The WAND local anesthetic delivery system: a more pleasant experience for anal anesthesia.

PURPOSE: The WAND is a computer-controlled local anesthetic delivery system. Its use has been proven to be more comfortable for dental patients. The purpose of this study is to explore its applicability to anal procedures. Our hypothesis is that the WAND will provide greater comfort during anesthesia delivery while achieving the same anesthetic effect as traditional syringe technique. METHODS: Twenty patients with painless anal pathology were randomized to receive anal anesthesia using either the WAND or traditional syringe technique to a randomly selected half of the anoderm (right or left). The opposite side was then anesthetized by the alternate method, allowing patients to act as their own control. Objective and subjective pain scores were obtained from the patient after each mode of delivery. An independent observer interpreted the patient's tolerance by giving a subjective pain score. The volume of anesthetic used was recorded. Adequacy of anesthesia was tested by a pinch test. RESULTS: Sixteen (80 percent) of the 20 patients preferred the use of the WAND. Objective and subjective pain scores per the patients and subjective pain scores per the observer were significantly lower for the WAND than for traditional syringe technique (P < 0.05). The mean volume of local anesthetic used with the WAND was 1.7 ml compared with 3.2 ml for traditional syringe technique (P < 0.005). Anesthesia achieved with the WAND was as good as that achieved with traditional syringe technique when the pinch test was used. CONCLUSION: The WAND is as effective as the traditional syringe technique in the delivery of anal anesthesia while providing a more comfortable experience for the patient.

Variations in treatment of rectal cancer: the influence of hospital type and caseload.

PURPOSE: Surgical options for the treatment of rectal cancer may involve sphincter-sparing procedures (SSP) or abdominoperineal resection (APR). We sought to examine variations in the surgical treatment of rectal cancer for a large, well-defined patient population and specifically to determine if differences exist in management and survival based on hospital type and surgical caseload. METHODS: The Cancer Surveillance Program database for Los Angeles County was used to retrospectively retrieve data on all patients who underwent SSP or APR for rectal adenocarcinoma between 1988 and 1992. RESULTS: A total of 2,006 patients with adenocarcinoma of the rectum underwent SSP or APR during the study period. Overall, 55 percent underwent SSP, and the remaining 45 percent underwent APR. Use of SSP remained relatively constant for each year of the five-year period. Substantial variability was seen in the use of SSP at various hospital types. For localized disease, this varied from as low as 52 percent at teaching hospitals to as high as 78 percent at hospitals approved by the American College of Surgeons (P = 0.067). To examine the role of caseload experience, hospitals were divided into those completing an average of five or fewer rectal cancer cases per year vs. those completing an average of more than five cases per year. For localized disease, hospitals with higher caseloads performed SSP in significantly more cases, 69 vs. 63 percent (P = 0.049). Survival was seen to be significantly improved for patients operated on at hospitals with higher caseloads, in cases of both localized and regional diseases (P < 0.001). CONCLUSION: Surgical choices in the treatment of rectal cancer may vary widely, even in a well-defined geographic region. Although the reasons for this variability are multifactorial, hospital environment and surgical caseload experience seem to have a significant role in the choice of surgical procedure and on survival.

Intra-abdominal abscesses following laparoscopic and open appendectomies.

Recent findings in a small number of studies have suggested a trend toward increased infectious complications following laparoscopic appendectomy. The purpose of the present review was to evaluate the incidence of postappendectomy intra-abdominal abscess formation following laparoscopic and open appendectomies. Using the surgical database of the Los Angeles County-University of Southern California Medical Center, we reviewed the records of all appendectomies performed at the center between March 1993 and September 1995. Incidental appendectomies as well as appendectomies in pediatric patients under the age of 18 years were excluded. A total of 2497 appendectomies were identified; indications for these procedures included acute appendicitis in 1422 cases (57%), gangrenous appendicitis in 289 (12%), and perforated appendicitis in 786 (31%). The intraoperative diagnosis made by the surgeon was used for classification. A two-tailed P value of <0.05 was considered significant. There was no significant difference in the rate of abscess formation between the groups undergoing open and laparoscopic appendectomies for acute and gangrenous appendicitis. In patients with perforated appendicitis, a total of 26 postappendectomy intra-abdominal abscesses occurred following 786 appendectomies for an overall abscess formation rate of 3.3%. Eighteen abscesses occurred following 683 open appendectomies (2.6%), six abscesses occurred following 67 laparoscopic appendectomies (9.0%), and the remaining two abscesses occurred following 36 converted cases (5.6%). For perforated appendicitis, however, there was a statistically significant increase in the rate of abscess formation following laparoscopic appendectomy compared to conventional open appendectomy (9.0% vs. 2.6%, P = 0.015). There was no significant difference in the rate of abscess formation between open vs. converted cases or between laparoscopic vs. converted cases. A comparison of the length of the postoperative hospital stay showed no significant difference between open and laparoscopic appendectomy for perforated appendicitis (6.1 days vs. 5.9 days). Laparoscopic appendectomy for perforated appendicitis is associated with a higher rate of postoperative intra-abdominal abscess formation without the benefit of a shortened hospital stay. Given these findings, laparoscopic appendectomy is not recommended in patients with perforated appendicitis.

