Prospective, randomized, clinical trial on the effects of laparoscopic insufflation pressures on portal pressures in dogs.

OBJECTIVE: The adverse effects of intra-abdominal pressure from capnoperitoneum on cardiovascular and pulmonary systems have been well documented, but the effects on portal pressures in dogs with various insufflation pressures is poorly defined. The aim of the present study was to measure the effect of a range of insufflation pressures on the portal pressure, using direct pressure measurements in patients undergoing laparoscopy. STUDY DESIGN: Clinical randomized prospective study. ANIMALS: Nine client-owned dogs undergoing routine laparoscopy. METHODS: Two rounds of direct portal pressure assessments were performed, at insufflation pressures of 0, 6, 10, and 14 mmHg in a predetermined randomized sequence. The data were analyzed for effects of insufflation pressure, hemodynamic alterations, and round. A best-fit exponential model of the relationship between portal pressure and insufflation pressure was created. RESULTS: Portal pressure increased by 38% at 6 mmHg, 95% at 10 mmHg, and 175% at 14 mmHg compared to baseline. Portal pressure increased at an average rate of 7.45% per mmHg of insufflation pressure. Effects of weight, weight/insufflation pressure interaction, and round of insufflation were not statistically significant. No systemic hemodynamic adverse events were observed. CONCLUSION: Portal pressure increased as insufflation pressure increased. There was no clinically significant difference in baseline portal pressure between rounds of insufflation. CLINICAL SIGNIFICANCE: This exponential model of portal pressure supports the use of the minimum insufflation pressure to allow visualization during laparoscopy. The return of portal pressure to baseline following desufflation supports the comparison of portal pressure measurements before and after laparoscopic shunt attenuation.

Assessment of laparoscopic working space in guinea pigs (Cavia porcellus) undergoing carbon dioxide insufflation at different intra-abdominal pressures.

OBJECTIVE: To evaluate pneumoperitoneal volumes (laparoscopic working space) in guinea pigs (Cavia porcellus) undergoing pneumoperitoneum via carbon dioxide insufflation at different intra-abdominal pressures (IAPs) (4, 6, and 8 mm Hg) and recumbencies (dorsal, right lateral, and left lateral). ANIMALS: Six 3- to 4-month-old sexually intact female Hartley guinea pigs. PROCEDURES: Guinea pigs were anesthetized, intubated, and had an abdominal insufflation catheter placed. A baseline abdominal CT scan was performed. Guinea pigs underwent insufflation, with each IAP given in a random order for 10 to 15 minutes with a washout period of 5 minutes between pressures. Abdominal CT scans were acquired at each IAP and at each recumbency. Pneumoperitoneal volumes were calculated using software. RESULTS: Increases in IAP increased working space significantly (P < .001). The 6- and 8-mm Hg pressures increased working space from 4 mm Hg by 7.3% and 19.8%, respectively. Recumbent positioning (P = .60) and body weight (P = .73) did not affect working space. Order of IAP had a significant (P = .006) effect on working space. One of the guinea pigs experienced oxygen desaturation and bradycardia at 6- and 8-mm Hg IAP. CLINICAL RELEVANCE: Although an increased working space occurred at 6 and 8 mm Hg compared to 4 mm Hg, further research is needed concerning the cardiovascular effects of pneumoperitoneum in guinea pigs to determine whether those higher IAPs are safe in this species. An IAP of 6 mm Hg can be considered for laparoscopic cannula placement, followed by a lower IAP for laparoscopic procedures.

Evaluation of the effects of medial saphenous venous pressures as an indirect method of measurement of intra-abdominal pressures in the horse.

OBJECTIVE: To evaluate the effect of changes in intra-abdominal pressure (IAP) on medial saphenous venous pressure (MSVP) and hemodynamics in normal horses. DESIGN: Experimental, in-vivo study. SETTING: University Teaching Hospital. ANIMALS: Convenience sample of 7 mixed breed horses; 5 geldings, and 2 mares. INTERVENTIONS: Pneumoperitoneum was induced in horses under standing sedation with carbon dioxide gas using a laparoscopic insufflator for a total of 60 minutes to simulate clinical elevation in IAP. Pressure was increased stepwise to 20 mm Hg over 30 minutes, and maintained at that pressure for 30 minutes to evaluate the effect of sustained intra-abdominal hypertension. The MSVP and vital parameters were recorded, along with direct arterial blood pressure from the transverse facial artery. MEASUREMENTS AND MAIN RESULTS: As IAP increased, MSVP increased in a stepwise manner, in concert with changes in IAP. The consistency in measurement between MSVP and IAP was high (intraclass correlation coefficient = 0.92; P < 0.001) and repeated measures correlation was excellent (r = 0.98; P < 0.001). Heart rate was unchanged over the course of the experiment (P = 0.09), however, respiratory rate increased with increasing IAP (P < 0.001). Arterial blood pressure also increased with insufflation (P < 0.001), with a significant difference at an IAP of 15 mm Hg (P = 0.04). CONCLUSIONS: This report provides preliminary data demonstrating a strong correlation between equine MSVP and changes in IAP, similar to that observed in other species. Further investigations are needed to evaluate this relationship, and to confirm these results in clinical patients.

