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.

Effect of insufflation pressure during transanal minimally invasive surgery on surgical complications with dissection of the rectal submucosa in canine cadavers.

OBJECTIVE: To determine ideal insufflation pressures during transanal minimally invasive surgery (TAMIS) in canine cadavers for rectal submucosal transection and incisional closure. ANIMALS: 16 canine cadavers. PROCEDURES: Cadavers were placed in lateral recumbency. Urinary catheters were placed to measure intra-abdominal pressure (IAP). A single access port was placed to establish a pneumorectum. Cadavers were placed in insufflation groups of 6 mmHg to 8 mmHg (group 1), 10 mmHg to 12 mmHg (group 2), or 14 mmHg to 16 mmHg (group 3). Defects in the rectal submucosa were created and closed with a unidirectional barbed suture. Duration for each procedure and subjective ease of identifying the transection plane and performing incisional closure were assessed. RESULTS: The single access port was successfully placed in dogs weighing 22.7 kg to 48 kg. The ease of each step of the procedure was not influenced by the insufflation pressure. The median surgical duration for group 1 was 740 seconds (range = 564 to 951 seconds), 879 seconds (range = 678 to 991 seconds) for group 2, and 749 seconds (range = 630 to 1,244 seconds) for group 3 (P = .650). The insufflation pressure increased the IAP (P = .007). Perforation of the rectum happened in 2 cadavers in group 3. CLINICAL RELEVANCE: The duration of each step of the procedure was not significantly influenced by insufflation pressure. Defining the dissection plane and performing resection was more challenging in the highest-pressure group. Rectal perforation occurred only with the 14 mmHg to 16 mmHg insufflation pressure. Single access port usage with TAMIS may provide a readily available, minimally invasive approach for the resection of rectal tumors in dogs.

Laparoscopic peritoneopericardial herniorrhaphy in 2 dogs.

Two peritoneopericardial hernias (PPDH) repaired laparoscopically are reported. Both PPDHs were approached with the dog in dorsal recumbency. Herniated organs (gallbladder and 2 liver lobes in Case 1 and omental fat in Case 2) were dissected and reduced. Hernias were closed in a 2-layer horizontal mattress pattern using 2-0 polyester (Case 1), and in a single-layer simple continuous pattern using 0 barbed polyglyconate (Case 2). Reduction and herniorrhaphy were achieved without conversion. Moderate to severe systemic hypotension was observed in both dogs which responded rapidly to reducing abdominal insufflation. Ten- and 7-month follow-up confirmed good clinical outcome in both dogs.

Herniorraphie péritonéo-péricardique laparoscopique chez deux chiens. Deux hernies péritonéopéricardiques (PPDH) réparées par laparoscopie sont rapportées. Les deux PPDHs ont été réalisées avec le chien en décubitus dorsal. Les organes herniés (vésicule biliaire et deux lobes hépatiques dans le cas 1 et graisse épiploïque dans le cas 2) ont été disséqués et réduits. Les hernies ont été fermées avec un patron de suture matelas horizontal à deux couches en utilisant du polyester 2-0 (cas 1) et avec un modèle de suture continu simple à une seule couche en utilisant du polyglyconate barbelé 0 (cas 2). La réduction et l'herniorraphie ont été réalisées sans conversion. Une hypotension systémique modérée à sévère a été observée chez les deux chiens qui ont répondu rapidement à la réduction de l'insufflation abdominale. Un suivi de dix et sept mois a confirmé de bons résultats cliniques chez les deux chiens.(Traduit par Dr Serge Messier).

Effects of combined one-lung ventilation and intrathoracic carbon dioxide insufflation on intrathoracic working space when performing thoracoscopy in dogs.

