Carcinoid tumors are slow-growing neoplasms arising from enterochromaffin cells. Because they originate from neuroendocrine cells, they are capable of secreting vasoactive substances, notably serotonin, kinin peptides, and histamine. If these substances reach the systemic circulation in sufficient quantity, they may produce the “carcinoid syndrome” which has important ramifications to the anesthesiologist.
The tumors arise from different embryonic divisions of the gut and their classification is based on the site of origin and histological characteristics. The sites are often the gastrointestinal tract (68%) and the bronchopulmonary system (25%). The amount of a metabolite of serotonin, 5-hydroxyindoleacetic acid (5-HIAA), in a 24-hour urine collection provides a measurement of the disease process. This test is highly specific, but has a sensitivity of 73%. Another marker of disease progression is the level of serum chromagraffin A. The 5-year survival of patients with no metastases is approximately 71%; however, this is reduced to 38% in those patients with metastases.
Only a small subset (10%) of patients with a carcinoid tumor will develop the carcinoid syndrome. This is explained by the ability of the liver to metabolize the tumor’s secreted vasoactive substances. Vasoactive substances secreted by tumors in the gut will pass through the liver via the hepatic portal vein and be metabolized before they can reach the systemic circulation. However, tumors arising in other locations, or those that originate in the liver (or liver metastases), can produce important systemic effects. The most frequent clinical features are cutaneous flushing and intestinal hypermotility (which may lead to dehydration and metabolic acidosis). Approximately 18% of patients with carcinoid syndrome may exhibit wheezing. Carcinoid heart disease occurs in about two-thirds of patients with carcinoid syndrome and is associated with perioperative complications. The right heart is typically affected and exhibits a thickened endocardium with mixed tricuspid and pulmonary valve disease. A severe manifestation of the syndrome, “carcinoid crisis,” is characterized by hemodynamic instability, bronchospasm, and profound flushing.
The two greatest areas of concern in the perioperative care of these patients are as follows:
Complications related to carcinoid heart disease
Potential for unpredictable vasoactive substance release
The severity of preoperative symptoms does not predict the severity of intraoperative complications. Likewise, the levels of 5-HIAA, although reflecting disease progression, do not reliably predict the incidence of intraoperative events.
A cardiovascular history and examination should focus on the possibility of the presence of right or biventricular heart failure. Signs and symptoms of reduced exercise tolerance, orthopnea, paroxysmal dyspnea, and peripheral edema should be investigated.
Excessive uncontrolled release of vasoactive substances may occur in response to anesthetic or surgical stimuli and hemodynamic variation. The possibility of either hypotension or hypertension exists, leading to hemodynamic instability. Importantly, hemodynamic collapse may be unresponsive to conventional therapy with inotropes and pressors. Indeed, catecholamine administration ...