Abstract
Hypokalemic paralysis is a rare but potentially life-threatening condition characterized by acute onset of muscle weakness due to significantly low serum potassium levels. While it can arise from various etiologies, certain medications such as loop diuretics and beta-agonists can precipitate this condition. We discuss a case of hypokalemic paralysis induced by the concurrent use of furosemide (Lasix) and salbutamol, highlighting the underlying mechanisms, clinical features, diagnostic approach, and management strategies.
Introduction
Potassium plays a vital role in maintaining neuromuscular function. A drop in extracellular potassium can lead to muscle membrane hyperpolarization, resulting in muscle weakness or paralysis. Diuretics like furosemide, which increase renal potassium excretion, and beta-2 agonists like salbutamol, which promote intracellular shift of potassium, are known to precipitate hypokalemia. When used together, these medications can act synergistically to cause significant hypokalemia, leading to acute flaccid paralysis.
Pathophysiology
- Furosemide (Lasix) is a potent loop diuretic that inhibits the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending limb of the loop of Henle. This results in increased excretion of sodium, chloride, and potassium, contributing to hypokalemia through renal losses.
- Salbutamol, a beta-2 adrenergic agonist, activates adenylate cyclase, increasing intracellular cAMP. This promotes Na⁺/K⁺ ATPase activity, causing potassium to shift from the extracellular to the intracellular space, exacerbating hypokalemia.
The combination of these two drugs can cause a rapid and profound decline in serum potassium, particularly in patients with poor dietary intake, chronic illness, or pre-existing electrolyte disturbances.
Clinical Presentation
- Sudden onset of flaccid muscle weakness, often symmetrical
- Lower limb weakness more pronounced than upper limbs
- Absence of sensory deficits
- Hyporeflexia or areflexia
- In severe cases, respiratory muscle involvement or cardiac arrhythmias
Case Illustration
Patient: 60-year-old male with a history of congestive heart failure and asthma
Medications: Furosemide 40 mg BID and frequent nebulizations with salbutamol
Presentation: The patient developed acute bilateral lower limb weakness with difficulty standing and walking. There was no history of trauma, fever, or sensory loss.
Vitals: HR 110 bpm, BP 100/60 mmHg, RR 22/min
Neurological exam: Flaccid paralysis in both lower limbs, muscle power 2/5, hyporeflexia
Lab results:
- Serum potassium: 2.1 mmol/L
- ECG: Flattened T waves, presence of U waves
Diagnosis: Hypokalemic paralysis secondary to diuretic and beta-agonist use
Diagnostic Workup
- Serum electrolytes: Focus on potassium, magnesium, calcium
- ECG: For arrhythmias and signs of hypokalemia (e.g., U waves, T wave flattening)
- ABG: To rule out metabolic alkalosis
- Thyroid function tests: Rule out thyrotoxic periodic paralysis
- Renal function tests: To evaluate kidney contribution to potassium loss
Management
Immediate goals:
- Potassium replacement:
- IV potassium chloride in symptomatic or severe cases
- Oral supplementation for milder forms
- Continuous ECG monitoring during IV replacement
- Stop or reduce offending agents:
- Discontinue/reduce furosemide
- Limit use of salbutamol, switch to anticholinergics if possible
- Address underlying conditions:
- Optimize heart failure management
- Review asthma treatment plan
- Monitor:
- Serial potassium levels
- Cardiac rhythm
- Renal function
Prognosis
With prompt recognition and treatment, hypokalemic paralysis is reversible, and most patients recover fully within hours to days. However, delays in treatment can result in respiratory compromise, fatal arrhythmias, and prolonged hospital stay.
Prevention
- Regular monitoring of electrolytes in patients on diuretics or beta-agonists
- Use of potassium-sparing diuretics when appropriate
- Patient education on symptoms of hypokalemia
- Avoid unnecessary overuse of beta-agonists, especially in elderly or comorbid patients
Conclusion
Hypokalemic paralysis is a rare but serious complication of combined Lasix and salbutamol therapy. Awareness of this potential interaction, early recognition of symptoms, and appropriate management can prevent severe outcomes. A multidisciplinary approach, including regular monitoring and judicious drug use, is essential for at-risk populations.