Signs and Tests
Physical examination may reveal crackling sounds in the lungs. Tests which can help diagnose this condition include:
- Chest X-ray
- Sputum culture
- CBC
- Blood culture
- Bronchoscopy
- Swallowing studies
- CT scan of the chest
The lab studies obtained should be guided by the clinical presentation. Patients with signs or symptoms of sepsis or septic shock require further lab testing than those with uncomplicated aspiration syndromes. The following lab tests are useful in both aspiration pneumonia and pneumonitis.
- Complete blood count with differential
- Determine white count as marker of possible infection.
- Determine band count; a left shift further supports the diagnosis of bacterial pneumonia.
- Determine baseline hemoglobin/hematocrit and platelets for further management.
- Basic metabolic panel
- Serum electrolytes, BUN, and creatinine can be used to assess fluid status and the need for intravenous hydration. This is especially important in patients presenting with fever, vomiting, or diarrhea that may have significant fluid loss.
- Serum BUN and creatinine can also be used to assess renal function in order to appropriately dose antibiotics. In addition, these values can be used to assess end-organ damage in patients who present with sepsis or septic shock.
- Arterial blood gas
- Arterial blood gas is used to assess oxygenation and adds information to guiding oxygen supplementation.
- Assess the patient’s pH status.
- Lactate (often included with blood gases) can be used as an early marker of severe sepsis or septic shock.
- Mixed venous gas
- This should be obtained in any patient in whom septic shock is suspected.
- Decreased mixed venous oxygen saturation is a marker for septic shock.
- Blood cultures
- Baseline screening for bacteremia
- In uncomplicated pneumonia (no signs of sepsis or septic shock), blood cultures have a low yield and are not necessary for initial management and treatment.
- Sputum culture and Gram stain – Generally not helpful in initial diagnosis or treatment
Imaging Studies
A chest radiograph – PA and lateral – is used to locate any infiltrate. The right middle and lower lung lobes are the most common sites of infiltrate formation, due to the larger caliber and more vertical orientation of the right main stem bronchus.
Patients who aspirate while standing can have bilateral lower lung lobe infiltrates.
Patients lying in the left lateral decubitus position are more likely to have left-sided infiltrates. The right upper lobe is a common area of consolidation in alcoholics who aspirate in the prone position.
The presence of pleural effusion may indicate the need to perform thoracentesis to rule out empyema. A chest CT is not usually necessary on an emergent basis, although in the presence of pleural effusion or empyema, it may aid in further characterization of the infiltrate.