PULMONARY EMBOLISM   11A

A 57-year-old man has a right total knee replacement for severe degenerative joint disease. Four days later, he develops shortness of breath and right-sided pleuritic chest pain.

He is in moderate respiratory distress with respiratory rate 28 breaths per minute, heart rate 120 beats per minute, blood pressure 110/70 mm Hg, and oxygen saturation 88% on room air. Cardiopulmonary examination is normal. The right leg is postsurgical, healing well, with 2+ pitting edema, calf tenderness, erythema, and warmth; his left leg is normal.

What are the salient features of this patient’s problem? How do you think through his problem?

Salient features: Recent surgery; acute dyspnea; pleuritic chest pain; tachypnea and tachycardia; hypoxia (oxygen desaturation); signs of deep venous thrombosis (DVT) including unilateral calf tenderness and edema.

How to think through: This patient has sudden onset of dyspnea, chest pain, tachypnea, hypoxemia, and tachycardia. What is the differential diagnosis of this scenario? (Myocardial infarction, pneumothorax, cardiac tamponade, pulmonary embolism [PE].) What features make PE more likely? (Pleuritic quality of chest pain, normal cardiopulmonary examinations, post-surgical onset.) What are immediate management and diagnostic priorities in this unstable patient? (Supplemental oxygen, intravenous access; electrocardiogram [ECG], chest radiography.) If ECG shows only sinus tachycardia and chest radiography shows only clear lung fields, how should the possibility of PE be evaluated? (Helical CT scan.) Is there a role for a D-dimer test? (No.) This test is best used for an “intermediate-probability,” rather than this “high-probability,” scenario. His CT scan shows extensive bilateral pulmonary emboli. How do you decide if this is a “massive” or “submassive” PE? (“Massive PE” indicates hemodynamic compromise [cardiogenic shock] and is treated by thrombolysis; in “submassive” PE, the role of thrombolysis is less clear.) In this case, given that his blood pressure is likely below baseline, but he is not in shock, how might you better assess right heart strain? (Echocardiogram.) What treatment should you initiate regardless of the thrombolysis decision? (Heparin or low-molecular weight heparin [LMWH].) Is a workup for thrombophilia indicated? (No. Surgery and stasis more likely “provoked” his PE than did a thrombophilia.) What is the typical duration of anticoagulation for “provoked” venous thromboembolism (VTE)? (6 months).

PULMONARY EMBOLISM   11B

What are the essentials of diagnosis and general considerations regarding pulmonary embolism?

Essentials of Diagnosis

Predisposition to venous thrombosis, usually of the lower extremities

Usually dyspnea, chest pain, hemoptysis, or syncope

Tachypnea and a widened alveolar–arterial PO₂ difference

Characteristic defects on ventilation/perfusion lung scan, helical CT scan of the chest, or pulmonary angiography

General Considerations

Third most common cause of death in hospitalized patients; often not recognized antemortem

Risk factors: immobility, hyperviscosity, increased central venous pressures, vessel damage (trauma, prior DVT, orthopedic surgery), hypercoagulable states

PE develops in 50% to 60% of patients with proximal lower extremity DVT; 50% are asymptomatic; hypoxemia results from vascular obstruction leading to dead space ventilation, right-to-left shunting, and decreased cardiac output

Other types of pulmonary emboli: fat embolism, air embolism, amniotic fluid embolism, septic embolism (e.g., endocarditis), tumor embolism, foreign body embolism, and parasite egg embolism (schistosomiasis)

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