Addition of nitrous oxide to the carbon dioxide pneumoperitoneum strongly decreases adhesion formation and the dose-dependent adhesiogenic effect of blood in a laparoscopic mouse model.

OBJECTIVE: To evaluate the effect of addition of nitrous oxide (N2O) to the carbon dioxide (CO2) pneumoperitoneum (PP) and the effect of blood, plasma, or red blood cells (RBCs) on postoperative adhesions in a laparoscopic mouse model. DESIGN: Prospective randomized controlled trial. SETTING: University laboratory research center. ANIMAL(S): BALB/c female mice. INTERVENTION(S): The effect of adding to the 60-minute CO2 PP 5%, 10%, 25%, 50%, or 100% N2O on adhesion formation was evaluated. Subsequently the effect of adding 1 mL blood, or RBCs, or plasma and the effect of adding different concentrations of blood were studied. Finally, the effect of adding 10% N2O, 4% O2, or both to the CO2 was evaluated in a control group and after addition of blood. MAIN OUTCOME MEASURE(S): Postoperative adhesions after 7 days. RESULT(S): N2O strongly reduces adhesion formation with a full effect at a concentration of 5% or 10%. Adhesions increase linearly with 0.125 mL to 1 mL blood. In both the control group and after adding blood, 10% N2O is the most effective factor in prevention of adhesions. CONCLUSION(S): N2O, from concentrations of 5% upward, strongly prevents adhesion formation. Blood, mainly the plasma, increases adhesion formation. These data extend the concept of the role of acute inflammation and support the importance of good surgical practice with little bleeding and peritoneal cavity conditioning in adhesion prevention.

Intraperitoneal temperature and desiccation during endoscopic surgery. Intraoperative humidification and cooling of the peritoneal cavity can reduce adhesions.

This study was conducted to document quantitatively the intraperitoneal temperature and desiccation during laparoscopic surgery. The temperature, relative humidity, and flow rate were measured in vitro and during laparoscopic surgery, at the entrance and at the exit of the abdomen. This permitted us to calculate desiccation for various flow rates using either dry CO(2) or CO(2) humidified with 100% relative humidity at any preset temperature between 25 and 37°C. The study showed that desiccation, both in vitro and in vivo, varies as expected with the flow rates and relative humidity while intraperitoneal temperature varies mainly with desiccation. Temperature regulation of bowels is specific and drops to the intraperitoneal temperature without affecting core body temperature. With a modified humidifier, desiccation could be eliminated while maintaining the intraperitoneal temperature between 31 to 32°C.

Postoperative inflammation in the abdominal cavity increases adhesion formation in a laparoscopic mouse model.

OBJECTIVE: To investigate acute inflammation in the peritoneal cavity in adhesion formation. DESIGN: Prospective randomized, controlled trial. SETTING: University laboratory research center. ANIMAL(S): 9- to 10-week-old BALB/c female mice. INTERVENTION(S): In a laparoscopic mouse model, acute inflammation in the peritoneal cavity evaluated in CO(2) pneumoperitoneum enhanced adhesions, by CO(2) pneumoperitoneum plus manipulation, and in the latter group plus dexamethasone. MAIN OUTCOME MEASURE(S): Qualitative and quantitative adhesion scores and an acute inflammation score (neoangiogenesis, diapedesis, and leukocyte accumulation). RESULT(S): Adhesions at the lesion site were enhanced by the CO(2) pneumoperitoneum, further enhanced by manipulation, and decreased by the administration of dexamethasone. The acute inflammation scores (total, neoangiogenesis, diapedesis, and leukocyte accumulation) strongly correlated with the total adhesion score. Inflammation scores were similar at both the surgical lesion and the parietal peritoneum. CONCLUSION(S): Acute inflammation of the entire peritoneum cavity is an important mechanism involved in adhesion formation and enhances adhesion formation at the lesion site.

Intercoat gel (oxiplex): efficacy, safety, and tissue response in a laparoscopic mouse model.

