Acid/Base balance by Kidneys Flashcards
Buffering equation
HCO3- + H+ → H2CO3 <ca>⇒ CO2 + H2O</ca>
Normal values:
pH
CO2
HCO3
pH: 7.4 (7.35-7.45)
CO2: 40 mmhg (35-45)
HCO3: 24 mM (20-28)
acute respiratory acidosis
Increased CO2
decreased pH
increased HCO3-
normal BE
chronic respiratory acidosis
increased CO2
close to normal pH
very increased HCO3-
> +2 BE
acute metabolic acidosis
decreased CO2
decreased HCO3- or increased H+
decreased pH
negative
Chronic metabolic acidosis
decreased CO2
decreased HCO3-
about normal pH
negative
Acute respiratory alkalosis
decreased CO2
decreased HCO3-
increased pH
normal BE
chronic respiratory alkalosis
decreased CO2
very decreased HCO3-
about normal pH
negative
acute metabolic alkalosis
increased CO2
increased HCO3-
increased pH
positive >+2 BE
chronic metabolic alkalosis
increased CO2
increased HCO3-
about normal pH
positive >+2 BE
anion gap
Na+ - (Cl- + HCO3-)
high anion gap = addition of acid
normal anion gap = loss of base
Where does bicarb reabsorption take place?
proximal tubule
thick ascending limb of Henle
Collecting duct
Under normal conditions, do you excrete bicarb in urine?
No
How many millimoles of bicarb in our ultrafiltrate?
How much do we reabsorb?
24 millimoles
100%
Generally, diuretics work by
altering osmolality of the urine filtrate, preventing the reabsorption of the water, resulting in an increase of urine volume.
* usually lose Na, then water follows
ACE inhibitors
Prevents Angiotensin from becoming Angiotensin II
How do loop diuretics work?
block the Na-K-2Cl pumps in the ascending loop of Henle
How do Thiazide-like diuretics work?
block Na reabsorption
Which diuretics are potassium sparing?
aldosterone blocking agents
At what age does kidney function begin to decline?
Kidneys begin to diminish in size and function in 50’s and dignificantly by 65
What are some renal considerations for the elderly?
- loss of nephrons
- diminished renal blood flow
- decrease in the GFR
- decreased ability to conserve salt and water
- cannot concentrate urine
- more susceptible to fluid and electrolyte imbalances and renal damage
What studies are helpful in evaluating kidney function?
- Urinalysis
- serum creatinine
- blood urea nitrogen levels
- high protein diet causes more urea and high BUN
- tests of GFR
Types of urinalysis
- single sample- most common
- 24 hour- used to evaluate substances that are excreted in varying concentrations throughout the day
- culture and sensitivity- determine presence of microorganisms and which drugs they are sensitive to.
What are abnormal substances to find in urine?
- protein (small amt is accepted as normal)
- glucose
- excess epithelial cells, erythrocytes, leukocytes, and bacteria
- cyrstals and stones
- casts
- WBC casts reflect infection
- RBC casts indicate inflammation of glomerulus
- epithelial casts indicate sloughing of tubular cells (acute tubular necrosis)
Where does creatinine come from and what is normal value?
- creatine is spontaneously converted to creatinine and excreted exclusively by the kidney
- normal level: 0.7 to 1.5 mg/dl
What affects the levels of creatinine?
What does an elevated level indicate?
- rate of creatinine produced from muscle, which is relative constant
- rate of creatinine excreted by the kidney, which is determined primarily by GFR
- Elevated levels indicat a decrease in renal function or an increase in muscle
BUN test
normal
elevated level indicates?
- Urea is the end product of protein metabolism excreted primarily by the kidney
- normal level: 10-20 mg/dl
- elevated level indicates:
- decrease in renal function and fluid volume.
- increase in catabolism and dietary protein intake
What is the most acurate way to measure GFR?
Inulin
