Assessment of the Efficacy and Safety of a Novel, Low-Cost, Junctional Tourniquet in a Porcine Model of Hemorrhagic Shock.

INTRODUCTION: Commercially available junctional tourniquets (JTQs) have several drawbacks. We developed a low-cost, compact, easy to apply JTQ. The aim of this study was to assess the tourniquets' safety and efficacy in a swine model of controlled hemorrhage. MATERIALS AND METHODS: Five pigs were subjected to controlled bleeding of 35% of their blood volume. Subsequently, the JTQ was applied to the inguinal area for 180 minutes. Afterwards, the tourniquet was removed for additional 60 minutes of follow up. During the study, blood flow to both hind limbs and blood samples for tissue damage markers were repeatedly assessed. Following sacrifice, injury to both inguinal areas was evaluated microscopically and macroscopically. RESULTS: Angiography demonstrated complete occlusion of femoral artery flow, which was restored following removal of the tourniquet. No gross signs of tissue damage were noticed. Histological analysis revealed mild necrosis and infiltration of inflammatory cells. Blood tests showed a mild increase in potassium and lactic acid levels throughout the protocol. CONCLUSIONS: The tourniquet achieved effective arterial occlusion with minimal tissue damage, similar to reports of other JTQs. Subjected to further human trials, the tourniquet might be a suitable candidate for widespread frontline deployment because of its versatility, compactness, and affordable design.

Retrospective assessment of peripheral nerve block techniques used in cats undergoing hindlimb orthopaedic surgery.

OBJECTIVES: The aim of this study was to assess retrospectively the efficacy and complication rate of hindlimb peripheral nerve blocks (PNBs) in cats. METHODS: Clinical records of cats that received PNBs and underwent hindlimb orthopaedic surgery from February 2010 to October 2014 were examined. Type of PNB, type and dose of local anaesthetic used, end-expiratory fraction of isoflurane (FE'Iso) administered, additional intraoperative analgesia, incidence of hypotension, postoperative opioid requirement, postoperative contralateral limb paralysis and neurological complications at the 6 week re-examination were investigated. RESULTS: Eighty-nine records were retrieved but only 69 were analysed. Four combinations of PNBs were used: 34 lateral preiliac (LPI) approach to lumbar plexus (LP) associated with lumbar paravertebral approach to sciatic nerve (SN); 20 LPI-LP associated with the lateral approach to SN; three LPI-LP associated with gluteal approach to SN; 12 dorsal-paravertebral (DPV) approach to LP associated with lateral SN. Levobupivacaine was used for the majority of PNBs. The mean intraoperative FE'Iso was 1.15%; hypotension was documented in 55.1% of anaesthetics, while 31.8% of cats received fentanyl and/or ketamine intraoperatively. Postoperatively, 72.7% of cats received at least one dose of opioid, while five cats required further postoperative analgesia (ketamine constant rate infusion and/or gabapentin). No cats showed contralateral limb paralysis and neurological complications at the 6 week re-examination. No differences were found when comparing the different PNBs used. CONCLUSIONS AND RELEVANCE: PNBs contributed to perioperative anaesthesia/analgesia in cats undergoing hindlimb orthopaedic surgery. However, the clinical relevance of intraoperative hypotension needs further investigation.

Automated assessment of pain in rats using a voluntarily accessed static weight-bearing test.

UNLABELLED: The weight-bearing test is one method to assess pain in rodent animal models; however, the acceptance of this convenient method is limited by the low throughput data acquisition and necessity of confining the rodents to a small chamber. NEW METHODS: We developed novel data acquisition hardware and software, data analysis software, and a conditioning protocol for an automated high throughput static weight-bearing assessment of pain. With this device, the rats voluntarily enter the weighing chamber, precluding the necessity to restrain the animals and thereby removing the potential stress-induced confounds as well as operator selection bias during data collection. We name this device the Voluntarily Accessed Static Incapacitance Chamber (VASIC). RESULTS: Control rats subjected to the VASIC device provided hundreds of weight-bearing data points in a single behavioral assay. Chronic constriction injury (CCI) surgery and paw pad injection of complete Freund's adjuvant (CFA) or carrageenan in rats generated hundreds of weight-bearing data during a 30 minute recording session. Rats subjected to CCI, CFA, or carrageenan demonstrated the expected bias in weight distribution favoring the un-operated leg, and the analgesic effect of i.p. morphine was demonstrated. In comparison with existing methods, brief water restriction encouraged the rats to enter the weighing chamber to access water, and an infrared detector confirmed the rat position with feet properly positioned on the footplates, triggering data collection. This allowed hands-off measurement of weight distribution data reducing operator selection bias. CONCLUSION: The VASIC device should enhance the hands-free parallel collection of unbiased weight-bearing data in a high throughput manner, allowing further testing of this behavioral measure as an effective assessment of pain in rodents.

