Efficacy of lumbosacral and sacrococcygeal epidural ropivacaine in dogs undergoing surgery for perineal hernia.

Epidural anesthesia is commonly administered as part of balanced anesthesia for perioperative analgesia. The main goal of this randomized clinical trial was to compare the efficacy of two epidural approaches in dogs undergoing surgery for a perineal hernia. A secondary aim was to compare motor blockade. Intact ASA 1 and 2 male dogs, weighing ≤25 kg with no previous surgery for perineal hernia were enrolled. After premedication with IM acepromazine 0.02 mg/kg and butorphanol 0.3 mg/kg, general anesthesia was induced with propofol and maintained with sevoflurane in oxygen. Dogs were randomly allocated to receive either a lumbosacral (LS, n = 30) or a sacrococcygeal (SC, n = 26) epidural injection with ropivacaine 1% (0.2 mL/kg) under computed tomography guidance. Successful analgesia was defined as no need of intraoperative rescue analgesia (fentanyl 3 µg/kg IV). Clinical failure was defined as the need of more than two boluses of fentanyl/h each dog received meloxicam 0.2 mg/kg IV at the end of the surgery. The Glasgow Composite Pain Scale short form (GCPS-SF), tactile sensitivity, pressure pain thresholds and motor blockade were assessed at 4, 6, 8, and 24 h after the epidural injection. Methadone (0.2 mg/kg, IV) was administered if the GCPS-SF was ≥6/24 points. Differences between groups were analyzed with the Mann-Whitney U test, Student's t-test or Fisher's Exact test, as appropriate. Success rate was assessed for non-inferiority between groups. The non-inferiority margin was set at -10%. Epidural analgesia was successful in 24 dogs in group LS and 17 dogs in group SC (p = 0.243), resulting in success rates of 80 and 65% in LS and SC groups, respectively. The non-inferiority of group SC versus group LS was confirmed. Clinical failure was recorded in two dogs in group LS and one dog in group SC. No significant differences between groups were detected in the GCPS-SF score, tactile sensitivity, pressure pain thresholds, need of post-operative methadone, or motor blockade. Both epidural techniques are valuable analgesic options for perineal hernia repair in dogs.

A novel soft cardiac assist device based on a dielectric elastomer augmented aorta: An in vivo study.

Although heart transplant is the preferred solution for patients suffering from heart failures, cardiac assist devices remain key substitute therapies. Among them, aortic augmentation using dielectric elastomer actuators (DEAs) might be an alternative technological application for the future. The electrically driven actuator does not require bulky pneumatic elements (such as conventional intra-aortic balloon pumps) and conforms tightly to the aorta thanks to the manufacturing method presented here. In this study, the proposed DEA-based device replaces a section of the aorta and acts as a counterpulsation device. The feasibility and validation of in vivo implantation of the device into the descending aorta in a porcine model, and the level of support provided to the heart are investigated. Additionally, the influence of the activation profile and delay compared to the start of systole is studied. We demonstrate that an activation of the DEA just before the start of systole (30 ms at 100 bpm) and deactivation just after the start of diastole (0-30 ms) leads to an optimal assistance of the heart with a maximum energy provided by the DEA. The end-diastolic and left ventricular pressures were lowered by up to 5% and 1%, respectively, compared to baseline. The early diastolic pressure was augmented in average by up to 2%.

Anatomical Variations of the Common Carotid Arteries and Neck Structures of the New Zealand White Rabbit and Their Implications for the Development of Preclinical Extracranial Aneurysm Models.

BACKGROUND: Rabbit models involving neck arteries are of growing importance for the development of preclinical aneurysm models. An optimal understanding of the anatomy is primordial to allow the conception of models while minimizing mortality and morbidity. The aim of this study is to give reliable anatomical landmarks to allow a standardized approach to the neck vessels. METHODS: We performed a necropsy on nine specimens from ongoing experimental studies. We measured the distance between the origins of the right and left common carotid artery (rCCA/lCCA) and between the rCCA and the manubrium sterni (MS). The structures at risk were described. RESULTS: Female New Zealand White rabbits (NZWR) weighing 3.7 ± 0.3 kg and aged 25 ± 5 weeks were included. The rCCA origin was located 9.6 ± 1.2 mm laterally and 10.1 ± 3.3 mm caudally to the MS. In all specimens, the lCCA originated from the aortic arch, together with the brachiocephalic trunk (BCT), and 6.2 ± 3.1 mm proximally to the rCCA origin. The external and internal jugular veins, trachea and laryngeal nerve were the main structures at risk. CONCLUSIONS: The data help to localize both CCAs and their origin to guide surgical approaches with the manubrium sterni as a main landmark. Special attention has to be paid to the trachea, jugular veins and laryngeal nerves.

