Somatostatin reduces gastric mucosal blood flow in normal subjects but not in patients with cirrhosis of the liver

Octreotide improves human lymphatic fluid transport a translational trial

OBJECTIVES

Chylothorax is a complex condition and many different pharmacological agents have been tried as treatment. Octreotide is used off-label to treat chylothorax, but the efficacy of octreotide remains unclear. A decrease in lymph production is suggested as the mechanism. In this cross-over study, we explore the direct effect of octreotide on human lymphatic drainage.

METHODS

Pre-clinical: the effect of octreotide on force generation was assessed during acute and prolonged drug incubation on human lymphatic vessels mounted in a myograph. Clinical: in a double-blinded, randomized, cross-over trial including 16 healthy adults, we administered either octreotide or saline as an intravenous infusion for 2.5 h. Near-infrared fluorescence imaging was used to examine spontaneous lymphatic contractions and lymph pressure in peripheral lymphatic vessels and plethysmography was performed to assess the capillary filtration rate, capillary filtration coefficient and isovolumetric pressures of the lower leg.

RESULTS

Pre-clinical: human thoracic duct (n = 12) contraction rate was concentration-dependently stimulated by octreotide with a maximum effect at 10 and 100 nmol/l in the myograph chamber. Clinical: spontaneous lymphatic contractions and lymph pressure evaluated by near-infrared fluorescence did not differ between octreotide or placebo (P = 0.36). Plethysmography revealed similar capillary filtration coefficients (P = 0.057), but almost a doubling of the isovolumetric pressures (P = 0.005) during octreotide infusion.

CONCLUSIONS

Octreotide stimulated lymphatic contractility in the pre-clinical setup but did not affect the spontaneous lymphatic contractions or lymph pressure in healthy individuals. Plethysmography revealed a doubling in the isovolumetric pressure. These results suggest that octreotide increases lymphatic drainage capacity in situations with high lymphatic afterload.

Effect of norepinephrine infusion on hepatic blood flow and its interaction with somatostatin: an observational cohort study

Background

Norepinephrine (NE) is a α₁-adrenergic mediated vasopressor and a key player in the treatment of perioperative hypotension. Apart from modulating systemic hemodynamics, NE may also affect regional blood flow, such as the hepatic circulation, which contains a wide variety of adrenergic receptors. It may alter regional vascular tonus and hepatic blood flow (HBF) by reducing portal vein flow (PVF) or hepatic arterial flow (HAF). The aim of this study was to assess the effects of NE on HBF.

Methods

Patients scheduled for pancreaticoduodenectomy were included. All patients received standardized anesthetic care using propofol and remifentanil and were hemodynamically stabilized using a goal-directed hemodynamic strategy guided by Pulsioflex™. On surgical indication, somatostatin (SOMATO) was given to reduce pancreatic secretion. HBF measurements were performed using transit-time ultrasound (Medistim™). Baseline hemodynamic and HBF measurements were made after pancreatectomy, at T1. Afterwards, NE infusion was initiated to increase mean arterial pressure (MAP) by 10 – 20% of baseline MAP (T2) and by 20 – 30% of baseline MAP (T3). HBF and hemodynamic measurements were performed simultaneously at these three time-points.

Results

A total of 28 patients were analyzed. Administration of NE significantly increased MAP but had no effect on cardiac index. NE infusion reduced total HBF in all patients (p < 0.01) by a reduction HAF (p < 0.01), while the effect on PVF remained unclear. Post-hoc analysis showed that SOMATO-treated patients had a significant lower PVF at baseline (p < 0.05), which did not change during NE infusion. In these patients, reduction of total HBF was primarily related to a reduction of HAF (p < 0.01). In untreated patients, NE infusion reduced total HBF both by a reduction HAF (p < 0.01) and PVF (p < 0.05).

Conclusion

Administration of NE reduced total HBF, by decreasing HAF, while the effect on PVF remained unclear. SOMATO-treated patients had a lower PVF at baseline, which remained unaffected during NE infusion. In these patients the decrease in total HBF with NE was entirely related to the decrease in HAF. In SOMATO-untreated patients PVF also significantly decreased with NE.

