Heterogeneity of intrapleural pressures during exercise.

We determined whether the caudodorsal region of the intrapleural space in exercising horses experiences larger pressure fluctuations than other regions and whether systematic phase-shifting of peak intrapleural pressures along the length of the thorax suggests the existence of locomotor-induced intrapleural pressure waves. We utilised percutaneous introducers and solid-state pressure-tip transducers implanted along the dorsal aspect of the thorax, mid-thorax or oesophagus to measure regional intrapleural pressures while 3 horses galloped on a flat treadmill at 13-14 m/s, then recorded pressures from the same catheters when horses exercised intensely (heart rate 170-190 beats/min) while swimming with no ground concussion. Pressure excursions in the caudodorsal region did not vary systematically from other regions during galloping or swimming, nor more than a few torr between different locations. During swimming, peak expiratory pressures were higher than during galloping (68-79 vs. 26-32 torr), and horses breathed explosively at frequencies 5 times slower than while galloping (28 vs. 120/min). During galloping, individual catheter locations registered locomotor concussion; however, this was variable and did not indicate a systematic pressure wave passing through the lung or intrapleural space.

Penile amputation and sheath ablation in the horse.

OBJECTIVE: To report a surgical technique for penile amputation and sheath ablation in horses. Study Design-Retrospective study. Animals or Sample Population-Twenty-five adult geldings of various breeds with conditions requiring penile amputation and sheath ablation. METHODS: The medical records of horses that had penile amputation and sheath ablation were reviewed. Briefly, the technique involved en bloc resection of the skin and subcutaneous tissues of the inner and outer lamina of the prepuce and penile shaft. Resection of the penile shaft, proximal to diseased segments, and spatulation of the urethral mucosa was followed by fixation of the penis to the ventral abdomen and closure of the peripreputial skin over the ventral aspect of the penis and creation of a new mucocutaneous junction at the urethral orifice. RESULTS: Mild to moderate postoperative hemorrhage occurred in all horses. Partial dehiscence of the mucocutaneous junction occurred in 8 horses; all healed by second intention. Postoperative pain lasting 24 to 48 hours occurred in 7 horses; 1 required epidural analgesia for pain relief. Long-term follow-up was available for 8 horses; none had any long-term complications. CLINICAL RELEVANCE: Partial amputation of the penis with pexy to the ventral abdomen and revision of the peripreputial skin can be used as an alternative to en bloc resection and penile retroversion for lesions involving the free part of the penis and the prepuce. It requires smaller incisions and results in less alteration to the normal appearance of the external genitalia than retroversion techniques, while still allowing the surgeon to remove extensive portions of the penis and extirpate the regional lymph nodes.

Use of sevoflurane for anesthetic management of horses during thoracotomy.

OBJECTIVE: To evaluate sevoflurane as an inhalation anesthetic for thoracotomy in horses. ANIMALS: 18 horses between 2 and 15 years old. PROCEDURE: 4 horses were used to develop surgical techniques and were euthanatized at the end of the procedure. The remaining 14 horses were selected, because they had an episode of bleeding from their lungs during strenuous exercise. General anesthesia was induced with xylazine (1.0 mg/kg of body weight, IV) followed by ketamine (2.0 mg/kg, IV). Anesthesia was maintained with sevoflurane in oxygen delivered via a circle anesthetic breathing circuit. Ventilation was controlled to maintain PaCO2 at approximately 45 mm Hg. Neuromuscular blocking drugs (succinylcholine or atracurium) were administered to eliminate spontaneous breathing efforts and to facilitate surgery. Cardiovascular performance was monitored and supported as indicated. RESULTS: 2 of the 14 horses not euthanatized died as a result of ventricular fibrillation. Mean (+/- SD) duration of anesthesia was 304.9 +/- 64.1 minutes for horses that survived and 216.7 +/- 85.5 minutes for horses that were euthanatized or died. Our subjective opinion was that sevoflurane afforded good control of anesthetic depth during induction, maintenance, and recovery. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of sevoflurane together with neuromuscular blocking drugs provides stable and easily controllable anesthetic management of horses for elective thoracotomy and cardiac manipulation.

