Toxicology – Enhanced Elimination Techniques I

Enhanced elimination techniques are used in selected severe poisonings to increase removal of a toxicant from the body or temporarily support the patient while normal elimination occurs. Choice depends on the toxicant’s pharmacokinetics and the patient’s clinical condition.

Cardiopulmonary Bypass (CPB)

Mechanism of Action

Cardiopulmonary bypass primarily provides temporary circulatory and respiratory support rather than directly removing the poison.

By maintaining organ perfusion during otherwise refractory cardiovascular collapse, it can provide time for:

• Hepatic metabolism
• Renal elimination
• Redistribution of the toxicant
• Recovery from reversible cardiotoxicity

Modern extracorporeal support such as VA-ECMO has largely assumed this role in many severe poisonings.

Indications

May be considered for otherwise refractory cardiovascular collapse caused by a potentially reversible poisoning, particularly when conventional resuscitation has failed.

It has historically been reported in severe cardiotoxic drug poisonings such as:

• Flecainide
• Lidocaine and other local anesthetics

Limitations / Complications

• Requires specialized personnel and equipment
• Major vascular access is required
• Bleeding and anticoagulation complications can occur
• It does not necessarily provide substantial direct toxicant clearance

Key Point

Think of extracorporeal circulatory support as a way to “buy time” for recovery and endogenous drug elimination, rather than as a conventional dialysis technique.

Exchange Transfusion

Mechanism of Action

The patient’s blood is progressively removed and replaced with donor blood or blood components.

This can remove toxicants that are largely confined to the intravascular compartment and replace damaged blood cells.

Possible Indications

Rarely considered for:

• Severe methemoglobinemia refractory to standard therapy
• Selected severe poisoning in neonates or infants when other extracorporeal techniques are unsuitable
• Severe toxin-induced hemolysis in exceptional circumstances

Limitations / Complications

• Transfusion reactions
• Hypothermia
• Hypotension
• Hypocalcemia
• Coagulopathy
• Thrombocytopenia
• Infection and other transfusion-related complications

Key Point

Exchange transfusion is now an uncommon, specialized rescue technique and is most useful when the relevant toxicant or toxic effect is concentrated within the blood.

Hemodialysis

Mechanism of Action

Blood passes along a semipermeable membrane, allowing toxic substances to diffuse into the dialysate.

A toxicant is generally easier to dialyze when it has:

• Low molecular weight
• Low protein binding
• Small volume of distribution
• High water solubility

Modern high-flux dialysis can remove some substances that older dialysis systems handled poorly.

Important Dialyzable Poisons

Hemodialysis has an established role in selected severe poisonings involving:

• Methanol
• Ethylene glycol
• Lithium
• Salicylates
• Theophylline

It can also simultaneously correct:

• Severe metabolic acidosis
• Electrolyte abnormalities
• Fluid disturbances

Dialysis may occasionally be used for other toxicants, but increased clearance alone does not mean that dialysis improves clinical outcomes enough to justify the procedure.

Complications

• Hypotension
• Fluid shifts
• Electrolyte abnormalities
• Vascular-access complications
• Bleeding related to anticoagulation

Important Considerations

Some antidotes, including fomepizole, can themselves be removed during dialysis, so antidote regimens may require adjustment under specialist guidance.

After dialysis, the serum toxicant concentration may occasionally rebound because drug stored in tissues redistributes back into the bloodstream. Additional treatment may therefore be required.

Key Point

Hemodialysis is most useful when the poison remains substantially in the bloodstream and can readily cross the dialysis membrane.

Hemoperfusion

Mechanism of Action

Instead of relying primarily on diffusion across a membrane, hemoperfusion passes blood through a cartridge containing an adsorbent material, historically activated charcoal or resin.

The toxicant binds to the cartridge and is removed from circulation.

