Poor urinary output Flashcards
What is oliguria and uria. What is normal urine output
Normal= 1mL/kg/hour
Oliguria is reduced urinary output, defined variously as:
<0.5mL/kg/hour,
<400mL/day and
<30mL/hour.
Anuria=complete absence of urine output
Untreated poor urinary output may indicate what.
How can patients die from this
Decreased urine output should be taken very seriously as it may be the fi rst (and
only) sign of impending acute renal failure.
Untreated, patients may die from hyperkalaemia, profound acidosis, or pulmonary oedema due to the kidneys not performing
their usual physiological role.
T/f renal stone in a ureter might be the cause of a reduced urine output
BILATERAL calcu`li necessary
Which drugs might result in poor urinary output and why
NSAIDs/Abx (gentamycin, vancomycin) can cause interstitial nephritis
Anticholinergi/sympathomimetics can be a bladder related cause
Broadly, how much fluid will an adult of average size need in 24hrs?
What if they are febrile
An adult of average size will require about 3L of fl uid intake per 24 hours (30–50 mL/kg/day)
Febrile, you need an extra 500mL for every 1 degrees above 37 degrees to compensate for sweating/increased RR
How can surgery (both any surgery, but also specifically pelvic surgery) cause poor urinary output
Pelvic surgery may result in damage to the urinary tract.
Surgery to the urinary tract itself can cause damage (e.g. urethral strictures after
a cystoscopic procedure).
Laparotomies (especially those of long duration)
can result in dehydration by evaporation of water from the open peritoneal
cavity and this loss of volume will not be recorded in the fl uid balance charts.
+
Blood loss
+
Anaethesia
What are the markers of intravascular hydration status?
When might intravascular hydration status not be matched to extravascular hydration status?
It is important
to be aware of the signs of intravascular hydration status versus extravascular
hydration status – the former is the critical parameter in this instance, and the
relevant markers are pulse, blood pressure, capillary refi ll time, and jugular
venous pressure (JVP).
Remember that it is perfectly possible for a patient
to be overloaded with fl uid in the extravascular compartment, but to be fl uid
depleted intravascularly, e.g. septic shock.
Why must you do a DRE in anybody not catheterised with poor urinary output
Check for a colon loaded with faeces and for an enlarged
prostate.
What might be the cause of bilateral basal lung crackles without any other signs of HF?
Post-operative atelectasis: small areas of alveolar
collapse that are common after surgery
What is suggested if the urea is raised alone, vs if the urea is raised along with creatinine
If the urea is raised, it suggests hypovolaemia. If the creatinine is also raised, it suggests renal injury (e.g. acute tubular necrosis).
How can urine versus serum concentratiosn of sodium help you distinguish pre-renal vs renal cause of poor urinary output
If pre-renal:
-Kidneys will try to reabsorb as much sodium to combat the hypovolaemia. So urine will be concentrated, and there will be low Na+
-If a renal problem, the kidneys will fail to concentrate the urine, or to reabsorb Na+ and water. So the urine will be dilute but have a high Na+
What is the convention for maintenance fluids
You then need
to remember to keep him on maintenance fl uids. Convention is to give 3 L over
24 hours, comprising 1 L of normal saline (+20 mM K+
) and 2 × 1 L of 5% dextrose
(+20 mM K+
). Th is should provide 3 L of water and the correct amount of electrolytes, but you will obviously have to adjust this for individual patients based on the
urea and electrolyte (U&E) results.
