Turner and McIlwraith's Techniques in Large Animal Surgery E-Book

Dean A. Hendrickson

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 688

Veröffentlichungsjahr: 2013

Beschreibung

Turner and McIlwraith’s Techniques in Large Animal Surgery, Fourth Edition is an updated version of the classic resource for step-by-step instruction on basic surgical techniques in cattle, horses, swine, goats, and llamas. With detailed line drawings to demonstrate the principles discussed, the book addresses general aspects of surgery such as anesthesia and equipment and provides descriptions of surgical conditions and techniques commonly encountered in large animal practice. Now including a website with interactive review questions and the figures from the book in PowerPoint, the Fourth Edition is a highly practical, reliable guide for veterinary students and veterinary practitioners with a large animal caseload.

The Fourth Edition includes eight new techniques and completely rewritten chapters on anesthesia, equine wound management, and surgical techniques in bovine and swine patients, as well as revisions to reflect advances throughout the book and updated references. Turner and McIlwraith’s Techniques in Large Animal Surgery continues to supply students and practitioners alike with a valuable resource on the fundamental techniques of farm animal surgery.

Leseprobe

Table of Contents

Title page

Copyright page

About the Companion Website

Contributors

Preface to the First Edition

Preface to the Second Edition

Preface to the Third Edition

Preface to the Fourth Edition

Chapter 1: Presurgical Considerations

Preoperative Evaluation of the Patient

Surgical Judgment

Principles of Asepsis and Antisepsis

Surgical Classifications

Role of Antibiotics

Preoperative Planning

Preparation of the Surgical Site

Postoperative Infection

Chapter 2: Anesthesia and Fluid Therapy

Anesthesia

Fluid Therapy

Chapter 3: Surgical Instruments

Use of Surgical Instruments

Preparation of Instruments

Chapter 4: Suture Materials and Needles

Suture Materials

Needles

Chapter 5: Knots and Ligatures

Principles of Knot Tying

Ligatures

Chapter 6: Suture Patterns

Basic Suture Patterns

Suture Patterns Used for Closure of Hollow Organs

Stent Bandages (Tie-Over Dressings)

Suture Patterns for Severed Tendons

Chapter 7: Principles of Wound Management and the Use of Drains

Wound Management

Methods of Closure and Healing

Use of Drains

Chapter 8: Reconstructive Surgery of Wounds

Chapter 9: Equine Orthopedic Surgery

Medial Patellar Desmotomy

Lateral Digital Extensor Tenotomy

Inferior (Distal) Check Ligament Desmotomy

Superior Check Ligament Desmotomy (After Bramlage)

Superficial Digital Flexor Tenotomy

Deep Digital Flexor Tenotomy

Sectioning of the Palmar (or Plantar) Annular Ligament of the Fetlock

Palmar Digital Neurectomy

Amputation of the Splint (II and IV Metacarpal and Metatarsal) Bones

Arthrotomy of the Fetlock Joint and Removal of an Apical Sesamoid Chip Fracture

Chapter 10: Equine Urogenital Surgery

Castration

Cryptorchidectomy by the Inguinal, Parainguinal, and Flank Approach

Laparoscopic Cryptorchidectomy

Caslick's Operation for Pneumovagina in the Mare

Urethroplasty by Caudal Relocation of the Transverse Fold

Cesarean Section in the Mare

Circumcision of the Penis (Reefing)

Amputation of the Penis

Aanes' Method of Repair of Third-Degree Perineal Laceration

Chapter 11: Surgery of the Equine Upper Respiratory Tract

Tracheostomy

Laryngotomy, Laryngeal Ventriculectomy, and Ventriculocordectomy

Partial Resection of the Soft Palate

Surgical Entry and Drainage of the Guttural Pouches

Chapter 12: Equine Dental and Gastrointestinal Surgery

Repulsion of Cheek Teeth

Ventral Midline Laparotomy and Abdominal Exploration

Standing Flank Laparotomy

Umbilical Herniorrhaphy in the Foal

Chapter 13: Bovine Gastrointestinal Surgery

Principles of Laparotomy

Flank Laparotomy and Abdominal Exploration

Rumenotomy

Rumenostomy (Rumenal Fistulation)

Surgical Corrections of Abomasal Displacements and Torsion

Surgical Correction of Cecal Dilatation/Volvulus

Small Intestinal Resection and Anastomosis

Chapter 14: Bovine Urogenital Surgery

Calf Castration

Urethrostomy

Hematoma Evacuation of the Bovine Penis

Preputial Resection and Anastomosis in the Bull

Surgical Techniques for Teaser Bull Preparation

Inguinal Herniorrhaphy in the Mature Bull

Unilateral Castration

Cesarean Section in the Cow

Retention Suturing of the Bovine Vulva (Buhner's Method)