Potentially Suitable Toxicants

Hemoperfusion works best when a substance:

• Has a relatively small volume of distribution
• Has low endogenous clearance
• Can be effectively adsorbed by the cartridge

Historically important examples include:

• Theophylline
• Carbamazepine
• Phenobarbital

Limitations / Complications

• Thrombocytopenia
• Bleeding and anticoagulation complications
• Vascular-access complications
• Hypotension
• Possible rebound after treatment

Unlike hemodialysis, hemoperfusion does not effectively correct metabolic acidosis, electrolyte abnormalities, or fluid disturbances.

Current Role

Hemoperfusion is used much less frequently today because modern hemodialysis is more readily available and effective for many dialyzable poisonings.

Key Points

• CPB/VA-ECMO: supports circulation while the body clears the poison.
• Exchange transfusion: replaces circulating blood and is rarely used.
• Hemodialysis: removes small, water-soluble, relatively unbound toxicants and simultaneously corrects acid-base/electrolyte problems.
• Hemoperfusion: directly adsorbs circulating toxicants but has a more limited modern role.
• Decisions about extracorporeal treatment depend on the patient’s clinical severity as well as toxicant characteristics, rather than serum concentration alone.
• Early consultation with toxicology and nephrology/critical-care specialists is important when extracorporeal treatment may be required.

Cardiopulmonary bypass primarily provides temporary circulatory and respiratory support rather than directly removing the poison. By maintaining organ perfusion during otherwise refractory cardiovascular collapse, it can provide time for:  Hepatic metabolism Renal elimination Redistribution of the toxicant Recovery from reversible cardiotoxicity  Modern extracorporeal support such as VA-ECMO has largely assumed this role in many severe poisonings. Indications

May be considered for otherwise refractory cardiovascular collapse caused by a potentially reversible poisoning, particularly when conventional resuscitation has failed. It has historically been reported in severe cardiotoxic drug poisonings such as:  Flecainide Lidocaine and other local anesthetics  Limitations / Complications  Requires specialized personnel and equipment Major vascular access is required Bleeding and anticoagulation complications can occur It does not necessarily provide substantial direct toxicant clearance  Key Point

Think of extracorporeal circulatory support as a way to “buy time” for recovery and endogenous drug elimination, rather than as a conventional dialysis technique.

Exchange Transfusion Mechanism of Action

The patient’s blood is progressively removed and replaced with donor blood or blood components. This can remove toxicants that are largely confined to the intravascular compartment and replace damaged blood cells. Possible Indications

Rarely considered for:  Severe methemoglobinemia refractory to standard therapy Selected severe poisoning in neonates or infants when other extracorporeal techniques are unsuitable Severe toxin-induced hemolysis in exceptional circumstances  Limitations / Complications  Transfusion reactions Hypothermia Hypotension Hypocalcemia Coagulopathy Thrombocytopenia Infection and other transfusion-related complications  Key Point

Exchange transfusion is now an uncommon, specialized rescue technique and is most useful when the relevant toxicant or toxic effect is concentrated within the blood.

Hemodialysis Mechanism of Action

Blood passes along a semipermeable membrane, allowing toxic substances to diffuse into the dialysate. A toxicant is generally easier to dialyze when it has:  Low molecular weight Low protein binding Small volume of distribution High water solubility  Modern high-flux dialysis can remove some substances that older dialysis systems handled poorly. Important Dialyzable Poisons

Hemodialysis has an established role in selected severe poisonings involving:  Methanol Ethylene glycol Lithium Salicylates Theophylline  It can also simultaneously correct:  Severe metabolic acidosis Electrolyte abnormalities Fluid disturbances  Dialysis may occasionally be used for other toxicants, but increased clearance alone does not mean that dialysis improves clinical outcomes enough to justify the procedure. Complications  Hypotension Fluid shifts Electrolyte abnormalities Vascular-access complications Bleeding related to anticoagulation  Important Considerations

Some antidotes, including fomepizole, can themselves be removed during dialysis, so antidote regimens may require adjustment under specialist guidance. After dialysis, the serum toxicant concentration may occasionally rebound because drug stored in tissues redistributes back into the bloodstream. Additional treatment may therefore be required. Key Point

Hemodialysis is most useful when the poison remains substantially in the bloodstream and can readily cross the dialysis membrane.

