Complications table

septic shock

short termmedium

Commonly complicates severe CAP. Patients 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 renal 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.[159]

acute respiratory distress syndrome (ARDS)

short termmedium

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%.[160]

Associated with a 30% to 50% mortality, and treated with low tidal volume plateau pressure limited mechanical ventilation.[31]

antibiotic-associated Clostridium difficile colitis

short termmedium

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.

heart failure

short termmedium

The incidence of heart failure in hospitalized patients with CAP was 14.1% in one study.[161] There is little information about risk factors for the occurrence of cardiac complications in patients with CAP. 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.[162][163][164] In patients with known cardiovascular disease, use of pneumococcal and influenza vaccine may reduce morbidity and mortality.

acute coronary syndrome

short termlow

The incidence of acute coronary syndrome in hospitalized patients with CAP was 5.3% in one study.[161]

cardiac arrhythmias

short termlow

The incidence of incident cardiac arrhythmia in hospitalized patients with CAP was 4.7% in one study.[161]

necrotizing pneumonia

short termlow

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.[168]

pleural effusion


May occur in up to 57% of hospitalized pneumonia patients.[165][166] 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.[17][167]

lung abscess


A rare complication, frequently requiring prolonged antibiotic therapy and, in some cases, surgical drainage.

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