Renal Flashcards
1
Q
Precursors of renal disease
A
DM
HTN
Family Hx
> 65 yo
2
Q
Kidneys receive ______% of CO.
A
20-25%
3
Q
Kidneys are autoregulated between MAP of _________ mmHg.
A
50-150 mmHg
4
Q
Kidneys: responsibilities/contributions
A
- water conservation
- electrolyte homeostasis
- acid/base balance
- neurohormonal functions
- waste filtration
5
Q
Normal GFR, variability, and estimated decline
A
90-140 ml/min/1.73m2
varies with gender, body weight, age
decreases 1% per year after the age of 20 (10% per decade after 30)
6
Q
best measure of renal function
A
creatinine clearance (most practical & inexpensive) direct measurement of clearance - creatinine and inulin
7
Q
What is creatinine clearance
A
most reliable measure for clinically assessing overall kidney function (GFR)
endogenous marker of renal filtration
produced at constant rate
freely filtered - not reabsorbed
normal: ~110-150 ml/min
8
Q
Pitfall of serum creatinine
A
slow reflect acute changes in renal function
ex. if acute injury occurs and GFR decreases from 100 ml/min to 10 ml/min, serum creatinine values may not increase for about a week
9
Q
What is serum creatinine?
A
creatinine is a product of muscle metabolism
serum creat directly r/t body muscle mass
can be used to reliably estimate GFR in NON critically ill pt
10
Q
Normal creatinine
A
men: .8 - 1.3 mg/dl
women: .6 - 1 mg/dl
11
Q
What is BUN?
A
directly r/t protein catabolism
sometimes used, but not ideal
12
Q
BUN: results are potentially misleading d/t?
A
dietary intake (high or low protein)
co existing disease (GI bleeding, febrile illness - catabolic illness)
intravascular fluid volume (dehydration)
13
Q
Despite extraneous variables - BUN > 50 mg/dL (normal 10-20 mg/dL) usually reflect ________ GFR/impaired renal function.
A
DECREASED GFR/impaired renal function
14
Q
Renal tubular dysfunction
A
established by demonstrating that the kidneys do not produce appropriately concentrated urine in the presence of a physiologic stimulus for the release of ADH
15
Q
Transient proteinuria
A
relatively common (5%-10% of adults)
associated with fever, CHF, seizures, pancreatitis, exercise
~up to 150 mg protein/day
16
Q
Persistent proteinuria
A
generally implies renal disease
~>750 mg protein/day
17
Q
Normal urine specific gravity and use
A
> 1.018 is adequate
measures urine concentrating ability
18
Q
What is fractional excretion of sodium?
A
measure of percentage of filtered sodium that is excreted in urine
19
Q
Usefulness of fractional excretion of Na?
A
useful to distinguish hypovolemia and renal injury
20
Q
FE na > 2% (or urine na concentration > 40 mEq/L) reflects?
A
decreased ability of the renal tubules to conserve sodium
-consistent with TUBULAR DYSFUNCTION
21
Q
FE NA < 1% (or urine na excretion < 20 mEq/L occurs when?
A
normally functioning tubules are conserving na (more of a reassuring sign)
could be more related to hypovolemia rather than intrarenal injury
22
Q
U/A: microhematuria can be indicative of?
A
- renal calculi causing damage
- cancerous growth
- glomerulonephritis
23
Q
Usefulness of a U/A
A
useful for renal tubular dysfunction and urinary tract disease
24
Q
What values can be obtained from a U/A
A
Detects presence of
- protein
- glucose
- acetoacetate
- blood
- leukocytes
urine pH & solute concentrations (specific gravity)
microscopy is used to identify cells, casts, microorganisms, crystals
25
U/A: WBC cast =
pyelonephritis
26
U/A: RBC cast =
acute glomerulonephritis
27
AKI is characterized by:
- deterioration of renal function - hours to days
- failure to excrete waste products
- failure to maintain fluid & electrolyte homeostasis
28
AKI diagnosis
- serum creatinine increase > .3 mg/dL within 48 hrs or >50% over 7 days
- acute drop in urine: <0.5mL/kg/hr for > 6 hrs
- severe injury: UO < 100 ml/day
- diagnostic biomarkers & U/A
29
AKI: s/s
usually absent in early stages
```
generalized malaise
fluid overload (dyspnea, edema, HTN)
nausea
confusion
hematuria
```
**Caution: encephalopathy, coma, seizures, death
30
AKI etiology
associated with other systemic disease/clinical conditions/drugs/interventional therapy
surgeries that are higher risk for AKI
- big CV surgeries
- vascular
31
AKI causes: prerenal
hypoperfusion
32
AKI causes: intrarenal
underlying renal causes, ischemia, nephrotoxins
33
AKI causes: postrenal
urinary collecting system obstruction
34
Azotemia
condition marked by abnormally high serum concentrations of nitrogen containing compounds such as BUN & creatinine and is HALLMARK OF AKI, regardless of cause
35
Pre renal azotemia: causes
pre existing CHF, liver dysfunction, septic shock
reduced RBF d/t decrease in PP (consider hypotension and vasodilation during anesthesia)
hypovolemia & blood loss
36
Early recognition and optimization of prerenal azotemia is important in order to prevent?
ischemia induced acute tubular necrosis & tubular cell injury
**rapidly reversible if underlying cause treated**
37
Why are the elderly susceptible to prerenal azotemia?
hypovolemia
| renovascular disease
38
Intrinsic azotemia is categorized according to site of injury i.e.....
