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Biomedical subjects

N F Couse

Publications and source records attributed to N F Couse.

18 recordsLinked to original sources
PubMed1999

Inferior mesenteric venous sampling, pulse oximetry, and assessment of colonic perfusion during aortic aneurysm surgery.

Ischemic colitis is a serious complication of aortic surgery. The condition continues to be difficult to diagnose at an early stage. This study monitors the biochemical changes in systemic and selective inferior mesenteric vein (IMV) blood sampling during aortic surgery and compares the reproducibility of this method to intraoperative colonic pulse oximetry in a series of 18 patients undergoing infrarenal aortic aneurysm repair. Base excess, pH, pCO2, and lactate were altered by aortic cross-clamping but returned to normal within 48 hr. IMV inorganic phosphate levels were higher than systemic values, suggesting improved sensitivity with selective sampling. BB isoenzymes of creatine kinase remained normal in all patients. Pulse oximetry signals were inconsistently obtained from the colon. This study establishes the physiological changes in IMV biochemistry during aortic surgery. Unlike intraoperative pulse oximetry, selective IMV sampling provides reproducible measurements of colonic perfusion. This simple and safe technique warrants further assessment of its accuracy at diagnosing ischemic colitis.

Alanine Transaminase↗
PubMed1997

Lower extremity bypass for critical ischemia using synthetic conduit and adjuvant vein cuff.

The use of an interposition cuff of vein placed at the distal anastomosis between synthetic bypass conduit and outflow vessel has been advocated to improve patency of lower extremity bypass grafts. Over a three-year period we have performed 43 such bypass procedures: to the above knee popliteal artery (n = 3); below knee popliteal (n = 13), and infrapopliteal arteries (n = 27). There were 20 females and 23 males having a mean age of 70 years (48-84 years). Fifteen patients were hypertensive, 15 were diabetic, and 25 had a history of tobacco use. All cases required limb salvage for rest pain (n = 25), gangrene (n = 10), or ulceration (n = 8) in the absence of suitable autologous vein. Nineteen operations followed a previous failed bypass. Patients were reviewed at six-month intervals. The operative mortality was 8% and two-year primary and secondary patency were 40% and 55%, respectively. Cumulative patency rates were better for first-time grafting procedures than for patients who had undergone previous attempts at limb salvage (60% versus 22%). Two-year limb salvage was 60%. During the same time period, two-year primary and secondary patency rates were 54% and 67%, respectively for autogenous vein. Although the numbers are small these results support the use of an adjuvant vein cuff when employing synthetic grafts. A prospective study of vein versus synthetic graft plus cuff should be undertaken.

Aged↗
PubMed1994

Investigation and management of subclavian steal syndrome.

Patients with subclavian steal syndrome present with symptoms of vertebrobasilar ischaemia. Although angiography has traditionally been used to confirm the diagnosis of subclavian steal and plan reconstructive surgery in symptomatic patients, duplex ultrasonography now offers rapid diagnosis and also permits examination of the other extracranial vessels. The treatment of subclavian steal syndrome is surgical. Extra-anatomic bypass procedures are used to increase inflow to the subclavian artery, abolishing the steal phenomenon. Carotid-subclavian bypass or transposition and subclavian-subclavian or axilloaxillary bypass are the procedures of choice; selection is governed by the presence of coexistent carotid artery disease. Percutaneous transluminal balloon angioplasty of the subclavian artery is an alternative treatment, although the long-term patency rate is inferior to that of extra-anatomic bypass.

Carotid Arteries↗
PubMed1994

Pulse oximetry in the diagnosis of non-critical peripheral vascular insufficiency.

