Jaime Viscasillas

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.

Ultrasonographic anatomy of the sacrococcygeal region and ultrasound-guided epidural injection at the sacrococcygeal space in dogs.

Sacrococcygeal epidural anaesthesia allows selective desensitisation of the sacral plexus. Ultrasound is used for guidance in human anaesthesia to facilitate sacrococcygeal epidural injections. The aims of this study were to describe the sonographic appearance of the sacrococcygeal region in dogs and a technique for performing epidural injection at this location under ultrasound guidance. In the preliminary part of the study four cadavers were used to describe the sonoanatomy of the sacrococcygeal space and to develop the ultrasound-guided puncture technique. In the second phase of the study this technique was repeated in four dogs under general anaesthesia. In all dogs the sacrococcygeal space appeared as a circular hypoechoic region, located caudal to the sacral caudal articular processes, delimited by bony hyperechoic structures such as body and arch of the first caudal vertebra. Ultrasound guidance allowed the operator to visualise and position the spinal needle into the sacrococcygeal epidural space. No complications were reported during this procedure. Preliminary results indicate that ultrasound-guided sacrococcygeal epidural anaesthesia may be considered as an alternative to a blind approach technique.

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.

Anaesthetic management and complications of balloon valvuloplasty for pulmonic stenosis in dogs.

PULMONIC stenosis (PS) is a common congenital cardiac defect in dogs (Buchanan 1992). Depending on the type of stenosis and its severity, surgical management is required. Balloon valvuloplasty (BV) is a non-invasive surgical technique that has become commonly performed in veterinary medicine (Bussadori and others 2001). Several protocols to anaesthetise patients undergoing this procedure have been described. However, only one retrospective study (Ramos and others 2014) assessing and reporting the perioperative complications during BV has been published recently. The aim of this study was to describe the anaesthetic management used over the past years in a large referring European veterinary institution and to explore which major factors are associated with complications in dogs undergoing BV. Forty-six dogs in which PS was managed with BV were included in this study. Parameters included in the analysis were breed, age, sex, weight, American Society of Anesthesiologists (ASA) status, severity of the stenosis, systolic pressure gradient, heart remodelling, presence of heart failure, patient medication, concurrent problems, use of NSAIDs, drugs used for premedication, induction and maintenance of anaesthesia, use of intermittent positive pressure ventilation (IPPV), use of other drugs, hypotension (mean arterial blood pressure 140 bpm), systemic hypertension (systolic arterial blood pressure >160 mmHg for at least five minutes), arrhythmias, treatment of complications, temperature at the end of procedure, length of …

Description of a new approach for great auricular and auriculotemporal nerve blocks: A cadaveric study in foxes and dogs

Abstract Otitis externa is a painful condition that may require surgical intervention in dogs. A balanced analgesia protocol should combine systemic analgesic agents and local anaesthesia techniques. The aim of the study was to find anatomical landmarks for the great auricular and the auriculotemporal nerves that transmit nociceptive information from the ear pinna and to develop the optimal technique for a nerve block. The study consisted of two phases. In phase I, one fox cadaver was used for dissection and anatomical localization of the auricular nerves to derive landmarks for needle insertion. Eight fox cadavers were subsequently used to evaluate the accuracy of the technique by injecting methylene blue bilaterally. In phase II findings from phase I were applied in four Beagle canine cadavers. A block was deemed successful if more than 0.6 cm of the nerves length was stained. Successful great auricular nerve block was achieved by inserting the needle superficially along the wing of the atlas with the needle pointing towards the jugular groove. For the auriculotemporal nerve block the needle was inserted perpendicular to the skin at the caudal lateral border of the zygomatic arch, close to the temporal process. The overall success rate was 24 out of 24 (100%) and 22 out of 24 (91%) for the great auricular and the auriculotemporal nerves, respectively, while the facial nerve was stained on three occasions. Our results suggest that it is feasible to achieve a block of the auricular nerves, based on anatomical landmarks, without concurrently affecting the facial nerve.

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.

