____________ is a rare, slow growing neuroendocrine tumor originating in the cells of the neuroendocrine system.
Where do carcinoid tumors typically start?
in the lining of the digestive tract or in the lungs; they arise from enterochromaffin cells, which is a type of enteroendocrine cell distributed throughout the digestive tract (crypts of Liberkuhn)
What do carcinoid tumors secrete?
serotonin among other peptides (chromogranins, pacreatic polypeptide, 5 hydroxytryptophan (5-HTP), histamine)
Where is the location of approximately 90% of the body’s store of serotonin?
What is 5HT and its function?
serotonin: important in response to chemical, mechanical, or pathological stimuli in the lumen…. activates both parastaltic and secretory reflexes, and activates vagal afferents (5HT3) that signal the brain for generation of nausea
The majority of carcinoid tumors are found in what section of the body?
What is the midgut comprised of?
second portion of the duodenum, the jejunum, the ileum, and the right colon (produces high levels of serotonin, kinins, prostaglandins, substance P, and other vasoactive peptides)
What is the foregut comprised of?
anterior part of gut towards the mouth…. lungs, bronchus, stomach, proximal duodenum, and pancreas
What is the hindgut comprised of?
transverse colon, descending colon, and rectum… rarely causes carcinoid syndrome, asymptomatic (even when metastatic); rarely secrete 5-HT, 5HTP, or any other vasoactive peptides
The most common tumor of the midgut, accounting for 70% of cases), is in the _______.
What is kallikrein?
a precursor to bradykinin: which is one of the most potent vasodilators…. resulting in flushing
Why do manifestations of carcinoid syndrome usually not occur until there is metastasis to the liver? What about if located in bronchi?
b\c the biologically active products undergo liver metabolism….. if in bronchi it reaches systemic circulation before passing through hepatic metabolism
What is a diagnostic lab test for typical cases involving pulmonary carcinoid tumors?
presence of high levels of 5-HIAA in the urine; these tumors typically cause HIGH levels of serotonin and CgA in the blood
What are s\s of pulmonary carcinoid tumors?
cough or hemoptysis, recurrent PNA, occasional CP
Symptoms that occur secondary to carcinoid tumors are relatively uncommon (10%), but can result from endogenous secretion of mainly serotonin and kallikrein (precursor to bradykinin)…. these symptoms include?????
flushing, diarrhea (abdominal cramps d\t serotonin), Right HF (fibrosis of right sided valve cusps of both pulmonary and tricuspid valves… d\t high exposure of 5-hydroxytryptamine… which is 5HT or serotonin) much more common than LHF!!!! (bronchoconstriction is also pretty rare)
4 primary symptoms seen MOST frequently in carcinoid syndrome are???
flushing, diarrhea, cardiac, cramping
NOTE: a picture from the PPT presentation included the following symptoms of Carcinoid
vascular phenomena (flushing, cyanosis), bronchoconstriction, liver metastasis, hyperperistalsis, pulmonary and tricuspid valve heart disease, 5HT elevation in plasma, 5HIAA increased in urine, patchy hyperpigmentation, edema (right sided HF)
When do symptoms appear with carcinoid tumors?
approx 10%: become apparent when vasoactive substances from the tumors enter systemic circulation escaping hepatic degredation
What is a carcinoid crisis?
When ALL of the symptoms of carcinoid syndrome occur together: flushing, tachycardia, bronchospasm, and widely fluctuating BP (hypo/hypertension); potentially fatal
What are the most common causes of a carcinoid CRISIS?
anesthetic interventions; surgical intervention or radiological
What is the definitive way to localize a carcinoid tumor?
What is 5HIAA?
5HIAA is the end product of serotonin metabolism
What is an octreotide scan?
octreotide, a drug similar to somatostatin, is radiolabeled with indium 111 and injected into a vein and travels through the blood stream… radioactive octreotide attaches to tumor cells that have receptors for somatostatin… radiation measuring device outlines the location of the tumor
What is a good preop assessment finding that indicates cardiovascular involvement of the carcinoid tumor?
What is the pre-operative drug regime suggested prior to surgery for a carcinoid tumor?
minimize tumor activity before day of surgery with octreotide… octreotide infusion 50-100mcg/hr for at least 12 hours immediately before surgery
Why should you monitor glucose levels during the administration of octreotide?
b\c it reduces glucagon and insulin more than somatostatin (a natural hormone)
What is somatostatin?
an inhibitory peptide hormone (natural) that regulates the endocrine system….affects neurotransmission and cell proliferation…. it is secreted in the stomach, intestine, and delta cells of the pancreas…. decreases stomach acid production by preventing release of gastrin, secretin, and histamine…. inhibits secretion of growth hormone in the anterior pituitary gland… inhibits TSH release
What is the best VAA to use for carcinoid tumor cases? Why?
Isoflurane…. d\t low metabolic rate (liver mets)
Why should you avoid morphine and atracurium in carcinoid cases?
d\t histamine release
What is the best bolus treatment for HTN in carcinoid cases?
20-50mcg IV of octreotide… or labetolol infusion (alpha blockade) has been used for prolonged HTN
Why is octreotide used for management of a carcinoid tumor?
mimics inhibitory action of somatostatin…. inhibits release of serotonin, gastrin, vasoactive intestinal peptide, secretin, motilin, and pancreatic polypeptide
What are s\e of octreotide?
n/v, bradycardia, conduction defects, QT prolongation, and abdominal cramps
What is the SQ dosing of octreotide?