Evaluation of the effects of intraabdominal hypertension on equine central venous pressure.

OBJECTIVE: To evaluate the effect of changes in intraabdominal pressure (IAP) on central venous pressure (CVP) in normal horses. DESIGN: Experimental, in vivo study. SETTING: University Teaching Hospital. ANIMALS: Convenience sample of 7 mixed breed horses-5 geldings and 2 mares. INTERVENTIONS: Pneumoperitoneum was induced in horses under standing sedation with carbon dioxide gas using a laparoscopic insufflator for a total of 60 minutes to simulate clinical elevation in IAP. Pressure was increased stepwise to 20 mm Hg over 30 minutes, and maintained at that pressure for 30 minutes to evaluate the effect of sustained intraabdominal hypertension. CVP was obtained from the cranial vena cava, concurrent with pressure obtained from the peritoneal cavity. MEASUREMENTS AND MAIN RESULTS: CVP increased as IAP increased up to 12 mm Hg, and declined as IAP increased further. The changes in CVP over time were significantly different (P < 0.03). Repeated measures correlation was positive, and highest, for mean CVP as IAP increased from 0 to 12 mm Hg (r = .70; 95% CI, .43-.85; P < 0.0001). Correlation of mean CVP with insufflation pressure became negative as IAP increased further from 15 to 20 mm Hg (r = -.47; 95% CI, -.66 to -.21; P = 0.0006). CONCLUSIONS: This report provides preliminary data demonstrating a biphasic trend in equine CVP caused by changes in IAP, similar to that observed in other species. Further investigations are needed to evaluate this trend and to confirm these results in clinical patients.

Effect of pneumoperitoneum with warmed humidified or standard-temperature carbon dioxide during laparoscopy on core body temperature, cardiorespiratory and thromboelastography variables, systemic inflammation, peritoneal response, and signs of postoperative pain in healthy mature dogs.

OBJECTIVE To evaluate effects of pneumoperitoneum created with warmed humidified CO2 (WHCO2) during laparoscopy on core body temperature, cardiorespiratory and thromboelastography variables, systemic inflammation, peritoneal response, and signs of postoperative pain in healthy mature dogs. ANIMALS 6 mature purpose-bred dogs. PROCEDURES In a randomized crossover study, each dog was anesthetized twice, and pneumoperitoneum was created with standard-temperature CO2 (STCO2; 22°C and 0% relative humidity) and WHCO2 (37°C and 98% relative humidity). Data were collected during each procedure, including core body temperature, cardiorespiratory and thromboelastography variables, and inflammatory biomarkers. Peritoneal biopsy specimens were collected and evaluated with scanning electron microscopy. Dogs were assessed for signs of postoperative pain. RESULTS Mean core body temperature was significantly lower (35.2°C; 95% confidence interval, 34.5° to 35.8°C) with WHCO2 than with STCO2 (35.9°C; 95% confidence interval, 35.3° to 36.6°C) across all time points. Cardiac index increased during the procedure for both treatments but was not significantly different between treatments. Thromboelastography variables did not differ significantly between treatments as indicated by the coagulation index. Subjective evaluation of peritoneal biopsy specimens revealed mesothelial cell loss with STCO2. There was no significant difference in circulating C-reactive protein or interleukin-6 concentrations. There was a significant increase in the number of postoperative pain scores > 0 for the WHCO2 treatment versus the STCO2 treatment. CONCLUSIONS AND CLINICAL RELEVANCE Analysis of these data suggested that effects on evaluated variables attributable to the use of WHCO2 for creating pneumoperitoneum in healthy mature dogs undergoing laparoscopy did not differ from effects for the use of STCO2.

