Renal Flashcards
Kidney functions
Fluid, pH, ion homeostasis
Waste removal- urea, uric acid, creatinine, meds, toxins
Endocrine- RAAS system, EPO, 1,25 D3–> active vitamin D, Prostaglandin production
Hypovolemic urine production
SNS and angiotensin II–> vasoconstrictive decrease in GFR and increase in Na+ reabsorption
Aldosterone increases Na+ reabsorption
ADH increases H2O reabsorption
Hypervolemic urine production
ANP increases GFR via vasodilation
Reduced SNS and angio II allow vasodilation and Na+ excretion
Increased cap hydrostatic pressure discourages Na reabsorption
Decreased aldosterone decreases Na reabsorption in the DCT and CD
No ADH leads to H2O being impermeable to the CD
Normal renal autoregulation
about 80-200 mmHg
Most anesthetic agents lead to
Decreased GFR, UO, RBF, and e-lyte excretion
All major kidney functions affected
Surg/Anesthesia effect on ADH, Aldosterone, RAAS system
Increase in ADH–> decreased UO
Increase in Aldosterone from baroreceptors detecting volume depletion
Hypotension (under 80mmHg) leads to a release of renin and further renal vasoconstriction
Prostaglandins have what effect on the renal system
Protective against renal ischemia
Ischemia, renal hypotension, stress, promote their production
Oppose action of angio II, SNS, ADH,
Avoid ketorolac in pts at risk for medullary ischemia
Low dose dopamine is
voodoo medicine
T4-T10 sympathectomy will
Decrease catecholamines, renin, and ADH
Need fluid boluses to maintain RBF and GFR
Which gas can create compound A
Sevo
Maintain flows over 2L
Which gases have negligible levels of free fluoride ion from metabolism
Iso and Des
Methoxy>Enflu=Sevo are the worst
No evidence Sevo cause injury though
PPV
More PIP/PEEP, less RBF/GFR/UO
Hydration will largely overcome this
Periop oliguria is defined as
< 0.5ml/kg/hr of UO (<30ml/hr as a general number)
Pre-op eval
HTN?
DM, MI, CHF?
Meds
Dialysis- pre/post weight, how much fluid off, when was last, e-lyte status
Renal function tests
GFR:
BUN (10-20mg/dl)
Plasma Cr (0.7-1.5mg/dl)
Cr clearance (110-150ml/min)
Tubular function: Urine spec grav (1.003-1.03) Urine osmo (38-140mOsm/L)
BUN
Inverse to GFR, >50 is indicative of decrease GFR
Not as sensitive as Cr
Can be abnormal, but GFR ok due to- high protein diet, GI bleed, fever, dehydration
Plasma Cr
8-17 hour lag after a GFR change
Suggestive of ARF
50% increase indicates 50% decrease in GFR
Cr clearance
Index of GRF
Most reliable ESTIMATE of GFR (don’t forget about Inulin aka gold standard for calculating GFR)
less than 25ml/min indicates moderate disease, less than 10 needs dialysis
Disadvantage- needs 2-24hr urine collection
Chronic RF Hgb hovers around
5-8g/dl
PT, PTT, bleeding time in CRF, reason and Tx
increased bleeding despite normal PT, PTT, and BT- cause is defective vWF
Give DDAVP 0.3-0.4mg/Kg over 30 minutes or cryo, also have blood warmer ready to go
Hyperkalemia common, what EKG changes does it produce
Peaked T, long PR, long QRS, ST depression
HB and V-fib can result
HyperMg leads to
CNS depression and coma
high or low pH in CRF
low, can’t excrete H+ ions
CXR for
HTN CV disease, pericardial effusion, uremic pneumonitis
Dig tox EKG
Short QT, ST depression
Hypocalcemia EKG
Long QT
RF and drugs
Anemia, low serum protein, e-lyte changes, fluid retention, changed cell membrane dynamics all affect drugs
Drugs excreted by the kidney unchanged are CONTRAINDICATED, like gallamine, phenobarbital
Common anesthetic drugs to use with caution in RF
Thiopental- high PB
Midazolam- 60-80% renal clearance, high PB
Dexmedetomidine- high PB
Opioid of choice in RF
Fentanyl
Remi also ok
Bad opioids in RF
Meperidine, morphine, hydromorphone
Muscle relaxants to avoid in RF
d-tubo, metocurine, gallamine, pancur, pipecur, doxacur
Vec, roc ok (30% renal), but may see longer effect
Extra caution with succs because
K is released! Only use if K is normal, but probably want to avoid it