Hemoperfusion Mechanism of Action

Instead of relying primarily on diffusion across a membrane, hemoperfusion passes blood through a cartridge containing an adsorbent material, historically activated charcoal or resin. The toxicant binds to the cartridge and is removed from circulation. Potentially Suitable Toxicants

Hemoperfusion works best when a substance:  Has a relatively small volume of distribution Has low endogenous clearance Can be effectively adsorbed by the cartridge  Historically important examples include:  Theophylline Carbamazepine Phenobarbital  Limitations / Complications  Thrombocytopenia Bleeding and anticoagulation complications Vascular-access complications Hypotension Possible rebound after treatment  Unlike hemodialysis, hemoperfusion does not effectively correct metabolic acidosis, electrolyte abnormalities, or fluid disturbances. Current Role

Hemoperfusion is used much less frequently today because modern hemodialysis is more readily available and effective for many dialyzable poisonings. Key Points  CPB/VA-ECMO: supports circulation while the body clears the poison. Exchange transfusion: replaces circulating blood and is rarely used. Hemodialysis: removes small, water-soluble, relatively unbound toxicants and simultaneously corrects acid-base/electrolyte problems. Hemoperfusion: directly adsorbs circulating toxicants but has a more limited modern role. Decisions about extracorporeal treatment depend on the patient’s clinical severity as well as toxicant characteristics, rather than serum concentration alone. Early consultation with toxicology and nephrology/critical-care specialists is important when extracorporeal treatment may be required.

Toxicology – Nontoxic Ingestion

Definition

A nontoxic ingestion is an exposure to a substance that, at the estimated dose and route involved, is not expected to produce clinically significant toxicity.

The term should be used cautiously because even normally harmless substances can cause problems after unusually large exposures or aspiration.

When an Exposure Can Be Considered Nontoxic

Before classifying an ingestion as nontoxic, confirm that:

• The exact product has been reliably identified.
• Only one substance is involved.
• The product is in its original container and has not been replaced or contaminated.
• The approximate amount ingested is known.
• The route of exposure is known.
• The patient has no symptoms or abnormal examination findings.
• Reliable observation and follow-up are available.

If these conditions cannot be established, the exposure should generally be approached as an unknown ingestion.

Clinical Features

By definition, a true nontoxic ingestion should not produce significant systemic toxicity.

Very large exposures can still cause:

• Nausea or GI discomfort
• Vomiting or diarrhea
• Mechanical airway obstruction
• Aspiration-related lung injury

Development of unexpected symptoms should prompt reconsideration of the original history and possible exposure to another substance.

Common Low-Toxicity Household Exposures

Examples that are often minimally toxic after small accidental ingestions include:

• Crayons and chalk
• Graphite from pencils
• Ballpoint pen ink
• Many soaps and shampoos
• Shaving cream
• Petroleum jelly
• White glue
• Play dough
• Silica gel packets
• Small amounts of many cosmetics and lotions
• Water-based or latex paints

However, the specific formulation and amount still matter. Products within the same general category can contain different ingredients.

Medication Exposures

Some medications or topical products have relatively low toxicity after a small, isolated accidental exposure, but medication ingestions should still be assessed according to the specific drug and dose.

Examples historically considered relatively low risk in limited exposures include:

• Some antacids
• Calamine lotion
• Zinc oxide
• Many water-soluble vitamins

Importantly, iron-containing vitamins are an exception and can cause serious poisoning.

Plant Exposures

Many household plants cause little or no systemic toxicity, but plant identification can be unreliable and toxicity varies among species.

For a substantial or uncertain plant ingestion, accurate identification and consultation with a poison center are preferable to relying on a general “nontoxic plant” list.