An alveolar recruitment maneuver followed by positive end-expiratory pressure improves lung function in healthy dogs undergoing laparoscopy.

OBJECTIVE: To evaluate the effects of an alveolar recruitment maneuver (ARM) followed by 5 cmH2O positive end-expiratory pressure (PEEP) in dogs undergoing laparoscopy. STUDY DESIGN: Prospective, randomized clinical study. ANIMALS: A group of 20 dogs undergoing laparoscopic ovariectomy. METHODS: Dogs were sedated with acepromazine and methadone intramuscularly; anesthesia was induced with propofol intravenously and maintained with inhaled isoflurane. The following baseline ventilatory setting (BVS) was administered: tidal volume of 12 mL kg-1, inspiratory to expiratory ratio of 1:2, inspiratory pause 25% of inspiratory time, no PEEP and a respiratory rate to maintain end-tidal carbon dioxide tension between 5.3 and 7.3 kPa. Then, 10 minutes after the pneumoperitoneum, 10 dogs (RM) underwent a sustained inflation ARM followed by BVS plus 5 cmH2O PEEP, while 10 dogs (NO-RM) were left with BVS throughout the procedure. Gas exchange and respiratory system mechanics were evaluated before the pneumoperitoneum (PPpre), before ARM (PP10), 30 minutes later (PP30) and 20 minutes after pneumoperitoneum discontinuation (PPpost20). Data were analyzed using anova (p < 0.05). RESULTS: The Fshunt at PP30 and PPpost20 was lower (p < 0.001) in the RM (2.3 ± 2.2 and 4.7 ± 3.7%) than in the NO-RM (5.2 ± 2.1 and 11.1 ± 5.2%), and PaO2 at PP30 and PPpost20 was higher (p < 0.001) in the RM (67.3 ± 4.2 and 60.1 ± 9.4 kPa) than in the NO-RM (50.2 ± 7.4 and 45.5 ± 11.1 kPa). Static compliance of the respiratory system at PP30 and PPpost20 was greater (p < 0.001) in the RM (2.4 ± 0.2 and 2.1 ± 0.4 mL cmH2O-1 kg-1) than in the NO-RM (0.9 ± 0.4 and 1.2 ± 0.2 mL cmH2O-1 kg-1). CONCLUSIONS AND CLINICAL RELEVANCE: In dogs undergoing laparoscopy, ARM followed by 5 cmH2O PEEP improves gas exchange and respiratory system mechanics.

In vitro evaluation of a simulated pneumoperitoneum environment using carbon dioxide on canine transitional cell carcinoma.

OBJECTIVE: To assess the impact of a simulated CO2 pneumoperitoneum environment on the viability and proliferation of canine transitional cell carcinoma (TCC) cells in vitro. STUDY DESIGN: In vitro study. METHODS: A control Madin-Darby canine kidney (MDCK) cell line and 3 canine TCC cell lines were exposed to 100% CO2 at pressure of 0, 5, 10, or 15 mmHg for 2 hours by using an airtight chamber and a mechanical insufflator at 37°C. Culture media pH was measured. Viability and proliferation were assessed by using a resazurin assay and trypan blue dye, respectively. RESULTS: The pH in the media significantly decreased immediately after CO2 exposure but returned to normal within 1 hour. The viability of the cell lines was variably affected at the evaluated pressures. Insufflation pressure of 10 mmHg resulted in significantly decreased cell viability compared with control. The impact of 15 mmHg CO2 was comparable to 0 mmHg and control. CO2 insufflation pressure had no significant effects on proliferation up to 7 days postexposure. Conclusion/Clinical significance: A positive pressure CO2 environment significantly decreased the viability of TCC and MDCK cells under specific conditions without influencing their proliferation up to 7 days postexposure. Investigating these effects in clinical patients undergoing CO2 laparoscopy is essential to assess for port site metastasis or peritoneal carcinomatosis in order to translate these in vitro results to clinical recommendations.

Effects of pneumoperitoneum and of an alveolar recruitment maneuver followed by positive end-expiratory pressure on cardiopulmonary function in sheep anesthetized with isoflurane-fentanyl.