OBJECTIVE: To evaluate the effects of combining one-lung ventilation and carbon dioxide insufflation (OLV-CDI) on intrathoracic working space (determined by means of CT) during thoracoscopy in dogs and investigate conditions that could safely improve working space compared with OLV alone. ANIMALS: 6 healthy Beagles. PROCEDURES: Dogs were anesthetized, and right- or left-sided (n = 3/side) OLV was instituted. On the blocked side, a laparoscopic trocar sleeve was placed in the ninth intercostal space for CDI. CT was performed under 3 conditions: with OLV alone, with OLV-CDI at an intrapleural pressure (IPP) of 3 mm Hg, and with OLV-CDI at an IPP of 5 mm Hg. Working space volume (WSV), ventilation space volume (VSV), and thoracic cavity volume (TCV) were determined from CT images. RESULTS: With OLV-CDI at an IPP of 3 or 5 mm Hg, WSV and TCV were significantly increased, compared with values obtained during OLV alone. With OLV-CDI at an IPP of 5 mm Hg, VSV and Spo2 were significantly decreased, compared with values obtained during OLV alone. Additionally, contralateral pneumothorax was observed in 4 dogs at an IPP of 5 mm Hg. CLINICAL RELEVANCE: Combining OLV and CDI could provide a larger working space than OLV alone, even with an IPP of 3 mm Hg, in dogs of limited size. However, an evaluation of the effects on oxygenation and cardiovascular variables is needed before clinical use.

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.

Effect of pneumoperitoneum on gastrointestinal motility, pain behaviors, and stress biomarkers in guinea pigs (Cavia porcellus).

OBJECTIVE: To compare stress markers, gastrointestinal motility, and behavioral indicators of pain between guinea pigs undergoing pneumoperitoneum with carbon dioxide (CO2) and control guinea pigs. ANIMALS: Fourteen 4- to 5-month-old intact female Hartley guinea pigs. PROCEDURES: Guinea pigs were randomized to receive insufflation or serve as controls (anesthesia and abdominal catheter placement without insufflation), with 7 animals/group. Insufflated animals underwent 6 mm Hg of CO2 pneumoperitoneum for 30 minutes. Afterward, results for vital signs, blood glucose, fecal cortisol, appetite, fecal output, and behaviors (via video recording) were compared between the 2 groups. RESULTS: There was no difference between groups and over time for body temperature, heart rate, fecal output in grams, pellets consumed, blood glucose, and fecal cortisol. Guinea pigs that underwent insufflation had significantly more fecal pellets at 36 hours after the procedure. Several behaviors were expressed similarly between groups and over time, such as body turns, incomplete movement, rearing, lying down, drinking, and hiding. Coprophagy occurred less often in the insufflated versus noninsufflated group at 12 h postprocedure but was similar between groups at other time points. At 60 hours after the procedure, insufflated animals spent less time squinting compared to noninsufflated animals. Other behaviors were differentially expressed over time but not between treatments. CLINICAL RELEVANCE: Overall, there were no major differences in appetite, stress markers, and behaviors between insufflated and control guinea pigs. CO2 insufflation did not appear to cause undue pain or stress in guinea pigs and may be a reasonable technique to use during laparoscopy.

Animal Model of Video-Assisted Cecum and Ileum Instrumentation for Equine Visceral Pain Study.

This study aimed to describe an animal model for studying equine visceral pain using minimally invasive and video-assisted cecum and ileum instrumentation. The access to the cecum and ileum was affected because of a previous typhlostomy. For video-assisted distention of the cecum and ileum, a distention device, which we developed using an endotracheal Rusch probe, was used, adapted, and coupled to a cuffometer to inflate and measure the pressure of the cuff attached to its distal portion. In a video-assisted manner, the distal portion of the device was introduced into the cecum and ileum, which contained the cuff in its distal portion, properly positioning it in the lumen. The cuff of the distension device was insufflated after the measurement of baseline physiological parameters of the animals and video-assisted confirmation of its right placement in the cecum and ileum lumen (M0). Was performed in one moment through two simultaneous cuff compressions and 1 minute of animal observation to evaluate the degree of abdominal discomfort manifestations (M1). To cease these stimuli, the cuff was deflated by disconnecting the extensor of the distension device attached to its proximal portion (M2). The procedure was easily performed in most cases. Slow and progressive insufflation allowed subjective adjustment of the intensity of the pain stimulus based on behavioral manifestations. Even with a low rate of complications, the model is feasible and reproducible for studies on visceral pain and the evaluation of analgesic effects.

Endometrial angiogenesis induced by uterine insufflation with an oxygen-ozone gas mixture in mares.