Pulse oximetry was used to detect return of pulsatile flow in 27 subjects during reactive hyperaemia following 3 min of total limb ischaemia induced by above knee tourniquet occlusion. Fourteen patients with exercise induced leg pain had 18 symptomatic limbs tested. Thirteen controls had 25 limbs tested. Return of pulsatile flow during reactive hyperaemia occurred within 20 s of tourniquet release in the 25 control limbs which was then regarded as normal. The mean time for return of pulsatile flow in 18 symptomatic limbs was 53 +/- 37 s (P < 0.05 versus controls). Three limbs had a normal value, two of which did not have peripheral vascular disease. Pulse oximetry correctly identified all 25 asymptomatic limbs and 15 of 16 patients with claudication secondary to peripheral vascular disease (PVD). This modification of the reactive hyperaemia test using the pulse oximeter is simple and quick to perform. It has potential as a non-invasive screening test for PVD, suitable for outpatient assessment.

Adult↗
PubMed1993

Extracorporeal shock wave lithotripsy induces the release of prostaglandins which increase ureteric peristalsis.

The aim of this study was to identify the changes in secretion of prostaglandins into the urinary tract as a result of treatment by extracorporeal shock wave lithotripsy (ESWL) and to determine their effects on ureteric motility. Sixteen patients with renal or upper ureteric calculi were studied. A peripheral blood and urine sample was collected immediately before and after ESWL, with further samples taken 24 h later. The following variables were assessed by radioimmunoassay:prostaglandin E2 (PGE2), prostaglandin F1 alpha (PGF1 alpha), and thromboxane B2 (TXB2). An in vitro canine study was then designed to study the activity of TXB2, PGF1 alpha and PGE2 on an isolated intact canine ureter model. Significant elevations of TXB2 were found immediately after ESWL in both serum and urine, which fell almost to pre-treatment levels by 24 h. PGF1 alpha levels showed significant elevations at 24 h but no immediate increase as seen with TXB2. In contrast, PGE2 levels were unchanged in the urine but significantly decreased in the serum. In vitro studies showed that both TXB2 and PGF1 alpha repeatedly produced an increased frequency of ureteric contraction. ESWL results in the release of prostaglandins from the urinary tract which are shown to cause increased ureteric peristalsis.

Adult↗
PubMed1993

Evolving management of biliary tract disease.

The variety of treatments available for gallstone-related problems require a multidisciplinary approach with involvement of the surgeon, endoscopist, and radiologist. Many conditions, until recently treatable only by an open operation, can now be satisfactorily dealt with by minimally invasive or endoscopic techniques. The benefits of such techniques are immediately apparent in terms of reduced hospital stay and early patient recovery. The pace of progress, particularly in the area of laparoscopic biliary surgery, is rapid and has important implications for surgical training and resources. Careful audit and prospective trials, when appropriate, are required to determine optimum treatment strategies for patients with benign biliary disease. These are exciting times in surgery, but our enthusiasm for new techniques should not cloud time-honored surgical principles.

Aged↗
PubMed1991

The role of 3 hour distal oesophageal pH monitoring in gastro-oesophageal reflux.

It has been suggested in the literature that an eight hour period of distal oesophageal monitoring is adequate for the diagnosis of reflux in symptomatic patients. The aim of this study was to investigate whether 3 hour intra-oesophageal pH-metry could be substituted for the eight hour test period without loss of sensitivity in the diagnosis of GOR. Twenty patients were tested, 10 of whom had classical De Meester symptoms of GOR and 10 asymptomatic patients served as controls. All were commenced on 3 hour ambulant pH monitoring of the distal oesophagus. This was followed by a separate period of 8 hour testing. Each test had a 50% supine time period. The following variables were determined: (i) number of reflux episodes (ii) number longer than 5 minutes (iii) longest episode of reflux, (iv) percent of time that pH was below 4. Results are analysed using the 'Esophogram' computer program. 8 hour monitoring resulted in a positive diagnosis of GOR in 10 of 10 patients, giving an overall sensitivity of 100%. 3 hour testing was positive in 8 patients (sensitivity of 80%). The best correlations were obtained when comparing total reflux episodes, and the percent of total time pH less than 4, but overall the tests correlate poorly for individual variables. None of the controls had positive 3 or 8 hour testing. We conclude therefore, that 3 hour pH metry may be a useful screening test to confirm symptomatic reflux, and can be performed within a single clinic visit. If negative, arrangements must be made for more prolonged monitoring.

