The optimum pneumoperitoneum pressure for laparoscopic surgery in the rat model. A detailed cardiorespiratory study

Development and technical validation of an ultrasound nebulizer to deliver intraperitoneal pressurized aerosols in a rat colon cancer peritoneal metastases model

Background/aim

To develop and validate a nebulizer device for anti-cancer research on pressurized intraperitoneal aerosol supply in a preclinical peritoneal metastases (PM) rat model.

Material and methods

For aerosol generation, an ultrasonic nebulizer (USN) was modified. Aerosol analyses were performed ex-vivo by laser diffraction spectrometry (LDS). Intraperitoneal (IP) ^99mtechnetium sodium pertechnetate (^99mTc) aerosol distribution and deposition were quantified by in-vivo single photon emission computed tomography (SPECT/CT) and compared to liquid IP instillation of equivalent volume/doses of ^99mTc with and without capnoperitoneum. PM was induced by IP injection of HCT116-Luc2 human colon cancer cells in immunosuppressed RNU rats. Tumor growth was monitored by bioluminescence imaging (BLI), ¹⁸F-FDG positron emission tomography (PET) and tissues examination at necropsy.

Results

The USN was able to establish a stable and reproducible capnoperitoneum at a pressure of 8 to 10 mmHg. LDS showed that the USN provides a polydisperse and monomodal aerosol with a volume-weighted diameter of 2.6 μm. At a CO₂ flow rate of 2 L/min with an IP residence time of 3.9 s, the highest drug deposition efficiency was found to be 15 wt.-%. In comparison to liquid instillation, nebulization showed the most homogeneous IP spatial drug deposition. Compared to BLI, ¹⁸F-FDG-PET was more sensitive to detect smaller PM nodules measuring only 1–2 mm in diameter. BLI, ¹⁸F-FDG PET and necropsy analyses showed relevant PM in all animals.

Conclusions

The USN together with the PM rat model are suitable for robust and species-specific preclinical pharmacological studies regarding intraperitoneal delivery of pressurized aerosolized drugs and cancer research.

Effect of laparoscopic liver resection versus the open technique on hepatocyte regenerating activity in the rat

BACKGROUND

Laparoscopic liver resection offers a safe and feasible option primarily for the excision of hepatic neoplasms. Timely recovery of liver volume is a key factor for improving prognosis and post-operative mortality of patients undergone liver resection. The aim of the present study was to compare liver regeneration after laparoscopic over open partial hepatectomy.

METHODS

Wistar rats were subjected to laparoscopic 70% hepatectomy (group LAP-HEP), open 70% hepatectomy (group HEP), sham operation (group Sham) or no intervention (group Control). At various timepoints following operation (1 h-2 weeks), the liver was excised to assess relative liver weight, thiobarbituric acid reactive substances (TBARS) levels, mitotic activity, tissue expression of Nuclear Factor-κB (NFκB), Intercellular Adhesion Molecule-1 (ICAM-1) and Vascular Cell Adhesion Molecule-1 (VCAM-1) and the histopathologic profile.

RESULTS

No differences were seen in relative liver weight between hepatectomy groups. Mitotic index was increased in all operative study groups, being higher in group LAP-HEP than in group HEP. TBARS levels were higher in group LAP-HEP compared to group HEP. NFκB and VCAM-1 tissue expression scores were increased in all operative study groups with VCAM-1 being higher in group HEP, while ICAM-1 was overexpressed only in hepatectomy groups. Mild histopathologic lesions were noted in hepatectomy groups with the histopathologic score being higher in group HEP (24 h).

CONCLUSIONS

Laparoscopic liver resection enhanced hepatocyte mitotic activity which was accompanied by mild oxidative stress and a less pronounced local inflammatory response and tissue injury to that of the open technique.

Protective effects of postconditioning in transvaginally created pneumoperitoneum

There are reports of ischemic complications in clinical practice after laparoscopy using pneumoperitoneum. Conditioning has a beneficial effect for various ischemic diseases. This experimental study was designed to evaluate the effects of postconditioning in transvaginally created pneumoperitoneum. Sixty adult female rats, weighing 300±50 g were divided into four equal groups. Pneumoperitoneum was created by CO₂ insufflation under a pressure of 10 mmHg. Rats in the first group (sham) were subjected to only sham-operation or gas insufflation. The second group (TV/PP) was subjected to pneumoperitoneum for 60 min followed by 30 min of desufflation. The third group (post-5) was subjected to pneumoperitoneum for 60 min followed by 5 min of desufflation, 5 min of insufflation and again followed by 30 min of desufflation. The fourth group (post-2.5) was subjected to pneumoperitoneum for 60 min followed by 2.5 min of desufflation and 2.5 min of insufflation-repeated in two cycles- and then followed by 30 min of desufflation. The rats were sacrificed, and blood was collected after 30 min, 2 and 6 h from the last desufflation. Levels of oxidative stress markers, malondialdehyde (MDA), superoxide dismutase (SOD), reduced glutathione (GSH), sulfhydryl groups (SH) and inflammatory cytokine TNF-α, were analyzed. Levels of MDA in the post-5 group were significantly reduced compared to the TV/PP and post-2.5 groups. The level of GSH in TV/PP animals was markedly reduced compared to the Sham, Post-5 and Post-2.5 groups. In addition, levels of SH were increased in the Post-5 group in comparison to the Sham, TV/PP and Post-2.5 groups. No difference in the activity of SOD between the groups was found, and the concentration of TNF-α in TV/PP animals was significantly higher than that in the Sham and postconditioning groups. Overall, the results of the present study indicate that postconditioning can reduce pneumoperitoneum-induced oxidative injury.

