Fluids, Electrolytes, Acid-Base Disorders, and Nutrition Support
Definition: Serum potassium less than 3.5 mEq/L, though most ICUs empirically prefer to keep
patients at 4.0 mEq/L or greater, if possible.
Signs and symptoms: Weakness, cramps, cardiac arrhythmias (ST depression, QT prolongation,
flat T wave, U wave). If severe hypokalemia (e.g., serum potassium less than 2 mEq/L): flaccid
paralysis, ileus.
Etiologies:
Inadequate intake (rare; kidneys can usually adapt)
ii.
Increased losses
| (a) | GI fluid losses (e.g., diarrhea, fistula, drainages) |
|---|---|
| (b) | Hypomagnesemia |
| (c) | Medications (diuretics, amphotericin B, mineralocorticoid excess, cisplatin, extended- |
spectrum penicillins such as piperacillin, ticarcillin)
| (d) | Polyuria (diabetes insipidus) |
|---|---|
| (e) | Renal potassium excretion (type I/distal and type II/proximal renal tubular acidosis) |
| (f) | Diabetic ketoacidosis |
iii.
Increased requirements (building of new muscle/tissue β refeeding syndrome)
iv.
Extracellular to intracellular shift
| (a) | Medications (Ξ²-adrenergic agonists, including albuterol, sodium bicarbonate or other |
|---|
alkalinizing agents; insulin)
| (b) | Acute alkalemia |
|---|---|
| (c) | Hypothermia |
| (d) | Pentobarbital |
| d. | Treatment: |
Treat, alleviate, or reduce the potential etiologies for hypokalemia, if possible.
ii.
Ensure that hypokalemia is not at least partly attributable to hypomagnesemia.
iii.
The estimated deficit should be replaced during a period of 1β3 days (depending on the extent
of deficit; the larger the deficit, the longer the repletion period) by giving boluses and increasing
the potassium content in intravenous fluids and/or PN formulation.
iv.
Enteral or oral potassium replacement is the preferred and safer route of delivery in
asymptomatic patients because of the time of absorption and feed-forward regulation of
extended release tablet or capsule (potassium chloride), oral solution (potassium chloride), and
effervescent tablet (potassium bicarbonate); the oral solution is limited by poor palatability
(preferred for administration via nasogastric/orogastric tube), and bicarbonate salt forms
may not be appropriate for patients with a significant metabolic alkalemia; administration
of potassium chloride liquid directly into the small bowel (by a jejunal or duodenal feeding
tube) should be avoided because of its osmolality, which can lead to abdominal cramping,
distension, and diarrhea.
Central administration of intravenous repletion doses of potassium chloride or potassium
phosphate is preferred. Potassium chloride can be given at 20 mEq/hour if the patient has
continuous electrocardiography (ECG) monitoring. Ten mEq/hour is safest if the patient is
asymptomatic.
vi.
Empiric intravenous potassium dosing. Institution or ICU-specific repletion protocols are
common and may need to be adjusted according to patient body size, renal function, ongoing
losses, and response to previous boluses. The following algorithm is an example of empiric
potassium repletion that is based on serum concentrations.