A 38-year-old man with bipolar I disorder, currently manic with psychotic features, has been hospitalized for 3 weeks. He is agitated, grandiose, and refusing food and fluids. Trials of lithium (level 0.9 mEq/L), valproate (level 85 µg/mL), and risperidone 6 mg/day have failed to achieve mood stabilization. He remains at high risk of self-harm. His wife consents to ECT. Before the first session, the patient's serum sodium is 132 mEq/L (normal 135–145), potassium is 3.2 mEq/L (normal 3.5–5.0), and magnesium is 1.6 mg/dL (normal 1.7–2.2). What is the MOST appropriate management before proceeding with ECT?

Explanation

## Electrolyte Abnormalities and ECT Safety **Key Point:** Electrolyte imbalances — particularly hypokalaemia, hypomagnesaemia, and hyponatraemia — significantly increase the risk of cardiac arrhythmias during and after ECT and MUST be corrected before proceeding. ### Mechanism of Risk Electrolyte abnormalities affect cardiac electrophysiology: | Electrolyte | Abnormality | ECT-Related Risk | |---|---|---| | **Potassium** | Hypokalaemia (K⁺ 3.2) | ↑ Risk of ventricular arrhythmias, prolonged QT, torsades de pointes; succinylcholine-induced hyperkalaemia may be blunted | | **Magnesium** | Hypomagnesaemia (Mg 1.6) | ↑ Risk of arrhythmias; cofactor for K⁺-ATPase; deficiency impairs repolarization | | **Sodium** | Hyponatraemia (Na⁺ 132) | ↑ Risk of seizure, cerebral oedema, altered mental status; may lower seizure threshold unpredictably | **High-Yield:** The combination of **hypokalaemia + hypomagnesaemia + hyponatraemia** creates a "perfect storm" for perioperative cardiac complications during ECT. This patient is at **HIGH RISK** of malignant arrhythmia. ### Corrective Actions Required 1. **Potassium supplementation:** Target K⁺ ≥3.5 mEq/L (preferably 4.0–4.5) - IV KCl if urgent; oral if time permits - Recheck level before ECT 2. **Magnesium supplementation:** Target Mg ≥1.8 mg/dL - IV MgSO₄ or oral magnesium glycinate - Recheck level before ECT 3. **Sodium correction:** Target Na⁺ ≥135 mEq/L - If hyponatraemia is SIADH-related (common in mania), fluid restriction + hypertonic saline if severe - If volume-depleted, normal saline - Gradual correction (avoid osmotic demyelination) 4. **Recheck ECG** after correction to ensure QTc normalizes **Clinical Pearl:** Succinylcholine causes a transient rise in serum potassium (0.5–1.0 mEq/L). In a patient with baseline hypokalaemia, this may paradoxically worsen the arrhythmia risk by creating a transient hyperkalaemic state. Correcting baseline K⁺ before ECT mitigates this risk. [cite:Kaplan & Sadock 20e Ch 35] ### Why This Patient Cannot Proceed Immediately - **Hypokalaemia alone** is a relative contraindication to ECT; combined with hypomagnesaemia and hyponatraemia, it becomes an absolute contraindication until corrected. - **Succinylcholine interaction:** Hypokalaemia + succinylcholine → unpredictable cardiac effects. - **Seizure threshold:** Hyponatraemia may lower seizure threshold, complicating dose titration. - **Arrhythmia risk:** The anaesthetic state + muscle relaxant + electrical stimulus + electrolyte imbalance = high risk of ventricular fibrillation. **Mnemonic: K-Mg-Na BEFORE ECT** — Correct **K**alium, **Mg** (magnesium), and **Na**trium before proceeding with ECT.