Evaluation of samarium-153 for synovectomy in an osteochondral fragment-induced model of synovitis in horses.

OBJECTIVE: To determine the effects of intraarticular administration of Samarium-153 (153Sm) bound to hydroxyapatite microspheres (153SmM) on an osteochondral chip-induced synovitis. STUDY DESIGN: Sixty days after implantation of autogenous osteochondral fragments in the middle carpal and metacarpophalangeal joints, 153SmM was administered into 1 joint of each type. The contralateral joints were used as untreated controls. ANIMALS OR SAMPLE POPULATION: Fifteen horses without preexisting joint disease were randomly divided into 2 groups (7 in the carpal group, 8 in the metacarpophalangeal group). METHODS: Horses had osteochondral fragments that were harvested from the lateral ridge of the trochlea of the talus and implanted bilaterally into a middle carpal joint and a metacarpophalangeal joint; the opposite joint type served as a control. Sixty days later, 10 to 15 mCi of 153SmM (20 to 50 microm diam) was injected into the fragment-implanted joints. Three horses were treated with nonradioactive hydroxyapatite fragments. Horses were examined clinically until they were killed 14 or 30 days later. Control and treated joints were examined grossly and microscopically to determine the effects of 153SmM on synovial membrane and cartilage. RESULTS: Intraarticular 153SmM caused a transient flare with lameness, effusion, and edema for 48 to 72 hours. Implanted osteochondral chips induced a synovitis characterized by variable degrees of joint damage and synovial infiltrate. Use of 153SmM resulted in synovectomy of variable depth and extent. CONCLUSIONS: Intraarticular 153SmM may be a useful method for synovectomy of inflamed synovial membrane. CLINICAL RELEVANCE: With further testing, radioactive pharmaceuticals might become useful clinical treatments for persistent synovitis not responsive to conventional techniques.

Samarium 153-labeled hydroxyapatite microspheres for radiation synovectomy in the horse: a study of the biokinetics, dosimetry, clinical, and morphologic response in normal metacarpophalangeal and metatarsophalangeal joints.

OBJECTIVE: To determine the effects of Samarium-153 bound to hydroxyapatite microspheres (153SmM) when injected into the metacarpophalangeal and metatarsophalangeal joints of horses. STUDY DESIGN: - Horses were injected with 153SmM in metacarpophalangeal and metatarsophalangeal joints with the diagonal contralateral joints used as untreated controls. ANIMALS OR SAMPLE POPULATION: Twelve adult horses without pre-existing disease involving the metacarpo/metatarsophalangeal joints. METHODS: Horses were divided into three groups: high-dose Samarium-153 (12.5 to 17.0 millicurie [mCi]), intermediate dose (6.5 to 12.0 mCi), and low dose (3.5 to 6.0 mCi). Horses were examined daily for 7 days postinjection for clinical abnormalities, lameness, and surface and systemic radiation levels. One horse from each group was euthanatized at 14, 30, and 60 days postinjection and the effects of the 153SmM examined microscopically in the cartilage and synovial membrane. RESULTS: Intraarticular(153)SmM caused inflammation characterized by lameness, effusion, and regional edema for 48 to 72 hours. Minimal levels of active 153SmM were identified in the blood or urine and were well below the maximal tolerance of 1 mCi. Microscopically the radiation caused no effects on the articular cartilage. The synovectomy created was good but not ideal in that some areas did have necrosis into the subintimal regions and a few islands of intact intimal cells persisted. CONCLUSIONS: The use of 153SmM is an effective means of targeting the synovial intimal cells with minimal extrasynovial leakage of radiation. CLINICAL RELEVANCE: The metacarpophalangeal and metatarsophalangeal joints of the horse can be safely treated with 153SmM without damage to the cartilage or significant extracapsular leakage.