Contrast-enhanced ultrasound assessment of muscle blood perfusion of extremities that underwent crush injury: an animal experiment.

BACKGROUND: This research aimed to study the assessment of local muscle microcirculation perfusion of extremities that underwent crush injuries by using contrast-enhanced ultrasonography (CEUS). METHODS: A total of 28 New Zealand rabbits were anesthetized by using intramuscular pentobarbital sodium (30 mg/kg). A balloon cuff device was used to create crush injuries to the left hind leg of each rabbit with a force of 18.6 kPa. CEUS was performed at the 0.5th, 2nd, 6th,24th, and 72nd hour after the release of the crush pressure. Peak intensity (PI) of the crushed regions was compared with those of the uncrushed regions and before the creation of crush injury. Receiver operating characteristic analysis was used to determine the diagnostic value of PI for the crushed region. RESULTS: During the 72nd hour after the release of the crush pressure, 5 of the 28 rabbits died, and thus, their statistics were eliminated from the experiment. At different time points after the release of the crush pressure, the crushed regions in all 23 survivals showed quick and high enhancement, and their intensities were higher than those of the un crushed region in the arterial phase. The time-intensity curves of the crushed regions all appeared as rapid lift-gradual drop. PIs were obviously higher in the crushed regions than in the uncrushed regions and than those before the creation of crush injury ( p G 0.001). Receiver operating characteristic curves showed that extremity crush injury was diagnosed by using PI value. CONCLUSION: CEUS presents that the microcirculation perfusion of the crushed muscle increased obviously after the release of the crush pressure.PIs evaluated quantitatively the microcirculation perfusion changes. It may suggest a potential alternative for evaluating microcirculation abnormality of the muscle crush injury to the extremities.

Designing the ideal model for assessment of wound contamination after gunshot injuries: a comparative experimental study.

BACKGROUND: Modern high-velocity projectiles produce temporary cavities and can thus cause extensive tissue destruction along the bullet path. It is still unclear whether gelatin blocks, which are used as a well-accepted tissue simulant, allow the effects of projectiles to be adequately investigated and how these effects are influenced by caliber size. METHOD: Barium titanate particles were distributed throughout a test chamber for an assessment of wound contamination. We fired .22-caliber Magnum bullets first into gelatin blocks and then into porcine hind limbs placed behind the chamber. Two other types of bullets (.222-caliber bullets and 6.5 × 57 mm cartridges) were then shot into porcine hind limbs. Permanent and temporary wound cavities as well as the spatial distribution of barium titanate particles in relation to the bullet path were evaluated radiologically. RESULTS: A comparison of the gelatin blocks and hind limbs showed significant differences (p < 0.05) in the mean results for all parameters. There were significant differences between the bullets of different calibers in the depth to which barium titanate particles penetrated the porcine hind limbs. Almost no particles, however, were found at a penetration depth of 10 cm or more. By contrast, gas cavities were detected along the entire bullet path. CONCLUSION: Gelatin is only of limited value for evaluating the path of high-velocity projectiles and the contamination of wounds by exogenous particles. There is a direct relationship between the presence of gas cavities in the tissue along the bullet path and caliber size. These cavities, however, are only mildly contaminated by exogenous particles.

Accuracy of pressure plate kinetic asymmetry indices and their correlation with visual gait assessment scores in lame and nonlame dogs.

