Ultrasound-Guided Continuous Block of Median and Ulnar Nerves in Horses: Development of the Technique
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Veterinary Anaesthesia and Analgesia 2020, 47, 405e413 https://doi.org/10.1016/j.vaa.2019.12.008 RESEARCH PAPER Ultrasound-guided continuous block of median and ulnar nerves in horses: development of the technique Maria Teresa MR Soutoa, Denise T Fantonib, Adilson Hamajic, Marcelo Hamajic, Cynthia P Vendruscolob, Denise A Otsukid, Ana Carolina BCF Pintob & Aline M Ambrosio b aDepartment of Anesthesiology, School of Medicine, University of Sao~ Paulo, Sao~ Paulo, SP, Brazil bSurgical Clinic Department, School of Veterinary Medicine and Animal Science, University of Sao~ Paulo, Sao~ Paulo, SP, Brazil cClinical Hospital, Institute of Orthopedics and Traumatology, Sao~ Paulo, SP, Brazil dLIM/08, Laboratory of Anesthesiology, Laboratory of Medical Research, Clinical Hospital, School of Medicine, University of Sao~ Paulo, Sao~ Paulo, SP, Brazil Correspondence: Maria Teresa MR Souto, Department of Anesthesiology, USP Medical School, Av. Dr. Eneas de Carvalho Aguiar nº 155, 8º Andar e Predio dos Ambulatorios - Bloco 3 - CEP 05403-000 - Cerqueira Cesar Sao~ Paulo, SP, Brazil. E-mail: [email protected] Abstract bearing in affected limbs and decreased requirement for systemic analgesic medications. No local reactions were Objective To develop a technique for ultrasound-guided observed. continuous median and ulnar peripheral nerve block in horses. Conclusions and clinical relevance The ultrasound tech- nique allowed real-time visualization of needle, catheter and Study design Anatomical and prospective experimental drug dispersion and resulted in a high success rate for nerve study. blocks. The horses administered a median and ulnar nerve Animals A total of 16 thoracic limbs from horse cadavers block exhibited no discomfort or signs of infection at the and 18 adult horses. catheter insertion site. Further studies are warranted to validate the efficacy of this technique. Method This study was conducted in three phases. Phase 1: Dissection of median and ulnar nerves in the ante- Keywords brachial region of two cadaver limbs to identify localizing catheters, horses, indwelling, infusion pump, landmarks. Description of sonoanatomy in 14 cadaver nerve block, ultrasonography. limbs using ultrasound-guided perineural infiltration of a combination of cellulose gel (5 mL), contrast medium (4 Introduction mL) and methylene blue (1 mL). Catheters were inserted between the perineural sheath and epineurium in six limbs, Musculoskeletal diseases are the leading causes of loss in the followed by computed tomography. Phase 2: Ultrasono- horse industry. These diseases involve muscles, bones, joints, graphic images of the limbs of 18 healthy horses of different tendons and ligaments, with ligament damage being the most breeds were used to define an acoustic window and opti- clinically relevant because of slow healing and consequent mize the approach to nerves. Phase 3: Two case reports of transition to chronic disorders (Broster et al. 2009; Wagner horses with chronic pain of different etiologies. Catheters 2010; Caston & Burzette 2018). Surgical trauma, especially were inserted between the epineurium and paraneural with preexisting pain, may cause peripheral and central pain sheath of the median and/or ulnar nerves guided by ul- sensitization and result in long-lasting, intractable pain syn- trasound, followed by continuous infusion of 0.4% dromes (Hoheisel & Mense 1989; Harvey et al. 2004; Driessen ropivacaine. et al. 2008; Guedes 2017) Diseases such as laminitis cause pain refractory to conventional systemic analgesia, requiring Results Information from phase 1 was used to direct needle euthanasia in serious cases (Collins et al. 2010; Wylie et al. insertion, solution dispersion and catheter implantation in 2012). Pain in horses is controlled by the use of non- phase 2, which resulted in 100% technique accuracy. In steroidal anti-inflammatory drugs (NSAIDs), steroids, opioids, response to the peripheral nerve block, pain reduction was N-methyl-D-aspartate receptor blockers and anticonvulsants apparent in the two clinical cases by increased weight (Driessen 2007). Prolonged NSAID use is the most common 405 Median and ulnar nerve blocks in horses MTMR Souto et al. treatment in equine pain medicine, often causing serious side Materials and methods effects (Taylor et al. 2002; Flecknell 2008; van Weeren & de This study was approved by the Animal Ethics Committee of Grauw 2010; Bardell 2017). Furthermore, NSAIDs alone are the School of Veterinary Medicine and Animal Science, Uni- ineffective at controlling moderate to intense pain in humans versity of Sao~ Paulo, Brazil (no. 7941181114) and by the according to the World Health Organization. Although opioids Animal Ethics