The effects of preperitoneal carbon dioxide insufflation on cardiopulmonary function in pigs.
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BACKGROUND AND OBJECTIVES: Although considerable experimental and clinical knowledge exists on the physiology of pneumoperitoneum, insufflation of the preperitoneal space has not been extensively studied. The purpose of this study is to evaluate the physiology associated with preperitoneal carbon dioxide (CO2) insufflation in a porcine model. METHODS: Eleven pigs weighing 35 to 45 kg were anesthetized and placed on mechanical ventilation. A pulmonary artery catheter and an arterial line were inserted. Balloon dissection of the preperitoneal space and insufflation to 10 mm Hg for 1.5 hours, followed by an increase to 15 mm Hg for an additional 1.5 hours, was performed. Hemodynamic and arterial blood gas values were determined every 15 minutes throughout the stabilization and three-hour insufflation period. Hemodynamic parameters and blood gas values were analyzed using one-way analysis of variance with respect to insufflation time and pressure. RESULTS: Analysis of hemodynamics (CO, CVP, PAD, PAS, PCWP) did not demonstrate statistical significance with respect to time. However, there was a statistical difference in CO (p=.01), CVP (p<.01), and PCWP (p=.034) when comparing a pressure of 15 mm Hg to a pressure of 10 or 0 mm Hg. The other parameters did not demonstrate significant differences among the three pressure groups. Arterial PCO2 and pH were highly significant with respect to time (p<.01 and P<.01, respectively) and among the pressure groups (p<.01 and P<.01, respectively). CONCLUSIONS: Insufflation of the preperitoneal space with CO2 gas does not cause significant alterations in hemodynamics and blood gas changes at a pressure of 10 mm Hg. However, when a pressure of 15 mm Hg is used to insufflate this space, there is evidence of decreased pH and cardiac output, with elevated CVP and CO2 retention. This correlates with greater pneumodissection of the gas within the layers of the abdominal wall when elevated pressures are used. (+info)
The mouse as a model to study adhesion formation following endoscopic surgery: a preliminary report.
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Our aim was to investigate the feasibility of a mouse model to study adhesion formation following endoscopic surgery. Following preliminary studies to establish anaesthesia and pneumoperitoneum pressure, a prospective randomized study was carried out to investigate the effect of CO2 pneumoperitoneum on postoperative adhesions. In group I (control group), the duration of pneumoperitoneum was shorter than 5 min. In groups II, III and IV, pneumoperitoneum was maintained for 60 min without flow, with a continuous low flow (1 ml/min) and a continuous high flow (10 ml/min) through the abdominal cavities of the mice using non-humidified CO2, respectively. Adhesions were scored after 7 days by laparotomy. The total adhesion scores were 0.9 +/- 0.8 (n = 15) in control group, 2.4 +/- 0.8 (n = 15) (P < 0.001 versus control group) in group II with no flow, 2.6 +/- 1.3 (n = 15) (P < 0.001 versus control group) in group III with a continuous low flow and 4.3 +/- 0.9 (n = 15) (P < 0.001 versus control group and P < 0.001 versus group II and III) in group IV with a continuous high flow. In conclusion, the mouse can be used as a model to study adhesion formation following endoscopic surgery. Duration of CO2 pneumoperitoneum is a co-factor in adhesion formation. (+info)
Carbon dioxide embolism during laparoscopy: effect of insufflation pressure in pigs.
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Carbon dioxide embolism is a rare but potentially devastating complication of laparoscopy. To determine the effects of insufflation pressure on the mortality from carbon dioxide embolism, six swine had intravascular insufflation with carbon dioxide for 30 seconds using a Karl Storz insufflator at a flow rate of 35 mL/kg/min. The initial insufflation pressure was 15 mm Hg. Following recovery from the first embolism, intravascular insufflation using a pressure of 20 mm Hg at the same flow rate was performed in the surviving animals. Significantly less carbon dioxide (8.3 +/- 2.7 versus 16.7 +/- 3.9 mL/kg; p < 0.02) was insufflated intravascularly at 15 mm Hg than at 20 mm Hg pressure. All of the pigs insufflated at 15 mm Hg pressure with a flow rate of 35 mL/kg/min survived. In contrast, 4 of the 5 pigs insufflated at 20 mm Hg pressure died. The surviving pig died when insufflated with 25 mm Hg pressure following an embolism of 15.7 mL/kg. Intravascular injection was often associated with an initial rise in end-tidal carbon dioxide tension, followed by a rapid fall in all cases where the embolism proved fatal. Insufflation should be begun with a low pressure and a slow flow rate to limit the volume of gas embolized in the event of inadvertent venous cannulation. Insufflation should immediately be stopped if a sudden change in end-tidal carbon dioxide tension occurs. (+info)
On the discrepancy between whole-cell and membrane patch mechanosensitivity in Xenopus oocytes.
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1. Mechanical stimulation of voltage-clamped Xenopus oocytes by inflation, aspiration, or local indentation failed to activate an increase in membrane conductance up to the point of causing visible oocyte damage. 2. The absence of mechanosensitivity is not due to the vitelline membrane, rapid MG channel adaptation or tension-sensitive recruitment of new membrane. 3. Membrane capacitance measurements indicate that the oocyte surface area is at least 5 times larger than that predicted assuming a smooth sphere. We propose that this excess membrane area provides an immediate reserve that can 'buffer' membrane tension changes and thus prevent MG channel activation. 4. High-resolution images of tightly sealed patches and patch capacitance measurements indicate a smooth membrane that is pulled flat and perpendicular across the inside of the pipette. Brief steps of pressure or suction cause rapid and reversible membrane flexing and MG channel activation. 5. We propose that changes in membrane geometry induced during cell growth and differentiation or as a consequence of specific physiological and pathological conditions may alter mechanosensitivity of a cell independently of the intrinsic properties of channel proteins. (+info)
The accuracy of gastric insufflation in testing for gastroesophageal perforations during laparoscopic Nissen fundoplication.
