Kidney Flashcards
Nephron
- functional unit of kidney
Renal cortex
- outer section
- contains:
1. glomerulus
2. bowman’s capsule
3. proximal tubules
4. distal tubules
Renal medulla
- inner section
- contains:
1. LOH
2. collecting ducts
Identify structures of nephron
Identify structures of kidney
6 functions of kidney
- Maintain ECF & composition
- aldosterone (Na+/H2O reabsorption)
- ADH (H2O reabsorbed but not Na+)
- K+, Cl-, Phos, Mg, H+, HCO3, glucose, urea - BP regulation
- RAAS - Excretion of toxins/metabolites
- Maintain acid-base balance
- Hormone production
- Blood glucose homeostasis
Hormones produced by kidney
- erythropoietin
- triggers for release: anemia, reduced IV vol, hypoxia
- stimulates bone marrow to produce erythrocytes - prostaglandins
- calictriol
- 25-hydroxycholecalciferol converted to calcitriol (active vit D)
- stimulates intestinal absorption Ca+
- tells kidney to reduce Ca+ & phos excretion
- increases deposition of Ca+ into bone - renin
hormone that controls plasma osmolarity
ADH
hormone that control ECF volume
aldosterone
2 organs responsible for acid-base balance
- kidney
- lung
Pathway of blood flow through kidney
afferent arteriole > glomerular capillary bed > efferent arteriole > peritubular capillary bed
Kidneys receive _______ % of CO
20-25%
Renal blood flow formula
RBF = (MAP - Renal venous pressure) / Renal vascular resistance
Renal cortex receives ____% of RBF
- 90%
- PO2 50 mmHg
Renal medulla receives ____% of RBF
- 10%
- PO2 10 mmHg
- more sensitive to ischemia
Pathway of blood through kidney
ARTERIAL
Renal a. > renal segment a. > interlobar a.> arcuate a. > interlobular a. > afferent arteriole > glomerular capillary bed > efferent arteriole > peritubular capillary bed
VENOUS
venules > interlobular vein > arcuate vein > interlobar vein > renal segmental vein > renal vein
RBF Autoregulation
- low renal perfusion > autoregulation increases RBF by decreasing renal vascular resistance > RBF increases
- too high renal perfusion > autoregulation decreases RBF by increasing renal vascular resistance > RBF decreases
RBF limits ~ 50-180 mmHg
6 mechanisms that autoregulate RBF
- myogenic
- JG apparatus + tubuloglomerular feedback
- RAAS
- prostaglandins
- ANP
- SNS
Most important contributors to renal autoregulation
- myogenic mechanism
- contricts/dilates afferent arteriole if renal artery pressure high/low - tubuloglomerular feedback
- JG apparatus in distal tubule b/t afferent & efferent arteriole detects Na+/Cl- composition in DCT & affects arteriolar tone
Kidney response to ischemia/sepsis/surgical stress
Vasoconstriction & Na+ retention
- SNS, RAAS, ADH
- decreased RBF, GFR UOP, Na+ excretion
RBF decreases by ____% per decade after the age 50
10%
JG apparatus
- located in distal tubule
- decreased RBF > decreased Na+/Cl= delivery to JG app (sensed by macula densa) > afferent arterioles dilate > GFR increases
- low Cl- delivery > renin released from juxtaglomerular cells > RAAS activates > AG2 constricts efferent arteriole > GFR increases
RAAS
Conditions that increase renin release
Aldosterone
- produced in zona glomerulosa of adrenal gland
- stimulates Na/K ATPase in principal cells of distal tubules & collecting ducts
- facilitates Na+ & H2O reabsorption & K+ & H+ excretion
- release is increased by high K+ & low Na+
- Conn’s dz = excess aldosterone (Na+ retention & K+ loss)
ADH (vasopressin)
- produced in the supraoptic & paraventriular nuclei of hypothalamus
- released from posterior pituitary gland
- 2 mechanisms that control release: increased osmolarity, decreased blood volume
- stimulates V1 in peripheral vasculature (vasoconstriction)
- stimulates V2 in collecting ducts- aquaporins reabsorption of H2O
Prostaglandins
- produced in afferent arteriole
- promote RBF
- arachidonic acid is liberated from cells in r/t ischemia, hypotension, NE, & AG2.
