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Improvement in survival of mice with proximal small bowel obstruction treated with octreotide
Improvement in Survival of Mice With Proximal Small Bowel Obstruction Treated With Octreotide George K. Gittes,
MD,
M. Tim Nelson,
MD,
Haile T. Debas,
Small bowel obstruction is a common disorder in surgical practice. The major morbidity of bowel obstruction relates to intestinal distension and iscbemia. We hypothesized that octreotide, a potent inhibitor of gut secretion, would reduce mortality in a mouse model of lethal small bowel obstruction. C57 mice were anesthetized with urethane and prepared with either proximal jejunal or distal ileal obstruction. After 8 hours, surviving mice were randomized to receive either octreotide ( 100 &kg) or saline subcutaneously every 8 hours. Octreotide significantly improved survival in mice with proximal obstruction by life table analysis. Mean survival increased from 31 f 3 to 41 f 4 hours. In distal obstruction, octreotide treatment resulted in a trend towards improved survival; however, this trend failed to reach statistical significance by life table analysis. The improvement in survival in this mouse model suggests that octreotide may be a valuable adjunct in the treatment of patients with small bowel obstruction.
MD,
Sean J. Mulvihill,
MD, fan Francisco, California
mall bowel obstruction is a significant health prob lem in the United States, accounting for 300,000 S operations annually [I]. Currently, optimal therapy involves nasogastric suction to remove intraluminal fluid and air, thus decreasing bowel distension. In patients with partial obstruction, reduction of bowel distension with nasogastric suction often resolves the obstruction without surgery. Pharmacologic reduction of gut secretion would be predicted to have similar benefit. Somatostatin is a cyclic tetradecapeptide originally isolated from the hypothalamus [2]. It has been shown to have potent inhibitory effects on the gut. Known actions include inhibition of gastric, pancreatic, biliary, and intestinal secretion, inhibition of gut peptide release, inhibition of bowel motility, and antitrophic effects [3]. Additionally, in some experimental models, somatostatin increases intestinal absorption of water and sodium [4]. These properties make somatostatin a potentially useful candidate for pharmacologic reduction of intestinal fluid in the setting of obstruction. In a preliminary study, somatostatin inhibited fluid accumulation, intestinal distension, and mucosal ischemia in a rabbit model of closed-loop ileal obstruction [5]. Unfortunately, naturally occurring somatostatin is impractical for clinical use because of its very short half-life [q. Octreotide, a longacting somatostatin analogue, is available for human use in the treatment of patients with metastatic, symptomatic carcinoid tumors and VIPomas [ 71. It retains the inhibitory actions of somatostatin on gut secretion [8-101. We hypothesized that octreotide would prolong survival in an anesthetized, mouse model of lethal small bowel obstruction. MATERIALS AND METHODS
From the Department of Surgery, University of California, San Francisco, San Francisco, California. Requests for reprints should be addressed to Sean J. Mulvihill, MD, Department of Surgery (U- 122), University of California, San Francisco, 533 Pamassus Avenue, San Francisco, California 94143-0788. Presented as a poster paper at the 32nd Annual Meeting of the society for Surgery of the Alimentary Tract, New Orleans, Louisiana, May 20-22,199l.
Male C57-strain mice (mean weight: 20 g) from Bantin and Kingman (Fremont, CA) were anesthetized with urethane (1.6 g/kg intraperitoneal). Mice remained anesthetized for the duration of the experiment. Through a midline laparotomy, either the proximal (ligament of Treitz) or distal (1 cm proximal to the ileocecal valve) bowel was completely occluded with suture. The laparotomy was closed in one layer. Mice were kept warm with heating blankets. In order to simulate the clinical condition, treatment was not initiated until 8 hours after the creation of the obstruction. After the initial 8 hours, all surviving mice were randomized to receive subcutaneous injections of either 2 mL of normal saline (control) or 2 mL of saline containing octreotide acetate (100 rg/kg) every 8 hours. Octreotide acetate was donated by the Sandoz Corporation (East Hanover, NJ). These studies were approved by the Committee on Animal Research of the University of California, San Francisco, and conformed with National Institutes of Health guidelines [I I].
