OBJECTIVE To evaluate the potential usefulness of epiduroscopy for clinical diagnosis and treatment of vertebral canal and spinal cord lesions in dogs.
SAMPLE Cadavers of 6 mixed-breed dogs.
PROCEDURES Dogs were positioned in sternal recumbency, and an endoscope was introduced into the lumbosacral epidural space. A fiberscope (diameter, 0.9 mm; length, 30 cm) was used for 3 dogs, and a videoscope (diameter, 2.8 mm; length, 70 cm) was used for the other 3 dogs. Visibility and identities of anatomic structures were recorded, and maneuverability of the endoscopes was assessed. Extent of macroscopic tissue damage was evaluated by manual dissection of the vertebral canal at the end of the procedure.
RESULTS Intermittent saline (0.9% NaCl) solution infusion, CO2 insufflation, and endoscope navigation improved visualization by separating the epidural fat from the anatomic structures of interest. Images obtained with the fiberscope were small and of poor quality, making identification of specific structures difficult. Maneuverability of the fiberscope was difficult, and target structures could not be reliably reached or identified. Maneuverability and image quality of the videoscope were superior, and spinal nerve roots, spinal dura mater, epidural fat, and blood vessels could be identified. Subsequent manual dissection of the vertebral canal revealed no gross damage in the spinal cord, nerve roots, or blood vessels.
CONCLUSIONS AND CLINICAL RELEVANCE A 2.8-mm videoscope was successfully used to perform epiduroscopy through the lumbosacral space in canine cadavers. Additional refinement and evaluation of the technique in live dogs is necessary before its use can be recommended for clinical situations.
OBJECTIVE To compare cardiac output (CO) measured by use of CT coronary angiography and thermodilution (criterion-referenced standard) at various CO values, record adverse effects, and determine the time needed to measure CO.
ANIMALS 5 healthy purpose-bred Beagles (2 males and 3 females).
PROCEDURES A prospective nonrandomized crossover study was conducted. Dogs were premedicated with butorphanol tartrate (0.2 mg•kg−1, IM). Anesthesia was induced by IV administration of etomidate (1 to 2 mg•kg−1) and midazolam (0.25 mg•kg−1). Orotracheal intubation was performed, and anesthesia was maintained by administration of isoflurane. The CO was determined by use of thermodilution and by use of CT at 3 CO values. Dobutamine was infused at various rates to obtain the 3 CO values.
RESULTS 13 values were obtained and analyzed. The mean ± SD difference between methods was 0.09 ± 0.71 L•min−1 (95% confidence interval [CI], 0.52 to −0.34 L•min−1). Only 1 of 13 values was located on the 100% agreement line (ie, 0 line), 7 of 13 values were located within the 95% CI, and 5 of 13 values were outside the 95% CI.
CONCLUSIONS AND CLINICAL RELEVANCE For this study, there was poor agreement between the 2 methods. The 95% CI interval was 0.52 to −0.34 L•min−1, and 5 of 13 values were outside the 95% CI. Therefore, results for the CT method appeared to be inappropriate for use in making clinical decisions.
OBJECTIVE To evaluate the use of a modified passive leg-raising maneuver (PLRM) to predict fluid responsiveness during experimental induction and correction of hypovolemia in isoflurane-anesthetized pigs.
ANIMALS 6 healthy male Landrace pigs.
PROCEDURES Pigs were anesthetized with isoflurane, positioned in dorsal recumbency, and instrumented. Following induction of a neuromuscular blockade, pigs were mechanically ventilated throughout 5 sequential experimental stages during which the blood volume was manipulated so that subjects transitioned from normovolemia (baseline) to hypovolemia (blood volume depletion, 20% and 40%), back to normovolemia, and then to hypervolemia. During each stage, hemodynamic variables were measured before and 3 minutes after a PLRM and 1 minute after the pelvic limbs were returned to their original position. The PLRM consisted of raising the pelvic limbs and caudal portion of the abdomen to a 15° angle relative to the horizontal plane.
RESULTS Hemodynamic variables did not vary in response to the PLRM when pigs were normovolemic or hypervolemic. When pigs were hypovolemic, the PLRM resulted in a significant increase in cardiac output and decrease in plethysomographic variability index and pulse pressure variation. When the pelvic limbs were returned to their original position, cardiac output and pulse pressure variation rapidly returned to their pre-PLRM values, but the plethysomographic variability index did not.
CONCLUSIONS AND CLINICAL RELEVANCE Results suggested a modified PLRM might be useful for identification of hemodynamically unstable animals that are likely to respond to fluid therapy. Further research is necessary to validate the described PLRM for prediction of fluid responsiveness in clinically ill animals.