Trial registration

Study protocol EC: 2019/0395.

EudraCT n°: 2018–004,139-66 (25 – 03 – 2019).

Clin.trail.gov: NCT03965117 (28 – 05 – 2019).

Partial splenic embolization is superior to intravenous somatostatin for decreasing portal pressure in cirrhotic patients: a dynamic self-controlled cohort study

AIMS

The efficacy of somatostatin in altering splanchnic hemodynamics in cirrhotic portal hypertension is still controversial. We aimed to establish the dynamic effect of somatostatin on portal pressure in cirrhotic patients and compared its effect with Partial Splenic Embolization (PSE).

METHODS

Eighteen patients with cirrhotic portal hypertension were prospectively recruited. The wedged hepatic venous pressure (WHVP) and free hepatic venous pressure (FHVP) were repeatedly measured at baseline, 1-, 5-, 10- and 20-min after initiating somatostatin infusion. After somatostatin infusion cessation and washout, WHVP and FHVP were measured before and after PSE. The change in all the variables between time points was analyzed.

RESULTS

Decreased hepatic venous pressure gradient (HVPG) 5-min after initiation of infusion was identified compared with baseline level (19.6%; p-value: .042), which was achieved through elevated FHVP (37.5%; p-value: 9.26e - 04). There was no significant decrease in WHVP at any time point during somatostatin infusion. The HVPG (17.4%; p-value: 1.27e - 04) and WHVP (10.4%; p-value: 3.00e - 03) post-PSE significantly decreased compared to the washout level. No significant distribution differences in the number of patients with HVPG decrease by a percentage relative to the baseline level were identified between the 5-min time point and post-PSE.

CONCLUSION

Our study indicates that somatostatin administration does not decrease WHVP within 20 min at clinically recommended doses. While somatostatin did decrease HVPG, this effect was achieved through increased FHVP, providing a possible explanation for its unclear efficacy. In contrast, PSE decreases both the WHVP and the HVPG.

Octreotide lowers gastric mucosal blood flow in normal and portal hypertensive stomachs

BACKGROUND

The vasoactive peptide octreotide has an established role in controlling variceal hemorrhage. The mechanism of action is believed to be a reduction in splanchnic blood flow. A decrease in splanchnic blood flow should be mirrored by a decrease in gastric mucosal blood flow (GMBF). Laser Doppler flowmetry (LDF) should detect changes in GMBF.

METHODS

In seven normal volunteers and four patients with portal hypertension, 100 micro g of octreotide was administered as an intravenous bolus. Continuous LDF measurements were then made at a single point on the midantrum for at least 10 min and plotted against time for each subject.

RESULTS

After a variable period of stabilization, GMBF decreased in all subjects except one. This was statistically significant in both the controls and the patients with portal hypertension.

CONCLUSIONS

Octreotide decreases GMBF in normal and portal hypertensive stomachs. Laser Doppler is a useful and minimally invasive tool to assess the effect of drugs on GMBF.

The effect of octreotide on gastroduodenal blood flow measured by laser Doppler flowmetry in rabbits and man

OBJECTIVE

The somatostatin analogue, octreotide is valuable in the management of variceal bleeding, and it has been suggested that it may stop peptic ulcer hemorrhage by reducing gastroduodenal blood flow or increasing intragastric pH. The aim of this study was to determine the effect of intravenous octreotide infusion on gastroduodenal mucosal blood flow and gastric pH.

METHODS

Seven New Zealand white rabbits and five healthy human volunteers were used. Mucosal blood flow was measured using a laser Doppler flowmeter (LDF). The Doppler probe was positioned in the upper gastrointestinal tract of the seven rabbits and five human volunteers. Blood flow was measured before and after octreotide infusion.

