Carlos Roger Molinas

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.

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.

Feasibility and construct validity of a novel laparoscopic skills testing and training model

The apprentice–tutor model was useful for training surgeons for many years, but the complexity of surgical technology in the 21st century, especially endoscopic surgery, has exponentially increased the demands for surgical education. Therefore, more and more people now accept that endoscopic surgery, demanding as it requires specific skills, should also be taught outside the operating theatre. Although many systems, including animal models and simulators, have been proposed, an in-house structured and validated method for testing and training laparoscopic skills is missing in gynaecology. We have developed a laparoscopic skills testing and training (LASTT) model and performed two studies evaluating its feasibility and the construct validity of three different exercises (camera navigation, camera navigation and forceps handling, and forceps handling and bi-manual coordination), specifically selected to test and train laparoscopic psychomotor skills (LPS). In the first study, ten experts and 14 novices repeated each exercise between 20 and 30 times. The results demonstrated that the model is useful for testing and training laparoscopic skills. Clear learning curves were observed for both experts and novices, with better scores for the former at the beginning and the end of the study, proving the construct validity of the model. In the second study, 42 experts and 241 novices repeated each exercise three times during skill evaluation workshops organised by the European Academy of Gynaecological Surgery. The results confirmed the construct validity of the model. In conclusion, the LASTT model seems a cost-effective tool for providing an in-house program for continuous training and evaluation of LPS in all surgical disciplines in which laparoscopic procedures are, or might be, performed.

Pathogenesis CO2 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.

A valid model for testing and training laparoscopic psychomotor skills

This study aims to evaluate the face and construct validity of the Laparoscopic Skills Testing and Training (LASTT) model, developed by the European Academy of Gynaecological Surgery (EAGS) for assessing laparoscopic psychomotor skills (LPS). This study is designed based on the Canadian Task Force II-1. This study was conducted in workshops organised by the EAGS in 2008 and 2009. One hundred ninety-nine gynaecologists were classified in three groups according to their exposure to laparoscopy (G1: no/little, G2: intermediate, G3: important). Participants performed three repetitions of three exercises (E1: camera navigation, E2: hands–eyes coordination, E3: bimanual coordination) with measurable objectives to accomplish within a limited time frame. The face validity of the model was assessed by an 11-item questionnaire using a 10-cm visual analogue scale. Q1–Q8 evaluated its capacity for testing and training LPS and Q9–Q11 its relevance for actual laparoscopic surgery. The score of each exercise was obtained by dividing the time to correct performed exercise by the number of objectives effectively accomplished. The correlation between E1–E3 scores and the level of exposure to laparoscopy was evaluated, and the scores of the different groups were compared to assess the construct validity. Participants gave a favourable opinion about the model without inter-group differences. In E1–E3, the scores correlated with the level of previous exposure to laparoscopic procedures, more-experienced participants achieving better results than less-experienced participants. The data demonstrate the face and construct validity of the LASTT model, suggesting that it can be a useful tool for training and evaluation of LPS in surgical disciplines that perform laparoscopic procedures.

Prevention of Adhesions with Crystalloids during Laparoscopic Surgery in Mice

STUDY OBJECTIVE To evaluate the effect of saline and Ringers lactate solutions in preventing adhesions during laparoscopic surgery in mice. DESIGN Prospective, randomized trial (Canadian Task Force classification I). SETTING Academic research center. SUBJECTS Ninety-two female Naval Medical Research Institute mice. INTERVENTION Adhesions were induced laparoscopically by opposing bipolar lesions in the uterine horns and pelvic sidewalls, and saline or Ringers lactate solution was added at different times during the procedure. MEASUREMENTS AND MAIN RESULTS Adhesions were scored quantitatively and qualitatively for extent, type, and tenacity after 7 days under microscopic vision during laparotomy. After 45 minutes of pneumoperitoneum, neither solution reduced adhesion formation, but when added immediately after surgery they did (p = 0.002). Coagulation was not significantly different with addition of either solution immediately after coagulation. In the third experiment the presence of fluid during pneumoperitoneum decreased adhesion formation (p = 0.0001) but Ringers lactate was more effective than saline (p = 0.0005). CONCLUSION Crystalloids reduced CO(2) pneumoperitoneum-enhanced adhesion formation in a laparoscopic mouse model, but Ringers lactate solution was more effective than saline.