Surgical repair of a thoracic meningocele in a foal.

A 6 week old American Paint filly was admitted for evaluation of a dorsal thoracic mass suspected to be a meningocele. The diagnosis was confirmed by plain and contrast enhanced computed tomography. Surgical repair was performed by dissection of the base of the meningocele followed by ligation. No postoperative complications occurred. Contrast enhanced computed tomography was useful to confirm the diagnosis of meningocele and rule out a meningomyelocele.

Persistent frenulum of the epiglottis in four foals.

OBJECTIVE: To report the clinical signs and management of 4 foals with persistent frenulum of the epiglottis. STUDY DESIGN: Case report. ANIMALS: Four newborn foals. METHODS: Foals were admitted with a complaint of oronasal reflux after nursing. Variable systemic signs of aspiration pneumonia were evident. Nasal endoscopy confirmed persistent dorsal displacement of the soft palate. Persistent frenulum of the epiglottis, confirmed by oral endoscopic examination, was transected. RESULTS: After surgery, all foals had the epiglottis positioned normally, dorsal to the soft palate. Clinical signs of oronasal reflux resolved by the second nursing attempt in 3 foals, whereas this was difficult to assess in one foal that was nursed intermittently because of the mares behavior. This foal died 2 days later. The other 3 foals have had normal epiglottic function for 2-4 years. CONCLUSIONS: Persistent frenulum of the epiglottis should be considered in foals with oronasal reflux from birth. With appropriate medical and surgical management the prognosis for resolution should be good.

Evaluation of peritoneal fluid pH, glucose concentration, and lactate dehydrogenase activity for detection of septic peritonitis in horses.

OBJECTIVE: To determine whether peritoneal fluid pH, glucose concentration, and lactate dehydrogenase activity can be used to differentiate horses with septic peritonitis from those with nonseptic peritonitis. DESIGN: Prospective study. ANIMALS: 46 horses, including 10 healthy horses, 15 horses with septic peritonitis, and 21 horses with nonseptic peritonitis. PROCEDURE: Peritoneal fluid and blood samples were analyzed for pH, glucose concentration, and lactate dehydrogenase activity. Complete blood cell counts were performed, and peritoneal fluid samples were submitted for bacterial culture. RESULTS: Horses with septic peritonitis had significantly lower peritoneal fluid pH and glucose concentrations than horses with nonseptic peritonitis and healthy horses. Compared with other tests, serum-to-peritoneal fluid glucose concentration differences > 50 mg/dl had the highest diagnostic use for detection of septic peritonitis. Peritoneal fluid pH < 7.3, glucose concentration < 30 mg/dl, and fibrinogen concentration > 200 mg/dl were also highly indicative of septic peritonitis. CLINICAL IMPLICATIONS: Peritoneal fluid pH and glucose concentration can be used to assist in the identification of horses with septic peritonitis. These measurements can provide an early indication of sepsis, especially if cytologic evaluation of peritoneal fluid is unavailable or results are equivocal and peritoneal fluid bacterial culture results are pending.

Cardiac output measurements using sonomicrometer crystals on the left ventricle at rest and exercise.

Eight horses were fitted surgically with 8 ultrasonic sonomicrometer crystals each attached to their left ventricular pericardia and a left atrial catheter. Three horses returned to treadmill performance with a maximum rate of oxygen consumption similar to their presurgical values. These horses were evaluated to determine how well sonomicrometer estimates of cardiac output agreed with those obtained by a steady-state method, the Fick principle. Variance between the 2 was similar to the coefficient of variation (approximately 12.5%) of the Fick estimates. We conclude that left ventricular sonomicrometer measurements in horses appear to give a reasonable estimate of ventricular dimensions and can, therefore, be used potentially to evaluate such variables as diastolic flow.

A modified teniotomy technique for facilitated removal of descending colon enteroliths in horses.

OBJECTIVE: To describe a method for facilitating movement of enteroliths obstructing the proximal portion of the descending colon. STUDY DESIGN: Prospective report. SAMPLE POPULATION: 15 horses. METHODS: A seromuscular incision through the antimesenteric taenia of the proximal portion of the descending colon was used to facilitate movement of enteroliths. RESULTS: Teniotomy allowed proximal descending colon enteroliths located within the abdomen or close to the abdominal wall to be advanced 4 to 15 cm in an aboral direction so that they could be exteriorized for safe removal. CONCLUSIONS AND CLINICAL RELEVANCE: Teniotomy is a feasible method for mobilizing enteroliths in the proximal descending colon in locations that cannot otherwise be exteriorized.

Nasal septoplasty for correction of septal deviation in a foal.

OBJECTIVE: This article reports an alternative to septal resection in nasal septal deviations involving the rostral 7 to 10 cm of the nasal septum. STUDY DESIGN: Case report. SAMPLE POPULATION: One client-owned foal. METHODS: A nasal approach with mucosal elevation was used to gain access to the cartilaginous portion of the nasal septum. Once exposed, a series of parasagittal incisions in the cartilage allowed the septum to be repositioned while providing some intrinsic stabilization. RESULTS: The nasal approach provided good access to the rostral 7 cm of the nasal septum. The technique resulted in minimal hemorrhage from the site. Bleeding was reduced with the use of ephedrine to vasoconstrict the mucosal vessels, and primary closure of the mucosa. CONCLUSIONS: Use of an intrinsically stabilized septoplasty should be considered as a means of decreasing the airway obstruction caused by nasal septal deviation in foals while allowing for normal development of facial contour.

Jejunal microvasculature of the llama and alpaca.

The vasculature of the jejunum was studied in 6 llamas and 1 alpaca, using a combination of microangiography, standard light microscopy, and vascular cast imaging. The casts were examined by use of scanning electron microscopy and low-power dissecting microscopy. After administration of 40,000 IU of heparin, all animals were euthanatized by administration of an overdose of sodium pentobarbital. Three sections of jejunum and their respective arcuate vessels were isolated from each animal. One section was immediately placed in formalin for later H&E staining. The second and third sections were placed in warm saline solution, and the vasculature was flushed free of all blood by repeated infusions of the solution. Once flushed of all blood, one section was infused with a radio-opaque medium and subsequently evaluated by microangiography, and the remaining section was perfused with a methylmethacrylate polymer for creation of vascular casts. The arcuate vessels branched into extensive primary and secondary arcades prior to giving rise to the marginal rete. Muscular arteries and small veins left the marginal rete and penetrated the tunica serosa and tunica muscularis to provide nutrients or drain the mesenteric angle, respectively, or entered into the circumferential submucosal network. The primary penetrating vessels in the submucosa formed an extensive submucosal plexus that supplied the tunica serosa, tunica muscularis, and tunica mucosa. The primary penetrating vessels anastomosed with vessels from oral and aboral sections and with their counterparts from the opposite side at the antimesenteric border.(ABSTRACT TRUNCATED AT 250 WORDS)

Resolution of a left ureteral stone using electrohydraulic lithotripsy in a thoroughbred colt.

A 3-year-old Thoroughbred colt was presented for evaluation of azotemia and anorexia. Physical examination revealed a ureterolith in the left ureter, approximately 10 cm from the bladder, which was thought to obstruct urine flow by approximately 90% when viewed cystoscopically. Ultrasonographic examination of both kidneys revealed indistinct corticomedullary junctions, and the right kidney was more hyperechoic. A percutaneous biopsy of the right kidney revealed chronic interstitial nephritis with marked interstitial medullary fibrosis. Medical therapy consisting of IV fluids, sodium chloride PO, and ammonium chloride PO was initiated. Ureteroscopic electrohydraulic lithotripsy via a perineal urethrostomy was used to successfully remove the stone. Klebsiella oxytoca, which responded to oral enrofloxacin therapy, was cultured from the urine after surgery. Azotemia resolved and the horse resumed training.

