Faculty Bibliography

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.

BACKGROUND:Several series of laparoscopic colon resection have been reported in the literature with varied results; however, no controlled series of laparoscopic vs open colon resection has been reported. The purpose of this study was to determine the relative safety and adequacy of laparoscopic colon resection in a controlled trial using a porcine model. METHODS:Domestic pigs (n = 23) were randomly divided into two groups. Animals underwent either an open or laparoscopic-assisted segmental resection of the sigmoid colon. The open resections were performed through a 20-cm midline incision and the laparoscopic technique utilized five 12-mm ports. Laparoscopic resection took twice as long to complete as open resection (P < 0.001). Return of gastric function was significantly faster in the laparoscopic group than in the open group (P < 0.032). RESULTS:No significant differences were found in total length of resection, proximal or distal margins, number of lymph nodes recovered, length of mesenteric vessel resected, or time to return of bowel function. At vivisection, more adhesions to the abdominal wall were noted in the open group (P < 0.002). One death occurred in the laparoscopic group 2 h postoperatively (8.3% mortality) while all open group pigs survived. However, there was no statistically significant difference in mortality rates by chi-square analysis (P > 0.5). CONCLUSIONS:Despite longer operative time, laparoscopic intervention is technically feasible, safe, and may offer significant postoperative benefits due to fewer abdominal adhesions.

OBJECTIVE:To test our hypothesis that tumors would be more easily established and grow more aggressively after laparotomy than after laparoscopy. This hypothesis was based on studies that have demonstrated that surgery can suppress immune function and facilitate tumor growth and that have shown preservation of immune function after laparoscopic procedures. DESIGN/METHODS:Double-blinded, randomized, control trial. SETTING/METHODS:Research laboratory and animal care facility. ANIMALS/METHODS:One hundred forty 5- to 6-week-old C3H/He female mice. INTERVENTIONS/METHODS:Three experiments with three groups each: laparotomy, insufflation, and anesthesia controls. All animals received an intradermal inoculation of tumor cells in the dorsal skin. The anesthesia control cohort underwent no procedure. The laparotomy cohort underwent a midline laparotomy from the xiphoid process to the pubis, which was closed after 30 minutes. The insufflation cohort underwent peritoneal insufflation with carbon dioxide for 30 minutes. MAIN OUTCOME MEASURES/METHODS:Tumor volume, tumor mass, and incidence of tumor establishment. RESULTS:In the first experiment, the tumor volumes of the anesthesia control and insufflation groups followed a similar pattern of plateau and regression. The tumor volumes of the laparotomy group followed a different pattern and were significantly larger than those of the control and insufflation groups on postoperative days 6 and 12 (P < .05 for all comparisons). In the second experiment, tumors in the laparotomy group were approximately three times larger than those of the control group (P < .01) and almost twice as large as insufflation group tumors (P < .01) by mass. In the third experiment, there was a significantly higher incidence of tumor establishment in the laparotomy group than in the insufflation (P < .04) or control (P < .01) groups. The incidence was not different between the control and insufflation groups. CONCLUSIONS:Tumors were more easily established and grew more aggressively after laparotomy than after insufflation. These results, coupled with those that demonstrate an immune advantage to laparoscopy over laparotomy, suggest that the difference in observed tumor growth may be related to immune function. While much work remains to be done, we believe these data provide evidence of a previously undemonstrated benefit of laparoscopic intervention.

We investigated the effects of laparotomy and insufflation on tumor establishment and growth in a murine model. Twenty female mice received intradermal inoculation of a low dose of tumor cells (2 x 10(3)) derived from the MC2 mouse mammary carcinoma cell line. Ten of these mice underwent laparotomy and ten received intraperitoneal insufflation with carbon dioxide gas at a pressure of 5 mmHg for 30 min. Tumor growth was followed postoperatively. By postoperative day 14, tumors had grown in zero of the ten insufflated mice and in seven of the ten laparotomy-group mice (P < 0.005). By postoperative day 30, tumors had grown in one of the ten insufflated mice and in eight of the ten laparotomy-group mice (P < 0.007). Ten additional mice received a high-dose inoculum of cells (1 x 10(6)) followed by either laparotomy or intraperitoneal insufflation. Upon sacrifice 12 days later, all mice had developed tumors, but the laparotomy group's tumors were almost three times as large, by mass, as tumors in the insufflated group (70.5 +/- 23.5 mg vs 25.8 +/- 9.5 mg; P < 0.02). These results suggest that laparotomy confers a permissive effect on tumor establishment and growth in a murine model not seen after peritoneal insufflation. We hypothesize that this may be a function of relative immunosuppression following laparotomy which is not present following peritoneal insufflation. These data may be important when choosing a route of access to the peritoneal cavity for cancer resection.