Ozone (O3 ) therapy has been used to improve peripheral tissue oxygenation in humans and domestic animals. The goal of the present study was to characterize histological changes in the endometria of healthy equines following tissue exposure to gas mixtures enriched with different concentrations of O3 . Cycling mares without endometrial degeneration were divided into three groups according to treatment (n = 9 mares/group). The uteri from the O3 , ½O3 and control groups were insufflated for 3 min with gas containing 42, 21 and 0 µg O3 ml-1 , respectively. Treatments were performed every three days from D0 to D6. Endometrial samples were collected immediately before the first treatment and 24 hr after the last treatment. The following nine histological parameters were evaluated: (i) the number of endometrial blood vessels, (ii) endometrial vascular degree (EVD), (iii) increase rate of blood vessels, (iv) increase rate of EVD, (v) glandular total area, (vi) glandular lumen area, (vii) intraglandular secretion area, (viii) glandular epithelial height and (ix) luminal epithelial height. In the O3 group, a positive effect from treatment (p < .01) was detected for all vascular parameters (i, ii, iii and iv), glandular total area, intraglandular secretion area and glandular epithelial height. Compared to the control group, the ½O3 group had greater (p < .01) EVD (84.1 ± 12%) and a higher increase rate of blood vessels (151.9 ± 47.1%). Uterine insufflation with low or intermediate concentrations of the O2 -O3 gas mixture induced endometrial angiogenesis. Morphometry, but not morphology, of the endometrial glands was affected by local O3 therapy. These findings would be of great significance for the development of new therapies for infertility in mares.

Ex vivo comparison of leak testing of canine jejunal enterotomies: Saline infusion versus air insufflation.

OBJECTIVE: To compare the ability to detect leakage of enterotomy closures by intraluminal injection of saline or air. STUDY DESIGN: Ex vivo study. ANIMALS: Grossly normal jejunal segments (n = 60) from five fresh canine cadavers. METHODS: Eight-centimeter jejunal segments were randomly assigned to two control (saline control [n = 5], air control [5]) and two treatment groups (injection of saline [n = 25] or air [25] after enterotomies were closed in a simple continuous pattern using 4-0 glycomer 631). Initial leak pressure (ILP, mean ± SD), maximum intraluminal pressure (MIP), and leakage location were compared. For all air insufflation constructs, the volume of air insufflated at the time of initial leakage was recorded. RESULTS: The ILPs of control segments did not differ whether injected with saline (405.71 ± 56.97 mmHg) or air (376.84 ± 42.54, p = 1.00). Enterotomy closures leaked at lower pressures when injected with air (ILP: 68.52 ± 6.56) compared to saline (87.76 ± 5.20, p = .03). Similar results were obtained when comparing MIPs. A moderate association (r = .51) was identified between volume of air infused and ILPs. The strength of the association improved when stratified by cadaver. The location of leakage-most commonly suture tracks-was identified for all air constructs and for 14 of 25 saline constructs. CONCLUSION: Enterotomy closures leaked at lower pressures after intraluminal injection of air compared to saline. CLINICAL SIGNIFICANCE: Intraoperative leak testing of small intestinal enterotomy closures may be rendered more sensitive and precise by the use of air instead of saline as the infusate.

Water immersion vs. air insufflation in canine duodenal endoscopy: is the future underwater?

Endoscopy represents a commonly employed technique for canine enteropathies. Different trials in human intestinal endoscopy have suggested that the introduction of water for luminal distension, in place of air, improves the visualization of the mucosal texture and decreases pain. The aim of the study was to compare water immersion (WI) vs. air insufflation (AI) during duodenoscopy in anesthetized dogs in terms of mucosal visualization and nociception. Twenty-five dogs undergoing duodenoscopy were included. The same image of the descending duodenum was recorded applying WI and AI. Each pair of images was analyzed using morphological skeletonization, an image entropy evaluation, and a subjective blind evaluation by three experienced endoscopists. To evaluate differences in nociception related to the procedure applied, heart rate and arterial blood pressure were measured before, during and after WI/AI. To compare the two methods, a t-test for paired data was applied for the image analysis, Fleiss' Kappa evaluation for the subjective evaluation and a Friedman test for anesthetic parameters. No differences were found between WI and AI using morphological skeletonization and entropy. The subjective evaluation identified the WI images as qualitatively better than the AI images, indicating substantial agreement between the operators. No differences in nociception were found. The results of the study pointed out the absence of changes in pain response between WI and AI, likely due to the sufficient control of nociception by the anesthesia. Based on subjective evaluation, but not confirmed by the image analysis, WI provided better image quality than AI.

Cardiorespiratory effects of variable pressure thoracic insufflation in cats undergoing video-assisted thoracic surgery.