Physiologic Changes in a Small Animal Model for Neonatal Minimally Invasive Surgery

BACKGROUND

Minimally invasive surgery (MIS) has gained increasing importance in neonatal surgery but the effects on neonatal physiology remain unclear. We aimed to characterize the impact of capnoperitoneum on physiologic parameters in a small animal model for neonatal MIS.

MATERIAL AND METHODS

Twenty-four 10-day-old Sprague Dawley rats underwent inhalative anesthesia (1% isoflurane in 100% O₂ 250 mL/minutes) and were allowed to breathe spontaneously. CO₂ was insufflated into the abdominal cavity for 1 hour via a 24G cannula. Anesthetized litter mates without insufflation served as sham controls, those without any treatment as external controls. Continuous monitoring included O₂-saturation, heart and respiration rate, pulse and breath distension. After euthanasia, blood gas analysis was performed.

RESULTS

All animals survived the experiment. Capnoperitoneum was best tolerated at a pressure of 2 mmHg and a flow of 0.5 L/minutes. A significant decrease in heart rate was observed within the first 30 minutes of insufflation comparing the CO₂ and sham group (P < .05). In both, the CO₂ and sham group, postmortem pH-levels were lower and pCO₂ levels were higher compared to external controls (P < .05). Additionally, levels of pCO₂ were higher but pH levels remained unchanged in the CO₂ compared to sham group (P < .05).

CONCLUSION

We established a small animal model for neonatal laparoscopy. A pressure of 2 mmHg and flow of 0.5 L/minutes induced physiologic alterations but was well tolerated by the animals. These settings can be used in future studies on the impact of the capnoperitoneum in neonatal MIS.

The effect of carbon dioxide pneumoperitoneum on the healing colonic anastomosis in rats

PURPOSE

To investigate the effects of pneumoperitoneum on colonic anastomosis healing.

METHODS

Colonic anastomosis was performed in 120 rats divided into four groups: Group I - pneumoperitoneum before laparotomy, Group II - pneumoperitoneum after laparorrhaphy, Group III - pneumoperitoneum before laparotomy and after laparorrhaphy, Group IV - no pneumoperitoneum (control group). Pneumoperitoneum pressure was 5 mmHg. Animals were killed on the 3rd, 7th and 14th postoperative day. Histopathological features, anastomosis breaking strength, collagen histomorphometry and hydroxyproline concentration were assessed.

RESULTS

Breaking strength between groups: (day 3, p=0.165; day 7, p=0.219; day 14, p=0.539). Histopathology revealed that group II had, on day 7, less infiltration of mononuclear cells (p=0.006), greater infiltration of polymorphonuclear cells (p=0.001) and greater necrosis (p=0.001); and on day 14, less fibrosis. Histomorphometry revealed a decrease in collagen in groups I and III (p<0.001) on day 7 and an increase in groups I and II on day 14 (p<0.001). Hydroxyproline concentration was similar for groups on days 3 (p=0.152), 7 (p=0.913) or 14 (p=0.981).

CONCLUSION

Carbon dioxide does not impair the healing of colonic anastomosis in rats.

Does prolonged pneumoperitoneum affect the kidney? Oxidative stress, stereological and electron microscopy study in a rat model

PURPOSE

Pneumoperitoneum (Pp) at 12 to 15 mmHg in rats is associated with kidney damage. However, Pp at 8 mmHg is now known to best correlate to working pressures used in humans. Thus the aim of this work was to study the kidney of rats submitted to prolonged Pp at 8 mmHg.

MATERIALS AND METHODS

Rats were divided into a Sham group (n = 14), submitted to anesthesia, and a Pp group (n = 14), submitted to Pp at 8 mmHg, followed by deflation. In both groups, 7 animals were immediately killed and their kidneys were used for oxidative stress analyses. The remaining 7 rats in each group were evaluated after 6 weeks for the number of glomeruli and podocyte morphology.

RESULTS

For all analyzed parameters Sham and Pp groups presented no statistical difference.

CONCLUSION

When submitted to adequate Pp pressures (8 mmHg), no kidney damage occurs in rats.

Kidney safety during surgical pneumoperitoneum: an experimental study in rats

BACKGROUND

Elevations of intraabdominal pressure during laparoscopic procedures may lead to oliguria or anuria in mammals. Despite this, previous research has not been able to confirm an associated kidney injury. This study aimed to investigate the occurrence of an early kidney lesion secondary to surgical pneumoperitoneum in a rat model using the expression of neutrophil gelatinase-associated lipocalin (N-GAL) as a biomarker for early kidney injury.

