Adhesion formation in intubated rabbits increases with high insufflation pressure during endoscopic surgery

Role of the plasminogen system in basal adhesion formation and carbon dioxide pneumoperitoneum-enhanced adhesion formation after laparoscopic surgery in transgenic mice

OBJECTIVE

To evaluate the role of plasminogen activator inhibitor-1 (PAI-1), urokinase plasminogen activator (uPA), and tissue-type plasminogen activator (tPA) in adhesion formation after laparoscopic surgery.

DESIGN

Prospective, randomized study.

SETTING

Academic research center.

ANIMAL(S)

Seventy female wild-type and transgenic knockout mice for PAI-1 (PAI-1(-/-)), uPA (uPA(-/-)) or tPA (tPA(-/-)).

INTERVENTION(S)

Standardized lesions to induce peritoneal adhesions were performed during laparoscopy. To evaluate basal adhesions and pneumoperitoneum-enhanced adhesions, the pneumoperitoneum was maintained for 10 minutes or 60 minutes, respectively. Peritoneal biopsy samples were obtained during and after 60 minutes of carbon dioxide pneumoperitoneum.

MAIN OUTCOME MEASURE(S)

Adhesions were blindly scored after 7 days. Concentrations of PAI-1 and tPA were measured by using enzyme-linked immunosorbent assay.

RESULT(S)

In PAI-1, uPA, and tPA wild-type mice, pneumoperitoneum enhanced adhesions. Compared with wild-type mice, basal adhesions were fewer in PAI-1(-/-) mice and more in uPA(-/-) and tPA(-/-) mice. Pneumoperitoneum did not enhance adhesions in these transgenic mice. PAI-1 concentration increased after 60 minutes of pneumoperitoneum whereas tPA concentration did not change.

CONCLUSION(S)

Impaired fibrinolysis increases basal adhesions. The absence of pneumoperitoneum-enhanced adhesions in PAI-1(-/-), uPA(-/-), and tPA(-/-) mice and the increase in PAI-1 expression indicate that PAI-1 up-regulation by carbon dioxide pneumoperitoneum is a mechanism of pneumoperitoneum-enhanced adhesion formation.

Combined therapy of allantoin, metronidazole, dexamethasone on the prevention of intra-abdominal adhesion in dogs and its quantitative analysis

AIM: To observe the preventive effects of combined therapy of AMD (allantoin, metronidazolem and dexamethasone in combination) on intra-abdominal adhesion in dogs.

METHODS: 20 dogs of both sexes were used in this study. After laparotomy under anesthesia, 2 cm section of cecal end was clamped and ligated, then 1 cm cecum section was cut and another 1 cm was kept. The cecum stump was closed with purse-string suture. Both parietal and visceral peritonea were stripped for an area of about 3 × 4 cm². Before the skin closure, the animals were divided into two groups randomly. The abdominal cavities in Group AMD (n = 10) were rinsed by 200 mL of AMD solution, and with 50 mL left, whereas the control (n = 10) received the equal volume of normal saline. After 7 d, the degree of intra-abdominal adhesions was evaluated by using the score method of ultrasonography and traditional dissection.

RESULTS: Compared with the control, both the ultrasonography and traditional dissection scores in Group AMD were significantly decreased that marked as 2.0 ± 1.25 vs 3.3 ± 0.82 and 1.91 ± 0.83 vs 3.3 ± 0.82 respectively (P < 0.01).

CONCLUSION: The combined therapy of AMD is an effective way to prevent intra-abdominal adhesion, and ultrasonography is an useful tool to diagnose intra-abdominal adhesion.

Pathogenesis of CO(2) pneumoperitoneum-induced metabolic hypoxemia in a rabbit model

STUDY OBJECTIVE

To investigate the effects of carbon dioxide (CO(2)) pneumoperitoneum-induced changes in blood gases, acid-base balance, and oxygen homeostasis in rabbits.

DESIGN

Prospective, randomized, controlled study (Canadian Task Force classification I).

SETTING

University training and teaching center.

SUBJECTS

Twenty-six adult female New Zealand white rabbits.

INTERVENTION

Anesthesia and pneumoperitoneum.

