All patients with significant chest pain, dyspnea, or tachypnea should receive cardiac monitoring, intravenous access, and supplemental oxygen while their evaluation proceeds. Failure to correct hypoxemia with supplemental oxygen may necessitate endotracheal intubation in order to provide a higher F iO2 directly. Shock in the absence of pulmonary edema should be treated with aggressive intravenous administration of crystalloid. If vasopressors are required, dopamine is considered the drug of choice in PE.
Stable patients with PE are treated with anticoagulant (AC) therapy. After obtaining baseline coagulation studies, intravenous heparin is administered first as a bolus
(either 5000 U or 80 U/kg) and then as a constant infusion (1280 U/h or 18 U/kg per hour). Dosing of heparin based on the patient's weight is preferred, as it is less likely to produce subtherapeutic levels. The activated partial thromboplastin time (aPTT) is measured every 6 h, altering the heparin infusion, until a stable aPTT of 50 to 90 s is achieved; it is then checked daily. After 24 h of heparin, oral warfarin is begun at 5 to 10 mg/day and the prothrombin time (PT) is checked daily. Warfarin administration is best delayed owing to an initial hypercoagulability effect of reducing protein before reduced prothrombin levels are achieved. The dose is adjusted until PT measurements show a stable International Normalized Ratio (INR) of between 2 and 3 (or PT of 1.5 to 2.5 times control). Heparin and warfarin therapy should overlap for at least 4 days. Patients should continue warfarin therapy for at least 3 months, with monitoring of the PT. Low-molecular-weight heparin (LMWH) has been shown to be as safe and effective as unfractionated heparin,23 allows for twice daily subcutaneous administration, and precludes the need for aPTT measurements. For these reasons many consider LMWH preferable in the treatment of DVT and PE. Chapteri216 discusses the major complication of AC therapy and their treatment.
Thrombolytic therapy is used in patients with massive PE associated with refractory hypoxemia or circulatory collapse. It should also be considered for patients with moderate to severe right ventricular dysfunction, since they may progress to circulatory collapse. Urokinase (4400 U/kg load followed by 4400 U/kg per hour by infusion for 12 to 24 h), streptokinase (250,000 U load followed by 100,000 U/h infusion for 24 h) and recombinant tissue plasminogen activator (r-tPA) at 100 mg over 2 h have all been shown to be effective in normalizing pulmonary artery pressures, improving right ventricular function, correcting hypoxemia, and improving systemic hemodynamics. However, r-tPA has been shown to be fastest in improving these parameters. Beneficial effects may be seen with thrombolytic therapy up to 2 weeks after the PE is activated, although the effects are greatest early in the course of the disease. 24 Therapy with heparin and warfarin is begun after the thrombolytic infusion is completed. Intrapulmonary artery infusion is no more effective than peripheral intravenous administration, and the risk of bleeding at the site of pulmonary artery catheter placement is high. The use of thrombolytics has largely replaced embolectomy in unstable patients.
Septic emboli, whether from indwelling central venous catheters or associated with IDU, represent a diagnostic and therapeutic challenge. Septic DVT requires not only appropriate AC therapy but also antibacterial or antifungal treatment. Removal or drainage of septic foci, whether due to an intravenous catheter or an abscess cavity, must be accomplished. In some circumstances surgical removal of an infected vein segment is required. AC therapy of septic PE from right-sided endocarditis is controversial, since heparin administration in endocarditis is associated with a higher incidence of intracranial hemorrhage.
Patients with recurrent PE despite adequate AC therapy or those with contraindications to AC therapy may require interruption of the inferior vena cava. Transvenous placement of a Greenfield (umbrella) filter is most commonly used for this.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.