Metabolic Acidosis
Acidosis, usually due to high levels of lactate, stimulates respiratory drive to try and balance pH. Sepsis is the most important cause of acidosis. When sepsis is developing, dyspnea frequently is a subtle sign. Have a high index of suspicion for sepsis, and be wary of a normal oxygen saturation level in a patient with dyspnea, he said. Other causes of metabolic acidosis that lead to dyspnea include diabetic or alcoholic ketoacidosis.
Putting this physiologic approach to dyspnea into context, consider three scenarios, Dr. Sankoff suggested. A patient with dyspnea who responds to oxygen therapy and has an abnormal chest x-ray has a primary pulmonary problem. A patient who responds to oxygen but has a normal chest x-ray may have sepsis, another cause of acidosis, or alveolar hypoventilation; their response to oxygen may be transient. They will respond to oxygen but continue to be tachypneic.
The third scenario – normal x-ray, but the patient does not respond to oxygen therapy – raises a broad differential diagnosis including sepsis, other causes of acidosis, hypercapnia, cardiac causes, and hemoglobinopathies. Narrow the differential by recalling the history and physical findings and getting arterial blood gas tests.
Only after everything else has been excluded should you consider anxiety or pain as the cause of dyspnea, he said.
Dr. Sankoff reported having no financial disclosures.