Faculty Bibliography

BACKGROUND:Reports of port site tumor recurrences after laparoscopic-assisted resection of colon tumors have raised concerns about the safety of laparoscopic cancer surgery. Tumor cell suspension studies in animals have implicated the CO2 pneumoperitoneum (pneumo) in the etiology of port tumors. Unfortunately, in several ways, the cell suspension model is unrealistic and does not permit assessment of how tumor cells become liberated from the primary tumor. The purpose of this study was to establish a more realistic splenic tumor model and to determine the relative importance of the CO2 pneumo and excessive surgical manipulation in the development of port site and incisional tumor recurrences. METHODS:Splenic tumors were established in female Balb/C mice (n = 134) via a subcapsular injection of 10(5) C-26 colon adenocarcinoma cells (0.1 ml volume) via a left-flank incision at the initial procedure. Ten days later, the animals were reexplored via a 1-cm left subcostal incision. Those with isolated splenic tumors (95%) were randomized into one of four groups: (a) control, (b) CO2 pneumo, (c) crushed tumor, or (d) crushed tumor with pneumo. Ports were placed in the left lower, right lower, and right upper quadrants of each mouse. In groups 1 and 2, the mice underwent a meticulously performed splenectomy; in groups 3 and 4, the tumor capsule was crushed intraabdominally prior to splenectomy. In groups 1 and 3, the subcostal incision was closed and the ports were removed after 15 min of anesthesia. Following splenectomy, group 2 and group 4 mice underwent closure of the subcostal incision and a 15-min CO2 pneumo (4-6 mm Hg) after which the ports were removed. Twelve days later, the mice were killed and examined for abdominal wall tumor implants. RESULTS:Significantly more animals in group 3 (crushed tumor) developed port site and incisional tumors than those in group 1 (control) (p < 0.002 for both comparisons). The same results were found when group 4 (crush plus pneumo) was compared to group 2 (pneumo) (p < 0.002 for both comparisons). Regarding the port wounds, when the ports are considered individually (number of ports with tumors/total number of ports for each group), there were significantly more port tumors in the two crush groups than in the noncrush groups. No significant differences were noted when the port site and incisional tumor rates for group 1 (control) and group 2 (pneumo) were compared or when the results for group 2 (crush) and group 4 (crush pneumo) were compared. CONCLUSIONS:A splenic tumor model was successfully established. When compared to meticulous technique, purposefully traumatic handling of the splenic tumor before resection resulted in significantly more port wound and incisional tumors. In contrast, the addition of a pneumo after splenectomy did not significantly influence the incidence of port tumors in either the "good" or the "poor" technique groups. These results suggest that surgical technique plays a larger role in the development of port site tumors than the CO2 pneumoperitoneum.

BACKGROUND:We investigated the ability of pressurized CO2 gas to aerosolize B16 melanoma (B16) tumor cells in an in vitro model. METHODS:The experimental apparatus consisted of an 18.9-L plastic cylindrical vessel and a compliant latex pouch was attached to the top. Two 5-mm ports penetrated the vessel; insufflation and desufflation were carried out through them. A culture dish containing 20 million B16 cells in liquid culture media was placed at the base within the container. In the first experiment, the vessel was insufflated with CO2 gas to a static pressure of 15 or 30 mm Hg with the outflow port closed. After 10 min, the outflow port was opened and the gas was desufflated through a collecting device containing sterile culture medium. In a second experiment, a continuous flow of CO2 through the vessel was maintained after a pressure of 15 or 30 mm Hg was established. A total of 10 L CO2 was cycled through the vessel. In both experiments, 24 determinations were carried out at each pressure. Each experimental culture dish was microscopically scanned for 2 weeks for the presence of tumor cells. The third and fourth experiments tested for the presence of aerosolized nonviable tumor cells in the expelled gas. Using the model described above, after 10 mins of 30 mm Hg static pressure, the CO2 gas was expelled directly onto a glass slide and cytofixed. Alternately, after 10 mins at 30 mm Hg static pressure, the gas was expelled through a saline-filled Soluset (Abbott Laboratories), centrifuged, and the residue cytofixed onto a glass slide. Each of the five slides per experiment were examined microscopically for the presence of cells. RESULTS:In the first and second experiments, no cells or growth were observed in any of the 96 experimental dishes. In experiments three and four, no cells were detected on any of the slides. CONCLUSIONS:It was not possible with this model to aerosolize tumor cells in a pressurized CO2 environment. Our results suggest that aerosolization of tumor cells is not the mechanism of port site recurrences after laparoscopic surgery for malignant disease.

