(↓ pH + ↑ PCO2)
( ↓pH [<7.35] + ↓ HCO3 [<20], ↓ PCO2 )
Inadequate ventilation or increased dead space.
- Head or chest trauma
- Oversedation, obtundation, or coma
- Neuromuscular disorders
- Pickwickian syndrome (obesity-hypoventilation syndrome)
Renal compensation occurs after 48 hrs of steady state.
Normal anion gap [Na − (K + Cl)] = 12
- Renal losses:
Renal tubular acidosis or acetazolamide
- GI losses:
Diarrhea or malabsorption
- Adrenal insufficiency
- Renal insufficiency
Renal tubular acidosis
- Intubation, mechanical ventilation
- RTA Type 1, & 2 ( ↓ K) : Potassium Citrate (Urocit-K) 20-40 mEq PO qd +/- HCTZ 12.5-50mg PO qd.
- RTA Type 4 ( ↑ K) : Lasix 20-80mg po qd OR bumetanide 0.5-2mg PO qd
- Refractory Acidosis : Na HCO3 8.4% (1mEq/ml) @ 50 cc/hr.
- Likely HypOventilating = Retaining CO2
- Goal = Help pt blow off CO2
- Ventilatory support
- O2 may be necessary to treat hypoxia, but may worsen hypercapnia in patients with COPD or in heavily sedated patients.
- May need to be intubated
- Treating the underlying cause is the most important action.
- Sodium bicarbonate treatment is a controversial and potentially dangerous treatment because of the risk of electrolyte disturbances and paradoxical cerebral acidosis. The cerebral acidosis occurs 2° to the inability of HCO3 to quickly cross the blood-brain barrier. Bicarbonate for the treatment of acidosis should only be considered for extremely ill patients with severe acidosis.
- A brief reminder of some special treatments of underlying causes of metabolic acidosis includes:
- Ethylene glycol and methanol: Fomepizole, Ethanol or 4-methylpyrazole and dialysis
- Salicylate toxicity: HCO3 to keep serum pH between 7.3 and 7.5 with resultant urine alkalinization; dialysis
- Iron overdose: Deferoxamine
- Isoniazid: Pyridoxine (vitamin B6)
Acidosis Management: (pH < 7.30)
If pH 7.15-7.30:
- Increase RR until pH > 7.30 or PaCO2 < 25 (Maximum set RR = 35).
If pH < 7.15:
- Increase RR to 35.
- If pH remains < 7.15, VT may be increased in 1 ml/kg steps until pH > 7.15 (Pplat target of 30 may be exceeded).
- May give NaHCO3 2-5 mEq/kg IV x1
Alkalosis Management: (pH > 7.45)
- Decrease vent rate if possible
Acute Respiratory Acidosis:
Chronic Respiratory Acidosis: