The recombinant DNA technology

The recombinant DNA technology or DNA cloning permits the isolation, amplification, and precise manipulation of specific DNA fragments. This is generally accomplished by linking or recombining the desired DNA fragment with a DNA molecule, termed the vector, which is capable of directing the replication of itself in a suitable host cell and any DNA segment covalently attached to it. Using this and associated technologies, it is possible to produce large amounts of specific proteins and to modify cell types by introducing the genes for proteins that are otherwise absent. Moreover, it is now possible to construct variants of naturally-occurring proteins with improved biological or physical properties.     

Thoracoscopic Thoracic Duct Ligation and Thoracoscopic Pericardectomy for Treatment of Chylothorax in Dogs

Objective— To report the use of thoracoscopic thoracic duct ligation (TDL) and pericardectomy for treatment of chylothorax.
Study Design— Case series.
Animals— Dogs with chylothorax (n=12).
Methods— Dogs with secondary or idiopathic chylothorax had thoracoscopy performed in sternal recumbency through 3 portals in the caudal right hemithorax for TDL and were then repositioned in dorsal recumbency for pericardectomy. Portals were placed in the 5th and 7th intercostal spaces of the right hemithorax with 1 transdiaphragmatic portal in the right paraxiphoid position. Follow-up was performed by recheck examination or telephone interview to determine outcome.
Results— Seven dogs (58%) had idiopathic chylothorax; 6 dogs (85.7%) had complete resolution of their effusion, whereas only 2 of the 5 nonidiopathic dogs (40%) had complete resolution.
Conclusions— Thoracoscopy is minimally invasive, provides excellent observation, and allows for ligation of the thoracic duct in the caudal thorax. Patients with idiopathic chylothorax may have a better prognosis after TDL and pericardectomy than dogs with nonidiopathic chylothorax.
Clinical Relevance— Thoracoscopy for ligation of the thoracic duct and pericardectomy is an acceptable surgical technique for treatment of chylothorax.     

Microvascular Free Tissue Transfer: Results in 57 Consecutive Cases

Objective —To evaluate the outcomes and complications in a consecutive series of animals undergoing microvascular reconstructive procedures at two veterinary institutions. Study Design—Retrospective study. Animals or Sample Population—A total of 44 client-owned dogs and one red-necked wallaby. Methods —The medical records of all animals undergoing reconstructive microsurgical procedures at the Western College of Veterinary Medicine and Michigan State University were reviewed. Microvascular flap survival and related complications were described. Statistical analysis was performed to determine the significance of relationships between operative factors and outcome. Results —A total of 57 microvascular procedures were performed on 55 animals. Reconstruction was required after trauma in 42 animals, after ablative cancer surgery in 11 animals and for correction of congenital tissue aplasia in 1 animal. Donor tissues included the superficial cervical cutaneous, medial saphenous fasciocutaneous or musculofasciocutaneous, caudal superficial epigastric cutaneous, trapezius muscle or musculocutaneous, caudal sartorius muscle, latissimus dorsi muscle or musculocutaneous, cranial abdominal myoperitoneal, carpal footpad, digital footpad, and vascularized ulnar bone flaps. A total of 53 of 57 flaps (93%) survived. There was a significant relationship between flap failure and level of assistant surgeon experience (P < .05). Latissimus dorsi flaps were significantly more likely to fail when compared with pooled data from all other flap types (P < .01). Conclusions —The success of microvascular tissue transfer in this case series compares favorably with those reported in human reconstructive microsurgery. Both the primary and assistant surgeon should be practiced in microsurgical technique. Failure of latissimus dorsi flaps was not likely caused by an inherently deficient flap design, but was more likely attributed to the location and severity of trauma at the recipient site, the difficulty in isolating suitable recipient vessels for anastomosis or the absence of a trained assistant surgeon during these procedures. Clinical Relevance —This retrospective study documents the successful application of microvascular technique in a series of clinical cases requiring tissue reconstruction.     

Plasma Concentrations and Cardiovascular Influence of Lidocaine Infusions During Isoflurane Anesthesia in Healthy Dogs and Dogs With Subaortic Stenosis

Objective—To determine the plasma concentrations and cardiovascular changes that occur in healthy dogs and dogs with aortic stenosis that are given an infusion of lidocaine during isoflurane anesthesia. Study Design—Phase 1, controlled randomized cross-over trial; Phase 2, before and after trial Animals—Phase 1, 6 healthy dogs (4 female, 2 male) weighing 23.8 ± 7.4 kg; Phase 2, 7 dogs (4 female, 3 male) with moderate to severe subaortic stenosis (confirmed by Doppler echocardiography) weighing 31.1 ± 14.5 kg. Methods—After mask induction, intubation, and institution of positive pressure ventilation, instrumentation was performed to measure hemodynamic variables. After baseline, measurement at an end-tidal isoflurane concentration of 1.9% (phase 1) or 1.85% (phase 2), a loading dose infusion of lidocaine at 400 μg/kg/min was given. Phase 1: Maintenance doses of lidocaine were administered consecutively (40, 120, and 200 μg/kg/min) after the loading dose (given for 10, 10, and 5 minutes, respectively) in advance of each maintenance concentrations. Measurements were taken at the end of each loading dose and at 25 and 35 minutes during each maintenance level. The same animals on a different day were given dextrose 5% and acted as the control. Phase 2: Dogs were studied on a single occasion during an infusion of lidocaine at 120 μg/kg/ min given after the loading dose (10 minutes). Measurements occurred after the loading dose and at 25 and 35 minutes. A blood sample for lidocaine concentration was taken at 70 minutes. Data were compared using a one-way ANOVA for phase 1, and between phase 1 and 2. Statistical analysis for phase 2 was performed using a paired r-test with a Bonferroni correction. A P value ± .05 was considered significant. Results—Phase 1: Plasma lidocaine concentrations achieved with 40, 120, and 200 μg of lidocaine/kg/min were 2.70, 5.27, and 7.17 μg/mL, respectively. A significant increase in heart rate (HR) (all concentrations), central venous pressure (CVP), mean pulmonary areterial pressure (PAP), and a decrease in stroke index (SI) (200 μg/kg/min) were observed. An increase in systemic vascular resistance (SVR) and mean PAP, and a decrease in SI also followed the loading dose given before the 200 μg/kg/min infusion. No other significant differences from the control measurements, during dextrose 5% infusion alone, were detected. Phase 2: Plasma lidocaine concentrations achieved were 5.35, 4.23, 4.23, and 5.60 μg/mL at 10, 25, 35, and 70 minutes, respectively. They were not significantly different from concentrations found in our healthy dogs at the same infusions. A significant but small increase in CVP compared with baseline was noted after the loading dose. There were no significant differences from baseline shown in all other cardiovascular data. There were no statistically significant differences in any measurements taken during the lidocaine infusion between the dogs in phase 1 and phase 2. Dogs with aortic stenosis tended to have a lower cardiac index than healthy dogs at baseline (88 v 121 mL/kg/min) and during lidocaine infusion (81 v 111 mL/kg/min). A small, statistically significant difference in systolic PAP was present at baseline. Conclusions—There does not appear to be any detrimental cardiovascular effects related to an infusion of lidocaine at 120 μg/kg/min during isoflurane anesthesia in healthy dogs or dogs with aortic stenosis. The technique used in this study resulted in therapeutic plasma concentrations of lidocaine. Clinical Relevance—Methods shown in the study can be used in clinical cases to achieve therapeutic lidocaine levels without significant cardiovascular depression during isoflurane anesthesia.     

Esophageal Replacement in the Dog by Microvascular Colon Transfer

An orthotopic colon graft based on the middle colic artery and vein was implanted with microvascular technique and a stapling instrument in five dogs. The grafts were successful in four dogs. A similar colon autograft was used to replace the entire thoracic esophagus in five dogs. The recipient vessels were the left carotid artery and left external jugular vein. Four of the grafts failed because of kinking and thrombosis of the arterial supply (2 dogs) or the venous outflow (2 dogs). One graft, which had a viable vascular supply, developed a severe leak at the colon-to-stomach anastomosis, and the dog was euthanatized on day 3. The recipient vascular pedicle was modified and used successfully to replace a portion of the cervical esophagus in three dogs. The grafts survived, the dogs could swallow liquids and semisolid food well, and, at necropsy after 4 weeks, the anastomotic sites were well healed. The graft sites contained essentially normal colon mucosa.     