OBJECTIVE: To investigate the effects of pneumoperitoneum alone or combined with an alveolar recruitment maneuver (ARM) followed by positive end-expiratory pressure (PEEP) on cardiopulmonary function in sheep. STUDY DESIGN: Prospective, randomized, crossover study. ANIMALS: A total of nine adult sheep (36-52 kg). METHODS: Sheep were administered three treatments (≥10-day intervals) during isoflurane-fentanyl anesthesia and volume-controlled ventilation (tidal volume: 12 mL kg-1) with oxygen: CONTROL (no intervention); PNEUMO (120 minutes of CO2 pneumoperitoneum); PNEUMOARM/PEEP (PNEUMO protocol with an ARM instituted after 60 minutes of pneumoperitoneum). The ARM (5 cmH2O increases in PEEP of 1 minute duration until 20 cmH2O of PEEP) was followed by 10 cmH2O of PEEP until the end of anesthesia. Cardiopulmonary data were recorded until 30 minutes after abdominal deflation. RESULTS: PaO2 was decreased from 435-462 mmHg (58.0-61.6 kPa) (range of mean values in CONTROL) to 377-397 mmHg (50.3-52.9 kPa) in PNEUMO (p < 0.05). Quasistatic compliance (Cqst, mL cmH2O-1 kg-1) was decreased from 0.85-0.92 in CONTROL to 0.52-0.58 in PNEUMO. PaO2 increased from 383-385 mmHg (51.1-51.3 kPa) in PNEUMO to 429-444 mmHg (57.2-59.2 kPa) in PNEUMOARM/PEEP (p < 0.05) and Cqst increased from 0.52-0.53 in PNEUMO to 0.70-0.74 in PNEUMOARM/PEEP. Abdominal deflation in PNEUMO did not restore PaO2 and Cqst to control values. Cardiac index (L minute-1 m2) decreased from 4.80-4.70 in CONTROL to 3.45-3.74 in PNEUMO and 3.63-3.76 in PNEUMOARM/PEEP. Compared with controls, ARM/PEEP with pneumoperitoneum decreased mean arterial pressure from 81 to 68 mmHg and increased mean pulmonary artery pressure from 10 to 16 mmHg. CONCLUSIONS AND CLINICAL RELEVANCE: Abdominal deflation did not reverse the pulmonary function impairment associated with pneumoperitoneum. The ARM/PEEP improved respiratory compliance and reversed the oxygenation impairment induced by pneumoperitoneum with acceptable hemodynamic changes in healthy sheep.

Influence of Trendelenburg position and pneumoperitoneum treatment on gastroesophageal reflux in dogs.

Gastroesophageal reflux is a latent factor that may cause esophagitis, esophageal stenosis, and aspiration pneumonia through the regurgitation of the gastric fluid contents. For laparoscopic surgery, posture-changing and pneumoperitoneum operations are conducted to develop the visual field. However, few studies have examined the influence of these operations on gastroesophageal reflux. In this experiment using 10 Beagles, 10 mL of contrast medium was administered into the stomach, and the dogs were placed in the Trendelenburg position with 10-degree tilting. Pneumoperitoneum treatment with carbon dioxide was performed, with an intraperitoneal pressure of 10 mmHg. The presence or absence of gastroesophageal reflux was evaluated using computed tomography (CT). In horizontal and Trendelenburg positions, there was no reflux of Contrast medium. However, reflux was observed in the Trendelenburg position under pneumoperitoneum (p<0.05). These results suggest that the risk of gastroesophageal reflux increases during laparoscopic surgery in the Trendelenburg position with 10-degree tilting under an intraperitoneal pressure of 10 mmHg.

Effect of changes in intra-abdominal pressure on diameter, cross-sectional area, and distensibility of the lower esophageal sphincter of healthy dogs as determined by use of an endoscopic functional luminal imaging probe.

OBJECTIVE To evaluate the effect of intra-abdominal pressure (IAP) on morphology and compliance of the lower esophageal sphincter (LES) by use of impedance planimetry in healthy dogs and to quantify the effect of changes in IAP. ANIMALS 7 healthy, purpose-bred sexually intact male hound-cross dogs. PROCEDURES Dogs were anesthetized, and cross-sectional area (CSA), minimal diameter (MD), LES length, LES volume, and distensibility index (DI) of the LES were evaluated by use of an endoscopic functional luminal imaging probe. For each dog, measurements were obtained before (baseline) and after creation of a pneumoperitoneum at an IAP of 4, 8, and 15 mm Hg. Order of the IAPs was determined by use of a randomization software program. RESULTS CSA and MD at 4 and 8 mm Hg were not significantly different from baseline measurements; however, CSA and MD at 15 mm Hg were both significantly greater than baseline measurements. The LES length and LES volume did not differ significantly from baseline measurements at any IAP. The DI differed inconsistently from the baseline measurement but was not substantially affected by IAP. CONCLUSIONS AND CLINICAL RELEVANCE Pneumoperitoneum created with an IAP of 4 or 8 mm Hg did not significantly alter LES morphology in healthy dogs. Pneumoperitoneum at an IAP of 15 mm Hg caused a significant increase in CSA and MD of the LES. Compliance of the LES as measured by the DI was not greatly altered by pneumoperitoneum at an IAP of up to 15 mm Hg.

