Flashcards in Renal Response to CPB- Exam 1 Deck (56)
Some studies say it is better
others show no idfference
no studies show it is harmful
Most cases not creating "true" pulse pressure
Adds significant degree of complexity
No significant advantage
Incidence of emboli and their associated clinical problems greatly reduced when...
Stopped using bubble oxygenators
Started using arterial/cardiotomy filter
Most patients who develop post op renal failure:
suffer form pre-existing renal disease
Have compromised renal perfusion secondary to low CO during perioperative period
What on bypass can cause post op renal failure ?
Low renal perfusion pressure while on bypass
Low renal perfusion pressure off pump caused by renal vasoconstriction during low cardiac output states
What is the goal of any pharmacological intervention?
Prevent acute renal failure that requires dialysis
Calcium Channel Antagonists
What is an indication of renal hypoperfusion?
Monitor urine output with decreased output
U/O less than 0.25-0.33 ml/kg/hr
What is the relationship between intraoperative urine volume and post op renal dysfunction?
Decreased urine output could be result of what?
Kinked or obstructed catheter or stress-induced ADH
What is the most important counter to renal hypoperfusion?
Maintaining adequate perfusion
MOA: Stimulate dopamine receptors in renal vasculature; vasodilation; inhibits sodium reabsorption in proximal tubule
Dose: 0.5 ug/kg/min
Problems: Post-Op A-fib, impairment of ventilatory drive in response to hypoxemia and hypercarbia, supress circulating levels of anterior pituitary-dependent hormones; renal effect is unpredictable
Current Research: No benefit, unpredictable
Type: Synthetic benzazepine derivation
MOA: Binds selectively to DA1 receptors, causes systemic and renal vasodilation; theoretically augments RBF during CPB
Dose: 0.1 ug/kg/min
Problems: Should not be used prophylactically, further research necessary
Current ResearcH: Improvement in creatinine clearance, less renal-replacement therapy, decreased time of mechanical ventilation and ICU stay; currently no difference in ARF-D incidence
Type: Synthetic sympathomimetic amine
MOA: stimulates B2 and dopaminergic DA1 receptors, exerting both systemic and renovasodilatory effect
Dose: 0.5 ug/kg/kim- 2.0 ug/kg/min
Problems: Only modest improvements in creatinine clearance; role is still speculative
Current Research: Potentially inhibits SIRS due to decrease in proinflammatory cytokines by B2 and DA1 receptor stimulation
Furosemide (Loop Diuretics)
MOA: inhibits active transcellular transport of Cl and Na, produce natriuresis
Problems: Higher rate of renal impairment compared to LDD; worsens outcome when treating oliguria
Current Research: reducing active transport decreases cellular oxygen demand and decreases damange to mTAL. May increase clearance of necrotic cellular debris diminishing tubular obstruction; improvement in urine flow rates but no change in overall dialysis-free survival
Mannitol (Osmotic Diuretic)
MOA: "Flushing" effect of necrotic tubular debris, oxygen-free radical scavenging and improevement in meduallary blood flow reducing endothelial edema
Dose: 0.25 - 1.0 g/kg before aortic XC
Problems: Unproven as a renal protectant
Current Studies: No greater renal protection
MOA: Dilates afferent arterioles, increases Pgc and GFR. Inibits the tubular reabsorption of chloride and sodium, redistributes medullary BF and bloods endothelin in renal vasculature
Problems: Worse in patients with nonoliguric ARF, due to hypotension from ANP; no role in perioperative renal dysfunction
Research: Increase in dialysis-free survival only in patients with oliguric ARF.
Calcium Channel Antagonists
Research: improved GFR, enhance vasodilating protraglandin E2, supress the vasoconstricting prostaglandin Thromboxane B2, modulate vascular sythesis of endothelin, improvements in postop renal function measured by creatinine clearance
Type: dihydropyridine calcium channel antagonist
MOA: preferential increase in regional blood flow to ischemic regions of hte kidneys
Research: in patients with baseline serum creatinine levels less than 1.3 mg% undergoing elective CABG with CPB. IV infusion of felodipine administered during the second half of hypothermic CPB nad discontinued before rewarming. GFR and active tubular transport improved
Reductions in urinary microenzyme excretion
Problems: Little protection against ARF
MOA: lowers blood pressure while possibly preserving renal function
Problem: Induced renal injury as evidenced by increase in urinary N-acetylglucosaminidase levels
Research: Suggests no benefit, potential harm due to the effects of hyperglycemia
Normally discontinued 7-10 days before open-heart surgery to minimize perioperative hemorrhage due to platelet dysfunction.
MOA: inhibition of thromboxane, a potent renovasoconstrictor
Dose: 100 mg until day of surgery
Potentially beneficial for preserving post op renal function.
Problems: increase in postop bleeding
Research: Significantly less postop renal insufficiency in aspirin-treated group