Female↗
PubMed1991

Pneumoperitoneum without peritonitis.

We present our experience with 5 patients, all of whom were noted to have radiological signs of pneumoperitoneum in the absence of clinical features of peritonitis. All 5 cases were eventually shown to be due to causes not requiring surgery. We review the numerous unusual causes of pneumoperitoneum which do not require urgent surgical intervention and emphasize their importance in cases where the absence of signs of peritonitis may cause diagnostic difficulty.

Adult↗
PubMed1990

The effect of pancreatic polypeptide infusion on glucose tolerance and insulin response in longitudinally studied pancreatitis-induced diabetes.

Glucose intolerance is often associated with pancreatitis. Pancreatitis-induced diabetes represents a different clinical syndrome than type I and type II diabetes mellitus. Patients with pancreatitis-induced diabetes may be extremely sensitive to exogenous insulin, rarely develop ketoacidosis, and rarely exhibit classic diabetic complications, such as retinopathy, nephropathy, or accelerated vasculopathy. Pancreatic polypeptide (PP) deficiency has been implicated in the defect of glucose homeostasis found after pancreatitis. This study evaluated intravenous and oral glucose tolerance and insulin response to glucose loading, in the setting of pancreatitis, with and without short-term PP replacement. Dogs (n = 7) underwent pancreatic duct ligation (PDL) and were studied with and without PP infusion (2 micrograms/kg/hr) before PDL and at 1 week, 6 weeks, and 4 months after PDL by means of intravenous and oral glucose tolerance tests. Basal and bombesin-stimulated PP levels at 4 months after PDL were subnormal, verifying PP deficiency in these animals with pancreatitis. PP levels during PP infusion reproduced normal postcibal levels, averaging 897 +/- 40 pg/ml. Glucose tolerance, expressed as the glucose decay constant for the intravenous glucose tolerance tests and as the integrated glucose response for the oral glucose tolerance tests, deteriorated over time and was not improved by acute PP replacement. The integrated insulin response to glucose was not affected by PP. The acute infusion of PP at a dose that reproduces normal postprandial PP levels fails to improve glucose tolerance or augment insulin release in this model of pancreatitis-induced diabetes.

Administration, Oral↗
PubMed1989

Pancreatic structure and glucose tolerance in a longitudinal study of experimental pancreatitis-induced diabetes.

Chronic pancreatitis is associated with glucose intolerance and resultant pancreatogenic diabetes. Using the canine pancreatic duct-ligated model of pancreatitis, we serially evaluated pancreatic histology and electron microscopy, tolerance to intravenous and oral glucose, and insulin response to glucose loading. Pancreatic duct ligation caused microscopic evidence of acute pancreatitis at 1 week, progressing to acinar loss and fibrosis consistent with chronic pancreatitis at time periods up to 6 months. The islets of Langerhans showed degranulation early and appeared to be structurally preserved late. Calculated K values indicated a progressive significant deterioration in intravenous glucose tolerance, falling significantly from 3.46 +/- 0.23 basally to 1.51 +/- 0.17 at 6 months after duct ligation (p less than 0.0001). Oral glucose tolerance deteriorated significantly, with the integrated glucose response rising from 23.7 +/- 1.2 g/dl.minute basally to 32.3 +/- 2.8 g/dl.minute at 6 months after duct ligation (p less than 0.05). Integrated insulin response to both intravenous and oral glucose deteriorated with pancreatitis. Pancreatitis-induced glucose intolerance is a consistent feature of this duct-ligated model. Glucose intolerance stabilizes between 4 and 6 months after duct ligation and is associated with pancreatic acinar fibrosis and pancreatic endocrine structural preservation. While the mechanism of altered glucose tolerance may involve mechanical, neural, humoral, or vascular events, our data clearly support the conclusion that pancreatic ductal stenosis with resultant pancreatic fibrosis and chronic pancreatitis is associated with abnormal islet responsiveness leading to circulating insulin deficiency and glucose intolerance, despite histologic and ultrastructural evidence of intact islets of Langerhans.