Results of hepatic and renal function tests to different CO2 pneumoperitoneum conditions: An experimental capnoperitoneum study in dogs.

Carbon dioxide (CO2) is the most commonly used insufflation gas to provide exposure in the abdominal cavity during laparoscopic surgery. This study investigated the results of hepatic and renal function tests after different capnoperitoneum intraabdominal pressures in dogs. Twenty-four beagle dogs (12 males and 12 females) were used (n = 6 dogs). The intraabdominal pressure was maintained for 60 minutes, and urinalysis, hepatic and renal function tests were carried out at designed times. No surgery was performed on any of the dogs during the capnoperitoneum. In this study, whether low or high pressure, significant increases of gamma-glutamyltransferase, alkaline phosphatase, aspartate aminotransferase and creatinine levels were observed after pneumoperitoneum. However, our results showed a trend toward higher serum concentrations of some enzymes in dogs at an insufflation pressure of 15 mmHg compared to that of the other groups, although these differences did not reach statistical significance. Therefore, low pressure capnoperitoneum should be considered for dogs with compromised splanchnic function, particularly those undergoing prolonged laparoscopic surgery.

Comparison of Pneumoperitoneum Volumes in Lift Laparoscopy With Variable Lift Locations and Tensile Forces.

OBJECTIVE: Evaluate the effect of peritoneal lift location and tensile force on peritoneal volume. STUDY DESIGN: Complete randomized block design. ANIMALS: Eleven fresh canine cadavers. METHODS: Cadavers underwent abdominal computed tomography (CT) scans after each treatment; 1) no lift, 2) umbilical lift with 15% body weight (BW) tension, 3) umbilical lift with 20% BW, 4) umbilical lift with 25% BW, 5) caudal lift with 15% BW, and 6) both umbilical and caudal lift with 15% BW shared equally between devices (dual lift). Isobaric pneumoperitoneal volume, instrument working distances, and transverse measures were calculated and normalized for each dog and compared across treatments. RESULTS: Increasing tensile force created a correspondingly larger pneumoperitoneal volume for the umbilical lift (0.34-0.40 total abdominal volume). Dual lifting created a larger pneumoperitoneal volume than either location alone at the same tension (0.39 total abdominal volume). Increasing lift tensions increased working distances, except to caudal abdominal structures. Increasing lift tensions at the umbilical location reduced the transverse diameter of the abdomen at the level of the kidney (0.92-0.86 total abdominal volume) and increased the transverse diameter at the midperitoneum (1.0-1.05 total abdominal volume). CONCLUSIONS: Larger isobaric penumoperitoneal volumes are produced with increased tensile force, or with dual lifting at lower force. A caudal lift leads to a small pneumoperitoneal volume but equivalent working space to caudal abdominal structures. Using an umbilical lift with moderate tensile force is preferable, providing good visualization and working space. Caudal lifting may be utilized to access caudal abdominal structures.

Influence of pneumoperitoneum and postural change on the cardiovascular and respiratory systems in dogs.

We investigated the influence of pneumoperitoneum#(PP) and postural change under inhalation anesthesia with isoflurane, which is routinely used in dogs, on the cardiovascular and respiratory systems. As test animals, 6 adult beagles were used. To induce anesthesia, atropine, butorphanol and propofol were intravenously injected. Anesthesia was maintained with 1.3 MAC (1.7%) isoflurane. The following were the experiment conditions: I:E ratio, 1:1.9; tidal air exchange, 20 ml/kg; and ventilation frequency, 14 times/min. Respiration was regulated so that the PaCO2 was approximately 35 to 40 mmHg before the start of the experiment. PP with CO2 (intraperitoneal pressure 15 mmHg) and a postural change (15°C) was performed during the experiment. As parameters of circulatory kinetics, heart rate (HR), mean aortic pressure (MAP), mean pulmonary arterial pressure (MPAP), central venous pressure (CVP), femoral venous pressure (FVP) and cardiac output (CO) were measured. As parameters of respiratory kinetics, airway pressure (PAW) and blood gas (BG) were measured. There were significant increases in HR, MAP, MPAP, CVP, FVP, CO, PAW and PaCO2 after PP in the horizontal position. There were significant increases in CVP, FVP, PAW and PaCO2 after PP in the Trendelenburg position. There were significant increases in the MPAP, CVP, FVP, PAW and PaCO2 after PP in the inverse Trendelenburg position. There was a significant difference in FVP after PP between the Trendelenburg position and inverse Trendelenburg position. The results of this experiment suggest that appropriate anesthesia control, such as changing the ventilation conditions after PP, is required for laparoscopic surgery under inhalation anesthesia with isoflurane.

