Human-relevant near-organ neuromodulation of the immune system via the splenic nerve.

Neuromodulation of immune function by stimulating the autonomic connections to the spleen has been demonstrated in rodent models. Consequently, neuroimmune modulation has been proposed as a new therapeutic strategy for the treatment of inflammatory conditions. However, demonstration of the translation of these immunomodulatory mechanisms in anatomically and physiologically relevant models is still lacking. Additionally, translational models are required to identify stimulation parameters that can be transferred to clinical applications of bioelectronic medicines. Here, we performed neuroanatomical and functional comparison of the mouse, rat, pig, and human splenic nerve using in vivo and ex vivo preparations. The pig was identified as a more suitable model of the human splenic innervation. Using functional electrophysiology, we developed a clinically relevant marker of splenic nerve engagement through stimulation-dependent reversible reduction in local blood flow. Translation of immunomodulatory mechanisms were then assessed using pig splenocytes and two models of acute inflammation in anesthetized pigs. The pig splenic nerve was shown to locally release noradrenaline upon stimulation, which was able to modulate cytokine production by pig splenocytes. Splenic nerve stimulation was found to promote cardiovascular protection as well as cytokine modulation in a high- and a low-dose lipopolysaccharide model, respectively. Importantly, splenic nerve-induced cytokine modulation was reproduced by stimulating the efferent trunk of the cervical vagus nerve. This work demonstrates that immune responses can be modulated by stimulation of spleen-targeted autonomic nerves in translational species and identifies splenic nerve stimulation parameters and biomarkers that are directly applicable to humans due to anatomical and electrophysiological similarities.

Mortality related to general anaesthesia and sedation in dogs under UK primary veterinary care.

OBJECTIVES: To quantify and explore risk factors in dogs seen at primary care UK veterinary clinics for general anaesthetic (GA)/sedative-related death overall, in addition to neuter-specific procedures. STUDY DESIGN: A nested case-control study within UK primary care veterinary electronic patient record surveillance programme, VetCompass, including over 300 UK veterinary practices. ANIMALS: A total of 157,318 dogs undergoing GA/sedative events. METHODS: Cases included dogs undergoing GA/sedative events between January 2010 and December 2013 with GA/sedative-related death recorded within 48 hours or 2 weeks of the event. Controls were randomly selected from dogs undergoing GA/sedation that did not die within these time periods. Risks of GA/sedative-related death for all surgeries and neuter-specific surgeries were estimated. Demographic and clinical associations with GA/sedative-related death were reported as odds ratios following multivariable logistic regression modelling. Statistical significance was set at 5%. RESULTS: From 157,318 dogs with a GA/sedative event, there were 159 (0.10%) within 48 hours and 219 (0.14%) GA/sedative-related deaths within 2 weeks. Within 89,852 dogs that underwent a neuter surgery, there were eight GA/sedative related (0.009%). Greater age, poorer American Society of Anaesthesiologists health status scores and more urgent procedures were associated with greater odds of death. Compared with mixed breeds, Rottweilers and West Highland White Terriers had greater odds and Cocker Spaniels had lower odds of GA/sedative-related death. CONCLUSIONS AND CLINICAL RELEVANCE: The overall risk for GA/sedative related death was relatively low, particularly among the subset of dogs undergoing castration or ovariohysterectomy surgery. Associations and risk estimates may assist shared decision-making in clinical practice and provide benchmarks for audit.

Lumbar erector spinae plane block: an anatomical and dye distribution evaluation of two ultrasound-guided approaches in canine cadavers.