METHODS

In this study, 20 male Sprague-Dawley rats under general anesthesia and mechanically ventilated were allocated to one of five experimental time-dependent groups: group 1 (1-h control), group 2 (1-h pneumoperitoneum), group 3 (2-h control), group 4 (2-h pneumoperitoneum), and group 5 (positive kidney injury group induced by intravenous administration of cisplatin 7.5 mg/kg). To evaluate the renal expression of N-GAL 24 h after the procedure, all the rats underwent a 2-h urine output evaluation as well as laparotomy and bilateral nephrectomy performed sequentially to investigate the presence of renal injury using immunofluorescence qualification and western blotting.

RESULTS

Urine output was reduced and N-GAL expression was increased in the animals from the cisplatin group. The animals undergoing 1- or 2-h pneumoperitoneum displayed urine output and N-GAL expression similar to that of the animals from the matching control groups.

CONCLUSIONS

Under the experimental conditions of this study, the animals with normal preoperative renal function did not show any type of acute kidney injury associated with the presence of a stabilized surgical pneumoperitoneum.

Evaluation of a simple valve mechanism used to stabilize intraabdominal pressure during surgically induced pneumoperitoneum in small animals

BACKGROUND

Preventing sudden changes in intraabdominal pressure (IAP) during surgical pneumoperitoneum may reduce adverse events. This study aimed to describe a valve system that stabilizes intraabdominal pressure, minimizing complications of erratic fluctuations in IAP.

METHODS

Five male Sprague-Dowley rats were submitted to pneumoperitoneum, with the insufflator set sequentially at 5, 10, and 15 mmHg for each rat. Measures of IAP were taken initially without the valve and then using the same insufflator levels with the valve system regulated to three different pressures (5, 10, and 15 mmHg). The mean of the three highest registered pressures during a 15-min observation was used as the maximal pressure, and the mean of the three lowest registered pressures was used as the minimal pressure for each experimental setting.

RESULTS

Without the valve system, the pressure level set by the insufflator correlated poorly with the actual IAP. When the valve system was used, the IAP pressure was limited by the valve settings regardless of the insufflator settings. Also, the variability of IAP was significantly higher when no valve was used than in all situations that had implementation of the system.

CONCLUSIONS

The valve system was very effective in stabilizing IAP, allowing a reproducible and reliable estimate of IAP and greatly reducing the variability resulting from the cycling mechanism of the insufflator. Due to the small dimensions of intracorporeal cavities in the newborn, this mechanism may help to improve safety when neonatal video-assisted surgery is performed.

Laparoscopic surgery in a rat model

BACKGROUND

The rat is increasingly being used in laparoscopic research. Laparoscopic microsurgical training is critical in order to develop new surgical indications in pediatric patients. This report evaluates laparoscopic splenectomy and nephrectomy in a rat model.

MATERIALS AND METHODS

A Wistar rat (weight between 250 and 400 g) was placed in the supine position. Inhaled 3% halothane anesthesia was administered. A Veress needle is inserted in the right-upper abdomen. After establishing a pneumoperitoneum of 3-4 mm Hg, a 2- or 5-mm trocar was placed, according to the procedure. A 2-mm 0-degree endoscope was used. Two additional 2- or 5-mm trocars were then placed. Laparoscopic splenectomy involved two-handed dissection, intracorporeal ligation, and the division of gastrosplenic attachments and hilar and short gastric vessels. Laparoscopic nephrectomy was done by intracorporeal ligation and division of the renal vessels and the ureter after mobilization of the kidney.

RESULTS

Laparoscopic splenectomy was performed in 8 rats; laparoscopic nephrectomy was done in 4 rats. Operative time was 25-40 minutes for splenectomy and from 30 to 65 for nephrectomy. Postoperatively, 4 rats died from hemorrhage. No wound infections occurred at the port sites.

CONCLUSIONS

Laparoscopic splenectomy and nephrectomy in an experimental rat model is technically feasible and may provide an excellent training model for pediatric minimally invasive surgery.

Influence of Pneumoperitoneum on Small Bowel Anastomoses: A Histological Analysis in the Rat Model

Laparoscopic techniques are increasingly applied for the treatment of diverse gastrointestinal diseases. With regard to reports of a pronounced decrease of intra-abdominal blood flow with increasing intra-abdominal pressure, the present study investigates the impact of pressure and gas type on ischemia in small bowel anastomoses in the rat model. Laparotomy and ileoileal anastomosis were performed in 39 male Sprague-Dawley rats. A CO2 or helium pneumoperitoneum of 3 mm Hg or of 6 mm Hg was maintained before and after anastomoses. Rats in the control group received no pneumoperitoneum. Animals were sacrificed after 5 d, and the anastomotic region was explanted for subsequent histopathological examinations. In hematoxylin and eosin (HE)-stained sections, the Chiu score, villi configuration, and number of goblet cells were analyzed. Proliferation (Ki67) and expression of a matrix metalloproteinase (MMP-8) were examined by immunohistochemistry. Mucosal damage according to the scoring system by Chiu, the number of goblet cells, the villus length, the proliferation (Ki67), and the submucosal expression of MMP-8 was similar in all groups. Our results suggest that within a certain range of pressures and time, laparoscopic assisted surgery using CO2 pneumoperitoneum can be performed safely. Helium gas offers no advantages over CO2.

