Hospital-acquired pneumonia overview
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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. ; Philip Marcus, M.D., M.P.H.
Overview
Hospital-acquired pneumonia (HAP) or nosocomial pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48–72 hours after being admitted. It is thus distinguished from community-acquired pneumonia. It is usually caused by a bacterial infection, rather than a virus.[1][2] HAP is the second most common nosocomial infection (after urinary tract infections ) and accounts for 15–20% of the total.[1][2][3] It is the most common cause of death among nosocomial infections and is the primary cause of death in intensive care units.[1][3] HAP typically lengthens a hospital stay by 1–2 weeks.[1][3]
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
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.[4] 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
Risk Factors
Among the factors contributing to contracting HAP are mechanical ventilation (ventilator-associated pneumonia), old age, decreased filtration of inspired air, intrinsic respiratory, neurologic, or other disease states that result in respiratory tract obstruction, trauma, (abdominal) surgery, medications, diminished lung volumes, or decreased clearance of secretions may diminish the defenses of the lung. Also poor hand-washing and inadequate disinfection of respiratory devicescauses cross-infection and is an important factor.
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
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.
Laboratory Findings
Current guidelines recommend a combination of chest Xray,laboratory data as well as clinical judgment in diagnosis and management of community acquired pneumonia.
Treatment
Medical Therapy
Methicillin-resistant staphylococcus aureus is a common isolate in the patients with Hospital-acquired pneumonia. The treatment options commonly used are vancomycin, linezolid, and clindamycin. Linezolid may be preferred in patients with renal insufficiency as the nephrotoxicity with Linezolid is less compared to vancomycin. Additionally, in patients with vancomycin MIC ≥ 2mcg/mL linezolid is preferred. Linezolid resistance and failure are rare.
References
- ↑ 1.0 1.1 1.2 1.3 Mandell's Principles and Practices of Infection Diseases 6th Edition (2004) by Gerald L. Mandell MD, MACP, John E. Bennett MD, Raphael Dolin MD, ISBN 0-443-06643-4 · Hardback · 4016 Pages Churchill Livingstone
- ↑ 2.0 2.1 The Oxford Textbook of Medicine Edited by David A. Warrell, Timothy M. Cox and John D. Firth with Edward J. Benz, Fourth Edition (2003), Oxford University Press, ISBN 0-19-262922-0
- ↑ 3.0 3.1 3.2 Harrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill Companies, ISBN 0-07-140235-7
- ↑ Almirall J, Bolibar I, Balanzo X, Gonzalez CA. Risk factors for community-acquired pneumonia in adults: A population-based case-control study. Eur Respir J. 1999;13:349. PMID 10065680