RESULTS

In the animal experiments, mucosal blood flow was decreased in a dose dependent manner in the gastric body (209.1-56.3 U) (p < 0.008), antrum (143.3-33.3 U) (p < 0.02) and duodenum (254-67.6 U) (p < 0.016) by doses of octreotide ranging from 10-50 microg/kg of body weight. In the human studies, mucosal blood flow was decreased in the gastric body (p < 0.016) and antrum (p < 0.009) after octreotide infusion (dose 1-1.5 microg/kg). Intragastric pH was significantly increased (p < 0.05). The change was not associated with systemic hemodynamic changes.

CONCLUSIONS

Gastroduodenal mucosal blood flow was reduced and intragastric pH increased by octreotide. This agent could be helpful in the management of gastroduodenal mucosal bleeding.

Advances in drug therapy for acute variceal haemorrhage

Recent advances in the pharmacology of portal hypertension are reviewed, against the background of existing knowledge and current clinical research. The most recent trials are analysed, and conclusions made about the use of drugs in acute variceal haemorrhage, as well as directions for further clinical trials and research.

Somatostatin reduces gastric mucosal blood flow in patients with portal hypertensive gastropathy: a randomized, double-blind crossover study

Agents which decrease gastric mucosal blood flow (GMBF) are postulated to have beneficial effects in arresting gastrointestinal bleeding in cirrhotic patients with portal hypertension. Our objective was to test the hypothesis that in a dose that significantly lowers wedged hepatic venous pressure (WHVP), a bolus injection of somatostatin will significantly decrease GMBF in patients with portal hypertensive gastropathy (PHG). In this placebo-controlled, double-blind, crossover study, 20 cirrhotic patients with PHG were randomly assigned to receive either somatostatin followed by placebo (Group A) or placebo followed by somatostatin (Group B). Wedged hepatic venous pressure was monitored. GMBF in the antrum and corpus was assessed by reflectance spectrophotometry. Indices of hemoglobin concentration (IHb) and indices of oxygen content (ISO2) were recorded. Nine patients were assigned to Group A, and 11 to Group B. Mild PHG was seen in 16 patients, and severe PHG in 4 patients. Baseline WHVP, IHb, and ISO2 were similar in both treatment groups. Wedged hepatic venous pressure (WHVP) was significantly lowered [median, 17.6%; interquartile range (-27.0,-12.6%); P = 0.0008] after a 250-microg bolus injection of somatostatin. This dose of somatostatin significantly reduced IHb both in the antrum [-10.2% (-23.4, 0.4%)] and in the corpus [-5.8% (-16.6, 5.6%)] compared to placebo (P = 0.02 and 0.04, respectively). Intravenous bolus injection of 250 microg somatostatin significantly reduces WHVP and GMBF in patients with PHG. Whether this ability to decrease the GMBF in PHG makes somatostatin an effective treatment in acute gastrointestinal bleeding in PHG deserves to be studied.

Octreotide in variceal bleeding

Bleeding from oesophageal varices has a high death rate. Injection sclerotherapy is the most appropriate treatment but facilities for this are not always available. Balloon tamponade and vasoactive therapy may be used as stop gap measures. Somatostatin and octreotide are therapeutic candidates for the treatment of variceal bleeding and there are several trials that have compared somatostatin and octreotide with other treatments for this condition. The results of these trials are summarised and discussed. A meta analysis of the group of trials of placebo or H2 antagonists v somatostatin or octreotide showed a significant advantage of somatostatin or octreotide in terms of efficacy, but no difference in mortality. The trials discussed seem to show that somatostatin and octreotide are at least as effective as other treatments, with the benefit of fewer adverse effects, and thus represent the best vasoactive agents. Additionally, they may have a role as adjuvant treatment to emergency sclerotherapy for active bleeders and this must be further investigated.