OBJECTIVE: To examine the anatomy of the lumbar epaxial region and to describe two different ultrasound-guided approaches for the lumbar erector spinae plane (ESP) block in dogs. STUDY DESIGN: An anatomical and experimental cadaver study. ANIMALS: A group of 19 canine cadavers. METHODS: The anatomy was described following dissection of two cadavers. Bilateral ultrasound-guided ESP injections with 0.4 mL kg-1 of contrast dye were performed in 17 adult Beagle cadavers using either transversal (TVS) or parasagittal (PST) approaches. Computed tomography was performed to measure the total length of the contrast dye column and the epidural, intravascular, hypaxial and intra-abdominal migration. Dissections were performed to assess the spread of the contrast dye and to determine the degree of staining of the dorsal branches of the spinal nerves (DBSN). Mann-Whitney U and chi-square tests were used to compare data between groups. RESULTS: Using both techniques, the contrast dye was observed within the ESP compartment. There was no difference in the total length of the contrast dye column between TVS and PST approaches (p = 0.056). Using the TVS approach, multisegmental staining of the DBSN was visible with 100% (17/17) of injections, while complete staining of the DBSN was achieved at 94% of the injection sites. Using the PST approach, these values were 29% (5/17) and 23% (4/17), respectively. The TVS approach stained more DBSN than the PST approach (p = 0.001), with a median (range) of 2 (2-3) versus 0 (0-3) DBSN, respectively. Using the TVS approach, epidural and intravascular migration were present in 2/17 (p = 0.485) and 3/17 (p = 0.227) injections, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Both ultrasound-guided approaches resulted in a spread of the contrast dye within the ESP compartment. Although there were no differences in the total length of the contrast dye column, the TVS approach was superior to the PST approach in staining DBSN.

In-plane ultrasound-guided peribulbar block in the dog: an anatomical cadaver study.

OBJECTIVE: To describe a novel in-plane ultrasound (U/S)-guided temporal approach to peribulbar block in dogs. STUDY DESIGN: Prospective experimental cadaver study. ANIMALS: A group of 10 Beagle cadavers. METHODS: After describing the U/S anatomy, peribulbar injection was performed bilaterally in 10 thawed Beagle cadavers by two randomly assigned operators. A 5-8 MHz microconvex U/S probe was positioned caudal to the orbital ligament in the longitudinal plane. Using an in-plane technique, methylene blue dye was injected in five dogs (10 eyes total), while methylene blue dye and iohexol contrast mixture (50:50) were injected in the remaining five dogs. Injection volume was 0.2 mL cm-1 of cranial length. A computed tomography (CT) scan was performed on dogs injected with dye and contrast to identify spread of contrast. Dissection to visualize dye spread in the orbit was performed in all dogs. Injection success was defined as spread of contrast into the peribulbar space. The pattern of distribution of contrast-dye was also assessed. Comparisons between operator and bilateral injections were assessed using a Student t test (p < 0.05). All other data are reported as number (n/N) and percentage (%). RESULTS: Peribulbar spread was noted in 19/20 injections (95%) on dissection. CT imaging (five dogs) illustrated peribulbar contrast spread in 9/10 injections (90%), with mixed peribulbar/retrobulbar spread for the remaining injection. Contrast was present at the rostral alar foramen in 4/10 (40%) injections, orbital fissure in 5/10 (50%), oval foramen in 1/10 (10%), maxillary nerve in 3/10 (30%) and intracranial in 5/10 (50%). Coverage of the maxillary nerve was noted on 3/20 (15%) injections on dissection. No further dye spread was noted. CONCLUSIONS AND CLINICAL RELEVANCE: This technique demonstrated peribulbar spread of injectate in 100% of injections for the 10 canine cadavers studied. Further studies are required to evaluate this technique clinically.

Ultrasound-guided posterior extraconal block in the dog: anatomical study in cadavers.

OBJECTIVE: To describe a novel ultrasound-guided posterior extraconal block in the dog. STUDY DESIGN: Prospective experimental cadaveric study. ANIMALS: A total of 13 Beagle Cross cadaver heads. METHODS: After describing the ultrasound bony landmarks and posterior extraconal local regional technique in one head, 12 heads were used to evaluate the spreading of contrast and evaluate potential complications. A 5-8 MHz microconvex ultrasound probe was positioned caudal to the orbital ligament, with the beam orientated transversely, and then tilted caudally until the orbital fissure was visualized. After identifying the bony structures consistent with the orbital fissure, a needle was advanced using an in-plane technique and 0.5 mL of a 50:50 mixture of iohexol and methylene blue was injected. Computed tomography (CT) and dissection were used to evaluate successful injections and potential complications. The injection was considered successful if radiopaque contrast medium was 5 mm from the orbital fissure. Potential complications were defined as the presence of radiopaque contrast within the globe or the intracalvarial tissues. RESULTS: The CT images confirmed contrast at the target site in 15/24 (63%) of the injections. Only two injections were found in the temporalis muscle; the rest of the injections were located in the extraconal space. No potential complications such as intracranial spreading of contrast, intravascular or intraocular injection were found. CONCLUSIONS AND CLINICAL RELEVANCE: The technique can deliver contrast close to the main nerves which provide sensory and motor innervation to the eye. Further studies are needed to evaluate this technique in clinical cases.

