The treatment of functional oliguria depends on the severity of the hypovolemia. In mild cases, oral fluid administration is usually sufficient.
In severe cases, i.v. fluid substitution with isotonic saline (0.9% NaCl) is indicated.
Patients with hypernatremia should instead receive a hypotonic solution such as 5% dextrose if water loss alone has occurred, or hypotonic saline (½ to ¼ normal saline) if water plus NaCl loss has occurred.
In metabolic acidosis with loss of bicarbonate, i. v. substitution of bicarbonate is indicated (Kasper 2015).
Blood loss: Patients with severe hemorrhage, should receive red cell concentrates, with hematocrit not exceeding 35% (Kasper 2015).
Urineoutput: Urine output is recommended to be monitored hourly in severe cases (Haider 2021).
Diuretics: If the oliguria does not resolve with the above fluid administration, the furosemide stress test (FST) is indicated for accurate assessment of renal function and further prognosis. The FST is one of the newer dynamic function markers (Kindgen- Milles 2020).
For this, the patient must first be euvolaemic. The test itself should be performed under constant monitoring of heart rate and blood pressure.
The patient receives a short infusion of 1 - 1.5 mg / kg bw furosemide.
If a diuresis of > 100 ml / h subsequently occurs, this indicates a GFR of > 20 ml / min and makes a progression of acute renal failure unlikely (Kindgen- Milles 2020). In this case, therapy with diuretics should be continued (Haider 2021).
If the above. Diuresis does not start within the first 2 h p. i., it is recommended to administer 100 - 200 mg furosemide. If this is also unsuccessful, a thiazide diuretic can still be tried. If all attempts are unsuccessful, diuretics should be discontinued (Haider 2021).
In patients with secondary renal oliguria, treatment focuses on supportive measures and - if necessary - renal replacement therapy (Haider 2021).