1. Chest x-ray. Look for pulmonary edema, infiltrates, pneumothorax, size of cardiac silhouette (increased with congestive heart failure or pericardial effusion), and endotracheal tube position.
2. ECG. Evaluate for arrhythmias.
V. Plan. Appropriate treatment depends on identifying underlying cause of the acidosis.
A. Respiratory Acidosis. If patient is oversedated with narcotics or benzodiazepines, consider administration of specific antidote. Electrolyte abnormalities (eg, hypokalemia, hypophosphatemia, hypocalcemia) may lead to muscular weakness and should be rapidly corrected. If patient has a neuromuscular disorder, noninvasive ventilation, such as continuous or bilevel positive airway pressure (CPAP or BiPAP), may be helpful. Extrinsic pulmonary disease (eg, pneumothorax, pleural effusion) should be treated specifically. Foreign bodies will require removal. Severe bron-choconstriction, as in asthma, should be aggressively treated with 0-agonists, steroids, ipratropium, and possibly magnesium. Endotracheal intubation and mechanical ventilation should be considered if mental status is abnormal, if patient appears to be "tired" from the high work of breathing, if there is poor response to initial therapies, or if oxygenation is compromised.
B. Metabolic Acidosis. Treat non-AG metabolic acidosis by replacing volume losses. Use isotonic fluid with low Cl- content. Specific treatments exist for most causes of AG metabolic acidosis. These may include insulin for diabetic ketoacidosis; dialysis for renal failure; fluids, inotropes, pressors, and antibiotics for septic shock. Use of HCO3 for lactic acidosis is controversial; if warranted, HCO3 therapy can be guided by the following formula:
Body weight (kg) x 0.40 (volume of distribution of bicarbonate) x (24 - HCO3]) = Total mEq HCO3
Give 50% of this amount in the first 12 hours by adding HCO3 to a solution of D5W.
VI. Problem Case Diagnosis. The 8-year-old patient had respiratory acidosis from inadequate ventilation secondary to reactive airway disease. She was given continuous aerosolized albuterol, intermittent aerosolized ipratropium bromide, and IV steroids. After minimal improvement, inhaled heliox (70%) was begun. Over the next several hours, she improved and heliox was discontinued. Ipratropium was stopped and albuterol was slowly weaned over the next 1-2 days.
Patient was discharged to home with instructions to continue albuterol and steroids.
VII. Teaching Pearl: Question. What is the significance of the absence of wheezing in the presence of respiratory distress or respiratory acidosis?
VIII. Teaching Pearl: Answer. Absence of wheezing may indicate that patient is extremely "tight" and unable to move enough air to cause a wheeze. Beware of the "silent chest."
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