A sonographic investigation for the development of ultrasound-guided paravertebral brachial plexus block in dogs: cadaveric study.

OBJECTIVE: To describe a novel in-plane ultrasound (US)-guided approach to the sixth (C6), seventh (C7), eighth (C8) cervical and to the first thoracic (T1) spinal nerves. STUDY DESIGN: Prospective, descriptive, experimental anatomic study. ANIMALS: A total of seven canine Beagle cadavers. METHODS: Phase 1: One cadaver was used to define bony landmarks for the C6-T1 spinal nerves using computed tomography (CT) and magnetic resonance imaging. An US transducer was positioned lateral to the C6 vertebra. Methylene blue (0.05 mL kg-1) was injected cranial and caudal to the transverse process of C6. The probe was moved caudally to identify the cranial costal fovea of T1 and 0.1 mL kg-1 of methylene blue was injected. Full cadaver dissection was performed to assess the staining of the spinal nerves. Phase 2: The technique was repeated using a 50:50 mixture of iohexol and methylene blue in six dogs. CT verified the proximity of contrast to C6, C7, C8 and T1 nerves. Mediastinal, epidural, intravascular and pleural contamination was recorded. Methylene blue staining of the phrenic nerve was assessed by dissection. RESULTS: Phase1: The identified bony landmarks were the lamina ventralis of C6, the transverse process of C6 and C7, T1 vertebra and the first rib. Phase 2: At all the 12 sites, the C6, C7 and C8 nerves were in contact with contrast material. Contrast was demonstrated in close proximity to the anatomical location of the T1 nerve in 11/12 sites. Mediastinal, epidural and intravascular contamination was observed in six, four and two cadavers, respectively. Pleural contamination was not observed. The phrenic nerve was stained on 2/12 of sides. CONCLUSIONS AND CLINICAL RELEVANCE: In-plane US-guided blockade of the spinal roots is a feasible technique. However, because of the undesirable spreads of contrast, further research is needed to diminish the occurrence of contaminations of noble structures.

Ultrasound-guided thoracic paravertebral block: cadaveric study in foxes (Vulpes vulpes).

OBJECTIVE: To describe an ultrasound-guided thoracic paravertebral block in canidae. STUDY DESIGN: Prospective, experimental, cadaveric study. ANIMALS: Twelve thawed fox cadavers. METHODS: A 15 MHz linear transducer was used to visualize the paravertebral space at the level of the fifth thoracic vertebrae. Iohexol (300 mg mL-1) at 0.2 mL kg-1 was injected into the right and left paravertebral spaces under ultrasound guidance using a Tuohy needle. The needle was advanced in a lateral to medial direction using an in-plane technique. Injections were performed by two operators, each performing 12 injections in six fox cadavers. A thoracic computed tomography was then performed and evaluated by a single operator. The following features were recorded: paravertebral contrast location (yes/no), length of contrast column (number of intercostal spaces), location of contrast relative to the fifth thoracic vertebrae (cranial/caudal/mixed), epidural contrast contamination (yes/no), pleural contrast contamination (yes/no) and mediastinal contrast contamination (yes/no). RESULTS: All injections resulted in paravertebral contrast distribution (24/24). The mean length of the contrast column was five intercostal spaces. Contrast spread was caudal to the injection site in 54% (7/24), cranial in 29% (4/24) and mixed in 17% (3/24). Pleural contamination was observed in 50% (12/24) of injections; 42% (10/24) and 4% (1/24) of the injections resulted in mediastinal and epidural contamination, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Injection of the paravertebral space in canidae is possible using the technique described. Possible complications include epidural, pleural and mediastinal contamination. To establish clinical efficacy and safety of this technique, further studies are required.

