Serotonin pathway in carcinoid syndrome: Clinical, diagnostic, prognostic and therapeutic implications

Carcinoid syndrome represents the most common functional syndrome that affects patients with neuroendocrine neoplasms. Its clinical presentation is really heterogeneous, ranging from mild and often misdiagnosed symptoms to severe manifestations, that significantly worsen the patient's quality of life, such as difficult-to-control diarrhoea and fibrotic complications. Serotonin pathway alteration plays a central role in the pathophysiology of carcinoid syndrome, accounting for most clinical manifestations and providing diagnostic tools. Serotonin pathway is complex, resulting in production of biologically active molecules such as serotonin and melatonin, as well as of different intermediate molecules and final metabolites. These activities require site- and tissue-specific catalytic enzymes. Variable expression and activities of these enzymes result in different clinical pictures, according to primary site of origin of the tumour. At the same time, the biochemical diagnosis of carcinoid syndrome could be difficult even in case of typical symptoms. Therefore, the accuracy of the diagnostic methods of assessment should be improved, also attenuating the impact of confounding factors and maybe considering new serotonin precursors or metabolites as diagnostic markers. Finally, the prognostic role of serotonin markers has been only evaluated for its metabolite 5-hydroxyindole acetic acid but, due to heterogeneous and biased study designs, no definitive conclusions have been achieved. The most recent progress is represented by the new therapeutic agent telotristat, an inhibitor of the enzyme tryptophan hydroxylase, which blocks the conversion of tryptophan in 5-hydroxy-tryptophan. The present review investigates the clinical significance of serotonin pathway in carcinoid syndrome, considering its role in the pathogenesis, diagnosis, prognosis and therapy.

Long-Term Safety Experience with Telotristat Ethyl Across Five Clinical Studies in Patients with Carcinoid Syndrome

BACKGROUND

Patients with neuroendocrine tumors (NETs) and carcinoid syndrome experience considerable morbidity and mortality; carcinoid syndrome may be associated with shorter survival. Carcinoid syndrome is linked to tumoral secretion of serotonin and other bioactive substances. The subsequent debilitating diarrhea and urgency to defecate pose significant health risks. In previous studies, telotristat ethyl, a tryptophan hydroxylase inhibitor, was effective and well tolerated in treating carcinoid syndrome diarrhea. We present pooled safety data from five clinical trials with telotristat ethyl in patients with carcinoid syndrome.

SUBJECTS, MATERIALS, AND METHODS

Adverse events reported during telotristat ethyl treatment were pooled from two phase II and three phase III clinical trials in 239 patients with carcinoid syndrome. Long-term safety of telotristat ethyl and causes of hospitalization and death were reviewed; overall survival was estimated.

RESULTS

Mean (median; range) duration of exposure and follow-up was 1.3 years (1.1 years; 1 week to 5.7 years), with 309 total patient-years of exposure. Leading causes of hospitalization were gastrointestinal disorders or were related to the underlying tumor and related treatment. Survival estimates at 1, 2, and 3 years were 93%, 88%, and 77%. Nearly all deaths were due to progression or complication of the underlying disease; none were attributable to telotristat ethyl. There was one death in year 4.

CONCLUSION

Based on long-term safety data, telotristat ethyl is well tolerated and has a favorable long-term safety profile in patients with carcinoid syndrome.

IMPLICATIONS FOR PRACTICE

Carcinoid syndrome can cause persistent diarrhea, even in patients treated with somatostatin analogs. Across five clinical trials in patients with carcinoid syndrome, telotristat ethyl has been well tolerated and efficacious, providing clinicians with a new approach to help control carcinoid syndrome diarrhea, in addition to somatostatin analog therapy. By reducing the stool frequency in patients with carcinoid syndrome whose diarrhea is refractory to anticholinergics, such as loperamide and atropine/diphenoxylate, and somatostatin analog dose escalation, improvement in quality of life becomes an achievable goal.

Cases in a series of carcinoid syndrome and carcinoid heart disease

Although carcinoid syndrome is regarded as a rare entity, carcinoid patients with evidence of cardiac involvement show a markedly reduced survival time. Patients with advanced signs of right-sided heart failure represent a subgroup at particularly high risk. Echocardiography remains the gold standard to diagnose or confirm structural cardiac involvement in patients with underlying carcinoid disease. This is the notion that propelled us to report on cases of carcinoid syndrome with cardiac involvement. We also review carcinoid syndrome and carcinoid heart disease, and challenges regarding the diagnosis and management of carcinoid heart disease.

A prospective study of the pathophysiology of carcinoid crisis

BACKGROUND

Sudden massive release of serotonin, histamine, kallikrein, and bradykinin is postulated to cause an intraoperative carcinoid crisis. The exact roles of each of these possible agents, however, remain unknown. Optimal treatment will require an improved understanding of the pathophysiology of the carcinoid crisis.

