Instructor says textbooks are wrong about urine output

  1. Hello,

    Our instructor was telling us that the common limit in hospitals and textbooks for urine output before intervention is at 30 ml/hr. She said that she strongly disagrees with this figure, because at that level the kidney is outputing half of the amount of urine it should be. She says that often by waiting that long, most of the patient's nephrons are destroyed resulting in serious kidney damage or even failure. Do you guys find this to be true? Our instructor is very intelligent and experienced, but she is giving a tall order by saying that all the hospitals and books are wrong about the right output level to intervene at.

    Alpha
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  2. 20 Comments

  3. by   ElvishDNP
    I am by far not an expert on kidneys, but here's what I've found. Our postop patients often put out *right at* 30ml/hr for several hours immediately following surgery. If they go less than that, we call the MD about it. What generally happens is that their UO is low for a few hours but then they diurese and pee to beat the band; we usually have to empty their foleys more often than qshift. A lot of the fluids used in surgery (LR, D5LR) have a delayed diuresis effect too. If a person is healthy, she/he can probably withstand a UO of 30ml/hr for a short time without going into renal failure. Once I took care of a patient who'd been bleeding so profusely from her vagina/uterus that her vessels had to be embolized and the MD gave her something (I don't remember off the top of my head what it was, it's been a few months) for her BP bottoming out, which was a vasoconstrictor. He told me not to call unless her UO was less than 20ml/hr because this med, being a vasoconstrictor, temporarily decreased blood flow to her kidneys. She tolerated it just fine and within a few hours was outputting normally again.

    I'm sure, however, that there is someone way more qualified than me to answer the question! Hope this helps a little.
  4. by   classicdame
    I agree with your instructor's philosophy, but when you are tested, you need to remember the 30 ml range. There has to be a cut off for testing purposes. However, in reality you will be watching that patient carefully if the output is significantly different (high or low) from input.
  5. by   TiffyRN
    Your instructor can disagree with hospital standards and textbooks, there are plenty of things I disagree with that are routine "reportables" in hospitals. However, generally the 30ml/hr is the accepted minimum output for adults. That is the number you need to keep in mind for testing purposes and as a "reportable" in your adult patients.
  6. by   RedCell
    Urinary output should be a minimum of 0.5ml/kg/hr, in newborns 1ml/kg/hr or greater. Anything less is considered oliguria. Multiple studies however, have shown no correlation between urine volume and evidence of acute tubular necrosis, GFR, or creatinine clearance.

    Miller, R. D. (2005). Miller's Anesthesia (6th ed.). Philadelphia: Elsevier.

    Tell your instructor she cannot dispute this dude, he is the master. The routine 30ml/hr is based on a guy that weighs 60kg. Americans are much fatter than that these days.
  7. by   cardiacRN2006
    Yep. Our instructors said, "I never want to hear 30ml/hr again"...


    It's anything greater than or equal to 0.5ml/kg/hr, preferably 1ml/kg/hr.
    30ml/hr is old school, and by today's standards, inaccurate. (unless like the pp stated, you are 60kgs...)
  8. by   meownsmile
    I think that may be what your instructor is meaning. She doesnt want to deal with how many ml's per hour one patient puts out but she prefers to see urine output being calculated based on ml/kg of body weight per hour. Which is fine, but normally you wont have time to sit and figure everyone's ml/kg/hr rate individually.
    I think 30ml is a good average to remember as a whole. But you have to do as the instructor wants while in school. So learn to calculate it her way.
  9. by   HM2VikingRN
    I remember seeing both the 0.5 ml/kg/hr and the 30ml/hour in my Med Surge textbook. (McLean Heitkemper 2007 7th ed).
  10. by   GregRN
    Quote from Alpha13
    Hello,

    Our instructor was telling us that the common limit in hospitals and textbooks for urine output before intervention is at 30 ml/hr. She said that she strongly disagrees with this figure, because at that level the kidney is outputing half of the amount of urine it should be. She says that often by waiting that long, most of the patient's nephrons are destroyed resulting in serious kidney damage or even failure. Do you guys find this to be true? Our instructor is very intelligent and experienced, but she is giving a tall order by saying that all the hospitals and books are wrong about the right output level to intervene at.