Ultrasound-guided subcostal oblique transversus abdominis plane block in canine cadavers.

OBJECTIVES: To describe the ultrasound-guided transversus abdominis plane (TAP) block using a subcostal oblique approach in dog cadavers and to evaluate the spread of a methylene blue solution using a multiple-injection technique. STUDY DESIGN: Prospective, descriptive, experimental anatomic study. ANIMALS: Nine adult Beagle cadavers weighing a mean ± standard deviation of 13 ± 2 kg. METHODS: Methylene blue solution (10.0 mL) was injected bilaterally within the fascia that overlies the transversus abdominis muscle in dog cadavers under ultrasound guidance. A total of three injections (3.3 mL each) were administered on each side by the same operator. Dissection was performed by a second operator 20 minutes later. Successful nerve staining was defined as the presence of dye on the nerve for a length of >1 cm. RESULTS: Ventral branches of the T9, T10, T11, T12 and T13 nerves innervating the cranial abdominal wall were stained in 72%, 95%, 100%, 95% and 61% of cases, respectively. Ventral branches of L1 and L2 innervating the caudal abdominal wall were stained in only 33% and 11% of cases, respectively. The dye was found only in the fascia between the transversus abdominis and the internal oblique muscles. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrasound-guided subcostal oblique TAP block provided adequate staining of the sensory innervation of the cranial abdominal wall. Further studies are required to evaluate the efficacy of this technique in blocking the nociceptive response in clinical procedures.

Description and evaluation of four ultrasound-guided approaches to aid spinal canal puncture in dogs.

OBJECTIVE: To describe four ultrasound-guided approaches to the lumbar and thoracic spine to aid spinal canal puncture in the dog and to evaluate the feasibility of the technique. STUDY DESIGN: Prospective experimental study. ANIMAL POPULATION: Two canine cadavers. METHODS: In the first part of the study, the ultrasonographic appearance of the interlaminar space in the lumbosacral, lumbar and thoracic regions was described. In the second part of the study, four operators attempted a real-time, ultrasound-guided approach to the vertebral canal. Each operator performed the technique 20 times in total: five times at the lumbosacral junction, five in the thoracic region, five in the lumbar region with an in-plane approach, and five in the lumbar region with an out-of-plane approach. Computed tomography (CT) was used to confirm the position of the needle. The procedure was considered successful when the tip of the needle was observed within the vertebral canal. The success rate was calculated for each approach and operator. Fisher's exact test was used to compare differences between approaches and operators. RESULTS: In all cases, visualization of a ventral, parallel and straight hyperechoic line (floor of the vertebral canal) was considered a necessary prerequisite for successful positioning of the needle within the vertebral canal. A straight hyperechoic line (ligamentum flavum or dura mater) closer to the ultrasound probe was visualized in both the median lumbosacral approach and the transverse lumbar approach. The success rate overall was 81%; for the lumbosacral approach, 100%; for the thoracic approach, 80%; for the in-plane lumbar approach 95%; and for the out-of-plane lumbar approach, 45%. These differences were statistically significant (p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: The sonographic description of these approaches was considered adequate for performing spinal canal puncture. In-plane techniques achieved a higher success rate than out-of-plane ones. Further studies are needed to evaluate them in a clinical setting.

A description of a technique for ultrasound-guided lumbar plexus catheter in dogs: cadaveric study.