Amylases↗
PubMed1989

Serotonin and substance P stimulate intestinal secretion in the isolated perfused ileum.

The actions of serotonin and substance P have been examined with use of an isolated, vascularly perfused rabbit ileal preparation. The vascular perfusate was composed of a modified Krebs' buffer solution that contained washed human red blood cells (hematocrit, 15% to 20%) and 3% albumin, with no added hormones or peptides. Ileal blood flow was held constant at 49.3 +/- 3.1 ml/min per 100 gm wet weight of intestine. Net intestinal water and electrolyte fluxes were calculated by means of an isosmotic buffer that contained carbon-14 polyethylene glycol as a nonabsorbable volume marker. Viability of this isolated perfused ileal preparation was confirmed on the basis of light microscopy, oxygen consumption, and transmucosal potential difference measurements. Control experiments, without exogenous hormone infusion, resulted in a stable preparation with a basal secretory state. Intra-arterial serotonin at 2.5 micrograms/min (n = 10) significantly stimulated secretion of H2O, Na+, and Cl- (p less than 0.01). Intra-arterial substance P at 2.5 x 10(-1) micrograms/min (n = 7) significantly increased the secretion of H2O, Na+, and Cl- (p less than 0.02). The dose of serotonin was designed to yield serotonin levels that resembled those found circulating in patients with carcinoid syndrome. These data indicate that serotonin and substance P are potent secretagogues in a mammalian system, independent of their effect on mesenteric blood flow and in the absence of extra-intestinal hormonal and neural influences.

Animals↗
PubMed1988

The effect of calcium channel blockade on basal- and substance P-induced intestinal secretion.

Calcium plays a central role in modulating many physiologic events. We have investigated the role of calcium channel blockade in the control of basal (n = 6)- and substance P-stimulated (n = 6) intestinal transport in the isolated perfused rabbit ileum. Twenty-centimeter segments of ileum, harvested from New Zealand rabbits, were arterially perfused at 1.5 ml/min with an oxygenated modified Krebs buffer solution containing washed human red cells (Hct = 15-20%) and 2.5 mM Ca2+. The intestinal lumen was perfused at 2 ml/min with an isotonic solution containing 1.2 mM Ca2+ and [14C]PEG as a nonabsorbable volume marker. The infusion of verapamil (1 microgram/min) significantly reduced (P less than 0.05) the basal secretion of H2O, and Cl-. Verapamil prevented the secretory effect of substance P infused at 0.25 microgram/min. Intraarterial verapamil had no effect on vascular perfusion pressure. These data indicate that calcium channel blockade has significant effects on basal- and substance P-stimulated intestinal secretion and suggest that transmembrane calcium fluxes function as major determinants of basal- and secretagogue-stimulated intestinal transport.

Animals↗
PubMed1988

The effect of norepinephrine on intestinal transport and perfusion pressure in the isolated perfused rabbit ileum.