THE AMERICAN JOURNAL OF SURGERY
VOLUME 163 FEBRUARY 1992
231
% Survival loom
60
0
10
20
30 40 50 60 70 TIME (hrs. after surgery)
.-.... Octreotide
+
60
QO 100
lo
Control
significantiypfoimged survival.
A total of 160 mice were studied. Survival was recorded to the nearest 8 hours. Data is presented as mean f standard error of the mean @EM). Where appropriate, confidence intervals are given. Comparison of survival in treated and control groups was carried out in three ways. Initially, life table analysis was used to compare survival curves over the entire experiment. Secondly, mean survival times were compared by unpaired t-test. Thirdly, the proportion of mice alive in each group at 36 hours was analyzed by chi square. RESULTS Proximal obstruction:
Proximal jejunal obstruction at the level of the ligament of Treitz was created in 80 mice. Of these, 26 died within 8 hours and were not studied. The remaining 54 mice were randomized to treatment and control groups. Survival curves over time are shown in Figure 1. Octreotide treatment delayed death significantly by life table analysis. Mean survival was 41 f 4 hours with octreotide treatment versus 3 1 f 3 hours in control mice (p = 0.03 1 by unpaired t-test). The 95% confidence interval for the difference between mean survival times was 0.6 to 19.4 hours. At 36 hours after the creation of obstruction, 11 of 27 treated mice and 4 of 27 control mice were alive (p = 0.068 by chi square). The 95% confidence interval for the differences in proportions surviving at 36 hours was 0.02 to 0.50. Distal obstruction: Distal obstruction 1 cm proximal to the ileocecal valve was created in 80 mice. After 8 hours, 47 mice were alive for randomization. Of these, 23 were assigned to octreotide treatment and 24 to saline control. Survival over time is shown in Figure 2. Life table analysis showed a trend towards improved survival that did not reach statistical significance. Mean survival was 60 f 5 hours in the octreotide treatment group versus 54 i 4 hours in the control group (p = 0.40 by unpaired ttest). The 95% confidence interval for the difference be tween mean survival times was -8.15 to 20.15 hours. The proportion of mice surviving 36 hours with distal obstruction was similar in the two groups (19 of 23 octreotide versus 20 of 24 control). The proportion of mice surviving THE AMERICAN JOURNAL OF SURGERY
20
30 40 50 60 70 TIME (hrs. after surgery)
--.---. Octreotide
F@re 1. Swvivai in mice with proximai jejunai obstrwtkm treated with ~ctreotide (n = 27) or saline control(n = 27). Octreotide
232
0
-k
60
90
100
Control
Figure 2. Wvlvai in mice with distal iieal cMruction treated with 0ctreoWe (n = 23) or saline cmtroi (n = 24). No signifkant diffemnces in suvivai were noted, atltmtgh there was a trend towards benefit with OcbOtide treatment.