Usefulness and Reliability of the Bispectral Index during Balanced Anesthesia for Neurovascular Surgery in New Zealand White Rabbits.

Few data about the electroencephalogram and its calculated indices, such as the bispectral index (BIS), have been reported in rabbits. We aimed to evaluate whether a clinically stable anesthesia was mirrored by consistent and stable BIS values and to investigate the effects of modified cerebral blood supply, due to bilateral carotid clamping and re-opening, on BIS values. We also investigated the effects of fentanyl, as an antinociceptive drug, on the BIS. Sixty-eight rabbits undergoing general anesthesia for surgical creation of carotid bifurcation aneurysms were enrolled. The BIS values were recorded at nine selected time points (TPs) during each procedure and before and after fentanyl administration. The BIS values over time were compared with two-way repeated-measures analysis of variance followed by Tukey test, while the Wilcoxon signed rank test was performed to compare values at clamping and re-opening of the carotids as well as before and after fentanyl administration. The BIS values were significantly lower during anesthesia than at the end of anesthesia and at tracheal extubation; no significant differences were found among other TPs. Adequate depth of anesthesia was mirrored by consistent BIS values among rabbits, and alteration of cerebral blood supply did not modify BIS values, except once. Following fentanyl, BIS values did not change in a clinically relevant way.

Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model.

Assessment of native cardiac output during extracorporeal circulation is challenging. We assessed a modified Fick principle under conditions such as dead space and shunt in 13 anesthetized swine undergoing centrally cannulated veno-arterial extracorporeal membrane oxygenation (V-A ECMO, 308 measurement periods) therapy. We assumed that the ratio of carbon dioxide elimination (V̇co2) or oxygen uptake (V̇o2) between the membrane and native lung corresponds to the ratio of respective blood flows. Unequal ventilation/perfusion (V̇/Q̇) ratios were corrected towards unity. Pulmonary blood flow was calculated and compared to an ultrasonic flow probe on the pulmonary artery with a bias of 99 mL/min (limits of agreement -542 to 741 mL/min) with blood content V̇o2 and no-shunt, no-dead space conditions, which showed good trending ability (least significant change from 82 to 129 mL). Shunt conditions led to underestimation of native pulmonary blood flow (bias -395, limits of agreement -1,290 to 500 mL/min). Bias and trending further depended on the gas (O2, CO2) and measurement approach (blood content vs. gas phase). Measurements in the gas phase increased the bias (253 [LoA -1,357 to 1,863 mL/min] for expired V̇o2 bias 482 [LoA -760 to 1,724 mL/min] for expired V̇co2) and could be improved by correction of V̇/Q̇ inequalities. Our results show that common assumptions of the Fick principle in two competing circulations give results with adequate accuracy and may offer a clinically applicable tool. Precision depends on specific conditions. This highlights the complexity of gas exchange in membrane lungs and may further deepen the understanding of V-A ECMO.

Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study.

OBJECTIVE: To investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration. STUDY DESIGN: A randomized, controlled, blinded, clinical trial. ANIMALS: A total of 28 client-owned dogs. METHODS: Dogs were premedicated with medetomidine (0.125 mg m-2) and butorphanol (0.2 mg kg-1) (group MB; n = 14), or medetomidine (0.25 mg m-2), butorphanol (0.2 mg kg-1) and vatinoxan (5 mg m-2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg-1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg-1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (fR), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe'Sevo) and carbon dioxide (Pe'CO2) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations. RESULTS: At the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute-1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in fR, Pe'CO2, Fe'Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: In group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups.

Implications of Wound Healing on Subcutaneous Photovoltaic Energy Harvesting.

