Poor Urinary Output Flashcards
How much urine do normal adults produce per hour?
1 ml/kg/hour
What urine output would be considered as oliguria?
< 0.5 ml/kg/hour
What important condition can decreased urine output be the first sign of?
Impending acute renal failure
What are the major complications of AKI that could be fatal?
Hyperkalaemia
Acidosis
Uraemia
Pulmonary oedema
What are the three main requirements for normal renal function?
Adequate blood supply to the kidney
Functioning kidneys
Unobstructed flow of urine from the kidneys, down the ureters to the bladder and out via the urethra
List the main pre-renal causes of poor urinary output.
Hypovolaemia (e.g. haemorrhage, dehydration)
Hypotension (e.g. sepsis, pancreatitis)
Heart failure
Reduced local perfusion of the kidneys (e.g. renal emboli, renal artery dissection)
List the main renal causes of poor urinary output.
- Tubular – acute tubular necrosis
- Glomerular – glomerulonephritis
- Interstitial – acute interstitial nephritis
- Vascular
Vasculitides
Haemolytic uraemic syndrome
Thrombocytic thrombocytopenic purpura
DIC
Malignant hypertension
Scleroderma - Infectious
Malaria
Legionnaire’s disease
Leptospirosis - Complex – multiple myeloma
List the main post-renal causes of poor urinary output.
- Ureters Bilateral calculi Abdominal/pelvic mass compressing the ureters Retroperitoneal fibrosis - Bladder Neuropathic bladder Anticholinergic and sympathomimetic drugs Bladder stones or tumour Ureterovaginal prolapse - Urethra BPH Blocked catheter Prostate cancer Urethral stricture Trauma Infection
What must you look for on fluid balance charts?
Adequate fluid intake – average-sized adults should have 3 L of water per day (30-50 ml/kg/day)
Positive balance – make sure there is at least as much fluid going in as there is going out
Describe how the fluid requirement of febrile patients is different from afebrile patients.
Febrile patients require an extra 500 ml per 1 degree above 37
What must you look for on the surgical operative notes?
Pelvic surgery may damage the urinary tract
Laparotomies cause a lot of fluid loss leading to dehydration
Blood loss (usually poorly estimated)
List some nephrotoxic drugs that you would look for on the drug charts of a patient with AKI.
NSAIDs ACE inhibitors Diuretics Some antibiotics (e.g. gentamycin, vancomycin) IV contrast
Why does acute haemorrhage cause a delayed drop in Hb?
Acute haemorrhage will initially lead to an equal loss of serum and Hb meaning that the Hb concentration has not changed
However, serum will be replenished much quicker than Hb leading to a delayed drop in Hb
Why is it important to compare pre-operative and post-operative blood test results?
Allows you to check for pre-existing anaemia and long-standing renal impairment
It allows you to check whether any abnormal changes are new or whether they have always been there (provides baseline values)
What is an important comorbidity that increases the risk of the patient developing AKI?
Cardiac disease – can lead to inadequate renal perfusion