OBJECTIVE: To describe an ultrasound-guided approach for lumbar plexus catheter placement in dogs. STUDY DESIGN: Prospective experimental cadaveric study. ANIMALS: Eleven thawed canine cadavers (13 ± 2 kg). MATERIAL AND METHODS: A technique to place a catheter in the psoas compartment at the level of the lumbar plexus under ultrasound guidance was described. Ultrasonographic landmarks for the placement of a lumbar plexus catheter were identified as the body of the sixth lumbar vertebrae, the psoas muscle and the femoral nerve. All catheters were placed by the principal investigator using epidural sets with an 18-G Tuohy needle. The procedure was carried out twice in each cadaver, with the aim of placing a catheter at the point of the left and right lumbar plexuses. A total volume of 0.4 mL kg(-1) of 1% methylene blue solution was injected into the psoas compartment after which the catheter was removed. After performing the injection in four cadavers, the technique was modified, altering the angle of needle placement and length of catheter insertion. Staining of the femoral and obturator nerves was assessed. Success was recorded if both nerves were stained over a length >1 cm. The spreading of the dye into the abdomen or to the nerve roots was also recorded. RESULTS: The success rate after the first four cadavers was four out of eight, and dye was found in the abdomen of two of the cadavers. When the modified technique was used in the subsequent seven cadavers, the success rate was 12 out of 14, and no dye was found in the abdomens. CONCLUSIONS AND CLINICAL RELEVANCE: This technique has shown a high percentage of success and low rate of complications. The only complication investigated in this study was the spread to the abdomen or epidural space. To establish safety, clinical studies will be needed.

Anaesthetic mortality in cats: A worldwide analysis and risk assessment.

BACKGROUND: Patient safety is essential in small animal anaesthesia. This study aimed to assess anaesthesia-related deaths in cats worldwide, identify risk and protective factors and provide insights for clinical practice. METHODS: A prospective multicentre cohort study of 14,962 cats from 198 veterinary centres across different countries was conducted. Data on anaesthesia-related deaths, from premedication up to 48 hours postextubation, were collected. Logistic regression was used to analyse patient demographics, American Society of Anesthesiologists (ASA) classification, procedure type and anaesthetic drugs. RESULTS: The anaesthesia-related mortality was 0.63%, with 74.5% of deaths occurring postoperatively. Cats with cachexia, a higher ASA status or who underwent abdominal, orthopaedic/neurosurgical or thoracic procedures exhibited elevated mortality. Mechanical ventilation use was associated with increased mortality. Mortality odds were reduced by the use of alpha2-agonist sedatives, pure opioids in premedication and locoregional techniques. LIMITATIONS: Limitations include non-randomised sampling, potential biases, unquantified response rates, subjective death cause classification and limited variable analysis. CONCLUSIONS: Anaesthetic mortality in cats is significant, predominantly postoperative. Risk factors include cachexia, higher ASA status, specific procedures and mechanical ventilation. Protective factors include alpha2-agonist sedatives, pure opioids and locoregional techniques. These findings can help improve anaesthesia safety and outcomes. However, further research is required to improve protocols, enhance data quality and minimise risks.

A cadaver study comparing two approaches for performing maxillary nerve block in dogs.

OBJECTIVE: To compare the success by inexperienced anaesthetists of using a modified infraorbital approach to the maxillary nerve with the traditional percutaneous approach. STUDY DESIGN: Prospective, randomized, blinded controlled study. ANIMALS: Heads from 37 euthanized Beagle and Beagle cross dogs. METHODS: Four anaesthetists were recruited to perform two different approaches to block the maxillary nerve of the cadavers. The infraorbital (I) approach advanced an intravenous catheter along the infraorbital canal. Earlier measurements from scans of similar heads were used to assess suitable catheter size. The percutaneous (P) approach introduced a needle percutaneously just below the ventral border of the zygomatic arch. The side of the head where the technique was to be performed was randomized. A total volume of 0.5 mL methylene blue was injected in each approach. After completion of injections, head dissections were performed by an investigator unaware of the approach used and staining of the maxillary and pterygopalatine nerves was evaluated. Chi squared analysis examined the relationship between the methods (p < 0.05). Complications related to the techniques, such as intravascular/intraneural injection and location of the dye, were evaluated macroscopically. RESULTS: Maxillary nerve staining >6 mm was found in 64.9% (I) versus 21.6% (P) attempts; staining <6 mm was found in 27% (I) versus 21.6% (P); and no nerve staining 8.1% (I) versus 56.8% (M). Pterygopalatine nerve staining was found in 70% (I) versus 21% (P). The infraorbital approach demonstrated significantly higher maxillary and pterygopalatine nerve staining compared to the percutaneous approach (p = 0.001 for both nerves). No evidence of intravascular/intraneural injections was found. CONCLUSION AND CLINICAL RELEVANCE: The infraorbital approach was more successful than the percutaneous approach when performed by inexperienced anaesthetists. No macroscopic complications were observed.

