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Normal BUN / Cre ratio
Does an individual's volume status affect BUN?
Yes, BUN is increased in a hypovolemic pt, but not necessarily b/c of decr RF
T or F, urea is only a reliable indicator of RF when protein catabolism is constant?
T, urea is a by product of protein breakdown
What non renal causes would incr BUN?
- high protein diet
- GIB (blood breakdown)
- trauma or sepsis (high catabolic rate)
What non renal causes would decr BUN?
starvation and liver dz
A BUN > ___ mg / dl indicates renal involvement?
Serum cre is directly prop to ______ and inversely proportional to ______.
Is BUN or Cre a better indicator of GFR?
If Cre doubles, then GFR is decr by?
Causes of falsely elevated cre levels
- large male
- cimetidine (inhibits cre secretion by renal tubules)
- ketoacidosis (ketone body interferes with lab testing)
T or F, if a geri pt has a normal Cre, this means their RF is normal?
F, since muscle mass decr by 5% / decade, their Cre is underestimated
What does it mean if the BUN / Cre ratio is greater than 10:1?
Pre-renal (hypovol) situation
What is the most accurate indicator of GFR?
Formula to est Cre cl from serum cre
- cre cl= (140-age) x IBW (kg) / 72 x serum cre
- multiplied by 0.85 if a female
Cre cl value for mild renal impairment
40-60 or 50-80 ml / min
Cre cl value for moderate renal impairment
25-40 or < 25 ml /min
Cre cl value for severe renal impairment
< 10 ml / min
What tests evaluate glomerular function?
BUN, Cre, proteinuria
What tests evaluate tubular function?
urine SG, urine osm, urine Na, glycosuria
Urine SG normal value
normal urine osm
- 50-1200 mosm/ L
- avg of 500-800 mosm/ L
What does a high urine Na tell us?
The tubular function is impaired and the tubules are unable to reabs Na
How can we differentiate causes of acute oliguria?
Look at urine osm and urine SG
What values for urine som and urine SG would be indicative of hypovolemia?
- Urine SG > 1.020
- Urine osm >500
- (body should be producing a conc urine to conserve water)
What values for urine som and urine SG would be indicative of ATN?
- Urine osm ~ 300 mosm / L
- Urine SG of 1.010
- conc ability of the kidneys is impaired
Earliest sign of diab nephropathy
Single most reliable predictor of postop renal dysfunction
pre-op renal func
Kidney dz is the __th leading cause of death in the US
What other factors can contrib to ARF
- hypoperfusion (blood loss, burns, sepsis, CHF)
- renal artery obstruction
- AAA or cardiac surg with CPB
- nephrotoxic drugs
T or F, GFR varies with size, gender, and age
- Abx (vanc, cephalosporins, aminoglycosides -gent)
- Anes agents- sevo, methoxy, enfl
- Chemo / immunosuppressive drugs
- Uric acid
- myoglobin (rhabdo))
- hemoglobin (hemolysis)
- Oxalate crystals
Over what time period does ARF develop over?
Hours to days
- Incr in serum cre by > 0.5 mg /dl over baseline cre
- this correlates with 50% decr in cre cl
Is ARF oliguric or non-oliguric?
It can be either
Is ARF acute or chronic?
It can be either
What UO is considered oliguria?
< 400 ml / day
- N/V, anorexia
- fatigue, AMS
- Vol overload
- hyperK, met acidosis
What types of pts are at risk for ARF?
- > age 60
- cardiac dz
- liver dz
Leading cause of M&M in ARF pts
ID issues (resp or GU infections)
Complications of ARF
- CV- HTN, CHF, pulm edema
- CNS- conf, somn, sz
- GI- anorexia, N/V, ileus, GIB
- peaked T's
- prolonged PR, QRS
hypovent, AMS, prolongation of NMB drugs
s/sx metabolic acidosis
hypotension, cardiac arrythmias, hyperK
Why is hypocalcemia associated with ARF
Cause(s) of pre-renal azotemia
- decr renal perfusion (hypovol, hypoten, decr CO, intrarenal VC)
- anything that impairs blood flow thru the kidneys
Pre-renal is assoc for ___% of renal failure cases?
Why will urea levels incr more than cre levels in pre-renal azotemia?
filtration rate is so slow that waste products get reabs, urea is smaller than cre so gets reabs
T or F, as long as RBF doesn't fall below 50% and the cause is corrected before there's cellular damage, this type of ARF is reversible
F, as long as RBF doesn't fall below 20%
Dx of pre-renal
- High ratio of BUN / Cre (>20:1)
- Low urine Na (low renal BF, decr GFR)
- conc urine
- Urine osm > 500 mosm/L
- incr renal perfusion
- ? renal dopa
causes of renal azotemia
- ischemia (hypoperf for > 30-60 mins) 50%
- nephrotoxicity 35%
- acute tubular interstitial nephritis or acute glomerular nephritis 15%
Primary site of injury in intrarenal azotemia
glomerulus, renal vessels, renal tubules, interstitium
T or F, the initial presentation of intrarenal azotemia is similar to pre renal due to decr RBF
Do most adults get oliguric or non-oliguric intrarenal azotemia
urinary tract obstruction (prosthetic hypertrophy, abd mass, or kidney stone)
Dx of intrinsic renal azotemia
- urine Na > 40 meq/L (poor tubular reabs and tubular functioning)
- urine osm 250-300 mosm/L
- BUN/ Cre ratio < 10:1
- way to categorize severity and prognosis of ARF by assessing serum Cre and UO
- categories: risk, injury, failure, loss, ESRD
chronic renal failure
decr in # of functioning nephrons
onset of CRF
3-6 mos to years
Leading cause of ESRD
DM, then HTN, then PCKD
T or F, ACEI may be renal protective and slow the progression of glomerular sclerosis
Causes of CRF
- primary glomerulopathies (glomulonephritis)
- glomerulopathies assoc with systemic dz (DM, amyloid, SLE)
- tubulointerstitial dz
- obstruction uropathy
GRF associated with CRF stages 1-5
- 1- GFR >=90
- 2- 60-80
- 3- 30-59
- 4- 15-29
- 5- < 15 or HD
Pts with CRF are relatively asymptomatic until renal function < ____% of normal
3 stages of adaptation in CRF
- 1) decr GFR and incr BUN and Cre (after a 50% decr in GFR)
- 2) K levels maintained until GFR decr to 10% of normal (incr aldosterone levels)
- 3) ECF volume regulation, but can be overwhelmed with excess volume or increase in PO Na intake
Common lyte dist in CRF
- hyper K
- hyper Phos
- Hyper Mg
- hypo Ca
Why does decreased serum albumin levels occur in CRF?
