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Hypokalemic periodic paralysis
From WikEM
Contents
Background
- Autosomal dominant channelopathy[1]
- Acquired hypokalemia from barium poisoning, hyperthyroidism, renal disorders, and GI losses[2]
- Most first attacks happen by age 16
- Young males, Asian
- There is no decrease in total body potassium. Blood potassium level is normal between attacks.[3]
- Associations
- Thyrotoxicosis
- Steroids
- ETOH
- Renal disease
Clinical Features
Symptoms
- Muscle weakness or paralysis with associated hypokalemia (though potassium levels can be normal)
- Sometimes painful though often painless
- Weakness can be from hand to leg to complete paralysis
History
- Strenuous exercise
- High carbohydrate meal
- High sodium meals
- Sudden changes in temperature
- Emotional stress
- Attacks can last several hours to several days
Physical Exam
- Reflexes are decreased or absent[4]
- Shoulders and hips, are involved more often than the arms and legs.[4]
- There is flaccid paralysis rather than hypertonia
- There should not be myoclonus or spasticity
Differential Diagnosis
Weakness
- Neuromuscular weakness
- UMN:
- Spinal cord disease:
- Infection (Epidural abscess)
- Infarction/ischemia
- Trauma (Spinal Cord Syndromes)
- Inflammation (Transverse Myelitis)
- Degenerative (Spinal muscular atrophy)
- Tumor
- Peripheral nerve disease:
- Guillain-Barre syndrome
- Toxins (Ciguatera)
- Tick paralysis
- DM neuropathy (non-emergent)
- NMJ disease:
- Muscle disease:
- Rhabdomyolysis
- Dermatomyositis
- Polymyositis
- Alcoholic myopathy
- Non-neuromuscular weakness
- Can't miss diagnoses:
- ACS
- Arrhythmia/Syncope
- severe infection/Sepsis
- Hypoglycemia
- Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
- Hypokalemic periodic paralysis
- Thyrotoxic periodic paralysis
- Respiratory failure
- Emergent Diagnoses:
- Symptomatic Anemia
- Severe dehydration
- Hypothyroidism
- Polypharmacy
- Malignancy
- Other causes of weakness and paralysis
- Acute intermittent porphyria (ascending weakness)
- Can't miss diagnoses:
Evaluation
Labs
- Chemistry (potassium)
ECG Findings
- Sinus bradycardia
- ECG signs of hypokalemia may be present but not always diagnostic[5]
- U waves in leads II, V-2, V-3, and V-4
- Progressive flattening of T waves and depression of ST segment
- Prolongation of the PR and QT intervals
Management
- Replace potassium appropriately - do not try to correct to normal level as once the muscles release potassium you will likely overcorrect
- Long Term Treatment:
- Should be initiated by primary physician but often includes eating a low carbohydrate diet and avoiding alcohol
- Medications to increase potassium: Acetazolamide, Spironolactone, Potassium tablets
Disposition
- Can be discharged from ED after potassium repletion and resolution of symptoms
- Consider admission if patient remains symptomatic
See Also
References
- ↑ June-Bum Kim, MD, PhD. Channelopathies. Korean J Pediatr. 2014 Jan;57(1):1-18 Full Text
- ↑ Ahlawat SK and Sachdev A. Hypokalemic paralysis. Postgrad Med J. 1999; 75(882):193-197.
- ↑ Mount DB, Zandi-Nejad K. Disorders of potassium balance. In Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 17.
- ↑ 4.0 4.1 Chinnery PF. Muscle diseases. In: Goldman L, Schafer AI, eds. Goldman’s Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 429.
- ↑ Hypokalemic Periodic Paralysis. Periodic Paralysis International. http://hkpp.org/physicians/hypokalemic_pp