PURPOSE/OBJECTIVE:Mouse mammary carcinoma tumors are established more easily and grow larger after sham laparotomy and open bowel resection than after CO2 pneumoperitoneum and laparoscopic-assisted bowel resection. The purpose of this study was to determine whether similar differences in tumor growth would be found when sham laparotomy and pneumoperitoneum were compared for the colon-26 mouse adenocarcinoma and B-16 mouse melanoma tumor lines. METHODS:In all three studies, a high-dose injection of tumor cells was used, which resulted in tumors in almost all control mice. In Study 1, female BALB/C mice (n = 127) were injected intradermally in the dorsal skin with 10(6) colon-26 cells in a 0.1-ml volume before interventions. In Study 2, female C57 BL/6 mice (n = 140) were inoculated similarly with 10(6) B-16 melanoma cells. Study 2 consisted of three separate trials conducted on different days. Study 3 was performed because considerable differences in mean tumor size were observed in each of these trials. In Study 3, the B16 experiment was repeated with a larger n (n = 82) on a single day. In each study, after tumor cell injections, mice were randomly assigned to one of three groups: 1) anesthesia control (no procedure); 2) full laparotomy (4-cm midline incision x 20 minutes, staple closure); or 3) CO2 pneumoperitoneum (4-6 mmHg X 20 minutes). Tumors were excised and weighed on postoperative day 12. RESULTS:In Studies 1 and 3, mean tumor sizes of the laparotomy groups were significantly larger than both the control group and pneumoperitoneum group lesions (P values by Student's t-test). In Study 2, laparotomy group tumors, although significantly larger than control group lesions, were not significantly larger than pneumoperitoneum group tumors. For all three studies, there was no significant difference between mean tumor sizes of the pneumoperitoneum and control groups. CONCLUSION/CONCLUSIONS:Both colon-26 adenocarcinoma and B-16 melanoma tumors grow larger after laparotomy than after pneumoperitoneum in a murine model. The mechanism of these postoperative tumor growth differences remains to be elucidated.

BACKGROUND:Previous work has demonstrated that cell-mediated immune function is better preserved in rodents after laparoscopic than open surgery. The cause of this laparotomy-related immunosuppression is unclear. Some investigators have attributed it to the length of the incision; others, to peritoneal air exposure. It has also been shown that tumors in mice are more easily established and grow larger after sham laparotomy than after pneumoperitoneum. Lastly, the differences in tumor growth have been shown to be, at least in part, attributable to the immunosuppression that occurs after laparotomy. The purpose of this study was to determine if air pneumoperitoneum, presumably via immunosuppression related to peritoneal air exposure, is associated with increased tumor growth in the postoperative period. METHOD/METHODS:A total of 150 immunocompetent syngeneic mice received high-dose intradermal injections of mouse mammary carcinoma tumor cells. They were then randomized to undergo one of the following procedures: (a) anesthesia alone, (b) air insufflation (44 mm Hg), (c) CO2 insufflation, or (d) full laparotomy. No intraabdominal procedure was carried out. All procedures were 20 min long. After 12 days, the animals were killed and the mean tumor mass determined for each group. RESULTS:All animals grew tumors. There was no significant difference in the mean tumor size of the anesthesia control, CO2 insufflation, and air insufflation groups (p > 0.85 by ANOVA). However, the laparotomy group tumors were 1.5 times as large as those of the other three groups (p < 0.05 by ANOVA). CONCLUSIONS:In this model, air insufflation did not significantly affect postoperative tumor growth, nor did CO2 pneumoperitoneum. However, full laparotomy was associated with increased tumor growth.