METHODS

Carcinoid patients with liver metastases undergoing elective abdominal operations were studied prospectively, using intraoperative, transesophageal echocardiography, pulmonary artery catheterization, and intraoperative blood collection. Serotonin, histamine, kallikrein, and bradykinin levels were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Of 46 patients studied, 16 had intraoperative hypotensive crises. Preincision serotonin levels were greater in patients who had crises (1,064 vs 453 ng/mL, P = .0064). Preincision hormone profiles were otherwise diverse. Cardiac function on transesophageal echocardiography during the crisis was normal, but intracardiac hypovolemia was observed consistently. Pulmonary artery pressure decreased during crises (P = .025). Linear regression of preincision serotonin levels showed a positive relationship with mid-crisis cardiac index (r = 0.73, P = .017) and a negative relationship with systemic vascular resistance (r=-0.61, P = .015). There were no statistically significant increases of serotonin, histamine, kallikrein, or bradykinin levels during the crises.

CONCLUSION

The pathophysiology of carcinoid crisis appears consistent with distributive shock. Hormonal secretion from carcinoid tumors varies widely, but increased preincision serotonin levels correlate with crises and with hemodynamic parameters during the crises. Statistically significant increases of serotonin, histamine, kallikrein, or bradykinin during the crises were not observed.

Carcinoid syndrome: update on the pathophysiology and treatment

Approximately 30-40% of patients with well-differentiated neuroendocrine tumors present with carcinoid syndrome, which is a paraneoplastic syndrome associated with the secretion of several humoral factors. Carcinoid syndrome significantly and negatively affects patients' quality of life; increases costs compared with the costs of nonfunctioning neuroendocrine tumors; and results in changes in patients' lifestyle, such as diet, work, physical activity and social life. For several decades, patients with neuroendocrine tumors and carcinoid syndrome have been treated with somatostatin analogues as the first-line treatment. While these agents provide significant relief from carcinoid syndrome symptoms, there is inevitable clinical progression, and new therapeutic interventions are needed. More than 40 substances have been identified as being potentially related to carcinoid syndrome; however, their individual contributions in triggering different carcinoid symptoms or complications, such as carcinoid heart disease, remain unclear. These substances include serotonin (5-HT), which appears to be the primary marker associated with the syndrome, as well as histamine, kallikrein, prostaglandins, and tachykinins. Given the complexity involving the origin, diagnosis and management of patients with carcinoid syndrome, we have undertaken a comprehensive review to update information about the pathophysiology, diagnostic tools and treatment sequence of this syndrome, which currently comprises a multidisciplinary approach.

Carcinoid crisis 24 hours after bland embolization: A case report

Within 24 h of bland embolization of carcinoid liver metastasis, patient developed flushing and severe hypotension consistent with carcinoid crisis. Octreotide pre- and post-procedure remains the mainstay for prevention and treatment of carcinoid crisis.

Carcinoid heart disease

Carcinoid heart disease is a rare form of valvular heart disease. The management of these patients is complex, as the systemic malignant disease and the cardiac involvement have to be considered at the same time. Progress in the treatment of patients with carcinoid disease has resulted in improved symptom control and survival. Development and progression of carcinoid heart disease are associated with increased morbidity and mortality. In patients with severe cardiac involvement and well-controlled systemic disease, cardiac surgery has been recognized as the only effective treatment option. Valve replacement surgery may not only be beneficial in terms of symptom relief, but may also contribute to the improved survival observed over the past 2 decades in patients with carcinoid heart disease. Early diagnosis and early surgical treatment in appropriately selected patients may provide the best results. In this article, we review the current literature regarding the biology, diagnosis, treatment, and prognosis of carcinoid heart disease.

Antisecretory factor counteracts secretory diarrhoea of endocrine origin

BACKGROUND

Dietary induction of antisecretory factor (AF) can reduce diarrhoea in patients with inflammatory bowel disease. Patients with neuroendocrine tumours may suffer from diarrhoea with a prominent secretory component. We studied if AF-therapy could affect this type of diarrhoea.

METHODS

Six patients with the midgut carcinoid syndrome and two with metastasizing medullary thyroid carcinoma (MTC) participated. Effects of intake of AF, in the form of AF-rich egg powder (AF-egg), and induction of endogenous AF-activity by intake of specially processed cereals (SPCs) were studied. In an initial open part of the study all patients received AF-egg for 4 weeks, followed by a double-blind crossover period with SPC and control cereals (CCs) for 6 weeks each. Daily number of bowel movements at the end of each treatment period was registered.