OBJECTIVE: To evaluate the effects of intrathoracic insufflation on cardiorespiratory variables and working space in cats undergoing video-assisted thoracic surgery. STUDY DESIGN: Prospective randomized study. ANIMALS: Six healthy cats. METHODS: Cats were anesthetized using a standardized protocol. A Swan-Ganz catheter was positioned in the pulmonary artery under fluoroscopic guidance for measurement of cardiac output. Intrathoracic pressures (ITP) of 0 (baseline), 3, and 5 mm Hg were induced with CO2 and maintained for 30 minutes. Statistical comparison of cardiorespiratory variables was performed. After the procedures, all cats were recovered from anesthesia. Videos of thoracic working space at each ITP level were scored in a blinded fashion by 3 board-certified surgeons using a numerical scale from 0-10. RESULTS: All cats tolerated insufflation with 3 and 5 mm Hg for 30 minutes without oxygen desaturation, although ventilatory levels had to be increased substantially to maintain eucapnia and oxygenation. Cardiac index was not significantly different from baseline after 30 minutes at 3 mm Hg but was significantly lower after 30 minutes at 5 mm Hg compared with 3 mm Hg. Oxygen delivery was unaffected by 3 or 5 mm Hg compared with baseline. Scores for working space increased between baseline and 3 and 5 mm Hg but were not different between 3 and 5 mm Hg. CONCLUSION: CO2 insufflation to 5 mm Hg seems well tolerated in healthy cats, provided ventilatory settings are substantially increased as ITP increases. CLINICAL SIGNIFICANCE: Thoracic CO2 insufflation of 3 mm Hg in cats during video-assisted thoracic surgery is associated with less hemodynamic perturbation than 5 mm Hg insufflation and may provide the benefit of improved working space compared with baseline.

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.

Evaluation of post-operative pain after active desufflation at completion of laparoscopy in mares undergoing ovariectomy.

The cause of transient post-operative pain in a subset of horses undergoing laparoscopy is unclear. The objective of this study was to evaluate if residual pneumoperitoneum is associated with transient post-operative pain in mares undergoing ovariectomy. Thirty-eight mares undergoing routine standing laparoscopic ovariectomy were randomly allocated into 2 groups. At the completion of laparoscopy, either the abdominal cavity was actively desufflated or the cannulas were opened to achieve ambient pressure before incisional closure. Assessments were performed for 18 hours after surgery using a validated visceral/somatic pain scale for horses. Overall, pain was minimal in both groups (median score 2/39) post-surgery. Active desufflation of the pneumoperitoneum at the completion of laparoscopy approached statistical significance (P = 0.07) in decreasing pain at 12 hours after laparoscopy. However, effects of active desuffation were not significant throughout the monitored 18-hour post-surgery period. We conclude that the decision to actively desufflate at the completion of laparoscopy should be based on surgeon's preference.

Évaluation de la douleur postopératoire après un désoufflement actif à l'achèvement d'une laparoscopie chez les juments subissant une ovariectomie. La cause d'une douleur postopératoire transitoire dans un sous-groupe de chevaux subissant une laparoscopie est indéterminée. Cette étude avait pour objectif d'évaluer si le pneumopéritoine résiduel est associé à de la douleur postopératoire chez les juments subissant une ovariectomie. Trente-huit juments subissant une ovariectomie laparascopique debout de routine ont été réparties au hasard dans deux groupes. À l'achèvement de la laparoscopie, soit la cavité abdominale a été activement désoufflée ou les canules ont été ouvertes pour obtenir une pression ambiante avant la fermeture de l'incision. Des évaluations ont été réalisées pendant 18 heures après la chirurgie en utilisant une échelle de douleur viscérale/somatique validée pour les chevaux. Dans l'ensemble, la douleur a été minimale dans les deux groupes (note médiane de 2/39) après la chirurgie. La désoufflement actif du pneumopéritoine à l'achèvement de la laparoscopie s'approchait de l'importance statistique (valeur de P = 0,07) en réduisant la douleur à 12 heures après la laparoscopie. Cependant, les effets du désoufflement actif n'étaient pas significatifs pendant la période de surveillance 18 heures après la chirurgie. La décision de désouffler activement à l'achèvement de la laparoscopie est toujours sujette à la préférence du chirurgien.(Traduit par Isabelle Vallières).

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.

Cardiopulmonary effects of pleural insufflation with CO2 during two-lung ventilation in dorsally recumbent anesthetized horses.

