Thromboembolic Complications

Case Synopsis

A 53-year-old man underwent posterior spinal fusion with instrumentation, involving segments L1–L4. His past medical history included protein S deficiency, for which he received warfarin therapy. He discontinued his warfarin therapy 2 weeks before surgery without telling his health care providers. His uneventful surgery lasted 8 hours. One hour postoperatively he became tachypneic, his blood pressure dropped from 130/80 to 88/50 mm Hg, and his oxyhemoglobin saturation dropped from 99% to 88%. Acute pulmonary embolus was diagnosed.

Problem Analysis

Thromboembolic events, being some of the most feared complications of the perioperative period, represent the most common cause of in-hospital mortality. They are often life threatening (pulmonary embolus), limb threatening (peripheral arterial embolus), or of great danger to the central nervous system (cerebrovascular embolus). Anesthesiologists, as leaders in the perioperative surgical home, are expanding their role in the perioperative period. They are increasingly relied on to prevent and treat complications such as thromboembolism.

Definition

Thromboembolism is a spectrum of vascular occlusive disorders involving intravascular blood coagulation. Thrombosis refers to the formation of clot, and embolism the dissemination of clot or other substances to parts of the vascular tree. In addition to clot, substances such as intravascular gas and bone marrow can result in embolus ( Table 183.1 ). The venous or arterial sides of the circulation may be involved, including the cerebral vasculature, chambers of the heart, coronary arteries, and pulmonary arteries ( Table 183.2 ). The focus of this chapter is on two manifestations of venous thromboembolism (VTE): deep venous thrombosis (DVT) and pulmonary embolus (PE).

TABLE 183.1

Sources of Embolus

Embolism Source	Clinical Scenarios
Venous thrombus	Deep venous thrombosis, immobility, hypercoagulable state
Air	Surgery in the sitting position; back surgery with surgical site elevated above the level of the heart; accidental air in venous infusion; open chamber cardiac surgery; accidental entrainment in coronary artery during coronary surgery
Carbon dioxide (CO ₂ )	Gas embolus during laparoscopic surgery; open chamber cardiac surgery in which CO ₂ is used
Oxygen	Orthopedic use of hydrogen peroxide as irrigant in long bone surgery
Catheters, catheter fragments, guidewires, guidewire fragments	Complications of vascular access attempts
Septic embolus	Prolonged infection (catheter site, endocarditis, abscess)
Tumor embolus	Renal cell carcinoma, cardiac chamber tumor
Fat embolus	Long bone fracture, surgery

TABLE 183.2

Selected Thromboembolic Phenomena and Their Clinical Manifestations

Site	Predisposing Factors	Clinical Consequences and Sequelae
Deep venous thrombosis	Venous stasis	Pulmonary embolus, inferior vena cava thrombosis, superior vena cava syndrome
Pulmonary embolus	Deep venous thrombosis, hypercoagulable state	Shock, death, residual pulmonary hypertension
Peripheral arterial thrombosis or embolus	Atrial or ventricular septal defect, thoracic aortic or peripheral arterial surgery	Organ, limb ischemia or infarction
Cerebral artery thrombosis or embolus	Arterial atherosclerosis, atrial or ventricular septal defect, surgery involving the carotid artery or aortic arch	Stroke
Coronary artery thrombosis	Coronary stent, withdrawn from antiplatelet agents, severe coronary artery disease	Sudden myocardial infarction
Coronary artery embolus	Arterial atherosclerosis, atrial or ventricular septal defect, surgery involving the aortic arch	Myocardial ischemia or infarction
Cardiac chamber thrombosis	Atrial fibrillation, heart failure	Arterial embolus

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