64 hours in the octreotide treatment group was 10 of 23 compared with 6 of 24 controls (p = 0.319, 95% confrdence interval -0.091 to 0.451). COMMENTS
In this study, the experimental model was complete small bowel obstruction in mice that was uniformly fatal. We chose to study a well-defined end-point, time of death, rather than more subtle parameters, such as bowel distension. In these studies, mice with proximal small bowel obstruction treated with octreotide showed a statistically significant prolongation in survival time compared with mice receiving saline. The mice prepared with distal small bowel obstruction showed a similar tendency toward longer survival when treated with octreotide, although the results did not reach statistical significance. The relatively small sample size in our study may not have allowed identification of a true difference between groups. Three mechanisms likely explain the improvement in the course of small bowel obstruction by octreotide in these mice. First, octreotide inhibits secretion from the gastric fundus, pancreas, and small bowel [8-101. These secretions add to the intraluminal volume. In a vicious cycle, small bowel distension further stimulates intestinal epithelial secretion [ 121. Thus, inhibition of gut secretion is a logical mechanism to exploit in the treatment of bowel obstruction. A second potentially beneficial action of octreotide in intestinal obstruction lies in its effects on water and sodium absorption. Dharmsathaphorn et al [4] demonstrated stimulation of sodium and chloride absorption by somatostatin in rabbit ileum in vitro. These lindings have been confirmed with octreotide [8]. A third potential mechanism of action of octreotide is its inhibition of gut hormone release. Vasoactive intestinal polypeptide (VIP) release, for example, is markedly inhibited by octreotide [fl. This is a part of the rationale for treatment of severe diarrhea in VIPoma patients with octreotide. It has been suggested that release of VIP plays a role in the pathophysiology of small bowel obstruction [13]. Although our experimental model was complete small
VOLUME 163 FEBRUARY 1992
bowel obstruction, the potential clinical usefulness of octreotide is in a different setting. Nearly all patients with complete bowel obstruction require surgical intervention. However, many patients with incomplete obstruction resolve with nasogastric suction and intravenous fluid therapy alone. This latter group of patients is the most likely to benefit from the addition of octreotide to their therapeutic regimen. Other patients who may benefit from octreotide as an adjunct to therapy are those in whom surgical intervention is undesirable. Examples include patients with obstruction due to carcinomatosis or in the early postoperative period. The basic treatment of small bowel obstruction has not changed significantly in 50 years. The data from this and previous studies point to the somatostatin analogue, octreotide, as a promising candidate as a pharmacologic adjuvant to standard therapy. Further studies, including controlled trials in patients with small bowel obstruction, are needed to demonstrate clinical efficacy. REFJWzNcEs 1. Welch JP. General considerations and mortality. In: Welch JP, editor. Bowel obstruction. Differential diagnosis and clinical management. Philadelphia: WB Saunders, Co., 1990: 59-95. 2. Brazeau P, Vale W, Burgus R, ef al. Hypothalamic polypeptide that inhibits the secretion of immunoreactive growth hormone. Science 1973; 179: 77-9. 3. Mulvihill S, Pappas TN, Passaro E Jr., Debas HT. The use of somatostatin and its analogs in the treatment of surgical disorders.
Surgery 1986; 100: 467-76. 4. Dharmsathaphom K, Binder HJ, Dobbins JW, Leo L. Somatostatin stimulates sodium and chloride absorption in the rabbit ileum. Gastroenterology 1980; 78: 1559-65. 5. Mulvihill SJ, Pappas TN, Fonkalsrud EW, Debas HT. The effect of somatostatin on experimental intestinal obstruction. Ann Surg 1988; 207: 169-73. 6. Seal A, Yamada T, Debas HT, et al. Somatcstatin-14 and -28: clearance and potency on gastric function in dogs. Am J Physiol 1982; 243: G97-102. 7. Gorden P, Comi RJ, Maton PN, Go VLW. Somatostatin and somatcstatin analogue (SMS 201-995) in treatment of hormone secreting tumors of the pituitary and gastrointestinal tract and nonneoplastic diseases of the gut. Ann Intern Med 1989; 110: 35-50. 8. Roberts WG, Fedorak RN, Chang EB. In uitro effects of the long-acting somatcctatin analogue SMS 201-995 on electrolyte transport by the rabbit ileum. Gastroenterology 1988; 94: 1343-50. 9. Williams ST, Woltering EA, G’Dorisio TM, Fletcher WS. Effect of octreotide acetate on pancreatic exocrine function. Am J Surg 1989; 157: 459-62. 10. Whitehouse I, Beglinger C, Rultimann G, Gyr K. Inhibition of pentagastrin-stimulated acid secretion after subcutaneous administration of a new somatostatin analogue. Gut 1986; 27: 141-6. 11. Guide for the Care and Use of Laboratory Animals. NIH Publication No. 86-23. National Institutes of Health, Bethesda, Maryland, 1985. 12. Caren JF, Meyer JH, Grossman MI. Canine intestinal secretion during and after rapid distension of the small bowel. Am J Physiol 1974; 227: 183-8. 13. Basson MD, Fielding LP, Bilchik AJ, et al. Does vasoactive intestinal polypeptide mediate the pathophysiology of bowel ob struction? Am J Surg 1989; 157: 109-115.