Diagnosis

History is the most important part of the assessment. Determine:

• Exactly what substance was accessible
• How much may have been taken
• When the exposure occurred
• Whether other medications or chemicals were accessible
• Whether any symptoms occurred and subsequently resolved
• Whether the original container or packaging is available

If the history reliably establishes a truly nontoxic exposure and the patient remains asymptomatic, laboratory testing is generally unnecessary.

Management

For a confirmed nontoxic ingestion:

• Provide observation and supportive care as appropriate.
• Do not induce vomiting.
• Gastrointestinal decontamination is generally unnecessary.
• Confirm uncertain products or exposures with a poison center.

If symptoms develop or the substance, dose, or circumstances are uncertain, reassess the case as a potential toxic or unknown ingestion.

Key Points

• “Nontoxic” depends on the substance, dose, route, and certainty of the history.
• Accurate product identification is essential.
• An asymptomatic patient with a clearly identified low-risk exposure usually does not require extensive testing.
• Unexpected symptoms should trigger evaluation for an alternative or additional exposure.
• Even low-toxicity substances can cause problems through aspiration, airway obstruction, or massive ingestion.
• Avoid relying on old blanket lists of “nontoxic” products because modern formulations can vary.

Toxicology – Button Battery Ingestion

Sources

Button or coin batteries are commonly found in:

• Toys
• Watches
• Hearing aids
• Remote controls
• Small electronic devices

Young children are at greatest risk because the batteries are small, shiny, and easy to swallow.

Typical Presentation

A toddler may swallow a button battery and initially appear completely well.

The most dangerous situation is when the battery becomes lodged in the esophagus.

Clinical Features

Symptoms may include:

• Drooling
• Coughing
• Vomiting
• Dysphagia
• Chest discomfort
• Refusal to eat

However, some children with an esophageal battery may initially have few or no symptoms.

Serious complications include:

• Deep esophageal burns
• Perforation
• Tracheoesophageal fistula
• Injury to major blood vessels
• Mediastinitis

Batteries lodged in the nose or ear can also cause rapid local tissue injury.

Mechanism of Action

The main injury is caused by an electrical current that generates hydroxide ions at the battery surface.

This creates a strongly alkaline environment and causes liquefactive necrosis.

Severe tissue injury can begin within only a few hours.

Diagnosis

Plain radiographs are used to determine:

• Whether a battery is present
• Its location
• Whether it is still in the esophagus

Button batteries can usually be distinguished radiographically from coins by their characteristic layered appearance.

Management

An esophageal button battery is an emergency and requires prompt endoscopic removal.

Important principles include:

• Rapid localization with imaging
• Immediate specialty consultation
• Urgent removal if lodged in the esophagus
• Monitoring for delayed complications after significant esophageal injury

Batteries that have already passed into the stomach or intestine often pass spontaneously, but management depends on factors such as symptoms, battery size, age, location, and evidence of GI injury.

Key Points

• Esophageal impaction is the major emergency.
• Serious tissue injury can occur rapidly, sometimes within about 2 hours.
• A child may appear well despite significant internal injury.
• Large lithium coin cells are especially concerning.
• Batteries beyond the esophagus are often managed expectantly if the patient is asymptomatic and the battery continues to progress.
• Button batteries in the ear or nose also require prompt removal because they can cause rapid liquefactive tissue damage.

Toxicology – Caustic Ingestion: Acidic Agents

Sources

Common acidic caustic substances include:

• Battery acid
• Rust removers
• Toilet bowl cleaners
• Metal and brick cleaners
• Other strong industrial or household acids

Typical Presentation

A child or adult with an acid ingestion may develop:

• Burning mouth or throat pain
• Drooling
• Painful swallowing
• Vomiting
• Chest or abdominal pain

Severe cases may progress to airway compromise or gastrointestinal perforation.

Clinical Features

Possible findings include:

• Oral burns
• Drooling
• Nausea and vomiting
• Hematemesis
• Dysphagia
• Odynophagia
• Dyspnea
• Chest pain
• Abdominal pain

Serious systemic complications can include:

• Hemolysis
• Metabolic acidosis
• Acute kidney injury
• Shock

Endoscopy may show patchy or “skip” areas of injury, so visible damage may not be continuous.