Complications of Celiotomy Incisions in Horses

Complications of celiotomy incisions were evaluated retrospectively in 274 horses that survived at least 1 month after surgery, or died or were euthanatized within 1 month of surgery, as a direct result of these complications. Horses were divided into four groups; group A, a ventral median celiotomy for intestinal disease; group B, ventral median celiotomy for nonintestinal disease; group C, repair of an umbilical hernia; and group D, celiotomy in a region other than the midline. Specific incisional complications were peri-incisional edema, drainage, incisional abscess, suture sinus, and dehiscence. Incision-related complications occurred in 30% of the horses (group A, 40%; group B 18%; group C, 7%; and group D, 88%). Complications occurred more frequently in group D than group A ( P =.009), which were higher than in groups B and C ( P <.00001). Incisional hernia occurred in 28 of 256 (11%) horses that survived at least 4 months and were available for follow-up. Hernia formation was more common ( P <.00001) in horses that had other incisional complications (23 horses) than those without (5 horses). Serous or purulent incisional drainage, were more likely to be associated with hernia formation than was serosanguineous drainage or other incisional complications.     

Development of a Free Latissimus Dorsi Muscle Flap in Cats

Anatomic and experimental evaluation of the feline latissimus dorsi muscle was performed to assess its potential use as a free muscle flap. In the anatomic study, nonselective angiography of the subscapular artery was performed in nine heparinized feline cadavers. The muscle dimensions and vascular anatomy of the dissected latissimus dorsi muscle were recorded. In the experimental study four cats underwent heterotopic transplantation of a partial latissimus dorsi flap, and three cats underwent orthotopic transplantation of a complete latissimus dorsi flap. The mean length and width of the latissimus dorsi muscle was 19.0 and 5.4 cm, respectively. The dominant vascular pedicle was the thoracodorsal artery and vein. The average length and diameter of the thoracodorsal artery was 2.7 cm and 0.6 mm, respectively. Minor vascular pedicles were provided by branches of the intercostal arteries. Numerous choke anastomoses existed between the two pedicle systems. Viability of muscle flaps based on subjective evaluation, angiography, and histopathology, was 66% and 100% in the heterotopic and orthotopic studies, respectively. Flap failure seemed to be caused by both arterial and venous thrombosis. The latissimus dorsi muscle flap met criteria required for application in microvascular reconstruction. The vascular pattern was appropriate and consistent. Donor site morbidity was low, whereas surgical accessibility was high. The muscle satisfied the physical criteria of a free flap. Long-term anastomotic patency and flap viability was shown.     

Arthroscopic Approach and Intra-Articular Anatomy of the Plantar Pouch of the Equine Tarsocrural Joint

Arthroscopic examination of structures within the plantar pouch of the tarsocrural joint was accomplished via portals in both the plantaromedial and plantarolateral aspects of the joint. Flexion and extension of the tarsus while examining the joint through either portal allowed observation of the proximal and plantar aspects of the lateral and medial trochlear ridges, the trochlear groove, the caudal aspect of the distal tibia, and the deep digital flexor tendon (DDFT) in its sheath. From a plantarolateral portal, the plantar talocalcaneal ligament and the plantar aspect of the lateral malleolus could be observed. The caudal aspect of the medial malleolus could not be observed with flexion or extension of the joint from a plantaromedial portal, but in some horses, the caudal aspect of the lateral malleolus could be observed. The dorsolateral and dorsomedial aspects of the plantar pouch were best examined from a portal on the ipsilateral side of the joint. An instrument portal opposite either arthroscope portal allowed access to most regions of the joint except the abaxial surface of the trochlear ridge opposite the instrument.