GU Flashcards
What are the two types of nephrons?
corticol- excretory, regulation functions
juxamedullary- concentration, dilution of urine
Characteristics of the Nephron
functional unit of the kidney
each kidney has one million nephrons
some nephrons are held in reserve
Describe the characteristics of the glomerulus
filtering point for the blood
3 layers - endothelium, basement membrane, epithelium
what is the bowman’s capsule?
holding area for filtrate
proximal tubule
about 80% filtrate returned by reabsorption
loop of henle
filtrate (urine) becomes concentrated,
ascending limb: chloride removed, sodium dragged
distal tubule
reabsorption sodium
secretion of potassium, hydrogen ions, uric acid
What is the hilum?
where the blood vessels and ureters enter and exit the kidneys
What are the four primary roles of the kidney?
filtration - glomerulus
reabsorption - tubules
secretion - tubules
excretion - ureters
Describe the permeability of the loop of henle
the descending loop is only permeable to water, whereas the ascending loop is only permeable to solutes
Describe how the basement membrane helps with filtration
it is negatively charged which helps filter by repelling positively charged proteins and RBCs
What is meant by renal selective reabsorption?
selective reabsorption of sodium, amino acids, and glucose are secreted by the filtrate back into the blood. All glucose is reabsorbed in a healthy state
What is the difference between afferent and efferent arterioles?
afferent - supply blood to each glomerulus
efferent - forms peritubular capillaries, reabsorbs water and solutes as required
How much of the cardiac output is used by the renal system in a resting state?
20-25% or cardiac output
Describe the juxtaglomerular apparatus
glomerular blood pressure regulation accomplished by mechanoreceptors and chemoreceptors
regulates GFR by adjusting diameter and resistance of afferent and efferent renal arteries to act as a valve to maintain a constant MAP
How do the kidneys attempt to maintain adequate perfusion pressure over a wide range of blood pressure?
in hypotension, afferent arteriole dilates and efferent constricts. The opposite happens in hypertension
How does the kidney help to maintain homeostasis?
elimination and clearance of metabolic wastes, water soluble drugs
fluid balance through urine formation, and water excretion
electrolyte balance
acid-base balance
What are the characteristics of the GFR?
rate at which filtrate is formed
in health 180L/24 hours (125ml/min), all but 1.5 is returned to the patient
dependent on blood flow but stable over a wide range of blood pressures
status of Glomerular filtration system is assessed by measuring GFR
What are the determinants of GFR?
blood flow
net filtration pressure (NFP)
What are the three forces of net filtration pressure?
glomerular hydrostatic pressure (60mmHg)
bowman’s capsule hydrostatic pressure (18mmHg)
glomerular colloid osmotic pressure (10mmHg)
Do you know which element is most commonly used to measure the adequacy of glomerular filtration rate?
creatinine - end product of protein metabolism that is always excreted in the urine in health
What are the characteristics of ADH?
antidiuretic hormone
secreted by posterior pituitary
negative feedback loops regulate ADH secretion
Give an example of how antidiuretic hormone works
dehydration - increased serum osmos
osmo receptors in the hypothalamus sensitive to serum osmolality
ADH increases permeability of collecting tubules to water for reabsorption
Describe the characteristics of renin
hormone secreted by juxtaglomerular cells
secreted by JGA when GFR falls
renin converts angiotensinogen (released by liver) to angiotensin I
Angiotensin I converted to Angiotensin II by Angiotensin convertin enzyme (found in lungs)
Angiotensin II
potent vasoconstrictor
stimulates secretion of aldosterone
Describe the characteristics of aldosterone
hormone secreted by the adrenal cortex
helps to maintain normal sodium composition
it helps conserve water because:
angiotensin II triggers secretion of aldosterone
promotes sodium reabsorption (distal tubules) and renal water reabsorption
kidneys reabsorb water and sodium
result? increased BP and decreased serum osmolalilty
Why assess the renal system?
- critical illness or injury may result in transitory or permanent renal issues
- patient may present with some degree of pre-existing disease/renal impairment
- critical care interventions/treatment may post threat to renal function
- 75% patients experience renal impairment in icu
What is oliguria?
low urinary output
less than 400ml/24 hours
What is polyuria?
excessive or abnormally large passage of urine
What is anuria?
absence of urinary output (<50mL/24 hours)
What is azotemia?
high levels of nitrogen containing compounds in the blood
What is the normal urine output?
0.5ml/kg/hour
What is the concentration of components of urine?