MEASUREMENTS AND MAIN RESULTS

In anesthetized rabbits arterial blood gases, acid-base balance, oxygenation values, and lactate concentrations were assayed during 2 hours. Spontaneous breathing, superficial and optimal ventilation without pneumoperitoneum, and with pneumoperitoneum at low (6 mm Hg) and higher (10 mm Hg) insufflation pressures were compared. The CO(2) pneumoperitoneum profoundly affected blood gases, acid-base balance, and oxygen homeostasis. Carboxemia with increasing end-tidal CO(2) and partial pressure of CO(2) (p <0.001), acidosis with decreasing pH (p <0.001), and base deficiency with decreasing actual base excess (p <0.001), standard base excess and standard bicarbonate and acid excess with increasing hydrogen bicarbonate (p <0.05 and <0.01) were found. Desaturation (p <0.01) with decreasing oxyhemoglobin p <0.05) and hemoglobin oxygen affinity (p <0.01) were also found. Carboxemia with acidosis was more pronounced with higher (p <0.01) than with lower (p >0.05) intraperitoneal pressures, and also with spontaneous breathing (p <0.05) and superficial ventilation (p <0.001) than with optimal ventilation, resulting in metabolic hypoxemia.

CONCLUSION

In superficially ventilated and spontaneously breathing rabbits, CO(2) pneumoperitoneum profoundly affected blood gases, acid-base balance, and oxygen homeostasis, resulting in metabolic hypoxemia. With optimal ventilation and low intraperitoneal pressure carboxemia, respiratory acidosis, and changes in oxygen metabolism were minimal.

Reduction of CO(2)-pneumoperitoneum-induced metabolic hypoxaemia by the addition of small amounts of O(2) to the CO(2) in a rabbit ventilated model. A preliminary study

BACKGROUND

CO(2)-pneumoperitoneum used in endoscopic surgery induces system effects by CO(2) absorption. This study investigated the effect of the addition of O(2) to CO(2)-pneumoperitoneum, upon CO(2) absorption.

METHODS

The effect of a pneumoperitoneum using 100% CO(2) or 94% CO(2) + 6% O(2) upon arterial blood gases, acid base and O(2) homeostasis was evaluated. In series A suboptimal ventilation and a pneumoperitoneum pressure (PP) of 10 mmHg was used. In series B adequate ventilation and PP of 6 mmHg was used.

RESULTS

CO(2)-pneumoperitoneum profoundly affected blood gases and acid base homeostasis i.e. increasing pCO(2), HCO(3)(P < 0.001) and lactate concentrations (P < 0.05) and decreasing pH, actual base excess and standard bicarbonate (P < 0.001), resulting in metabolic hypoxaemia with desaturation, lower pO(2) (P < 0.001) and O(2)Hb (P < 0.05). These effects were more pronounced with higher PP and suboptimal ventilation.

CONCLUSION

CO(2)-pneumoperitoneum profoundly affected blood gases and acid base homeostasis resulting in metabolic hypoxaemia. The addition of 6% of O(2) to the CO(2)-pneumoperitoneum prevented these effects to a large extent. If these preliminary data are confirmed in the human, the addition of a few percent of O(2) to CO(2) could become important for endoscopic surgery of long duration, especially in obese patients with limited cardiorespiratory adaptation and steep Trendelenburg.

Peritoneal mesothelial hypoxia during pneumoperitoneum is a cofactor in adhesion formation in a laparoscopic mouse model

OBJECTIVE

To develop a laparoscopic mouse model to evaluate the hypothesis that mesothelial hypoxia during pneumoperitoneum is a cofactor in adhesion formation.

DESIGN

Prospective randomized trials.

SETTING

Academic research center.

ANIMAL(S)

One hundred thirty female Naval Medical Research Institute (NMRI) mice.

INTERVENTION(S)

Adhesions were induced by opposing monopolar lesions in uterine horns and pelvic side walls during laparoscopy and evaluated after 7 or 28 days under microscopic vision during laparotomy. The following pneumoperitoneum variables were assessed: duration (10 or 60 minutes), insufflation pressure (5 or 15 cm of water), insufflation gas (CO(2) or helium), and addition of oxygen (0-12%).

MAIN OUTCOME MEASURE(S)

Adhesions were scored quantitatively and qualitatively for extent, type, and tenacity.

RESULT(S)

Scoring of adhesions 7 or 28 days after laparoscopic surgery was comparable. Adhesions increased with duration of pneumoperitoneum and with insufflation pressure and decreased with the addition of oxygen. Half-maximal reduction of adhesions was obtained at 1.5% oxygen, whereas a maximal reduction required only 2%-3%. The effect of CO(2) and helium was similar.

CONCLUSION(S)

These data demonstrate the feasibility of the intubated laparoscopic mouse model and confirm previous observations in rabbits, indicating that mesothelial hypoxia plays a key role in adhesion formation.