Topic 2: Renal Response to CPB Flashcards
Incidence of renal failure (i.e. requiring dialysis) %
(1%) - may be up to 13%
better patient preparation
improved perfusion techniques
better management cardiac performance postop
If renal dysfunction occurs during/after CPB: ?% mortality rate
> 50%
Nephron two main parts?
- glomerulus
specialized capillary network
allows filtration of fluid from plasma (no cellular components or proteins)
membrane is 100 x more permeable than normal capillaries - tubular system
collects filtered fluid
alters composition converting plasma filtrate to urine
Glomerular Filtration Rate (GFR) mL/min in normal adult?
100 to 200 mL/min in normal adult
Other risks for Acute Renal Failure include? (4)
impaired cardiac function
complexity of procedure
advanced age - greater than 63
genetics - inflammatory response
GFR - % vol filtered that is reabsorbed by diffusion?
what is actively reabsorbed?
99% of volume filtered is reabsorbed (osmotic
diffusion)
glucose and amino acids actively reabsorbed
what happens to U.O. when there is an increase pressure 100 to 200 mmHg ?
urine output — increases by factor of 7
Common Emboli
aortic atheroma
decrease blood pressure below 50 mmHg does what to U.O.?
output to stop
Patients undergoing valve surgery twice the risk compared to what patients?
to CABG patients
Preoperative renal dysfunction most significant risk factor?
Elevated serum creatinine
Decreased creatinine clearance
ARF-D develops in what % of patients post
CPB
1.2 to 13%
little conclusive evidence that modern cardiopulmonary bypass in-and-of itself causes renal dysfunction
Intraoperative Renal Risk Factors? (9)
Low flow Decreased blood volume IABP Prolonged CPB times with SIRS Inappropriate hemodilution Emboli Avoiding hypothermia Pulsatility
High hematocrit
Decrease in microcirculatory blood flow
Low hematocrit
Decrease in renal oxygen-carrying capacity
Warm heart surgery –Is renal dysfunction
increased?
Strokes/ RF?
plasma renin activity/vasopressin concentration?
Renal clearance?
◦strokes & renal failure occurred more frequently at 37oC than at 34oC–Difference not statistically significant (Arom et. al.)
◦no difference plasma renin activity or concentration of vasopressin (Lehot et. al)
◦transient increase in renal clearance and other indices of renal function while on bypass
–returned to normal after bypass
–Temperature has no lasting effect (Regragui et. al.)
Incidence of emboli and their associated
clinical problems greatly reduced when? (2)
stopped using bubble oxygenators
started using arterial / cardiotomy filter
Most patients who develop post operative
renal failure have what two things?
Suffer from preexisting renal disease
Have compromised renal perfusion secondary to low cardiac output during perioperative period
Have compromised renal perfusion secondary to low cardiac output during perioperative period caused by what two states?
- -low renal perfusion pressure while on bypass
- -low renal perfusion pressure off pump caused by renal vasoconstriction during low CO states
Goal of any pharmacological intervention is to prevent acute renal failure that requires dialysis – does it work???
No studies have conclusively shown that any
pharmacological agent was effective in
preventing acute renal failure requiring
dialysis or death during or after cardiac
surgery
decreased urine output is usually an indication of what?
renal hypoperfusion
Maintaining adequate perfusion pressure may be most important counter to renal hypoperfusion
Oliguria:
Urine output less than 0.25 to 0.33
ml/kg/hour
Assessment of Renal Function
Monitor U.O.
No other point-of-care assessment methods available
Studies have found no correlation between
intraoperative urine volume and postoperative
renal dysfunction (Alpert et al. and Knos et al)
Decreased urine output could be result of what?
kinked or obstructed catheter or stress -induced ADH secretion