RESULTS

Treatment with AF-egg resulted in a decrease of bowel movements in seven patients (P<0.01). Registrations of bowel movements from both SPC and CC diet periods were obtained from five patients. The daily number of bowel movements was lower during the SPC-period compared to the period with CC (P<0.05). All patients had low levels of AF-activity in serum at baseline. During treatment with AF-egg, the mean level increased slightly. AF-activity was higher (P<0.05) after SPC compared to the CC diet.

CONCLUSIONS

In a group of patients with endocrine diarrhoea, AF-activity could be induced, and AF-therapy reduced the number of bowel movements.

Epidemiology, clinical features and diagnosis of gastroenteropancreatic endocrine tumours

Gastroenteropancreatic (GEP) neoplasms originate from any of the various cell types belonging to the neuroendocrine system. A general characteristic of GEP endocrine tumours is that the vast majority produce and secrete a multitude of peptide hormones and amines. Many patients with malignant metastasising tumours present clinical symptoms related to hormone hyperproduction. These include the so-called carcinoid syndrome, characterised by flushing, diarrhoea, wheezing and right heart disease, which is predominantly associated with the serotonin- and tachykinins-producing carcinoids of the midgut. Several types of syndrome associated with GEP endocrine tumors are caused by overproduction of a specific hormone. For instance, the well-known Zollinger-Ellison syndrome is gastrin-mediated. The so-called 'insulinoma syndrome' depends on excessive production of insulin and proinsulin, resulting in hypoglycemia. The 'glucagonoma syndrome' is characterised by necrolytic migratory erythema, diabetes and diarrhoea. The Verner-Morrison syndrome, which is brought about by high circulating levels of vasointestinal peptide (VIP). produces severe secretory diarrhoea. Finally the 'somatostatinoma syndrome' involves gallbladder dysfunction and gallstones, diarrhoea with or without steatorrhea, and impaired glucose tolerance. The biochemical diagnosis of endocrine digestive tumors is based on general and specific markers. The best general markers are chromogranin A (CgA) and pancreatic polypeptide (PP). Specific markers for endocrine tumors include insulin, gastrin, glucagon, vaso intestinal polypeptide (VIP), somatostatin and the primary cathabolic product of serotonin, 5-hydroxyndoleacetic acid (5-HIAA). Localisation procedures commonly applied, in the diagnosis of endocrine tumours include ultrasound (US), computed tomography (CT) and somatostatin receptor scintigraphy (SRS).

The carcinoid syndrome: an unusual cause of valvular heart disease

A 30-year-old woman presented to the Emergency Department with complaints of shortness of breath, orthopnea, and a severe reduction in exercise tolerance. The symptoms were the result of severe valvular heart disease that resulted from a bronchopulmonary carcinoid tumor. The carcinoid syndrome is a distinctive clinical syndrome seen in patients with carcinoid tumors. Cardiac valvular lesions are seen in the majority of patients with the carcinoid syndrome and represent the most clinically significant consequence of the carcinoid syndrome. This case report discusses carcinoid tumors, the carcinoid syndrome induced by these tumors, and the therapeutic options in the management of carcinoid tumors.

Severe intrapulmonary shunting associated with metastatic carcinoid

A 37-year-old woman with a 10-year history of metastatic carcinoid presented to her oncologist with increased dyspnea. Further evaluation revealed hypoxemia and intrapulmonary vasodilatation. We describe a case of hepatopulmonary-like physiology associated with metastatic carcinoid in a patient with intact liver function. To our knowledge, this is the first documented case of intrapulmonary shunting and hepatopulmonary-like physiology associated with metastatic carcinoid.

Anesthesia for patients with carcinoid syndrome

Carcinoid syndrome, although rare, can create serious problems to the anesthetist, both by the nature and variability of clinical manifestations and by the complications that can occur peroperatively. Recent research has led to a better understanding of the pathophysiology of the disease process. However, modern medicine is far from unraveling the precise nature and physiological effects of all the peptide mediators produced by these tumors. The severity of symptoms does not predict the severity of perioperative complications, so that patients with minor preoperative symptoms may have significant intraoperative complications. While urinary 5-HIAA levels provide a good indicator of disease progression, they cannot predict the degree or type of physiological response to intraoperative tumor manipulation. Indeed, urinary 5-HIAA may be normal both in the presence of a clinical diagnosis of carcinoid syndrome and in the face of a peroperative carcinoid crisis. The keys to successful anesthetic management of patients with carcinoid syndrome are good communication between endocrinologist, anesthetist, and surgeon and preoperative optimization of the patient. This includes appropriate investigation and treatment of the effects of carcinoid peptides and the prevention of their release from tumors. If possible, advice should be sought from centers with experience at managing this group of patients. Octreotide has largely replaced the use of other drugs both for symptomatic control and acute treatment of the symptoms associated with carcinoid syndrome. However, other drugs, such as aprotinin, still have a significant place in the symptomatic control and treatment of peroperative complications, as serotonin is only one of a large variety of peptides responsible for the clinical effects of this disease. Anesthetic technique should be aimed at minimizing carcinoid mediator release, in response to stress it induction of anesthesia and tracheal intubation and during tumor manipulation. It is equally important to prepare for carcinoid crisis by, for example, ordering drugs, which are otherwise uncommonly used in the theater setting, ahead of time. Cardiovascular instability, particularly hypotension, is common, so that full monitoring and vigilance is vital to predict its onset. The current surgical view of management is that, while curative resection of carcinoid tumors less than 2 cm in diameter with no evidence of invasion or metastatic spread is appropriate, patients with disseminated disease should be medically managed unless symptom control is poor. The exceptions to this are those patients with early and correctable carcinoid cardiac disease and those who require palliative procedures such as defunctioning obstructed bowel. Survival rates in patients following excision of gastric and appendical carcinoid tumors approach those of the general population as a whole and the chance of metastasis is extremely low. Only two series have been published in the anesthetic literature on anesthesia for patients with carcinoid syndrome, although there are many single-case reports. Despite the rarity of this syndrome, further formal studies into the anesthetic management of this condition should be encouraged.

