Acid Base Balance Flashcards
FPC
pH Normal Range
7.35-7.45
CO2 Normal range
35-45 mmHg
HCO3 Normal range
22-26 mEq/L
SaO2 Normal range (SPO2)
> 95%
PaO2 Normal range (pO2 or Partial Pressure of Oxygen)
80-100 mmHg
Base (Deficit/Excess)
(-2) to (2+)
Buffer system: Reacts in seconds
Bicarb (HCO3)/ Carbonic Acid (H2C03)
Buffer system: Reacts in minutes
Lungs blow off/hold CO2
Buffer system: React in hours to days
Kidneys resorb/excrete bicarb (HCO3)
How does CO2 exist in the blood?
as a soluble gas
What is a normal byproduct of metabolism?
CO2
How is CO2 measured in solute?
Measured in partial pressure PaCO2
What is the relationship between CO2 and respirations?
CO2 regulation is a function of MINUTE Volume and tidal volume (VT) X respiratory rate (F). If the PaCO2 is high respirations will increase; if PaCO2 is low, respiratory drive decreases; Apnea causes respiratory acidosis and eventually metabolic; Hyperventilation causes respiratory alkalosis and eventually metabolic alkolosis.
Low HCO3
Low pH, >22 too little bicarb, too much H+
High HCO3
High pH, <26 too much bicarb, too little H+
What does a base deficit of >-4 indicate?
for the potential need for blood transfusion
What does a base deficit of >-19 indicate?
Correlates with a poor outcome (death likely)
Replacement formula of bicarb needed
0.1 x (-BE) x patient weight in kg x
i.e. pt weighs 110 kg and has a BE of -6.
Formula 0.1 x (-6) x 110 = 66 meq of bicarb needed
PaO2 of 60 is roughly equal to what SaO2?
90%
PaO2 and SaO2 correlation
40 mmhg / 50 mmHg / 60 mmHg = 70%/ 80%/ 90% SaO2
What does 2,3 DPG do to the oxygen carrying abilities of Hgb?
2,3-DPG pries 02 off of hemoglobin
What is the affinity for oxygen in a right shift?
decreased
What is the affinity for oxygen in a left shift?
increased
What happens in a left shift of the oxyhemoglobin dissociation curve?
Increased affinity of Oxygen to Hgb decreased H+ decreased temp decreased 2,3-DPG low PCO2
What happens in a right shift of the oxyhemoglobin dissociation curve?
Decreased affinity of Oxygen to Hgb increased H+ increased temp increased 2,3-DPG High PCO2
How does a change in CO2 of 10 mmHg affect pH?
pH changes 0.8 in opposite direction
How does a change in CO2 of 10mmHg affect K+?
K+ changes 0.5 in the same direction
How does a change in 0.1 of pH affect K+?
K+ changes 0.6 in the opposite direction
How does a change in pH of 0.15 affect HCO3?
HCO3 changes 10 in the same
Critical ABG’s for intubation
pH <7.2
pCO2 > 55
pO2 < 60
Normal potassium range
3.5 - 5.0 mEq/L
