Having trouble with understanding lasix use

Nurses General Nursing

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I understand what lasix does in terms of removing fluid from pts' so to help with CHF/fluid around their lungs to hlp them breathe better, and what it can cause (metabolic alkalosis, hypokalemia, hyponatremia, etc.) but I am having a hard time grasping the fact that it is given at times due to oliguria caused by renal failure. I was in practicum the other day and I saw a nurse giving lasix to a pt who had oliguria and a creatinine that was high, I think it was 2.3 or something. Why is this? I thought that it should not be given when creatinine is high. Thanks for any help guys!

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It is given when a oliguric patient's creatinine is high to stimulate the kidneys to make urine. This can at times stimulate some form of urine formation in the oliguric patient that is fluid overloaded.

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Specializes in Dialysis, Nephrology & Cosmetic Surgery.

Look up the NKF K/DOQI guidelines for more info as I am not an expert in the ins & outs of why. As a Renal nurse I see it used routinely as it will help regulate not only fluid loss but will help with the excretion of sodium, therefore helping regulating blood pressure.

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I had trouble understanding this too when I first went through IV therapy, so let me see if I can explain it.

In the case of renal failure or disease, the creatinine is high because the glomeruli aren't filtering it out as they should, and urine output is low (oliguria). Lasix is administered because it will increase urine output despite low functioning kidneys, which should also help lower creatinine levels. Creatinine is not harmful - it is largely just used as an indicator of kidney function.

If the oliguria was caused by an obstruction in the ureters or urethra, then you wouldn't treat with lasix. But since lasix works as a loop diuretic, it will help in oliguria and renal failure to increase urinary output and lower levels of minerals.

At least, this is how I understood it. I'm only an LPN though, not an RN =]

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Specializes in Critical Care.

Something to keep in mind in addition to what others have said: you need to know you're pt's baseline renal function when determing whether to give Lasix or not. Many CHF patients have some form of chronic renal insufficiency so if their baseline is already high, you may not only be giving Lasix but giving a higher dose in order to get a response. I liken it to "spanking" the kidneys to get them to give up some fluid. (It may sound like a silly description but the visual helped me understand it.) You also may be giving differing diuretics as well.

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Specializes in Hospital Education Coordinator.

sorta like what Metformin and other pills do to the pancreas - gives it a poke to make it function to highest capacity. BTW, DOCUMENT the results. No point in poking if no results. MD then has to go to plan B, whatever that is.

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thanks for all the replys so far...I was just confused b/c I have heard before that if the BUN and creatinine are elevated then it is time to stop giving lasix. Is that true or is that not the case in this straight-forward scenario? I'm just curious b/c there was another day last week in this same practicum when I was given the orders to hold the lasix dose b/c the creatinine levels were rising from 2.1-2.4 (BUN rising from 22 to 23). My initial though was ohh, I guess if they are having some sort of renal issue, be it ATN/acute renal failure that you wouldn't want to give lasix b/c they may have been thinking that he was too negative in his fluid status and his kidney's were suffering from maybe a low CO, but his pressures were fine and he was overall net 500mL positive for his stay.

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Specializes in SICU.

Lasix can be used to differentiate pre-renal failure from renal failure. The medical side will give lasix to see if the pt makes any more urine. The surgical side will give a fluid bolus (500 ml) and see if any more urine is made. Either way if urine output increases then it's pre-renal, if not then it's renal.

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I always though you should not give Lasik if the patient has oliguria.

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I always though you should not give Lasik if the patient has oliguria.

happens all the time in the sicu I am doing my practicum at

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Specializes in tele, stepdown/PCU, med/surg.

This was always something that I also never truly understood in my years of practice. I truly believe it is such something that MDs use because they think it can work. I don't think it's best practice or anything. Obviously is Lasix helps produce more urine and if the creatinine goes down or doesn't get worse, than why not. More urine is usually good for the oliguric patient. However, if Lasix is given and urine output doesn't increase and/or the creatinine goes up, it is obviously contraindicated and damaging to the patient.

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I've been taught that the pt is not in renal failure unless the BUN is >40 and the creat is >4. Anything less is renal insufficiency, meaning that the kidneys are still functioning at some level. They give lasix to stimulate the kidney to work a little more.

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