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Flashcards in Renal II Deck (18)
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1

How does anesthesia affect renal function?

  • Neuraxial
    • T4-T10 sympathectomy decreases release of catechols, renin, and vasopressin
      • maintain RBF and GFR with fluid boluses
  • Surgical stress response- usually canges in RBF, not the actual anesthetic agent, esp in major surgery, CPB, hypovolemia, or aortic cross clamping
  • Pharmacology- most agents decrease GFR and UOP but it is resolved w/emergence
    • d/t CV depression
    • prehydrate and attenuate against stress response
    • renal autoreg and hormonal function usually maintained
  • IA- can be renal protective
    • nephrotoxic concern with free Fl- in older agents (negligible in Iso)
  • Ventilation- increased pressure on IVC, pulmonary arterial, and renal venous pressures caused by high PIP and PEEP can decrease RBF, GFR, and UOP

2

General info about chronic kidney disease:

What is it?

When is HD required?

What is most common cause?

  • CKD is the decrease in the number of functioning nephrons
    • 30% of nml nephrons can eliminate the full load of waste products, but will become overloaded and overworked
    • blood flow to the functioning flomerulus increases 50-100%
    • wastes accumulate in the ECF
    • tubular solutes arent reabsorbed, act as an osmotic diuretic 
  • HD required when Cr >3 or GFR <30
  • Most common cause: DM
    • second: HTN

3

What are the physiologic effects of CKD?

(10)

  • generalized edema
  • high levels of nitrogens (Cr, urea, uric acid), phenols, sulfates, phos, K
  • osteomalacia and secondary hyperparathyroidism
    • VitD must be converted to allow Ca++ absorption from intestines
    • accumulation of phos causes decreased Ca++ levels and increased PTH secretion causing bone resorption 
  • Prurities- cause unknown
  • anemia (Hgb 5-8)- decreased EPO production (compensated)
  • Coagulopathies- decreased circulating vWF
    • increased risk for GI bleed
    • tx with desmopressin, EPO, cryo, or estrogen therapy
  • altered electrolyte balance
  • systemic HTN- d/t volume expansion and RAAS activation
    • goal: <130/85 usually w/ ACEI or ARBs
  • CNS abnormalities
  • infections- most common cause of death

4

What is considered an AKI?

What increases the mortality rate?

  • AKI
    • increased Cr by >0.5
    • 50% decrease in Cr clearance
    • may be oliguric or nonoliguric
  • High mortality rate (50-80%) if:
    • HD is required
    • Multiple organ dysfunction occurs
    • hypotension occurs
    • respiratory failure ensures
  • **No elective surgery, if emergency procedure, keep MAP > 65

5

What patients are at high risk of an AKI post-anesthesia?

  • pre-op renal disease (#1)
  • CHF or CAD
  • intra-op cardiac events (inadequate BP or CO)
  • sepsis or emergency surgery, trauma, MODS
  • elderly
  • ESLD
  • hypovolemia
  • nephrotoxic exposure
  • CPB
  • aortic cross clamping
  • liver/kidney transplant
  • nephrectomy

6

What are the different categories of AKI?

  • Prerenal- d/t decreased blood supply to kidneys
    • CHF
    • low CO/BP
    • low blood volume
  • Intrarenal- d/t severe ischemia, nephrotoxic exposure, parenchymal disease
    • TALOH is esp vulnerable- necrosis occurs, releasing debris into tubules and blocking
    • Acute glomerulonephritis d/t infection (strep)
      • antibodies develop that are insoluble and get trapped in glomerulus and inflammatory process damages kidney
  • Post renal- d/t obstructionof urinary collecting system by renal calculi, etc
    • if cause is found w/in a few hours, normal function can be restored

7

What are the physiologic effects of AKI?

  • retention of water, waste procucts, and electrolytes in the blood and ECF
  • HTN, CHF, pulmonary edema
  • diluted RBCs--> Hct 20-30%
  • GI bleed- anorexia, nausea, ileus
  • hyperkalemia/metabolic acidosis (can be fatal)
  • neurologic changes
  • uremia induced immune suppression leading to infection

8

How can AKI be prevented and treated?

