Clinical study evaluating the accuracy of injecting the distal tarsal joints in the horse.

BACKGROUND: Osteoarthritis (OA) of the centrodistal (CD) and tarsometatarsal (TMT) joints is a common cause of lameness in horses. Intra-articular diagnostic anaesthesia and/or therapeutic injection are relied upon to help diagnose and treat many horses with OA of these joints. OBJECTIVES: The objective of this study was to determine the accuracy of arthrocentesis of the CD and TMT joints using a sample population of equine surgeons and surgery residents. STUDY DESIGN: Randomised experimental study. METHODS: Six operators each injected four CD and four TMT joints in 12 sedated horses. The operators were randomly assigned to inject either the left CD and right TMT or the right CD and left TMT on four randomly assigned horses. The joints were injected with a 4 ml solution of contrast medium (2 ml), sterile saline (1.5 ml) and amikacin (0.5 ml). A minimum of two radiographs of each joint was obtained to evaluate the presence of contrast medium within the target joint. RESULTS: The TMT joint was successfully injected in 23/24 joints (96% accuracy). The CD joint was successfully injected in 10/24 joints (42% accuracy). Communication between the TMT and CD joints was visible in 26% of successful TMT injections. Communication between the CD and TMT joints was visible in 20% of successful CD injections. MAIN LIMITATIONS: Despite specific requests to do so, we were unable to standardise the injection technique across all operators. CONCLUSIONS: The accuracy of injecting the TMT and CD joints of sedated horses was 96 and 42%, respectively. The CD joint was frequently missed with contrast medium being placed in the periarticular tissues. These data support the clinical impression of the difficulty of injecting the CD joint and suggests that practitioners should utilise ancillary methods, such as radiographs, to ensure proper needle placement.

Effect of intravenous lidocaine administration on laminar inflammation in the black walnut extract model of laminitis.

REASONS FOR PERFORMING STUDY: Laminitis is a serious complication of horses suffering from sepsis/endotoxaemia-related events. Laminitis in horses and organ injury in human sepsis are both reported to involve inflammatory injury to the laminae/organs including early activation of endothelium and leucocytes leading to emigration of neutrophils into the tissue interstitium. In the black walnut extract (BWE) model, systemic inflammatory events coincide with marked increase in laminar mRNA concentrations of inflammatory genes including proinflammatory cytokines (i.e. IL-1beta, IL-6), COX-2, chemokines (i.e. IL-8) and endothelial adhesion molecules (i.e. ICAM-1 and E-selectin). In models of human sepsis, i.v. lidocaine has been reported to decrease leucocyte and endothelial activation, and the expression of proinflammatory cytokines and chemokines. OBJECTIVES: To evaluate the effect of i.v. lidocaine therapy on the inflammatory processes documented to occur in the BWE model of laminitis. METHODS: Twelve horses were administered BWE and treated immediately with either lidocaine (1.3 mg/kg bwt bolus, followed by 0.05 mg/kg bwt/min CRI, n=6) or saline (n=6) for 10 h. At 10 h post BWE administration, laminar samples were obtained under general anaesthesia for assessment of proinflammatory gene expression (using RT-qPCR) and leucocyte emigration (via CD13 immunohistochemistry). At 0, 3 and 10 h post BWE administration, skin samples were obtained for assessment of leucocyte emigration (via calprotectin immunohistochemistry). RESULTS: No significant differences between groups were noted for inflammatory gene mRNA concentrations (IL-1beta, IL-6, IL-8, COX-2) or for number of leucocytes present within the laminar interstitium or skin dermis. Increased (P<0.05) laminar E-selectin mRNA concentrations were present in the LD group (vs. SAL group). CONCLUSIONS: Continuous administration of i.v. lidocaine does not inhibit inflammatory events in either the laminae or skin in the horse administered black walnut extract. POTENTIAL RELEVANCE: This work questions the use of continuous i.v. administration of lidocaine as an effective anti-inflammatory therapy for systemic inflammation.

Black walnut extract-induced laminitis in horses is associated with heterogeneous dysfunction of the laminar microvasculature.

REASONS FOR PERFORMING STUDY: Equine laminitis purportedly involves haemodynamic dysfunction at the level of the laminar vasculature. However, to date, no studies have been performed characterising the function of laminar arteries and veins during the prodromal stages of equine laminitis. HYPOTHESIS: That the prodromal stages of laminitis are associated with contractile dysfunction of the equine laminar vasculature. OBJECTIVE: To assess contractile function of laminar arteries and veins to phenylephrine (PE) and 5-hydroxytryptamine (5-HT). METHODS: Horses were administered black walnut heartwood extract (BWHE) or water (control horses) via nasogastric intubation. After euthanasia, laminar vessels (100-800 microm internal diameter) were isolated and mounted on small vessel myographs to assess contractile function. RESULTS: Contractile responses to PE or 5-HT were identical in laminar arteries isolated from either control horses or those administered BWHE. In contrast, responses to PE or 5-HT were significantly reduced in laminar veins isolated from BWHE-administered horses when compared with laminar veins isolated from control horses. CONCLUSIONS AND POTENTIAL RELEVANCE: These results are consistent with the prodromal stages of laminitis being associated with selective dysfunction of laminar veins. Further studies are required to discern the precise nature of this dysfunction and its potential relevance to the pathogenesis of acute laminitis in the horse and possible therapeutic targets for treatment.

