The Furosemide Stress Test
You admitted a 72 year old male to the ICU for septic shock from community acquired pneumonia. He required intubation and mechanical ventilation for failure to improve oxygenation with NIPPV and encephalopathy. He received broad spectrum antibiotics and a 30 cc/kg crystalloid bolus. His MAP was persistently in the 50s despite adequate fluid resuscitation and based on your exam he does not appear hypovolemic. Norepinephrine is started and despite adequate MAP he is oliguric. His only medical history is he was a previous smoker with COPD, HTN, HLD but normal renal function with a Cr of 0.8 two months prior. His Cr on admission is 2.2 and a foley is placed and his UA shows granular casts. He is not acidotic and his electrolytes are normal.
You are concerned this patient may require renal replacement therapy. He is adequately fluid resuscitated and has a MAP above 65 on a vasopressor but is still not making urine and has signs of ATN on urinalysis. Renal replacement therapy is an invasive procedure and has associated risks. If a patient has a chance to have renal recovery with a more conservative approach then this should be considered. You wonder if there is a diagnostic test which can be used to assess the potential for renal recovery.
The furosemide stress test can be used to determine if underlying renal function may recover.
The test involves administering a bolus of 1 mg/kg of furosemide to a patient that is furosemide naive or 1.5 mg/kg of furosemide to a non-naive patient. The urine output is then monitored over the next two hours. If >200 ml of urine is produced this indicates that tubular function is intact and the patient may recover. If less than 200 ml or urine is produced the patient may develop worsening AKI and require renal replacement therapy.
Important points before attempting a furosemide challenge is to ensure the patient is adequately fluid resuscitated with appropriate MAP. Furosemide can cause hypovolemia and if the MAP is < 65 the kidneys may not be adequately perfused. Make sure the patient is resuscitated prior attempting the furosemide stress test.
Chawla L, Davison D, Brasha-Mitchell E, et al. Development and standardization of a furosemide stress test to predict the severity of acute kidney injury. Crit Care. 2013;17(5):R207.
Koyner, J., Davison, D., Brasha-Mitchell, E., Chalikonda, D., Arthur, J., Shaw, A., Tumlin, J., Trevino, S., Bennett, M., Kimmel, P., Seneff, M., Chawla, L. (2015). Furosemide Stress Test and Biomarkers for the Prediction of AKI SeverityJournal of the American Society of Nephrology 26(8), 2023-2031. https://dx.doi.org/10.1681/asn.2014060535