BACKGROUND:In order to better investigate the effects of laparoscopic surgery, it is necessary to establish reliable, reproducible, and economical animal models of laparoscopic intervention. Here we describe a mouse model of laparoscopic-assisted colon resection. METHODS:After successful induction of anesthesia the mouse is placed in Trendelenburg position and the peritoneal cavity is insufflated with carbon dioxide gas through an angiocatheter placed in the right upper quadrant. A 4-mm rigid scope with camera attachment is then inserted through a midline port created just caudal to the xiphoid. A second port is then created in the right lower quadrant to allow introduction of laparoscopic forceps into the peritoneal cavity. The cecum, which extends 1.5 cm beyond the ileocecal valve, is grasped with forceps and exteriorized through the operative port. Extracorporeally, the cecum is ligated and resected before the cecal stump is returned to the peritoneal cavity. The abdominal wall defects are then stapled closed. RESULTS:This simple model can be mastered by individuals with very limited surgical experience. This laparoscopic model has been used successfully in our laboratory in a number of experiments with an intraoperative complication rate of 3. 2% (3/94), which was similar to the open surgery group rate of 2.1% (2/95, p = 0.99 by chi square). We observed no postoperative leaks in either group. The only postoperative death occurred in the open resection group due to dehiscence of the laparotomy wound. CONCLUSIONS:We propose that this model may be useful for comparing the effects of open to laparoscopic surgery.

BACKGROUND:Major surgery through a laparotomy incision is associated with a postoperative reduction in immune function. Studies in rats involving sham procedures suggest that immune function may be preserved after laparoscopy. This study investigates the effects of incision length and exposure method for bowel resection with respect to postoperative immune function as assessed by delayed-type hypersensitivity (DTH) reactions. METHODS:Male Sprague Dawley rats (n = 175) were challenged preoperatively, immediately postoperatively, and on postoperative day 2 with an intradermal injection of 0.2 mg phytohemagglutinin (PHA), a nonspecific T-cell mitogen. The averages of two measures of perpendicular diameters were used to calculate the area of induration. Anesthesia control rats underwent no procedure. Minilaparotomy rats underwent a 3.5-cm midline incision. Sham full laparotomy rats underwent a 7-cm midline incision. The open bowel-resection group underwent a cecal ligation and resection through a 7-cm midline incision. In the laparoscopic-assisted resection group a CO2 pneumoperitoneum and four-port technique was utilized to deliver the cecum through a 4-mm port where the cecum was extracorporeally ligated and resected. RESULTS:Preoperative responses were similar in all five groups. Incision length: Full laparotomy group responses were 20% smaller than anesthesia control responses on postoperative day (POD)1 through POD4 (p < 0.02). At no time point were the responses in the minilaparotomy group significantly different from either anesthesia control or full laparotomy group responses. Exposure method: The laparoscopic-assisted resection group responses were 20% larger than open group responses at the time of two of the four postoperative measurements (p < 0.05, both comparisons). At all postoperative time points, open resection group responses were significantly smaller than control responses (p < 0.05, all comparisons), whereas at no time point were laparoscopic group responses significantly different from control responses. CONCLUSION/CONCLUSIONS:We conclude that postoperative cell-mediated immune function varies inversely with the degree of surgical trauma. Results from the minilaparotomy and laparoscopy groups suggest that procedures done through small incisions may result in preservation of postoperative immune function.

