Management of Hyperkalemia

               R. S. Cohen

INDICATION

Management of hyperkalemia involves treatment of elevated serum potassium levels in patients in the neonatal intensive care unit (NICU), particularly those dependent on parenteral fluids.

Clinical Findings

Initially, neonates should be in good fluid and electrolyte balance and thus have normal serum potassium concentrations. Exceptions can and do occur rarely but need to be recognized in a timely fashion.

1. Maternal history suggestive of abnormal fluid and electrolyte status

    a. Renal diseases with abnormal electrolytes

    b. Diuretic therapy

    c. Malnutrition or very abnormal diet

    d. Oligohydramnios

2. Physical findings suggestive of abnormal electrolyte balance

    a. Edema/anasarca

    b. Ascites, abdominal/flank masses

    c. Ambiguous genitalia

Confirmatory/Baseline Tests

The usual neonate, even the very premature patient, does not need serum electrolytes measured immediately after birth. Initially, a neonate’s electrolytes and creatinine should reflect the mother’s status. Patients with a history or physical findings like those mentioned in the discussion of clinical findings may need an electrolyte panel early in life. Note that in the face of normal placental and maternal renal function, a totally anephric neonate may have normal (ie, maternal) serum creatinine and potassium levels at birth.

1. Serum electrolytes should be followed closely in all low birth weight (LBW) and sick patients in the NICU. Serum potassium levels in neonates tend to be somewhat higher than in older children and adults and not uncommonly will be in the range of 5 to 6 mEq/L. However, levels greater than 6.5 should be watched closely, and those greater than 7 are associated with poor outcomes.

2. Hyperkalemia results in specific recognizable changes in the electrocardiogram (ECG) in the following progression:

    a. Tall, peaked T waves

    b. Prolonged P-R interval

    c. Widened QRS

    d. Bradycardia with abnormal QRS axis

    e. Ventricular fibrillation

Differential Diagnosis/Diagnostic Algorithm

Hyperkalemia in the neonate can be thought of in 4 categories:

1. Nonoliguric hyperkalemia (NOHK) occurs in the first few days of life in very low birth weight infants in the presence of normal urine output. It is caused by the transfer of potassium from the very high intracellular concentration (∼150 mEq/L) to the relatively low concentration in extracellular fluids. Factors that contribute to this potassium flux include

    a. Immaturity of the energy-dependant Na⁺-K⁺ ion pump, which may be worsened by perinatal hypoxia or hypoglycemia

    b. Acidosis resulting in increased H⁺-K⁺ exchange across cellular membranes

    c. Epidemiologic findings associated with NOHK, including

        (1) Birth weight less than 1000 g

        (2) Fetal distress

        (3) Metabolic acidosis

        (4) Hyperglycemia (caused by osmolality and low insulin)

        (5) Polyuric renal failure

        (6) No antenatal steroid treatment

    d. Tissue breakdown (eg, hemolysis, necrosis) is a minor contributor¹ to NOHK. Indeed, severe hemolytic disease of the newborn does not commonly result in life-threatening hyperkalemia. Rare situations exist in which tissue breakdown may result in hyperkalemia:

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