Reduction of CO2‐pneumoperitoneum‐induced metabolic hypoxaemia by the addition of small amounts of O2 to the CO2 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.

Defining a structured training program for acquiring basic and advanced laparoscopic psychomotor skills in a simulator

The effect of different structured training programs on basic laparoscopic psychomotor skills (LPS), as assessed by hand–eye coordination (HEC), and on advanced LPS, as assessed by laparoscopic intracorporeal knot tying (LICK), was evaluated. Sixty gynecologists without laparoscopic experience were randomly allocated to three groups for different HEC training and similar LICK training. During HEC training, group 1 (G1) trained the dominant hand (DH) and the nondominant hand, G2 trained the DH only, and G3 did not train at all. All groups then underwent LICK training. HEC and LICK training consisted of 60 repetitions of the relevant task. All participants were tested at the beginning of the study (T1), before LICK training (T2), and after LICK training (T3). The time to correctly performed exercise was scored. The groups had comparable scores at T1. At T2, G1 and G2 improved their relevant HEC scores (both hands in G1, DH in G2), and LICK scores improved according to the previous HEC training (G1 > G2 or G3 and G2 > G3). At T3, all groups further improved their LICK scores up to the same level. The LICK training did not provide any additional improvement in HEC for G1 and G2, but it further improved HEC for G3, though not up to the same level of the other groups. This study confirms that training improves laparoscopic skills and indicates that many repetitions are required for reaching proficiency. Full acquisition of LPS (e.g., HEC) facilitates the acquisition of more complex laparoscopic tasks (e.g., LICK). Mastering LICK is not sufficient for acquiring HEC skills, the clinical relevance of which still needs to be evaluated. Mastering both skills before starting a training program in the operating theater is advisable.

The impact of the learning curve on adhesion formation in a laparoscopic mouse model

OBJECTIVE To evaluate the impact of surgeon training on adhesion formation in a laparoscopic mouse model. Laparoscopic surgery and bowel manipulation was demonstrated to enhance postoperative adhesion formation. DESIGN Prospective randomized, controlled trial. SETTING University laboratory research center. ANIMAL(S) 200 BALB/c and 200 Swiss female mice. INTERVENTION(S) Adhesions were induced by opposing bipolar lesions and 60 minutes of pneumoperitoneum. Each surgeon operated on 80 mice (40 Swiss and 40 BALB/c), the only variable thus being his/her increasing experience. Some surgeons were already experienced gynecologists, others were starting their training. MAIN OUTCOME MEASURE(S) End points were the duration of surgery while performing the lesions. The adhesion formation was scored quantitatively (proportion and total) and qualitatively (extent, type, and tenacity) after 7 days. RESULT(S) With training, duration of surgery and adhesion formation decreased exponentially for all surgeons, whether experienced or not. Experienced surgeons had initially a shorter duration of surgery, less adhesion formation, and less de novo adhesions than inexperienced surgeons. CONCLUSION(S) These data suggest that laparoscopic skills improve with training, leading to a decrease in the duration of surgery and formation of adhesions. Therefore completion of a standardized learning curve should be mandatory when initiating adhesion formation studies both in laboratory or clinical setting.

Angiogenic factors in peritoneal adhesion formation

Abdominal surgery is considered as the leading cause of peritoneal adhesions and almost universally as adhesiogenic. Peritoneal injury at the time of surgery initiates an inflammatory reaction determining fibrin deposition on the wound surface. Depending on the balance between the different components of the plasminogen system, this fibrin can be either lysed, leading to normal peritoneal healing, or organised, serving as a scaffold for fibroblast ingrowth, extracellular matrix deposition and angiogenesis, leading to adhesion formation. The mechanism underlying the predisposition to form adhesions in some patients and in some specific anatomic sites and not in others after similar surgical procedures remains unknown. In spite of the many attempts proposed over the years for reducing the incidence of adhesion formation, peritoneal adhesions remain a major clinical problem, inducing intestinal obstruction, pelvic pain, female infertility and difficulties at the time of re-operation. The available evidence indicates that understanding the adhesion formation process at the molecular level is essential for developing successful strategies for preventing adhesions. Fortunately, the advancement in molecular biology during the last years has led to the identification of many molecules with the potential of regulating inflammatory and immune responses, tissue remodelling and angiogenesis, key events in peritoneal healing and adhesion formation. This review focuses on the role of angiogenesis and angiogenic factors in peritoneal adhesion formation.