Dissemination of bacteria labeled with technetium-99m after laparotomy and abdominal insufflation with different CO2 pressures on rats

PURPOSE: To asses the dissemination of bacteria labeled with technetium-99m (99mTc) from peritoneal cavity after different surgical procedures. METHODS: Bacteria of the Escherichia coli species labeled with 99mTc were used in a concentration of 10(8) units of colony-makers for ml (UFC/ml) and 1ml was inoculated through intra-peritoneal via. Forty-eight rats were divided into four groups: control, laparotomy, pneumoperitoneum with 10mmHg and pneumoperitoneum with 20mmHg of CO2. Procedures were performed 20 min after injection of the inoculum and lasted 30 min. Animals were sacrificed after six hours (Group 1) and 24 hours (Group 2). Samples of blood, liver and spleen were collected for radioactivity counting. RESULTS: After six hours, indirect detection of the bacteria in different organs was uniform in all groups. After 24 hours, a larger detection of technetium was observed in the livers of animals of the group insufflated with 20mmHg of CO2, when compared with those of control group (p<0.01). The other groups did not present statistically significant variations. CONCLUSIONS: The use of a higher intra-abdominal pressure was associated with a higher bacterial dissemination to the liver. The application of lower intra-abdominal pressures may be associated with a lower dissemination of the infectious status during laparoscopic approach of peritonitis status.

Laparoscopic surgery and the parasympathetic nervous system

BACKGROUND

Laparoscopic surgery preserves the immune system and has anti-inflammatory properties. CO2 pneumoperitoneum attenuates lipopolysaccharide (LPS)-induced cytokine production and increases survival. We tested the hypothesis that CO2 pneumoperitoneum mediates its immunomodulatory properties via stimulation of the cholinergic pathway.

METHODS

In the first experiment, rats (n = 68) received atropine 1 mg/kg or saline injection 10 min prior to LPS injection and were randomization into four 30-min treatment subgroups: LPS only control, anesthesia control, CO2 pneumoperitoneum, and helium pneumoperitoneum. In a second experiment, rats (n = 40) received atropine 2 mg/kg or saline 10 min prior to randomization into the same four subgroups described previously. In a third experiment, rats (n = 96) received atropine 2 mg/kg or saline 10 min prior to randomization into eight 30-min treatment subgroups followed by LPS injection: LPS only control; anesthesia control; and CO2 or helium pneumoperitoneum at 4, 8, and 12 mmHg. In a fourth experiment, rats (n = 58) were subjected to bilateral subdiaphragmatic truncal vagotomy or sham operation. Two weeks postoperatively, animals were randomized into four 30-min treatment subgroups followed by LPS injection: LPS only control, anesthesia control, CO2 pneumoperitoneum, and helium pneumoperitoneum. Blood samples were collected from all animals 1.5 h after LPS injection, and cytokine levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Serum tumor necrosis factor-alpha (TNF-alpha) levels were consistently suppressed among the saline-CO2 pneumoperitoneum groups compared to saline-LPS only control groups (p < 0.05 for all four experiments). All chemically vagotomized animals had significantly reduced TNF-alpha levels compared to their saline-treated counterparts (p < 0.05 for all), except among the CO2 pneumoperitoneum-treated animals. Increasing insufflation pressure with helium eliminated differences (p < 0.05) in TNF-alpha production between saline- and atropine-treated groups but had no effect among CO2 pneumoperitoneum-treated animals. Finally, vagotomy (whether chemical or surgical) independently decreased LPS-stimulated TNF-alpha production in all four experiments.

CONCLUSION

CO2 pneumoperitoneum modulates the immune system independent of the vagus nerve and the cholinergic pathway.

O papel do pneumoperitônio na avaliação de parâmetros respiratórios e hemodinâmicos de ratos anestesiados, com ou sem intubação intratraqueal

OBJETIVO: Estudar as alterações hemodinâmicas e respiratórias em ratos submetidos ou não ao pneumoperitônio com CO2, sob anestesia com ou sem intubação intratraqueal. MÉTODO: Ratos machos (n = 40), albinos, com peso médio de 300g, idade de três meses, foram randonizados em quatro grupos: GA - anestesia com intubação endotraqueal por uma hora e com pneumoperitônio de 4mmHg de CO2; GB - anestesia sem intubação endotraqueal por uma hora e com pneumoperitônio de 4mmHg de CO2; GC - anestesia sem intubação endotraqueal por uma hora e sem pneumoperitônio; GD - anestesia com intubação endotraqueal por uma hora, sem pneumoperitônio. Foram registrados os valores da pressão arterial média (PAM), pressão parcial de gás carbônico (pCO2), freqüência cardíaca (FC), freqüência respiratória (FR), pressão venosa central (PVC), potencial hidrogeniônico acidose (pH), saturação de oxigênio periférico (spO2), bicarbonato (HCO3-) e saturação de oxigênio no sangue arterial (SO2,). Os dados foram coletados no início do experimento (M0), após 30 minutos (M1) e após 60 minutos (M2). RESULTADOS: Em GA e GC (grupos com pneumoperitônio) ocorreu aumento da PAM, PCO2, HCO3-, FR, PVC e uma diminuição do pH, SO2, spO2 e da FC em relação aos animais sem pneumoperitônio. Por outro lado a intubação intratraqueal demonstrou atenuar estas alterações nos animais com até uma hora de anestesia. CONCLUSÃO: A anestesia geral com intubação endotraqueal associada ao pneumoperitônio de 4mmHg, por um período de uma hora, mostrou vantagens do ponto de vista respiratório e hemodinâmico, em relação aos animais com pneumoperitônio e sem intubação e também sobre aqueles com até quatro horas de anestesia, apesar da intubação.

