To investigate the effects of a xylazine infusion during isoflurane anesthesia on global perfusion parameters and gastrointestinal oxygenation and microperfusion, 8 adult warmblood horses were sedated with xylazine and anesthesia induced with midazolam and ketamine. Horses were mechanically ventilated during anesthesia. After 3 h of stable isoflurane anesthesia (FEIso 1.3 Vol %), a xylazine infusion with 1 mg/kg body weight (BW) per hour was started for 1 h and then stopped. Before, during, and after xylazine infusion, heart rate (HR), arterial blood pressure (MAP), cardiac output (CO), central venous pressure (CVP), and pulmonary artery pressure (PAP) were measured and systemic vascular resistance (SVR) was calculated. Arterial blood gases were taken and oxygen delivery (DO2) and alveolar dead space (VDalv) were calculated. Further intestinal oxygen and microperfusion were measured using white light spectroscopy and laser Doppler flowmetry. Surface probes were placed via median laparotomy on the stomach, the jejunum, and the colon. Wilcoxon rank-sum test was used to compare values over time (P < 0.05). During xylazine infusion, MAP, CVP, PAP, SVR, and VDalv increased significantly, whereas CO, DO2, and intestinal microperfusion decreased. Intestinal oxygenation remained unchanged. All parameters returned to pre-xylazine values within 1 h after stopping xylazine infusion. A xylazine infusion during constant isoflurane anesthesia in horses impairs global and intestinal perfusion without changing tissue oxygenation in normoxic healthy horses. Further studies are necessary, however, to evaluate whether a possible reduction of isoflurane concentration by xylazine infusion will ameliorate these negative effects.

A rabbit serosal scarification model was utilized to compare the ability of four drugs, previously administered peri-operatively to horses undergoing exploratory celiotomy, to prevent the development of postoperative intestinal adhesions. The substances compared were 32% Dextran 70 (7 mL/kg), 1% sodium carboxymethylcellulose (7 mL/kg), trimethoprim-sulfadiazine (30 mg/kg), and flunixin meglumine (1 mg/kg). The first two were administered intra-abdominally following surgery, while the latter two were administered systemically in the peri-operative period. Fibrous adhesions were evident in all animals in the untreated serosal scarification group. No significant difference in the number of animals with adhesions was found between the untreated control group and any treatment group, nor among the treatment groups. Microscopic examination of adhesions collected at postmortem examination revealed fibers consistent with cotton, surrounded by a giant-cell reaction and ongoing acute inflammation. The source of the fibers was likely the cotton laparotomy sponges used to scarify the intestinal surface, since the pattern in the granuloma and sponge fibers appeared similar under polarized light. Though consistent intestinal adhesion formation was produced in the rabbit, the presence of foreign body granulomas may prevent consideration of this model for future research. The drugs tested were ineffective in preventing the formation of postoperative small intestinal adhesions in this model.

The effect of right paralumbar fossa exploratory celiotomy and omentopexy on peritoneal fluid constituents was studied in 22 adult dairy cows. Six cows were eliminated on the basis of physical examination findings (n = 2), surgical findings (n = 2), or inability to obtain a sufficient volume of peritoneal fluid (n = 2). Sixteen cattle had normal results of Csc and serum biochemical analysis, and a minimum of 1 ml of peritoneal fluid was obtained by abdominocentesis. Abdominocentesis was repeated on days 1, 2, and 6 after surgery. Statistical analysis for repeated measures was performed, using a significance level of P < 0.05. Stage of gestation was evaluated for interaction with time. Mean total nucleated cell count was 3,200 cells/1 before surgery, was significantly increased 2 days after surgery (16,336 cells/microliter), and continued to increase through day 6 (20,542 cells/microliter). Mean polymorphonuclear cell count was 1,312 cells/microliter before surgery and was significantly higher at 2 (11,043 cells/microliter) and 6 (10,619 cells/microliter) days after surgery. Mean lymphocyte count was 254 cells/microliter before surgery and was significantly increased 2 days (1,911 cells/microliter) after surgery. By day 6, lymphocyte numbers were similar to preoperative values. Mean mononuclear cell count was 770 cells/microliter before surgery and was significantly increased on days 1 (3,084 cells/microliter), 2 (3,285 cells/microliter and 6 (2,349 cells/microliter) after surgery. Mean eosinophil numbers were 1,388 cells/microliter before surgery and were significantly increased on day 6 (6,347 cells/microliter) only. Interaction between time and stage of gestation was found only for specific gravity and total protein concentration. In general, specific gravity and total protein concentration increased after surgery (mean before surgery, 1.016 and 3.6 g/dl; mean after surgery, 1.021 and 5.6 g/dl). Left paralumbar fossa celiotomy performed 7 days after surgery did not reveal complications of repeated abdominocentesis, and pregnancy status was unchanged. Peritoneal fluid constituents are highly variable after exploratory celiotomy and omentopexy in cattle. However, results of this study may provide a reference for interpretation of postoperative peritoneal fluid sample findings in cattle.

