Flashcards in Renal Response to CPB- Exam 1 Deck (56)
What does the kidney do?
Regulates fluid composition, intravascular volume and excretion of metabolic byproducts
What is the incidence of renal failure (i.e. requiring dialysis)
Why is the incidence of renal failure decreasing?
Better patient preparation
Improved perfusion techniques
better management cardiac performance post op
If renal dysfunction occurs, what is the mortality rate?
>50% mortality rate
What is the function unit of the kidney?
How many nephrons in each kidney?
More than 1 million
What are the two main parts of the nephron?
What is the glomerulus?
Specialized capillary network
Allows filtration of fluid from plasma (no cellular components or proteins)
Glomerular membrane vs. normal capillaries
100x more permeable than normal capillaries
Collects filtered fluid
alters composition converting plasma filtrate to urine
What is the normal Glomerular Filtration Rate
100-200 mL/min in normal adult; preserved over a broad range of blood pressures
What percent of the volume filtered is reabsorbed (osmotic diffusion)?
How is urine output related to arterial blood pressure?
Linear increase in output with increase in arterial blood pressure
If you increase pressure 100 to 200 mmHg urine output increases by factor of what?
Decrease blood pressure below 50 mmHg causes what?
Urine output to stop
What allows long term control of blood pressure?
What determines how concentrated or dilute the urine is?
ARF Risk in patients with valve surgery vs. CABG
Patients undergoing valve surgery twice the risk compared to CABG patients
What is the most significant risk factor for acute renal failure?
Preoperative renal dysfunction
How can you determine preoperative renal dysfunction?
Elevated serum creatinine
Decreased creatinine clearance
What are some other risk factors for acute renal failure?
Impaired cardiac function
Complexity of procedure
ARF-D develops in what percent of patients?
1.2 to 13% of patients post CPB
Intraoperative Renal Risk Factors
Decreased blood volume
Prolonged CPB times with SIRS
High Hematocrit results in
Decrease in microcirculatory blood flow
Low hematocrit results in
Decrease in renal oxygen-carrying capacity
What lowers organ metabolic requirements?
What is hte most important target in hypothermia?
Stroke & Renal failure at 37C vs 34C?
Strokes and renal failure occured more frequently at 37C than 34C; difference not statistically significant
What is the difference in plasma renin activity or concentration of vasopressin?
No difference in plasma renin activity or concentration of vasopressin 37C vs 34C