Videoendoscopic endotracheal intubation in the rat: A comprehensive rodent model of laparoscopic surgery1,2

BACKGROUND

Peritoneal absorption of CO(2) during abdominal insufflation in laparoscopy may disrupt the acid-base equilibrium and alter the physiological response to stress. Current nonventilated rodent models of laparoscopy do not manage the CO(2) load of pneumoperitoneum, but ventilated surgical rodent models are invasive (tracheotomy) and may independently induce the inflammatory response.

MATERIALS AND METHODS

A comprehensive rodent model of laparoscopy was developed. Rats were randomized to receive anesthesia alone, anesthesia plus CO(2) pneumoperitoneum, or anesthesia plus CO(2) pneumoperitoneum with videoendoscopic intubation and mechanical ventilation. Arterial blood-gas analysis was performed at baseline and after 30 min of intervention.

RESULTS

Baseline pH, pCO(2), and HCO(3)(-) arterial blood gas parameters were normal for all rats. After 30 min, pCO(2) and pH changed slightly but remained normal among rats receiving anesthesia alone (pCO(2) = 46.5 +/- 1.9; pH = 7.365 +/- 0.009) whereas animals receiving anesthesia plus CO(2) pneumoperitoneum that were dependent on spontaneous respiration for ventilation developed significant hypercarbic acidosis (pCO(2) = 53.2 +/- 1.9, P < 0.05; pH = 7.299 +/- 0.011, P < 0.001). This acidosis was completely corrected with increased minute ventilation in intubated rats receiving mechanical ventilation (pCO(2) = 36.8 +/- 1.5, P < 0.001; pH = 7.398 +/- 0.011, P < 0.001).

CONCLUSIONS

CO(2) pneumoperitoneum induces significant hypercarbic acidosis in nonventilated rats. Noninvasive endotracheal intubation is feasible in the rat with videoendoscopic assistance. Our noninvasive rodent model of laparoscopic surgery controls for anesthesia- and capnoperitoneum-related acid-base changes and provides an environment in which the biological response to pneumoperitoneum can be studied precisely.

Pneumoperitoneum impairs blood flow and augments tumor growth in the abdominal wall

BACKGROUND

Despite several clinical and experimental studies, the mechanisms behind the development of port site metastases in laparoscopic surgery have remained largely unknown. The current study was designed to investigate the effect of pneumoperitoneum on blood flow in the abdominal wall and its possible effects on tumor growth at this site.

METHODS

A total of 40 Wistar Fu rats had a laser Doppler probe placed on their left rectus muscle and a suspension of 50,000 adenocarcinoma cells was injected into their right rectus muscle. The experimental group (n = 20) was insufflated with air at 10 mmHg for 45 min while abdominal blood flow was registered before and during insufflation and after exsufflation. The control group (n = 20) was not insufflated but the blood flow was recorded in the same manner. After 9 days, all animals were killed and the occurrence of tumor was observed. The tumors were analyzed with respect to weight and volume.

RESULTS

The insufflation caused an 82% reduction in blood flow in the experimental group (p < 0.001). No reduction in blood flow was registered in the control group. Tumor nodules developed significantly more often in the insufflated group (20/20) compared to the controls (14/20) (p = 0.016). Tumor weight (p = 0.003) and volume (p < 0.001) were significantly increased in the insufflated group.

CONCLUSIONS

Pneumoperitoneum seems to enhance tumor growth. It also causes a significant reduction in blood flow in the abdominal wall, which may contribute to the increased susceptibility of tumor take.

Modelo experimental de esplenectomia laparoscópica em ratos

OBJETIVO: Desenvolver um modelo de esplenectomia laparoscópica em ratos. MÉTODOS: Foram utilizados trinta e cinco ratos machos ( Rattus Norvegicus Albinus, linhagem Wistar),pesando 250 +/- 50 g .Os animais foram anestesiados com cetamina e xylazina e foi estabelecido pneumoperitônio de CO2 com pressão de 7 mmHg, através da agulha de Veress. Após pneumoperitônio, dois trocateres de 5 mm e um de 11mm foram alocados na parade abdominal obedecendo a triangulação. O ligamento gastroesplênico foi dissecado para mobilização do baço. Os vasos hilares foram dissecados e eletrocoagulados utilizando a pinça "Maryland" e o gancho "HooK". Um "endobag" adaptado, foi utilizado para retirar o orgão da cavidade abdominal. RESULTADOS: Um animal (2,86%) morreu na indução anestésica. Após um período de observação de oito dias, trinta animais sobreviveram (85,7 %) e quatro (11,42%) Morreram no pós-operatório imediato. Em relação às complicações, Aderências intra-abdominais foram encontradas em 25,71% dos animais (n=9). CONCLUSÃO: A esplenectomia laparoscópica é um modelo factível por conta da baixa taxa de mortalidade além do baixo custo para treinamento da técnica.