Mechanism of Action

Acids cause coagulative necrosis.

This leads to protein denaturation and formation of an eschar, which may limit deeper penetration to some extent compared with strong alkalis, although severe injury can still occur.

Management

Treatment is mainly supportive:

• Assess and protect the airway
• Monitor cardiovascular status
• Evaluate for perforation and major GI injury
• Check relevant laboratory studies in significant exposures
• Use imaging when perforation or other complications are suspected

Endoscopy is often performed in selected symptomatic patients after stabilization to determine the extent of injury.

Avoid:

• Inducing vomiting
• Gastric lavage
• Activated charcoal
• Attempting to neutralize the acid with an alkali

Neutralization can generate heat and worsen tissue injury.

Routine dilution with milk or water is not generally recommended without poison-center or specialist guidance, particularly once symptoms are present.

Key Points

• Acids classically cause coagulative necrosis with eschar formation.
• Severe injury can involve the esophagus, stomach, airway, and surrounding tissues.
• Do not induce emesis or attempt chemical neutralization.
• A relatively normal oral examination does not exclude serious internal injury.
• Airway compromise, perforation, acidosis, hemolysis, and renal injury are major complications.
• Corticosteroids are not routinely used solely to prevent strictures; their role depends on the specific clinical situation.

Toxicology – Caustic Ingestion: Alkaline Agents

Sources

Common alkaline caustic products include:

• Drain cleaners
• Lye
• Oven cleaners
• Ammonia-containing cleaners
• Some concentrated cleaning solutions
• Bleach, although household bleach is usually less corrosive than strong alkalis

Typical Presentation

A young child is found after getting into a household cleaner and develops:

• Coughing
• Sore throat
• Drooling
• Pain with swallowing

Severity depends on the concentration, amount, and duration of contact.

Clinical Features

Possible findings include:

• Oral or pharyngeal burns
• Drooling
• Nausea and vomiting
• Hematemesis
• Dysphagia
• Odynophagia
• Chest pain
• Abdominal pain
• Dyspnea or stridor

Serious complications include:

• Upper-airway edema
• Esophageal or gastric injury
• Perforation
• Mediastinitis or peritonitis
• Later esophageal stricture formation

Importantly, the absence of visible mouth burns does not exclude serious esophageal injury.

Mechanism of Action

Alkaline substances cause liquefactive necrosis and saponification of fats.

This allows deeper tissue penetration and can produce significant injury to the esophagus and surrounding structures.

Management

Initial priorities include:

• Airway assessment and protection
• Supportive care
• Evaluation for perforation or significant internal injury
• Early consultation with gastroenterology, surgery, and toxicology when severe exposure is suspected

Endoscopy is commonly used in selected symptomatic patients to assess the extent of injury, usually after stabilization and within an appropriate early time window.

Avoid:

• Inducing vomiting
• Gastric lavage
• Activated charcoal
• Attempting to neutralize the alkali with an acid

These measures can worsen tissue injury or increase aspiration risk.

Routine administration of milk or water after significant caustic ingestion is not generally recommended without poison-center or specialist guidance, especially once symptoms are present.

Key Points

• Alkalis cause liquefactive necrosis and can penetrate deeply.
• Drooling, dysphagia, odynophagia, chest pain, or respiratory symptoms suggest significant injury.
• A normal-looking mouth does not rule out esophageal burns.
• Do not induce emesis or attempt chemical neutralization.
• Airway compromise and GI perforation are the most dangerous early complications.
• Corticosteroids are not routinely recommended solely to prevent strictures; their use depends on the specific clinical situation.

Toxicology – Hydrocarbon Ingestion

Sources

Hydrocarbons are found in many fuels, solvents, and petroleum products. Examples include:

• Propane and butane
• Hexane and octane
• Gasoline
• Kerosene
• Motor oil

Typical Presentation

A person drinks a small amount of gasoline and immediately begins gagging and coughing. The main danger is often not absorption from the stomach, but aspiration into the lungs.