- glomerulus
- renal tubules - ischemia or nephrotoxins (aminoglycosides, contrast dye)
- interstitium
- renal vasculature
39
What consideration must be given to a surgery that may involve a cross clamping or particular vascular surgeries?
"reperfusion injury" with influx of inflammatory cells/cytokines/oxygen free radicals
40
Postrenal azotemia: treatment option
removal of obstruction
percutaneous nephrostomy
recovery is inversely r/t duration of obstruction
41
(Patient) risk factors for perioperative renal failure
- pre existing renal dx
- advanced age
- CHF
- PVD
- DM
- emergency surgery
- major surgery (aortic aneurysm repair)
42
(Anesthesia related) Iatrogenic risk factors for perioperative renal failure
- inadequate fluid replacement
- hypotension
- delayed TX of sepsis
- nephrotoxic drugs
43
complications of AKI: neurologic
```
confusion
asterixis
somnolence
seizures
polyneuropathy r/t build up of protein and AA
```
44
complications of AKI: CV
```
systemic HTN -- LVH
CHF
pulm edema r/t Na and H2O retention
dysrhythmias, conduction blocks (metabolic derangement)
uremic pericarditis
autonomic neuropathy
Inc CO r/t to maintain O2 delivery (compensation for anemia)
accelerated CAD
```
45
complications of AKI: heme
anemia (hgb 6-8 -- dec erythropoietin and dec RBC production and dec in RBC lifespan)
coagulopathy
HCT 20-30% common d/t hemodilution & decreased erythropoietin
increased risk of bleeding d/t uremia induced platelet dysfunction
46
complications of AKI: metabolic
```
hyperkalemia and metabolic acidosis
hyperphosphatemia & hypocalcemia
hypoalbuminemia
hypermagnesemia
uricemia
```
47
complications of AKI: GI
anorexia
n/v
ileus (buildup of urea?)
gastroparesis -- think of periop aspiration risk
hypersecretion of gastric acid -- peptic ulceration and GI hemorrhage
48
complications of AKI: infection
respiratory & urinary tracts
sites where breaks in normal anatomic barriers have occurred
impaired immune response - WBC function impaired
49
Principles that guide anesthetic management
ONLY LIFE SAVING SURGERY WHEN POSSIBLE
1. maintain adequate systemic BP & CO
2. avoid further renal insults - hypovolemia, hypoxia, nephrotoxins
3. invasive hemodynamic monitoring - ABG & lytes
4. consider initiation of post - op dialysis if in stable condition
5. caution with diuretics
50
Chronic kidney disease defined
estimated GFR < 60 ml/min/1.73m2 for > or = 3 months
@GFR < 25 ml/min -- ESRD -- dialysis or rental tx
51
Clinical manifestations of CKD are related to:
- inability to excrete waste
- regulate fluid and electrolyte balance
- secrete hormones
52
Intrarenal hemodynamic changes likely responsible for progression of CKD
1. glomerular HTN
2. glomerular hyperfiltration & permeability changes
3. glomerulosclerosis
53
Goal and Management of CKD
reduce systemic & glomerular HTN:
- ACE inhibitors
- ARBs
- moderate protein restriction
- strict control of BG
- hyperlipidema likely - statin therapy advised
- smoking cessation
54
Patients with CKD remain relatively asymptomatic until RF is < ____% of normal.
10
55
CKD: 3 stages of adaptation
1. GFR decreases w/ rise in creatinine & urea
2. serum K increases (normal until GFR approaches 10% of normal)
3. sodium homeostasis and regulation of ECF (volume overload/volume depletion)
56
Complications of CKD: uremic syndrome, s/s
```
anorexia
nausea
vomiting
pruritis
anemia
fatigue
coagulopathy
--inability to excrete uremic toxins, secrete, regulate
```
BUN useful clinical indicator of severity & response to therapy
serum Cr poor clinical indicator
57
Complications of CKD: uremic syndrome, TX
dietary protein restriction + dialysis
58
complications of CKD: renal osteodystrophy
secondary hyperparathyroidism & dec vit d production -- impairs intestinal absorption of ca
hypocalcemia stimulates PTH secretion - leads to bone marrow resorption to restore serum Ca concentrations
as GFR decreases, decrease in phosphate clearance - increase in serum phosphate/decrease in Ca
59
renal osteodystrophy: tx
restrict dietary phospate, + oral ca and vit d supplements, antacids (to bind phosphorus in GI tract) (avoid mag & aluminum)
if medical therapies fail - subtotal parathyroidectomy
60
CKD: anemia
```
normochromic & normotcytic d/t dec erythropoietin
excess PTH (replace bone marrow with fibrous tissue)
```
TX: erythropoietin or darbepoietin; avoid blood transfusions; iron
61
complications of CKD: uremic bleeding
increased tendency to bleed & persistent anemia
BLEEDING TIME - best correlates with tendency to bleed!