OBJECTIVE: Cardiac pacemakers must be regularly replaced due to depleted batteries. A possible alternative is proposed by subcutaneous photovoltaic energy harvesting. The body's reaction to an implant can cause device encapsulation. Potential changes in spectral light transmission of skin can influence the performance of subcutaneous photovoltaic cells and has not yet been studied in large animal studies. METHODS: Subcutaneous implants measuring changes in the light reaching the implant were developed. Three pigs received those implants and were analyzed for seven weeks. Spectral measurements with known irradiation were performed to identify possible changes in the transparency of the tissues above the implant during the wound healing process. A histological analysis at the end of the trial investigated the skin tissue above the subcutaneous photovoltaic implants. RESULTS: The implants measured decreasing light intensity and shifts in the light's spectrum during the initial wound healing phase. In a later stage of tissue recovery, the implants measured a generally reduced light intensity compared to the healthy tissue after implantation. The spectral distribution of the measured light at the end of the trial was similar to the first measurements. The histological analysis showed subcutaneous granulation tissue formation for all devices. CONCLUSION: The varying reduction of light intensity reaching the implants means that safety margins must be sufficiently high to ensure the power. At the end of the wound healing process, the spectral distribution of the light reaching the implant is similar to healthy tissue. SIGNIFICANCE: Optimizations of spectral sensitivity of photovoltaic cells are possible.

Aspirin treatment prevents inflammation in experimental bifurcation aneurysms in New Zealand White rabbits.

BACKGROUND: Aneurysm wall degeneration is linked to growth and rupture. To address the effect of aspirin (ASA) on aneurysm formation under various wall conditions, this issue was analyzed in a novel rabbit bifurcation model. METHODS: Bifurcation aneurysms created in 45 New Zealand White rabbits were randomized to vital (n=15), decellularized (n=13), or elastase-degraded (n=17) wall groups; each group was assigned to a study arm with or without ASA. At follow-up 28 days later, aneurysms were evaluated for patency, growth, and wall inflammation at macroscopic and histological levels. RESULTS: 36 rabbits survived to follow-up at the end of the trial. None of the aneurysms had ruptured. Patency was visualized in all aneurysms by intraoperative fluorescence angiography and confirmed in 33 (92%) of 36 aneurysms by MRI/MRA. Aneurysm size was significantly increased in the vital (without ASA) and elastase-degraded (with and without ASA) groups. Aneurysm thrombosis was considered complete in three (50%) of six decellularized aneurysms without ASA by MRI/MRA. Locoregional inflammation of the aneurysm complex was significantly reduced in histological analysis among all groups treated with ASA. CONCLUSION: ASA intake prevented inflammation of both the periadventitial tissue and aneurysm wall, irrespective of initial wall condition. Although ASA prevented significant growth in aneurysms with vital walls, this preventive effect did not have an important role in elastase-degraded pouches. In possible translation to the clinical situation, ASA might exert a potential preventive effect during early phases of aneurysm formation in patients with healthy vessels but not in those with highly degenerative aneurysm walls.

Persistent hyperammonia and altered concentrations of urea cycle metabolites in a 5-day swine experiment of sepsis.

We measured plasma and cerebrospinal fluid (CSF) metabolite concentrations in a 5-day porcine sepsis model of fecal peritonitis. The objectives were: (i) to verify whether the expected pathways that had emerged in previous studies pertain only to the early inflammatory response or persist for the subsequent days; (ii) to identify metabolic derangements that arise later; (iii) to verify whether CSF metabolite concentrations were altered and if these alterations were similar to those in the blood or delayed. We observed an early response to inflammation and cytokine storms with alterations in lipid and glucose metabolism. The arginine/asymmetric dimethylarginine (ADMA) and phenylalanine/tyrosine balances changed 24 h after resuscitation in plasma, and later in CSF. There was a rise in ammonia concentration, with altered concentrations of metabolites in the urea cycle. Whether persistent derangement of these pathways have a role not only on short-term outcomes but also on longer-term comorbidities, such as septic encephalopathy, should be addressed in further studies.

Creation of Two Saccular Elastase-Digested Aneurysms with Different Hemodynamics in One Rabbit.