Wound recurrence following laparoscopic colon cancer resection. Results of the American Society of Colon and Rectal Surgeons Laparoscopic Registry.

INTRODUCTION: Multiple case reports have suggested that laparoscopic resection of colon cancer may alter the pattern or incidence of cancer recurrence. All reports lack a significant denominator to evaluate the incidence of surgical wound recurrence. We hypothesized that wound recurrence incidence is not increased by laparoscopic resection of colon cancer. METHODS: A prospective registry was initiated under the auspices of The American Society of colon and Rectal Surgeons, American College of Surgeons, and Society of American Gastrointestinal Endoscopic Surgeons in 1992. Patients having laparoscopic colon resection were voluntarily entered and followed until June 1995. Recurrences were evaluated by the primary surgeon and reported to the registry. RESULTS: A total of 504 patients treated for cancer were identified in the registry. A minimum follow-up of one year was obtained for 480 of 493 evaluable patients (97.4 percent). Wound recurrence was identified in five patients (1.1 percent). Recurrence status was unknown in 18 patients (3.8 percent). CONCLUSION: Wound recurrence rates appear to be low. Although length of follow-up is limited, patterns of recurrence from previous studies suggest that 80 percent of recurrences should have occurred within one year. Given the limitations of a Phase II study, the hypothesis that recurrence rate is low is supported. However, prospective randomized trials are needed to establish if any difference in wound recurrence rates after laparoscopic or open resection of colorectal cancer exists.

Inferior vena caval blood flow and cardiac hemodynamics during carbon dioxide pneumoperitoneum.

BACKGROUND: The effects of carbon dioxide pneumoperitoneum on venous return and cardiac hemodynamics during laparoscopic surgery were studied. METHODS: Twelve adult pigs underwent placement of an electromagnetic flow meter across the infrarenal vena cava (IVC) as well as placement of Swan Ganz and arterial monitoring catheters. Measurements of the flow through infrarenal IVC, cardiac output (CO), pulmonary capillary wedge pressure (PCWP), mean arterial pressure (MAP), and heart rate were recorded at baseline, 5 and 60 min following insufflation to 15 mmHg with CO2, and 5 min following desufflation. Stroke volumes and systemic vascular resistance (SVR) were calculated as well. RESULTS: Flow through the IVC dropped by 24 and 31% at 5 and 60 min (p = 0.03 and 0.02, respectively). Paradoxically, cardiac output rose by 14 and 28% at 5 and 60 min (p = 0.03 at 60 min). Central venous and pulmonary capillary wedge pressures rose transiently by 35 and 36% at 5 min before returning to baseline (p < 0.01). Mean arterial pressure and heart rate remained relatively constant during insufflation. Systemic vascular resistance diminished from 938 dynes/cm/s prior to insufflation to its nadir at 60 min of 650 dynes/cm/s (p < 0.01). CONCLUSIONS: These observations suggest potentially complex interactions between the mechanical and systemic effects of the CO2 pneumoperitoneum on venous return. Transient elevations in cardiac filling pressures occur by an unknown mechanism, and a generalized enhanced inotropic state mediated via increased sympathetic outflow is observed in this hypercapnic anesthetized animal model.

Basal and meal-stimulated colonic absorption.