- NSAIDs inhibit cyclooxygenase & can reduce RBF by inhibiting production of vasodilating prostaglandins
natriuretic peptide
- atrial distension > ANP & BNP release
- inhibit renin release
- promote Na+/H2O excretion
dopamine receptors
- DA1 (kidney, splanchnic circ)
- DA2 (presynaptic adrenergic n. terminal)
- DA1: increase cAMP > vasodilation, increased RBF & GFR, diuresis, Na+ excretion
Fenoldopam
- selective DA1 agonist
- increases RBF
- renal vasodilator
- facilitates Na+ excretion
normal GFR
125 ml/min
glomerular filtration
- H2O, electrolytes, glucose freely filtered
- plasma proteins not filtered
- kidney disease destroys basement membrane which allows proteins to enter tubules
Net filtration pressure
NFP = glomerular hydrostatic P - Bowman’s capsule hydrostatic P - Glomerular oncotic P
Most important determinant of GFR
glomerular hydrostatic pressure
BP
- increased MAP increases GFR
- decreased MAP decreases GFR
Constriction of afferent arteriole _____GFR
reduces
Dilation of afferent arteriole ______ GFR
increases
Constriction of efferent arteriole
- mild reduces flow toward peritubular capillaries & increases GFR
- excessive reduces RBF & GFR
Dilation of efferent arteriole
increases flow towards peritubular capillaries & reduces GFR
reabsorption
substance transferred from tubule to peritubular capillaries
secretion
substance transferred from peritubular capillaries to tubule
excretion
substance removed from body in urine
urine excretion rate
= filtration - reabsorption + secretion
proximal convoluted tubule
- 65% Na+ reabsorption
- 65% H2O reabsorption
- 65% K+, Cl-, HCO3 reabsorption
Diuretics:
- acetazolamide, dorzolamide (carbonic anyhdrase inhibitors)
- osmotic diuretics: mannitol (also LOH)
descending LOH
- highly permeable to H2O (20% reabsorbed)
- more concentrated w/ Na+
- LOH = countercurrent multiplier - creates osmotic gradient
- vasa recta = countercurrent exchanger = maintains medullary osmotic gradient
ascending LOH
- NOT permeable to H2O
- Na/2K/Cl co transporter
- Na+ reabsorption
- more dilute
Diuretics:
- Loop diuretics (furosemide, bumetanide)
DCT
- 5% Na+ reabsorbed
- K, Cl, HCO3 reabsorbed
- late DCT impermeable to H2O except in presence of ADH or aldosterone
- JGA lives here
- PTH promotes Ca+ reabsorption
Diuretics:
- thiazide (HCTZ, chlorthalidone, metalazone, indapamide)
Collecting duct
- 5% Na+ reabsorbed
- aldosterone & ADH act here
Diuretics: K+ sparing (spironolactone, amiloride, triamterene)
carbonic anhydrase inhibitors
- inhibit carbonic anhydrase in proximal tubule
- reduces HCO3, Na+, H2O reabsorption
- ex: acetazolamide, dorzolamide
osmotic diuretics
- inhibit H2O reabsorption in proximal tubule (primary) & LOH
- pull ECF volume into intravascular space
- ex:
1. Mannitol 0.25-1 gram/kg
2. glycerin
3. isosorbide
Loop diuretics
- inhibit Na/K/2Cl transporter in ascending LOH
- ex: furosemide, bumetanide, ethacrynic acid
thiazide diuretics
- inhibit Na/Cl co-transporter in DCT
- activates Na-Ca antiporter (increases Ca+ reabsorption)
- hyperglycemia
- HCTZ, chlorthalidone, metolazone, indapamide
K sparing diuretics
- inhibit K secretion & Na reabsorption in collecting ducts
- spironolactone subclass - inhibit aldosterone > inhibit K secretion/Na reabsorption in collecting ducts
- amiloride, triamterene