Preclinical animal models with hemodynamic, morphologic, and histologic characteristics close to human intracranial aneurysms play a key role in the understanding of the pathophysiological processes and the development and testing of new therapeutic strategies. This study aims to describe a new rabbit aneurysm model that allows the creation of two elastase-digested saccular aneurysms with different hemodynamic conditions within the same animal. Five female New Zealand white rabbits with a mean weight of 4.0 (± 0.3) kg and mean age of 25 (±5) weeks underwent microsurgical stump and bifurcation aneurysm creation. One aneurysm (stump) was created by right common carotid artery (CCA) exposure at its origin at the brachiocephalic trunk. A temporary clip was applied at the CCA origin and another, 2 cm above. This segment was treated with a local injection of 100 U of elastase for 20 min. A second aneurysm (bifurcation) was created by suturing an elastase-treated arterial pouch into the end-to-side anastomosis of the right CCA to left CCA. Patency was controlled by fluorescence angiography immediately after creation. The average duration of surgery was 221 min. The creation of two aneurysms in the same animal was successful in all rabbits without complication. All aneurysms were patent immediately after surgery except for one bifurcation aneurysm, which showed an extreme tissue reaction due to elastase incubation and an immediate intraluminal thrombosis. No mortality was observed during surgery and up to one-month follow-up. Morbidity was limited to a transient vestibular syndrome (one rabbit), which recovered spontaneously within one day. Demonstrated here for the first time is the feasibility of creating a two-aneurysm rabbit model with stump and bifurcation hemodynamic characteristics and highly degenerated wall conditions. This model allows the study of the natural course and potential treatment strategies on the basis of aneurysm biology under different flow conditions.

Tocilizumab Reduces Vasospasms, Neuronal Cell Death, and Microclot Formation in a Rabbit Model of Subarachnoid Hemorrhage.

Early brain injury (EBI), delayed cerebral vasospasm (DCVS), and delayed cerebral ischemia (DCI) are common complications of subarachnoid hemorrhage (SAH). Inflammatory processes in the cerebrospinal fluid (CSF) are one of the causes for such complications. Our aim to study the effects of an IL-6 receptor antagonist (Tocilizumab) examines the occurrence of DCVS, neuronal cell death, and microclot formation in an acute SAH rabbit model. Twenty-nine New Zealand white rabbits were randomized into one of three groups as the SAH, SAH + Tocilizumab, and sham groups. In SAH groups, hemorrhage was induced by extracranial-intracranial arterial blood shunting from the subclavian artery into the cisterna magna under intracranial pressure (ICP) monitoring. In the second group, Tocilizumab was given once intravenously 1 h after SAH induction. Digital subtraction angiography was performed, and CSF and blood were sampled before and after (day 3) SAH induction. IL-6 plasma and CSF levels were measured. TUNEL, FJB, NeuN, and caspase-3 immunostaining were used to assess cell apoptosis, neurodegeneration, and neuronal cell death, respectively. Microclot formation was detected by fibrinogen immunostaining. Between baseline and follow-up, there was a significant reduction of angiographic DCVS (p < 0.0001) in the Tocilizumab compared with the SAH group. Tocilizumab treatment resulted in decreased neuronal cell death in the hippocampus (p = 0.006), basal cortex (p = 0.001), and decreased microclot formation (p = 0.02). Tocilizumab reduced DCVS, neuronal cell death, and microclot formation in a rabbit SAH model, and could be a potential treatment to prevent DCVS and DCI in SAH patients.

Comparison of the effects of methadone and butorphanol combined with acepromazine for canine gastroduodenoscopy.

OBJECTIVE: To evaluate the feasibility of gastroduodenoscopy in dogs premedicated with acepromazine in combination with butorphanol or methadone. STUDY DESIGN: Prospective, randomized, double-blinded clinical trial. ANIMALS: A group of 40 client-owned dogs. METHODS: Dogs were randomly allocated to one of two groups and give intramuscular acepromazine 0.02 mg kg-1 combined with either butorphanol 0.3 mg kg-1 (group ACEBUT) or methadone 0.2 mg kg-1 (group ACEMET). General anaesthesia was induced with propofol and ketamine and maintained with sevoflurane (2.3%) in oxygen. Cardiopulmonary variables were recorded at 5 minute intervals during anaesthesia. Feasibility of the entire gastroduodenoscopy was evaluated with a visual analogue scale (VAS) from 0 (best) to 100 (worst) (primary outcome of the study). Lower oesophageal sphincter dilatation and duodenal intubation were scored. Pylorus diameter was measured with standard endoscopic inflatable balloons. Overall cardiovascular stability was assessed during anaesthesia, using a VAS (0-100), as was the presence of fluid in the oesophagus, regurgitation, need for mechanical ventilation, and intraoperative and postoperative rescue analgesia (secondary outcomes of the study). Differences between treatments were analysed with Mann-Whitney U, Student t test, Fisher exact test or mixed model analysis of variance as appropriate. Subsequently, feasibility VAS of the gastroduodenoscopy was assessed for noninferiority between groups. The noninferiority margin was set as -10. RESULTS: All gastroduodenoscopies were successfully completed in both groups using an endoscope tip diameter of 12.8 mm in all but one dog. Feasibility of gastroduodenoscopy was evaluated as 2.9 ± 5.6 in group ACEBUT and 5.1 ± 5.8 in group ACEMET. No significant differences between groups were detected in any measured or assessed variables, and noninferiority was confirmed. CONCLUSION AND CLINICAL RELEVANCE: In our study population, the effects of methadone and butorphanol when combined with acepromazine were comparable.

