Does my patient need maintenance fluids?
SCENARIO 2: IMPAIRED WATER EXCRETION, AND FLUIDS GIVEN
If the patient is euvolemic but has or is at risk for ADH stimulation,1,9 providing maintenance IV fluids according to the NICE or Holliday-Segar recommendations (a total of 2 L of 0.2% NaCl = 34 mEq Na/L = 68 mOsm/L) would result in an excess of free water, as an increase in ADH secretion impairs free water clearance. A potential scenario with impaired water excretion is shown in Table 2.
After 24 hours, the patient’s serum osmolality would drop by about 7 mOsm/L, and the serum sodium would decrease by 3 or 4 mEq. The consequence of the intracellular fluid shift would be seen by the expansion of the intracellular volume from 28 to 28.7 L.
If this patient were to have received 2 L of 0.9% NaCl (308 mOsm/L × 2 L = 616 Osm) as suggested by Moritz and Ayus,1 the result would be a serum osmolality of 284 mOsm/L, thus avoiding hyponatremia and intracellular fluid shifts.
THE BOTTOM LINE
Know your patient, answer the clinical questions noted above, and decide.
For a euvolemic patient with normal serum sodium, GFR greater than 60 mL/1.73 m2, and no ADH stimulation, for 24 hours it probably doesn’t matter that much, but a daily reassessment of the continued need for and type of intravenous fluids is critical.
For patients not meeting the criteria noted above such as a patient with systolic or diastolic heart failure, advanced or end-stage renal disease puts the patient at risk for early potential complications of either hyponatremia or sodium overload. For these patients, maintenance intravenous fluids need to be chosen wisely. Daily weights, examinations, and laboratory testing will let you know if something is not right and will allow for early detection and treatment.
