Chapter 26 ICU Infections

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SECTION II • Medical and Surgical Crises

is required and viral antimicrobials should be con- sidered. For example, acyclovir (varicella), riman- tadine (influenza), and ribavirin (adenovirus) each offer modest benefit when used in timely fashion in well-selected cases. Perhaps the most important aspect in the management of these pneumonias is to take appropriate measures to prevent the spread of these contagious diseases to health care workers and to the patients they treat. The importance of such precautions was dramatically emphasized in the high incidence of illness among physicians dur- ing the SARS outbreak of 2003. When an appro- priate vaccine is available for a contagious disease (e.g., influenza), immunization of exposed individu- als is prudent. Empyema and Parapneumonic Effusions Definition Small amounts of pleural fluid routinely accu- mulate adjacent to pneumonias, and such collec- tions are termed “parapneumonic effusions.” Most parapneumonic effusions are intermediate or even transudative in nature (protein <3.5 g/dL or 50% of the serum level; LDH < 200 U/dL or 60% of the serum level), freely flowing, and self-limited. The term “complicated parapneumonic effusion” has been applied to effusion with loculations, the characteristics of which fall somewhere between

an uncomplicated, self-resolving parapneumonic effusion and an empyema. Usually exudative by protein and LDH criteria, leukocyte counts usually are less than 20,000/mm 3 , and glucose levels fall between the serum value and 20 mg/dL. The pH of such effusions is commonly regarded as a discrimi- nator of the need for drainage, but its discriminat- ing value is often limited. Although it is true that the lower the pH, the more likely a pleural effusion is to have characteristics of an empyema (see fol- lowing), the pH alone neither makes the diagnosis of an empyema nor dictates a particular course of action. Effusions with a pH less than 7.0 (with a normal arterial pH) are likely to be empyemas and are likely to require drainage by tube thoracostomy, but such associations are not always valid. An acidic, thin, clear, or slightly cloudy sterile fluid does not necessarily require tube thoracostomy, whereas a thick, viscous, protein- and leukocyte-rich effusion would require thoracostomy, regardless of fluid pH. As a general rule, freely flowing effusions that separate the lung from the chest wall by more than 1 cm on a lateral decubitus film, those that are loculated, and those that do not flow freely, should be sampled and/or drained (Fig. 26-3). The exis- tence of parietal pleural thickening documented on a contrast-enhanced CT scan suggests an intense inflammatory response and probable empyema. The ease and safety of thoracentesis in the ICU

A B FIGURE 26-3. Ultrasonic (A) and CT (B) images of complicated pleural effusion and empyema. Though less precise than CT, bedside ultrasound is convenient and may be definitive. Both are helpful prior to interventional procedures such as chest tube placement.