BACKGROUND AND OBJECTIVE/OBJECTIVE:Reports in the literature indicate that low energy laser irradiation has a biostimulatory effect on wound healing; however, no mechanism of this effect has been elucidated. STUDY DESIGN/MATERIALS AND METHODS/METHODS:We attempted to establish a model from which to study the mechanism of biostimulation. The effects of low energy helium-neon irradiation on wound healing were observed in two rat models. In the first model, 1.5 cm diameter full thickness excisional skin defects were created in the dorsal midline of rats (n = 32). All animals were anesthetized and all eschars were debrided daily. Wound area was determined by caliper measurements for 2 weeks postoperatively. Rats that received a treatment of 1 J/cm2 had two defects in the dorsal skin. One wound was treated and the second was used as its own control. These measurements were not blinded. Rats that received 2 J/cm2, 4 J/cm2, or anesthesia alone had one defect on the dorsal skin. Caliper measurements of these wounds were blinded. We were unable to demonstrate any difference in the rate of wound contracture in rats that received a daily dose of 1 J/cm2, 2 J/cm2, 4 J/cm2, or anesthesia alone (P > 0.8 by student's t-test). In the second model, a single 2 cm longitudinal full thickness skin incision was created in the dorsal midline of each rat (n = 24). No difference was found between rats that received anesthesia alone and those treated daily with 2 J/cm2 as assessed by tensile strength measurements on postoperative days 7 and 14 (P > 0.8 by student's t-test between groups at both time points). These determinations were blinded. RESULTS:Despite our intentions of studying the mechanism of low energy HeNe biostimulation, we were unable to demonstrate a beneficial effect. CONCLUSION/CONCLUSIONS:In this study, helium-neon laser irradiation produced no measurable benefit on wound healing.

PURPOSE/OBJECTIVE:This study was undertaken to investigate the ability of a high-pressure CO2 environment to aerosolize tumor cells in both in vitro and in vivo models. (An aerosol is defined as a stable gaseous suspension of insoluble particles). Also, this study was designed to determine if rapid desufflation is capable of transporting fluid laden with tumor cells. METHODS:The four in vitro aerosol experiments were performed in an 18.9-1 plastic vessel fitted with two 7-mm ports and a compliant latex balloon affixed to the top. After CO2 insufflation, the vessel was desufflated through a sterile soluset containing 25 ml of culture media that was subsequently emptied into a culture dish, incubated for two weeks, and periodically assessed for growth. At the bottom of the vessel, one of the following was placed: Study 1 and 2, a suspension of B16 melanoma or colon 26 tumor cells in liquid culture media; Study 3, colon 26 cells in saline solution; Study 4, several pieces of solid colon 26 tumor. In Studies 1 to 3, cell preparations were subjected to the following high-pressure CO2 conditions (pneumo): 1) static pneumo of 15 and 30 mmHg (10 minute dwell); 2) a continuous flow (CF) of CO2 (1O l) while maintaining a pressure of 15 or 30 mmHg in the vessel. In Study 4, only the 30 mmHg static and CF conditions were tested. Between 6 and 12 determinations were performed for each condition and cell preparation. In vivo aerosol experiments consisted of Spraque Dawley rats that received intraperitoneal injections of 10-5 B16 cells in 0.1 ml of liquid media. Two laparoscopic ports were placed in the abdomen, one each for insufflation and desufflation. Study groups were: 1, static CO2 pneumo of 15 mmHg; 2 and 3, continuous CO2 flow (10 l) at a stable pneumo pressure of 5 and 10 mmHg. Desufflation was performed via the same collecting device and handled in an identical manner to the in vitro experiments described above. The in vitro balloon experiment was designed to investigate the ability of desufflation to transport fluid-containing tumor cells; latex balloon model was used. To prevent complete loss of volume on desufflation, a wire coil was placed inside the balloon. Twenty ml of media containing 20 x 10(-6) B16 cells was placed in the bottom of the balloon. The balloon was insufflated with 1 to 2 l of gas. There were three study groups that differed in the degree to which the cell suspension was agitated before desufflation. Study conditions were as follows: 1) no agitation; 2) moderate agitation to coat the lower walls and coil; 3) maximum agitation to coat the entire balloon. To verify the viability of tumor cells, at the end of each in vitro and in vivo study, a sample of tumor cells or peritoneal washing was incubated in sterile media. These samples served as positive controls. RESULTS:In vitro aerosol studies consisted of the following. At the end of two weeks of incubation, no tumor growth was noted in any of the 124 test dishes. The 14 control samples all demonstrated tumor growth. In vivo aerosol studies consisted of the following. Zero of 18 experimental dishes grew tumor. All three peritoneal washing samples demonstrated growth. In vitro balloon studies consisted of the following. Zero of 12 test dishes in Groups 1 and 2 demonstrated growth, whereas five of six dishes did so in Group 3 (maximally agitated before desufflation). Again, positive controls all grew tumor cells. SUMMARY/CONCLUSIONS:We were unable to demonstrate aerosol formation in any of the in vitro and in vivo studies performed. In the balloon experiment, desufflation-related transport of tumor cells was demonstrated but only when the entire balloon surface was coated with the tumor cell suspension before desufflation. CONCLUSION/CONCLUSIONS:Aerosols of tumor cells are not likely to form. Free intraperitoneal tumor cells are most likely found in liquid suspension. Desufflation is a potential means of transport of cell-laden fluid.