Relation between fat malabsorption and transit abnormalities in human carcinoid diarrhea

BACKGROUND & AIMS

Fat and complex carbohydrates in the distal bowel activate "brakes" inhibiting upper gut motility. The hypothesis of this study was that rapid transit carcinoid diarrhea in association with steatorrhea results in impairment of gastric emptying.

METHODS

Fifteen patients with carcinoid diarrhea without prior gastrointestinal resection or whose small bowel resection was limited to < 100 cm of ileum were studied. Gastrointestinal transit was measured scintigraphically with a standardized meal. Percentage of ingested fat excretion was calculated.

RESULTS

Mean length of small bowel resected was 33 cm, and mean 24-hour urine 5-hydroxyindoleacetic acid was 120 mg. Fourteen patients had increased daily stool weights, and 10 had increased stool fat excretion (mean, 13%). Transit was accelerated in the small bowel in 14 and in the colon in all patients. The lag time for gastric emptying was prolonged in 2 patients who had no previous resection. Gastric emptying rate was accelerated in 5, normal in 7, and delayed in 3 patients.

CONCLUSIONS

Ileal and colonic brakes do not seem to delay gastric emptying in patients with carcinoid diarrhea associated with rapid transit and mild to moderate steatorrhea.

Octreotide treatment of carcinoid hypertensive crisis

In the severe crisis of carcinoid syndrome the flush is usually accompanied by hypotension and occasionally shock. Injection of octreotide, the long-acting analog of somatostatin, usually prevents or aborts this vasomotor reaction. A small minority of carcinoid syndrome patients manifest hypertension during their crises and little has been reported in the literature on their management. We present the first case reports of the response of patients with hypertensive carcinoid crisis to treatment with octreotide. The world literature contains reports of 20 prior cases of hypertensive carcinoid crises occurring in association with the stress of surgery and anesthesia. Review of these cases reveals no common feature, other than hypertension, that might clearly distinguish them from the typical hypotensive carcinoid syndrome patient. It is hypothesized that the mechanism of action of octreotide correcting the blood pressure changes in all carcinoid crises is via its known inhibition of vasomotor product release from the tumor and blocking receptors for these substances. We suggest that hypertensive as well as hypotensive carcinoid crises respond to octreotide and that this agent should be considered for prophylactic and emergency use in all carcinoid syndrome patients prior to and during anesthesia and surgery.

Pathophysiological causes and clinical significance of flushing

Flushing is a common and important symptom, resulting from changes in cutaneous blood flow. It occurs as part of a number of endocrine syndromes, and may be caused pharmacologically. Effective management depends on accurate diagnosis and understanding of the mechanisms involved.

Motor dysfunction of the small bowel and colon in patients with the carcinoid syndrome and diarrhea

BACKGROUND AND METHODS

The pathophysiology of diarrhea in patients with the carcinoid syndrome is not understood. Possible causes include tumor production of neurohumoral substances, such as serotonin and substance P, which stimulate small-bowel and colonic motility, and intestinal abnormalities, such as lymphangiectasia and bacterial overgrowth. We undertook this study to determine whether carcinoid diarrhea is associated with abnormal motor function in the small intestine and colon. We measured the gastric, small-bowel, and colonic transit of radiolabeled solid residue and estimated the volume of the ascending colon in 16 patients with the carcinoid syndrome and diarrhea and 16 normal subjects. We also measured colonic tone and phasic pressure activity by intracolonic multilumen manometry and with an electronic barostat in seven patients and six normal subjects.

