The cyanosis that accompanies bacterial pneumonia is primarily caused by which of the following?
A. Decreased cardiac output.
B. Pleural effusion.
C. Inadequate peripheral circulation.
D. Decreased oxygenation of the blood.
Correct Answer: D. Decreased oxygenation of the blood.
A client with pneumonia has less lung surface available for the diffusion of gases because of the inflammatory pulmonary response that creates lung exudate and results in reduced oxygenation of the blood. The client becomes cyanotic because blood is not adequately oxygenated in the lungs before it enters the peripheral circulation. It is evident that the cyanosis of pneumonia patients is due to the incomplete saturation of venous blood with oxygen in the lungs, and that the various shades of blue observed in the distal parts are caused by an admixture of reduced hemoglobin and oxyhemoglobin in the superficial capillaries.
Option A: With expansion of blood volume in the acute phase of pneumonia, all patients showed an increase in cardiac output, a decrease in arteriovenous oxygen difference, and a decrease in peripheral vascular resistance; however, the percentage change in the hypodynamic patients was not as great as occurred in the patients with normal hemodynamics nor as great as occurred when restudied in convalescence.
Option B: Pleural effusions are common in patients who develop pneumonia. At least 40-60% of patients with bacterial pneumonia will develop a pleural effusion of varying severity. Today, these parapneumonic effusions are not common because of prompt antibiotic therapy.
Option C: The inadequate response to pneumonia is most consistent with depressed myocardial function, but the possibility of decreased intravascular volume as a contributory factor could not be excluded. The arteriovenous oxygen difference was used to assess the adequacy of the circulation to meet peripheral tissue perfusion, and a spectrum of arteriovenous oxygen differences was noted.
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