PURPOSE: Few quantitative experiments evaluating colonic absorption of water and electrolytes have been performed using an awake, conscious animal model. The purpose of these experiments was to develop this type of model and evaluate both basal and meal-stimulated colonic absorption of water and electrolytes. METHODS: Canine Thiry-Vella fistulas were created using a 20 cm segment of distal colon under general anesthesia. Colonic absorption studies were performed using infusion of the Thirty-Vella fistulas with a buffer solution containing [14C]polyethylene glycol. Electrolyte analysis and concentration of radioactivity in the effluent were obtained and used to calculate the net flux of water, sodium, and chloride. Each study consisted of an one-hour basal period and a three-hour experimental period divided into two groups. Group 1 received no meal. Group 2 orally ingested a mixed meal at the completion of the basal hour. RESULTS: In the basal state, water and electrolytes are absorbed from the distal colon at a steady and constant rate. An orally ingested meal produces a statistically significant increase in the rate of absorption, independent of direct colonic luminal contact with the nutrients of the meal given. CONCLUSIONS: These studies demonstrate an in vivo quantitative and qualitative measure of mammalian colonic water and electrolyte absorption. An increase in absorption rate occurs in response to a meal that is probably the result of an unidentified neural or humoral signal.

Intraabdominal abscesses following laparoscopic and open appendectomies.

BACKGROUND: The purpose of this review was to evaluate the incidence of postoperative intraabdominal abscess formation following laparoscopic and open appendectomies. METHODS: The current study retrospectively examines appendectomies performed during the period from January 1993 to July 1994. Excluded were cases which were started laparoscopically but converted to open procedures. There were 1,287 cases identified; 597 were perforated (46%), 114 were gangrenous (9%), and 576 were acute (45%). These diagnoses represent intraoperative diagnoses. RESULTS: Of the 576 appendectomies for acute appendicitis, 64 (11%) were performed laparoscopically. There were four intraabdominal abscesses (0.7%), all occurring after open procedures. Of the 114 appendectomies for gangrenous appendicitis, 16 (14%) were done laparoscopically. There were two postoperative abscesses (1.8%), one following an open and one following a laparoscopic procedure. There was no significant difference in abscess rate between laparoscopic and open appendectomies for either acute or gangrenous appendicitis. Of the 597 appendectomies for perforated appendicitis, 28 (5%) were done laparoscopically. There were 19 postoperative abscesses in the whole group, accounting for a 3.2% abscess rate. Sixteen abscesses occurred after open appendectomies and three occurred after laparoscopic appendectomies (2.9% vs 11%, P = 0.054). The preoperative diagnosis was incorrectly identified as acute appendicitis in 95 cases subsequently found to have perforated appendicitis; there was only 1 postoperative abscess in this group. There was no difference in postoperative stay in the open vs laparoscopic group (6.3 days vs 6.1 days). CONCLUSIONS: We found no significant difference in the rate of postoperative intraabdominal abscess formation between laparoscopic and open appendectomies in cases of acute or gangrenous appendicitis. However, laparoscopic appendectomy for perforated appendicitis was associated with an important trend toward a higher rate of postoperative intraabdominal abscess formation than open appendectomy. This observation calls for closer prospective scrutiny of laparoscopic appendectomy in the setting of perforated appendicitis.

Surgical outcome in acquired immunodeficiency syndrome patients with non-Hodgkin's lymphoma of the gastrointestinal tract.

PURPOSE: Incidence of non-Hodgkin's lymphoma (NHL) has shown a dramatic increase, concurrent with the epidemic of acquired immunodeficiency syndrome (AIDS). In terms of surgical intervention, management of the patient with AIDS-NHL remains unclear. Purpose of this paper was to determine the role and outcome of surgical intervention in patients with AIDS-NHL of the gastrointestinal (GI) tract. METHODS: Data were obtained by retrospective chart review. RESULTS: From 1980 to 1993, charts of 22 patients with diagnosis of AIDS-NHL of the GI tract who underwent either biopsy or surgical procedure were reviewed. All patients were male, with a mean age of 35.7 years. Sixty-seven biopsies were performed in the 22 patients identified. No morbidity or mortality was associated with any of the biopsy procedures. Major intra-abdominal operations were performed in eight patients, including seven who underwent primary resections of lymphomas. Mean survival for the group as a whole was 18 months, although that for the seven patients undergoing resection was 20.4 months. CONCLUSIONS: Diagnosis of AIDS-NHL of the GI tract should not discourage performance of otherwise appropriate surgical procedures.