OBJECTIVE To determine the optimal energy profile for and to assess the feasibility and efficacy of ultrasonographic and laparoscopic guidance for microwave ablation (MWA) of clinically normal canine ovaries. SAMPLE 44 extirpated ovaries from 22 healthy dogs. PROCEDURES In the first of 2 trials, 13 dogs underwent oophorectomy by routine laparotomy. Extirpated ovaries underwent MWA at 45 W for 60 (n = 11) or 90 (12) seconds; 3 ovaries did not undergo MWA and served as histologic controls. Ovaries were histologically evaluated for cell viability. Ovaries without viable cells were categorized as completely ablated. Histologic results were used to identify the optimal MWA protocol for use in the subsequent trial. In the second trial, the ovaries of 9 dogs underwent MWA at 45 W for 90 seconds in situ. Ultrasonographic guidance for MWA was deemed unfeasible after evaluation of 1 ovary. The remaining 17 ovaries underwent MWA with laparoscopic guidance, after which routine laparoscopic oophorectomy was performed. Completeness of ablation was histologically assessed for all ovaries. RESULTS 2 ovaries were excluded from the trial 1 analysis because of equivocal cell viability. Six of 11 ovaries and 10 of 10 ovaries that underwent MWA for 60 and 90 seconds, respectively, were completely ablated. In trial 2, laparoscopic-guided MWA resulted in complete ablation for 12 of 17 ovaries. Dissection of the ovarian bursa for MWA probe placement facilitated complete ablation. CONCLUSIONS AND CLINICAL RELEVANCE Laparoscopic-guided MWA at 45 W for 90 seconds was feasible, safe, and effective for complete ablation of clinically normal ovaries in dogs.

OBJECTIVE To assess effects of major abdominal surgery on serum cortisol and aldosterone and plasma canine ACTH (cACTH) concentrations. ANIMALS 39 healthy dogs undergoing laparotomy during veterinary student surgical laboratories. PROCEDURES Blood samples were obtained before and at completion of surgery. Serum cortisol and aldosterone and plasma cACTH concentrations were measured by use of validated radioimmunoassays. Changes in concentrations (postoperative concentration minus preoperative concentration) were calculated. Data were analyzed by use of the Wilcoxon signed rank test, Pearson correlation analysis, and Mann-Whitney rank sum test. RESULTS Cortisol, aldosterone, and cACTH concentrations increased significantly from before to after surgery. Although cortisol and aldosterone concentrations increased in almost all dogs, cACTH concentrations decreased in 6 of 32 (19%) dogs. All dogs had preoperative cortisol concentrations within the reference range, but 24 of 39 (62%) dogs had postoperative concentrations above the reference range. A correlation between the change in cACTH concentration and the change in cortisol concentration was not detected. CONCLUSIONS AND CLINICAL RELEVANCE Laparotomy caused a significant increase in serum cortisol and aldosterone concentrations. In most dogs, but not all dogs, plasma cACTH concentrations increased. Lack of correlation between the change in cACTH concentration and the change in cortisol concentration suggested that increased postoperative cortisol concentrations may have been attributable to ACTH-independent mechanisms, an early ACTH increase that caused a sustained cortisol release, or decreased cortisol clearance. Further studies are indicated to evaluate the effects of various anesthetic protocols and minimally invasive surgical techniques on the stress response.