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BACKGROUND: Laparoscopic Nissen fundoplication is an effective technique for the symptomatic relief of the manifestations of gastroesophageal reflux disorder but is associated with a 0.8-1% rate of gastroesophageal perforation. Early detection and repair of these injuries is critical to patient outcome, but occult injuries occur and may be missed. Gastric insufflation technique evaluates the integrity of the gastroesophageal wall after laparoscopic Nissen fundoplication. Gastric insufflation technique involves occlusion of the proximal stomach with a noncrushing bowel clamp while insufflating the submerged gastroesophageal junction. We conducted an animal study to assess the utility of gastric insufflation technique. METHODS: Five pigs (mean weight, 40.4 kg) underwent testing of laparoscopic gastric insufflation technique. In four animals, laparoscopic Nissen fundoplication was performed and then gastroesophageal junction injuries were created (3-5 mm distraction-type wall injuries). Non-crushing bowel clamps provided occlusion of the pylorus and then the proximal stomach during gastroesophageal insufflation. The gastroesophageal junction was then submerged. In the fifth animal, gastric insufflation technique was repeated while calibrated injuries were created to determine the smallest detectable injury. An injury was considered detectable if rising air bubbles were noted from the submerged gastroesophageal structures. Maximal luminal pressures needed to detect injuries were recorded with an in-line manometer. RESULTS: In all animals, 5-7 mm injuries of the gastroesophageal junction were easily detected using gastric insufflation technique when the proximal stomach was occluded. When the pylorus alone was occluded, detection of gastroesophageal injuries was inconsistent. Small injuries (<3 mm) of the esophagus were difficult to visualize with pyloric occlusion alone but were consistently detectable with proximal stomach occlusion at pressures less than 20 mm Hg. When the pylorus alone was occluded, the smallest detectable stomach perforation was a 16-gauge needle puncture while applying maximal gastric pressure (40-60 mm Hg) and a 2.5 mm linear injury when generating lower pressures (20 mm Hg). CONCLUSION: Proximal stomach occlusion and insufflation appears to effectively detect esophageal injuries of likely clinical importance (>2.5 mm). Pyloric occlusion and insufflation reliably evaluates the anterior stomach for injury. Gastric insufflation technique is a useful method for detecting gastroesophageal injury after laparoscopic Nissen fundoplication. (+info)
Transoesophageal echocardiographic assessment of haemodynamic changes during laparoscopic herniorrhaphy in small children.
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Laparoscopic techniques for surgery are gradually becoming established in paediatric surgery. Technical aspects, such as the maximum safe gas insufflation pressure, are still open to discussion. We used transoesophageal echocardiography to study the haemodynamic changes in eight small children undergoing laparoscopic herniorrhaphy, with two different levels of intra-abdominal pressure (IAP), 6 and 12 mm Hg. End-tidal carbon dioxide tension was maintained constant at 4.3-4.7 kPa. After baseline measurements, an IAP of 12 mm Hg was applied for 10 min. Next, IAP was decreased to 6 mm Hg, followed by a second period of 12 mm Hg. Haemodynamic measurements were obtained at each stage. A further measurement was obtained 10 min after abdominal deflation at the end of surgery while anaesthesia was unchanged. Cardiac index (CI) decreased significantly only after the first 12 mm Hg level of IAP. The subsequent decrease in IAP to 6 mm Hg caused return of CI to baseline levels. The second increase in IAP did not cause any reduction in CI. The initial reduction in CI, although statistically significant, did not appear to be clinically important. We conclude that an IAP of up to 12 mm Hg appeared to be safe in healthy small children undergoing laparoscopic herniorrhaphy. (+info)
Nasal toxicity of cocaine: a hypercoagulable effect?
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Nasal insufflation of cocaine injures the nasal mucosa and can perforate the septum. Cocaine-induced vasoconstriction resulting in ischemia is one of the methods that may be responsible for this damage. We are determining whether cocaine also produces a hypercoagulable state that may compound factors which have been previously established to cause damage to the nasal mucosa and septum. This study uses Modified Recalcification Time (MRT), a test developed in our laboratory that has the ability to measure the overall coagulation process. Our study revealed no connection between cocaine and enhanced platelet function or monocyte-released tissue factor. The coagulation process was unaffected by the addition of the drug, so we conclude that cocaine does not cause a hypercoagulable state and cannot assist in the explanation regarding the ischemic changes of the nasal septum. (+info)
The LMA 'ProSeal'--a laryngeal mask with an oesophageal vent.
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We describe a new laryngeal mask airway (LMA) that incorporates a second tube placed lateral to the airway tube and ending at the tip of the mask. The second tube is intended to separate the alimentary and respiratory tracts. It should permit access to or escape of fluids from the stomach and reduce the risks of gastric insufflation and pulmonary aspiration. It can also determine the correct positioning of the mask. A second posterior cuff is fitted to improve the seal. A preliminary crossover comparison with the standard mask in 30 adult female patients showed no differences in insertion, trauma or quality of airway. At 60 cm H2O intracuff pressure, the new LMA gave twice the seal pressure of the standard device (P < 0.0001) and permitted blind insertion of a gastric tube in all cases. It is concluded that the new device merits further study. (+info)