Electrode fabrication and interface optimization for imaging of evoked peripheral nervous system activity with electrical impedance tomography (EIT)

OBJECTIVE Non-invasive imaging techniques are undoubtedly the ideal methods for continuous monitoring of neural activity. One such method, fast neural electrical impedance tomography (EIT) has been developed over the past decade in order to image neural action potentials with non-penetrating electrode arrays. APPROACH The goal of this study is two-fold. First, we present a detailed fabrication method for silicone-based multiple electrode arrays which can be used for epicortical or neural cuff applications. Secondly, we optimize electrode material coatings in order to achieve the best accuracy in EIT reconstructions. MAIN RESULTS The testing of nanostructured electrode interface materials consisting of platinum, iridium oxide, and PEDOT:pTS in saline tank experiments demonstrated that the PEDOT:pTS coating used in this study leads to more accurate reconstruction dimensions along with reduced phase separation between recording channels. The PEDOT:pTS electrodes were then used in vivo to successfully image and localize the evoked activity of the recurrent laryngeal fascicle from within the cervical vagus nerve. SIGNIFICANCE These results alongside the simple fabrication method presented here position EIT as an effective method to image neural activity.

Anaesthetic management and complications during hypophysectomy in 37 cats with acromegaly

Objectives The aim of this study was to describe the anaesthetic management and perianaesthetic complications encountered during hypophysectomy surgery in acromegalic cats. We explored relationships between animal demographic data, the anaesthetic protocol used and presence of perioperative complications. Methods Cats having undergone hypophysectomy surgery for the treatment of feline acromegaly at a single veterinary referral hospital were identified from hospital records. The anaesthesia records and clinical notes of these animals were retrospectively reviewed. Descriptive statistics were produced and binary logistic regression run to assess for any relationship between patient factors, anaesthetic management and complications during the perioperative period. Results Perianaesthetic complications identified included hypothermia, hypotension, bradycardia and airway obstruction. Mortality at 24 h post-anaesthesia was 8%. The use of alpha (α)2 agonists was associated with a lower incidence of hypotension. Fentanyl infusion was associated with a higher incidence of airway obstruction compared with remifentanil. Subjectively assessed anaesthetic recovery quality had an association with the number of days spent in the intensive care ward postoperatively. Conclusions and relevance The anaesthetic management described seems effective for hypophysectomy surgery in cats. Intraoperative complications were common and, while not apparently associated with 24 h patient outcome, drugs and equipment to manage these complications should be available.

Ultrasound-guided sciatic and femoral nerve blocks for metatarsal fracture stabilisation in a two-day-old neonatal calf

A two-day-old heifer calf presented with a non-weight bearing right hindlimb lameness following a traumatic event. A closed, complete, overriding, displaced fracture of the distal right metatarsal diaphysis was diagnosed and closed reduction and cast placement was elected as treatment. The calf was sedated intravenously with a combination of diazepam and ketamine. With the calf in lateral recumbency, sciatic and femoral nerve blocks were performed using procaine to provide analgesia and muscle relaxation for the procedure. The procedure was performed with the patient sedated and no further anaesthetics or analgesics were needed. This report is the first describing the use of sciatic and femoral nerve blocks as analgesia for a young calf. The success of the technique allowed a decrease in the dosage of other systemic drugs. This is an important factor in decreasing potential complications related to anaesthesia in these patients.

Anaesthetic management and complications of pacemaker implantation in dogs

The aim of this study was to report the anaesthetic management and peri-anaesthetic complications of 57 dogs undergoing pacemaker implantation at a referral institution over 10 years (2002–2012). The median duration of the procedure was 135 minutes (range 25–260 minutes). Patients were classified as American Society of Anaesthesiologist (ASA) III (42 cases) and ASA IV (15 cases). Forty-three patients had third-degree atrioventricular block, and 14 patients had sick sinus syndrome. The anaesthetic protocol most frequently chosen was pethidine (41 cases), etomidate-midazolam (43 cases) and isoflurane in oxygen for maintenance (57 cases). Transthoracic external pacing was used (43 cases) until the internal pacing lead was implanted. Atracurium was administered (48 cases) and intermittent positive pressure ventilation was applied in 52 cases. Complications observed included hypothermia (19 cases) and hypotension (5 cases). Three patients died (5.8%, 95% CI 1.1% to 14.6%) within the first 48 hours after termination of anaesthesia. The outcome for this procedure in sick animals appeared generally good though a number of complications were documented.