From the Research
The optimal fluid for post-obstructive diuresis is lactated Ringer solution, as it has been shown to reduce major adverse kidney events compared to normal saline 1. When managing post-obstructive diuresis, the goal is to replace ongoing urinary losses with appropriate intravenous fluids to prevent volume depletion and electrolyte abnormalities.
- Patients should receive volume replacement at a rate of approximately 75-100% of urine output, adjusted based on clinical status and laboratory values.
- Potassium chloride should be added to the fluids at concentrations of 20-40 mEq/L depending on serum potassium levels, as hypokalemia is common during this phase.
- Close monitoring of vital signs, fluid balance, and electrolytes (sodium, potassium, bicarbonate) every 4-6 hours is essential, with adjustments made accordingly. The physiological basis for using lactated Ringer solution is that post-obstructive diuresis typically results in isotonic or hypotonic urine losses with significant sodium and potassium wasting, and lactated Ringer solution has been shown to be associated with a reduction in major adverse kidney events 1.
- The diuresis occurs due to impaired renal concentrating ability, accumulated osmotic solutes, and natriuretic factors that developed during the obstruction.
- Fluid replacement should continue until the diuresis resolves, typically within 24-48 hours, when urine output stabilizes to less than 200 mL/hour or 2-3 L/day. It is worth noting that while older studies suggested the use of isotonic saline 2, 3, 4, 5, the most recent and highest quality study recommends the use of lactated Ringer solution 1.