Laparoscopic-assisted colectomy learning curve.

PURPOSE: The purpose of this paper is to establish the number of cases necessary to master laparoscopic removal of the left or right colon. METHODS: Data were obtained by chart review and by individually completed questionnaires. RESULTS: A total of 144 laparoscopic-assisted or intracorporeal right or left hemicolectomies were completed by four surgeons at separate institutions. Questionnaires were completed by each surgeon for each sequential hemicolectomy, and data concerning the type of surgery and total operating time were recorded. Times were plotted to diagram individual learning curves for each surgeon, and data grouping methods were used to determine the curve for each surgeon as well as for the combined data base. Learning was said to have been completed when the surgeon's operative time reached a low point and subsequently did not vary by more than 30 minutes. A total of 78 right colectomies and 66 left colectomies were completed by the group. Respectively, each surgeon appeared to learn the procedure after 16, 21, 11, and 6 cases. When the entire database was analyzed as a whole, it was shown that between 11 and 15 completed colectomies were needed for learning, after which operative times remained relatively stable. CONCLUSIONS: This analysis, using total operative time as an indication of learning, shows that approximately 11 to 15 completed laparoscopic colectomies are needed to comfortably learn this procedure.

Laparoscopy and colon cancer. Is the port site at risk? A preliminary report.

PURPOSE: To quantify the magnitude of the risk for port/extraction site recurrence of laparoscopically resected colon cancer in a defined study population. METHODS: The data from a prospective laparoscopic bowel surgery registry was used to identify cases of colon cancer that were resected laparoscopically, with a minimum follow-up of 1 year. A questionnaire was sent to the surgeons who performed the procedures. RESULTS: A total of 252 cases were identified from the registry. Questionnaires were returned in 208 of those cases, a response rate of 82.5%. Three cases of port or extraction site recurrence were noted, two of them associated with diffuse peritoneal carcinomatosis. All the patients had a Dukes' stage C tumor at the time of initial surgery. CONCLUSIONS: The incidence of port/extraction site recurrence following laparoscopic colon cancer surgery is low. All the recurrences were in patients with Dukes' stage C tumors, and there was diffuse peritoneal carcinomatosis in two of the three cases, suggesting that port/extraction site recurrence may be attributable to the advanced nature of the disease rather than the laparoscopic technique. Longer follow-up and more cases are required to confirm these findings.

Meal-stimulated canine jejunal ionic absorption. Influence of mucosal neural blockade.

The oral ingestion of a meal or the delivery of nutrients directly to the stomach or duodenum stimulates water and ion absorption from the proximal jejunal lumen. To further investigate this phenomenon, this study tested two hypotheses: (1) direct jejunal nutrient delivery stimulates jejunal absorption, and (2) the signal for jejunal absorption requires intact enteric neurotransmission and will therefore be altered by mucosal neural blockade with the local anesthetic bupivacaine. Intestinal absorption studies (N = 52) were performed on eight dogs with 25-cm jejunal Thiry-Vella fistulas (TVF) and feeding jejunostomies. Luminal perfusion with [14C]PEG was used to calculate TVF absorption of H2O, Na+, and Cl-. Six groups were randomly studied over 4 hr. Each group incorporated a basal hour, a TVF or jejunostomy treatment hour, and an oral (groups 1 and 3) or a jejunal (groups 4 and 6) meal stimulus. The oral and jejunal meals were isocaloric and of identical composition. Groups 1-3 had saline (as a control) or 0.75% bupivacaine applied to the lumen of the TVF. Groups 5 and 6 had 0.75% bupivacaine application to the feeding jejunostomy. Both the oral and the jejunal meal stimuli resulted in a significant proabsorptive response in the TVF. TVF bupivacaine reduced basal absorption but did not diminish the meal-induced proabsorptive response. Treatment of the jejunostomy with bupivacaine caused no change in basal or postmeal absorption in the TVF.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical experience with pancreatic islet-cell tumors.

