Pneumonia in the critically ill hospitalized patient: part 2
Approximately one week after discharge from the intensive care unit, the patient again developed dyspnea, cough productive of green sputum, and fever to 38.3°C. A repeat chest radiograph (Fig 3) demonstrated persistent infiltrates in the right chest along with specimen brush was repeated and again Pseudomonas aeruginosa was recovered in greater than 104 organisms per ml. However, at this time, the organism demonstrated a different sensitivity pattern than the original organism and appropriate antibiotic therapy was initiated. In addition, bronchoscopy with bronchoalveolar lavage demonstrated Pneumocystis carinii on Giemsa staining and therapy with trimethoprim-sulfamethoxizole was added to anti-Pseudomonal antibiotics. The patient again required mechanical ventilation, but after a two-week course of antibiotics, the patient had defervescence and clearing of his chest radiograph and was eventually weaned off the ventilator to ultimately be discharged from the hospital.
Dr. Michael S. Niederman: Dr. Fein, can you describe how systemic sepsis may be complicated by ARDS? Dr. Alan M. Fein: Our patient exemplifies the close clinical relationship which ties severe infection to the adult respiratory distress syndrome (ARDS). The patient, a 59-year-old man with systemic lupus erythe-matosus and diabetes mellitus, who was receiving corticosteroids, presented with Gram-negative pneumonia which was uncontrolled by the prescribed antibiotics and he then developed septic ARDS. ARDS may be conceptualized as the pulmonary component of a generalized inflammatory injury, especially to the endothelium. When initiated by severe infection, it often progresses to involve in a sequential fashion other major organ systems, including kidneys, gastro-intestinal tract and liver leading to a syndrome of multisystem organ failure. ARDS may have both direct and indirect causes which often overlap. Pneumonia is the most common direct cause of the adult respiratory distress syndrome, particularly if it involves a large enough segment of parenchyma to severely impair the mechanical and gas exchange function of the lung. While viral pneumonia typically involves the lung parenchyma in a diffuse fashion, most other classes of organisms, including bacteria (most comonly), fungi and mycobacteria, also have this capability. Pneumocystis carinii has emerged as a common cause of severe hypoxic respiratory failure, usually in patients with AIDS. erectalis 20 mg
FIGURE 3. A second episode of pneumonia developed, with new infiltration in the left lung.
Infection may also initiate ARDS indirectly by activation of systemic inflammation. Bacteria, viruses, fungi, or even traumatized tissue induce a similar systemic response characterized by hypermetabolism (even in the absence of blood stream invasion) and subsequent multiorgan failure. The link between this systemic response, organ failure and infection is under complex and active investigation. Recent work has emphasized the central role of lymphocyte/mac- rophage-derived tumor necrosis factor (cachectin) and interleukin-1, in modulating the response to sepsis. Other potential mediators in this chain are activated neutrophils, complement and the various components of the thrombotic system, which may directly injure tissue and amplify inflammation. Dr. Niederman: It is possible to predict which septic patients will develop ARDS?
Dr. Fein: ARDS usually follows onset of the septic syndrome within 72 hours. While isolated bacteremia carries a relatively low risk for progressive lung injury (6-15 percent), when combined with shock and thrombocytopenia, the risk rises dramatically to 65 and 46 percent, respectively. Additional insults, such as hypertransfusion, aspiration or burns will increase the likelihood of sepsis leading to ARDS to approximately 50 percent. cialis soft tabs
At the present time, clinical signs in patients at risk are the best predictors of progressive lung injury. In a recent analysis combining injury severity score (ISS), individual risk factors and initial oxygenation, Pepe et al reported that ISS, numbers of transfusions, the presence of the septic syndrome and initial oxygenation best predicted ARDS, in that order. Our own data suggest that severity of presenting hypoxemia and metabolic acidosis are better predictors of pro-gression to ARDS in septic patients than are any measurements of mediators in serum.