PSEUDOHYPERKALEMIMA

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PSEUDOHYPERKALEMIMA

• A Review Article Discussing the Causes and
  Implications of Pseudohyperkalemia.

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CASE

• 61 y/o female no significant PMHx and normal PE
• presents with recurrent episodes of hyperkalemia.
  
• Values of serum potassium ranged from 5.0 to
  7.2.
• Normal BUN and Cr GFR 69ml/minute.
• Normal Plasma Renin Activity and Serum
  Aldosterone
• Concentration.
• Normal 24 hour urine excretion of K, Na and
  Ca.
• Normal EKG

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THESE DATA INDICATE A NORMAL

• (1) RENIN-ANGIOTENSIN-ALDOSTERONE
• SYSTEM
• (2) INTAKE OF Na, K, AND Ca
• (3) ACID BASE REGULATION
• (4) PRESERVED RENAL FUNCTION

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Factors Resulting in Elevated K Levels

• (1) Leaving Tourniquet on for Extended Time
• (2) Excessive Fist Clenching
• (3) Arm in Upward Position
• (4) Betadine
• (5) Inappropriate Order of Draw
• (6) Drawing Above IV Site
• (7) Benzalkonium Heparin for Coating Catheters
• (8) Vigorously Mixing Tubes
• (9) Collection Technique
• (10) Chilling Blood
• (11) Re-centrifuging
• (12) Pneumatic Tube Systems
• (13) Thrombocytosis and Myeloproliferative
  Disorders
• (14) Dehydration
• (15) Familial Pseudohyperkalemia

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Pseudohyperkalemia Resulting From Repeated
Fist-Clenching During Phlebotomy.
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• Fist clenching is used to make veins more
  prominent.
• May increase serum potassium in healthy subjects
  by 1-2 mmol/L.
• - A case report in New England Journal of
  Medicine by BR Don shows, the application of
  tourniquet alone had no effect on K, however,
  fist clenching increased levels by 1.1.

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• In a study by JJ Brown, a study of 1,865
  patients investigated for hyperaldosteronism
  demonstrated that
• -69 of those with a postive diagnosis had a
  normal serum K.
• -11 when blood was drawn without stasis or
  fist clenching.

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Re-centrifugation May Elevate Potassium
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• - In a study by Hira and co-workers,several
  patients were found to have hyperkalemia only at
  a certain hospital
• Blood samples collected and centrifuged 20 to 60
  minutes later. Then, re-centrifuged prior to
  transport.
• - In a time-series study of 5,700 specimens
  shown that delayed re-centrifugation led to an
  erroneous increase in K of upto 2.77 mmol.L.

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Familial Psdeudohyperkalemia
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• Leaky Red Blood Cell
• Cells show a temperature-dependent loss of K
  from RBCs when stored at room temperature
• Marginal increase in permeability at room
  temperature.