Modelo experimental de vasectomia laparoscópica em ratos

OBJETIVO: Descrever um modelo experimental de vasectomia laparoscópica em ratos. MÉTODOS: Foram utilizados 35 ratos Rattus norvegicus albinus da linhagem Wistar. Após a anestesia, os ratos foram submetidos ao pneumoperitôneo através da agulha de Veress com PCO2 de 7mmHg. Depois, foram transpassados pela parede abdominal um trocater de 11mm de espessura e dois trocateres com 5 mm de espessura. Através destes foram introduzidos na cavidade abdominal à ótica (10mm) e as pinças utilizadas na dissecção, cauterização e secção do canal deferente e seus vasos. RESULTADOS: Durante o ato operatório dois animais (5,74%) apresentaram sangramento, contido com cauterização. Ocorreu um óbito na indução anestésica (2,85%) e outro (2,85%) no quarto dia pós-operatório de causa não identificada. Após 08 dias havia 33 ratos vivos (94,28%). CONCLUSÃO: Neste modelo, o material cirúrgico é o mesmo utilizado em humanos e são aplicados todos os procedimentos básicos da cirurgia laparoscópica, tornando-o factível para o treinamento de acadêmicos, médicos residentes e cirurgiões.

Blood flow distribution during elevated intraperitoneal pressure in the rat

AIM

Oliguria is seen during elevated intraperitoneal pressure, but the physiological mechanisms are not yet clarified. The purpose of the present study was to investigate the changes in renal function, cardiac output and distribution of systemic blood flow (BF) that occur in connection with an elevation of intra-abdominal pressure (IAP) in a rat model by isotope-labelled microsphere technique.

METHODS

A 5 or 10 mmHg IAP was created by CO2 insufflation and maintained for 90 min in anaesthetized and mechanically ventilated rats. Rats with normal IAP served as controls. Blood flow and cardiac output measurements by injection of isotope-labelled microspheres were conducted at three time points. Acid-base balance, urine output, glomerular filtration rate (GFR) and urinary excretion products were also followed.

RESULTS

Glomerular filtration rate decreased [0.7-0.1 mL min(-1) g(-1) kidney weight (KW)] with elevated IAP, as did urine output (8.5-0.6 microL min(-1) g(-1) KW). Dramatic decreases were seen in renal excretion of sodium (by 97%), potassium (by 94%) and osmotic active substances (by 93%). Cardiac output was diminished by 54% at 5 mmHg and by 65% at 10 mmHg intraperitoneal pressure and systemic vascular resistance (SVR) was elevated threefold.

CONCLUSION

Cardiac output, measured by microsphere technique, decreased during elevated intraperitoneal pressure by CO2 in anaesthetized rats, while SVR was elevated and renal excretory functions were decreased to a large extent.

Repetitive pneumoperitoneum with ozonized oxygen as a preventive in lethal polymicrobial sepsis in rats

The aim of this study was to test whether repetitive pretreatments of rats with ozonized oxygen at relatively low gas volumes into the abdomen (20 ml per rat per day) have any beneficial or detrimental effects on the course of a polymicrobial-induced lethal peritonitis. Peritonitis was induced in a surgical or a nonsurgical model by usage of fecal material from the cecum. As the biological read out we used the mortality analysis. To include possible mechanisms by which ozone might influence the septic outcome, we characterized the gene expression of the pro-inflammatory cytokines IL-1beta, IL-2, and TNF-alpha mRNA in lymphoid organs. In both models, we found a significant beneficial influence of a dose-dependent O(2)/O(3 )pneumoperitoneum on the survival rate when compared to control animals or to room air. The ozone-enhanced survival seems to be independent from altered cytokine expression because there were no differences noticed in the levels of bacterial-induced gene expression of IL-1beta and TNF-alpha in septic animals pretreated with ozonized oxygen when compared to control animals.