OBJECTIVE: To determine the accuracy of pressure plate kinetic asymmetry indices (ASIs) for diagnosis of unilateral hind limb lameness in dogs and their correlation with visual gait assessment (VGA) scores. ANIMALS: 9 healthy dogs and 16 dogs with previously diagnosed unilateral rupture of the cranial cruciate ligament and concurrent unilateral hind limb lameness. PROCEDURES: Dogs were walked over a pressure plate to determine paw contact area (PCA), peak vertical pressure (PVP), peak vertical force (PVF), and vertical impulse (VI) of both hind limbs. An ASI was calculated for each gait variable. Simultaneously, gait was assessed visually and scored by use of a numeric rating scale (0 to 10). The ASI of each variable was tested for its usefulness in discrimination between lame and nonlame dogs and for correlation with VGA scores. RESULTS: Sensitivity and specificity of ASIs to discriminate between lame and nonlame dogs were excellent for PVF, VI, and PCA; these values were substantially lower for ASI of PVP. Cutoff values to discriminate between lame and nonlame dogs were determined by use of ASIs for PVF, VI, and PCA; however, this could not be done for ASI of PVP. Correlations between ASIs of PVF, VI, and PCA and VGA scores were higher than correlation between the ASIs of PVP and VGA scores. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that ASIs of PVF and VI determined via analysis of pressure plate measurements were reliable indicators of clinical lameness in dogs, but the ASI of PVP was not. The ASI of PCA is an interesting new variable for assessment of limb loading symmetry.

Efficacy and cost-effectiveness of transdermal fentanyl patches for the relief of post-operative pain in dogs after anterior cruciate ligament and pelvic limb repair.

OBJECTIVES: To determine whether transdermal fentanyl patches provided cost-effective post-operative analgesia in dogs with pelvic limb injuries. STUDY DESIGN: Prospective, randomized, blinded clinical trial. ANIMALS: Twenty-four dogs undergoing repair of ruptured cranial cruciate ligaments or pelvic limb fractures. METHODS: Dogs were randomly assigned to one of two groups: those receiving transdermal fentanyl patches (group F) and those receiving injectable morphine for control of post-operative pain (group M). Patients in both treatment groups were monitored for adequacy of analgesia and alterations in physiological variables. Plasma fentanyl concentrations were measured in Group F. Rescue morphine was given if a dog was deemed uncomfortable. The time of first rescue morphine, the total amount, and number of doses of morphine administered over 72 hours was quantified and compared for each group. RESULTS: There was no significant treatment effect on any of the parameters, except for serum cortisol concentration, which was significantly lower overall in group F (p = 0.01). Pain scores peaked at 6 hours post-extubation and were higher than baseline from 2 to 20 hours post-extubation. Cortisol concentrations were the highest at time 0 (extubation) and were significantly higher than baseline until 2 hours post-extubation. Pain scores correlated with fentanyl plasma concentrations (p = 0.0001 and p = 0.01, respectively), but the correlation was low (r = 0.26 and r = 0.16, respectively). No correlation was found between serum cortisol concentrations and pain scores in either group. Fentanyl cost and total cost for pain management were considerably higher for group F. CONCLUSIONS: Fentanyl patches did not provide better analgesia or a reduced requirement for rescue opioid compared with intramuscular morphine. CLINICAL RELEVANCE: When considering overall costs to the client for comparable analgesic intervention, fentanyl patches increased rather than decreased cost during the first 24 hours post-operatively.

1H double-quantum-filtered MR imaging as a new tool for assessment of healing of the ruptured Achilles tendon.

1H double-quantum-filtered magnetic resonance imaging (DQF MRI) was applied to monitor the healing process of the Achilles tendons in rabbits after tenotomy. DQF MRI provides a new contrast, which is based on the non-zero average of the dipolar interaction caused by anisotropic motion of water molecules, determined mainly by their interaction with the ordered collagen fibers. Tissues are characterized by the dependence of their DQF signal on the DQ creation time, tau. With the use of DQF MRI, higher tissue contrast is obtained between tendon, bone, skin, and muscle. The tendons, which give weak signals in standard MRI techniques, are highlighted in the (1)H DQF image. The image changed dramatically during the healing process of the injured Achilles tendon. These changes matched the phases of the healing process. By using a tau-weighted contrast, the DQF images indicate the part of tendon that has not completely healed, even after the conventional MRI appeared normal. Magn Reson Med 42:884-889, 1999.