Renal Flashcards
What are the major functions of the kidneys?
- Control fluid and ion balance
- volume, osmolarity, pH, mineral composition
- remove wastes from circulation
- gluconeogenesis
- endocrine function/hormone
- fluid balance- Renin, prostaglandins, kinins
- RBC production- EPO
- bone- 1, 25 dihydroxyvitamin D3
Autoregulation
What do our anesthetic techniques cause?
- Autoregulation of RBF and GFR maintained with MAP between 80-180
- All agents and most techniques cause decreased:
- GFR
- UOP
- RBF
- electrolyte excretions
- All major kidney functions affected, usually reversible after procedure
What is considered oliguria?
What are the causes?
- UOP < 0.5 ml/kg/hr or < 30 ml/hr
- Prerenal
- hypovolemia
- decreased CO
- renal
- renal ischemia
- nephrotoxic drugs
- release of hemoglobin or myoblobin (in rhabdo, will clog glomeruli)
- Post renal
- bilateral ureteral obstruction
- extravasation due to bladder rupture
What affects do anesthetics have on normal renal function (hormone release)?
-
ADH release due to surgical stimulation
- will decrease UOP
- aldosterone release- from baroreceptor response to volume depletion
- Autoregulation may be affected under GA
Hypotension caused by agents under GA causeses blood to _____. What happens next?
- shunt away from the kidney
- any decrease in RBF causes release of Renin which leads to vasoconstriction and SNS stimulation further decreases RBF
Prostaglandins:
What do they do?
When are they produced?
What drug does affects prostaglandins?
- prostaglandins have protective effect agains renal ischemia (local vasodilators)
- oppose the actions of angiotensin II, SNS, ADH to balance the decrease in RBF and increase UOP
- Production of prostaglandins is promoted in renal ischemia, renal hypotension, and physiologic stress
- Ketoralac should be avoided in pts a risk for medullary ischemia because it inhibits the productions of prostaglandins, increasing risk of ischemic damage
Does Low dose dopamine decrease ARF?
dose
NO. It does not decrease incidence of ARF, dialysis, or mortality, but it does have inotropic effects with diuretic activity.
Does not protect the kidney b/c it does not increase BF to the deep loops of henle where the metabolic demand is.
1-2 mcg/kg/min
What does spinal and epidural anesthesia do to Renal function?
- T4-T10 sympathectomy will decrease release of catecholamines, renin, and vasopressin
- Key to maintenance of renal blood flow and GFR is you have to maintain renal perfusion pressure
- fluid boluses
What VA do we avoid with renal patients? Why are these agents more concerning?
- Methoxy > Enflurane > Maybe Sevo
- these agents create free fluoride ions during metabolism that can cause tubular injury and the loss of concentrating ability
Which VA are very low risk to the kidney?
- Isoflurane and Desflurane
What is the most up to date rule regarding Sevo flows?
- FDA recommends flows of 2L
- if running 1-2 L, should not use for more than 2 MAC hours
- no clinical evidence of injury from compound A
How do PIP and PEEP affect the kidney?
how can these changes be overcome?
- The higher the PIP and PEEP, the greater the decrease in RBF, GFR, and Urine flow rate
- Hydration will overcome these changes by improving CV function
What response would you expect the body to have to a decreased preload, CO, and arterial hydrostatic pressure
- SNS activation
- RAAS activation
- promotion of vasopressin release
What are the clinical features of Chronic Renal failure?
- long term dialysis is required when Cr > 3 mg/dl (GFR < 30 ml/min)
- Generalized edema- may need to administer higher doses of water soluble drugs
- high concentrations of non-protein nitrogens
- creatinine, urea, uric acid
- High concentration of phenols, sulfates, phos, and potassium
- Osteomalacia- vit D must be converted by liver and kidneys before it is able to promote Ca absorption
- Pruritis
Why are renal pts anemic?
What Hgb is normal for a renal pt?
what are the Hgb/Hct goals for these pts
- Anemic because of decreased production of EPO
- EPO therapy is helpful in improving this anemia, however it causes HTN or makes current HTN worse
- Hgb 5-8 g/dl
- Goal:
- Hct 36-40%
- Hgb> 12 g/dl in females and >13 g/dl in males
What changes would you expect to see in the coagulopathies of a pt with renal disease?
What is the cause?
What does this mean?
- Increased bleeding time DESPITE normal PT, PTT, and platelet count
- b/c platelets are not normal
- usually from defective von-willebrand factor
- can be treated with DDAVT or Cryo
- Pts at risk for GI bleed, hemorrhagic pericarditis, and subdural hematoma
What does hyperkalemia cause?
- peaked T waves
- prolonged PR interval and QRS
- heart block
- v-fib
what causes hypocalcemia?
What causes metabolic acidosis?
What does hypermagnesemia cause?
- hypocalcemia due to hyperphosphatemia
- hypermagnesemia can lead to coma and CNS depression
- metabolic acidosis due to inability to excrete H ions
What causes systemic HTN in renal pts?
What is the BP goal?
How can this be achieved?
- intravascular volume expansion and activiation of the RAAS
- at risk for CHF, MI, and stroke
- BP goal <130/85
- ACE inhibitors or angiotensin receptor blockers
- Hold the morning of surgery
What are some nervous system abnormalities seen in renal pts?
- Uremic neuropathy- maybe dont do regional
- Uremic encephalopathy
- anywhere from mild irritability to coma
- usually reversed when dialysed
- mixed motor/sensory polyneuropathy
- ascending neuropathy that stops at knee or elbow
- median nerve and common peroneal nerves most often seen
- End stage may see parathesias in feet and lower extremety weakness
How do infections affect pts with renal disease?
How do infections usually originate?
what can we do about it?
- Of pts on HD, 25% die per year
- 1/2 of those deats are caused by infections
- 1/2 are caused by CV instability
- usually originates as a pulmonary infection
- associated with uremia
- ASEPTIC TECHNIQUE!!
What is ARF?
- sudden deterioration in renal function
- increased serum Cr > 0.5 mg/dl means a 50% decrease in Cr clearance
- pt may be oliguric (<400 ml/day) or nonoliguric (>400 ml/day)
What are the three categories of ARF?
- Pre-renal: decreased blood supply to kidneys from CHF, low CO/BP, or low blood volume
- seen in shock syndromes
- Intra-renal: abnormality within the kidney
- Post-renal: obstruction of urinary collecting system by renal calculi, etc
What pts are at high risk for ARF following anesthesia?
- Pre-op renal insufficiency
- pre-op CHF or atherosclerosis
- cardiac events peri-op (inadequate BP/CO)
- Sepsis and/or emergency surgery, trauma (MODS)
- elderly
- ESLD
- hypovolemia
- nephrotoxic exposure
- CPB
- aortic clamping
- liver or kidney transplant procedures
- nephrectomy procedures
What are the physiologic effects of ARF?
- Retention of water and waste products, electrolytes, in the blood and CSF
- HTN, CHF, Pulm edema
- RBCs diluted- Hct 20-30%
- GI bleeds- anorexia, nausea, and ileus
- hyperkalemia- can be fatal
- metabolic acidosis
- neurological changes from confusion to coma
- uremia induces immune suppression–>infection
Do we want to take a pt in ARF to the OR?
NO. Only if it is an emergency! These pts are very sick!
Keep MAP > 65
What are the goals for a dialysis pt?
- Avoid infection!
- preserve vascular access
- avoid IV in non-dominant arm and upper portion of dominant arm
- Remember pre-op dialysis clears many medications
- may need to redose
What kinds of medications are easily cleared in Dialysis?
- Low weight
- <90% PB
- water soluble