95% water, 5% solutes
What is included in the routine urinalysis?
colour, clarity odor pH glucose Ketones Protein
What do casts in the urine mean?
breakdown products of cellular materia
correlate: severity and type of renal damage
What do red cells in the urine mean?
it’s common, extra renal
if there is no trauma it is extra renal
What do white cells in the urine mean?
abnormal - infection
What do epithelial cells in the urine mean?
may indicate nephritis
What are the important facts about creatinine?
by-product of muscle metabolism
freely filtered - appears in serum in amounts proportional to body muscle mass
single most important indicator of GFR
amount excreted remains constant (with the exception of muscle wasting and sepsis)
What are the important facts about blood urea nitrogen (BUN)?
aka urea
waste product of protein metabolism
freely filtered, less reliable than creatinine
What causes abnormalities in BUN?
hypovolemia
increased protein intake
liver disease
trauma (crush injuries)
Discuss creatinine clearance
amount of blood cleared of creatinine in one minute - related to age, sex, size
24 hour urine/serum creatinine sent
in renal failure you will compare the level of creatinine in the blood to the level in the urine
Discuss serum albumin as it relates to renal function
manufactured in the liver
about 50% total plasma protein
responsible for colloid osmotic pressure
holds fluid in the intravascular space
predominant “serum binding” protein for drugs
enema occurs when hydrostatic pressure is greater than colloid osmotic pressure
hypoalbuminemia is common in ICU
Discuss serum osmolality as it relates to renal function
total concentration of particles in blood
depends mostly on serum sodium
glucose and BUN also affect serum osmolality
Increased pituitary release of ADH
What is important to remember about urine electrolytes?
there are no fixed normal values
kidneys vary the rates of electrolyte excretion
interpretation within the individual clinical context
How do urine electrolytes trend in acute kidney injury?
increase or decrease in sodium
increased chloride
increased potassium
decreased calcium
What are some non-invasice renal diagnostic procedures?
renal (abdominal) ultrasound - position, size, and shape, fluid collection and hydronephritis
CT scan - tumours, hemorrhage, necrosis
MRI - inflammatory processes, carcinoma
What are some invasive renal diagnostic procedures?
cystoscopy/cystogram - utrethra/bladder issues
intravenous pyelogram (KUB) kidneys compared
Renal Arteriogram - renal vasculature/blood flow - requires contrast which must be then excreted by the kidneys
What is the ratio for intra and extracellular water?
2/3 intracellular, 1/3 extracellular (75% interstitial, 25% plasma)
How does the body regulate body water?
thirst - hypothalamus, responds to intracellular dehydration
ADH - released in response to increased serum osmolality, kidneys resorb water to correct osmolality, urine output decreases
kidney - concentrates urine, excretes solutes
What are some sources of fluid loss?
GU system (60% of fluid loss is urine) GI - vomiting, diarrhea, surgical drains Infection - fever, increased metabolic demand, increased insensible losses Medication - diuretic therapy THird Spacing
How is fluid balance assessed?
admission/daily weights
1kg = 1 L fluid
accurate intake and output
hemodynamic monitoring
What can happen in positive fluid balance?
hypervolemia generalized edema dyspnea 3rd heart sound respiratory crackles
What can happen in negative fluid balance?
rapid, weak pulse
tachycardia
orthostatic hypotension
What are the characteristics of crystalloids?
a solution of sterile water with added electrolytes
low molecular weight
approximates mineral content of human plasma
examples: normal saline, lactated ringers
What are the characteristics of colloids?
a solution that contains water, electrolytes and colloid
high molecular weight
colloid does not freely diffuse
examples: albumin, pentastarches
Give some examples of crystalloids and their tonic state
normal saline - isotonic
.45 normal saline - hypotonic, (water enters the cell) can be given with hypernatremia
3% saline - hypertonic (water leaves the cell)
lactated ringers - isotonic, liver converts lactate into bicarb
D5W - isotonic when in the IV bag, but becomes hypotonic when in the vascular space because the dextrose is taken up so quickly thus free water left behind
How do colloids affect osmotic pressure?
increased oncotic pressure
What are the functions of sodium, where is it found, and what happens with abnormal levels?
function - neuromuscular function, acid-base balance, maintains osmolality in extracellular fluid extracellular cation abnormalities - behavior and mental status changes, muscle tremors, seizures
What are the causes and treatments of hyponatremia?
cause - vomiting, diarrhea, loop diuretics, excessive water intake
treatment - hypertonic saline
What are the causes and treatments of hypernatremia?
causes - fluid disturbances, dehydration, osmotic diuretics
treatment - free water to dilute the sodium
What are the functions of potassium, and where is it found?
intracellular cation balance maintain by intake and renal excretion function - acid/base, fluid balance, transmission of nerve impulses
What are the causes and treatments of hypokalemia?
cause - diuretics, renal dysfunction, and GI losses
treatment - potassium chloride - controlled IV intake, or OG/NG administration
What are the causes and treatments of hyperkalemia?
