ABGs - patho 406 Flashcards
purpose of ABGs
to assess acid base status and to determine adequacy of oxygenation & ventilation
primary event
the problem that initiates the acid base imbalance
(ex: hypovent, hypervent, vomiting, diarrhea)
primary disorder
what results from the primary event
(ex: resp acidosis, metabolic alkalosis)
compensation mechanisms
physiologic processes that adjust the pH back to the normal range
(ex: lung problem -> kidney will comp)
general causes of imbalance: metabolic
-HCO3 level changes secondary to metabolic alterations (kidneys)
general causes of imbalance: respiratory
-H2CO3 level changes secondary to respiratory alterations (lungs)
respiratory acidosis or alkalosis
increases or decrease in CO2
change in ventilation
metabolic acidosis or alkalosis
changes in H+ or bicarb ions
acid base mnemonic: ROME
R espiratory
O pposite
inc pH, dec PCO2 = alk; dec pH, inc PCO2 = acid
M etabolic
E qual
inc pH, inc HCO3 = alk; dec pH dec HCO3 = acid
metabolic acidosis: what is it & what is our comp
dec HCO3, dec Ph
comp: lungs blow off CO2 to decrease levels (dec pCO2)
respiratory alkalosis: what is it & what is our comp
dec CO2, inc pH
comp: kidneys get rid of bicard (HCO3) to decrease levels
(dec HCO3)
respiratory acidosis: what is it & what is our comp
inc pCO2, dec pH
comp: kidneys hold on to bicard to increase levels
(inc HCO3)
metabolic alkalosis: what is it & what is our comp
inc HCO3, inc pH
comp: lung hold on to CO2 to increase levels
(inc pCO2)
metabolic alkalosis: ABG
too much bicard or not enough carbonic acid
pH > 7.48 (B)
PaCO2: 35-45 (N)
HCO3 >29 (B)
metabolic alkalosis: causes
-taking excess baking soda, alka-seltzer (H shifts out of the cell & K+ goes in causing hypoK)
-prolonged vomiting
-NG tube suctioning
-diuretics (lose H but bicard stays)
metabolic alkalosis: clinical manifestations
CNS over excitability
confusion
tremors
muscle cramps
parethesias
coma
N/V/D
resp depression (to try to hold on to CO2)
respiratory alkalosis: ABGs
H2CO3 deficit in extracellular fluid
pH >7.45 (H/basic)
PaCO2 <35 (L)
HCO3-: 24-29 (N)
respiratory alkalosis: causes
-hyperventilation (primary event)
kidneys need to comp but can’t work quickly so often time these pts pass out
-fever / sepsis (inc metabolic demand)
-medications
-acute anxiety
-hypoxia
-PE or lung disease
-CNS lesions
-ventilator
respiratory alkalosis: clinical manifestations
-CNS over excitability
-tachypnea
-light headedness
-confusion, blurred vision
-paresthesia
-hyperactive reflexes
-coma
respiratory acidosis: ABGs
H2CO3 excess in ECF
pH <7.35 (L/acidic)
PaCO2 > 45 (H)
HCO3-: 24-29 (N)
hco3 is wnl w/ acute resp acid bc kidneys don’t have time to comp -> if copd/chronic high bicard and normal pH d/t comp
respiratory acidosis: clinical manifestation
-hypoventilation (primary event)
-dyspnea
-respiratory distress
-H/a, restlessness, confusion
-tachycardia, arrhythmias
-dec LOC, stupor, coma
when a pt goes into respiratory arrest, they become
acidotic bc they are not breathing
respiratory acidosis: causes
not taking good breaths or any
-hypoventilation
-cardiopulmonary arrest
-head injury
-narcotics/sedatives
-anesthesia
-pulmonary disorders
-pain (not taking deep breaths)
-abdominal distension
-airway obstruction
-chest wall deformities
-neuromuscular problems
metabolic acidosis: ABGs
HCO3 deficit in the ECF
pH < 7.35 (L/acidic)
PaCO2: 35-45
HCO3- <24 (L)
metabolic acidosis: causes
-renal failure
-fistulas
-DKA
-lactic acidosis
-prolonged diarrhea (lose bicarb)
-starvation (ketosis)
-shock & cardiac arrest
metabolic acidosis: clinical manifestations
-lethargy, drowsiness, confusion, tremors, muscle cramps, paresthesia
-hypotension
-hyperkalemia
-deep breathing (kussmaul respirations in DKA)
summary of respiratory comp
Rate: rapid
Organ: Lungs
activity: hyper/hypo vent
trigger: met acid-base abnorm
summary of metabolic comp
Rate: slow
Organ: Kidneys
activity: retention/excretion of H+/HCO3
trigger: resp acid-base abnorm
what do we do for pt w/ respiratory acidosis
-give narcan if drug related
-bag mask
-intubate
do not give bicarb bc doesn’t fix respiratory problem
what would some w/ respiratory acidosis ABGs look like if they have COPD
they will be fully compensated
pH: normal
PCO2: high
HCO3: high
what would we do for a patient with respiratory alkalosis
-calm
-anti anxiety meds
-breathing into paper bag
-rebreather
what will someones ABGs look like in respiratory alkalosis who is fully compensated
pH: normal/basic
PCO2: low
HCO3: low
what do for someone w/ metabolic acidosis
treat the cause
ex: if DKA, bring down BG
what would someones ABGs look like if they have fully compensated metabolic acidosis
pH: normal - acidic
PacCO2: low
HCO3: low
with compensation, the arrow will always move….
in the same direction as the disorder
what would someones ABGs look like if they have fully compensated metabolic alkalosis
ph: normal
PaCO2: high
HCO3: high
treatment for metabolic alkalosis
treat the cause so if vomiting give drugs to reduce gastric hydrochloric acid secretions
what is the parameters for the pH to be leaning after compensation has occurred
neutral = 7.4
-leaning toward acidic: <7.4
-leaning toward base: >7.4
uncompensated
pH abnormal, acid or base abnormal
partially compensated
pH abnormal, acid and base component abnormal
compensated
pH normal, acid or base imbalance is neutralized but not corrected -> arrows moving in same direction
