We’ve all heard it at some point on morning rounds: “Mr. So-and-so had a creatinine bump from 1.6 to 2.4 overnight, so we’re holding his home Lasix tonight.” Everyone nods knowingly. Obviously, if someone has AKI, they can’t get Lasix, right?
As with most things in medicine: it depends.
Remember that AKI is defined in a variety of ways. There are specific criteria from KDIGO:
- Increase in Cr by ≥0.3 mg/dl within 48 hours; or
- Increase in Cr to ≥1.5 times baseline in the past 7 days; or
- Urine volume < 0.5 ml/kg/h for 6 hours.
There are also TONS of reasons a patient might have AKI. It can be overwhelming, so keep the three major categories of AKI in mind:
- pre-renal: usually low-volume state, hypotension, ischemic injury
- intrinsic: ATN, drugs that can directly injure the cells, IV contrast
- post-renal: obstructive causes like kidney stones, neurogenic bladder, etc.
The argument for holding Lasix is that it is a diuretic that acts on the tubules of the nephron and results in water loss, which can aggravate AKI. If you are astute, you will realize that this argument only applies to pre-renal AKI! Reducing volume to the kidneys won’t affect an intrinsic injury, and it may or may not be appropriate for post-renal causes of AKI. Therefore, you can’t use the blanket statement that if a patient has AKI, they can’t get furosemide.
Whether or not a patient should get furosemide depends on their volume status. Certainly, if a patient is dehydrated, giving them Lasix and forcing them to pee more water out would not help their kidneys. But if a patient has intrinsic or post-renal AKI, then Lasix can be continued or held based on the patient’s volume status.
To sum up, if Mr. So-and-so has a blood pressure of 100/60 and has a creatinine bump, holding furosemide is good clinical management. But if Mr. So-and-so has a blood pressure of 140/80 and had an MRI with contrast yesterday, then holding furosemide won’t make him better (and it will probably make his hypertension worse). If Mr. So-and-so had a creatinine bump and also has new bilateral crackles on exam this morning, you might order a chest x-ray to evaluate for fluid overload and keep him on the furosemide.