Objective-To develop laparoscopic-assisted techniques for enterostomy feeding tube placement and full-thickness biopsy of the jejunum in dogs. Animals-15 healthy dogs. Procedure-Dogs were anesthetized, and positive pressure ventilation was provided. A trocar cannula for the laparoscope was inserted on the ventral midline caudal to the umbilicus. For enterostomy tube placement, a second trocar cannula was placed lateral to the right rectus abdominis muscle, and a Babcock forceps was used to grasp the duodenum and elevate it to the incision made for the cannula. The duodenum was sutured to the abdominal wall, and a feeding tube was inserted. For jejunal biopsy, a third trocar cannula was placed lateral to the left rectus abdominis muscle. A portion of jejunum was elevated to the incision for the second or third cannula, and a full-thickness biopsy specimen was obtained. A second specimen was obtained from another portion of jejunum, and retention sutures for the 2 biopsy sites were tied so that serosal surfaces of the biopsy sites were apposed to each other. Dogs were euthanatized 30 days after surgery. Results-The enterostomy tube was properly positioned and functional in all 8 dogs that underwent laparoscopic-assisted enterostomy tube placement, and sufficient samples for histologic examination were obtained from all 7 dogs that underwent laparoscopic-assisted jejunal biopsy. None of the dogs had any identifiable problems after surgery. Conclusion and Clinical Relevance-Results suggest that in dogs, laparoscopic-assisted procedures for enterostomy tube placement and jejunal biopsy are an acceptable alternative to procedures performed during a laparotomy.

OBJECTIVE To investigate the use of microwave ablation (MWA) with cooling urethral perfusion and with no perfusion (MWA-UP and MWA-NP, respectively) for prostate gland ablation in canine cadavers. ANIMALS Cadavers of 18 sexually intact male dogs. PROCEDURES After technique refinement in 2 cadavers, laparotomy with ultrasound-guided MWA-UP (n = 8) or MWA-NP (8) of the prostate gland was performed in 16 cadavers. Normograde cystourethroscopy was performed before and after treatment; recorded images were reviewed in a blinded manner for scoring of urethral mucosal discoloration and loss of integrity. Difficulty with cystoscope insertion was recorded if present. Excised prostate glands were fixed for serial sectioning, gross measurements, and calculation of percentage ablation. Percentages of prostate tissue necrosis from MWA, denuded urethral mucosa, and depth of epithelial surface loss in an adjacent section of the colon were estimated histologically. Variables of interest were statistically analyzed. RESULTS Difficulty with cystoscope insertion after treatment was significantly more common and scores for urethral mucosal discoloration and loss of integrity were significantly higher (indicating more severe lesions) for the MWA-NP group than for the MWA-UP group. The histologically assessed percentage of denuded urethral mucosa was also greater for the MWA-NP group. Overall median percentage prostate gland ablation was 73%; this result was not associated with prostate gland volume or chronological order of treatment. CONCLUSIONS AND CLINICAL RELEVANCE MWA-UP induced subtotal thermal necrosis of prostate glands in canine cadavers while limiting urethral mucosal injury. Further study is required to optimize the technique and evaluate its safety and efficacy in vivo as a future curative-intent treatment for prostatic tumors in dogs.

