ABG Flashcards
pH is inversely proportional to ______.
H+
If pH is < 7.35 then it is _____.
acidic
If pH is >7.45 then it is _____.
alkalotic
Why does the blood pH matter?
pH and temperature affect biochemical reactions
An acidotic state can lead to what 3 negative effects?
- decreased efficacy of medications
- decrease in catecholamine response
- decrease in cardiac contractility
An alkalotic state can lead to what 3 negative effects?
- interferes with muscular contractions
- interferes with neurological functioning
- interferes with tissue oxygenation
What is the definition of a buffer?
Chemical that binds excessive H+ (or OH-) without significant pH shift
What is the most important plasma buffering system?
carbonic acid-bicarbonate system
A buffer pair consists of what 2 things?
a weak acid + conjugate base
What is the carbonic acid-bicarbonate equation?
H2O + CO2 H2CO3 H + HCO3
In the body what is the “hero” and “villain” of the acid-base balance?
- hero = bicarbonate
- villain = acid (H+)
What does the respiratory buffer response do?
CO2 is eliminated or retained via respiration
The more CO2 in the body the _______ the pH.
lower
The less CO2 in the body the _______ the pH.
higher
What organ is responsible for the renal buffer (metabolic) response?
kidneys
The renal metabolic response consists of what 2 things?
- kidneys excrete or retain bicarbonate
- kidneys excrete or retain H+
The more HCO3-, the _____ the pH.
higher
The less HCO3-, the _____ the pH.
lower
How does the lungs compensate for an increase in carbonic acid (pH lowering)?
Eliminates more CO2 by increasing respiration
How does the lungs compensate for a decrease in carbonic acid (pH increasing)?
Retains more CO2 by decreasing respiration
Which of the compensation methods (respiratory/metabolic) is quick and begins in minutes?
respiratory
How does the kidneys compensate for an increase in carbonic acid (pH lowering)?
Retains more HCO3
How does the kidneys compensate for a decrease in carbonic acid (pH increasing)?
Excretes more HCO3
What equation describes the derivation of pH as a measure of acidity?
Henderson-Hasselbach Equation
What is the formal for the Henderson-Hasselbach Equation?
pH = 6.1 + log [ HCO3/ (pCO2 x 0.03) ]
Any process that changes ______ is a metabolic process.
HCO3-
Any process that changes ______ is a respiratory process.
pCO2
pCO2 can only leave in one way, which is?
the lungs
pCO2 is produced where?
everywhere
HCO3 is produced where?
in the kidney
T/F: You are not able to overcompensate.
True
What is the ABG wishbone composed of?(from left to right)
pH/pCO2/pO2/HCO3/SaO2
When reading the ABG results it is important to note what about the patient?
% of O2 they are receiving if any
What are 3 indications for ABG draw?
- Assess status of oxygenation and ventilation
- evaluate acid-base status
- monitor effectiveness of therapy
T/F: ABG is significantly more painful than phlebotomy.
True
What are 4 sites in which ABG specimen can be collected? (* the preferred location)
- Radial artery puncture*
- Brachial artery puncture
- Femoral artery puncture
- Arterial line draw
Before obtaining an ABG what 3 exams should be done on the puncture site?
- skin inspection
- pulse exam
- allen’s test
Which artery is responsible for the dominant circulation of the hand?
ulnar artery
Ideally you want the whole hand to perfuse within how many seconds on an Allen test?
15 seconds
What are 4 contraindications for ABG?
- Abnormal Allen’s test
- Local skin infection/lymphedema
- Arterial disease
- Acral hypoperfusion
What 2 things does the ABG kit consist of?
- 22-25g needle
- Heparinized syringe system
T/F: The ABG syringe does not need a negative vacuum pressure.
True
Once you collect the ABG what is the first thing you should do?
Mix the arterial sample with heparin anticoagulant by rolling in your hands.
Once the ABG specimen is obtained ideally you want to run the test how quickly?
right away
Patients with dark skin it can be challenging to see change in perfusion. What test is better?
laser doppler flowmetry (LDF)
The heparinized syringe needle consists of how much heparin?
1-2 ml