OBJECTIVE: To review the surgical management of pancreatic islet-cell tumors, with attention to preoperative localization, surgical therapy, and postoperative survival. DESIGN: Consecutive case series of patients treated surgically for pancreatic islet-cell tumor. SETTING: The Johns Hopkins Hospital, a large teaching hospital in Baltimore, Md, serving both as a primary and tertiary care center. PATIENTS: Thirty-seven patients with pancreatic islet-cell tumors treated surgically between 1979 and 1990. MAIN OUTCOME MEASURES: Success of preoperative localization studies, types of operations performed, and postoperative survival. RESULTS: Preoperative computed tomography correctly localized the tumor in 20 of 34 patients (59%); angiography in 21 of 28 patients (75%), and the combination of computed tomography and angiography in 23 of 28 patients (82%). Benign islet-cell tumors were found in 19 patients, and malignant tumors in 18 patients. Twenty-four patients (65%) had functional tumors. The proportion of patients with nonfunctioning tumors increased from 0% before 1984, to 43% from 1985 to 1990. Surgical therapy was curative in 27 patients and palliative in 10. The most commonly performed operative procedures were tumor enucleation (11 patients [30%]), distal pancreatectomy (10 patients [27%]). There was no operative mortality. The actuarial survival at 40 months was 100% in patients with benign tumors and significantly lower (66%) in patients with malignant tumors. CONCLUSIONS: This experience from a single institution underscores the role of preoperative localization studies and appropriate surgical management of these rare tumors.

Site specificity and meal stimulation of the intestinal absorption of water, electrolytes, and bile acids.

Ileal water and electrolyte absorption exceed jejunal absorption in both the basal and meal-stimulated states. The purposes of these experiments were to determine: (1) if luminal bile acids alter basal or meal-stimulated intestinal absorption, and (2) if there is site specificity or meal stimulation of intestinal bile acid absorption. Twenty-five centimeters of canine proximal jejunal and distal ileal Thiry-Vella fistulas were constructed. Simultaneous jejunal and ileal absorption studies (n = 88) were performed with a luminal perfusate containing polyethylene glycol labeled with radioactive carbon-14 to calculate the absorption of water, electrolytes, and the bile acid taurocholate (TC). In group 1, there was no TC in the luminal perfusate, whereas in group 2, 10 mM of TC was present in the luminal perfusate. Half of the observations were performed after a meal stimulus, which consisted of an orally ingested, 480-kcal mixed nutrient meal. Intraluminal TC did not affect basal or meal-stimulated water or electrolyte absorption. In both the basal and meal-stimulated states, ileal absorption of water, electrolytes, and TC significantly exceeded jejunal absorption (p < 0.05). A meal significantly stimulated water and electrolyte absorption in both the jejunum and ileum, but it stimulated absorption of TC in the ileum only (p < 0.05). Intraluminal TC does not alter basal or meal-stimulated intestinal water and electrolyte absorption. A meal stimulates increased water and electrolyte absorption in both the jejunum and the ileum, but it stimulates bile acid absorption in the ileum only. Bile acid absorption is site specific and responsive to a meal stimulus.

Small bowel origin and calorie dependence of a signal for meal-induced jejunal absorption.

The ingestion of a meal stimulates the absorption of water and electrolytes from the small intestine independent of the cephalic or gastric phases of digestion. This study tested two hypotheses: (1) the jejunum is the origin of a postmeal proabsorptive signal and (2) the magnitude of the proabsorptive response is dependent on the caloric content of the meal stimulus. Twenty-five-centimeter proximal canine jejunal Thiry-Vella fistulas and feeding jejunostomies were constructed under general anesthesia. Jejunal absorption studies (n = 50) were performed by luminal perfusion of the Thiry-Vella fistula with 14C-polyethylene glycol (PEG) to calculate fluxes of water and electrolytes. Five groups were studied: (1) CONTROL: no meal, (2) 240 kcal oral meal, (3) 480 kcal oral meal, (4) 240 kcal jejunal meal, and (5) 480 kcal jejunal meal. Independent of the route of delivery (i.e., oral vs. jejunal), each meal stimulus significantly increased jejunal water and electrolyte absorption (p < 0.05). The magnitude of the proabsorptive response increased significantly as the calories delivered increased (p < 0.05). These data support the hypothesis that a proabsorptive signal responsible for meal-induced jejunal absorption originates from, or distal to the jejunum and suggest that intestinal chemoreceptors or osmoreceptors participate in the generation of the proabsorptive signal.