Evaluation of total oxidant and antioxidant status in dogs under different CO2 pneumoperitoneum conditions.

BACKGROUND: The induction of the pneumoperitoneum increases intraabdominal pressure (IAP), causing splanchnic ischemia, whereas its deflation normalizes IAP and splanchnic blood flow. We investigated the oxidant-antioxidant status of dogs who underwent low pressure (7 mm Hg), standard pressure (12 mm Hg), and high pressure (15 mm Hg) pneumoperitoneum. RESULTS: Twenty-four beagle dogs (12 males and 12 females), 4-6 years old, weighing 8-11 kg were used. The animals were assigned to one of four groups (n = 6 dogs). Group 1 served as a control; these animals received only anaesthesia for 90 min. In groups 2, 3 and 4, intra-abdominal pressure was increased to 7, 12 and 15 mmHg, respectively, and maintained for 60 min. Total oxidant status (TOS) and total antioxidant status (TAS) were determined in venous blood samples. The percentage ratio of TOS to TAS provided an oxidative stress index (OSI). No significant difference in TOS levels was found among the groups. A significant decrease in TAS levels and an increase in OSI levels were observed at 90 min and 24 h of pneumoperitoneum deflation within group 4. No differences were found among the groups. CONCLUSIONS: A high pressure pneumoperitoneum induced significant changes in TAS and OSI. In addition, TOS and TAS levels are useful markers for evaluating changes in the oxidative status caused by a pneumoperitoneum during laparoscopy. Furthermore, a low-pressure pneumoperitoneum could attenuate oxidative stress induced by CO2 insufflation in dogs.

Effects of pneumoperitoneum induced at various pressures on cardiorespiratory function and working space during laparoscopy in cats.

OBJECTIVE: To evaluate the effect of pneumoperitoneum on cardiorespiratory variables and working space during experimental induction of 3 intra-abdominal pressures (IAPs) in cats. ANIMALS: 6 healthy young adult neutered male domestic shorthair cats. PROCEDURES: All cats were anesthetized through use of a standardized protocol. A catheter was placed in the right femoral artery for blood pressure and blood gas monitoring. A thermodilution catheter was placed in the right jugular vein via fluoroscopic guidance. Cardiopulmonary variables were measured before (baseline) and 2 and 30 minutes after initiation of pneumoperitoneum at IAPs of 4, 8, and 15 mm Hg; these were created through the use of a mechanical insufflator. At each IAP, abdominal dimensions (height, width, and circumference) were measured at a standardized location. RESULTS: At 4 mm Hg and 8 mm Hg IAP, no clinically important changes were identified in cardiorespiratory values. Heart rate, cardiac index, and stroke volume index remained unchanged throughout the study at all IAPs. Mean arterial blood pressure began to increase at 8 mm Hg and was significantly higher, compared with baseline, at both time points at 15 mm Hg. At 15 mm Hg, Paco2 was significantly higher and cats were more acidotic than at baseline. Working space was subjectively greater at 8 mm Hg than at 4 mm Hg IAP; however, at 15 mm Hg, no clinically important enlargement of the working space was identified, compared with at 8 mm Hg. CONCLUSIONS AND CLINICAL RELEVANCE: Values of cardiopulmonary variables were largely unchanged by induction of pneumoperitoneum in healthy cats up to an IAP of 8 mm Hg, and no clinically important increases in working space were evident at an IAP of 15 versus 8 mm Hg. These findings provide little justification for use of IAPs > 8 mm Hg in healthy cats undergoing laparoscopic procedures; however, whether the situation is similar in diseased or elderly cats remains to be determined.

Right intercostal insertion of a Veress needle for laparoscopy in dogs.

