
 Active at pH of body fluids.

Question 26

General care of the comatose patient?

Answer 26

 Airway protection, maintenance of adequate oxygenation, with the assistance of artificial ventilation.
 Intravenous hydration: use isotonic fluids.
 Nutrition (feeds via a nasogastric tube) and fluid balance.
 Care of the mouth and eyes (by taping the eyelids shut or by applying a lubricant).
 Care of pressure areas and skin (the patient must be turned every 1-2 hours to prevent pressure sores).
 Urinary catheterization.
 Monitoring of the Cardio-vascular system.
 Infection control.