THE AMERICAN JOURNAL OF SURGERY
VOLUME 163 FEBRUARY 1992
233
MD,
M. Tim Nelson,
MD,
Haile T. Debas,
Small bowel obstruction is a common disorder in surgical practice. The major morbidity of bowel obstruction relates to intestinal distension and iscbemia. We hypothesized that octreotide, a potent inhibitor of gut secretion, would reduce mortality in a mouse model of lethal small bowel obstruction. C57 mice were anesthetized with urethane and prepared with either proximal jejunal or distal ileal obstruction. After 8 hours, surviving mice were randomized to receive either octreotide ( 100 &kg) or saline subcutaneously every 8 hours. Octreotide significantly improved survival in mice with proximal obstruction by life table analysis. Mean survival increased from 31 f 3 to 41 f 4 hours. In distal obstruction, octreotide treatment resulted in a trend towards improved survival; however, this trend failed to reach statistical significance by life table analysis. The improvement in survival in this mouse model suggests that octreotide may be a valuable adjunct in the treatment of patients with small bowel obstruction.
MD,
Sean J. Mulvihill,
MD, fan Francisco, California
mall bowel obstruction is a significant health prob lem in the United States, accounting for 300,000 S operations annually [I]. Currently, optimal therapy involves nasogastric suction to remove intraluminal fluid and air, thus decreasing bowel distension. In patients with partial obstruction, reduction of bowel distension with nasogastric suction often resolves the obstruction without surgery. Pharmacologic reduction of gut secretion would be predicted to have similar benefit. Somatostatin is a cyclic tetradecapeptide originally isolated from the hypothalamus [2]. It has been shown to have potent inhibitory effects on the gut. Known actions include inhibition of gastric, pancreatic, biliary, and intestinal secretion, inhibition of gut peptide release, inhibition of bowel motility, and antitrophic effects [3]. Additionally, in some experimental models, somatostatin increases intestinal absorption of water and sodium [4]. These properties make somatostatin a potentially useful candidate for pharmacologic reduction of intestinal fluid in the setting of obstruction. In a preliminary study, somatostatin inhibited fluid accumulation, intestinal distension, and mucosal ischemia in a rabbit model of closed-loop ileal obstruction [5]. Unfortunately, naturally occurring somatostatin is impractical for clinical use because of its very short half-life [q. Octreotide, a longacting somatostatin analogue, is available for human use in the treatment of patients with metastatic, symptomatic carcinoid tumors and VIPomas [ 71. It retains the inhibitory actions of somatostatin on gut secretion [8-101. We hypothesized that octreotide would prolong survival in an anesthetized, mouse model of lethal small bowel obstruction. MATERIALS AND METHODS
From the Department of Surgery, University of California, San Francisco, San Francisco, California. Requests for reprints should be addressed to Sean J. Mulvihill, MD, Department of Surgery (U- 122), University of California, San Francisco, 533 Pamassus Avenue, San Francisco, California 94143-0788. Presented as a poster paper at the 32nd Annual Meeting of the society for Surgery of the Alimentary Tract, New Orleans, Louisiana, May 20-22,199l.
Male C57-strain mice (mean weight: 20 g) from Bantin and Kingman (Fremont, CA) were anesthetized with urethane (1.6 g/kg intraperitoneal). Mice remained anesthetized for the duration of the experiment. Through a midline laparotomy, either the proximal (ligament of Treitz) or distal (1 cm proximal to the ileocecal valve) bowel was completely occluded with suture. The laparotomy was closed in one layer. Mice were kept warm with heating blankets. In order to simulate the clinical condition, treatment was not initiated until 8 hours after the creation of the obstruction. After the initial 8 hours, all surviving mice were randomized to receive subcutaneous injections of either 2 mL of normal saline (control) or 2 mL of saline containing octreotide acetate (100 rg/kg) every 8 hours. Octreotide acetate was donated by the Sandoz Corporation (East Hanover, NJ). These studies were approved by the Committee on Animal Research of the University of California, San Francisco, and conformed with National Institutes of Health guidelines [I I].