RESULTS

The patients with the carcinoid syndrome had elevated 24-hour urinary excretion of 5-hydroxyindoleacetic acid and elevated fasting plasma serotonin concentrations. Transit times in the small bowel and colon were two times (P < 0.001) and six times (P = 0.001) faster in the patients than in the normal subjects. The volume of the ascending colon was approximately 50 percent smaller in the patients than in the normal subjects (P < 0.001). The patients had normal fasting colonic tone; their mean postprandial colonic tone was markedly increased as compared with the values in the normal subjects (mean increase, 41 percent vs. 24 percent; P = 0.03).

CONCLUSIONS

Patients with the carcinoid syndrome who have diarrhea have major alterations in gut motor function that affect both the small intestine and colon.

Abnormalities of the interdigestive migrating motor complex in a patient with carcinoid syndrome

Intraluminal pressures of the gastric antrum, duodenum and jejunum were recorded for 206 min after a 12 h fast in a patient with carcinoid syndrome due to neoplasia of enterochromaffin cells of the ileum and with hepatic metastases. The most conspicuous alteration was a tachyrrhythmia of 16 waves/min predominating in the activity fronts of both duodenum and jejunum. Periods of 11-12 waves/min frequency appeared irregularly and the simultaneous occurrence of frequencies of 11 waves/min and 16 waves/min was also recorded. The gastric antrum was fully quiescent throughout the study. The alterations observed are presumed to be produced by substances secreted by the carcinoid tumor.

Carcinoid syndrome and serotonin: therapeutic effects of ketanserin

The carcinoid syndrome can arise when effluent blood from carcinoid tumor tissue gains access to the systemic, as opposed to the portal, venous system. Features include facial flushing, diarrhea, wheezing, right-sided cardiac lesions, and retroperitoneal fibrosis. Attacks of flushing, diarrhea, and wheezing can be provoked by bolus injections of adrenaline, noradrenaline, or pentagastrin. While serotonin usually predominates, carcinoid tumors can also secrete, in varying proportions, 5-hydroxytryptophan, kallikrein, kinins, substance P and other neuropeptides, prostaglandins, catecholamines, and histamine. Of these, serotonin, kinins, histamine, and substance P are possible mediators of flushes; serotonin and substance P of hyperperistalsis; and serotonin, kinins, or histamine of bronchial constriction. Despite the gross excess of circulating serotonin, nearly all is platelet bound and therefore inactive. Very little is free in plasma. Demonstration of a contribution of serotonin to carcinoid attacks requires assay of free plasma serotonin; measurements of whole blood or serum serotonin are of little value. Some, but not all, provoked flushes have been shown to be accompanied by a rise in free plasma serotonin or substance P; an increase in circulating kinins has been more consistently shown. The 5HT2 antagonist ketanserin has been found to inhibit both provoked and spontaneous attacks of flushing, diarrhea, and dyspnea in a proportion of patients with carcinoid syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of somatostatin analog in management of carcinoid syndrome

Carcinoid tumors are the most frequent gut neuroendocrine tumors accounting for more than 50% of all tumors of the gastroenteropancreatic (GEP) axis. These tumors appear to derive from a stem cell line capable of differentiating into a variety of malignant cells that secrete many different peptides and amines. The symptoms of carcinoid tumors are often non-specific, vague abdominal pain that may precede the diagnosis by a median of 9 years. Carcinoid syndrome occurs in less than 10% of patients. We evaluated the effects of SMS 201-995 in 14 such patients, 12 with diarrhea, 8 with flushing, 3 with wheezing, one with tricuspid valve incompetence, 6 with facial telangiectasia, 3 with a pellagra type dermatosis and one with myopathy. Diarrhea was abolished or significantly reduced in 83%, flushing in 100%, wheezing in 100%, and myopathy improved in the one patient. Blood serotonin was resistant to change, urine 5HIAA fell in 75%, and most gut neuropeptide hormones apart from somatostatin were suppressed. Tumor growth appeared to be slowed in 2/3 of cases treated for up to 4 years. The analog of somatostatin appears to be a useful addition to the therapeutic armamentarium for carcinoid tumors and the symptom complex.

Clinical and echocardiographic comparison of patients with the carcinoid syndrome with and without carcinoid heart disease