Use of needle enhancing software to improve injection technique amongst inexperienced anaesthetists performing ultrasound-guided peripheral nerves blocks in dogs.

OBJECTIVE: To determine if the use of needle enhancing software facilitate injection technique in ultrasound-guided peripheral nerve blocks. STUDY DESIGN: Prospective, blinded, randomized controlled trial. ANIMALS: Eight hind limbs from canine cadavers. METHODS: The limbs were randomly allocated to two groups; software on (group I) and software off (group II). Eight anaesthetists with no previous experience of ultrasound-guided regional anaesthesia were recruited. Thirty-six procedures were carried out (18 per group). After sciatic nerve visualisation via ultrasonography, the anaesthetist introduced a needle guided by ultrasonography. When the tip of the needle was considered by the anaesthetist to be as close as possible to the nerve without touching it, 0.05 mL of methylene blue dye was injected. Parameters evaluated included: number of attempts to visualise the needle with ultrasonography, time spent to perform the technique, subjective evaluation of ease of needle visualisation, proximity of the tip of the needle to the nerve, and, at dissection of the leg, inoculation site of the dye in relation to the nerve. RESULTS: Significant differences between groups were identified in relation to the number of attempts (group I: median 1, IQR: 1 - 1 attempts versus group II: median 1, IQR: 1 - 4 attempts, p = 0.019), and the relationship between the dye and the nerve during hind limb dissection (72.2% of the nerves were stained in group I versus 16.6% in group II, p = 0.003). No significant difference between groups was observed with respect to the time taken to perform the procedure (group I: median 25.5, IQR: 18.4 - 44.3 seconds versus group II: median 35.7, IQR: 18.6-78.72 seconds, p = 0.31), subjective evaluation of the needle visualization (p = 0.45) or distance between the tip of the needle and the nerve as measured from the ultrasound screen (p = 0.23). CONCLUSIONS AND CLINICAL RELEVANCE: This study identified greater success rate in nerve staining when the needle enhancing software was used. The results suggest that the use of this technique could improve injection technique amongst inexperienced anaesthetists performing ultrasound-guided peripheral nerve blocks in dogs.

Assessment of an Ultrasound-Guided Rectus Sheath Block in Foals: A Cadaveric Study.

In neonatal equines, pathologies involving umbilical structures are an important cause of morbidity, and surgical removal of urachal remnants is a common procedure in clinical practice. Surgery involving the ventral abdominal wall can cause substantial pain, leading to complications and prolonged recovery. The objectives of this study were to describe a two-point bilateral ultrasound-guided rectus sheath block at the level of the umbilicus and to evaluate the extent of dye distribution in foal cadavers. Ten foal cadavers were included in the study, in which a bilateral two-point ultrasound-guided rectus sheath block was performed-one injection 5 cm cranially and a second one 5 cm caudally to the umbilicus. The injectate consisted of a mixture of iodinated contrast medium and blue dye at a volume of 0.25 mL kg-1 per injection point (total 1 mL kg-1). After the injection, computer tomography and subsequent dissection of the ventral abdominal wall were performed. The extension of the contrast medium, the number of stained nerves, and contamination of the abdominal cavity were evaluated. The cranio-caudal extension of the contrast ranged from 0.8 to 1.4 cm per milliliter of injectate. The most commonly stained ventral branches of spinal nerves were thoracic (Th) nerves 16, 17, and 18 (95%, 85%, and 80% of the nerves, respectively). Abdominal contamination was found in four animals. The results suggest that the block could provide periumbilical analgesia. Further studies with different volumes of injectate and living animals are warranted.