This chapter will review the pharmacotherapy for management of fluid and electrolyte disorders according to The Society for Endocrinology Endocrine Emergency Guidance and other expert panel.
General overview ( tables 21.1, 21.2, and 21.3 )
| ELECTROLYTE | NORMAL SERUM CONCENTRATION | EXTRACELLULAR FLUID (mEq/L) | INTRACELLULAR FLUID (mEq/L) | DAILY REQUIREMENTS(g/day) |
| Sodium | 135–145 mEq/L | 142 | 10 | 1.2–1.5 |
| Potassium | 3.5–5.2 mEq/L | 4 | 140 | 2.3–3.4 |
| Chloride | 95–105 mEq/L | 103 | 4 | 1.8–2.3 |
| Bicarbonate | 24–32 mEq/L | 28 | 10 | N/A |
| Calcium | 8.5–10.5 mg/dL | 2.4 | — | 1–1.3 |
| Magnesium | 1.8–2.4 mg/dL | 1.2 | 58 | 0.2–0.4 |
| Phosphate | 2.5–4.5 mg/dL | 4 | 75 | 0.7–1.3 |
| SOLUTIONS | SODIUM (mEq/L) | POTASSIUM (mEq/L) | CHLORIDE (mEq/L) | BICARBONATE (mEq/L) | CALCIUM (mEq/L) | MAGNESIUM (mEq/L) | OSMOLALITY (mOsm/kg) |
| 5% Dextrose | — | — | — | — | — | — | 252 |
| 0.9% NaCl | 154 | — | 154 | — | — | — | 308 |
| 0.45% NaCl | 77 | — | 77 | — | — | — | 154 |
| 5% Dextrose-0.225% NaCl | 34 | — | 34 | — | — | — | 320 |
| 3% NaCl | 513 | — | 513 | — | — | — | 1026 |
| Lactated ringer | 130 | 4 | 109 | 28 | 2.7 | — | 274 |
| PlasmaLyte, normosol | 140 | 5 | 98 | 27 | — | 3 | 294 |
| DRUG | MECHANISM |
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Hypernatremia
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Defined as a serum sodium level >145 mEq/L
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Clinical manifestations: lethargy, irritability, restlessness, muscle spasticity, hyperreflexia, seizures, coma, and death
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Gross estimation of free water deficit (Adrogue-Madias) = 0.6 × wt (kg) × [serum sodium/140 – 1]; use 0.5 × wt (kg) for women. The Adrogue-Madias equation often underestimates total body water deficit.
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Dehydration: free water boluses using 200–300 mL q4–6h via feeding or suction tube. If no enteral route, intravenously (IV) as below
Management of acute hypernatremia (hypernatremia ≤48 h): Rare
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Goal: decrease serum Na by 1–2 mEq/L per hour with max 10 mEq/L per 24 h
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5% dextrose (D5W) IV @3–6 mL/kg/h until serum Na 145 mEq/L; monitor serum Na q2–3h
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Once serum Na 145 mEq/L, decrease D5W to 1 mL/kg/h until serum Na 140 mEq/L
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Central diabetes insipidus: add desmopressin
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Initial therapy: 5 to 10 mcg of the nasal spray every night (qhs)
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0.1 or 0.2 mg tablet qhs (may result in inadequate response)
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1 mcg subcutaneous q12h (if intranasal or oral route not feasible)
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2 mcg IV q12h (if inadequate response to subcutaneous)
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Management of chronic hypernatremia (hypernatremia >48 h): Common
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D5W IV @1.35 mL/h × weight (kg) to lower serum Na by max 10 mEq/L per 24 h
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If concurrent hypovolemia: 0.225% NaCl @1.8 mL/kg/h
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If concurrent hypovolemia and hypokalemia: 0.225% NaCl with KCl 40 meq/L @2.7 mL/kg/h
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Monitor serum sodium concentration q4–6h until goal achieved then q12–24h
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If hypernatremia due to correction of severe hyperglycemia and hypovolemia (e.g., diabetic ketoacidosis, hyperosmolar hyperglycemic state): 0.45% NaCl 6–12 mL/kg/h to lower serum Na by max 10 mEq/L per 24 h
Hyponatremia
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Defined as a serum sodium level <135 mEq/L
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Clinical manifestations: lethargy, disorientation, restlessness, muscle weakness, depressed reflexes, seizures, coma, and death
Treatment of acute or severe hyponatremia ( table 21.4 )
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Hypervolemic: fluid and sodium restriction, diuretics
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Hypovolemic and low urine sodium: administer 0.9% NaCl IV or NaCl tablets 1–2 g three times daily
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Euvolemic:
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Consider syndrome of inappropriate antidiuresis, secondary adrenal insufficiency, severe hypothyroidism, or drug induced
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Fluid restriction and 0.9% NaCl IV
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If above measures inadequate, consider vasopressin receptor antagonists ( Table 21.5 )
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