Watch out for Lithium!

We recently had a case involving high serum lithium concentration. I wanted to recap some of the main points with respect to this...

Lithium Poisoning

Lithium- it is rapidly absorbed by the GI tract soon after oral administration with peak blood levels being reached in 1-2 hours after ingestion of immediate release (IR) products, and later (i.e. 4-6h) after sustained release products

·      It’s a small molecule with no protein or tissue binding and is therefore amendable to hemodialysis

·      It is excreted almost entirely by the kidneys! It is freely filtered but >60% is reabsorbed in the proximal tubules!

    What can increase Lithium absorption (i.e. increase serum level)?

·      Volume depletion, renal impairment/AKI

o   i.e. GI loss (gastroenteritis), diuretic use, AKI (i.e. NSAIDs, volume loss or other nephrotoxic drugs, ACEi/ARB)

o   Reduction in effective circulating volume (i.e. heart failure, ascites)

o   Elderly: lower GFR and reduced volume of distribution (have reduction in total body water and lean body mass)

Clinical Presentation:

·      Can be acute or chronic

Acutely, focus on the history if the patient is stable

·      PMHx, Meds, Dehydration/recent illness, type of lithium (IR, SR), infectious symptoms, co-ingestants, nephron-toxic meds

·      Symptoms: nausea, vomiting, diarrhea, palpitations, inquire about pre-syncope or syncope; neurological symptoms (develop late in acute poisoning as there is time for drug absorption into the CNS)—patients describe feeling agitated, confused, a bit sluggish; can also have tremor (coarse), fasciculations or myoclonic jerks, seizure, encephalopathy

Labs:

·      Obtain Serum Lithium concentration, CBC, Electrolytes, renal function (Cr and urea);

o   Lithium can elevate WBC count

o   Normal therapeutic lithium level is 0.8-1.2 mmol/L

o   Na: nephrogenic diabetes insipidus is a complication of chronic lithium use

·      Extended Lytes

o   Calcium abnormalities can occur

·      TSH: can have associated hypo- or hyperthyroidism

·      Check Serum Blood Glucose

·      Acid-base disorder: not typical; if present, consider co-ingestants

o   Toxicology screen (urine), salicyclate, acetaminophen level

·      12 lead ECG: can appreciate cardiac arrhythmia, hypotension, sinus node dysfunction, bradycardia, inverted T-waves (reversible!)

·      Beta-hcg if child-bearing age

Treatment: start with ABCs and ensure the patient is stable!

Specific treatment: IVF to maintain adequate renal function and replace losses if recent GI loses

·      Hydration: IVF (i.e. 0.9NS), watch the Na

·      GI Decontamination: oral activated charcoal does NOT prevent absorption of lithium (which is charged); thus, it has NO role in the management of an isolated lithium ingestion

·      Whole Bowel Irrigation with PEG may be effective in those with large acute ingestions (especially if it was a SR product)

·      Hemodialysis: Lithium can be dialyzed! Treatment of choice for severe toxicity

o   i.e. Lithium concentration >4 mmol/L

§  or >2.5 mmol/L with signs of significant toxicity (i.e. seizures, depressed mental status, cannot tolerate IV fluid hydration secondary to profound CHF, etc)

§  CALL NEPHRO IF IN DOUBT!