Lithium toxicity

Background

• Toxicity most often involves a drug-drug interaction or decreased renal excretion
• Lithium levels are only helpful for chronic toxicity
• Pts die of respiratory failure or CV collapse

Precipitants

1. Overdose
2. Renal failure
3. Volume depletion
   1. Diuretic use, vomiting, diarrhea, diaphoresis, decreased oral intake
4. Hyperthermia
5. Infection
6. CHF
7. Surgery
8. Cirrhosis

Clinical Features

1. GI
   1. Usually first to develop
   2. N/V
   3. Diarrhea
   4. Generalized abd pain
2. CNS
   1. Usually develops as GI symptoms are abating; more common in chronic toxicity
   2. Tremor
   3. Muscle weakness
   4. Ataxia
   5. Stupor
   6. Seizure
   7. Coma
3. Cardiac
   1. Hypotension
   2. Conduction Abnormalities
   3. Ventricular dysrhythmias
   4. Prolonged QT, transient ST depression, TWI
4. Endocrine
   1. Hyper/Hypothyroidism or hyperparathyroidism
   2. Hypothyroidism most common
5. Renal
   1. Nephrogenic Diabetes Insipidus
      1. Can be seen mildly at therapeutic levels

Diagnosis

1. Lithium level
   1. Correlates better with chronic than acute toxicity
2. Chemistry
   1. Low or negative ion gap
   2. Elevated osmolar gap
3. ECG
   1. QT prolongation
   2. Diffuse TWI

level may be falsely elevated if placed in a green top tube due to the heparin lithium interaction

Treatment

1. GI decontamination
   1. Consider lavage for massive ingestions (>4gm) if can be performed w/in 1hr
   2. Activated charcoal is ineffective
2. Fluid resuscitation
   1. Average pt has Na/volume deficit; giving fluid helps reestablish normal Li excretion
      1. Give 2L NS bolus; then give 200mL/hr
3. Seizure
   1. Benzos are 1st line
   2. Phenobarbital is 2nd line
   3. Phenytoin is ineffective
4. Dialysis
   1. Indications:
      1. Li level >4 (acute overdose)
      2. Li level >3.5 (chronic toxicity)
      3. Little change in Li level after 6hr IVF
      4. Sustained Li level >1.0 after 36hr
      5. Baseline renal failure
      6. Ingestion of sustained-release preparations
   2. Goal:
      1. Li level <1
         1. Must monitor for up to 8hr following dialysis to ensure levels stay <1

Disposition

• Consider discharge for pts asymptomatic after 4-6hr obs
• Admit all pts w/ Li level >1.5
• Admit all pts w/ ingestion of sustained-release preparation (regardless of Li level)

See Also

• Toxicology (Main)

Source

• Tintinalli