OBJECTIVE: To evaluate right intercostal Veress needle (VN) insertion for laparoscopy in dogs. STUDY DESIGN: Longitudinal cohort study. ANIMALS: Female dogs (n = 56). METHODS: The VN was inserted in the last palpable right intercostal space, either 1/3 (Group T; 28 dogs) or mid distance (Group H; 28 dogs) from the xiphoid cartilage to the most caudal extent of the costal arch. Problems encountered during VN insertion and injuries were recorded, graded, and compared between groups, and also between the first and last 20 insertions. RESULTS: Pneumoperitoneum was successfully achieved by VN insertion in 49 (88%) dogs after a single (45 dogs) or 2nd attempt (4 dogs). Frequency of complications was as follows: 20 grade 1 (subcutaneous emphysema, omentum, or falciform injuries); 6 grade 2 (liver or spleen injury), and 1 grade 3 complication (pneumothorax occurred). No significant difference was found between the 2 groups or between the first and last 20 dogs. CONCLUSIONS: Right intercostal VN insertion facilitates pneumoperitoneum in dogs with few consequential complications. No significant difference was found between entry sites; however, the mid distance insertion site in the last palpable intercostal space with dog positioned in dorsal recumbency is likely to result in less complications.

Use of gastric balloon manometry for estimation of intra-abdominal pressure in horses.

REASONS FOR PERFORMING STUDY: Standing laparoscopic procedures, facilitated by abdominal insufflation with carbon dioxide, are being employed to an increasingly greater extent in horses. However, a sustained increase in abdominal pressure may be life-threatening. A practical method for intra-abdominal pressure (IAP) assessment is imperative. Although indirect methods for estimating IAP have been extensively studied in man, little work has been performed in veterinary medicine. OBJECTIVES: To investigate the utility of gastric manometry for purposes of evaluating IAP in horses. METHODS: Gastric pressure (P(ga) ) was estimated by balloon manometry in 8 healthy, mature horses, before and during a 30 min passive pneumoperitoneum induced by right paralumbar puncture. The balloon manometer was positioned within the gastric lumen and inflated using 2 separate volumes of air: 10 and 50 ml. P(ga) Gastric pressure was determined at baseline (0) and 5, 15 and 30 min after induction of passive pneumoperitoneum. Intra-abdominal pressure was measured directly by right paralumbar puncture using an 8 gauge needle at baseline and immediately following establishment of passive pneumoperitoneum. RESULTS: Baseline IAP values were negative and increased (P≤0.05) during development of passive pneumoperitoneum. However, recorded P(ga) measurements for both inflation volumes were positive before (baseline) and during the course of the passive pneumoperitoneum. Measured P(ga) values did not correlate with IAP at any time. CONCLUSIONS AND POTENTIAL RELEVANCE: Our results suggest that the indirect method used in human patients for estimating IAP by P(ga) is not applicable for horses.

Effect of passive pneumoperitoneum on oesophageal pressure, cardiovascular parameters and blood gas analysis in horses.

REASONS FOR PERFORMING STUDY: Standing surgical procedures are being employed to an ever-greater extent in horses. Pneumoperitoneum during abdominal surgery might adversely affect the work of breathing. OBJECTIVES: To determine whether development of pneumoperitoneum during abdominal surgery adversely influences the work of breathing. METHODS: Eight healthy mature horses were equipped with carotid artery and thoracic vena cava catheters and an intraluminal manometry system. The following measurements were obtained before and at +5, +10, +15 and +30 min following establishment of pneumoperitoneum by paralumbar puncture using an 8 gauge needle: vital signs, oesophageal pressure, gastric pressure, arterial and central venous blood pressures, and arterial and mixed venous blood gas analyses. RESULTS: Significant changes in oesophageal pressure, central venous pressure and results of arterial and mixed venous blood gas analysis were not detected. Arterial diastolic and mean pressures and rectal temperature increased slightly (P ≤ 0.05). CONCLUSIONS: Passive pneumoperitoneum did not adversely affect breathing mechanics or haemodynamic variables under experimental conditions. Changes in arterial pressure could have occurred as a response to the passive pneumoperitoneum or be related to handling stress. Subtle variations in rectal temperature were not clinically relevant and likely resulted from stress associated with restraint. POTENTIAL RELEVANCE: It is unlikely that mature horses will develop signs of respiratory difficulty as a result of the development of passive pneumoperitoneum during standing laparoscopy.

Randomized blinded trial comparing the cardiopulmonary effects of NOTES with standard laparoscopy in a porcine survival model.