Equine thoracoscopy: normal anatomy and surgical technique.

Six normal, healthy horses age 3-10 years underwent left and right thoracoscopic examination using a rigid telescope. A minimum of 30 days was allowed between procedures. Horses were restrained in stocks and sedated with a continuous detomidine infusion. After surgical preparation of the hemithorax elected for surgery, and administration of local or regional anaesthesia of the surgery sites, thoracoscopy was completed during two 15 min pneumothorax periods. During the procedures, the thoracic structures were viewed using a 57 cm, 10 mm diameter, 30 degrees rigid telescope connected to a digital camcorder to allow computer capture of digital images. The telescope was inserted into the thoracic cavity via 3 different intercostal spaces. The 8th, 10th and 12th intercostal spaces were randomly selected and used among horses. The exploration of each hemithorax started from the dorsal-caudal quadrant continued toward the cranial thorax and was completed by observing the diaphragmatic and caudal pulmonary region. Collapsed lung, aorta, oesophagus and diaphragm were viewed readily in either hemithorax. On exploration of the right hemithorax, the azygos vein, thoracic duct and pulmonary veins were also identified. Horses tolerated thoracoscopy well. Signs of discomfort, such as increased respiratory rate, coughing and decreased level of sedation, were associated with lung collapse in one horse, with pneumothorax on 2 occasions, and when the thorax was approached through the 8th intercostal space. Surgery performed via the 8th intercostal space was hindered by the rigidity of the 8th and 9th ribs, and by the presence of a greater musculature, which did not allow easy cranial and caudal movements of the telescope.

Pleuropulmonary and cardiovascular consequences of thoracoscopy performed in healthy standing horses.

Six healthy, awake, and pharmacologically restrained mature horses were studied in order to define the changes in cardiopulmonary function during and after exploratory thoracoscopy and to determine the presence of postoperative complications occurring 48 hours after thoracoscopy. In a randomised 3 x 3 latin square design with 2 replications, 18 procedures were performed: 6 right (RTH) and 6 left thoracoscopies (LTH) and 6 sham procedures (STH). Prior to each procedure a physical examination and a bronchoalveolar lavage fluid analysis were performed. During thoracoscopy and sham protocols, horses were sedated with a continual drip of detomidine HCl and data were collected at 6 time intervals: T1 (baseline), T2 (10 min detomidine administration), T3 (first 15 min pneumothorax), T4 (5 min recovery from pneumothorax), T5 (second 15 min pneumothorax), and T6 (10 min recovery from the second pneumothorax and detomidine). An endoscopic thoracic examination was conducted during the 2 pneumothorax periods. An identical protocol was followed for sham procedures without surgery or pneumothorax. Data were analysed by ANOVA with time and surgical procedure as main factors. Physical examinations, thoracic radiography and ultrasound, CBC and bronchoalveolar lavage fluid analysis were performed 48 h after thoracoscopy. Heart rate, respiratory rate, and cardiac output decreased following detomidine administration. There was a trend for cardiac output to be lower during thoracoscopy. Mild systemic hypertension was associated with thoracoscopy although there was no effect on pulmonary arterial pressure. Total and pulmonary vascular resistances were increased following detomidine administration. Thoracoscopy caused a further increase in systemic and pulmonary vascular resistances especially during the second pneumothorax. Arterial O2 tension decreased following detomidine administration and was further decreased during the second pneumothorax period. PaO2 values were lower when thoracoscopy was performed on the left rather than the right hemithorax. No significant complications were found during the 48 h follow-up evaluation. A subclinical postoperative pneumothorax occurred in 2 horses, one of which had sustained a lung laceration by the trocar. Thoracoscopy performed in healthy, awake, and pharmacologically restrained horses did not have detrimental cardiopulmonary effects and did not cause postoperative complications within the first 48 h period.

Thoracoscopy in horses.

With the recent development of video-assisted thoracic surgery, visual inspection of the thoracic cavity has been used to provide a more accurate diagnosis and prognosis of thoracic diseases and to better manage these diseases. Equipment, techniques, and complications for standing thoracoscopy in horses are described.