Laparoscopic anatomy of the llama abdomen.

Paralumbar laparoscopy was performed, caudal to the last rib, in seven llamas. All animals were anesthetized, instrumented, and placed in sternal recumbency. Systematic exploration was performed in six donated llamas dividing the abdomen into right and left, cranial and caudal quadrants. The main structures of diagnostic significance that could be observed from the right side were the parietal and visceral surface of the liver, diaphragm, first compartment of the stomach (C1), caudal aspect of the third compartment of the stomach (C3), pancreas, kidney duodenum, jejunum, and ascending colon. From the left side C1, varying lengths of jejunum, ileum, ascending colon, and spiral colon were identified. From both approaches the bladder, and in females the uterus and ovaries could be observed. All animals were necropsied immediately following the procedure. Gross examination of the abdominal viscera in the did not yield any abnormalities that had been missed by laparoscopic evaluation. Using a left paralumbar approach, one clinical case presenting with signs of acute abdominal discomfort was evaluated. A diagnosis was made of diffuse enteritis that was confirmed at necropsy. Because of the distensible nature of the South American camelid (SAC) abdominal wall, the small size of the abdominal viscera, and the freely mobile nature of most portions of the gastrointestinal tract a thorough examination was possible in all animals.

Use of autogenous cancellous bone grafting in the treatment of septic navicular bursitis and distal sesamoid osteomyelitis in horses.

Six horses with septic navicular bursitis or distal sesamoid osteomyelitis were treated by means of surgical debridement and lavage, followed by packing of the wound created in the bottom of the foot with an autogenous cancellous bone graft. Two horses were euthanatized, one 18 months after surgery because of complications in the contralateral support limb, and one 68 days after surgery because of continuing severe lameness. Four horses were alive 9, 16, 21, and 42 months after surgery. One horse was used as a broodmare and did not have observable lameness. Two horses were being ridden. The remaining horse had improved markedly, but was still lame. It appears that cancellous bone grafts can be used successfully, in conjunction with debridement and antimicrobial treatment, in horses with septic navicular bursitis and distal sesamoid osteomyelitis.

Abdominal radiography for diagnosis of enterolithiasis in horses: 141 cases (1990-1992).

Medical records of 245 horses that had been evaluated by use of abdominal radiography between January 1990 and December 1992 were reviewed. One hundred forty-one horses subsequently had a postmortem examination or surgical exploration performed for definitive lesion diagnosis. The signalment, diagnosis, site, and number of enteroliths were obtained from the medical records. Radiographs were evaluated individually by 3 reviewers for the presence of enteroliths, preferred diagnostic view, evidence of large colon tympany, and film quality. Of the 141 cases reviewed, 66.7% (94/141) had confirmed enterolithiasis. Enteroliths were identified in the right dorsal colon of 59 horses, in the transverse colon of 28, in the small colon of 24, and in the ventral colon of 1 (enteroliths were detected in multiple sites in 12 horses). For the 3 reviewers, mean sensitivity was 76.9% and specificity was 94.4%. Mean positive-predictive value was 96.4%, and negative-predictive value was 67.5%. Cases involving only large colon enteroliths were correctly diagnosed 83.2% of the time, compared with 41.6% of the time for cases involving small colon enteroliths. Enteroliths were evident in 54.8% of the horses with radiographic signs of large colon distention. Fifteen horses had enteroliths in the small colon, 4 in the transverse colon, and 4 in the dorsal colon. Radiographic quality was evaluated and scored as adequate (0), underexposed (-1), overexposed (1), or incomplete. Mean score was -0.5, and there were 21 (14.9%) incomplete studies.(ABSTRACT TRUNCATED AT 250 WORDS)