Veterinary surgery Study Guide

📖 Core Concepts Surgical categories – Orthopaedic: bones, joints, muscles; Soft‑tissue: skin, cavities, cardiovascular, GI/uro‑respiratory tracts; Neurosurgery: nervous system. Local anesthetics – Lidocaine, mepivacaine, bupivacaine (short‑, intermediate‑, long‑acting). α₂‑adrenergic agonists – Xylazine & medetomidine produce sedation/analgesia; reversible with yohimbine (xylazine) or atipamezole (medetomidine). General anesthesia workflow – Induction → endotracheal intubation → inhalant maintenance. Castration methods – Cord ligation, rubber band (ischemia), Burdizzo crushing. Joint replacement & arthroscopy – Advanced orthopaedic options for severe OA or trauma, performed minimally invasively. Oncologic surgery – Simple excision vs reconstructive plastic surgery; wide margins for oral malignancies. Laser surgery advantage – Less bleeding, infection, pain, swelling. --- 📌 Must Remember Induction agents Dogs/Cats: thiopental, ketamine + diazepam, tiletamine‑zolazepam, propofol, alfaxalone. Horses: thiopental + guaifenesin. Inhalants – Isoflurane, enflurane, halothane (traditional); desflurane, sevoflurane (rapid on/off). Reversal agents – Yohimbine ↔ xylazine; atipamezole ↔ medetomidine. Sterilization – Spaying = ovariectomy or ovario‑hysterectomy; castration = orchiectomy. Common skin tumors – Lipoma, mast cell tumor, melanoma, SCC, basal cell, fibrosarcoma, histiocytoma. Cranial cruciate ligament (CCL) repair – Restores knee stability; most common orthopaedic case. Bloat (GDV) surgery – De‑tension stomach, perform gastropexy to prevent recurrence. --- 🔄 Key Processes General Anesthesia (Dog/Cat) Pre‑oxygenate → Induction with chosen agent. Verify jaw relaxation, loss of reflexes. Endotracheal intubation (visualize cuff, secure tube). Initiate inhalant (e.g., isoflurane) via vaporizer. Adjust vaporizer to maintain appropriate plane (monitor HR, BP, reflexes). Castration (General steps) Restrain animal, aseptic prep. Make scrotal incision, exteriorize testis. Apply chosen method: Ligation: Tie spermatic cord, cut distal cord. Rubber band: Place band proximal to testis, allow ischemic necrosis. Burdizzo: Crush cord for 30 s, then excise testis. Close incision or leave open (species dependent). Cranial Cruciate Ligament Repair Arthrotomy/arthroscopy to visualize joint. Remove damaged ligament remnants. Place tibial plateau‑leveling osteotomy (TPLO) or tibial tuberosity advancement (TTA) plate/screw construct. Verify stability, close joint capsule, suture skin. GDV (Bloat) Surgery Midline laparotomy, locate stomach. Deflate gastric gas (needle or suction). Re‑position stomach (untwist if volvulus). Perform gastropexy (right‑side gastropexy or tube‑gastropexy). Close abdomen, monitor for reperfusion injury. --- 🔍 Key Comparisons Lidocaine vs Bupivacaine Lidocaine: rapid onset, short duration. Bupivacaine: slower onset, prolonged analgesia. Xylazine vs Medetomidine Xylazine: reversed by yohimbine. Medetomidine: reversed by atipamezole. Castration methods Ligation: immediate hemostasis, requires suturing. Rubber band: no suturing, delayed necrosis (3‑5 days). Burdizzo: no suture, minimal tissue handling, risk of incomplete cord crush. Induction in Dogs/Cats vs Horses Dogs/Cats: multiple agents (propofol, ketamine combos). Horses: thiopental + guaifenesin (muscle relaxation). Laser vs Scalpel surgery Laser: less bleeding, infection, postoperative pain. Scalpel: cheaper, widely available, more intra‑operative bleeding. --- ⚠️ Common Misunderstandings All α₂‑agonists reverse with the same drug – Only xylazine ↔ yohimbine; medetomidine ↔ atipamezole. “Desflurane = faster recovery for every species” – True for dogs/cats; horses often use isoflurane due to equipment limits. Every fracture needs internal fixation – Some are adequately treated with casting or external fixation. Laser surgery eliminates the need for anesthesia – Most laser procedures still require general or deep sedation for safety. Spaying = only removal of ovaries – Can also include uterine removal (ovario‑hysterectomy). --- 🧠 Mental Models / Intuition Anesthesia depth = volume knob – Turn up (more inhalant) = deeper plane; watch reflexes as the “meter.” Cranial cruciate ligament as a door hinge – Damage = door swings open → repair re‑locks the hinge. Rubber‑band castration = “tourniquet” – Think of cutting off blood flow, letting the tissue auto‑necrose. Laser = “cold scalpel” – Energy cuts while simultaneously cauterizing, reducing “wet” mess. --- 🚩 Exceptions & Edge Cases Ruminants – Prefer regional anesthesia over inhalants for many surgeries. Horses – Thiopental induction may be combined with guaifenesin for muscle relaxation; not typical in small animals. Medetomidine reversal – Only atipamezole is effective; yohimbine will not reverse medetomidine. Laser surgery – Limited to superficial or well‑vascularized tissues; deep bone work still requires conventional tools. --- 📍 When to Use Which Choose induction agent Propofol: rapid induction, short recovery – ideal for short procedures. Ketamine + diazepam: good analgesia, useful in patients where cardiovascular depression must be minimized. Alfaxalone: smooth induction, minimal respiratory depression – good for compromised patients. Select castration technique Ligation: when immediate hemostasis is critical (large breeds). Rubber band: field castration, limited equipment. Burdizzo: when suturing is undesirable (wildlife, feral cats). Use laser surgery For superficial skin tumors, gingival hyperplasia, or when minimizing postoperative pain is a priority. Decide on minimally invasive vs open Arthroscopy/laparoscopy: when joint or abdominal cavity visualization is needed with less morbidity. Open surgery: for large masses, complex fractures, or when extensive reconstruction is required. --- 👀 Patterns to Recognize Skin tumor list – lipoma → soft, mobile; mast cell → variable ulceration; melanoma → dark pigmented mass. GDV presentation – distended abdomen, non‑peristaltic gas, rapid deterioration → immediate surgery needed. Cranial cruciate tear – “drawer sign” on tibial thrust, effusion, lameness that worsens with activity. Laser cases – minimal intra‑operative bleeding, clear vapor plume, reduced postoperative swelling. Anesthetic recovery – rapid, smooth emergence → likely desflurane or sevoflurane; sluggish emergence → halothane or high isoflurane concentration. --- 🗂️ Exam Traps Reversal agent mix‑up – Choosing yohimbine for medetomidine reversal is wrong; the correct answer is atipamezole. Assuming all dogs receive propofol induction – Many protocols use thiopental or ketamine combos; the exam may list propofol as “most common” but not exclusive. Confusing spay types – “Ovariectomy” vs “ovario‑hysterectomy”; both are spaying, but the latter includes uterus removal. Laser surgery eliminates all bleeding – It reduces but does not completely abolish bleeding; some cases still require hemostasis. All fractures need internal fixation – Some simple transverse fractures in small animals are adequately managed with casting; choosing internal fixation for every fracture is a distractor. ---