BACKGROUND: Anecdotal reports of natural orifice translumenal endoscopic surgery (NOTES) procedures in patients are emerging. Whether the new procedure is truly less invasive is not known. We compared perioperative cardiopulmonary parameters during NOTES with standard laparoscopy. METHODS: Twelve swine were randomized to transgastric peritoneoscopy with air or diagnostic laparoscopy with CO(2). Cardiopulmonary parameters were invasively monitored. Animals were survived for 14 days. Data were analyzed by an investigator blinded to the procedure performed. Treatments were contrasted on the mean outcome using a repeated measures linear model. RESULTS: All experiments were successfully completed. No gastric leak or peritonitis resulted. Two hundred and fifty cubic centimeters of saline irrigation was adequate to decrease gastric contamination. Respiratory compromise requiring desufflation resulted in two laparoscopy and one endoscopy animal. Mean arterial oxygen saturation remained at baseline for the NOTES group and decreased by 1.5 +/- 1.5% in the laparoscopic group (p < 0.001). Mean arterial pH dropped significantly lower in the laparoscopy versus the NOTES group (-0.09 +/- 0.06 versus -0.05 +/- 0.05, p = 0.01). Mean systolic blood pressure (Sbp) in both groups remained unchanged from the respective baseline (p = 0.45). Mean diastolic blood pressure (Dbp) showed a mean difference of 19 +/- 1.5 mmHg between the groups (p < 0.001), increasing from baseline for the laparoscopy group and decreasing significantly from baseline in the NOTES group (+2.4 +/- 12.5 versus -6.1 +/- 7.0 mmHg, p < 0.001). Mean heart rate increased significantly from baseline in the laparoscopy group compared to the NOTES group (15.0 +/- 23.4 versus 3.8 +/- 19.0 bpm, p = 0.004). A widening pulse pressure resulted in the NOTES group compared to the laparoscopy group (p < 0.001). The mean bladder pressure was 14.6 +/- 8.0 cmH(2)O in the laparoscopy group compared to 7.1 +/- 7.1 cm H(2)O the NOTES group (p < 0.001). CONCLUSION: Significant differences in measured but not clinically apparent cardiopulmonary parameters were encountered. The difference in insufflation gas, different vagal or catecholamine response may be contributing to these findings.

Evaluación de cambios hemodinámicos y gasométricos producidos por neumoperitoneo experimental con bióxido de carbono y helio en perros / Evaluation of hemodynamic and blood gases changes produced by experimental pneumoperitoneum using carbon dioxide and helium in dogs

La cirugía laparoscópica ha llegado a ser clínicamente relevante. Siempre que se lleva a cabo este tipo de cirugías se tiene que insuflar la cavidad abdominal con dióxido de carbono (CO2). Nosotros evaluamos el uso de CO2 y helio (He) en la producción de neumoperitoneo experimental. Doce perros mestizos fueron sometidos a neumoperitoneo bajo anestesia con halotano al 1 por ciento. Todos los animales se ventilaron mecánicamente con volumen 15 mL/kg, frecuencia respiratoria de 20/min y 100 por ciento de fracción inspirada de O2. Los animales fueron divididos en 2 grupos de estudio. Grupo I: (n = 6) se les produjo neumoperitoneo experimental con CO2 y grupo II: (n = 6) neumoperitoneo experimental con He. El neumoperitoneo se estableció a través de un trocar de 5 mm que se insertó a nivel de la cicatriz umbilical. La presión de insuflación de la cavidad fue de 10 cmH2O durante 30 minutos, 15 cmH2O por 30 minutos y 20 cmH2O también durante 30 minutos. Los parámetros hemodinámicos, gases sanguíneos y la presión inspiratoria máxima fueron evaluados después de la insuflación cada 30 minutos de establecido el neumoperitoneo y 30 minutos después de desinsuflar el abdomen. En los resultados se observó que el gasto cardiaco disminuyó en ambos grupos durante la producción del neumoperitoneo. La presión venosa central (PVC) y la resistencia vascular pulmonar se mantuvo similar en ambos grupos. Las gasometrías del grupo I mostraron incrementó en la pCO2 venosa a los 30 minutos de haberse iniciado el neumoperitoneo, a los 30 mintos de mantener la presión a 20 cmH2O y al finalizar el estudio, mientras que el grupo II no sufrió cambios. La presión inspiratoria máxima (PIM) se incrementó en ambos grupos. Concluimos que no hay diferencia entre la producción del neumoperitoneo con CO2 o He.