Acid-Base Balance Flashcards
Normal ABG’s for acid-base balance
arterial pH: 7.35-7.45 (< 7.35 acidosis)
pCO2: 35-45 mm Hg (> 45 acidosis)
HCO3-: 22-26 mm Hg (< 22 acidosis)
pO2: 80-100 mm Hg (< 80 hypoxia)
Causes of respiratory alkalosis
hyperventilation (due to anxiety, pain, etc.) excessive ventilation (mechanical ventilator rate too high)
Causes of metabolic alkalosis
excessive vomiting or gastric suction excessive intake of antacids or alkaline foods kidney dysfunction (decreased bicarbonate excretion) hypokalemia (due to diuretics - causes exchange of K+ out of cell and H+ into cell)
Causes of respiratory acidosis
COPD/hypoventilation/hypercapnea
insufficient mechanical ventilation (rate too low)
decreased hypoxic drive (high O2 with COPD causes respiratory depression)
respiratory failure
Causes of metabolic acidosis
Diabetes (ketoacidosis) Hypoxia (due to anaerobic metabolism causes increase in lactic acid) excessive diarrhea (loss of bicarbonate) excessive intake of acidic foods hyperkalemia (increased exchange of K+/H+)
Clinical manifestations of alkalosis (respiratory and metabolic)
CNS excitability: tremors, irritability, restlessness, tachycardia (increased HR)
Vasoconstriction
Heart dysrhythmias due to hypokalemia and hypocalcemia
Manifestations of hypocalcemia: paresthesias, muscle spasms
Clinical manifestations of acidosis (respiratory and metabolic)
CNS depression: confusion, drowsiness, headaches
Vasodilation –> flushed skin
Manifestations of hypercalcemia: muscle weakness
Hyperkalemia
Normal ratio of acid to base (H2CO3 to HCO3-)
1:20
1 parts H2CO3 to 20 parts HCO3-
Explain the 3 mechanisms for acid-base balance in the body
Buffers are 1st
Carbonic acid system is most prevalent extracellular buffer; proteins and phosphates are most prevalent intracellular buffers
Once buffer system is saturated, then respiratory system intervenes:
H2O + CO2 H2CO3 H+ + HCO3-
If pH is acidic, then increase RR to exhale CO2 to drive formula to LEFT to decrease H+ and raise pH
If pH is alkalotic, then decrease RR to retain CO2 and drive formula to RIGHT to increase H+ and lower pH
Lungs maintain acid-base balance for short-term; kidneys maintain acid-base balance for long term
If pH is acidic, then kidneys excrete more H+ and retain HCO3-; if pH is alkalotic, then kidneys excrete HCO3- and retain H+
Explain the difference between compensated, uncompensated, and corrected acid-base balance states
uncompensated state when pH outside normal range; but respiratory or renal systems unable to compensate for the acid-base balance - will show as imbalance in kidneys with lungs unable to compensate in opposite direction, or vice versa
Compensated state: when pH is in normal range but respiratory and renal systems in opposite directions enough to “cancel each other out”
Corrected: when pH and both respiratory and renal system lab values within normal range
Explain the emergency intervention for hyperkalemia
IV insulin (bolus then infusion with glucose) because insulin causes potassium and glucose uptake by cells - glucose is given to prevent hypoglycemia
Briefly describe the interventions for respiratory acidosis
remove the cause if possible (bronchodilation, increase CO2 elimination, O2 therapy, etc.)
normalize blood volume
IV: Ringer’s lactate infusion (converted to bicarbonate in the liver)
Briefly describe the interventions for metabolic acidosis
identify and remove cause e.g. if due to kidney failure, then intervene with dialysis, or if due to DKA, then administer insulin
Alkalinize patient with bicarbonate, lactate, acetate, or citrate (the last 3 require normal liver function to convert to bicarbonate)
Fluid replacement as necessary
Briefly describe the interventions for respiratory alkalosis
remove the cause of hyperventilation and intervene with sedatives if needed
IV solution with saline (chloride ions are exchanged with bicarbonate in the kidney***)
Briefly describe the interventions for metabolic alkalosis
IV to restore volume depletion
Potassium supplements to correct hypokalemia
IV NS or chloride solutions (Cl- exchange with bicarbonate in kidney)
