Complications
Sepsis is a life-threatening condition and is the main complication of severe pneumonia, observed in approximately one in three patients with severe community-acquired pneumonia (CAP).[3]
Patients may have fever, leukocytosis, tachypnea, tachycardia. Can progress rapidly to multi-organ failure and shock. It is often fatal, and survival is dependent on a high index of suspicion, early recognition, and immediate intervention.
The prevalence of sepsis in very old patients (≥80 years) with CAP was 71%. Risk factors included: male sex, chronic kidney disease, and diabetes mellitus. Antibiotic therapy before admission was associated with a lower risk of sepsis. In-hospital and 1-year mortality rates were increased in these patients if they developed sepsis.[211]
Pneumonia can be complicated by ARDS, which is a condition of noncardiogenic pulmonary edema and severe lung inflammation.
Reported in 2% of CAP patients who are hospitalized, and 13% of CAP patients who are admitted to the intensive care unit. Occurs in 29% of CAP patients who are mechanically ventilated, with a 30-day mortality of 25%.[212]
Associated with a 30% to 50% mortality, and treated with low tidal volume plateau pressure limited mechanical ventilation.[37]
May occur as a result of interruption of the normal bowel flora from antibiotic use. Patients generally have diarrhea, abdominal pain, and leukocytosis. Stool immunoassay for C difficile enzymes is diagnostic. Ideally, causative antibiotics should be stopped, and antibiotic treatment started according to current local guidance.
Cardiovascular complications are a common and serious consequence of community-acquired pneumonia (CAP), particularly in severe cases of pneumococcal CAP, occurring in up to 30% of hospitalized patients. These include arrhythmias, acute myocardial infarction (AMI), and heart failure, often arising within the first 24 hours of illness and contributing to both short- and long-term mortality. Mechanisms such as pneumococcal microlesions in cardiac tissue, the action of pneumolysin, and platelet activation have been implicated. Similar cardiac risks have been identified in viral pneumonias caused by SARS-CoV-2, influenza virus, and respiratory syncytial virus (RSV). In one large study of over 32,000 hospitalizations, RSV was associated with higher odds of acute cardiovascular events compared to COVID-19, regardless of vaccination status. While RSV and influenza had similar overall cardiac risk, RSV demonstrated a higher risk of heart failure in recent years (2023-2024). Cardiovascular events were also linked to more severe RSV illness.[213][214]
The incidence of heart failure in hospitalized patients with CAP was 14.1% in one study.[215] Older age, pre-existing congestive heart failure, severity of CAP, and the use of insulin by glucose sliding scales in hospitalized patients are possible risk factors.[216][217][218] In patients with known cardiovascular disease, use of pneumococcal and influenza vaccine may reduce morbidity and mortality.
The incidence of acute coronary syndrome in hospitalized patients with community-acquired pneumonia was 5.3% in one study.[215]
The incidence of incident cardiac arrhythmia in hospitalized patients with community-acquired pneumonia was 4.7% in one study.[215]
Regarded as a rare complication of CAP in adults. Associated with pathogens such as Staphylococcus aureus, Streptococcus pyogenes, Nocardia species, Klebsiella pneumoniae, and Streptococcus pneumoniae.
Smoking, alcoholism, old age, diabetes mellitus, chronic lung diseases, or liver disease are risk factors associated with necrotizing pneumonia.[222]
May occur in up to 57% of hospitalized pneumonia patients.[219][220] About 1% to 2% of CAP cases with pleural effusion are complicated with empyema.
Pleural effusion is considered to be an indicator of pneumonia severity and is clearly associated with an increased risk of treatment failure.[79][221]
A rare complication, frequently requiring prolonged antibiotic therapy and, in some cases, surgical drainage.
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