UNLABELLED:We evaluated cell-mediated immune function after laparoscopic-assisted and open bowel resection in rats by measuring delayed-type hypersensitivity responses to keyhole limpet hemocyanin (KLH) and phytohemagglutinin (PHA). METHODS:Male Sprague-Dawley rats (n = 120) were sensitized to 1 mg of KLH ten days before investigations. Rats were challenged preoperatively, immediately postoperatively, and on postoperative day (POD) 2 with an intradermal injection of 0.3 mg of KLH and 0.2 mg of PHA (at different sites). Averages of two measures of perpendicular diameters (taken 24 and 48 hours postchallenge) were used to calculate the area of induration using the formula for the area of an ellipse, A = (D1/2 x D2/2) x pi. Anesthesia control animals underwent no procedure (n = 40). Open resection group underwent ligation and resection of the cecum (length = 2 cm) through a 7 cm midline incision (n = 40). In the laparoscopic-assisted resection group, under CO2 pneumoperitoneum (4-6 mmHg), the cecum was identified, dissected free, and exteriorized through a 4 mm port. The cecum was then ligated and resected extracorporeally (n = 40). RESULTS:Preoperative responses to both KLH and PHA were the same in all three groups. Furthermore, within each group, postoperative responses were similar. When groups were compared, the anesthesia group responses were significantly greater than the open resection group responses at all time points (P < 0.05 for all comparisons). Laparoscopic assisted resection group responses differed from control at only two of eight postoperative measures. Laparoscopic resection group responses were significantly greater than open resection group responses to challenge with both KLH and PHA on POD1 (P < 0.02, for both comparisons) and POD 4 (P < 0.05, for both comparisons). CONCLUSIONS:Postoperative cell-mediated immune function is better preserved after laparoscopic-assisted bowel resection than after open resection as assessed by skin antigen testing.

Percutaneous stents are used in vascular applications in conjunction with angioplasty and in combination with graft material for repair of abdominal aneurysms. The authors have designed a collapsible bioprosthetic aortic valve for placement by a transluminal catheter technique. This trileaflet stent valve is composed of stainless steel and bovine pericardium. Stent valves, 23 and 29 mm, were tested in a pulse duplicator system with rigid rings from 21 to 31 mm in 2 mm increments. At a mean flow of 3.1 L/min (+/-0.7), normal systemic aortic pressure was generated with a transvalvular gradient of 14.9 +/- 7 mmHg (mean +/- SD). Regurgitation fraction ranged from 10 to 18% (mean 13.8 +/- 3%) in the best ring size. Valves with the best hemodynamic profile were used for implantation in three 70 kg pigs in an open chest model. The valve was collapsed in a 24 Fr catheter designed to allow slow, controlled release. After resection of the native leaflets, the new valve was placed in the subcoronary position. No additional sutures were used for securing the valve. Two animals were successfully weaned from cardiopulmonary bypass and maintained systemic pressures of 100/45 (+/-10) and 116/70 (+/-15) mmHg, respectively. Intraoperative color echocardiography revealed minimal regurgitation, central flow, full apposition of all leaflets, and no interference with coronary blood flow. Both animals were sacrificed after being off bypass for 2 hr. Postmortem examination revealed the valves to be securely anchored. The third animal was weaned from cardiopulmonary bypass but developed refractory ventricular fibrillation because of valve dislodgment due to structural failure. Although long term survival data are needed, development of a hemodynamically acceptable prosthetic aortic valve for transluminal placement is feasible.