Committee of the Medical School, University of are more effective than NSAIDs in controlling pain, they too Sao~ Paulo, Brazil (no. 175/14). It was conducted at the Vet- can cause adverse effects in horses (Taylor et al. 2002; erinary Hospital of the School of Veterinary Medicine and Flecknell 2008; van Weeren & Back 2016). Animal Science of the University of Sao~ Paulo, Brazil. Use of regional anesthesia is popular in human medicine. Peripheral nerve blocks can improve analgesia, decrease the Animals duration of hospitalization and, by decreasing the need for systemic medication, minimize the side effects (Kapral et al. The study was divided into three phases. In phase 1, the 2008; Kiran et al. 2018). Use of ultrasonography allows anatomy of the antebrachial region containing median and visualization of the needle position and spread of the local ulnar nerves was defined using dissection, ultrasonography anesthetic solution in real time. The advantages over con- and computed tomography (CT) in horse cadavers. In phase 2, ventional, blind techniques are significant, such as decreased the same anatomy was studied using ultrasonography in volume for injection for effective blockade, reducing the risk of conscious horses of different breeds. In phase 3, median and toxicity from the local anesthetic, and decreased risk of intra- ulnar nerve blocks were evaluated in two clinical equine neural or intravascular injections or damage (Marhofer et al. patients. 1998, 2010; Kapral et al. 2008; Kiran et al. 2018). High- resolution equipment is essential, and the clinician must ac- Phase 1 quire experience in ultrasonography and knowledge of the The thoracic limbs of eight horses that died for reasons unre- local anatomy of the nerve to be blocked (Gray 2006; Juanes lated to this study were used. Immediately after death, the et al. 2016). limbs were disarticulated from the body at the scapula and Local anesthetic solution for a peripheral nerve block can be frozen. The limbs were slowly thawed by immersing the limbs administered as single or multiple boluses or by a continuous in a container of water at room temperature for 24 hours. The infusion (Gray & Schafhalter-Zoppoth 2003; Jones et al. anatomy of two limbs was studied using literature guidelines 2007). A continuous infusion of local anesthetic is delivered on neuroanatomy of equine thoracic limbs and the aid of an through a catheter inserted percutaneously, using ultrasound anatomist (Constantinescu et al. 2004; Ashdown & Done to guide the tip to the nerve or plexus. The drug can be titrated 2012). The limb was placed with the lateral side facing according to the desired level of motor or sensory block down, and the skin and superficial fascia were dissected (Marhofer et al. 2010). Nerve blocks are indicated in the exposing the pectoralis transversus, flexor carpi radialis, flexor perioperative or postoperative periods, as well as for chronic carpi ulnaris, superficial digital flexor and deep digital flexor pain, because local analgesia can provide effective pain relief muscles as well as the median and ulnar nerves. with a lower incidence of side effects compared with systemic The other 14 thoracic limbs were examined for the sonoa- administration of analgesics (Capdevila et al. 2005; Ilfeld natomy study. The limbs were placed with the lateral side 2011, 2017). facing down and the limb in extension. Ultrasonography was Studies of continuous perineural blockade of the palmar performed using a multifrequency linear transducer (13e6 nerves in the distal equine thoracic limb have been published MHz, model HFL38x; FUJIFILM SonoSite Inc., WA, USA) (Zarucco et al. 2007, 2010; Driessen et al. 2008; Watts et al. configured with nerve preset and a SonoSite M-turbo model 2011). No studies regarding continuous median and (FUJIFILM SonoSite Inc.). The transducer was positioned ulnar nerve blockade in horses were found in the literature transversely to the limb (short axis) to identify the median and search. The aim of this study was to describe the gross anatomy ulnar nerves and all structures adjacent to them. Initially, and ultrasonographic anatomy of the median and ulnar echogenic needles (22 gauge, 0.70 Â 50 mm; Stimuplex ultra; nerves at the antebrachium in horses, to identify landmarks for B Braun Melsungen, Germany) were placed between the needle and catheter insertion at this site and to test these epineurium and paraneural sheath of both nerves in the procedures in vivo and assessing response to ropivacaine antebrachial region. The needles were inserted percutaneously injection. Our hypothesis was that the use of ultrasound at an angle of approximately 60 degrees between the trans- would allow precise localization of the median and ulnar ducer and the limb in a proximal to distal direction. The so- nerves in real time and that the adequate positioning