To correlate clinical and laboratory variables in carcinoid heart disease, clinical data, echocardiograms, 24-hour urinary 5-hydroxyindoleacetic acid levels and liver function tests were evaluated in 30 patients with the carcinoid syndrome. The dominant cardiac lesion of carcinoid heart disease by echocardiography and Doppler was severe tricuspid regurgitation with right ventricular volume overload. A characteristic finding was thickened, retracted tricuspid valve leaflets that were fixed in a partially open position. Carcinoid heart disease was progressive and often fatal. The 17 patients with echocardiographic evidence of carcinoid heart disease had higher peak levels of urinary 5-hydroxyindoleacetic acid (331 +/- 231 vs 58 +/- 78 mg, p less than 0.001) and more severe hepatic dysfunction than the 13 patients without carcinoid heart disease. Although duration of symptoms of the carcinoid syndrome before echocardiography was similar for patients with and without carcinoid heart disease (5.4 +/- 6.4 vs 6.2 +/- 5.9 years, respectively, p greater than 0.1), survival after echocardiography was shorter for those with carcinoid heart disease (1.9 +/- 1.4 vs 3.8 +/- 2.9 years, p = 0.05). The findings support the concept that long-term exposure of the endocardium to serotonin in the right side of the heart leads to the development of heart lesions; in addition, progressive hepatic dysfunction may allow more serotonin to bypass liver enzymes and reach the right side of the heart.

Distinguishing features of idiopathic flushing and carcinoid syndrome

We compared the clinical and biochemical profiles of 11 patients with idiopathic flushing (IF) with those of eight patients with carcinoid syndrome (CS). Patients with IF were more often women, had a longer duration of symptoms, and were younger. Palpitations, syncope, and hypotension occurred only in patients with IF, while wheezing and abdominal pain occurred only with CS; diarrhea occurred in both types of patients. Elevated blood serotonin levels were present primarily in CS. Increased levels of urine 5-hydroxyindoleacetic acid was specific for CS but unsufficiently sensitive to detect all cases. Abnormalities of gut and vasoactive peptides failed to distinguish the two conditions. Flushing in carcinoid patients responds uniformly to octreotide (Sandostatin), but only one third of the patients with IF are relieved of the symptom. Patients with IF have features that distinguish them from individuals with flushing from other causes, such as CS, postmenopausal state, chlorpropamide-alcohol flush, panic attacks, medullary thyroid carcinoma, and autonomic epilepsy. Familiarity with the clinical and biochemical features of IF should facilitate evaluation and identification of these patients.

Pre-treatment with somatostatin in the anaesthetic management of a patient with carcinoid syndrome

Carcinoid syndrome produces flushing, bronchoconstriction and gastrointestinal hypermotility secondary to serotonin, histamine, bradykinin and prostaglandin release. A variety of drugs, foods and anaesthetic agents may provoke this syndrome. Under anaesthesia, the flushing produced may be associated with acute hypotension and cardiovascular collapse; this phenomenon is called a carcinoid crisis. Recently, somatostatin analogue has been used successfully to treat intraoperative carcinoid crisis. In this report, we present a 66-year-old lady with carcinoid syndrome who was pre-treated with 50 micrograms somatostatin analogue IV and IM prior to surgical manipulation. The anaesthetic course was relatively uneventful and the patient did well postoperatively.

[The disseminated endocrine system of man. A contribution of pathology]

The disseminated (or diffuse) endocrine system is composed of many single cells and small groups of cells disseminated in the whole organism, capable of producing biogenic amines and polypeptide hormones. They are also called APUD cells and were first detected in the mucosa of the intestinal tract, where they occur in highest concentration. Carcinoids are tumors of disseminated endocrine cells which sometime retain their hormone-producing capacity. These hormones are key factors in the control of numerous bodily functions; some are transported by way of the bloodstream, while others probably exercise their functions only within the tissue immediately adjacent to the producing cells (paracrine function). It is an interesting fact that almost identical hormones are found within the brain and within the peripheral autonomic nervous system, where they act as neural transmitters.

Carcinoid syndrome and intravenous cyproheptadine

The anaesthetic management of a patient with the carcinoid syndrome is reported. Important cardiovascular complications occurred immediately after tracheal intubation and during manipulation of metastases. Hypertensive crises were controlled with intravenous cyproheptadine, although hypotension and drowsiness were observed due to its use.

Wheezing and stridor

Wheezes are defined as high-pitched, continuous, adventitious lung sounds. They are produced by oscillation of opposing airway walls whose lumen is narrowed. Although asthma is the most common cause of wheezing, a wide variety of disease processes may result in wheezing due to airway obstruction. This obstruction may be caused by airway edema, smooth muscle constriction, increased secretions, vascular congestion, mass lesions, scarring, or foreign bodies. Stridor is a special kind of wheeze described as a loud musical sound of constant pitch, which is heard in patients with tracheal or laryngeal obstruction. The full differential diagnosis of airway obstruction should be carefully considered in any patient with wheezing or stridor.

Functional acute renal failure in a patient with carcinoid syndrome

Acute renal failure occurred in a patient with a carcinoid syndrome whenever he developed a flushing episode. Renal biopsy performed during one of these oliguric episodes did not reveal any lesions which could explain this reversible form of renal insufficiency. Urinary indices were not conclusive. Alteration of intrarenal hemodynamics by vasoactive compounds is proposed to be the causative mechanism of this relapsing acute oliguric renal failure.

