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Abstract: TH-PO374

Urinary Potassium Excretion Rate in Hypokalemic Periodic Paralysis: Spot vs. 24-Hour Urine

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Sung, Chih-Chien, Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
  • Chen, Chien-Chou, Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
  • Lin, Chin, School of Medicine, National Defense Medical Center, Taipei, Taiwan
  • Hsu, Yu-Juei, Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
  • Lin, Chien-Ming, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
  • Lin, Shih-Hua P., Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
Background

Hypokalemic periodic paralysis (HypoKPP) with acute hypokalemia and muscle paralysis is a potentially life-threatening emergency requiring rapid diagnosis and management. The role of timely spot versus 24 hour urine for urine K+ excretion rate in the diagnostic and therapeutic value of HypoKPP have not well evaluated.

Methods

HypoKPP patients with the exclusion of other non-HypoKPP causes and incomplete urine collection were consecutively enrolled over 5 years. Spot and 24 hour urine collection for urine K+ and other electrolytes excretion rate, and clinical characteristics including K+ supplementation to achieve recovery were examined. Spot urine K+ excretion was calculated by transtubular potassium concentration gradient (TTKG) and potassium-creatinine ratio (K+/Cr). Balanced K+ was defined as (supplemental K+-24 hour urine K+ excretion). Patients with K+ deficit was defined as positive balanced K+.

Results

Sixty-two HypoKPP patients (age 35.5 ± 10.4 year-old) including thyrotoxic periodic paralysis (TPP) (n=50), sporadic periodic paralysis (SPP) (n=9), and others (n=3) had hypokalemia (serum K+ 2.2 ± 0.5 mmol/L) and received K+ supplementation (77.0±45.3 mmol) to achieve recovery. All of them had a higher 24 hour urine K+ excretion (61.7 ± 34.2 mmol/day > 20 mmol/day), but their TTKG (< 3, 64% of them) or K+/Cr (< 0.18 mmol/L/mg/dl, 84% of them) were often lower. Despite acute hypokalemia without K+ deficit, thirty-eight patients (61%) with a positive balanced K+ balance had significantly lower serum K+ (2.1±0.5 vs 2.4±0.4 mmol/dL, p=0.013), needed more supplemental K+ (96.1±43.6 vs 46.7±28.8 mEq, p<0.001), and exhibited a slower increase in serum K+ concentration during K+ supplementation than those without K+ deficit (n=24).

Conclusion

To evaluate urine K+ excretion rate, timely spot urine is superior to 24 hour urine, which helps reveal the underlying subclinical K+ deficit in HypoKPP patients.