ABG Flashcards
purpose of ABG’s
to assess acid-base status and determine adequacy of oxygenation and ventilation
ABG: pH
balance of H+
7.35-7.45
< = acidic
> = basic
PaCO2
35-45 mmHg
respiratory parameter
carbonic acid dissolves into CO2 and H2O
partial pressure of CO2 in ARTERY
HCO3
22-26 mEq/L
metabolic parameter
*measured HCO3 is reported as CO2 on a chemistry panel (serum CO2)
venous blood gas:
pH
PvCO2
pH: 7.31-7.41
PvCO2: 41-51 (partial pressure of CO2 in VEIN)
basic metabolic panel (BMP):
serum CO2 =
HCO3 level
22-26 mmol/L
primary EVENT
PROBLEM that initiates imbalance
*hypoventilation
*hyperventilation
*V/D
primary DISORDER
what RESULTS from the primary event
*respiratory acidosis (hypovent)
*metabolic acidosis (hypervent)
+ “” alkalosis
compensation mechanisms
physiologic processes that adjust the pH back to normal range
*if lungs are problem - kidneys compensate
*if kidneys are problem - lungs compensate
metabolic cause
HCO3 (bicarbonate) level changes d/t METABOLIC alterations (KIDNEY)
respiratory cause
H2CO3 (carbonic acid) level changes d/t RESPIRATORY alterations (LUNGS)
4 types of imbalances are a result of
changes in ventilation
increase/decrease in CO2
changes in H+ or bicarbonate ions
ROME
respiratory - opposite
metabolic - equal
metabolic acidosis: primary/compensation/pH
decrease HCO3
decrease CO2
decrease pH
metabolic alkalosis: primary/compensation/pH
increase HCO3
increase CO2
increase pH
respiratory acidosis: primary/compensation/pH
increase CO2
increase HCO3
decrease pH
respiratory alkalosis: primary/compensation/pH
decrease CO2
decrease HCO3
increase pH
metabolic alkalosis
too much HCO3 OR not enough carbonic acid
pH > 7.45
CO2 35-45
HCO3 > 26
causes of metabolic alkalosis
-excess baking soda/sodium bicarb
-prolonged vomiting
-NG tube (GI suctioning)
-diuretics (esp. loop)
clinical manifestation of metabolic alkalosis
CNS over excitability –> leads to fatigue
confusion
tremors
muscle cramps
paresthesias
coma
N/V/D
respiratory depression - compensatory hypoventilation
dysrhythmias (tachycardia)
hypokalemia
respiratory alkalosis
H2CO3 (carbonic acid) DEFICIT in ECF
pH > 7.45
CO2 < 35
HCO3 22-26
cause of respiratory alkalosis
hyperventilation (CO2 blown off)
increased metabolic demands (d/t fever, sepsis)
meds
acute anxiety
hypoxia
PE or lung disease
CNS lesions
ventilator settings
clinical manifestations of respiratory alkalosis
CNS over excitability
tachypnea + hyperventilation (deep and rapid)
light headedness
confusion, blurred vision
paresthesia
hyperactive reflexes
seizures
coma
tachycardia
hypokalemia
respiratory acidosis
excess carbonic acid/ H2CO3
*hypoventilation – retained CO2
pH < 7.35
CO2 > 45
HCO3 22-26
acute respiratory acidosis
HCO3 WNL
no time for kidneys to compensate
*resp arrest
chronic - COPD/oversedation
causes of respiratory acidosis
cardiopulmonary arrest
head injury
narcotics/sedatives
anesthesia
pulmonary disorders (COPD exacerbation, acute asthma, PNA, resp failure)
pain
abd distention
airway obstruction
chest wall deformities
neuromuscular problems
clinical manifestations of respiratory acidosis
CNS depressing…
HYPOventilation
dyspnea
respiratory distress
H/A
restlessness
confusion
tachycardia
arrhythmias
decreased LOC, stupor, coma
metabolic acidosis
HCO3 DEFICIT in ECF
excess acids are added or bicarb is lost
pH < 7.35
CO2 35-45
HCO3 < 22
IF lungs compensating, respirations increased and CO2 decreased
clinical manifestation of metabolic acidosis
CNS…
lethargic, drowsy
confusion
tremors, muscle cramps
parasthesias
H/A
hypotension
hyperkalemia
warm, flushed skin (vasodilation)
*deep breathing (KUSSMAUL RESPIRATIONS [DKA])
*fruity odor breath [DKA]
causes of metabolic acidosis
renal failure
fistulas
T1DM - DKA
lactic acidosis
prolonged diarrhea
starvation (body using fat for energy resulting in ketosis)
med overdose (ASA)
shock and cardiac arrest (begin to produce lactic acid from lack of oxygen in tissues)
respiratory acidosis/alkalosis: compensation
KIDNEYS compensates by:
-conserving HCO3
-excreting HCO3
takes kidneys HOURS TO DAYS to compensate
metabolic acidosis/alkalosis: compensation
LUNGS compensate by:
-conserving CO2
-excreting CO2
(the kidneys also attempts to correct imbalance by retaining/excreting HCO3)
takes lungs MINUTES TO HOURS to compensate