  • Fluid resuscitation
    • no data supporting colloids vs crystalloids
    • mannitol may be helpful in transplants w/approp fluid bolus
    • N-acetylcysteine + IVF may be protective agains contrast dye
  • Vasopressors
    • increased SBP to decrease renal SNS and RAAS and increase plasma hydrostatic pressure in glomerulus to increase GFR
    • NE used in septic pts improves GFR and UOP
    • dopamine/loop diuretics not supported
  • Drug dosing
    • use pharmacy guidelines-- helpful to know CRcl/GFR
    • reduce doses of drugs cleared unchanged by the kidneys and GFR <50
    • consider the Vd
    • protein binding is altered
      • acidic drugs = less binding
      • basic drugs = more binding

9

Anesthetic drugs in the pt with an AKI:

propofol, ketamine, etomidate

midaz

precedex

morphine

meperidine

hydromorphone

fentanyl, alfent, sufent, remi

long acting NMB

roc/vec

cisatra, atracurium

succ

  • TPL- highly protein bound, high free fraction with AKI
  • prop, ket, etomi- no major change
  • midaz- active metab 60-80% renally cleared; avoid repeat dosing
  • precedex- highly PB, longer sedation with AKI
  • morphine- avoid repeat dosing d/t potent, highly PB metabolite
  • meperidine- avoid d/t metabolite
  • hydromorphone- accumulation of active metab, avoid repeat dosing
  • fent, sufent, alf- all good choices
  • long acting NMB- avoid
  • roc/vec- single dose ok, but prolonged effect possible
  • cisatra, atracurium- normal dosing
  • succ- check K first

10

What drugs are nephrotoxic?

When would you want to avoid them especially?

  • aminoglycosides
  • radiocontrast dyes
  • cyclosporin
  • amphotericin B
  • Especially avoid if given with NSAIDs, DM, shock, or hypovolemia

11

What tests can be used to measure GFR?

  • GFR- best b/c it parallels nephron function
  • BUN (5-10) - >50 = decreased GFR
    • varies inversely with GFR
    • depends on urea production (metab of ammonium in the liver)
    • can be altered by:
      • high protein diet
      • GI bleed
      • dehydration
  • Creatinine (0.5-1)
    • varies inversely from GFR (2x increase in Cr = 50% decrease in GFR)
    • specific indicator b/c it is freely filtered and not reabsorbed
    • depends on muscle mass, physical activity, and protein intake and catabolism
  • Creatinine clearance (110-150, <25 = moderate disease)
    • most reliable estimate of GFR
    • men have higher levels d/t muscle mass
    • elderly lower d/t decreased muscle mass; an elevated CrCl is more concerning

12

What tests are done to test tubular function?

  • Urine specific gravity (1.003-1.030)
  • Urine Osm (38-1400)
  • Urine Na

13

What are the goals for the HD patient?

  • avoid infection and CV events
    • 25% of annual mortality rate for all dialysis pts
  • perserve vascular access
    • avoid IV in non-dominant arm and upper arm
    • AV fistula usually cephalic vain anastomosed to radial artery
    • emergency access = double lumen dialysis catheter inserted into the jugular or femoral vein

14

What are the different types of dialysis?

  • Hemodialysis (most common)
    • circulation through extracorporeal circuit that filters waste products into dialysstae
    • purified blood is pumped from the dialyzer into the AV fistula
  • Peritoneal dialysis
    • peritoneum acts as a blood filter
    • catheter inserted into abdomen and dialysate is pumped into abdominal cavity; waste products move from blood into dialysate solution
    • after 6-24 hours, waste filled dialysate is drained from abdomen and replaced with clean dialysate

15

What are the side effects of dialysis?

  • hypotension- tx with decreased ultrafiltration rate or NS bolus
  • hypersensitivity
  • hypokalemia- b/c most K is in the ICF after dialysis, equilibration post-dialysis takes time
  • cramps, HA, N/V
  • anemia
  • infection

16

What drugs are completely dependent on renal elimination?

  • gallamine, metocurine
  • digoxin, inotropes
  • aminoglycosides
  • vancomycin
  • cephalosporins
  • PCNs

17

What are the systemic concerns seen in renal patients?

respiratory

CV

renal

hematologic

endocrine

CNS

  • Resp- infection = high M&M
  • CV
    • electrolyte imbalances (high K, Mg; Low Ca)
    • metabolic acidosis
    • unpredictable IVF status
    • anemia; increased CO, Oxyhgb shift to right
    • systemic HTN
    • CHF
    • atenuated SNS activity d/t tx w/ antihypertensive drugs
  • Renal- renal osteodystrophy
  • Heme
    • anemia (compensated)
    • uremic coagulopathies causing plt dysfunction
  • Endocrine
    • renin
    • EPO
    • Vit D-->PTH
  • CNS
    • encephalopathy
    • ANS dysfunction
    • neuropathies

18