Hyperkalemia

Symptoms occur when Serum Potassium > 6.0 to 6.5 meq/L
Neurologic Changes
1. Weakness
2. Paresthesias
3. Areflexia
4. Ascending paralysis
5. Respiratory Failure
Cardiovascular Changes
1. Bradycardia to Asystole or Ventricular Fibrillation
2. AV prolonged transmission to complete Heart Block

Chemistry Panel
1. Serum Potassium
2. Serum Electrolytes including serum bicarbonate
3. Renal Function tests (BUN, Creatinine)
Spot urine for Urine Potassium, Urine Sodium and Urine Creatinine
1. Fractional Excretion of Potassium
2. Transtubular Potassium Gradient
3. Urine Sodium <25 mEq/L suggests decreased distal renal flow
  1. See Hyperkalemia Causes
Other labs to consider (see evaluation below)
1. Serum Aldosterone
2. Serum renin

General
1. EKG changes occur when Serum Potassium >6.0 meq/L
  1. EKG may however be normal despite significant Hyperkalemia
  2. When significant EKG changes are present, pursue aggressive Hyperkalemia Management
2. Changes are listed in the classic, textbook description
  1. However, patient's EKG findings often fail to follow the typical pattern
Initial
1. T Waves peaked or Tented (increased amplitude) in V2, V3, II, III
Next
1. ST depression
2. First degree AV Block (PR Interval increases)
3. QT Interval shortening
Next (ominous harbinger)
1. QRS Duration widening (>110 msec)
2. Loss of P Wave (Junctional Rhythm)
3. Sine Wave appearance
4. New Bundle Branch Block
Final
1. Biphasic wave (sine wave) QRS and T fusion
2. Severe Bradycardia
3. Imminent Asystole, Ventricular Tachycardia or Ventricular Fibrillation
Changes exacerbated by
1. Hyponatremia
2. Hypocalcemia
3. Metabolic Acidosis
4. Hypermagnesemia
5. Chronic Renal Failure with frequent, recurrent Hyperkalemia
  1. Change from normal EKG to Cardiac Arrest may be rapid in these patients

Serious signs of Hyperkalemia present (EKG, symptoms)
1. Urgent Hyperkalemia Management
Consider Pseudohyperkalemia
1. Consider confirmatory testing (re-draw sample)
Consider exogenous source or transcellular shift
1. See Hyperkalemia Causes
2. Eliminate causative factors

Urine Sodium <25 mEq/L suggests decreased distal renal flow
Urine Sodium >25 mEq/L with normal serum Aldosterone
1. Primary tubular defects (e.g. RTA-4)
2. Obstructive uropathy
3. Tubular unresponsiveness to Aldosterone (e.g. SLE, Multiple Myeloma, Sickle Cell Anemia)
4. Medications (e.g. Potassium sparing Diuretics, Lithium, Trimethoprim)
Urine Sodium >25 mEq/L with low serum Aldosterone and normal serum renin
1. Primary Adrenal Insufficiency
2. Medications (Heparin, Cyclosporine, ACE Inhibitor, ARB)
Urine Sodium >25 mEq/L with low serum Aldosterone and low serum renin
1. Hyperglycemia
2. Primary renal tubular defects
3. Medications (e.g. NSAIDs, Beta Blockers)