Assessment of Right Heart Function during Extracorporeal Therapy by Modified Thermodilution in a Porcine Model.

BACKGROUND: Veno-arterial extracorporeal membrane oxygenation therapy is a growing treatment modality for acute cardiorespiratory failure. Cardiac output monitoring during veno-arterial extracorporeal membrane oxygenation therapy remains challenging. This study aims to validate a new thermodilution technique during veno-arterial extracorporeal membrane oxygenation therapy using a pig model. METHODS: Sixteen healthy pigs were centrally cannulated for veno-arterial extracorporeal membrane oxygenation, and precision flow probes for blood flow assessment were placed on the pulmonary artery. After chest closure, cold boluses of 0.9% saline solution were injected into the extracorporeal membrane oxygenation circuit, right atrium, and right ventricle at different extracorporeal membrane oxygenation flows (4, 3, 2, 1 l/min). Rapid response thermistors in the extracorporeal membrane oxygenation circuit and pulmonary artery recorded the temperature change. After calculating catheter constants, the distributions of injection volumes passing each circuit were assessed and enabled calculation of pulmonary blood flow. Analysis of the exponential temperature decay allowed assessment of right ventricular function. RESULTS: Calculated blood flow correlated well with measured blood flow (r2 = 0.74, P < 0.001). Bias was -6 ml/min [95% CI ± 48 ml/min] with clinically acceptable limits of agreement (668 ml/min [95% CI ± 166 ml/min]). Percentage error varied with extracorporeal membrane oxygenation blood flow reductions, yielding an overall percentage error of 32.1% and a percentage error of 24.3% at low extracorporeal membrane oxygenation blood flows. Right ventricular ejection fraction was 17 [14 to 20.0]%. Extracorporeal membrane oxygenation flow reductions increased end-diastolic and end-systolic volumes with reductions in pulmonary vascular resistance. Central venous pressure and right ventricular ejection fractions remained unchanged. End-diastolic and end-systolic volumes correlated highly (r2 = 0.98, P < 0.001). CONCLUSIONS: Adapted thermodilution allows reliable assessment of cardiac output and right ventricular behavior. During veno-arterial extracorporeal membrane oxygenation weaning, the right ventricle dilates even with stable function, possibly because of increased venous return.

Defense mechanisms to increasing back pressure for hepatic oxygen transport and venous return in porcine fecal peritonitis.

High central venous pressure (CVP) acutely decreases venous return. How this affects hepatic oxygen transport in sepsis remains unclear. The aim of this study was to evaluate the effects of repeated increases in CVP via standard nursing procedures (NPs) on hepato-splanchnic and renal oxygen transport in a prolonged porcine sepsis model. Twenty anesthetized and mechanically ventilated pigs with regional hemodynamics monitored were randomized to fecal peritonitis or controls (n = 10 pigs/group). Resuscitation was started after 8 h of observation and continued for 3 days. NPs were performed at baseline and 8 h, 32 h, 56 h, and 72 h after resuscitation started. NPs increased CVP by 4-7 mmHg in both groups. In controls, this was associated with less decrease in hepatic arterial (Qha; 62 ± 70 mL/min) than portal venous flow (Qpv; 364 ± 151 mL/min). Portal venous oxygen content and hepatic O2 delivery (Do2) and consumption (V̇o2) decreased by 11 ± 6 mL/dL and 0.9 ± 0.3 and 0.4 ± 0.3 mL·min-1·kg-1, respectively. In septic animals, hepatic Do2 decreased more in response to increasing CVP (1.5 ± 0.9 mL·min-1·kg-1), which was attributable to a larger fall in both Qha (88 ± 66 ml/min) and portal O2 content (14 ± 10 mL/dL, all P < 0.05). This resulted in numerically lower hepatic V̇o2 since O2 extraction did not increase significantly. In control conditions, a smaller decrease in Qha compared with Qpv helped to limit the reduction in hepatic V̇o2 in response to acute CVP increase. In sepsis, the contribution of Qha to maintain hepatic Do2 was reduced, which jeopardized hepatic V̇o2 further. Renal arterial flow was similarly affected by CVP increase as Qha.NEW & NOTEWORTHY Sepsis impairs intrinsic mechanisms to attenuate effects of increasing back pressure on hepatic oxygen transport.

