Hospital-acquired pneumonia overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

American Thoracic Society (ATS) and the Infectious Disease Society of America (IDSA) definitions of Hospital acquired pneumonia, ventilator-associated pneumonia, and health care associated pneumonia

Hospital-acquired pneumonia (HAP)

HAP is defined as pneumonia that occurs 48 hours or more after admission, which was not incubating at the time of admission

Ventilator-associated pneumonia (VAP)

VAP refers to pneumonia that arises more than 48–72 hours after endotracheal intubation. Some patients may require intubation after developing severe HAP and should be managed similar to patients with VAP.

Healthcare-associated pneumonia (HCAP)

HCAP includes any patient who was hospitalized in an acute care hospital for two or more days within 90 days of the infection; resided in a nursing home or long-term care facility; received recent intravenous antibiotic therapy, chemotherapy, or wound care within the past 30 days of the current infection; or attended a hospital or hemodialysis clinic. }}

Pathophysiology

Most nosocomial respiratory infections are caused by so-called skorvatch microaspiration of upper airway secretions, through inapparent aspiration, into the lower respiratory tract. Also, "macroaspirations" of esophageal or gastric material is known to result in HAP. Since it results from aspiration either type is called aspiration pneumonia. Although gram-negative bacilli are a common cause they are rarely found in the respiratory tract of people without pneumonia, which has led to speculation of the mouth and throat as origin of the infection.

Causes

The majority of cases related to various gram-negative bacilli (52%) and S. aureus (19%). Others are Haemophilusspp. (5%). In the ICU results were S. aureus(17.4%), P. aeruginosa (17.4%), Klebsiella pneumoniae andEnterobacter spp. (18.1%), and Haemophilus influenzae (4.9%). Viruses -influenza and respiratory syncytial virus and, in the immunocompromised host, cytomegalovirus- cause 10-20% of infections.

Differentiating Hospital-acquired pneumonia from other diseases

• Atelectasis
• Congestive heart failure
• Pulmonary embolism

Epidemiology and Demographics

Pneumonia is a common illness in all parts of the world. It is a major cause of death among all age groups. Mortality from pneumonia generally decreases with age until late adulthood. Elderly individuals, however, are at particular risk for pneumonia and associated mortality. More cases of pneumonia occur during the winter months than during other times of the year. Pneumonia occurs more commonly in males than females, and more often in Blacks than Caucasians. Individuals with underlying illnesses such as Alzheimer's disease, cystic fibrosis, emphysema, tobacco smoking,alcoholism, or immune system problems are at increased risk for pneumonia. These individuals are also more likely to have repeated episodes of pneumonia. People who are hospitalized for any reason are also at high risk for pneumonia. Following urinary tract infections, this is the second common cause of nosocomial infections, and its prevalence is 15-20% of the total number

Diagnosis

Diagnostic Criteria

In hospitalised patient who develop respiratory symptoms and fever one should consider the diagnosis. The likelyhood increases when upon investigation symptoms are found of respiratory insufficiency, purulent secretions, newly developed infiltrate on the chest X-Ray, and increasing leucocyte count. If pneumonia is suspected material from sputum or tracheal aspirates are sent to the microbiology department for cultures. In case ofpleural effusion thoracentesis is performed for examination of pleural fluid. In suspected ventilator-associated pneumonia it has been suggested that bronchoscopy(BAL) is necessary because of the known risks surrounding clinical diagnoses.

History and Symptoms

Pneumonia fills the lung's alveoli with fluid, keeping oxygen from reaching the bloodstream. The alveolus on the left is normal, while the alveolus on the right is full of fluid from pneumonia.

People with pneumonia often have a productive cough, fevershaking chills, Shortness of breath, pleuritic chest pain, cough up blood, headaches, sweaty, and clammy skin. Other possible symptoms are loss of appetite, fatigue, blueness of the skin, nausea,vomiting, mood swings, andjoint pains or muscle aches. In elderly people manifestations of pneumonia may not be typical. They may develop a new or worsening confusion or may experience unsteadiness, leading to falls. Infants with pneumonia may have many of the symptoms above, but in many cases they are simply sleepy or have a decreased appetite.