Hypotension & its causes

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Specializes in Critical Care, Emergency Medicine, Flight.

Alright, so recently we had a lecture in class about BPH & Urinary retention. My instructor told us gave us an example of a pt retaining about 1200ml of urine. He would need to be catheterized. Now, she told us that we would have to remove say 600ml of fluid, wait a little bit.. (didnt really say how long) and then cath and remove the remaining 600ml. She said the reason for this was if you remove all 1200ml of fluid, the person would go into shock.

does this make any sense?

My thought is , your urine is no longer part of circulating fluid and is just hanging out in your bladder until you eliminate it. i dont see how it would cause you to become hypotensive..in the sense of decreased circulating blood /fluid volume.

can anyone enlighten me?:idea: I would ask my instructor but someone did in class and she gave that "ya, you just shouldnt do it" answer , no really beef to back it up with.

Thanks! :)

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Specializes in NICU, PICU, PCVICU and peds oncology.

If you remove that large a volume of urine from a person's bladder at one time, it causes a shift in their intra-abdominal pressure, leading to dilatation of the blood vessels in that compartment which then causes a drop in venous return to the heart. If you drop preload in this way, you will also drop cardiac output and shock is the result.

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Specializes in Emergency.
If you remove that large a volume of urine from a person's bladder at one time....

You know, I argued the same point as pneumothorax to an ICU nurse the other week. She just said you can lower BP without any explanation behind it. Therefore, I didn't want to believe her. You however, put it quite succinctly! :up:

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well, except that it's nonsense, :uhoh3:. that's an old wives' tale that's been around forever, with various amounts-- a liter, then clamp for ten minutes/half an hour/an hour; 500cc, then clamp, ad infinitum.

think about it-- some people have big bladders and void that much. do they go into shock? no. (ad = autonomic dysreflexia, a complication of spinal cord injury above t6)

http://sci.rutgers.edu/forum/showthread.php?t=125929

"this is an old myth that is dying a very difficult death. there is no scientific basis or evidence base for there being any ill effects of draining the complete bladder volume when catheterizing the urinary bladder. there are many rumored ill effects (hypotension, shock, etc.)...yours of bladder prolapse is a new one on me, but also without any scientific basis. you would have to rip a bunch of ligaments to prolapse your bladder in a woman, and it is nearly impossible in men. i was actually involved in a ebp study related to this in the 1980s and we not only found no evidence of any serious effects that was research based, but also did an additional study of health care providers' fixed beliefs related to this and the very weird and physiologically and anatomically impossible ill sequalae that they claimed could result.

the only exception is when we cath patients with sci who are having an active ad episode, as we do know that under those circumstances that rapid decompression of a very full bladder (say over 1000 cc.) can cause bladder spasm, which can worsen ad. our protocol calls for draining 500 cc. at a time, clamping for 5 minutes, then draining another 500 cc., then clamping for 5 min. etc. etc. until the bladder is completely empty."

in a series of patients with obstruction, christensen et al found a 50% decrease in intravesical pressure after only the first 100 ml of urine was removed.[2, christensen j, ostri p, frimodt-moller c, juul c. intravesical pressure changes during bladder drainage in patients with acute urinary retention. urol int. 1987;42(3):181-4. [medline]. ] since the major drop in bladder pressure occurred with the early removal of relatively small amounts of urine, they concluded that fractionating urine removal in bladder obstruction was unjustified.

hematuria and bladder spasm is another well-known complication of bladder decompression. gould et al compared the incidence of hematuria in rapidly emptied and gradually emptied obstructed dog bladders.[3gould f, cheng cy, lapides j. comparison of rapid versus slow decompression of the distended urinary bladder. investigative urology. sep 1976;14 (2):156-8. [medline]. ] they found that hematuria was correlated strongly with the degree of bladder wall damage prior to relief of obstruction and was not correlated with the rate of emptying.

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Specializes in Critical Care, Emergency Medicine, Flight.
well, except that it's nonsense, :uhoh3:. that's an old wives' tale that's been around forever, with various amounts-- a liter, then clamp for ten minutes/half an hour/an hour; 500cc, then clamp, ad infinitum.

think about it-- some people have big bladders and void that much. do they go into shock? no. (ad = autonomic dysreflexia, a complication of spinal cord injury above t6)

http://sci.rutgers.edu/forum/showthread.php?t=125929

"this is an old myth that is dying a very difficult death. there is no scientific basis or evidence base for there being any ill effects of draining the complete bladder volume when catheterizing the urinary bladder. there are many rumored ill effects (hypotension, shock, etc.)...yours of bladder prolapse is a new one on me, but also without any scientific basis. you would have to rip a bunch of ligaments to prolapse your bladder in a woman, and it is nearly impossible in men. i was actually involved in a ebp study related to this in the 1980s and we not only found no evidence of any serious effects that was research based, but also did an additional study of health care providers' fixed beliefs related to this and the very weird and physiologically and anatomically impossible ill sequalae that they claimed could result.

the only exception is when we cath patients with sci who are having an active ad episode, as we do know that under those circumstances that rapid decompression of a very full bladder (say over 1000 cc.) can cause bladder spasm, which can worsen ad. our protocol calls for draining 500 cc. at a time, clamping for 5 minutes, then draining another 500 cc., then clamping for 5 min. etc. etc. until the bladder is completely empty."

in a series of patients with obstruction, christensen et al found a 50% decrease in intravesical pressure after only the first 100 ml of urine was removed.[2, christensen j, ostri p, frimodt-moller c, juul c. intravesical pressure changes during bladder drainage in patients with acute urinary retention. urol int. 1987;42(3):181-4. [medline]. ] since the major drop in bladder pressure occurred with the early removal of relatively small amounts of urine, they concluded that fractionating urine removal in bladder obstruction was unjustified.

hematuria and bladder spasm is another well-known complication of bladder decompression. gould et al compared the incidence of hematuria in rapidly emptied and gradually emptied obstructed dog bladders.[3gould f, cheng cy, lapides j. comparison of rapid versus slow decompression of the distended urinary bladder. investigative urology. sep 1976;14 (2):156-8. [medline]. ] they found that hematuria was correlated strongly with the degree of bladder wall damage prior to relief of obstruction and was not correlated with the rate of emptying.

i dont have time to read this all right now, but i skimmed over it and you have piqued my interest.

im gonna look into this further after my meeting tonight :)

thank you so much!:nurse:

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