STUDY OBJECTIVE: To study the efficacy and safety of Intercoat gel in a laparoscopic mouse model with pneumoperitoneum-enhanced adhesion formation. DESIGN: Randomized controlled trial. Evidence obtained from a properly designed, randomized, controlled trial (Canadian Task Force classification I). SETTING: University laboratory research center. SUBJECTS: Balb\c female mice 9 to 10 weeks old. INTERVENTIONS: Two laparoscopic mouse models for adhesion formation were used. In the first model, adhesions following bipolar opposing lesions in the pelvis were enhanced by 60 minutes of carbon-dioxide pneumoperitoneum. In the second model, adhesions were further enhanced by bowel manipulation. The first experiment evaluated the efficacy of Intercoat in both models. The second experiment evaluated the efficacy of Intercoat in the first model, when applied immediately on the lesion, when applied at the end of the pneumoperitoneum, and when applied in the upper abdomen. Biopsy specimens were taken after 7 days and were evaluated after hematoxylin-eosin and CD45 staining. MEASUREMENTS AND MAIN RESULTS: Qualitative and quantitative adhesion scoring. Morphology was evaluated by standard light microscopy. In both models, Intercoat decreased adhesion formation whether applied immediately on the lesion or at the end of the pneumoperitoneum (qualitative and quantitative scoring p <.0001 and p <.0001, respectively). Intercoat application is associated with tissue redness, vascular congestion, and cellular edema but without an inflammatory reaction. Applied in the upper abdomen, Intercoat does not increase adhesions, but decreases adhesions at higher doses (p =.0024). Intercoat in high doses had a toxic effect (p =.0058). CONCLUSION: Intercoat is an effective antiadhesion product. It is associated with tissue edema and vasodilatation as observed after 7 days both macroscopically and by histology.

Effects of adding small amounts of oxygen to a carbon dioxide-pneumoperitoneum of increasing pressure in rabbit ventilation models.

OBJECTIVE: To evaluate the metabolic consequences of the addition of oxygen to the CO(2)-pneumoperitoneum. DESIGN: Prospective randomized study in rabbits. After 30 minutes of ventilation pneumoperitoneum was maintained for 90 minutes with pure CO(2) or CO(2) with 2% or 6% of oxygen. The intraperitoneal pressure was increased from 10 to 15 and 20 mm Hg every 30 minutes. Ventilation rate was either fixed or a progressive hyperventilation. End points were changes in arterial blood gases (Pco(2), Po(2)), pH, acid-base balance (actual base excess [ABE], standard bicarbonate [SBC], standard base excess [SBE], hydrogen carbonate [HCO(3)(-)], concentration of total carbon dioxide [Tco(2)]); oxygen and oximetry (oxyhemoglobin [O(2)Hb], oxygen saturation [So(2)], reduced hemoglobin [RHb], total oxygen concentration [To(2)], and oxygen tension at half saturation assessing hemoglobin oxygen affinity [p50]); and lactate concentrations assayed every 15 minutes. SETTING: University research center. ANIMALS: Twenty-four adult female New Zealand white rabbits. INTERVENTION(S): Anesthesia, mechanical ventilation, and pneumoperitoneum. RESULT(S): The effects of CO(2)-pneumoperitoneum on all end points increased with the elevated intraperitoneal pressure and were more pronounced when ventilation was fixed. Changes were less when 2% or 6% of oxygen had been added to the CO(2)-pneumoperitoneum. With use of logistic regression, the addition of oxygen, intraperitoneal pressure, and ventilation were found to be independent variables affecting Pco(2), pH, ABE, SBE, HCO(3)(-), O(2)Hb, So(2), p50, and end-tidal CO(2). CONCLUSION(S): The metabolic consequences of the combined effect of increased intraperitoneal pressure and CO(2)-pneumoperitoneum were less when 2% to 6% of oxygen was added or when animals were hyperventilated. We suggest that metabolic and mesothelial hypoxemia caused by CO(2) absorption can be reduced by adding small amounts of oxygen and by hyperventilation.

The rabbit nephrectomy model for training in laparoscopic surgery.

BACKGROUND: Laparoscopic surgical training is generally done with the teacher-student model using complex exercises. This study was performed to evaluate a new training model that emphasizes the repetition of simple procedures. METHODS: Laparoscopic surgery was performed in rabbits (n=200) using conventional instruments. Gynaecologists (n=10) and medical students (n=10) performed a series of exercises during 20 full days training. Nephrectomy was chosen to evaluate and score laparoscopic skills, i.e. duration of surgery and complication rate, since it mimics the surgical challenge and involves dissection of major vessels. Each surgeon performed 20 nephrectomies, alternating left and right sides. RESULTS: Duration of surgery and complications decreased with training. For duration of surgery, a two-phase exponential decay learning curve, with different decays for gynaecologists and students, was observed. Gynaecologists achieved shorter operating times than students for real and calculated times in the first procedure (P<0.0001 and P<0.0001) and for calculated time in the last procedure (P=0.001). Severe complications were more frequent in students than in gynaecologists (P=0.0003). CONCLUSION: The rabbit nephrectomy model is suitable for training in laparoscopic surgery. Since it implies the repetition of short and well-defined exercises, progression is easier to monitor and the necessity for continuous supervision is less, making training less expensive.