Cervicopexy for Vaginal Prolapse (after Winkler)

Chapter 15: Bovine General Surgery

Digit Amputation

Digit Amputation via Disarticulation

Eye Enucleation

Cosmetic Dehorning

Rib Resection and Pericardiotomy

Repair of Teat Lacerations

Third Eyelid Resection

Tracheotomy

Umbilical Surgery

Chapter 16: Small Ruminant Surgery

Dehorning the Mature Goat

Disbudding the Young Goat

Obstructive Urolithiasis

Mastectomy

Vasectomy

Cesarean Section

Rectal Prolapse Resection in Small Ruminants

Chapter 17: Camelid Surgery

Castration of the Llama

Cesarean Section in the Camelid

Tooth Removal in the Llama

Chapter 18: Swine Surgery

Castration of the Piglet

Inguinal Herniorrhaphy in the Piglet

Cryptorchid Castration of Piglets

Preputial Diverticulum Ablation

Cesarean Section in the Sow

Ovariohysterectomy in the Pot-Bellied Pig

Rectal Prolapse Ring Placement

Index

This edition first published 2013 © 2013 by John Wiley & Sons, Inc.

First and Second editions, © Lea & Febiger

Third edition, © Blackwell Publishing Ltd.

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Library of Congress Cataloging-in-Publication Data

Hendrickson, Dean A.

Turner and McIlwraith's techniques in large animal surgery. – 4th ed. / Dean A. Hendrickson, A.N. (Nickie) Baird.

p. ; cm.

Techniques in large animal surgery

Rev. ed. of: Techniques in large animal surgery / Dean A. Hendrickson. 3rd ed. c2007.

Includes bibliographical references and index.

ISBN 978-1-118-27323-4 (hardback : alk. paper) – ISBN 978-1-118-68399-6 (PDF) – ISBN 978-1-118-68404-7 – ISBN 978-1-118-68405-4 (Mobi) – ISBN 978-1-118-68429-0 – ISBN 978-1-118-68439-9

I. Baird, A.N. (Aubrey Nickie) II. Hendrickson, Dean A. Techniques in large animal surgery. III. Turner, A. Simon (Anthony Simon) Techniques in large animal surgery. IV. Title. V. Title: Techniques in large animal surgery.

[DNLM: 1. Surgery, Veterinary–methods. 2. Goats–surgery. 3. Horses–surgery. 4. Surgical Procedures, Operative–veterinary. 5. Swine–surgery. SF 911]

636.089'7–dc23

2013007056

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Cover design by Modern Alchemy LLC

About the Companion Website

This book is accompanied by a companion website:

www.wiley.com/go/hendrickson/techniques

The website includes:

Multiple Choice QuestionsPowerpoints of all figures from the book for downloading

Contributors

Dean A. Hendrickson, DVM, MS, DACVS

Editor-in-Chief

Colorado State University

College of Veterinary Medicine and Biomedical Sciences

Fort Collins, Colorado

A. N. (Nickie) Baird, DVM, MS, DACVS

Associate Editor

Purdue University

College of Veterinary Medicine

West Lafayette, Indiana

Khursheed Mama, DVM, DACVA

Colorado State University

College of Veterinary Medicine and Biomedical Sciences

Fort Collins, Colorado

Preface to the First Edition

The purpose of this book is to present some fundamen­­tal techniques in large animal surgery to both veterinary students and large animal practitioners. It is designed to be brief, discussing only the major steps in a partic­­ular operation, and each discussion is accompanied by appropriate illustrations. Most of the techniques presented in this book can be performed without the advantages of a fully equipped large animal hospital or teaching institution.

The book assumes a basic understanding of anatomy and physiology. Those who wish to know more about a particular technique are encouraged to consult the bibliography.

We and our colleagues at the Colorado State University Veterinary Teaching Hospital consider the procedures discussed in this book to be time honored. Some practitioners may perform certain techniques in slightly different ways. We would be happy to receive input about modifications of these techniques for future editions of this book.

All of the drawings in the book are original and based on rough sketches and photographs taken at various points during actual surgery. Occasionally, dissections were performed on cadavers.