Arterial Pouch Microsurgical Bifurcation Aneurysm Model in the Rabbit.

Endovascular treatment for intracranial aneurysms gained importance over the past decades, consequently there is an increased need of testing endovascular devices. Animal models respecting rheological, hemodynamic and aneurysm wall conditions are highly warranted. Therefore, the aim of the present study was to design a novel standardized and reproducible surgical technique to create autologous arterial pouch bifurcation aneurysms with non-modified and modified wall conditions in rabbits. Bifurcation aneurysms were created by end-to-side anastomosis of the right on the left common carotid artery, both serving as parent arteries for the arterial pouch, which was microsurgically sewn on. Grafts were taken from the proximal right common carotid artery, either for the control (n = 7, immediate autologous re-implantation) or modified (n = 7, incubated with 100 international units elastase for 20 minutes before autologous re-implantation) group. Pouch and parent artery patency were controlled by fluorescence angiography immediately after creation. At follow-up (28 days), all rabbits underwent contrast enhanced magnetic resonance angiography and fluorescence angiography followed by aneurysm harvesting, macroscopic and histological evaluation. A total of 16 female New Zealand White rabbits were operated upon. Two animals died prematurely. At follow-up, 85.72% of all aneurysms remained patent. Both groups revealed an increase in aneurysm size over time; this was more pronounced in the control group (6.48 ± 1.81 mm3 at time of creation vs. 19.85 ± 6.40 mm3 at follow-up, p = 0.037) than in the modified group (8.03 ± 1.08 mm3 at time of creation vs. 20.29 ± 6.16 mm3 at follow-up, p = 0.054). Our findings demonstrate the adequacy of this new rabbit model which allows for the creation of bifurcation aneurysms with different wall conditions in a microsurgical approach. Given the excellent long-term patency and the property of aneurysm growth over time, this model may serve as an important tool for preclinical evaluation of novel endovascular therapies.

An endovascular assisted, nonocclusive cerebral bypass: a technical feasibility study in a rabbit model.

OBJECTIVE: Temporary parent vessel occlusion performed to establish a high-flow interpositional bypass carries the risk of infarcts. The authors investigated the feasibility of a novel technique to establish a high-flow bypass without temporary parent vessel occlusion in order to lower the risk of ischemic complications. METHODS: In 10 New Zealand white rabbits, a carotid artery side-to-end anastomosis was performed under parent artery patency with a novel endovascular balloon device. Intraoperative angiography, postoperative neurological assessments, and postoperative MRI/MRA were performed to evaluate the feasibility and safety of the novel technique. RESULTS: A patent anastomosis was established in 10 of 10 animals; 3 procedure-related complications occurred. No postoperative focal neurological deficits were observed. The MRI/MRA findings include no infarcts and bypass patency in 50% of the animals. CONCLUSIONS: The authors demonstrated the feasibility of an endovascular assisted, nonocclusive high-flow bypass. Future refinement of the device and technique in an animal model is necessary to lower the complication rate and increase patency rates.

Comparison of Experimental Rat Models in Donation After Circulatory Death (DCD): in-situ vs. ex-situ Ischemia.