THE AMERICAN JOURNAL OF SURGERY
VOLUME 163 FEBRUARY 1992
231
% Survival loom
60
0
10
20
30 40 50 60 70 TIME (hrs. after surgery)
.-.... Octreotide
+
60
QO 100
lo
Control
significantiypfoimged survival.
A total of 160 mice were studied. Survival was recorded to the nearest 8 hours. Data is presented as mean f standard error of the mean @EM). Where appropriate, confidence intervals are given. Comparison of survival in treated and control groups was carried out in three ways. Initially, life table analysis was used to compare survival curves over the entire experiment. Secondly, mean survival times were compared by unpaired t-test. Thirdly, the proportion of mice alive in each group at 36 hours was analyzed by chi square. RESULTS Proximal obstruction:
Proximal jejunal obstruction at the level of the ligament of Treitz was created in 80 mice. Of these, 26 died within 8 hours and were not studied. The remaining 54 mice were randomized to treatment and control groups. Survival curves over time are shown in Figure 1. Octreotide treatment delayed death significantly by life table analysis. Mean survival was 41 f 4 hours with octreotide treatment versus 3 1 f 3 hours in control mice (p = 0.03 1 by unpaired t-test). The 95% confidence interval for the difference between mean survival times was 0.6 to 19.4 hours. At 36 hours after the creation of obstruction, 11 of 27 treated mice and 4 of 27 control mice were alive (p = 0.068 by chi square). The 95% confidence interval for the differences in proportions surviving at 36 hours was 0.02 to 0.50. Distal obstruction: Distal obstruction 1 cm proximal to the ileocecal valve was created in 80 mice. After 8 hours, 47 mice were alive for randomization. Of these, 23 were assigned to octreotide treatment and 24 to saline control. Survival over time is shown in Figure 2. Life table analysis showed a trend towards improved survival that did not reach statistical significance. Mean survival was 60 f 5 hours in the octreotide treatment group versus 54 i 4 hours in the control group (p = 0.40 by unpaired ttest). The 95% confidence interval for the difference be tween mean survival times was -8.15 to 20.15 hours. The proportion of mice surviving 36 hours with distal obstruction was similar in the two groups (19 of 23 octreotide versus 20 of 24 control). The proportion of mice surviving THE AMERICAN JOURNAL OF SURGERY
20
30 40 50 60 70 TIME (hrs. after surgery)
--.---. Octreotide
F@re 1. Swvivai in mice with proximai jejunai obstrwtkm treated with ~ctreotide (n = 27) or saline control(n = 27). Octreotide
232
0
-k
60
90
100
Control
Figure 2. Wvlvai in mice with distal iieal cMruction treated with 0ctreoWe (n = 23) or saline cmtroi (n = 24). No signifkant diffemnces in suvivai were noted, atltmtgh there was a trend towards benefit with OcbOtide treatment.
64 hours in the octreotide treatment group was 10 of 23 compared with 6 of 24 controls (p = 0.319, 95% confrdence interval -0.091 to 0.451). COMMENTS
In this study, the experimental model was complete small bowel obstruction in mice that was uniformly fatal. We chose to study a well-defined end-point, time of death, rather than more subtle parameters, such as bowel distension. In these studies, mice with proximal small bowel obstruction treated with octreotide showed a statistically significant prolongation in survival time compared with mice receiving saline. The mice prepared with distal small bowel obstruction showed a similar tendency toward longer survival when treated with octreotide, although the results did not reach statistical significance. The relatively small sample size in our study may not have allowed identification of a true difference between groups. Three mechanisms likely explain the improvement in the course of small bowel obstruction by octreotide in these mice. First, octreotide inhibits secretion from the gastric fundus, pancreas, and small bowel [8-101. These secretions add to the intraluminal volume. In a vicious cycle, small bowel distension further stimulates intestinal epithelial secretion [ 121. Thus, inhibition of gut secretion is a logical mechanism to