The surgical procedures described in this text represent not only our thoughts, but suggestions from many of our colleagues as well. Their help was an important contribution to the production of this book. We are indebted to Dr. Wilbur Aanes, Professor of Surgery, Colorado State University, who unselfishly shared 30 years of his personal experience in large animal surgery with us. We are proud to be able to present in Chapter 10 of this book “Aanes' Method of Repair of Third-Degree Perineal Laceration” in the mare, a technique that he pioneered over 15 years ago. We also wish to give credit to the following faculty members at Colorado State University Veterinary Teaching Hospital who willingly gave us advice on the diagrams and manuscript of various techniques discussed in this book: Dr. Leslie Ball, Dr. Bill Bennett, Dr. Bruce Heath, Dr. Tony Knight, Dr. LaRue Johnson, Dr. Gary Rupp, Dr. Ted Stashak, Dr. Gayle Trotter, Dr. James Voss, and Dr. Mollie Wright. We also wish to express appreciation to Dr. John Baker, Purdue University, and Dr. Charles Wallace, University of Georgia, for their comments on some questions we had. Dr. McIlwraith is also grateful to Dr. John Fessler, Professor of Surgery, Purdue University, for his inspiration and training.

We are particularly grateful to Dr. Robert Kainer, Professor of Anatomy, Colorado State University, for checking the manuscript and the illustrations and advising us on nomenclature. His input impressed upon us the importance of the relationship between the dissection room and the surgery room.

The terrific amount of time and effort involved with the illustrations will be clear to the reader who cares only to leaf through the book. For these illustrations, we are indebted to Mr. Tom McCracken, Director, Office of Biomedical Media, Colorado State University. We are thankful for his expertise, as well as his cooperation and understanding. The diagrams for “Aanes' Method of Repair of Third-Degree Perineal Laceration” were done by Mr. John Daughtery, Medical Illustrator, Colorado State University. We must also thank Kathleen Jee, who assisted with various aspects of the artwork. We would also like to thank Messrs. Al Kilminster and Charles Kerlee for taking photographs during the various surgical procedures that were used to assist with the artwork of this text.

The manuscript was typed by Mrs. Helen Mawhiney, Ms. Teresa Repphun, and Mrs. Jan Schmidt. We thank them for their patience and understanding during the many changes we made during the generation of the final manuscript.

We are grateful to the following instrument companies for allowing us to use some of the diagrams from their sales catalogs for inclusion in Chapter 3, “Surgical Instruments”: Schroer Manufacturing Co., Kansas City, MO; Intermountain Veterinary Supply, Denver, CO; Miltex Instrument Co., Lake Success, NY; J. Skyler Manufacturing Co., Inc., Long Island, NY.

The idea for this book was conceived in 1978 when one of us (AST) was approached by Mr. George Mundroff, Executive Editor, Lea & Febiger. We would like to thank him for his encouragement and guidance. We are also grateful to Mr. Kit Spahr, Jr., Veterinary Editor; Diane Ramanauskas, Copy Editor; Tom Colaiezzi, Production Manager; and Samuel A. Rondinelli, Assistant Production Manager, Lea & Febiger, for their assistance, as well as to others at the Publisher who assisted in the production of this book.

A. Simon Turner

C. Wayne McIlwraith

Fort Collins, Colorado

Preface to the Second Edition

The second edition of Techniques in Large Animal Surgery is in response to the acceptance of the first edition and the continued need for such a book for both veterinary students and large animal practitioners. In many instances, the techniques are time honored and require no change from 5 years ago. In other instances, however, refinements in technique as well as improved perception of indications, limitations, and complications have made changes appropriate.

A significant change is the addition of Dr. R. Bruce Hull, Professor of Veterinary Clinical Sciences, The Ohio State University, as a contributor. He has carefully analyzed the entire bovine section, and his suggested changes and additions have been incorporated into the text. In addition, two procedures, “teaser bull preparations by penile fixation” and “treatment of vaginal prolapse by fixation to the prepubic tendon,” have been added. We are most grateful in having Dr. Hull's help and expertise. Among the introductory chapters, the section on anesthesia required the most updating, and we are grateful to our colleague Dr. David Hodgson at Colorado State University for his review and advice. Two new procedures, “superior check ligament desmotomy” and “deep digital flexor tenotomy,” were considered appropriate additions to this edition. We are grateful to Dr. Larry Bramlage, Ohio State University, for his comments and help with the first of these procedures. Many of the other changes in this edition are in response to the book reviews and comments on the first edition returned to Lea & Febiger. To these people, we appreciate your feedback.

A chapter on llama tooth removal was added because of the increased popularity of this species, especially in our own part of the country. Although we only discuss this one technique, it should not be inferred that other operations are unheard of in llamas. We have corrected angular limb deformities, repaired fractures, and performed gastrointestinal surgery, among other procedures, but tooth removal is the most common. Descriptions of these other procedures in llamas are beyond the scope of this book at this stage.

The need for more sophisticated equine techniques prompted us to produce the textbook Equine Surgery: Advanced Techniques in 1987. It is envisioned that the book will be used as a companion to this second edition, to provide a full spectrum of equine procedures, with the well-accepted format of concise text and clear illustrations.