Objective—To evaluate the use of a micro-lightguide tissue spectrophotometer for measurement of tissue oxygenation and blood flow in the small and large intestines of horses under anesthesia. Animals—13 adult horses without gastrointestinal disease. Procedures—Horses were anesthetized and placed in dorsal recumbency. Ventral midline laparotomy was performed. Intestinal segments were exteriorized to obtain measurements. Spectrophotometric measurements of tissue oxygenation and regional blood flow of the jejunum and pelvic flexure were obtained under various conditions that were considered to have a potential effect on measurement accuracy. In addition, arterial oxygen saturation at the measuring sites was determined by use of pulse oximetry. Results—12,791 single measurements of oxygen saturation, relative amount of hemoglobin, and blood flow were obtained. Errors occurred in 381 of 12,791 (2.98%) measurements. Most measurement errors occurred when surgical lights were directed at the measuring site; covering the probe with the surgeon's hand did not eliminate this error source. No measurement errors were observed when the probe was positioned on the intestinal wall with room light, at the mesenteric side, or between the mesenteric and antimesenteric side. Values for blood flow had higher variability, and this was most likely caused by motion artifacts of the intestines. Conclusions and Clinical Relevance—The micro-lightguide spectrophotometry system was easy to use on the small and large intestines of horses and provided rapid evaluation of the microcirculation. Results indicated that measurements should be performed with room light only and intestinal motion should be minimized.

Objective-To evaluate efficacy and safety of IP administration of high-molecular-weight carboxymethylcellulose (HMW CMC) for the prevention of postoperative intra-abdominal adhesions in ponies. Animals-10 ponies. Procedure-A 1% solution of HMW CMC was instilled intra-abdominally prior to surgery in 5 ponies, whereas 5 control ponies did not receive HMW CMC. Postoperative adhesions were induced by use of a bowel-abrasion method comprising laparotomy, typhlotomy, and abrasion of jejunal serosa at multiple sites with placement of 3 sutures at each site. Day of surgery was day 0. After surgery, ponies were monitored, and hematologic, serum biochemical, and peritoneal fluid analyses were performed on days 1, 2, 3, 5, 7, and 10. On day 10, ponies were euthanatized. Intra-abdominal adhesions were recorded, and tissue samples were collected for histologic examination. Results-A significantly greater number of adhesions, number of multiple adhesions, and mean incidence of adhesions were identified in control ponies, compared with CMC-treated ponies. Mean peritoneal fluid WBC count on day 7 and serum fibrinogen concentrations on days 5 and 7 were significantly higher in control ponies, compared with CMC-treated ponies. Results of serum biochemical analyses did not differ significantly between the 2 groups. Conclusions and Clinical Relevance-Intra-abdominal use of 1% HMW CMC during surgery was effective for preventing postoperative adhesions in ponies. Use of HMW CMC did not have detrimental effects on wound healing, intra-abdominal defenses, or patient health. A 1% solution of HMW CMC may be used routinely during abdominal surgery of horses for prevention of postoperative adhesions.

Plasma and peritoneal fluid samples were collected before and after surgery from 6 horses undergoing a ventral midline exploratory laparotomy and from 6 anesthetized control horses. Coagulation/fibrinolytic components measured in the plasma and peritoneal fluid of these horses included the functional activity of antithrombin III, alpha-2 antiplasmin, plasminogen, and protein C, and the concentrations of fibrinogen and fibrin degradation products. Peritoneal fluid antithrombin III, fibrin degradation products, and plasminogen values were significantly increased after surgery (over time) in principal horses. Compared with control horses, postoperative peritoneal fluid from horses undergoing laparotomy had significantly increased antithrombin-III activity at 12 and 72 hours, alpha-2 antiplasmin activity at 24 hours, fibrin degradation product concentrations at 6, 12, 24, 72, 96, and 144 hours, plasminogen activity at 6, 12, 24, 48, 72, and 96 hours, and protein-C activity at 12, 24, 72, and 96 hours. There were no significant changes in the peritoneal fibrinogen concentration in principal horses. Plasma plasminogen activity was significantly decreased at 24 hours after surgery in principal horses, compared with controls. Changes were minimal in the remaining plasma coagulation/fibrinolytic components of horses undergoing laparotomy. Plasma and peritoneal fluid values of anesthetized control horses did not change.