exploit in the treatment of bowel obstruction. A second potentially beneficial action of octreotide in intestinal obstruction lies in its effects on water and sodium absorption. Dharmsathaphorn et al [4] demonstrated stimulation of sodium and chloride absorption by somatostatin in rabbit ileum in vitro. These lindings have been confirmed with octreotide [8]. A third potential mechanism of action of octreotide is its inhibition of gut hormone release. Vasoactive intestinal polypeptide (VIP) release, for example, is markedly inhibited by octreotide [fl. This is a part of the rationale for treatment of severe diarrhea in VIPoma patients with octreotide. It has been suggested that release of VIP plays a role in the pathophysiology of small bowel obstruction [13]. Although our experimental model was complete small
VOLUME 163 FEBRUARY 1992
bowel obstruction, the potential clinical usefulness of octreotide is in a different setting. Nearly all patients with complete bowel obstruction require surgical intervention. However, many patients with incomplete obstruction resolve with nasogastric suction and intravenous fluid therapy alone. This latter group of patients is the most likely to benefit from the addition of octreotide to their therapeutic regimen. Other patients who may benefit from octreotide as an adjunct to therapy are those in whom surgical intervention is undesirable. Examples include patients with obstruction due to carcinomatosis or in the early postoperative period. The basic treatment of small bowel obstruction has not changed significantly in 50 years. The data from this and previous studies point to the somatostatin analogue, octreotide, as a promising candidate as a pharmacologic adjuvant to standard therapy. Further studies, including controlled trials in patients with small bowel obstruction, are needed to demonstrate clinical efficacy. REFJWzNcEs 1. Welch JP. General considerations and mortality. In: Welch JP, editor. Bowel obstruction. Differential diagnosis and clinical management. Philadelphia: WB Saunders, Co., 1990: 59-95. 2. Brazeau P, Vale W, Burgus R, ef al. Hypothalamic polypeptide that inhibits the secretion of immunoreactive growth hormone. Science 1973; 179: 77-9. 3. Mulvihill S, Pappas TN, Passaro E Jr., Debas HT. The use of somatostatin and its analogs in the treatment of surgical disorders.
Surgery 1986; 100: 467-76. 4. Dharmsathaphom K, Binder HJ, Dobbins JW, Leo L. Somatostatin stimulates sodium and chloride absorption in the rabbit ileum. Gastroenterology 1980; 78: 1559-65. 5. Mulvihill SJ, Pappas TN, Fonkalsrud EW, Debas HT. The effect of somatostatin on experimental intestinal obstruction. Ann Surg 1988; 207: 169-73. 6. Seal A, Yamada T, Debas HT, et al. Somatcstatin-14 and -28: clearance and potency on gastric function in dogs. Am J Physiol 1982; 243: G97-102. 7. Gorden P, Comi RJ, Maton PN, Go VLW. Somatostatin and somatcstatin analogue (SMS 201-995) in treatment of hormone secreting tumors of the pituitary and gastrointestinal tract and nonneoplastic diseases of the gut. Ann Intern Med 1989; 110: 35-50. 8. Roberts WG, Fedorak RN, Chang EB. In uitro effects of the long-acting somatcctatin analogue SMS 201-995 on electrolyte transport by the rabbit ileum. Gastroenterology 1988; 94: 1343-50. 9. Williams ST, Woltering EA, G’Dorisio TM, Fletcher WS. Effect of octreotide acetate on pancreatic exocrine function. Am J Surg 1989; 157: 459-62. 10. Whitehouse I, Beglinger C, Rultimann G, Gyr K. Inhibition of pentagastrin-stimulated acid secretion after subcutaneous administration of a new somatostatin analogue. Gut 1986; 27: 141-6. 11. Guide for the Care and Use of Laboratory Animals. NIH Publication No. 86-23. National Institutes of Health, Bethesda, Maryland, 1985. 12. Caren JF, Meyer JH, Grossman MI. Canine intestinal secretion during and after rapid distension of the small bowel. Am J Physiol 1974; 227: 183-8. 13. Basson MD, Fielding LP, Bilchik AJ, et al. Does vasoactive intestinal polypeptide mediate the pathophysiology of bowel ob struction? Am J Surg 1989; 157: 109-115.
THE AMERICAN JOURNAL OF SURGERY
VOLUME 163 FEBRUARY 1992
233