Ação do pneumoperitônio com dióxido de carbono na translocação bacteriana em ratos

Objetivo: Investigar a translocação bacteriana decorrente da ação do pneumoperitônio com CO2 em ratos normais e em ratos com colite induzida. Métodos: Utilizaram-se 60 ratos distribuídos em seis grupos de 10 animais. No grupo simulação realizou-se laparotomia, manipulação de órgãos abdominais e síntese da parede; os dois grupos pneumoperitônio foram submetidos a pneumoperitônio por uma e três horas, respectivamente; no grupo colite, foi induzida colite e realizada laparotomia, manipulação de órgãos abdominais e síntese da parede; nos dois grupos colite pneumoperitônio induziu-se colite mais pneumoperitônio por uma e três horas, respectivamente. Sacrificados os animais, foram feitas as coletas dos rins, baço, fígado e linfonodos mesentéricos. Nos animais submetidos a colite induzida, foram ressecados 2cm de cólon para análise histológica. Nos órgãos ressecados pesquisou-se a presença de Escherichia coli e Enterococcus faecallis para verificar a translocação bacteriana. Resultados: Não ocorreram óbitos nos grupos estudados. Não houve diferença estatisticamente significante nos grupos de animais submetidos a colite. A ocorrência de translocação bacteriana nos diferentes órgãos independe do gênero da bactéria. Não há incremento da translocação bacteriana com relação a duração de pneumoperitônio (1 e 3h) tanto em ratos normais como nos submetidos a colite induzida. Conclusão: O pneumoperitônio induz a translocação bacteriana em ratos normais e a incrementa em ratos submetidos à colite.

Experimental assessment of tumor growth and dissemination of a microscopic peritoneal carcinomatosis after CO2 peritoneal insufflation or laparotomy

BACKGROUND

Based on clinical observations and previous animal studies, laparoscopic surgery for malignant disease is regarded as controversial. We used a rat model to measure and compare the tumor growth, proliferation, and dissemination of a microscopic peritoneal carcinomatosis after CO(2) intraperitoneal insufflation or laparotomy.

METHODS

Peritoneal carcinomatosis was induced in three groups of 27 BD IX rats each with intraperitoneal injections of 106 DHD/K12 cells, an aneuploid tumor cell line. At 48 h after tumor cell injection, the animals were randomly divided into three groups to undergo different types of intervention. All animals were anesthetized for 20 min (Halothane). The control group had no surgical intervention (group C), group I had CO(2) insufflation (7 mmHg),and group L had a midline laparotomy (5-cm). Neither bowel manipulation nor any other traumatic action was performed. Two weeks later, the rats were killed and the incidence, type, and dissemination of carcinomatosis were evaluated. We also measured the tumor's weight. Malignant omentum was sampled for flow cytometry analysis (DNA ploidy, S-phase fraction).

RESULTS

The incidence of carcinomatosis did not differ among the groups. The mean score of macroscopic characteristics of the carcinomatosis was 2.8 +/- 1.9 in group L, 2.9 +/- 1.9 in group I, and 3 +/- 1.9 in group C (NS). The location of the implants did not differ, except for parietal peritoneum location, which was more frequent in group L (p < 0.01). The tumor weight was 4.96 g +/- 3.2 in group L, 5.55 g +/- 3.2 in group C, and 5.75 g +/- 3.4 in group I (NS). The percentage of aneuploid cells and S-phase fraction did not differ statistically among the groups.

CONCLUSION

These results indicate that CO(2) insufflation does not cause more effects than laparotomy when tumors cells are present before the beginning of the surgery. Further studies are needed to determine the influence of other steps in laparoscopic surgery on tumor growth and dissemination.

Metabolic and hemodynamic effects of CO2 pneumoperitoneum in a controlled hemorrhage model

BACKGROUND

Intracavity infusion of fibrin sealant-based agents, as a novel modality to control internal bleeding, is associated with an increase of pneumoperitoneum (PP) pressure. The safe limit of such increase has not been well defined in hypovolemic subjects. The purpose of this study was to evaluate the hemodynamic and metabolic effects of increasing PP pressure and to define the limits of carbon dioxide (CO2) insufflation in a controlled hemorrhage rat model.

METHODS

Ninety male rats (474 +/- 6 g, 37 degrees +/- 1 degrees C) were anesthetized, and mechanically ventilated. Animals were randomly distributed among 14 groups (n = 6-8) with an increasing amount of blood loss (0, 10, 15, and 17.5 mL/kg) and 15 minutes of CO2 insufflation at 0, 5, 10, and 15 mm Hg starting 15 minutes after hemorrhage, followed by desufflation. Mean arterial pressure (MAP), heart rate, and survival were recorded and arterial and venous blood samples were collected at baseline, at 15 minutes after hemorrhage, after insufflation, and after desufflation procedures to determine arterial blood gases and lactic acid levels.

RESULTS

In nonhemorrhaged animals, increasing PP pressure up to 15 mm Hg produced only transient changes in MAP and no increase in lactate level. A moderate hemorrhage (10 mL/kg) limited the safe abdominal pressure to 10 mm Hg with metabolic changes that were restored 15 minutes after desufflation. Higher PP pressure (15 mm Hg) at this hemorrhage level produced a significant decline in MAP (42%, p < 0.001) and progressive metabolic acidosis with a 2.1-fold increase (p < 0.01) in lactate level. The more severe hemorrhage (15 mL/kg) further reduced the limits of PP pressure such that 10 and 15 mm Hg resulted in a progressive decline of blood pressures (52% and 54%, respectively; p < 0.001) and severe metabolic acidosis as manifested by 3.3- and 3.1-fold rises in lactate levels, respectively. In the most severe hemorrhaged animals (17.5 mL/kg), the 50% mortality was primarily determined by the severity of the blood loss and the additional PP at 5 mm Hg had no significant impact.

