Lithium Toxicity with Severe Hyponatremia
This patient has lithium toxicity precipitated by severe hyponatremia (Na 125), and lithium must be discontinued immediately while the hyponatremia is urgently corrected.
Critical Diagnosis
The presentation of pressured speech and mania in a patient on lithium with Na 125 mmol/L represents a dangerous clinical scenario. While the manic symptoms might suggest inadequate treatment of bipolar disorder, the severe hyponatremia creates a high risk for lithium toxicity even at therapeutic lithium levels 1. The FDA label explicitly contraindicates lithium in patients with sodium depletion, stating "the risk of lithium toxicity is very high in such patients" 1.
Immediate Management Algorithm
Step 1: Discontinue Lithium Immediately
- Lithium should be stopped regardless of serum lithium level 1
- Hyponatremia impairs lithium excretion and dramatically increases toxicity risk 2, 3
- The manic symptoms may paradoxically worsen initially but preventing life-threatening toxicity takes priority
Step 2: Assess Symptom Severity for Hyponatremia Treatment
Severe symptoms (mental status changes, seizures, coma):
- Transfer to ICU 4
- Administer 3% hypertonic saline as 100-150 mL IV bolus 4, 5
- Target: Increase Na by 4-6 mEq/L over first 1-2 hours 4, 5
- Critical limit: Do not exceed 8 mEq/L correction in 24 hours 4
- Monitor Na every 2 hours 4
Mild/moderate symptoms (nausea, headache, weakness):
- Transfer to intermediate care 4
- Fluid restriction to 1L/day 4
- Monitor Na every 4 hours 4
- Consider oral salt supplementation 4
Step 3: Determine Volume Status
The hyponatremia etiology guides ongoing management:
- Hypovolemic: Normal saline infusions 6, 5
- Euvolemic (likely SIADH): Fluid restriction as primary therapy; consider urea or vaptans if refractory 5, 7
- Hypervolemic: Treat underlying cause (heart failure, cirrhosis) plus fluid restriction 6, 5
Step 4: Monitor for Lithium Toxicity
Check serum lithium level and watch for:
- Neurological symptoms (tremor, confusion, ataxia)
- GI symptoms (nausea, vomiting, diarrhea)
- Renal function deterioration
If lithium level is toxic or symptoms develop, consider hemodialysis 1.
Critical Pitfalls to Avoid
Do not continue lithium "because the patient is manic": The combination of lithium and severe hyponatremia is explicitly contraindicated 1. Lithium toxicity can cause seizures, coma, and death 1.
Do not correct sodium too rapidly: Overcorrection risks osmotic demyelination syndrome, which can cause permanent neurological damage 4, 5, 8. If you exceed 8 mEq/L in 24 hours, consider administering desmopressin or hypotonic fluids to re-lower sodium 7, 8.
Do not assume therapeutic lithium levels are safe: Toxic symptoms can occur within the therapeutic range when hyponatremia is present 2.
Subsequent Psychiatric Management
Once sodium normalizes (>135 mEq/L) and lithium is cleared:
- Consider alternative mood stabilizers (valproate, carbamazepine, antipsychotics)
- Lithium can theoretically be restarted only if: (1) psychiatric indication is life-threatening, (2) patient failed all other options, (3) sodium disorder is corrected and cause identified, and (4) daily lithium levels with extreme caution are feasible 1
- Hospitalization is mandatory if lithium is reconsidered 1
The priority is preventing mortality from lithium toxicity and hyponatremic encephalopathy—psychiatric symptoms are secondary concerns until these life-threatening conditions are addressed.