Oliguria

Oliguria is defined as urine output less than 0.5 mL/kg/h. Prerenal, renal, and postrenal causes are described in Chapter 4.

1. Treatment includes ruling out mechanical causes (e.g., malpositioned, kinked, or obstructed Foley catheter) and renal dysfunction (can be accessed through renal ultrasound).
2. Hypotension should be corrected to ensure adequate renal perfusion pressure.
3. Volume status should be assessed. A fluid bolus may be given if hypovolemia is suspected. If oliguria persists, CVP measurement or systolic variation in arterial tracing in mechanically ventilated patients may help guide further fluid management. Patients with reduced ventricular function may require placement of a pulmonary artery catheter.
4. If oliguria persists despite an adequate volume status, urine output can be increased with the following drugs. Current evidence suggests that these medications do not affect renal function or outcome, however they may aid in toxin elimination and reduce the formation of casts.
   1. Furosemide, 2 to 20 mg IV.
   2. Dopamine infusion, 1 to 3 μg/kg/min IV.
   3. Mannitol, 12.5 to 25.0 g IV.
   4. Fenoldopam, 0.1 to 0.4 μg/kg/min IV.
5. Intraoperative diuretics may be required to preserve urine output in patients on chronic diuretic therapy.