Clinical Features

Possible symptoms include:

• Coughing
• Gagging
• Vomiting
• Shortness of breath
• Hypoxia
• Altered mental status
• Syncope

Aspiration can cause:

• Chemical pneumonitis
• Pulmonary edema
• Respiratory distress

Inhalation of hydrocarbon vapors may also cause:

• CNS depression or intoxication
• Dizziness and impaired coordination
• Cardiac dysrhythmias

Repeated inhalational abuse can lead to chronic neurologic injury.

Mechanism of Action

Hydrocarbon toxicity depends greatly on the physical properties of the product.

Low-viscosity hydrocarbons spread easily and are more likely to enter the airway during swallowing or vomiting.

Once aspirated, they:

• Directly injure pulmonary tissue
• Disrupt surfactant
• Trigger inflammation and chemical pneumonitis

Some inhaled hydrocarbons can also sensitize the heart to catecholamines, increasing the risk of dangerous dysrhythmias.

Aspiration Risk

Aspiration risk is generally higher with low-viscosity hydrocarbons.

Examples:

• Gasoline and kerosene: relatively high aspiration risk
• Motor oil: lower aspiration risk because of higher viscosity

Management

Treatment is mainly supportive:

• Remove the patient from further exposure
• Support airway and breathing
• Provide supplemental oxygen if needed
• Monitor for respiratory deterioration

There is no specific antidote for hydrocarbon aspiration.

Inducing vomiting is avoided because it can increase the risk of aspiration. Activated charcoal is generally not useful for uncomplicated aliphatic hydrocarbon ingestion.

Key Points

• The major danger after ingestion is often aspiration, not systemic absorption.
• Low viscosity = higher aspiration risk.
• Chemical pneumonitis may develop after coughing or choking during ingestion.
• High-viscosity products such as motor oil usually pose less aspiration risk.
• Treatment is primarily supportive, with attention to respiratory symptoms and cardiac rhythm abnormalities.

Toxicology – Hydrofluoric Acid (HF) Exposure

Sources

Hydrofluoric acid is used in several industrial and commercial processes, including:

• Glass etching
• Semiconductor and computer-chip manufacturing
• Oil refining
• Chemical production
• Metallurgy
• Some rust removers and wheel-cleaning products

Typical Presentation

A worker exposed to HF develops severe, deep pain several hours after skin contact, despite relatively minor-looking surface burns.

Pain that seems out of proportion to the visible injury is an important clue.

Clinical Features

Skin exposure may cause:

• Severe burning or throbbing pain
• Tissue destruction that can extend deeply beneath the skin
• Delayed symptoms, particularly with more dilute solutions

Significant exposure can produce systemic electrolyte abnormalities, especially:

• Hypocalcemia
• Hypomagnesemia

These may cause:

• Muscle cramps or spasms
• Tetany
• Chvostek or Trousseau signs
• QT prolongation
• Ventricular dysrhythmias
• Cardiovascular collapse in severe poisoning

Inhalational exposure can also cause significant respiratory tract and pulmonary injury.

Mechanism of Action

HF toxicity is unusual because both components contribute to injury.

The hydrogen ion produces local corrosive damage, while absorbed fluoride ions penetrate deeply and bind calcium and magnesium.

This sequestration can cause profound electrolyte disturbances and disrupt cardiac electrical activity.

Management

HF exposure is a medical emergency. Initial treatment includes:

• Immediate removal from the source
• Prompt removal of contaminated clothing
• Copious water irrigation of exposed skin
• Early cardiac monitoring for significant exposures
• Serial monitoring of calcium, magnesium, potassium, and ECG findings

After initial decontamination, calcium gluconate is used to bind fluoride and limit ongoing tissue injury. The route of calcium treatment depends on the location and severity of exposure and should be directed by experienced clinicians or a poison center.

