How do you manage fluid and electrolytes in patients?

Fluid and Electrolyte Management in Patients

The most effective management of fluid and electrolytes requires understanding normal physiologic requirements, recognizing disease-specific alterations, and implementing targeted replacement strategies based on careful monitoring of clinical and laboratory parameters.

Basic Fluid Requirements

Fluid requirements should be calculated based on weight and adjusted for clinical circumstances:

• Adults (18-60 years): 35 ml/kg body weight 1
• Adults (>60 years): 30 ml/kg body weight 1
• Children: Use Holliday-Segar formula 1:
  • First 10 kg: 100 ml/kg/day (4 ml/kg/hour)
  • Second 10 kg: 50 ml/kg/day (2 ml/kg/hour)
  • Each kg above 20 kg: 25 ml/kg/day (1 ml/kg/hour)

Assessment of Hydration Status

Clinical Signs of Dehydration

• Confusion, non-fluent speech, extremity weakness
• Dry mucous membranes, dry/furrowed tongue, sunken eyes
• Postural pulse change ≥30 beats/minute or severe postural dizziness 2
• Decreased skin turgor, oliguria

Laboratory Assessment

• Serum electrolytes with calculated anion gap
• Serum osmolality, renal function tests
• Acid-base status 2
• Urine specific gravity and osmolality

Electrolyte Management

Sodium Management

Hyponatremia

• Isotonic/hypovolemic: 0.9% NaCl infusion at 4-14 ml/kg/hour based on severity
• Hypotonic/euvolemic: Fluid restriction (<1 L/day)
• Severe symptomatic (<120 mEq/L with neurological symptoms): 3% hypertonic saline at 1-2 ml/kg/hour
  • Correction rate should not exceed 8-10 mEq/L in 24 hours or 0.5-1 mEq/L/hour 2

Hypernatremia

• Determine if acute (<48 hours) or chronic
• Replace water deficit gradually
• For chronic hypernatremia, correct no faster than 0.5 mEq/L/hour 3

Potassium Management

Hypokalemia

• Mild (3.0-3.5 mEq/L): Oral potassium chloride 40-80 mEq/day in divided doses
• Moderate (2.5-3.0 mEq/L): Oral potassium chloride 80-120 mEq/day in divided doses
• Severe (<2.5 mEq/L): IV potassium at 10-20 mEq/hour (not exceeding 40 mEq/hour in critical situations) with continuous cardiac monitoring 2
• Monitor for digitalis toxicity when correcting hypokalemia in patients on digoxin 4

Hyperkalemia

Treatment steps:

1. Eliminate potassium-containing foods and medications
2. IV calcium gluconate if no risk of digitalis toxicity
3. IV dextrose with insulin (10% dextrose solution with 10-20 units insulin per 1,000 mL)
4. Sodium bicarbonate if acidosis present
5. Consider exchange resins (Kayexalate), hemodialysis, or peritoneal dialysis 4
   • Caution: Intestinal necrosis has been reported with Kayexalate 5

Phosphate Management

• Mild deficiency (2.0-2.5 mg/dL): Oral phosphate 1000-2000 mg/day in divided doses
• Moderate deficiency (1.0-2.0 mg/dL): Oral phosphate 2000-3000 mg/day in divided doses
• Severe deficiency (<1.0 mg/dL): IV phosphate 0.08-0.16 mmol/kg over 4-6 hours 2

Magnesium Management

• Mild deficiency (1.2-1.7 mg/dL): Oral magnesium oxide/citrate 400-800 mg/day in divided doses
• Moderate deficiency (0.8-1.2 mg/dL): Oral magnesium 800-1600 mg/day in divided doses
• Severe deficiency (<0.8 mg/dL): IV magnesium sulfate 1-2 g over 1 hour, followed by 0.5-1 g every 6 hours 2

Special Clinical Scenarios

Acute Kidney Injury (AKI)

• Avoid medications that may worsen kidney function or electrolyte disturbances
• Adjust medication doses based on kidney function
• Consider non-calcium-based phosphate binders in consultation with nephrology 2
• Monitor electrolytes closely, especially in patients requiring renal replacement therapy

Diabetic Ketoacidosis (DKA)

• Initial fluid therapy: 0.9% NaCl at 15-20 ml/kg/hour during first hour
• Subsequent fluid: 0.45% NaCl at 4-14 ml/kg/hour if corrected sodium normal/elevated; 0.9% NaCl if corrected sodium low
• Add potassium (2/3 KCl and 1/3 KPO₄) at 20-30 mEq/L once renal function is assured 1

Heart Failure

• Reduce water requirements in congestive heart failure
• Monitor patients sensitive to sodium intake for signs of fluid overload
• Use diuretics (e.g., furosemide) when there is evidence of systemic volume overload
• Caution with diuretics in patients with cirrhosis as sudden fluid/electrolyte changes may precipitate hepatic coma 6

Refeeding Syndrome

• Start nutritional support at low levels (approximately 10 kcal/kg/day)
• Provide generous electrolyte supplementation
• Monitor phosphate, potassium, and magnesium closely 2

Monitoring and Follow-up

• Check electrolytes within 24-48 hours after initiating replacement therapy
• Monitor vital signs and clinical status daily
• Arrange close follow-up, ideally within 24-48 hours 2
• Educate patients on signs requiring immediate medical attention:
  • Confusion or altered mental status
  • Inability to maintain oral intake
  • Severe weakness or cardiac symptoms
  • Seizures or muscle spasms

Common Pitfalls to Avoid

1. Correcting electrolyte abnormalities too rapidly, especially sodium imbalances which can lead to osmotic demyelination syndrome
2. Overlooking ongoing losses when calculating replacement needs
3. Failing to adjust fluid requirements in special populations (elderly, cardiac/renal disease)
4. Not considering medication effects on fluid and electrolyte balance
5. Inadequate monitoring during correction of severe imbalances

Remember that oral replacement is preferred whenever possible, and the route of administration should match the severity of the deficiency and the patient's clinical status 2.