Hospital-Acquired Pneumonia

Hospital-acquired pneumonia (HAP) is a new infection of the lung parenchyma that develops more than 48 hours after hospital admission. Epidemiologic data suggest that HAP occurs in up to 1% of patients, prolongs hospital stay by 7 to 9 days, and represents the most common hospital-acquired infection leading to death. The morbidity and mortality attributed to HAP are significantly increased if infection is caused by multidrug-resistant pathogens. The subset of HAP occurring more than 48 hours after initiation of mechanical ventilation is termed ventilator-associated pneumonia (VAP). Risk factors for HAP and VAP are diverse and include both patient-specific and treatment-associated elements. Clinical defining criteria for pneumonia require a new or worsening infiltrate on chest radiography in conjunction with typical clinical and laboratory findings. Although microbiologic confirmation is ideal, the optimal diagnostic strategy is hotly debated. Recent trends in the microbial resistance rates for pathogens causing HAP have led to significant changes in the recommendations for empirical therapy, with an increased reliance on broad-spectrum therapy followed by culture-based deescalation. Empirical treatment decisions must also take into consideration local microbiologic data, host-specific risk factors, and the severity of the patient's acute illness. Limited new antibiotic development and high attributable mortality rates highlight the importance of evidence-based HAP prevention strategies.