Meal-stimulated canine jejunal ionic absorption. Effect of direct jejunal meal delivery and premeal intravenous hydration.

The ingestion of a meal stimulates water and ion absorption from the small intestine. The administration of nutrient substances directly to the small bowel can cause dumping symptoms, with intraluminal fluid accumulation and relative systemic hypovolemia. This study compared the effect of oral versus direct jejunal meal delivery on jejunal water and ion absorption, with and without premeal intravenous saline infusion. Jejunal absorption studies (N = 40) were performed on dogs with 25 cm proximal jejunal Thiry-Vella fistulas and feeding jejunostomies. Luminal perfusion with [14C]PEG was used to calculate fluxes of water and electrolytes. Five groups were randomly studied: (1) intravenous 0.9% saline alone, (2) oral meal alone, (3) intravenous 0.9% saline plus oral meal, (4) jejunal meal alone, and (5) intravenous 0.9% saline plus jejunal meal. Hydration status was assessed hourly by measurement of hematocrit. Water and electrolyte absorption was significantly stimulated by both oral and jejunal meal delivery (P less than 0.01). Intravenous saline hydration significantly reduced the hematocrit (P less than 0.05) but did not alter the proabsorptive response to an oral or jejunal meal. In conclusion, a postprandial signal for proximal jejunal water and electrolyte absorption was stimulated equally by orally or jejunally administered nutrients and was not affected by premeal hydration. These data support the hypothesis that the proabsorptive signal that stimulates water and ion absorption is an enteroenteric phenomenon originating from the small intestine, without implicating pathophysiologic events such as hypovolemia or dumping.

Site-specific variations in basal and meal-stimulated intestinal absorption.

The ingestion of a meal increases water and electrolyte absorption in the proximal jejunum. The purpose of these experiments was to elucidate any site-specific variations in intestinal absorption, comparing jejunum to ileum, in both the basal and the meal-stimulated states. Twenty-five-centimeter proximal jejunal and distal ileal Thirty-Vella fistulae were constructed in four dogs. Simultaneous jejunal and ileal absorption studies were performed using [14C]PEG to calculate net absorption of water and electrolytes. Two groups were studied: in Group 1 no meal was ingested, while in Group 2, the animals ingested a mixed meal. Each study consisted of a 1-hr basal period and a 3-hr experimental period. In the basal state ileal absorption significantly exceeded jejunal absorption (P less than 0.0001). The ingestion of mixed meal significantly increased water and electrolyte absorption in both the jejunum and the ileum, (P less than 0.001), with the magnitude of meal-stimulated ileal absorption significantly exceeding the magnitude of meal-stimulated jejunal absorption (P less than 0.001). These studies demonstrate distinct site specific variations in intestinal water and electrolyte absorption in both the basal and the meal-stimulated states.

Meal-induced jejunal absorption requires intact neural pathways.

A signal for meal-induced absorption originates from the small intestine and is transmitted to a luminally excluded segment of the proximal jejunum (Thiry-Vella [TV] fistula). Using intraluminal topical anesthesia with oxethazaine, this study assessed the role of intestinal neural pathways in basal and postprandial jejunal water and electrolyte absorption. Studies (n = 45) were performed on dogs with 25-cm proximal jejunal TV fistulae and feeding jejunostomies, using luminal perfusion with 14C-polyethylene glycol. The animals were randomized into five study groups: (1) jejunostomy oxethazaine alone, (2) jejunostomy water and jejunal meal, (3) jejunostomy oxethazaine and jejunal meal, (4) TV fistula water and jejunal meal, and (5) TV fistula oxethazaine and jejunal meal. The jejunal meal significantly increased TV fistula absorption, whereas oxethazaine significantly reduced basal absorption when administered via the TV fistula and postprandial absorption when administered via the jejunostomy (p less than 0.05). TV fistula oxethazaine did not diminish the magnitude of postprandial absorption. We conclude that intact intestinal neurotransmission is necessary for maintenance of the normal basal absorptive state of the proximal jejunum and for the generation of a normal meal-stimulated proabsorptive signal from the small intestine. A nonneural mechanism appears to be of predominant importance in transmitting the proabsorptive signal from the intact gastrointestinal tract to the TV fistula.

