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Electrolyte Abnormalities

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Hyperkalemia

  • Definition:

    • Mild: 5.5-6.5
    • Moderate: 6.5 - 8
    • Severe: >8

  • Contributing Factors:

    • Renal Disease
    • Drugs (ACEi, NSAIDS, K-sparing diuretics, digoxin, B-Blockers)
    • Succinylcholine (raises K by 0.5-1 acutely)
    • Acidosis
    • Hemolysis
    • Rhabdomyolysis
    • Administration of dantrolene and verapamil concurrently
    • Hyponatremia, hypocalcemia
    • Old pRBCs

  • Signs and Symptoms:

    • Cardiac conduction system abnormalities, including cardiac arrest and dysrhythmias (usually requires K > 6). Classically associated with administration of succinylcholine to paralyzed or burn patients
    • At K > 7, may have ascending paralysis that progresses to flacid paralysis and respiratory arrest

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  • Treatment:

    • Reverse membrane effects with Calcium
    • Transfer extracellular K+ into cells with Bicarbonate (50-100 mEq over 5-10 min), Insulin (10-15 units) + Glucose (25g), and Beta 2 Agonists (albuterol)
    • Remove potassium from body (Kayexelate, proximal or loop diuretics, dialysis).

  • Anesthetic considerations

    • Consider canceling elective cases if K>5.5
    • Avoid Succinylcholine
    • Monitor for EKG changes
    • Avoid hypoventilation (respiratory acidosis)
    • Treat acidosis
    • Consider NS instead of LR
    • Monitor for increased sensitivity to muscle relaxants

Hypokalemia

  • Definition:

    • Mild: 3.1-3.5
    • Moderate: K < 3 w/PACs
    • Severe: K< 3 w/ PVCs

  • Preoperative Causes:

    • GI Losses
    • Lasix
    • Magnesium Deficiency

  • Intraoperative Causes:

    • Alkalosis
    • Insulin
    • Hypothermia

  • Signs and Symptoms:

    • Acute Hypokalemia causes hyperpolarization of cardiac cells, leading to ventricular escape activity, re-entrant phenomena, ectopic tachycardias and delayed conduction.
    • PACs, PVCs, SVTs (esp. A fib,/A flutter)
    • Metabolic alkalosis
    • Autonomic Lability
    • Weakness, ↓ DTRs
    • Ileus
    • Digoxin toxicity
    • Enhanced response to muscle relaxants

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  • Treatment

    • Chronic Hypokalemia:

    • 1 mEq/L of K = 300-600 mEq total body deficit.

    • Acute Hypokalemia:

    • Likely redistribution phenomenon
    • Reverse underlying cause (e.g. alkalemia 2/2 mechanical hyperventilation)

  • Anesthetic Considerations:

    • Consider cancelling elective cases if K<3-3.5 (depending on chronicity of defect).
    • Monitor EKG for changes.
    • KCL if arrhythmias develop
    • Avoid hyperventilation (respiratory alkalosis)
    • Consider reducing dose of muscle relaxant 25-50%

Hypercalcemia

  • Contributing Factors:

    • Hyperparathyroidism
    • Malignancy
    • Immobilization
    • Acute Renal Failure
    • Drugs (Thiazide diuretics, lithium)

  • Signs and Symptoms

    • EKG Changes (short QT)
    • Hypertension
    • Polyuria

  • Treatment

    • Hydration
    • Dialysis if severe/non-responsive

  • Anesthetic Considerations:

    • Consider cancelling elective cases
    • Avoid acidosis (reduces Ca2+/Albumin binding)
    • Check serial K+ and Mg2+

Hypocalcemia

  • Preoperative Causes:

    • Hypoparathyroidism
    • Renal Failure (↓Vitamin D)
    • Sepsis
    • Magnesium Deficiency (Decreased end-organ response to PTH)

  • Intraoperative Causes:

    • Alkalosis (increased Ca-Albumin binding)
    • Massive pRBC binding (due to citrate binding)
    • Drugs (heparin, protamine, glucagon)

  • Signs and Symptoms:

    • EKG (prolonged QT, Bradycardia)
    • Hemodynamics (vasodilation, hypotension, decreased myocardial contractility, LV failure)
    • Respiratory (Laryngospasm, stridor, bronchospasm, respiratory arrest)
    • Neuro (cramps, tetany, ↑DTR, perioral numbness, seizures)

  • Treatment:

    • Calcium Gluconate - 1 g = 45 mEq elemental Ca2+ (do not give with bicarb; will precipitate)
    • Replace Magnesium

  • Anesthetic Considerations

    • Avoid alkalosis
    • Monitor paralysis with muscle relaxants

Hypermagnesemia

  • Contributing Factors:

    • Renal Failure
    • Hypothyroid

  • Signs and Symptoms

    • EKG (widened QRS, Prolonged PR interval, Bradycardia)
    • Hemodynamics (vasodilation, hypotension, myocardial deprssion)
    • Neuro (↓DTR, sedation, weakness, enhanced NM blockade)

  • Treatment

    • Hydration
    • Ca administration

  • Anesthetic Considerations

    • Vigilance for EKG changes
    • Consider reducing dose of muscle relaxants 25-50%

Hypomagnesemia

  • Contributing Factors

    • GI/Renal losses
    • Beta Agonists (cause intracellular shift)
    • Drugs (diuretics, theophylline, aminoglycosides)

  • Signs and Symptoms

    • Usually asymptomatic alone, but symptomatic in combination with induced hypokalemia, hypocalcemia, phyophosphatemia
    • EKG (prolonged QT, PACs, PVCs, A Fib)
    • Neuro (neuromuscular excitability, AMS, seizures)

  • Treatment

    • Replace with MGSO4 to MG2+ > 2
    • Watch for hypotension and arrhythmias with rapid administration.

  • Anesthetic Considerations

    • EKG monitoring
    • Check for coexistant electrolyte deficiencies.