Renal Dysfunction Flashcards
Why is urine normally clear/ amber coloured?
Urobilinogen - breakdown product of haemoglobin
What does SG stand for?
Specific gravity? 1003-1030
pH of urine?
Output?
5-6.5 (due to hydrogen)
0.5ml per kg per hour
What is the composition of urine?
96% water
2% urea
others: creatinine, ammonia, sodium, chlorides, sulphates, potassium
Dip stick?
Lab tests?
Variety of info about urine e.g. SG, nitrates, bilurubin, urobilinogen, proteins etc.
Urine specific gravity test - lab
1.003-1030 is normal range
Above 1030 = dehydration, higher = more dehydration
Why? Sweating,
SG- pneumonia - fast resp rates
What causes high Specific gravity?
Increased concentration of solutes... Anything that makes you dehydrated: - sweating - temperature - fast respiratory rates - UTI - more urination, dehydration - decreased renal blood flow (poor perfusion to kidney) - Excessive ADH secretion (anti-diuretic hormone)
What does HIGH specific gravity indicate?
You have extra substances in your urine e.g. - - - -
What does LOW specific gravity indicate?
Decreased concentration of solutes:
- Renal Failure
- Pylophrenitis
- Diabetus insipidus*
- Acute tubular necrosis*
- Interstitial nephritis
What is diabetes insipidus?
Condition where you produce large amounts of urine, feel thirsty,
AKA POLYURIA
POLYDIPSIA
What is Acute tubular necrosis/
Acute tubular necrosis (ATN) is a medical condition involving the death of tubular epithelial cells that form the renal tubules of the kidneys. ATN presents with acute kidney injury (AKI) and is one of the most common causes of AKI. Common causes of ATN include low blood pressure and use of nephrotoxic drugs.
What does Urine Osmolarity measure?
Number of dissolved particles in urine
It’s more accurate than SG
Useful in diagnosing diabetes insipidus, diagnosing dehydration status
What can high Urine Osmolarity indicate?
- Congestive Heart Failure
- Dehydration
- Acute Kidney Injury
- High glucose
What can LOW Urine Osmolarity indicate?
- Excessive fluid intake
- Kidney failure
- Renal tubular necrosis
What should urine not contain (measured on dipstick)
- Proteins (proteinuria)
- Albumin (albuminuria)
- Red blood cells (haematuria) (small amount = grey /smokey)
- White blood cells
(they’re too large particles)
- glucose (glycosuria)
- keytones - associated with weight loss & diabetes
- nitrites -
Urinary tract infection - what is urine like?
What is the most common cause?
What CAN show on dipstick?
Smelling bad - bacteria acting on urea to increase ammonia levels
Cloudy urine - due to exudate (infection, increased calcium or phosphates)
90% of UTIs are caused by Gram Negative Bacteria which produce nitrate reductase, an enzyme that breaks down nitrate
Dipstick - nitrites CAN show
When WBC count is high?
= inflammation in urine or
Bacterial UTI - bladder or kidney infection
Lab tests - serum blood
Renal disease - mega principle? - elevated electrolytes e.g. potassium, sodium - elevated urea in bloods - elevated creatinine in bloods -
ACIDOSIS
Urine Osmolarity
- normal range
- what does lower score mean?
Normal is 270-300 mOsm/kg water
Lower - fewer particles in urine - less concentrated
associated with overhydration, oedema
Higher - ADH (antidieretic hormone)
deficient fluid volume, dehydrated
Hypovoalemic Shock - definition
Hypovoalemic shock refers to a medical or surgical condition in which rapid fluid loss results in multiple organ failure due to inadequate perfusion/ poor oxygen delivery
Hypovoalemic Shock
Pre-renal renal failure cause of AKI
Two forms of Hypovoalemic Shock - define!
‘Absolute’ is due to a lower circulating blood volume for a given vascular capacity e.g Hemorrhage, trauma,post op bleeding
‘Relative’ is expanded vascular capacitance for a given blood volume e.g sepsis, anaphalayxis, drops BP, drops perfusion, … internally hypovoalemic
Hypovoalemic Shock - relevance
In almost all medical and surgical emergencies, consider hypovoalemia to be the primary cause of shock until proven otherwise. RCUK 2015
By far the most common type of shock in children
Shock and Blood pressure
Urine output reflects to a degree your caridovascular function - reflective of cardio output - perfusion to kidney is good
Perfusion poor (due to shock) - may have symptoms of renaldysfunction
When should you be worried about urine output?
When is less than 0.5ml/kg/hour, AKA oliguria
When should you be worried about urine output? (as a principle)
When is less than 0.5ml/kg/hour, AKA oliguria
How is urine produced?
Via glomerular filtration (125ml per min)
Relies on relatively high perfusion pressure within the glomerular capillary and adequate blood flow
What autoregulates urine output?
Pre-glomerular afferent arteriole until the mean arterial pressure falls below 80
What regulates urine output when blood pressure is low?
Hormonal control
- (renananti intensive system? mystery word) e.g. Aldosterone
ADH - Anti-dieretic hormone
Why does urine output fall when perfusion to kidney is reduced?
Renal system responds to shock by stimulating an increase in RENIN secretion from the juxtaglomerular apparatis. Renin converts angiotensin to angiotensin 1, which is subsequently converted to angiotensin 2.
–> vasoconstriction and stimulation of aldosterone …
leads to SALT & WATER conservation - retain instead of excrete.
What are the 2 x main effects of angiotensin 2?
Vasoconstriction of arteriolar smooth muscle and stimulation of aldosterone secretion by the adrenal cortex.
ADH (anti-diretic hormone)
Where is is released from, and when?
What does it do?
ADH is released from the posterior pituitary gland in response to a decrease in BP (detected by baroreceptors) and a decrease in SODIUM concentration (as detected by osmorecepetors)
Indirectly leads to an increased reabsorption of water and salt by the distal tubule, the collecting ducts, and the loop of Henle
Critical pressure ?
pressure less than 65 (or sometimes lower than 80) - > will produce kidney injury
Triad of three variables freq. mentioned in pathophysiology world
Cardiac output - reflects cardio function, normal is stroke*rate = 5
cardio output - falls
pH - normal is 7.35-7.55 - renal prob=acidotic
aerobic to anaerobic -> lactic acid, c02 functions as acid
PaO2 - normal 11-14 kilopascals
Hypovoalemic shock - lose red blood cells, less capacity, o2 falls
What amount of cardiac output goes to kidneys each minute?
20-25%
1999 Goldhill
Respiritatory rate is the most sensitive predictor of impending deterioration and that rate, depth and ease of respiriations needs to be assessed
BUT - poor urine output VERY important
Hypovoalemic shock - exists as a spectrum,
Early?
Late?
Early - subtle pathophysiological tissue insults
Late - multi-system organ dysfunction
How to assess hypovoalemic shock?
(Assess for safety, PPE, early call for help)
Airway:
Breathing(LLF): fast resp due to acidosis (phrenic nerve stimulation),
Circulation: decreased blood pressure (cardiovascular collapse) cold hands (poor perfusion), poor urine output due to poor perfusion
Increased HR due to adrenaline release
Increased blood glucose - glycogen->glucose in liver, tehn released.
Nausea and vomitting due to pain OR blood redirection to major organs (big GI changes- ++fluid)
Disability: Consciousness impaired due to hypoxia
Exposure:
Objective way to assess hypovoalemic shock?
Full blood count, repeated a few hours on. If red blood cells count remains the same, can’t be bleeding