Best indicator of GFR
Creatinine clearance
Best test of tubular function
urine osmolality
prerenal AKI
- cause = hypoperfusion
- Tx: IVF, HD support, PRBCs
- avoid NSAIDs
intrinsic AKI
- cause = parenchymal dysfunction
- normally ATN -ischemia, drugs
- contrast, abx, NSAIDs
- Tx: restore perfusion, supportive
postrenal AKI
- cause = obstruction
- clogged foley, ureteral stone, neurogenic bladder
- Tx: relieve obstruction
most common cause CKD
DM
second most common cause CKD
HTN
stages of kidney disease
uremic syndrome
-s/s = anemia, fatigue, n/v, anorexia, coagulopathy
uremic bleeding
- at risk for increased bleeding
- elevated bleeding time
- PT/PTT/PLT normal
- 1st line tx = desmopressin
- dialysis w/i 24 hours of surgery (improves bleeding time)
Other s/s CKD
- anemia
- HTN
- CAD
- CHF
- gap metabolic acidosis
- hyperkalemia
- renal osteodystrophy
- ANS dysfunction
- CNS s/s
- infection
indications for dialysis
- volume overload
- hyperkalemia > 6
- severe metabolic acidosis
- symptomatic uremia
- OD w/ a drug that is cleared by dialysis
Impaired renal function: anesthetic drug considerations
- sevo Compound A
- sux ok w/ normal K+
- cisatracurium > atracurium (benzyliso’s)
- roc, vec, pancuronium prolonged DOA
- sugammadex not recommended
- morphine = resp depression
- meperidine = sz
- hydromorphone = sz
- fentanyl, sufentanil, remi better choices
- precedex safe
prevention of contrast-induced nephropathy
- nonionic/low osmolar contrast
- lowest volume of contrast possible
- no other nephrotoxic drugs
- NS IVF before contrast dye
- HCO3
- n-acetylcysteine
Compound A
- produced when sevo is exposed to soda lime
- FGF of 1 L/min safe for up to 2 MAC hours
nephrotoxic agents
- amnioglycosides (gent, tobramycin, amikacin)
- amphotericin B
- vanc
- sulfonamide
- tetracylcines
- cephalosporins
- NSAIDs
- caclineurin inhbitors
- IVP dye
- sevo
- myoglobin
TURP
- spinal preferred (T10 level)
- height of solution bag no more than 60 cm above OR table
- limit surgery to 1 hour
- irrigation solution complications
- distilled water = TURP syndrome (low Na+, hemolysis, hemoglobinuria)
- glycine = blindness
- sorbitol = hyperglycemia
- LR/NaCL = electrocution (monopolar)
- complications
1. TURP
2. bladder perforation (abd/shoulder pain) - supportive, H/H, transfusion, suprapubic cysto, ex lap
3. bleeding
4. hypothermia
TURP syndrome
- absorption of hypo-osmolar irrigation solution
- S/S: HTN, bradycardia, AMS
- circulatory overload
- Na < 110 = SZ
- Tx:
1. O2 & CV support
2. tell surgeon to stop
3. electrolytes, Hct, Creat, gluc, EKG
4. Na > 120 = restrict fluids, give lasix
5. Na < 120 = 3% NaCl at 10 ml/hr
6. versed for sz
7. intubate if pt has difficult w/ oxygenation
extracorporeal shock wave lithotripsy
- delivers shocks in rapid succession to break up stone
- absolute contraindications:
1. pregnancy
2. risk of bleeding - relative contraindications:
1. PM/AICD
2. UTI
3. obesity
4. calcified aneurysm or aorta or renal artery - complications: R on T phenomenon, bruising, hematuria
percutaneous nephrolithotripsy
- nephrostomy tube to access stone& ureteral stents placed
- prone
- GETA
- irrigation fluid used
- pneumo complication
laser lithotripsy
- uses laser to break up stone
- laser precautions
- irrigation fluids used
- lithotomy