Damage to renal tubular epithelial cells and so albumin is lost in the urine
Why does met acidosis occur in CRF?
Kidney unable to eliminate non-volatile acids (H+)
Treatment of hyper K
- 10 ml 0f 10% calcium gluconate
- 10U insulin and 50 ml of D50
- 50-100 meq of bicarb
There are generally no s/sx of CRF until ___% of functioning nephrons remain
Why might polyuria and nocturne initially be seen with CRF?
Failure of countercurrent mechanism to concentrate urine
Heme manifestations of CRF
- anemia (decr erythropoitin)
- impaired WBC and Plt func
- uremic bleeding
What effect does anemia have on the oxyHgb dissoc curve?
Right shift (O2 is more easily given up to the tissues) due to acidosis and incr 2,3 DPG (decr RBC survival)
Pulm effects of CRF
- incr MV (compensate of met acidosis)
- interstitial edema
- pulm edema and pleural effusions
- Incr AA gradient
Endocrine effects of CRF
ins rx and secondary hyperPTH (due to hypocalcemia)
Neuro effects of CRF
- peripheral neuropathy
- autonomic neuropathy
GI effects of CRF
- GIB due to incr gastric acid secretion
- gastroparesis (? RSI)
What are the benefits of a native AVF?
better potency and lower rate of thrombosis
Native AVF grafts are preferred, what is the adv of synthetic grafts?
less time to endothelialize so can be used sooner
What is the goal wt for a HD pt upon entering the OR
2.5 kg above dry wt
MOA and example of an osmotic diuretic. Where in the tubules does it work?
- Inhibits water and solute reabs by increasing tubular osm
MOA and example of a loop diuretic. Where in the tubules does it work?
- Inhibits Na-K-Cl co-transport
- thick asc LoH
MOA and example of a thiazide diuretic. Where in the tubules does it work?
- Inhibit Na-Cl co-transport
- early DT
MOA and example of a carbonic anhydrase inhibitor diuretic. Where in the tubules does it work?
- inhibit H secretion and bicarb reabs, decr Na reabs
MOA and example of an aldosterone antagonist diuretic. Where in the tubules does it work?
- Inhibits aldosterone, decr Na reabs, decr K secretion
MOA and example of a Na channel blocker diuretic. Where in the tubules does it work?
- blocks Na entry into channels, decr Na reabs and K secr
What % of ESRD is associated with glomerulonephritis
inflammation, hematuria, RBC casts
- primary- inflammatory dz, may be IgA mediated or post-streptococcal
- or secondary- assoc with DM, HTN, SLE
Examples of tubulointerstitial renal diseases
- acute interstitial nephritis (WBC casts)
- chronic tubulointerstitial nephropathy
acute interstitial nephritis- type of renal disease, s/sx, cause
- WBC casts, sterile pyuria, rash, fever
- drugs, infection, autoimmune processes
Examples of tubular renal diseases
- Barttler's syndrome (pedi)
- Gitelman's syndrome
- Liddle's syndrome
- Fanconi's syndrome
- renal tubular acidosis
- pseudohypoaldosteronism type 1
Which of the tubular renal diseases are AD
- pseudohypoaldosteronism type 1
- Liddle's syndrome
renal cystic diseases are due to HTN, T or F?
F, they are inherited (AD or AR)
Examples of systemic dzs with renal involvment
What renal dzs are assoc with trauma
- rhabdo (myoglobin causes renal injury)
- adb compartment syndrome
Anesthesia agents assoc with renal injury
- enf and methoxy- fl induced
- sevo- compound A, vinyl halide induced
fentanyl, mso4, and demerol adjustments in dosage for decr GFR
- GFR > 50 ml / min- give normal dose
- GFR 10-50 ml / min- give 75%
- GFR < 10 ml / min give 50%
How should the dose of remi, alfent, and sufent be adjusted for GFR
give 100% of the dose for any GFR
What K level would warrant postponing elective surgery?
> 5.5 meq/L
NMB of choice for renal failure pts
How does anemia affect the BG solubility of the volatiles?
BG sol is decr (so incr speed of onset)
Why might ages agents have an incr effect in renal failure pts?
- Incr IV vol, so incr VD, but…
- decr clearance
- decr protein and protein binding, so
- increased levels of free drug
- uremia disrupts BBB, so more sensitive to sedatives
What meds should be avoided for kidney transplant surgery?
- Succ (hyperK)
- Toradol (nephrotoxic)
- Morphine (renal clearance of morphine 6-gluc)
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