Neuropeptide Y-induced intestinal absorption: mediation by alpha 2-adrenergic receptors.

In the intestine neuropeptide Y (NPY) is contained in sympathetic nerves, in neuroendocrine cells of the mucosa, and in neurons of the enteric plexuses. After a meal is ingested the concentration of NPY in the blood rises, and intestinal absorption of water and ions increases. We have recently demonstrated a proabsorptive effect of NPY on water and ion transport in the small intestine. The current experiments tested the hypothesis that the alpha 2-adrenergic receptor mediates NPY-induced intestinal absorption. Rabbit ileal segments (n = 35) were harvested and arterially perfused ex vivo. The intestinal lumen was perfused with an isotonic solution containing carbon 14-labeled polyethylene glycol. Net fluxes of H2O, Na+, and Cl- were calculated for three 20-minute periods: basal, drug infusion, and recovery. Five groups were randomly studied: (1) NPY (500 pmol/min); (2) terazosin (1 microgram/min, alpha 1-adrenergic receptor antagonist); (3) NPY + terazosin; (4) yohimbine (1 microgram/min, alpha 2-adrenergic receptor antagonist); and (5) NPY + yohimbine. The infusion of NPY alone caused a significant (p less than 0.05) proabsorptive response for H2O, Na+, and Cl-. Neither terazosin nor yohimbine alone had a significant effect on the transport state of the intestine. Yohimbine, but not terazosin, completely prevented the NPY-induced proabsorptive response. These data support the hypothesis that the proabsorptive effect of NPY is mediated by the alpha 2-adrenergic receptor system.

Neuropeptide Y is a proabsorptive agent in the small intestine.

In the mammalian intestine neuropeptide Y (NPY) is contained in sympathetic nerves and in enteric neurons originating from the myenteric and submucosal plexuses. This study investigated the role of NPY on small intestinal ionic transport using an isolated intestinal preparation. Rabbit ileal segments (n = 12) were harvested and arterially perfused with a nonrecirculating oxygenated sanguinous solution. The intestinal lumen was perfused with an isotonic solution containing [14C]PEG. Net fluxes of H2O, Na+, and Cl- were calculated for three 20-min periods: basal, drug infusion, and recovery. Two groups were studied: (1) NPY 50 pM/min (n = 6) and (2) NPY 500 pM/min (n = 6). NPY at 50 pM/min caused modest absorption and at 500 pM/min yielded a significant proabsorptive effect (P less than 0.05) for H2O, Na+, and Cl- during the drug infusion period. There were no significant changes in vascular perfusion pressure in either group. These data demonstrate a significant proabsorptive effect of NPY on water and electrolyte transport in the isolated perfused ileum. This proabsorptive effect occurs at a constant arterial blood flow and without alteration in perfusion pressure, supporting a direct effect of NPY on intestinal ionic transport.

Direct proabsorptive effect of octreotide on ionic transport in the small intestine.

Somatostatin is widely distributed within the nervous system and the gastrointestinal tract. Gastrointestinal actions of somatostatin include inhibition of hormone release, reduction of pancreatic secretion, inhibition of motility, and reduction of blood flow. The purpose of this study was to investigate the role of somatostatin and its analogue octreotide on water and electrolyte transport in the small intestine. Rabbit ileal segments (n = 17) were harvested and arterially perfused ex vivo with a nonrecirculating oxygenated sanguineous solution. The lumen was perfused with an isotonic solution containing carbon 14-labeled polyethylene glycol. Net fluxes of water, Na+, and Cl- were calculated for three 20-minute periods designated basal, drug infusion, and recovery. Three groups were studied: somatostatin at 10(-6) mol/L (n = 5), somatostatin at 10(-5) mol/L (n = 5), and octreotide at 10(-5) mol/L (n = 7). Somatostatin at 10(-5) mol/L yielded a proabsorptive effect on the flux of water and electrolytes. Octreotide at 10(-5) mol/L caused a significant (p less than 0.05) proabsorptive response in the fluxes of water, sodium, and chloride during the period of drug infusion, which returned to basal secretory levels during the recovery period. This proabsorptive effect occurred without alterations in vascular resistance and necessarily was independent of systemic hormone interaction, supporting a direct effect of octreotide on intestinal ionic transport.