Severe exposures may require intensive treatment of electrolyte abnormalities, dysrhythmias, and respiratory complications.

Key Points

• Severe pain out of proportion to the visible burn is characteristic of HF exposure.
• HF can penetrate deeply even when the surface injury initially appears mild.
• Fluoride binds calcium and magnesium, potentially causing life-threatening electrolyte disturbances.
• Significant exposure can produce QT prolongation and dangerous ventricular dysrhythmias.
• Rapid decontamination and calcium-based treatment are central to management.
• Because deterioration can be delayed, significant HF exposure requires urgent medical evaluation and toxicology guidance.

Toxicology – Magnesium Toxicity

Sources

Hypermagnesemia may result from excessive exposure to magnesium-containing products such as:

• Magnesium sulfate
• Magnesium citrate
• Milk of magnesia
• Other magnesium-containing antacids or laxatives

Risk is increased in patients with renal impairment, because magnesium is primarily eliminated by the kidneys.

Typical Presentation

A patient receiving magnesium therapy, such as during treatment of preeclampsia, develops:

• Weakness
• Nausea
• Flushing
• Diminished reflexes
• Hypotension
• Bradycardia

Severe toxicity may progress to respiratory depression and cardiac conduction abnormalities.

Clinical Features

As magnesium levels rise, findings may include:

• Nausea and vomiting
• Flushing
• Thirst
• Generalized weakness
• Lethargy
• Decreased or absent deep tendon reflexes
• Hypotension
• Bradycardia
• Respiratory depression
• Prolonged cardiac conduction
• Wide QRS complexes
• Complete heart block
• Cardiac arrest in extreme cases

Loss of deep tendon reflexes is an important early bedside clue during magnesium therapy.

Mechanism of Action

Excess magnesium depresses neuromuscular and cardiac function.

It:

• Reduces acetylcholine release at the neuromuscular junction
• Interferes with calcium-dependent processes
• Alters sodium and potassium channel activity
• Slows cardiac conduction
• Produces peripheral vasodilation

Management

Treatment includes:

• Immediately stopping the magnesium source
• Airway and respiratory support when needed
• IV fluids and cardiovascular support
• Continuous ECG monitoring in significant toxicity

IV calcium, usually calcium gluconate, can temporarily antagonize the cardiac and neuromuscular effects of magnesium.

Patients with adequate renal function may eliminate excess magnesium with supportive care. Hemodialysis is particularly useful in severe toxicity or when renal failure prevents magnesium excretion.

Key Points

• Think of weakness + diminished reflexes + hypotension/bradycardia in a patient receiving magnesium.
• Renal failure greatly increases the risk of magnesium accumulation.
• Calcium antagonizes the physiologic effects of magnesium and is used for significant toxicity.
• Severe hypermagnesemia can cause respiratory failure and heart block.
• Magnesium-containing laxatives should be used cautiously in patients with impaired renal function.

 Toxicology – Thallium Poisoning

Sources

Thallium exposure may occur from:

• Certain industrial processes
• Some older rodenticides
• Fireworks or pyrotechnic materials
• Contaminated products
• Intentional poisoning

Historical medical uses are largely obsolete.

Typical Presentation

Thallium poisoning often begins with gastrointestinal symptoms, followed days later by characteristic neurologic and skin findings.

A classic clue is the combination of:

• Abdominal pain
• Painful peripheral neuropathy
• Hair loss

Clinical Features

Early findings

• Nausea
• Vomiting
• Abdominal pain
• Diarrhea
• Occasionally GI bleeding
• Tachycardia
• Hypertension
• Chest discomfort

Neurologic findings

• Painful paresthesias
• Peripheral neuropathy
• Headache
• Ataxia
• Visual disturbances
• Altered mental status
• Seizures in severe cases

Delayed skin and hair findings

• Alopecia, often developing days to weeks after exposure
• Scaling or abnormalities of the palms and soles
• Acneiform or pustular skin eruptions
• Abnormal nail growth

Mechanism of Action

Thallium behaves similarly to potassium and can enter cells through potassium transport pathways.