    Alpha
    Tall order indeed. It's like trying to steer the Titanic wtih a paddle: yes, it can be done, but it's going to take a long, long time. Most hospitals use 30ml and, depending on the surgery/situation, it may be adequate. Many surgery patients are kept very dry intentionally and 30ml is a fine benchmark. However, for patients who are well hydrated and intake isn't being restricted, 0.5mg/kg/hr is more accurate.

    The only thing I would question is the instructor's assertion that when a patient reaches 30ml/hr., "most of the patient's nephrons are destroyed resulting in serious kidney damage or even failure." You can lose almost 90% of your nephrons and still have functioning kidneys. At 1,000,000 nephrons per kidney, there's a lot of room. ESRD usually occurs at more than 90% nephron loss.
    Last edit by GregRN on Apr 7, '07
  11. by   TrudyRN
    Quote from RedCell
    Urinary output should be a minimum of 0.5ml/kg/hr, in newborns 1ml/kg/hr or greater. Anything less is considered oliguria. Multiple studies however, have shown no correlation between urine volume and evidence of acute tubular necrosis, GFR, or creatinine clearance.

    Miller, R. D. (2005). Miller's Anesthesia (6th ed.). Philadelphia: Elsevier.

    Tell your instructor she cannot dispute this dude, he is the master. The routine 30ml/hr is based on a guy that weighs 60kg. Americans are much fatter than that these days.
    Not all Americans are much fatter than that these days. That's a dangerous generalization, RedCell. As dangerous as saying Miller is the "master", meaning he's the only one who knows anything about the topic. Open minds, keep open minds.
  12. by   GregRN
    Quote from TrudyRN
    Not all Americans are much fatter than that these days. That's a dangerous generalization, RedCell. As dangerous as saying Miller is the "master", meaning he's the only one who knows anything about the topic. Open minds, keep open minds.
    Dangerous? Really? Americans as a whole ARE much fatter these days. That isn't debatable. Does that mean ALL Americans are fatter these days than ALL Americans previous? Not by any means, and that's not what RedCell was saying anyway. Semantics aside, the obesity epidemic (and it is an epidemic) in America is much more dengerous than political correctness.
  13. by   carolinapooh
    Quote from TrudyRN
    Not all Americans are much fatter than that these days. That's a dangerous generalization, RedCell. As dangerous as saying Miller is the "master", meaning he's the only one who knows anything about the topic. Open minds, keep open minds.
    I think what she means is that your average adult male these days weighs more than 132 pounds. I'd guess most men - and I consider my husband pretty average at age 37 and about six feet tall - probably weigh closer to 180ish - and many men I know and have cared for weigh more than that; that doesn't mean they're necessarily obese, either, although unfortunately a lot of them ARE.

    I don't consider saying most of us weigh more than 132 lbs a "dangerous generalization". Most people I know weigh more than that and are perfectly "normal" for their height and weight.
  14. by   Roy Fokker
    I don't nearly "freak out" about low u/o q shift now as much as I used to when I started working.

    Now I also factor in other things - like age, weight, fluid maintenance rates, cardiac and nephro history etc. And no, I don't go by the "less than 30 cc/hr" standard --- unless MD orders states so.

    I am cross with some surgeons about their IV fluid orders - maintenance rates are almost always insufficient and patients keep having chronic low output (with attending complains of feeling "thirsty" and "dry").

    Some of our docs are very good about it. Some are notorious for being absolutely indifferent.

    I also found, curiously, that many of my peers did not know about Holliday-Segar maintenance fluid rates formulas (which I understand is one of the simplest ways to determine fluid maintenance).

    cheers,
    Last edit by Roy Fokker on Apr 7, '07

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