Flushing in the carcinoid syndrome and plasma kallikrein

To examine the role of kallikrein in the etiology of flushing in the carcinoid syndrome, chromogenic substrates specific for kallikrein were used to measure two isoenzymes of this substance. The plasma and glandular kallikrein levels were determined in 20 carcinoid patients and in 17 controls. Kallikrein levels were not significantly different between these two groups. Twelve carcinoid patients and six controls were given alcohol and the kallikrein activity was measured before and at 2, 5, and 10 minutes after alcohol ingestion; kallikrein activity did not change significantly. Kallikrein was absent from the primary tumors of seven patients with carcinoids. These studies, therefore, indicate that kallikrein with subsequent induction of bradykinin formation is not solely responsible for the flushing in the carcinoid syndrome.

Tachykinins in carcinoid tumors: their use as a tumor marker and possible role in the carcinoid flush

The plasma concentrations of various tachykinins were measured before and during flushing episodes in 16 patients with metastatic carcinoid tumors. The flushing attacks were induced by iv injection of pentagastrin or ingestion of food or alcohol. Tachykinins, such as neurokinin A (NKA) and neuropeptide K (NPK), increased 2-fold during flushing episodes in 12 patients, and the plasma concentrations of substance P increased to a varying extent in 3 patients. Chromatographic analysis of plasma samples taken before and during flushing episodes in 2 patients indicated the presence of individual spectra of tachykinins. In addition, the plasma concentration of tachykinin [TKLI(K12)], using an assay that detects NKA, NPK, kassinin, eledoisin, and NKB, but not substance P and physalaemin, and the urinary excretion of 5-hydroxyindole acetic acid (5-HIAA) were measured in 20 patients with midgut carcinoid tumors before and during treatment with human leucocyte interferon. The overall changes in the 2 tumor markers were concordant in 18 of the 20 patients. Thus, the Spearman correlation coefficient between the percent changes in urinary 5-hydroxyindole acid excretion and plasma TKLI(K12) was 0.54 (P less than 0.001). The patients who had a decrease in the tumor markers also had a decrease in flushing episodes and diarrhea. Plasma TKLI(K12) is a convenient tumor marker for the diagnosis and follow-up of patients with carcinoid tumors of midgut origin. The combined use of both tumor markers strengthens the diagnosis and may improve the evaluation of response during treatment.

Peri-operative management of carcinoid syndrome using ketanserin

This report describes the successful use of ketanserin, a 5-HT2 receptor antagonist, for the acute control of systemic blood pressure in a patient with the carcinoid syndrome, undergoing hepatic artery embolisation. Serial measurements of plasma 5-hydroxyindoles, platelet 5-hydroxytryptamine and plasma catecholamines are also given.

Serotonin and the vascular system. Role in health and disease, and implications for therapy

Serotonin released from aggregating platelets can reach sufficient concentrations to affect local vascular function in a number of ways. The monoamine can cause contraction of blood vessels by its direct action on smooth muscle or by potentiating the effect of other vasoconstrictor agents. It can also induce vasodilatation by a direct relaxing effect on smooth muscle, by inhibition of adrenergic nerves, and by release of an uncharacterized relaxing factor from endothelial cells. One of its most likely physiological roles is to aid in haemostasis by promoting platelet aggregation and by causing local vasoconstriction at sites of injury. It probably has a role in some forms of vascular pathology as well: it may contribute to vasospasm of cerebral, coronary, and digital arteries, particularly if there is endothelial dysfunction or damage. Much evidence has implicated serotonin (5-hydroxytryptamine) in the pathogenesis of migraine. Serotonergic agonists, such as ergotamine, and antagonists, such as methysergide and pizotifen, are both used in therapy of migraine. Promising but conflicting early results have not yet defined a place for serotonergic antagonists in other vasospastic disorders. The antihypertensive efficacy of one serotonergic antagonist, ketanserin, raises questions about the possible involvement of serotonin in either the initiation or the maintenance of the elevated peripheral vascular resistance in several forms of hypertension, including essential hypertension.

The carcinoid syndrome: comparison of 21 necropsy subjects with carcinoid heart disease to 15 necropsy subjects without carcinoid heart disease