Pharmacodynamic effects of Sandostatin in the gastrointestinal tract

Somatostatin (SST) is widely distributed throughout the human gastrointestinal system. There, it is found in neurons and fibers of both the submucosal and myenteric plexus and the pancreas, and also in the D cells of the stomach, gut, and pancreatic islets. Whereas in the intestinal nervous system, duodenum, and pancreas, somatostatin-14 (SST-14) appears to be the predominant molecular form, the endocrine-type D cells of the intestine primarily contain somatostatin-28 (SST-28). SST peptides may act very differently at different sites, as hormones, paracrine substances, or neurotransmitters. Because of this complexity of action, very little is known about the physiological effects of SST in the gastrointestinal tract. In contrast, the pharmacological actions of natural synthetic SST have been thoroughly studied and have given rise to many therapeutic applications. Octreotide, an analogue with a longer half-life and higher potency, has greatly facilitated the clinical application of SST. This review deals with the pharmacological effects of octreotide on different gastrointestinal functions. The SST analogue exerts a long-lasting inhibitory action on gastric acid, pancreatic enzyme, bicarbonate secretion, and on bile flow. It also inhibits stimulated intestinal secretion, ie, the release of neuropeptides from the gut and pancreas. It can also prolong orocecum transit time and prevent gallbladder contraction. It inhibits absorption of nutrients and exerts inhibitory effects on splanchnic hemodynamics. It is because of these actions that SST has attracted so much attention in the treatment of different gastrointestinal disorders.

Randomized, double-blind, placebo-controlled trial of somatostatin for variceal bleeding. Emergency control and prevention of early variceal rebleeding

A randomized, double-blind, placebo-controlled trial of somatostatin was conducted among 120 patients admitted for bleeding esophageal varices (59 placebo, 61 somatostatin). An initial 250-micrograms bolus of somatostatin followed by a 5-day continuous infusion of 250 micrograms/h and an identical administration of placebo were evaluated for both the control of bleeding and prevention of early rebleeding from varices. Failure to control bleeding occurred in 22 (36%) somatostatin patients vs. 35 (59%) placebo patients, with time to failure occurring earlier with placebo (P = 0.036). blood and plasma transfused per hour during drug infusion of trial drug was reduced in the somatostatin group: median 0.033 vs. 0.105 unit/h (P = 0.025). Use of balloon tamponade was halved in somatostatin-treated patients. The average effect of somatostatin was a 41% reduction in the hazard of failure (95% confidence interval, -1% to 65%, P = 0.0545) after adjustment for the severity of liver disease, which was the only other variable having a significant influence on time to failure. There was no difference in 30-day mortality per admission (7 placebo, 9 somatostatin) or complications. It is concluded that somatostatin is safe and more effective than placebo for the control of variceal bleeding.

Nonsurgical control of upper gastrointestinal hemorrhage in old age patients: intragastric norepinephrine and endoscopic alcoholization of lesions

Of 28 consecutive patients over 64 years old, in whom endoscopy revealed gastro-duodenal ulcers with signs of recent hemorrhage (active bleeding, non-bleeding vessel or adherent clot), 14 were randomly assigned to receive endoscopic alcoholization of the lesions preceded by intragastric instillation of norepinephrine, while as controls 14 received antacids. After the applied treatment the bleeding stopped in all cases (100%) in the study group and one patient died (7.1%) after hemostasis was achieved. In the control group bleeding stopped in 12 patients (85.7%). Two patients continued to bleed and needed emergency surgery. Another patient had a major rebleed successfully treated by alcoholization. There were 4 deaths (28%): 2 patients died postoperatively and the other 2 from acute porphyria and bronchopneumonia respectively. The transfusion requirements after the entry into trial were significantly lower in the study group compared to controls (mean no. of blood units 0.79 vs. 1.71). No complications were seen with the treatment applied. These results suggest that endoscopic alcoholization of the lesions preceded by intragastric instillation of norepinephrine is an effective and safe emergency therapy for bleeding from peptic ulcers in old age patients.