OBJECTIVE: To record the cardiopulmonary effects of pleural CO2 positive pressure insufflation in anesthetized horses. STUDY DESIGN: Prospective study. ANIMALS: Seven horses (mean ± standard deviation, 530.9 ± 68.1 kg) undergoing terminal surgery. METHODS: Horses were sedated with xylazine. Anesthesia was induced with ketamine-propofol and maintained with isoflurane, positive pressure ventilation, detomidine infusion, and butorphanol with the horses in dorsal recumbency. Baseline measurements were cardiac output, heart rate, pulmonary and systemic arterial and right atrial blood pressures, body temperature, expired and inspired gas concentrations, and arterial and mixed venous blood gases, electrolytes, glucose, and lactate concentrations. An 18 gauge 6.6 cm needle was inserted into the right pleural cavity midway between the sternum and dorsal midline in the sixth or seventh intercostal space for pleural pressure (PP) measurement. A 14 gauge 18 cm needle placed 5 cm below the previous needle allowed CO2 insufflation into the pleural cavity. All measurements were repeated after: needle insertion, at 2, 5, and 8 mmHg PPs, and after pleural gas removal (GR). Data were compared with baseline using one-way analysis of variance with repeated measures. p < 0.05 was considered significant. RESULTS: Actual PPs were within 1.1 mmHg of the targeted PP. Pulmonary systolic and mean arterial pressures, alveolar dead space to tidal volume ratio, and isoflurane requirements increased at 8 mmHg PP and GR. Cardiac index decreased at 5 mmHg PP. Stroke index decreased at 2 mmHg PP to GR. PaO2 decreased at 5 mmHg PP to GR. PaCO2 increased at 8 mmHg PP and GR. Oxygen delivery decreased at 5 and 8 mmHg PP. Intrapulmonary shunt fraction and lactate concentration increased with GR. CONCLUSIONS AND CLINICAL RELEVANCE: Severe adverse cardiopulmonary effects arise from CO2 positive pressure insufflation into the right hemithorax in dorsally recumbent isoflurane-anesthetized horses. PP should be ≤2 mmHg.

Influence of body weight and body conformation on the pressure-volume curve during capnoperitoneum in dogs.

OBJECTIVE To evaluate the pressure-volume relationship during capnoperitoneum in dogs and effects of body weight and body conformation. ANIMALS 86 dogs scheduled for routine laparoscopy. PROCEDURES Dogs were allocated into 3 groups on the basis of body weight. Body measurements, body condition score, and body conformation indices were calculated. Carbon dioxide was insufflated into the abdomen with a syringe, and pressure was measured at the laparoscopic cannula. Volume and pressure data were processed, and the yield point, defined by use of a cutoff volume (COV) and cutoff pressure (COP), was calculated. RESULTS 20 dogs were excluded because of recording errors, air leakage attributable to surgical flaws, or trocar defects. For the remaining 66 dogs, the pressure-volume curve was linear-like until the yield point was reached, and then it became visibly exponential. Mean ± SD COP was 5.99 ± 0.805 mm Hg. No correlation was detected between yield point, body variables, or body weight. Mean COV was 1,196.2 ± 697.9 mL (65.15 ± 20.83 mL of CO2/kg), and COV was correlated significantly with body weight and one of the body condition indices but not with other variables. CONCLUSION AND CLINICAL RELEVANCE In this study, there was a similar COP for all dogs of all sizes. In addition, results suggested that increasing the abdominal pressure after the yield point was reached did not contribute to a substantial increase in working space in the abdomen. No correlation was found between yield point, body variables, and body weight.

Retroperitoneal Laparoscopy in Dogs: Access Technique, Working Space, and Surgical Anatomy.