cause - kidneys don’t excrete potassium, trauma (crush injury)
treatment - glucose, IV insulin (pushes potassium into the cells), calcium chloride (decrease myocardial irritability), dialysis, kayexalate
What are the functions of magnesium, where is it located, and what occurs with abnormal levels?
function - neuromuscular transmission, enzyme activation, energy/protein synthesis 2nd major intracellular cation abnormalities - muscle tremors/seizures/arrythmias
What are the causes and treatments of hypomagnesemia?
cause - increased loss (diuretics), decreased intake, pancreatitis
treatment - magnesium sulfate
What are the causes and treatments of hyperkalemia?
cause - increased intake (antacids), chronic renal failure, and rhabdomyolysis
treatment - hemodialysis
What are the functions of calcium, where is it located, and what happens with abnormal levels?
function - myocardial contractility, blood clotting cascade, transmission of nerve impulses both intra/extracellular abnormalities - variable - mental status changes, nausea, arrest, cardiac arrhythmias, tetany, hyper-reflexia
What are the causes and treatments of hypocalcemia?
cause - increased loss (diuretics), vitamin D deficiency
treatment - IV calcium gluconate or calcium chloride
What are the causes and treatments of hypercalcemia?
cause - thiazide diuretics, hyperparathyroidism, malignancy
treatment - IV normal saline, diuretics, pamidronate
As a result of hypocalcemia, you notice Chvostek’s and trousseau’s sign. What would you observe?
Chovestek’s sign - twitching of facial muscles elicited by tapping of facial nerve
Trousseau’s sign - carpopedal spasm caused by reduction of blood supply to the hand
helps to identify tetany due to hypocalcemia
What are the functions of phosphate, where is it located, and what happens with abnormal levels?
functions - formation of ATP, muscle contraction, neuromuscular conduction, WBC activity, platelet function
intracellular anion
abnormalities - muscle weakness, pruritis, myocardial contractility issues
What are the causes and treatments of hypophosphatemia?
causes - decreased intake, increased loss (diuretics), hypomagnesemia, sepsis
treatment - IV phosphate, OG/NG phosphate
What are the causes and treatments of hyperphosphatemia?
cause - increased intake (laxatives), decreased excretion (renal failure), rhabdomyolysis
treatment - calcium antacids, phosphate binders (amphojel)
Describe the ratio between increased creatinine and GFR
when creatinine values double, this often reflects a 50% decrease in GFR
What are the basic characteristics of acute kidney injury?
- sudden deterioration in renal function
- often associated with a fall in GFR (fluid and electrolyte/acid-base imbalance)
- progressive azotemia (increased creatinine/increased BUN)
- often a decrease in urinary output
What is the “rifle” criteria system?
Classification system used to determine risk of developing AKI in critical care R - risk I - injury F - failure L - loss E - end-stage renal disease
What is a hallmark characteristic of acute kidney injury?
metabolic acidosis
accumulation of unexcreted waste products
What are the three classifications of acute kidney injury?
pre-renal
intra-renal
post-renal
What are the characteristics of pre-renal kidney injury?
renal hypoperfusion
-when renal perfusion is compromised capacity for autoregulation is reduced
-decreased GFR
rapidly reversible because glomerulus and tubules are functionally intact
What happens if a pre-renal injury is left untreated?
ischemia
intra-renal acute kidney injury
How is a pre-renal kidney injury diagnosed?
history low urine output low urine sodium increased urine osmolality increased urine specific gravity
What are the rules of management and treatments for pre-renal acute kidney injury?
- identify at-risk patients
- maintain hydration
- maintain normotension
- ensure adequate fluid resuscitation (crystalloid or colloid)
- IV lasix
- monitor serum electrolytes
- optimize cardiac function after fluid resuscitation with inotropes and vasopressors
What are the important characteristics of acute intra-renal injury?
when the internal filtering structures are affected
glomerulonephritis
interstitial nephritis
acute tubular necrosis can happen which is the death of tubular cells
What are the two types of intra-renal failure?
nephrotoxic and ischemic
Describe nephrotoxic intra-renal failure
affects epithelial cells
can regenerate after nephrotoxic injury resolved
can be caused by antibiotics, heavy metals, and contrast dyes
Describe ischemic intra-renal failure
can extend to basement membrane of nephron
membrane cannot regenerate
can be caused by crush injury, septic shock, hypotension
How is an intra-renal injury diagnosed?
history
physical examination - CVP, edema
Imaging - renal ultrasound
Urine studies - sediment - obtain samples prior to fluids or meds
What are some treatments for nephrotoxic intra-renal injury?
monitor antibiotic levels maintain hydration acetylcystine IV sodium bicarbonate maintain normotension
What are the top three aminoglycoside nephrotoxic drugs?
tobramycin, gentamycin, and vancomycin
Who is at risk for a contrast dye induced intra-renal injury and what will you see?
