acid base, blood gas interpretation Flashcards
Why look at blood gas levels
not a primary disease: reflects disease state, need to address underlying cause
early indicator of change-pulmonary function, metabolic balance
POC monitors more common now
pH
acidemia: <7.35
alkalemia: >7.45
PCO2
normal 35-45 mmHg
Partial pressure of O2
measures oxygen dissolved in plasma
normals vary with percentage of O2 inspired
PaO2
partial pressure of Oxygen in arteries
reflects ventilation/respiratory function
increased–>hyperoxia
decreased–>hypoxia/hypoxemia
hypoxia numbers
<80 mmHg moderate
<60 mmHg severe
PvO2
partial pressure of oxygen in veins
reflects tissue oxygen use
HCO3
bicarbonate level
normal values variable
carnivores: 16 to 24
herbivores: 24 to 30
Total CO2
95% is HCO3
5% is carbonic acid and dissolved CO2
normal is within 2 units of HCO3
Base Excess/base deficit
indicates the amount of HCO3 below or above normal
difference between normal buffer base and actual buffer base
What are the buffers in the body?
HCO3
Hemoglobin
phosphate
ammonium
serum proteins
SAT/SaO2
percent oxygen saturation
same as pulse oximeter reading
What is a normal SaO2 reading? Abnormal?
perfect: 100
normal: >95
serious hypoxemia: <90
severe hypoxemia: <70
lethal hypoxemia: <60
Will a patient be cyanotic if their SaO2 is at 90?
NO!
respiratory acidosis
increase in PCO2 (hypercapnia)
increases denominator causing a decrease in pH
rule outs for respiratory acidosis
respiratory depression from general anesthesia or CNS trauma/disease
primary respiratory compromise (pneumonia, pneumothorax, respiratory muscle weakness, restricted chest wall movement related to pain, upper airway obstruction)
malignant hyperthermia (increased CO2 production)
respiratory alkalosis
decreased PCO2 (hypocapnia)
decreases denominator to increase pH
rule outs for respiratory alkalosis
excessive manual or mechanical ventilation during general anesthesia
anxiety, directly stimulating respiratory centers
hypoxic stimulation in compromised patient
pain
metabolic acidosis
decreased HCO3
results in an increase in numerator to cause a decrease in pH
rule outs for metabolic alkalosis
shock, poor tissue perfusion resulting in anaerobic tissue metabolism
DKA, poisoning
diarrhea, renal tubular acidosis
metabolic alkalosis
increase in HCO3
increase in numerator leads to increase in pH
rule outs for metabolic alkalosis
primary gastric vomiting
potassium wasting diuretics, decreased fluid volume/dehydration
excessive endogenous sodium bicarbonate therapy
PaO2 normals
room air: 85 to 105 mmHg
33% O2: 150 mmHg
nasal O2: 200 mmHg
pure O2: 500 mmHg
BE normals
-4 to +4