Carcinoid heart disease is a morphologically specific type of cardiac disorder that involves the mural and valvular endocardium on the right side of the heart. Twenty-one subjects (57 percent) (Group I) with carcinoid heart disease and 15 subjects (43 percent) (Group II) without carcinoid heart disease were studied at necropsy. The two groups were similar in mean age (54 years versus 55 years), duration of clinical illness (4.7 years versus 6.3 years), body weight (50 kg versus 52 kg), systemic blood pressure (117/77 mm Hg versus 128/77 mm Hg), blood hematocrit levels (37 percent versus 36 percent), total serum protein levels (6.0 g/dl), and serum albumin levels (2.2 g/dl versus 2.6 g/dl). The two groups were different in the frequency of the presence of precordial murmurs consistent with tricuspid regurgitation and/or pulmonic stenosis (95 percent versus 13 percent), cardiomegaly by chest radiography (38 percent versus 0), low voltage on electrocardiography (47 percent versus 0), and location of the primary site of the carcinoid tumor. Total electrocardiographic 12-lead QRS voltage was similar in each group (105 mm versus 132 mm) (10 mm = 1 mV). Of Group I subjects, 43 percent died of cardiac causes; none of the Group II subjects died of cardiac causes. Of the 21 subjects with carcinoid heart disease, seven had left-sided cardiac involvement, but in none was it of functional significance. Thus, although carcinoid heart disease frequently is the cause of death in patients with the carcinoid syndrome, the development of carcinoid heart disease is not related to the duration of symptoms of the carcinoid syndrome.

The pentagastrin test in the diagnosis of the carcinoid syndrome. Blockade of gastrointestinal symptoms by ketanserin

The levels of 5-hydroxytryptamine (serotonin, 5-HT) and substance P (SP) were assayed (using high performance liquid chromatography-electron capture and radioimmunoassay methods) in the peripheral blood of 17 patients with known mid-gut carcinoids, 16 of whom had hepatic metastases. All patients had supranormal basal levels of 5-HT and SP. The clinical and hormonal changes induced by two provocation tests, intravenous pentagastrin (PG) and calcium infusion, were compared. Pentagastrin caused flushing in all the patients, induced gastrointestinal symptoms in all but one of the patients with hepatic involvement, and universally elevated circulating 5-HT levels. Pretreatment with a 5-HT2-receptor blocking agent, ketanserin, abolished the gastrointestinal effects but had virtually no influence on either 5-HT levels or flushing induced by intravenous pentagastrin. In contrast, calcium infusion induced carcinoid symptoms in only two of six patients, and this was consistently associated with stimulation of circulating serotonin levels. The authors conclude that 1) 5-HT may be responsible for the gastrointestinal symptoms in carcinoid patients, but it does not seem to play any role in flushing; 2) ketanserin may be a useful therapeutic agent in alleviating gastrointestinal symptoms in carcinoid patients; 3) differential responses to PG suggests that SP is released from a site different from that of 5-HT; 4) it is possible that SP may contribute to the mediation of flushing, but it cannot be the sole agent causing this symptom; and 5) the pentagastrin test with measurements of 5-HT levels in peripheral blood seems to be superior to calcium infusion as a provocative test in documenting the diagnosis of carcinoid disease.

The effect of carcinoid levels of serotonin and substance P on hemodynamics

Serotonin and substance P circulate in high concentrations in patients with the carcinoid syndrome. These studies were performed to evaluate the effects of intravenous infusions of serotonin and substance P to reproduce carcinoid levels of these agents on central hemodynamics, regional blood flow (using the radioactive microsphere technique), and endogenous hormone release. Serotonin did not affect mean arterial pressure but it significantly increased cardiac output, decreased systematic vascular resistance, and redistributed regional blood flow, increasing blood flow to the heart, adrenals, fundus, and antrum. Substance P significantly decreased mean arterial pressure and systemic vascular resistance, increased cardiac output, and increased blood flow to adrenal, fundus, antrum, liver, and all muscular layers of the stomach and small bowel. Neither serotonin nor substance P affected skin blood flow, nor altered circulating levels of glucose, insulin, or gastrin. Although both of these agents seem to participate in the pathogenesis of the carcinoid syndrome, our studies suggest that it is not possible to ascribe all the hemodynamic abnormalities to either.

Circulation, respiration and serotonin levels in carcinoid patients during neurolept anaesthesia

Release of hormones peri-operatively in patients with metastatic carcinoids may lead to severe circulatory and respiratory disturbances. Fourteen patients with liver metastases were studied during 16 operations with a modified neurolept anaesthesia in order to evaluate the central haemodynamic and respiratory functions as well as plasma serotonin levels. The premedication in five patients was supplemented with levopromazine. During the 11 operations performed on patients not pretreated with levopromazine, no major significant fluctuations in circulatory or respiratory functions were recorded although big variations in serotonin plasma levels were measured. In the patients treated with levopromazine, however, significant changes were observed in heart rate, mean pulmonary artery pressure, cardiac index, and left and right ventricular stroke work especially during flushing episodes. However, these changes did not correlate with the changes in plasma serotonin levels. Modified neurolept anaesthesia without levopromazine pretreatment combined with careful monitoring seems to be a safe procedure for carcinoid patients. Using this type of anaesthetic procedure only one major complication occurred in connexion with 16 major operations and then in the postoperative period.