Fluid Management in Critical Care

Intensive Care patients are prone to Fluid Overload
1. Initial emergency Resuscitation often has replaced most of patient's presenting fluid deficits
2. Fluid Overload (Positive Fluid Balance) is associated with worse outcomes and higher mortality
Minimize maintenance fluids beyond specific indications (e.g. Pancreatitis, Sepsis, Diabetic Ketoacidosis, Rhabdomyolysis)
1. Estimate daily fluid requirements and subtract intravenous infusions and Enteral Nutrition volumes
2. Although otherwise healthy patients maintain fluid balance, most ICU patients have disordered fluid balance

Fluid management decisions should be based on reliable clinical data
1. Avoid Positive Fluid Balance >4-5 liters above dry weight
2. Carefully follow input and output volumes
3. See Inferior Vena Cava Ultrasound for Volume Status
4. Avoid Central Venous Pressure (CVP) as a marker of fluid status
5. Avoid Lactic Acid as a marker of fluid status
  1. Evaluate for other causes of Lactic Acidosis, before reflexively administering more IV fluids
Intravenous Fluids
1. Lactated Ringers (LR) is preferred in most cases (including Hyperkalemia)
  1. Normal Saline is associated with Metabolic Acidosis
  2. LR does have more Drug Interactions (e.g. Ceftriaxone, zosyn cannot be run on the same IV line)
Diuresis (for excessive Positive Fluid Balance >5 L)
1. Furosemide (Lasix)
  1. Combine with other Diuretics to prevent Hypernatremia (from dilute urine excretion)
2. Thiazide Diuretics
  1. Use in combination with Loop Diuretic to increase Sodium excretion (and prevent Hypernatremia)
  2. Indapamide 2.5 to 5 mg orally daily OR
  3. Chlorothiazide 500 mg IV every 12 hours
3. Acetazolamide
  1. Indicated in persistent Fluid Overload, yet significant contraction alkalosis from aggressive diuresis
  2. Acetazolamide 500 to 1000 mg IV every 12 hours
4. Electrolytes
  1. Monitor Serum Potassium and Magnesium closely during aggressive diuresis

Sodium
1. Hypernatremia
  1. See Hypernatremia (as well as management below)
2. Hyponatremia
  1. See Hyponatremia
  2. MIld Hyponatremia 125-135 mE/L is common in the ICU setting
    1. Does not typically require correction or further evaluation when in this range
Potassium
1. Hyperkalemia
  1. See Hyperkalemia
  2. See Hyperkalemia Management
2. Hypokalemia
  1. See Hypokalemia
  2. See Potassium Replacement
  3. Enteral Potassium Replacement is preferred over intravenous Potassium
  4. Correct Hypomagnesemia with intravenous Magnesium
  5. Do NOT over-correct Hypokalemia in Renal Failure (target Potassium of 3.5 meq/L)
Calcium
1. See Hypocalcemia
2. Hypocalcemia is common in the ICU and does not typically require replacement
  1. Calcium Replacement indicated for very low levels (Ionized Calcium <2 mg/dl or <0.5 mmol/L)
Magnesium
1. See Hypomagnesemia
2. Correct Hypomagnesemia with intravenous Magnesium

See Hypernatremia
Hypernatremia with Polyuria in hospitalized patients is common and critical to prevent and correct
1. Results from Parenteral or enteral feeds AND
2. Inadequate free water intake OR Increased free water loss (e.g. Central Diabetes Insipidus in Head Injury)
Correct Hypernatremia
1. Administer free water
  1. Enteral water sources are preferred (e.g. Feeding Tube)
  2. D5W is an alternative (avoid 1/2NS due to risk of volume overload)
2. Calculate free water requirements
  1. See Free Water Deficit
  2. See Hypernatremia
3. Chronic Hypernatremia (>48 hours) should be replaced slowly (esp. in under age 30-40 years)
  1. Limit Serum Sodium reduction to 12 mEq/L per day
4. Concurrent Volume overload
  1. Coadminister free water (as above) with Diuretics
  2. Diuretics: Furosemide AND high dose Thiazide Diuretics (see above)
  3. Monitor Electrolytes with diuresis (Serum Potassium and Serum Magnesium)
Prevention
1. Intervene when Serum Sodium is trending upwards, by increasing free water