To compare initial leak pressure (ILP) between cadaveric canine and synthetic small intestinal segments that did and did not undergo enterotomy.
Eight 8-cm grossly normal jejunal segments from 1 canine cadaver and eight 8-cm synthetic small intestinal segments.
Intestinal segments were randomly assigned to undergo enterotomy (6 cadaveric and 6 synthetic segments) or serve as untreated controls (2 cadaveric and 2 synthetic segments). For segments designated for enterotomy, a 2-cm full-thickness incision was created along the antimesenteric border. The incision was closed in a single layer with 4-0 suture in a simple continuous pattern. Leak testing was performed with intestinal segments occluded at both ends and infused with dilute dye solution (999 mL/h) until the solution was observed leaking from the suture line or serosal tearing occurred. Intraluminal pressure was continuously monitored. The ILP at construct failure was compared between cadaveric and synthetic control segments and between cadaveric and synthetic enterotomy segments.
Mean ± SD ILP did not differ significantly between cadaveric (345.11 ± 2.15 mm Hg) and synthetic (329.04 ± 24.69 mm Hg) control segments but was significantly greater for cadaveric enterotomy segments (60.77 ± 15.81 mm Hg), compared with synthetic enterotomy segments (15.03 ± 6.41 mm Hg).
CONCLUSIONS AND CLINICAL RELEVANCE
Leak testing should not be used to assess the accuracy or security of enterotomy suture lines in synthetic intestinal tissue. Synthetic intestinal tissue is best used for students to gain confidence and proficiency in performing enterotomies before performing the procedure on live animals.
Objective—To evaluate effects of commonly used anesthetics administered as single bolus injections on splenic volume.
Animals—10 adult Beagles.
Procedures—A randomized crossover study was conducted. Computed tomography was performed on dogs to determine baseline splenic volume and changes after IV injection of assigned drug treatments. Dogs were allowed to acclimate for 10 minutes in a plastic crate before acquisition of abdominal CT images. Treatments were administered at 7-day intervals and consisted of IV administration of saline (0.9% NaCl) solution (5 mL), acepromazine maleate (0.03 mg/kg), hydromorphone (0.1 mg/kg), and dexmedetomidine (0.005 mg/kg) to all 10 dogs; thiopental (8 mg/kg) to 5 of the dogs; and propofol (5 mg/kg) to the other 5 dogs. Splenic volume was calculated from the CT images with image processing software. A repeated-measures ANOVA was performed, followed by a Bonferroni post hoc test.
Results—No significant difference in splenic volume was detected between the acepromazine, propofol, and thiopental treatments, but splenic volume was greater with these drugs than with saline solution, hydromorphone, and dexmedetomidine. Splenic volume was less with hydromorphone, compared with dexmedetomidine, but splenic volume with hydromorphone and dexmedetomidine did not differ significantly from that with saline solution.
Conclusions and Clinical Relevance—Administration of acepromazine, thiopental, and propofol resulted in splenomegaly. Dexmedetomidine did not alter splenic volume. Hydromorphone slightly decreased splenic volume. Propofol should not be used when splenomegaly is not desirable, whereas hydromorphone and dexmedetomidine may be used when it is best to avoid splenic enlargement.
To evaluate cardiac output (CO) measurements using transpulmonary ultrasound (TPUD) technology and compare results with those of the gold standard, pulmonary arterial catheter thermodilution (PACTD), in 6 healthy anesthetized pigs during acute hemodynamic changes caused by manipulation of the blood volume.
6 healthy male Landrace pigs.
Over a period of 1 week, pigs were anesthetized with isoflurane, mechanically ventilated, and underwent instrumentation in dorsal recumbency. They were subjected to sequential experimental states during which the blood volume was manipulated so that the animals transitioned from normovolemia to hypovolemia (20% and 40% of blood volume depletion), back to normovolemia (autologous blood transfusion), and then to hypervolemia (following colloid bolus). During each volume state, CO measurements were compared between TPUD and PACTD.
The mean ± SD relative bias between TPUD and PACTD was 7.71% ± 21.2% with limits of agreement –33.9% to 49.3%, indicating TPUD slightly underestimated CO values, compared with values obtained with PACTD. The mean ± SD of the bias between the 2 methods was 0.13 ± 0.5 L/min. Only 5 of 36 (13.9%) TPUD CO measurements had an absolute value of relative bias > 30%. The percentage error calculated for TPUD was 29.4%.