diabetic
underlying renal failure
elderly
volume depleted patients
you will see increased serum creatinine more than 25% from baseline within 48-72 hours of exposure
What are the treatments for ischemic intra-renal injury?
identify at risk patients
aim for MAP greater than 60mmHg to maintain autoregulation of afferent/efferent arterioles
maintain hydration
maintain normotension
Describe the characteristics of post-renal injury.
not common
obstruction past the kidney
retrograde pressure decreases GFR which then dilates collecting system, compressing and damaging nephrons
will affect both kidneys
How are post-renal injuries diagnosed?
history low or no urine output increased serum creatinine, BUN, osmolality increased urine sodium variable specific gravity
What are the treatments of post-renal injury?
foley cath bladder scanning irrigation of foley consultation for general surgery/urology diuretics - mainstay of treatment
What are the five classifications of diuretics?
loop osmotic thiazide potassium sparing carbonic anhydrase inhibitors
Give the action, considerations and an example of loop diuretics.
lasix
inhibits sodium reabsorption in the loop
considerations - hypokalemia, hypovolemia, transient deafness due to ototoxicity
Give the action, considerations and an example of osmotic diuretics.
Mannitol
inhibit sodium and water reabsorption
considerations - dehydration, monitor for increased serum osmolality, electrolytes disturbances, urinary retention
Give the action, considerations and an example of thiazide diuretics
hydrochlorothiazide
inhibits sodium reabsorption
considerations - hypokalemia, leukopenia, thrombocytopenia, rash
Give the action, considerations and an example of potassium sparing diuretics
spironolactone (aldactazide)
inhibits aldosterone, decreased sodium reabsorption and increased potassium reabsorption
considerations - hyperkalemia, hyponatremia, may be given with thiazides for increased diuresis
Give the action, considerations and an example of carbonic anhydrase inhibitors
acetazolamix (diamox)
inhibits carbonic anhydrase, inhibits reabsorption of sodium and bicarb, facilitates excretion of bicarb
considerations - hyperchloremic (metabolic) acidosis
How do vasoactive drugs impact acutely injured kidneys?
vasoactive drugs potentially increase renal blood flow therby increasing renal protection.
Describe the pathophysiology of chronic renal failure, causes and treatments
slow, progressive, irreversible deterioration in renal function that leads to end-stage renal disease
remaining functional nephrons can no longer compensate
causes - hypertension and diabetes
treatment - life-long dialysis therapy
What is rhabdomyolysis
after skeletal muscle injury, damage results in the breakdown of muscle cells
cells leak toxic contents into circulation including creatine kinase, myoglobin and uric acid
this interferes with filtration at the glomerulus by damaging the tubules which then leads to renal failure
What are the two types of rhabdomyolysis?
traumatic - falls, crush injuries
non-traumatic - exertional such as marathon running, weight lifting, or non-exertional such as alcohol or drugs
How is rhabdomyolysis diagnosed?
patient history - muscle pain, swelling, stiffness
urine colour and volume - commonly 1st clinical sign of rhabdo, dark red, coca-cola colored, decreased urine output
serum CK - excessively elevated
serum electrolytes - elevated potassium and phosphate
urinalysis - positive for blood
What is the medical management of rhabdomyolysis?
IV fluid - large volumes (200-500ml/hr) to maintain kidney perfusion and dilute myoglobin
alkalinization of urine with IV sodium bicarb
diuretics to promote diuresis of toxins
What are the management criteria for patients with rhabdomyolysis?
maintain IV therapy, observe urinary output, decrease CK level, trend the potassium level
when all else fails, dialysis therapy to maintain clearance of waste products, recover renal function, optimize fluid balance, and maintain acid-base balance.
Briefly describe peritoneal dialysis
sterile dialysate fluid instilled into abdominal cavity via a catheter
semi-permeable membrane in the peritoneum is bathed by solution
solute and fluid removal via osmosis, diffusion and filtration
fluid then drained from abdomen
What is the difference between IHD and CRRT?
IHD - patient must be stable because it stresses the CV system, quick and efficient, inexpensive, intermittent - large volumes removed in a short period of time
CRRT - patient can be stable or unstable, less stress to CV system, time-consuming, more expensive, continuous (hourly calculation of fluid balance possible
What physical findings indicate renal dysfunction?
htn engorged neck veins third heart sounds crackles pitting edema renal bruit
what is the difference between fluid volume deficit and dehydration?
deficit- both water and electrolytes together (diaphoresis, feces, urine)
dehydration - refers only to the loss of water
what is the difference between ionized and total calcium?
ionized - physiologically active calcium, available calcium
total - bound to protein and not available
why do we want to alkalinize the urine in rhabdomyolysis?
prevents myoglobin from breaking down into nephrotoxic metabolite
