Locoregional Anesthesia Techniques for Large Animals PDF

Locoregional anesthesia techniques for large animals Dr. André Escobar, DVM, Ms, PhD, DACVAA Assistant Professor of Anesthesiology Outline • Equine • Head • Epidural • Castration • Ruminant • • • • • • Head Laparotomy Epidural Udder/teat Foot Castration Equine eye – motor nerve • Auriculopalpe...

Locoregional anesthesia techniques for large animals Dr. André Escobar, DVM, Ms, PhD, DACVAA Assistant Professor of Anesthesiology Outline • Equine • Head • Epidural • Castration • Ruminant • • • • • • Head Laparotomy Epidural Udder/teat Foot Castration Equine eye – motor nerve • Auriculopalpebral nerve block • Used to prevent closure of the eyelid (blinking) • Ophthalmic exam • Nerve can be palpated • Motor block only – do not desensitize the eye • Injection site • Dorsal aspect of the zygomatic arch OR • Depression caudal to the mandible Lumb and Jones 2015 Equine eye – sensory nerves • A - Supraorbital nerve • Majority of the upper eyelid • Injection at supraorbital foramen • B - Lacrimal nerve • C – Infratrochlear nerve • D – Zygomatic nerve SQ injection • Standing enucleation • All nerves previously mention + retrobulbar Lumb and Jones 2015 Equine dental • Infraorbital nerve block • Desensitize ipsilateral upper lip and nose (G) • Desensitize teeth rostral to 1st molar, maxillary sinus, roof of nasal cavity (H) • Mental nerve block • Desensitize lower lip (I) • Desensitize lower incisors (K) Lumb and Jones 2015 Equine dental • Inferior alveolar nerve block • Anesthesia of the mandible https://academyofequinedentistry.wordpress.com Equine dental • Maxillary nerve block • Maxilla and sinus cavity https://academyofequinedentistry.wordpress.com Equine epidural • Caudal epidural • • • • Prevent loss of motor function Inserted between Co1-Co2 space Space palpated moving the tail up and down Loss of resistance/ hanging drop technique Equine epidural • Indications • Tail, perineum, rectum or vulva procedures • Fetotomy, obstetric manipulations • Hindlimb analgesia (do not use local anesthetics) Equine epidural - drugs • Local anesthetics • Volume important to limit cranial spread of anesthetic • Must avoid hind limb ataxia (motor blockage) • Lidocaine 2% (6-8mL) in an adult horse is adequate for anus, perineum, rectum, vulva, vagina, urethra, bladder • Alpha-2 agonists • Xylazine, detomidine (common) • Causes local analgesia and systemic alpha-2 effects (sedation, 2nd degree AV block, ataxia, etc) • Side effects can be reversed with IV antagonist Equine epidural - drugs • Morphine • Provides analgesia • No risk of weakness or motor blockade • Hind limb trauma, surgery, severe laminitis • Side effects: urticaria, ileus • Often administered through epidural catheter for longer- term (days) analgesia Equine epidural • Epidural catheter • Inserted between Co1-Co2 space • Do not use local anesthetics – motor block • Analgesia for multiple days • If advanced to LS space – analgesia for hind limbs • Alpha-2 agonist + morphine – excellent analgesia Duque 2007 Intratesticular block • Anesthesia for castration • Horses, ruminants, swine • Under GA or sedation • Lidocaine volume • Horses – 20 mL • Small ruminants 2-5 mL • Quickly diffuses into the spermatic cord Lumb and Jones 2015 Ruminant eye • Retrobulbar block (A) – enucleation • Auriculopalpebral block (B) – examination of the eye Ruminant dehorning • Cattle • Cornual branch of zygomaticotemporal nerve (D) • Very painful procedure specially in adults Ruminant dehorning • Goats • Cornual branch of zygomaticotemporal nerve (1) • Cornual branch of infratrochlear nerve (2) • A ring block around the horn is commonly performed Lumb and Jones 2015 Ruminant flank laparotomy • Line block (infiltration) • Block SQ and muscular layers • LA injected along the incision line • Inverted L block (infiltration) • Injection remote from incision site • Caudal aspect of the last rib • Ventral aspect of the lumbar vertebrae transverse processes Ruminant flank laparotomy • Proximal paravertebral block • Dorsal and ventral branches of T13, L1 and L2/ inclusion of L3 provides better anesthesia • Injection site 3-5 cm from dorsal midline, majority of drug deposited at VENTRAL aspect • Signs of blockage: • Spinal scoliosis • Increased skin temperature • Absent reaction to pinprick Lumb and Jones 2015 Ruminant flank laparotomy • Distal paravertebral block • Dorsal and ventral branches of T13, L1 and L2 • Dorsal and ventral to transverse processes of L1, L2, and L4 • Majority of drug injected ventral to process Lumb and Jones 2015 Ruminant caudal epidural • Indications: obstetric manipulations and surgical procedures for tail, perineum, anus, rectum, vulva, vagina, prepuce, scrotum • Commonly and easily performed • Injection between S5-Co1 or Co1-Co2 space (A) • Drugs: local anesthetics, alpha-2 agonists, morphine Lumb and Jones 2015 Ruminant caudal epidural Ruminant lumbosacral epidural • Used in immature cattle, small ruminants, camelids, and pigs (caudal epidural preferred for adult cattle) • Will induce loss of motor function • Injection between L6-S1 • Similar technique as for dogs Lumb and Jones 2015 Anesthesia of the teats • To treat teat lacerations, remove polyps, others • Techniques • Ring block (A) • Inject distal to the tourniquet • Inverted V block (B) • Inject distal to the tourniquet • Teat cistern infusion (C) • Anesthesia of the mucous membranes • IV regional anesthesia of the teat (D) • Inject distal to the tourniquet Lumb and Jones 2015 Anesthesia of the udder • Paravertebral block of L1- L3 (1-4) • Cranial aspect of udder and teats • Pudendal block (5) • Caudal aspect of teats and udder Lumb and Jones 2015 Intravenous regional anesthesia (“Bier block”) • Foot is a common site of injury or disease • Similar than small animals Questions?