hemorrhagic episodes - significant source of morbidity
62
uremic bleeding: TX
desmopressin - increases VIII - vWF complex (present within 2 - 4 hours & lasts 6 - 8 hours)
conjugated estrogens (onset approx 6 hours & lasts 14-21 days)
erythropoietin - enhances platelet aggregation & increases platelet counts
63
CKD complications: CV changes
systemic HTN: contributes to CHF, CAD, CVD
uncontrolled HTN: speeds progression of disease
pathogenesis: retention of Na and H2O + activation of RAAS = intravascular volume expansion
dyslipidemias
silent MI
uremic pericarditis
64
CV changes: treatment
dialysis - d/t hypervolemia & uremic pericarditis (keep in mind that dialysis will not fix HTN if the HTN is not related to hypervolemia)
increase dosage of antihypertensive drugs
tamponade - prompt drainage of effusion
65
Management of CKD: BP control
**remember that HTN is both a cause and a consequence of CKD - directly correlated with deterioration of renal function**
MULTIMODAL DRUG THERAPY
- ACE inhibitors & ARBs (1st line: especially in patients with proteinuria)
- diuretics
- Ca channel blockers
- aldosterone antagonists
66
Management of CKD: nutrition
modest protein restriction (0.6 g/kg daily)
dietary phosphorus restricted (600 - 800 mg/day) - can give phosphorus binders
vitamin D
Advanced disease - alkali salts
Na restriction (<1.5 - 2 g/day) (to prevent volume overload)
long term: euglycemic
67
Management of CKD: anemia
benefits vs risks of blood administration and management of anemia intraoperatively
erythropoietin (target hgb 10-11.5 g/dL, but really hard to achieve)
68
When is dialysis advised for CKD?
GFR 10 ml/min/1.73m2
effective dialysis significantly correlated with survival!
69
Management of Anesthesia: Pre op evaluation
- is renal function stable? - trends in serum creatinine concentration
- blood volume status before & after dialysis
- VS
- glucose management (parameters may be facility dependent)
- BP (ACE inhibitors and ARBs often withheld day of surgery)
- serum K should not exceed 5.5 mEq/L day of surgery (not a hard stop necessarily)
- anemia (consider surgery type, does the pt need optimization before sx)
- coagulopathy (consider surgery type, does the pt need optimization before sx)
- gastric aspiration prophylaxis (dose adjustment)
- dialysis within 24 hours preceding elective surgery
70
Management of Anesthesia: Induction considerations
safely accomplished with most IV induction drugs - concern is accumulation of active metabolites
ESRD - respond to induction agents as if they are hypovolemic/under-resuscitated
uremia & antihypertensives - result in hypotension
Exaggerated CNS effects - uremia induced changes in BBB
attenuated SNS activity impairs compensatory peripheral vasoconstriction (exaggerated hypotension)
--consider with position changes, drug induced myocardial depression, initiation of PPV/Peep, small decreases in blood volume
71
Can you induce a pt with CKD with succinylcholine?
Yes if K is <5.5
K release is not exaggerated in pts with CKD
But okay to use short onset like roc
72
Management of anesthesia: maintenance considerations with VA
balanced approach
VA: good control of HTN & decrease dose of muscle relaxant
VA: depression of CO potential hazard
sevo sometimes avoided (fluoride nephrotoxicity/compound A), but no evidence that patients with renal disease are at increased risk
73
Management of anesthesia: maintenance considerations with muscle relaxants
slow excretion of vec and roc
--prudent to decrease initial dose and base subsequent doses on TOF
cisatracurium independent of renal function!
74
Management of anesthesia: maintenance considerations with opioids
morphine & meperidine undergo metabolism to potentially neurotoxic compounds that rely on renal clearance (morphine 6 glucuronide & normeperidine)
hydromorphone also has active metabolite - doesn't mean that you can't use, just reduce dose and expect prolongs effect (especially in elderly or other comorbidities)
75
Management of anesthesia: maintenance considerations with reversal
renal excretion 50% of clearance of neostigmine, prolonged effect
- "recurarization" is unlikely because of potentially prolonged effect (so if the patient wakes up kind of weak, consider that its not recurarization, but another issue like metabolic derangement or CNS effect)
- sugammadex: not recommended in low creatinine clearance (<30 ml/min) or RRT
76
Management of anesthesia: maintenance considerations with fluid management & u/o
may benefit from preop hydration (500 ml) if...
