acid base Flashcards
what is normal arterial pH
7.35-7.45
what is normal CO2
35-45
what is normal HCO3
22-26
where is the collection of an ABG done?
radial artery
may use femoral, brachial, or dorsalis pedis in emergencies
what would a nurse do if they cannot find the radial artery
use a Doppler
a respiratory therapy is usually the most experienced
watch over the medical resident
when would the radial artery be hard to find?
edematous, elderly, dehydrated
can a critical care nurse take an ABG?
yes, a critical care nurse can take the blood from the Alaris pump central line insert
what information is obtained from an ABG?
acid base status
oxygenation (dissolved O2, saturation of hemoglobin)
What are the indications for an ABG?
Assess the ventilatory status
Oxygenation and acid base status
To reassess the response to an intervention
what are the contraindication for an ABG
bleeding disorder
AV fistula
severe peripheral vascular disease, absence of an arterial pulse
infection over site
what are the differences between and ABG and pulse oximetry
Pulse oximetry uses light absorption at two wavelengths to determine hemoglobin saturation
Pulse oximetry is non-invasive and provides immediate and continuous data
Pulse oximetry does not assess ventilation (pCO2) or acid base status
Pulse oximetry becomes unreliable when saturations fall below 70-80%
Technical sources of error (ambient or fluorescent light, hypoperfusion, nail polish, skin pigmentation)
Pulse oximetry cannot interpret methemoglobin or carboxyhemoglobin
what does heparin do for an ABG
Eliminates dilution problem
Mixing becomes more important
May alter sodium or potassium levels
how would an ABG be performed
Withdraw the needle and hold pressure on the site
Protect needle
Remove any air bubbles
Make sure blood is in contact with heparin
Gently mix the specimen by rolling it between your palms
Place the specimen on ice and transport to lab immediately
what are the collection problems associated with an ABG
air bubbles
specimen handling and transport
collection problems air bubbles
Gas equilibration between ambient air (pO2 ~ 150, pCO2 ~ 0) and arterial blood
pO2 will begin to rise, pCO2 will fall
Effect is a function of duration of exposure and surface area of air bubble
collection problems: specimen handling and transport
- Minimize time from sample acquisition to analysis (within 30 minutes)
- After specimen is collected and air bubble is removed, gently mix and invert syringe
- Placing the ABG on ice may help minimize changes, depending on the type of syringe, pO2 and WBC count
- Because the WBCs are metabolically active, they will consume oxygen
-PaO2 will decrease, PaCO2 will increase - Plastic syringes are gas permeable
- Because the WBCs are metabolically active, they will consume oxygen
what is pH
an indicator of hydrogen ion H+ concentration
what is normal venous pH
7.32-7.42
what is the pH of water
7.0
neutral
what is the pH range compatible with life
6.8-7.8
Outside of range can denaturize proteins
how is pH regulated
Homeostatic mechanisms: Chemical buffer systems Lungs Kidneys
Net acid production: Net acid elimination
what body systems regulate pH
lungs and kidneys
which body system works faster to regulate pH
Lungs work a lot faster
Peak compensation for lungs is 1-24 hours
Peak compensation for kidneys is 12 hours-5 days
what are the three major chemical buffer systems
Bicarbonate
Phosphate
Protein buffer systems