CONCLUSION

The safe limit of PP pressurization with CO2 is dependent on the amount of blood loss. In this mechanically ventilated rat model, increasing the amount of blood loss from 0 to 15 mL/kg reduces the tolerable level of abdominal insufflation pressure from 15 mm Hg to 5 mm Hg. A 5-mm Hg PP pressure appears safe even in the most severely hemorrhaged animals.

Effect of increased intraabdominal pressure on cardiac output and tissue blood flow assessed by color-labeled microspheres in the pig

BACKGROUND

Studies of the hemodynamic effects associated with the pneumoperitoneum have had controversial results. We set out to investigate the effect of increased intraabdominal pressure (IAP) on cardiac output and tissue blood flow in various intraabdominal and extraabdominal organs using the color-labeled microsphere (CLM) technique.

METHODS

IAP was induced by CO2 insufflation in anesthetized pigs; 0, 5, and 10 mmHg was used in the low-pressure group and 0, 15, and 24 mmHg in the high-pressure group. Tissue blood flow (ml.min-1.g-1) and cardiac output (CO) (ml/min) were determined by the CLM technique.

RESULTS

CO decreased at IAP > or = 15 mmHg. Arterial PaCO2 and hydrogen ion concentration increased in response to all levels of IAP. Arterial PaO2, oxygen saturation, and bicarbonate ion concentration remained unchanged. Low IAP did not influence tissue blood flows in most of the organs. However, in the spleen, pancreas, esophagus, and gastric mucosal specimens, tissue blood flow was significantly decreased at 24 mmHg.

CONCLUSION

The level of IAP used in current practice (10-12 mmHg) appears to be safe with regard to hemodynamic variables and tissues blood flow; however, higher levels may induce a decrease in cardiac output and tissue blood flow.

Cancer and laparoscopy, experimental studies: a review

OBJECTIVE

To review the experimental studies on laparoscopy and cancer and to propose guidelines for the clinical management of gynecologic cancer.

METHODS

The literature in MEDLINE was searched from January 1992 to December 1998 using the terms 'cancer', 'laparoscopy' and 'experimental or animal study'. Cross-referencing identified additional publications. Abstracts and letters to the editor were excluded. All the relevant papers were reviewed.

RESULTS

Depending on the model used, controversial results have been reported on the incidence of trocar site metastasis when comparing CO(2) laparoscopy and laparotomy. In contrast, the following conclusions can be proposed: (i) tumour growth after laparotomy is greater than after endoscopy; (ii) tumour dissemination is worse after CO(2) laparoscopy than after laparotomy; (iii) some of the disadvantages of CO(2) laparoscopy may be treated using local or intravenous treatments or avoided using other endoscopic exposure methods, such as gasless laparoscopy.

CONCLUSIONS

The laparoscopic treatment of gynecologic cancer has potential advantages and disadvantages, and may only be performed in prospective clinical trials. The risk of dissemination appears high when a large number of malignant cells are present. Adnexal tumours with external vegetations, and bulky lymph nodes should be considered as contra-indications to CO(2) laparoscopy.

Pneumoperitoneum does not potentiate the nephrotoxicity of aminoglycosides in rats

OBJECTIVES

Pneumoperitoneum is associated with transient renal dysfunction. To our knowledge, the safety of administering nephrotoxins such as aminoglycosides during pneumoperitoneum has not been studied. Our hypothesis was that pneumoperitoneum potentiates the nephrotoxicity of aminoglycosides.

METHODS

From 29 rats we obtained preprocedure 24-hour urine collections. In the pneumoperitoneum group (n = 7), carbon dioxide was insufflated intra-abdominally at 15 mm Hg pressure for 2 hours. In the gentamicin group (n = 7), 10 mg/kg gentamicin was administered intravenously. In the combined pneumoperitoneum/gentamicin group (n = 8), the same dose of gentamicin was administered 10 minutes before pneumoperitoneum. Sham rats (n = 7) received anesthesia only. Urine was collected for the 24 hours after the procedure, and 1 week later blood for creatinine determination and final 24-hour urine collections were obtained. All urine samples were assayed for creatinine and N-acetyl-beta-glucosaminidase (NAG).

RESULTS

Only the gentamicin and combined pneumoperitoneum/gentamicin groups presented day 1 values for NAG excretion that were significantly greater than same day sham or paired preprocedure values; the rest of the urinary creatinine and NAG day 1 levels and all the day 7 levels were not significantly different from same day sham or paired preprocedure levels. Day 7 serum creatinine and creatinine clearance did not differ significantly among the groups.

CONCLUSIONS

We found that intravenous gentamicin transiently increased urinary excretion of NAG in rats, which resolved within 1 week. Pneumoperitoneum for 2 hours at 15 mm Hg did not increase urinary NAG, either alone or in gentamicin-treated rats. Moreover, our data are sufficient to refute with 95% certainty the possibility that gentamicin plus pneumoperitoneum decreases creatinine clearance more than approximately 60%. These results do not support the hypothesis that pneumoperitoneum potentiates the nephrotoxicity of aminoglycosides.