Organ-specific support in multiple organ failure: pulmonary support.
The catastrophic pulmonary failure that complicates management of patients with multiple trauma or sepsis syndrome with shock is recognizable to nearly all experienced surgeons. However, the spectrum of injury is broad, the distribution of lung injury may be heterogeneous within a single patient, and many patients will not develop acute respiratory distress syndrome (ARDS) even after a major predisposing insult. The lung responds stereotypically to many disparate insults, so a better conceptual construct of ARDS may be to consider it as one component of the multiple organ dysfunction syndrome. Support of oxygen transport with positive pressure ventilation and high levels of positive end-expiratory pressure, long the mainstay of pulmonary support, has been criticized for its predilection to cause barotrauma. Newer modes of ventilation, such as pressure-controlled, inverse-ratio ventilation and permissive hypercapnia, are under investigation but have not yet been reported with scientific rigor. However, pulmonary support extends beyond the support of gas exchange. Fluid management requires close attention so that the circulation is supported but lung water accumulation is minimized. Nosocomial pneumonia greatly increases the mortality rate in ARDS, but is difficult to diagnose and must be sought aggressively. Until recently, pharmacologic therapy has held little promise, but inhalation of very low concentrations of nitric oxide appear to decrease pulmonary vascular pressures and intrapulmonary shunt. It remains unknown whether nitric oxide is effective therapy for the underlying injury, or is simply treatment for certain manifestations.