- --do not require HD
- --w/o renal disease undergoing surgery with high incidence of post op RF
CAUTION - LR or K containing
U/O - 0.5 ml/kg/h
Diuretics in absence of intravascular fluid volume replacement is not advised
HD - dependent - narrow margin of safety
77
Management of anesthesia: maintenance considerations with POSITIONING
positioning - prone to bruising, sloughing/protect vulnerable nerves
fistulas must be protected
NO BP cuff on arm with fistula
If possible, maintain intra op access to arm with fistula
78
Management of anesthesia: maintenance considerations with monitoring
AVOID venipuncture in nondominant arm & upper part of dominant arm
AVOID radial and ulnar cannulation (same may be said of brachial and axillary)
- femoral cannulation - risk of infection
- DP and PT arteries - inconvenient/difficult to access
- Arterial pressure & ABG will not be accurate if on same extremity of AV fistula
- venous pressure monitoring - may be helpful, CVC may difficult
- TEE (for fluid management and overall CV function)
- Dialysis catheters may be used (THOUGH STRONGLY DISCOURAGED)
1) asceptic technique
2) aspirate heparin
3) heparin after d/c of use
79
Management of anesthesia: maintenance considerations with REGIONAL ANESTHESIA
May be considered
Concern for: bleeding, pre existing neuropathies
Considerations:
- sympathetic block T4-T10 may improve renal function by attenuating catecholamine induced renal vasoconstriction and suppressing surgical stress response
- BUT pts have platelet dysfunction, increased bleeding times, residual heparin from potential use of dialysis line
- brachial plexus blockade - assess for presence of uremic neuropathies!!
- presence of coexisting metabolic acidosis - may decrease seizure threshold in response to LAs
80
Management of anesthesia: POST OPERATIVE CONSIDERATIONS
skeletal muscle weakness: from residual NM blockade (unlikely) or....antibiotics, acidosis, electrolyte imbalance (its not that It couldn't be weakness from inappropriate dosing of NMB, but consider other possibilities as well)
caution w/ parenteral opioids - respiratory depression
avoid NSAIDs - may be more difficult to institute multimodal pain control in this population
continuous ECG monitoring (potential metabolic derangements)
supplemental O2 - don't tolerate hypoxia well
check electrolytes, BUN, creatinine, HCT, chest xray if concern for pulmonary edema
bleeding - uremic coagulopathy
81
Renal transplant: general anesthesia considerations
```
RA and GA successful - GA is more common
minimize decrease in CO - promote renal perfusion
high - normal BP is required
cisastracurium is often drug of choice
CVP is useful
Mannitol (osmotic diuretic)
albumin administration is helpful
release of vascular clamps - be aware of hypotension and cardiac arrest
```
82
Renal transplant: regional anesthesia considerations
- Advantages - No ETT & muscle relaxants
- Advantage negated if need to supplement RA with IV anesthetics
- Control of BP may be more difficult
- Controversial in presence of abnormal coagulation
83
Renal transplant: post op complications and associated TX
-acute immunologic rejection - almost IMMEDIATE
only TX: remove the kidney
-delayed signs of graft rejection - fever, local tenderness, deterioration of urine output
TREATMENT:
---high dose corticosteroids & antilymphocyte globulin
---monoclonal antibodies
---tacrolimus
---mycophenolate mofetil
---dialysis may be required
-opportunistic infections may occur
84
Renal transplant: additional anesthesia considerations
- often elderly
- co existing CV disease
- co existing DM
- consider side effects of immunosuppressant drugs - HTN, low seizure threshold, anemia, thrombocytopenia
- consider drugs that are excreted by kidneys
- avoid drugs that are nephrotoxic or dependent on renal clearance
- minimize decreases in RBF
85
AKI management: Treatment Aims
1. limit further renal injury
2. correct fluid/electrolyte/acid base derangements
3. reverse underlying causes of injury (hypovolemia, hypotension, low CO, sepsis)
4. Maintain MAP 65 or > (no evidence supporting outcomes with supraphysiologic values)
5. fluid resuscitation (goal directed therapy) & vasopressor therapy (norepi/vasopressin)
6. diuretics not advised
7. alkalinization of urine with sodium bicarb (rhabdo); reduces incidence of contrast induced nephropathy
8. dialysis - mainstay for severe AKI; volume overload, hyperkalemia, severe metabolic acidosis, symptomatic uremia, overdose with dialyzable drug - day of surgery/day before