Somatostatin in portal hypertension

The effect of somatostatin on portal pressure is mediated by splanchnic arterial vasoconstriction which induces a reduction in portal blood flow and pressure. One of the most important characteristics of somatostatin is that its splanchnic effect is not accompanied by major systemic hemodynamic effects. Somatostatin has been used in several controlled trials to test its potential in controlling acute variceal bleeding. The results remain controversial. Different findings in existing clinical trials may derive in part from distinct protocols for somatostatin administration. Published trials suggest that somatostatin may be as effective as vasopressin in the acute management of variceal bleeding. However, since the efficacy of vasopressin has been questioned, a comparison of two potentially ineffective drugs cannot establish definitively the efficacy of somatostatin in controlling variceal bleeding. The most significant finding of the two published studies has been the lower incidence of minor and major complications with somatostatin when compared to vasopressin. Newer trials in progress may shed new light into the potential use of somatostatin for the treatment of variceal bleeding.

Gastric, duodenal, and pancreatic somatostatin-like immunoreactivity during hypovolemic shock

Because hypovolemic shock is known to cause gastric ulcers in animals and human beings, we investigated the tissue levels of somatostatin-like immunoreactivity (SLI) in the gastric corpus and antrum, duodenum, and pancreas during hypovolemic shock in rats. We studied male Wistar rats (N = 10 each) 15 min, 2 hr, and 12 hr after hypovolemic shock and compared results to a control group (N = 15). Two rats in both 2-hr and 12-hr groups showed gastric ulcers: three corporal and one antral. One animal developed multiple ulcers. In the gastric corpus and antrum and in the duodenum, tissue SLI showed significant decrease 15 min and 2 hr after shock. Gastric SLI remained low, whereas duodenal SLI recovered and rose above control level at 12 hr. Pancreatic SLI showed no significant changes during hypovolemic shock. Gastric tissue SLI levels that were significantly lower after shock than those of normal controls may have contributed to the peptic ulcer disease induced by hypovolemic shock in this experimental model.

Gastrointestinal somatostatin: distribution, secretion and physiological significance

Somatostatin-like immunoreactivity (SLI) has been found throughout the gastrointestinal tract in all species examined. In the stomach it is mainly present in endocrine-type D-cells whereas in the intestine there is also an extensive distribution in enteric neurones. In all regions of the gastrointestinal tract multiple forms of somatostatin exist. A precursor (prosomatostatin) has been partially sequenced, three forms with 20 (SS-20), 25 (SS-25) and 28 (SS-28) amino acids completely sequenced, and somatostatin-14 (SS-14) demonstrated by radioimmunoassay. Both SS-14 and SS-28 exert a wide range of actions on the gastrointestinal tract and there is strong supportive evidence for a role in the regulation of gastric acid and gastrin secretion, gastrointestinal motility and intestinal transport. Both in vivo and in vitro studies on the secretion of gastric SLI into the vasculature have shown that nutrients initiate the process but that subsequent events are regulated by a complex interplay between hormonal and neuronal pathways. GIP is one of the most potent hormonal secretagogues. In the stomach, acetylcholine, opioid peptides and substance P are probably involved in parasympathetic inhibitory pathways and gastrin releasing peptide in stimulatory pathways. The sympathetic nerves are also stimulatory. Regulation of secretion of intestinal SLI has not been so extensively studied. Although SLI is also found in the gastrointestinal lumen the significance is unclear. Despite these advances the exact route of delivery of somatostatin to its target organs is uncertain and paracrine, endocrine and neural pathways may all be involved.

Somatostatin in treatment of haematemesis and melaena

630 patients with haematemesis and melaena were randomly allocated to treatment by a constant intravenous infusion of either somatostatin or an apparently identical placebo in a double-blind controlled trial. Rebleeding was less common in treated patients (70 episodes in 315 individuals compared with 89 episodes in 315 controls) but the difference was not significant. Operation rates were virtually identical (35 treated patients and 34 controls), while there were slightly more deaths in the treated group than in the controls (31 and 25, respectively). These results are in clear disagreement with those of other smaller series. Though it is not possible to be completely sure that treatment is not useful in some individuals, earlier claims of marked benefit seem unlikely to be justified.