CHAPTER 39

#### KEY POINTS

• Pulmonary embolism (PE) is common and potentially lethal, yet readily treatable.

• Prophylaxis and accurate diagnosis are essential to improving outcome.

• The cause of death in PE is most often circulatory failure (acute cor pulmonale) due to right heart ischemia.

• There is no perfect diagnostic test for PE; accurate diagnosis requires both an informed clinical pretest probability and a stepwise application of helical CT angiography and/or LE duplex.

• A careful risk assessment may identify patients ideal for outpatient therapy. Conversely, patients with hypotension or right ventricular strain are at significantly higher risk for death from PE, and warrant ICU admission.

• While low-molecular-weight heparin (LMWH) is approved and recommended as the initial therapy for PE, critically ill patients often have reason for a shorter-acting medication. Unfractionated heparin is typically used to maintain the partial thromboplastin time (PTT) at 1.5 to 2.5 times control.

• Thrombolytic therapy is lifesaving and possibly in those with isolated RV dysfunction in patients with massive embolism and circulatory instability, but does not seem beneficial in patients without shock.

• Air and fat embolism usually present as acute respiratory distress syndrome (ARDS), and are managed with mechanical ventilation, oxygen, and positive end-expiratory pressure (PEEP).

This chapter covers diseases involving embolism to the pulmonary circulation, including pulmonary thromboembolism, as well as the less common conditions of venous air embolism and fat embolism. Thromboembolism is predominantly an acute circulatory insult, with important but less dramatic consequences for gas exchange. In contrast, both air and fat embolism usually present as acute hypoxemic respiratory failure (AHRF). All three of these forms of embolism may cause acute right heart failure, more fully discussed in Chap. 38.

#### PULMONARY THROMBOEMBOLISM: EPIDEMIOLOGY IN THE ICU

PE is a dramatic and life-threatening complication of underlying deep venous thrombosis (DVT). Therefore, much of the management of PE is grounded in the prophylaxis, diagnosis, and treatment of DVT. While extensive prospective data regarding the diagnosis and treatment of PE are available, the vast majority of patients in such trials have not been critically ill, and thus the treatment for ICU patients with thromboembolic disease relies on extrapolation, and may lack the strength of evidence now available for most patients with PE or DVT. Nonetheless, important distinctions exist between the critically ill and noncritically ill patient populations when considering PE diagnosis and treatment.

Pulmonary thromboembolism is a common illness, which accounts for substantial morbidity and mortality. Interesting trends have been recently reported regarding the incidence of PE. Historically, acute PE was believed to be frequently underdiagnosed, and a frequent cause of unexplained sudden death, as it was estimated that up to 25% of patients may die before admission.1 However, a recent time-trend analysis using an administrative database demonstrated a dramatic increase in PE incidence in the United States, from approximately 62 cases per 100,000 population to over 113 cases per 100,000.2 This change in the incidence of ...

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