HYPOKALEMIA

Hypokalemia describes low potassium levels in the blood. Less than 3.5 mEq/L of serum potassium is the most typical electrolyte abnormality. Your body needs potassium to function properly. The foods you eat provide potassium for your body.

CAUSES

1. Extra-renal causes: Inadequate dietary intake, diarrhea, vomiting, and redistribution (e.g., as a result of insulin administration, epinephrine injection)

2. Renal causes

a) Drug-induced renal losses: 

—Loop diuretics

—Penicillin

—Aminoglycosides

—Amphotericin B

b). Hormone-induced renal losses: Can occur as a result of primary adrenal adenomas, adrenal hyperplasia, ectopic adrenocorticotropic hormone syndrome, renin-secreting tumors, renal artery stenosis, and malignant hypertension

c) Renal tubular acidosis, Bartter syndrome, or chronic magnesium depletion can also lead to hypokalemia.

CLINICAL FEATURES

1. Symptoms:

—Paresthesias

—Constipation

—Weakness/fatigue

—Excessive thirst

—Excessive urination

—Fainting /lightheadedness

2. Examination findings:

—Areflexia

—Arrhythmias

—Ileus

—Orthostatic hypotension

—Paralysis

EVALUATION

1. Laboratory studies should include a serum electrolyte panel; serum BUN, creatinine, creatinine phosphokinase, phosphate, magnesium, and glucose levels; and urinalysis.

a) Creatinine phosphokinase levels in the serum may be high.

b) Urinalysis: The urine specimen may be dipstick-positive for red blood cells. Myoglobin may be seen in a formal urinalysis, which is consistent with rhabdomyolysis.

2. Electrocardiography: ECG findings include T-wave flattening or inversion, U waves, ST-segment depression, premature ventricular contractions, and a wide QRS complex.

THERAPY

1. Potassium replacement

a) If the serum potassium level is higher than 2.5 mEq/L and there are no abnormalities on the electrocardiogram (ECG), 40 to 80 mEq of potassium chloride should be given every day until the imbalance is resolved, with no more than 40 mEq given in a single dosage.

b) For severe hypokalemia, defined as a potassium level of less than 2.5 mEq/L, 10 mEq of potassium chloride are infused hourly through intravenous piggyback in 50–100 mL of 5% dextrose in water or normal saline for 3–4 hours.

—No more than 40 mEq of potassium should ever be put in a single liter of intravenous fluid, and no more than 10 mEq should be given per hour.

—Continuous cardiac monitoring is required.

2.Magnesium replacement with 2 g of magnesium sulfate in 50 mL of 5% dextrose in water administered over 20 minutes may be necessary.

3.Phosphate replacement: Potassium phosphate may be used instead of potassium chloride if the serum phosphate level is low. The 2.5 mg/kg daily dosage is advised.

DISPOSITION

Admission

—Patients with serum potassium concentrations of less than 2.5 mEq/L require admission to the hospital.

—Patients with malignant cardiac dysrhythmias, digitalis toxicity, profound weakness with impending respiratory failure, rhabdomyolysis, hepatic encephalopathy, or a serum potassium level of less than 2.0 mEq/L require admission to the intensive care unit.

Discharge: Patients with mild hypokalemia (serum potassium concentration = 2.5 to 3.5 mEq/L) can usually be managed as outpatients with gradual oral potassium repletion, provided they do not have ECG abnormalities, or profound muscular weakness, ileus, or other serious effects. Patients who are discharged on oral supplementation should have a follow-up appointment within 48 to 72 hours.