Acid-Base Imbalance Flashcards
partially compensated
process has begun, but pH is abnormal
compensated
pH is normal, but CO2 and HCO3- are still abnormal
expected pH
7.35-7.45
expected PaCO2
35-45 mm Hg
expected HCO3
22-26 mm Hg
ROME for interpreting ABGs quickly
- Respiratory
- *O**pposite
- pH ↑ PaCO2 ↓ alkalosis
- pH ↓ PaCO2 ↑ acidosis
- Metabolic
- *E**qual
- pH ↑ PaHCO3 ↑ alkalosis
- pH ↓ PaHCO3 ↓ acidosis
alkalosis
↑ pH
acidosis
↓ pH
respiratory alkalosis
↓ pH
↑ PaCO2
respiratory acidosis
↓ pH
↑ PaCO2
metabolic alkalosis
↑ HCO3
↑ pH
metabolic acidosis
↓ HCO3
↓ pH
organs responsible for acid-base balance
- kidneys: metabolic
- lungs: respiratory
respiratory acid
CO2
metabolic alkaline component
HCO3
steps to interpret ABG
- look at pH: high or low?
- high = alkalosis
- low = acidosis
- normal + abornomal gas = fully compensated
- look at PaCO2: opposite of pH?
- yes = respiratory
- look at HCO3: same direction as pH?
- yes = metabolic
- If neither both fit the pattern, it’s mixed
full compensation
- pH is normal, but PaCO2 and PaHCO3 are abnormal
- pH is slightly acidic or alkalotic
- 7.4 = midpoint
- 7.35-7.39 = slightly acidic = acidosis
- 7.41-7.45 = slightly alkalotic = alkalosis
partial compensation
- acidosis or alkalosis?
- respiratory or metabolic (ROME)?
- the other component won’t fit ROME pattern, and that’s the one that’s compensating
mixed acid-base imbalance
just metabolic or alkalotic
mild hypoxemia
PaO2 = 60-79 mm Hg
moderate hypoxemia
PaO2 = 40-59 mm Hg
severe hypoxemia
PaO2 < 40 mm Hg
expected PaO2
80-100 mm Hg
pH 7.30
PaCO2 53
PaHCO3 24
respiratory acidosis
pH 7.48
PaCO2 29
PaHCO3 23
respiratory alkalosis
pH 7.32
PaCO2 44
PaHCO3 19
metabolic acidosis
pH 7.52
PaCO2 36
PaHCO3 32
metabolic alkalosis
pH 7.36
PaCO2 55
PaHCO3 31
fully compensated repiratory acidosis
pH 7.43
PaCO2 50
PaHCO3 35
fully compensated metabolic alkalosis
pH 7.47
PaCO2 30
HCO3 20
partially compensated repiratory alkalosis
pH 7.47
PaCO2 30
PaHCO3 28
mixed alkalosis
three types of compensatory mechanisms in acid-base disturbance and when they respond
- buffers: seconds
- respiratory: seconds to minutes
- renal/kidney/metabolic: 24-48 hr
respiratory acidosis
- caused by hypoventilation of any etiology
- COPD
- oversedation
- head trauma
- anesthesia
- neuromuscular dz like myasthenia gravis or Guillian-Barre
- inappropriate mechanical ventilation
- sleep apnea
- s/sx
- rapid, shallow respirations
- ↓ BP
- skin/mucosa pale to cyanotic
- hyperkalemia
- dysrhythmias (↑ K+)
- drowsiness
- dizziness
- disorientation
- muscle weakness
- hyporeflexia
respiratory acidosis Tx
- assess airway for patency
- patent
- position in semi- to high Fowler’s
- encourage coughing and deep breathing, incentive spirometry
- oxygen therapy if needed
- not patent: mechanical ventilation
- medications
- bronchodilators
- anti-inflammatories
- narcan (opioid overdose)
metabolic acidosis***
- harder to correct than respiratory imbalance
- caused by gain in nonbolatile acids (ketoacids, lactic acid, etc.)
- DKA
- renal failure
- lactic acidosis
- poisoning
- salicylates
- ethylene glycol
- methyl alcohol
- paraldehyde
- caused by loss of HCO3
- diarrhea
- drainage of***
- liver damage
- dehydration
metabolic acidosis
- headache
- lower BP
- hyperkalemia
- muscle twitching
- warm, flushed skin
- nausea
- vomiting
- lower muscle tone
- lower reflexes
- confusion
- drowsiness
- Kussmaul respirations
metabolic acidosis causes
- ↑ H+ production
- DKA
- hypermetabolism
- ↓ H+ elimination
- renal failure
- ↓ HCO3 production
- dehydration
- liver failure
- ↑ HCO3 elimination
- diarrhea
- fistulas
Tx: metabolic acidosis
- hydration
- meds to reverse cause
- insulin
- antidiarrheal
- sodium bicarbonate to buffer in emergent period
- rare because of rebound
respiratory alkalosis
- low PaCO2
- caused by hyperventilation because of
- hypoxemia
- nervousness and anxiety
- pulmonary embolism
- pregnancy
- inappropriate mechanical ventilation
- compensation for metabolic acidosis
s/sx of respiratory alkalosis
- lightheadedness
- hyperventilation (↑ rate and depth
- tachycardia
- ↓ or normal BP
- hypokalemia
- numbness and tingling in extremities or around lips
- hyperreflexes and muscle cramping
- sz
- anxiety, irritability
Tx for respiratory alkalosis
- increase sedation
- control pain/anxiety to lower resp rate
- possible mechanical ventilation when lungs start to give out or regulate respirations
metabolic alkalosis
- elevated bicarb
- loss of nonvolatile acids (keto and lactic)
- loss of gastric acid (vomiting)
- bicard admin during cardiac arrest
- now only give if pH < 7.1 or 7.0
- baking soda intake (usually for heartburn)
- massive blood transfusion
- ↑ intake of H+, K+, and Cl- because of
- diuretics
- Cushing’s
- corticosteroids
- aldosteronism
s/sx of metabolic alkalosis
- confusion
- dysrhythmias
- tachycardia r/t ↓ K+
- hypoventilation (compensatory)
- dizziness
- increased irritability
- nausea
- vomiting
- diarrhea
- increased anxiety
- sz
- decreased serum Ca++
- tremors
- muscle cramps
- tingling of fingers and toes
Tx for metabolic alkalosis
- stop Tx that may have caused it
- NG tube suctioning
- diuretics
- bicarb admin
- replace lost electrolytes
- admin antiemetics
