General Management of Acute Overdosage

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General Management of Acute Overdosage

Rapid intervention is essential to minimize morbidity and mortality in an acute toxic ingestion. Institute measures to prevent absorption and hasten elimination as soon as possible; however, symptomatic and supportive care takes precedence over other therapy. It is assumed that basic life support measures, (eg, cardiopulmonary resuscitation [CPR]) have been instituted. Specific antidotes are discussed in the overdosage section of individual or group monographs. The discussion below outlines procedures used in the management of acute overdosage of orally ingested systemic drugs.

Advanced Life Support Measures:

Adequate airway: Adequate airway must be established and maintained, generally via oropharyngeal or endotracheal airways, cricothyrotomy, or tracheostomy.

Ventilation: Ventilation may then be performed via mouth-to-mouth insufflation, hand-operated bag (ambu bag), or by mechanical ventilator.

Circulation: Circulation must be maintained.

Hypotension: If hypotension/hypoperfusion occurs, place the patient in shock position (head lowered, feet elevated); specific therapy may include:
Establish IV access and initiate IV fluids (eg, 0.9% or 0.45% Saline, Lactate Ringer's, Dextrose). A maintenance flow rate is generally 100 to 200 ml/hour; individualize as necessary.
Plasma, plasma protein fractions, whole blood, or plasma expanders may be required.
Severe hypotension may required judicious use of cardiovascular active agents. The most commonly recommended agents are dopamine, dobutamine, and norepinephrine.
Arrhythmia: Treatment is dictated by the offending drug.
Hypertension: Sometimes severe, hypertension may occur. (See Nitroprusside and Diazoxide, Parenteral in the Agents for Hypertensive Emergencies section.)
Seizures: Simple isolated seizures may require only observation and supportive care. Repetitive seizures or status epilepticus require therapy. Give IV diazepam or lorazepam followed by fosphenytoin and/or phenobarbital. Pancuronium may also be considered.

Reduction of Drug Absorption:

Gastric emptying: Gastric emptying is generally recommended as soon as possible; however, this is generally not very effective unless employed within the first 1 to 2 hours after ingestion. Syrup of ipecac and gastric lavage are the 2 most commonly employed methods for gastric emptying.

Syrup of ipecac: This is the preferred method of choice outside the hospital. Do not induce vomiting if the medication is caustic or a petroleum or if the patient is in a coma or having seizures. Syrup of ipecac takes 20 to 30 minutes to work. Consider gastric lavage if response is needed immediately. The following dosage is recommended for syrup of ipecac and may be followed by a glass of water. A second dose may be given if results do not occur within 20 to 30 minutes.
6 months to 1 year – 10 ml
1 year to 12 years – 15 ml
> 12 years – 30 ml
Gastric lavage: This is indicated in the comatose patient or for those in whom syrup of ipecac failes to produce emesis. Gastric lavage is immediate and does not have a delay reaction, and is preferred over forced emesis. Airway protection via endotracheal intubation is appropriate for the patient without a gag reflex or comatose patients. Position the patient on left side, face down and use a large bore tube. Instill warm water or saline 300 to 360 ml for adults. Avoid water for infants and children; use warm saline or 5% to 6% polyethylene glycol solution. Give until lavage solution becomes clear. Add charcoal before removing the tube.

Adsorption: Adsorption, using activated charcoal alone or after completion of emesis or lavage, is indicated for virtually all significant toxic ingestions. It adsorbs a wide variety of toxins and there are no contraindications. However, it adsorbs many orally administered antidotes as well, so space dosage properly. Give an adult 50 to 100 g of activated charcoal mixed in 240 ml of water; the pediatric dose is 1 g/kg, or 25 to 50 g in 120 ml of water.

Cathartics: Cathartics increases the elimination of charcoal-poison complex. Generally using a saline or osmotic cathartic (eg, magnesium sulfate or citrate or sorbital) with 3 ml/kg of a 35% to 75% solution of sorbitol has the most rapid effect.

Whole bowel irrigation (WBI): Whole bowel irrigation utilizes rapid administration of large volumes of lavage solutions, such as PEG. The dose is 4 to 6 L over 1 to 2 hours for adults and 0.5 L/hr for children. It may be most useful to remove iron tables, sustained-release capsules or cocaine-containing condoms or balloons.

Elimination of Absorbed Drug:

Interruption of enterohepatic circulation: Interruption of enterohepatic circulation by “gastric dialysis” uses scheduled doses of activated charcoal for 1 to 2 days. Gastric dialysis not only interrupts the enterohepatic cycle of some drugs, but also creates an osmotic gradient, drawing drug from the plasma back into the GI lumen where it is bound by the charcoal and excreted in the feces.

Diuresis: Diuresis may be effective as identified in the individual drug monographs.

Forced diuresis: Occasionally useful, forced diuresis may cause volume overload or electrolyte disturbances. Forced diuresis is useful for phenobarbital, bromides, lithium, salicylate, or amphetamines overdosages. Do not use for tricyclic antidepressants, sedative-hypnotics, or highly protein-bound medications. The most common agents employed are furosemide and osmotic diuretics with mannitol.
Alkaline diuresis: Alkaline diuresis promotes elimination of weak acids (eg, barbiturates, salicylates) and is accomplished by the administration of IV sodium bicarbonate.
Acid diuresis: Acid diuresis may be indicated in overdoses with weak bases (eg, amphetamines, fenfluramine, quinine) but use with caution in patients with renal or liver disease. It is usually accomplished with oral or IV ascorbic acid or ammonium chloride.

Dialysis: Dialysis is indicated in a minority of severe overdosage cases. Drug factors that alter dialysis effectiveness include volume of distribution, drug compartmentalization, protein binding, and lipid/water solubility.

Hemodialysis: Hemodialysis may be used after an overdosage and when the patient is having complications (eg, severe metabolic acidosis, electrolyte imbalances, renal failure).
Peritoneal dialysis: Peritoneal dialysis is even less effective than hemodialysis.
Charcoal hemoperfusion: Charcoal hemoperfusion is useful when a drug can be adsorbed by charcoal (eg, theophylline, barbiturates).

Poison Control Center: Consultation with a regional poison control center is highly recommended.