Acid-Base Disorders Flashcards
PCO2
partial plasma for CO2
what values are found in an ABG?
pH, HCO3, PCO2
when do you do the Allen test?
prior to drawing blood
why do we order an ABG?
assess respiratory (ventilation) and metabolic (renal) and electrolyte homeostasis
- manage ventilator
- pre-op assessment
- acute/critical illness assessment
why do we use radial instead of femoral artery?
it is a cleaner site
what does the allen test accomplish?
identifies if the ulnar artery will compensate for the radial artery if you block it while taking the sample
-ensures patency
what kind of test tube will you use to get a blood gas?
green top (heparin)
how quickly should your blood gas sample get to the lab?
ASAP or place on ice
one or two sticks?
you may use lidocaine to numb the area prior to drawing blood from the RA
positive Allen test means
ulnar artery is not patent and you cannot use that hand (7-10 seconds return)
contraindications for RA
no palpable pulse cellulitis or open infection AV fistula severe coagulopathy positive Allen test
what are the potential complications of drawing a blood gas?
arterial occlusion
penetration of other important structures nearby
what is the normal pH of arterial blood?
7.4
what is the normal pH of venous blood and interstitial fluid
7.35 (has extra CO2 released from nearby tissues that makes it more acidic)
what is the normal pH of intracellular fluid
estimated to be between 6.0-7.4
what is considered acidosis?
<7.35
what is considered alkalosis?
> 7.45
what are the lower and upper limits of pH that support life?
6.8<8.0 (more than a few hours at the high and low end will end life)
where is Hydrogen found most?
intracellular (which makes cells more acidic)
what is the alkaline substance in the body?
HCO3
what is the acidic substance in the body?
H+ and CO2 (H2CO3)
how does the body hold onto CO2?
breathing slower (found in alkaline patients)
where is bicarb manufactured?
kidney (slower than the lungs when it comes to compensation)
which organ responds first when pH becomes out of balance?
lungs
which organ controls retention and secretion of H+
kidney
what are the normal values for bicarb?
22-26 mEq/L
what is the alkalotic value of bicarb?
> 26
-metabolic alkalosis
what is the acidic value of bicarb?
<22
-metabolic acidosis
what are the normal values of PCO2?
35-45 mm/Hg
what is the alkalotic value of PCO2
<35
-respiratory alkalosis
what is the acidodic value of PCO2
> 45
-respiratory acidosis
metabolic acidosis
acidosis caused by a primary decrease in bicarb
-diarrhea (loss of HCO3 in feces)
metabolic alkalosis
caused by a primary increase in bicarb concentration
-drug overconsumption of HCO3 (overcorrecting in renal disease)
respiratory acidosis
caused by an increase in PCO2 from a respiratory disturbance
-hypoventilation (drug use)
respiratory alkalosis
caused by a decrease in PCOz from a respiratory disturbance
-hyperventilation (anxiety)
what is the time frame of the renal compensatory response?
several hours to 3-5 days
what is the time frame of the respiratory compensatory response?
minutes to max in several hours
SOB can also be called
hyperventilation (compensatory response of acidosis)
how much will ventilation increase in acidosis?
4-5 times normal
how much will ventilation slow down in alkalosis?
will slow but not as significantly
COPD who are former smokers are in a chronic state of
respiratory acidosis
what is metabolic compensation in acidosis?
reabsorb all filtered HCO3
produce new HCO3 which is added back into the extracellular fluid
secrete H+
-net effect is lowered extracellular H+
what is metabolic compensation in alkalosis
increase secretion of HCO3
most of the compensation is respiratory
what is a chem 7
BMP
what CO2 does the BMP come with?
not the same as a ABG
what is the formula to calculate anion gap?
Na - Cl+HCO3 (from blood gas)
what does elevated anion gap indicate?
metabolic acidosis
what is the Delta gap?
excess anion gap
AG-12 +HCO3
what does <23 delta gap indicate?
metabolic acidosis
what does >30 delta gap indicate?
metabolic alkalosis