Results suggested that TPUD measurements have acceptable agreement with PACTD measurements. Moreover, TPUD exhibits promising potential in being used interchangeably with PACTD for future hemodynamic research involving swine as species of interest.
Objective—To determine the minimal electric threshold (MET) of neurostimulation in and out of the lumbosacral epidural space necessary to cause muscle contraction of the hind limb or tail, determine an MET cutoff value that indicates epidural needle placement, and compare predictability of epidural needle placement attained by use of neurostimulation versus the standard technique that uses loss of resistance in dogs.
Animals—96 healthy Beagles.
Procedures—Dogs received nonionic contrast medium (90 mg/kg) either in or out of the epidural space. Correct placement of the needle was evaluated by use of neurostimulation and loss of resistance of injection and confirmed by use of epidurography.
Results—With the neurostimulator test, MET was significantly lower in dogs with needle placement in the epidural space (mean ± SEM, 0.30 ± 0.07 mA) than those with needle placement out of the epidural space (1.2 ± 0.13 mA). When an electric current cutoff of ≤ 0.28 mA for the neurostimulator test was used to suggest correct needle placement in the lumbosacral epidural space, sensitivity and specificity were 74% and 93%, respectively. The loss of resistance test had sensitivity of 63% and specificity of 90%. The combination of both tests yielded a sensitivity of 89% and specificity of 83%.
Conclusions and Clinical Relevance—Neurostimulation is a useful tool to suggest correct lumbosacral epidural needle placement in dogs.
Objective—To assess the accuracy of an ultrasound velocity dilution cardiac output (UDCO) method, compared with that of the lithium dilution cardiac output (LiDCO) method, for determination of cardiac output (CO) in juvenile horses with experimentally induced hypovolemia.
Animals—12 anesthetized 2- to 6-month-old horses.
Procedures—For each anesthetized horse, CO was determined by the LiDCO and UDCO methods prior to any intervention (baseline state), after withdrawal of approximately 40% of the horse's blood volume (low CO state), after maintenance of hypovolemia and infusion of norepinephrine until mean arterial blood pressure was equal to baseline value (high CO state), and after further infusion of norepinephrine and back-transfusion of withdrawn blood (posttransfusion state). For each of the 4 hemodynamic situations, CO and calculated cardiac index (CI) values were obtained by each method in duplicate (8 pairs of measurements/horse); mean values for each horse and overall mean values across all horses were calculated. Agreement between CI determined by each method (96 paired values) was assessed by Bland-Altman analysis.
Results—For the UDCO method–derived CI measurements among the 12 horses, mean ± SD bias was −4 ± 11.3 mL/kg/min (95% limits of agreement, −26.1 to 18.2 mL/kg/min) and mean relative bias was −10.4 ± 21.5% (95% limits of agreement, −52.6% to 31.8%).
Conclusions and Clinical Relevance—Results indicated that, compared with the LiDCO method, the UDCO method has acceptable clinical usefulness for determination of CO in foals.
OBJECTIVE To evaluate a percutaneous, continuous gastric decompression technique for dogs involving a temporary T-fastener gastropexy and self-retaining decompression catheter.
ANIMALS 6 healthy male large-breed dogs.
PROCEDURES Dogs were anesthetized and positioned in dorsal recumbency with slight left-lateral obliquity. The gastric lumen was insufflated endoscopically until tympany was evident. Three T-fasteners were placed percutaneously into the gastric lumen via the right lateral aspect of the abdomen, caudal to the 13th rib and lateral to the rectus abdominis muscle. Through the center of the T-fasteners, a 5F locking pigtail catheter was inserted into the gastric lumen and attached to a device measuring gas outflow and intragastric pressure. The stomach was insufflated to 23 mm Hg, air was allowed to passively drain from the catheter until intraluminal pressure reached 5 mm Hg for 3 cycles, and the catheter was removed. Dogs were hospitalized and monitored for 72 hours.
RESULTS Mean ± SD catheter placement time was 3.3 ± 0.5 minutes. Mean intervals from catheter placement to a ≥ 50% decrease in intragastric pressure and to ≤ 6 mm Hg were 2.1 ± 1.3 minutes and 8.4 ± 5.1 minutes, respectively. After catheter removal, no gas or fluid leakage at the catheter site was visible laparoscopically or endoscopically. All dogs were clinically normal 72 hours after surgery.
CONCLUSIONS AND CLINICAL RELEVANCE The described technique was performed rapidly and provided continuous gastric decompression with no evidence of postoperative leakage in healthy dogs. Investigation is warranted to evaluate its effectiveness in dogs with gastric dilatation-volvulus.
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.
44 extirpated ovaries from 22 healthy dogs.
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.
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.