It interferes with:

• Potassium-dependent cellular processes
• Mitochondrial energy production
• Sulfhydryl-containing enzymes
• Protein and keratin synthesis

These effects help explain its prominent neurologic toxicity and characteristic abnormalities of the hair, skin, and nails.

Management

Treatment includes:

• Immediate removal from the exposure source
• Supportive care
• Management of seizures, cardiovascular instability, and electrolyte abnormalities
• Gastrointestinal decontamination in selected recent exposures

Prussian blue is the specific antidotal therapy. It binds thallium in the gastrointestinal tract and interrupts enterohepatic and enteric recycling, increasing fecal elimination.

Repeated-dose activated charcoal may also be considered in selected cases under toxicology guidance.

Extracorporeal removal may be considered in severe poisoning, particularly early in the course.

Key Points

• Think of GI symptoms + painful neuropathy + delayed alopecia.
• Thallium mimics potassium and disrupts mitochondrial and enzymatic function.
• Prussian blue is the key specific antidote.
• Hair loss is often delayed and may become a major diagnostic clue.
• Conventional chelators are generally not useful for thallium poisoning.

Toxicology – Arsenic Poisoning

Sources

Arsenic exposure may occur from:

• Contaminated groundwater or food
• Certain traditional or nonstandard medicines
• Some pesticides and industrial products
• Pigments and manufacturing processes
• Contaminated occupational environments

Inorganic arsenic is generally responsible for the most significant systemic toxicity.

Typical Presentation

A patient with substantial arsenic exposure may develop severe gastrointestinal illness followed by cardiovascular and neurologic toxicity. Chronic exposure can produce characteristic skin changes and a painful stocking-glove peripheral neuropathy.

A garlic-like odor on the breath has traditionally been described but is neither sensitive nor specific.

Clinical Features

Acute poisoning may cause:

• Severe nausea and vomiting
• Profuse watery diarrhea
• Abdominal pain
• Dehydration
• Tachycardia
• Hypotension and shock
• Altered mental status
• Seizures
• Peripheral neuropathy, sometimes developing after the initial illness
• Cardiac dysrhythmias and QT prolongation
• Cardiovascular collapse in severe cases

Chronic poisoning may cause:

• Hyperkeratosis, especially of the palms and soles
• Abnormal skin pigmentation
• Peripheral neuropathy
• Metabolic abnormalities, including increased risk of diabetes
• Cardiovascular disease
• Increased risk of several cancers, particularly skin, lung, and bladder cancers

Mechanism of Action

Arsenic disrupts cellular energy production. Inorganic arsenic can inhibit enzymes such as pyruvate dehydrogenase, interfering with formation of acetyl-CoA and ATP.

It can also impair:

• Oxidative phosphorylation
• Glucose metabolism
• Other essential enzyme systems

The result is widespread cellular dysfunction affecting the gastrointestinal, cardiovascular, neurologic, and other organ systems.

Management

Treatment includes:

• Immediate removal from the exposure source
• Aggressive supportive care
• IV fluids and cardiovascular stabilization
• Correction of electrolyte abnormalities
• ECG monitoring in significant acute poisoning

Chelation may be required for clinically important poisoning. Agents include:

• Dimercaprol (BAL) in selected severe acute cases
• Succimer (DMSA)
• DMPS, where available

Chelation decisions should be made with a medical toxicologist or poison center because the preferred agent depends on the type and severity of exposure.

Key Points

• Acute arsenic poisoning often begins with severe GI symptoms and can progress to shock, dysrhythmias, and neurologic injury.
• Painful stocking-glove neuropathy is an important clue.
• Chronic exposure can cause hyperkeratosis and characteristic pigmentation changes.
• Arsenic interferes with cellular energy production.
• Chronic inorganic arsenic exposure is associated with increased cancer risk.
• Groundwater contamination remains an important source of arsenic exposure worldwide.