Norepinephrine (NE) is an autonomic neurotransmitter and a potent vasoactive agent, with putative effects on intestinal absorption and secretion. To characterize the effects of NE on intestinal water and ion transport, independent of changes in intestinal blood flow, we studied the effects of three doses of NE (0.1, 0.4, and 2.0 microgram/min) on the isolated, vascularly perfused rabbit ileum at a constant vascular perfusion rate. Twenty-centimeter segments of New Zealand white rabbit distal ileum (n = 21) were vascularly perfused at a fixed rate of 1.5 ml/min using a modified Krebs buffer solution (37 degrees C) containing washed human red blood cells with a hematocrit of 15-20%. The intestinal lumen was perfused at 2 ml/min with a warm buffered isotonic electrolyte solution containing 10 microCi [14C]PEG as a nonabsorbable volume marker. Net fluxes of H2O, Na+, and Cl- were calculated during 20-min basal, NE infusion, and recovery periods. Perfusion pressure was monitored continuously. NE caused statistically significant graded increases in vascular resistance, as reflected by perfusion pressure, with increasing doses. NE stimulated absorption of H2O, Na+, and Cl- with a less distinct response to increasing dose. These data suggest that the separate effects of NE on absorption and hemodynamics may be mediated through different pathways or different receptors in the intestine.

Animals↗
PubMed1988

Discrimination between alpha 1- and alpha 2-adrenergic receptors in the isolated perfused ileum.

Adrenergic control over intestinal homeostasis has been associated with changes in intestinal vascular resistance, motility, and transport. With the use of selective alpha-adrenergic agents, this study was designed to discriminate between the vascular and transport effects. Rabbit 20 cm ileal segments (n = 31) were vascularly perfused at a rate of 1.5 ml/min by means of a modified Krebs solution containing 15% to 20% red cells. The intestinal lumen was perfused with an isotonic solution containing carbon 14-polyethylene glycol as a nonabsorbable marker. Net fluxes of water and electrolytes were calculated during 20-minute basal, experimental, and recovery periods. Norepinephrine (mixed alpha 1- and alpha 2-agonist) significantly increased intestinal absorption and vascular resistance. Phenylephrine (alpha 1-agonist) significantly increased vascular resistance without altering transport. Clonidine (alpha 2-agonist) stimulated intestinal absorption without changing vascular perfusion pressure. Yohimbine (alpha 2-antagonist) prevented norepinephrine-induced absorption but had no effect on norepinephrine-induced increases in perfusion pressure. In this isolated perfused whole gut model, alpha 1-adrenergic stimulation was responsible for increases in vascular resistance, and alpha 2-adrenergic stimulation was responsible for increases in the absorption of water and electrolytes. The ability to discriminate between alpha 1- and alpha 2-effects has potential therapeutic implications in patients with malabsorption and diarrhea.

Adrenergic alpha-Agonists↗
PubMed1988

Peptide YY inhibits cholecystokinin-stimulated sphincter of Oddi activity in the prairie dog.

Peptide YY (PYY), a recently discovered gut peptide, has been shown to have a number of actions that are antagonistic to the effects of cholecystokinin. This study was designed to determine whether PYY would inhibit cholecystokinin-stimulated sphincter of Oddi activity in the prairie dog. In 12 prairie dogs PYY was infused intravenously at 1, 10, and 100 ng/kg/min, and arterial blood samples were obtained. A dose-response curve was obtained, with the 10 ng/kg/min dose producing serum levels of 725 pg/ml. In seven additional prairie dogs a side-hole, pressure-monitored perfusion catheter was passed into the duodenum through a choledochotomy and positioned in the sphincter of Oddi. A perfusion catheter was also placed in the gallbladder fundus. Sphincter of Oddi and gallbladder pressures were recorded before and during 20-minute infusions of cholecystokinin and then cholecystokinin plus PYY at 10 ng/kg/min. PYY significantly inhibited cholecystokinin-stimulated sphincter of Oddi phasic wave frequency (3.8 +/- 0.2 vs 3.3 +/- 0.4; p less than 0.05) and sphincter of Oddi motility index (26.2 +/- 4.3 vs 18.7 +/- 4.8; p less than 0.025) but did not affect the increase in gallbladder pressure induced by cholecystokinin. These findings are consistent with other known anticholecystokinin effects of PYY. We conclude that PYY may also inhibit sphincter of Oddi activity in the prairie dog by an anticholecystokinin effect, thus reducing flow through the sphincter.

Ampulla of Vater↗