Introduction: Donation after circulatory death (DCD) could substantially improve donor heart availability. However, warm ischemia prior to procurement is of particular concern for cardiac graft quality. We describe a rat model of DCD with in-situ ischemia in order to characterize the physiologic changes during the withdrawal period before graft procurement, to determine effects of cardioplegic graft storage, and to evaluate the post-ischemic cardiac recovery in comparison with an established ex-situ ischemia model. Methods: Following general anesthesia in male, Wistar rats (404 ± 24 g, n = 25), withdrawal of life-sustaining therapy was simulated by diaphragm transection. Hearts underwent no ischemia or 27 min in-situ ischemia and were explanted. Ex situ, hearts were subjected to a cardioplegic flush and 15 min cold storage or not, and 60 min reperfusion. Cardiac recovery was determined and compared to published results of an entirely ex-situ ischemia model (n = 18). Results: In donors, hearts were subjected to hypoxia and hemodynamic changes, as well as increased levels of circulating catecholamines and free fatty acids prior to circulatory arrest. Post-ischemic contractile recovery was significantly lower in the in-situ ischemia model compared to the ex-situ model, and the addition of cardioplegic storage improved developed pressure-heart rate product, but not cardiac output. Conclusion: The in-situ model provides insight into conditions to which the heart is exposed before procurement. Compared to an entirely ex-situ ischemia model, hearts of the in-situ model demonstrated a lower post-ischemic functional recovery, potentially due to systemic changes prior to ischemia, which are partially abrogated by cardioplegic graft storage.

Systemic and CSF Interleukin-1α Expression in a Rabbit Closed Cranium Subarachnoid Hemorrhage Model: An Exploratory Study.

BACKGROUND: The inflammatory pathway in cerebrospinal fluid (CSF) leads to delayed cerebral vasospasm (DCVS) and delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH). The role of IL-1α has never been evaluated in a rabbit SAH model. The aim of our study is to analyze systemic and CSF changes of IL-1α, and to evaluate potential associations with the onset of DCVS in a rabbit closed cranium SAH model. Methods: 17 New Zealand white rabbits were randomized into two groups, SAH (n = 12) and sham (n = 5). In the first group, SAH was induced by extracranial-intracranial shunting from the subclavian artery into the cerebral cistern of magna under intracranial pressure (ICP) monitoring. The sham group served as a control. The CSF and blood samples for IL-1α measurement were taken at day zero before SAH induction and at day three. RESULTS: There was a significant increase of ICP (p = 0.00009) and a decrease of cerebral perfusion pressure (CPP) (p = 0.00089) during SAH induction. At follow up, there was a significant increase of systemic IL-1α in the SAH as compared with the sham group (p = 0.042). There was no statistically significant difference in the CSF values in both groups. The CSF IL-1α values showed a correlation trend of DCVS. CONCLUSIONS: Systemic IL-1α levels are elevated after SAH induction in a rabbit SAH model.

Iatrogenic cerebral arterial gas embolism from flushing of the arterial line in two calves.

BACKGROUND: Measurement of invasive blood pressure as reflection of blood flow and tissue perfusion is often carried out in animals during general anesthesia. Intravascular cannulation offers the potential for gas to directly enter the circulation and lead to arterial gas embolism. Cerebral arterial gas embolism may cause a spectrum of adverse effects ranging from very mild symptoms to severe neurological injury and death. Although several experimental models of arterial gas embolism have been published, there are no known published reports of accidental iatrogenic cerebral arterial gas embolism from flushing of an arterial line in animals. CASE PRESENTATION: A 7-day-old Red Holstein-Friesian calf (No. 1) and a 28-day-old Holstein-Friesian calf (No. 2) underwent hot iron disbudding and sham disbudding, respectively, under sedation and cornual nerve anesthesia. Invasive arterial blood pressure was measured throughout the procedure and at regular intervals during the day. Before disbudding, a sudden and severe increase of blood pressure was observed following flushing of the arterial line. Excitation, hyperextension of the limbs and rapid severe horizontal nystagmus appeared shortly thereafter. Over the following minutes, symptoms ameliorated and blood pressure normalized in both cases. Prompt diagnosis was missed in calf 1; supportive fluid therapy was provided. Severe deterioration of neurologic status occurred in the following 24 h and culminated with stupor. The calf was euthanized for ethical reasons and the histological examination revealed extensive cerebral injury. Treatment of calf 2 consisted of supportive fluid and oxygen therapy; furosemide (1 mg/kg IV) was injected twice. Calf 2 appeared clinically normal after 2 h and showed no neurologic sequelae on a 3-month-follow up period. CONCLUSIONS: There are no known reports of cerebral arterial gas embolism following flushing of the auricular arterial line in calves. The injection of a small amount of air at high pressure in a peripheral artery may lead to a significant cerebral insult. The clinical presentation is non-specific and can favour misdiagnosis and delay of therapy.