ABGs Flashcards
purpose of ABGs
to assess acid-base status and to determine adequacy of oxygenation and ventilation
pH normal range and purpose
–7.35-7.45
–balance of H+
PaCO2 normal range and purpose
–35-45
–respiratory parameter
–carbonic acid dissolves into CO2 and H2O
HCO3 normal range and purpose
–22-26
–metabolic parameter
–measured HCO3 is reported as CO2 on a chem panel
PaCO2
partial pressure of CO2 in artery
components of ABG
–pH (7.35-7.45)
–PaCO2
–HCO3
components of VBG
–pH (7.31-7.41)
–PvCO2 (41-51)
–HCO3
PvCO2
partial pressure of CO2 in vein
BMP
serum CO2 = HCO3 level (22-26)
primary event
the problem that initiates the acid-base imbalance (hypoventilation, hyperventilation, vomiting, diarrhea, etc.)
primary disorder
what results from the primary event (respiratory acidosis, metabolic alkalosis, etc.)
compensation mechanisms
physiologic processes that adjust the pH back to the normal range
–lungs are problem = kidneys compensate
–kidneys are problems = lungs compensate
metabolic cause of imbalance
–HCO3 level changes secondary to metabolic alterations
–the PROBLEM is metabolic in nature
respiratory cause of imbalance
–H2CO3 level changes secondary to respiratory alterations
–the PROBLEM is respiratory in nature
respiratory acidosis and alkalosis
–increase or decrease in CO2
–changes in ventilation
metabolic acidosis and alkalosis
changes in H+ or bicarb ions
acid base pneumonic
R(espiratory)
O(pposite)
M(etabolic)
E(qual)
‘Respiratory Opposite’
–pH high, CO2 low (alkalosis)
–pH low, CO2 high (acidosis)
‘Metabolic Equal’
–pH high, HCO3 high (alkalosis)
–pH low, HCO3 low (acidotic)
metabolic alkalosis
too much bicarb or not enough carbonic acid
ABGs for metabolic alkalosis
pH > 7.45
PaCO2 : 35-45
HCO3 > 26
causes of metabolic alkalosis
–taking excess baking soda or alka-seltzer = too much base
–prolonged vomiting
–NG tube
–diuretics
effect of taking too much baking soda or antacids
hypokalemia causing hydrogen to shift out of the intracellular space and potassium goes into the cell
symptoms of metabolic alkalosis
–CNS over-excitability
–confusion
–tremors
–muscle cramps
–paresthesias
–coma
–N/V/D
–respiratory depression
–hypoventilation (compensatory)
–tachycardia
–hypokalemia
respiratory alkalosis
–H2CO3 deficit in ECF
–hyperventilation –> primary event –> CO2 blown off
ABGs for respiratory alkalosis
–pH > 7.45
–PaCO2 < 35
–HCO3 = 22-26
common causes of respiratory alkalosis
–hyperventilation
–increased metabolic demands
–meds
–acute anxiety
–hypoxia
–PE or lung disease
–CNS lesions
–vent settings
symptoms of respiratory alkalosis
–tachypnea
–light headedness
–confusion, blurred vision
–paresthesia
–hyperactive reflexes (seizures)
–coma
respiratory acidosis
H2CO3 in excess
primary event in respiratory acidosis
hypoventilation
primary event for respiratory alkalosis
hyperventilation
ABGs for respiratory acidosis
–pH < 7.35
–PaCO2 > 45
–HCO3 = 22-26
when is HCO3 WNL for respiratory acidosis?
acute respiratory acidosis
no time for kidneys to compensate
signs of respiratory acidosis
–hypoventilation
–dyspnea
–respiratory distress
–shallow respirations
–headache, restlessness, confusion
–tachycardia, arrythmias
–decreased LOC, stupor, coma
common causes of respiratory acidosis
–cardiopulmonary arrest
–head injury
–narcotics/sedatives
–anesthesia
–pulmonary disorders
–pain
–abdominal distention
–airway obstruction
–chest wall deformities
–neuromuscular problems (ALS)
metabolic acidosis
HCO3 deficit in ECF
–excess acids are added or bicarb is lost
ABGs for metabolic acidosis
–pH < 7.35
–PaCO2 = 35-45
–HCO3 < 22
CO2 and compensation with metabolic acidosis
if lungs are compensating, the CO2 will be decreased
symptoms of metabolic acidosis
–lethargy, drowsiness
–confusion
–tremors, muscle cramps
–paresthesias
–hypotension
–hyperkalemia
–deep breathing (Kussmaul’s respirations)
–fruity odor breath (DKA)
common causes of metabolic acidosis
–renal failure
–fistulas
–diabetes (Type 1)
–lactic acidosis
–prolonged diarrhea
–starvation
–medication overdose (aspirin)
–shock and cardiac arrest
respiratory acidosis/alkalosis compensation
kidneys compensate by either:
(1) conserving (reabsorbing) HCO3
(2) excreting HCO3
**hours to days
metabolic acidosis/alkalosis compensation
lungs compensate by either:
(1) conserving CO2 ions
(2) excreting CO2 ions
**kidneys also attempt to correct imbalance by retaining/excreting HCO3
**minutes to hours
rate of compensation with respiratory
rapid
rate of compensation with metabolic
slow
major organ involved in respiratory compensation
lungs
major organ involved in metabolic compensation
kidneys
compensatory mechanism of lungs
hyper/hypoventilation
compensatory mechanism of kidneys
retention/excretion of H+/HCO3
acid-base problem triggering activation of compensation in respiratory
metabolic A-B abnormalities
acid-base problem triggering activation of compensation in metabolic
respiratory A-B abnormalities
interventions for respiratory acidosis
measures to improve ventilation
–increase rate/depth of RR
–stimulate patient/encourage slow and deep respirations
–give sodium bicarb
fully compensated respiratory acidosis
–pH normal, leaning acidic
–PaCO2 high
–HCO3 high
uncompensated respiratory alkalosis
pH high
PaCO2 low
HCO3 WNL
interventions for respiratory alkalosis
–calm patient
–breathe into paper bag
–anti-anxiety meds
–rebreather
fully compensated respiratory alkalosis
pH normal, leaning basic
PaCO2 low
HCO3 low
metabolic acidosis physiology
–pH is down and metabolic acidosis presents as low HCO3
–lungs compensate by increasing the rate and depth of respirations to blow off CO2, moving pH back toward a more normal state
treatment for metabolic acidosis
admin rapid acting insulin to bring BG down
uncompensated metabolic acidosis
pH low
PaCO2 normal
HCO3 low
partially compensated metabolic acidosis
pH low
PaCO2 low
HCO3 low
fully compensated metabolic acidosis
pH normal (leaning acidic)
PaCO2 low
HCO3 low
physiology of metabolic alkalosis
–pH is increased and metabolic alkalosis is present as indicated by high HCO3
–lungs compensate by decreasing rate and depth of respirations to hold on to CO2
uncompensated metabolic alkalosis
pH high
PaCO2 normal
HCO3 high
partially compensated metabolic acidosis
pH low
PaCO2 low
HCO3 low
fully compensated metabolic acidosis
pH normal (leaning low)
PaCO2 low
HCO3 low
pH “leaning toward acid”
pH < 7.4
pH “leaning toward base”
pH > 7.4
uncompensated
–pH abnormal
–acid OR base abnormal
partially compensated
–pH abnormal
–acid AND base abnormal
fully compensated
–pH normal (leaning acid or base)
–acid or base abnormal, but balanced (arrows moving in same direction)
corrected
–pH WNL
–all acid or base parameters WNL
COPD patient balance
compensated, but not corrected