OBJECTIVE: To develop and describe a laparoscopic retroperitoneal access technique, investigate working space establishment, and describe the surgical anatomy in the retroperitoneal space as an initial step for clinical application of retroperitoneal laparoscopy in dogs. STUDY DESIGN: Cadaveric and experimental study. ANIMALS: Cadaveric (n=8) and healthy (n=6) adult dogs. METHODS: The retroperitoneal access technique was developed in 3 cadavers based on the human technique and transperitoneal observation. Its application and working space establishment with carbon dioxide (CO2 ) insufflation alone was evaluated in 5 cadavers by observing with a transperitoneal telescope and in 6 live dogs by repeated computed tomography (CT) scans at pressure of 0, 5, 10, and 15 mmHg. Recordings of retroperitoneoscopy as well as working space volume and linear dimensions measured on CT images were analyzed. RESULTS: Retroperitoneal access and working space establishment with CO2 insufflation alone were successfully performed in all 6 live dogs. The only complication observed was in 1 dog that developed subclinical pneumomediastinum. As pressure increased, working space was established from the ipsilateral to the contralateral side, and peritoneal tearing eventually developed. Working space volume increased significantly from 5 mmHg and linear dimensions increased significantly from 0 to 10 mmHg. With pneumo-retroperitoneum above 5 mmHg, retroperitoneal organs, including kidneys and adrenal glands, were easily visualized. CONCLUSION: The retroperitoneal access technique and working space establishment with CO2 insufflation starting with 5 mmHg and increasing to 10 mmHg provided adequate working space and visualization of retroperitoneal organs, which may allow direct access for retroperitoneal laparoscopy in dogs.

Video-Assisted Thoracoscopic Resection of a Noninvasive Thymoma in a Cat with Myasthenia Gravis Using Low-Pressure Carbon Dioxide Insufflation.

OBJECTIVE: To report the use of low-pressure carbon dioxide insufflation during video-assisted thoracoscopic surgery for resection of a noninvasive thymoma in a cat with secondary myasthenia gravis. STUDY DESIGN: Clinical case report. ANIMAL: Client-owned cat. METHODS: An 11-year-old castrated male domestic shorthair cat was examined for generalized weakness, voice change, hypersalivation, hyporexia, vomiting, coughing, and gagging. Thoracic ultrasound revealed a cranial mediastinal mass for which cytology was consistent with a thymoma (or lymphoid tissue). Acetylcholine receptor antibody concentration was elevated at 3.16 mmol/L (reference interval < 0.3 mmol/L). Thoracic computed tomography showed two round, contrast-enhancing structures in the cranioventral mediastinum identified as the sternal lymph node and a cranial mediastinal mass (11 × 17 × 24 mm). A presumptive diagnosis of thymoma with paraneoplastic myasthenia gravis was made and surgical resection of both mediastinal masses was recommended. RESULTS: Video-assisted thoracoscopic resection of the cranial mediastinal mass and sternal lymph node were performed with low-pressure carbon dioxide insufflation maintained at an intrathoracic pressure of 2-3 mmHg. The cat recovered from surgery without serious complications. Nineteen months after surgery, the cat developed hind limb stiffness. Thoracic radiographs ruled out a cranial mediastinal mass or megaesophagus. Acetylcholine receptor antibody concentration remained elevated at 2.72 mmol/L. CONCLUSION: Low-pressure thoracic insufflation facilitated video-assisted thoracoscopic resection of cranial mediastinal masses in this cat.

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.

Computed Tomography Determined Changes in Position of the Hepatobiliary and Gastrointestinal Systems after CO2 Insufflation to Determine Optimal Positioning for Abdominal Laparoscopy.

OBJECTIVE: To evaluate changes in body position and effect of CO2 insufflation on the hepatobiliary and gastrointestinal systems using computed tomography (CT) to determine optimal laparoscopic approach. STUDY DESIGN: Experimental study. ANIMALS: Healthy intact female Beagles (n = 6) of similar age, weight, and body condition score. METHODS: Urinalysis, peripheral blood smear, and abdominal ultrasonography were performed to determine dog health. A series of pre insufflation (PrI) CT scans in ventrodorsal routine (VDR), ventrodorsal Trendelenburg (VDT), left lateral (LL), and right lateral (RL) recumbency were performed before and after abdominal insufflation (PoI) with CO2 (10-14 mm Hg). Pre-determined measurements were made on PrI and PoI scans and differences compared. RESULTS: Liver position was affected by body position and under gravitational influence moved to the dependent part of the abdominal cavity. The gallbladder was best exposed in LL. Stomach position was not significantly changed after insufflation. Different areas of small intestine were dependent on gravitational effects. The pancreas maintained a similar position after insufflation. CONCLUSIONS: VDR was the ideal position for all laparoscopic procedures of the liver. The LL position could be used for surgery of the gallbladder but likely provides poor exposure to the rest of the liver. In approaching the stomach and intestines, the area of interest should be used to determine the best position.