Again, we are thankful to Mr. Tom McCracken, Assistant Professor, Department of Anatomy and Neurobiology, Colorado State University, for his talent in capturing the techniques described in his line drawings. We are also indebted to Helen Acvedo for typing our additions and to Holly Lukens for copyediting. Finally, our thanks again to the excellent staff at Lea & Febiger for the production of this edition.

A. Simon Turner

C. Wayne McIlwraith

Fort Collins, Colorado

Preface to the Third Edition

The first two editions of Techniques in Large Animal Surgery have been well accepted, much to the credit of Drs. Turner and McIlwraith. They have been excellent texts for the veterinary student and the large animal practitioner. I was fortunate to be able to take on the task when it came time to update the information for a third edition. I am deeply appreciative of the opportunity to take such an excellent text and update it with new information and techniques.

The third edition of Techniques in Large Animal Surgery has been updated in response to the continued need for such a book for both veterinary students and large animal practitioners. There are some techniques that are time tested and continue to be included. There are other techniques that have been refined or replaced, and these are included in the new text.

New information has been included in essentially every chapter. We have made extensive use of tables to simplify the information. The anesthesia section includes new and updated information on sedation and anesthetic agents. The instrument section has been evaluated, adding new instruments where applicable and removing outdated or unavailable instruments. The section on suture materials has been updated to include new materials. There are new illustrations in the suture pattern section to better aid the practitioner with surgical techniques. The sections on wound management and reconstructive surgery have been increased to provide up-to-date information on wound care. Tables of required instrumentation have been added to all sections of the remaining surgical chapters to aid in surgical planning and preparation.

I am very grateful for our new illustrator Anne Rains; she has done an excellent job and has made my life very easy. I am indebted to Joanna Virgin who has done the lion's share of the research to make sure this text was as up-to-date and accurate as possible. I could not have done this work without her. Thanks to the folks at Blackwell for their help and assistance in the production of this edition.

Dean A. Hendrickson

Fort Collins, Colorado

Preface to the Fourth Edition

The first two editions of Techniques in Large Animal Surgery have been well accepted much to the credit of Drs. Turner and McIlwraith. They have been excellent texts for the veterinary student and the large animal practitioner. I was fortunate in that when it came time to update the information for a third edition, I was able to take on the task; and now we have added a fourth edition.

The fourth edition of Techniques in Large Animal Surgery has been updated in response to the continued need for such a book for both veterinary students and large animal practitioners. As with the third edition, we have gone through the entire text to make sure the information was reliable. The “tried-and-true” procedures have been retained, the outdated procedures have been removed, and new procedures have been added. As we thoroughly researched each of the chapters in the text, we did a major overhaul of the references.

Probably the most important changes in this text are the addition of two authors. Nickie Baird joined me in co-authoring the fourth edition. His expertise in livestock animal surgery was a perfect fit for this textbook. He brings a great deal of new information to the text and has been a great partner. Dr. Khursheed Mama joined us as the author of Chapter 2, Anesthesia and Fluid Therapy. She did an excellent job updating all of the information.

We added a considerable amount of new information in the text and retained the table format to simplify information. New figures have been added, where needed, to support the updated information.

I am very grateful for Grahm Hendrickson for illustrating the new procedures, as well as Katie Hunsucker and Joy Fuhrman for providing a lot of the background research. Thanks as well to the folks at Wiley for their help and assistance in the production of this edition.

Dean A. Hendrickson

Fort Collins, Colorado

A. N. (Nickie) Baird

West Lafayette, Indiana

Chapter 1

Presurgical Considerations

Dean A. Hendrickson, DVM, MS, DACVS

Objectives

1. Discuss some of the presurgical considerations that can affect the success of a procedure, including the physiological state and condition of the patient; the predisposing factors for infection; and the limitations of the surgeon, facilities, and equipment.

2. Describe the methods of asepsis and antisepsis.

3. Describe the classification of different procedures with regard to risk of infection and degree of contamination.

4. Discuss the judicious use of antibiotics and their applications prophylaxis and postoperative infection.

5. Describe proper techniques for surgical site preparation.

Preoperative Evaluation of the Patient

Before a surgical procedure, a physical examination is generally indicated. This applies to both emergency and elective surgery. The following are laboratory tests that are generally indicated for horses based upon animal age and systemic status at our clinic:

For horses younger than 4 years old and healthy: Packed cell volume (PCV)Total proteinAppropriate for horses greater than 4 years old or those that are systemically ill: Complete blood count (CBC)Chemistry

Exactly where to draw the line on laboratory tests is largely a matter of judgment on the part of the surgeon. Obviously, if the surgery consists of castration of several litters of piglets, then for purely economic reasons laboratory tests prior to surgery may not be performed. In many cases, however, additional tests will be necessary. The following are examples of other optional tests and their indications:

Electrolyte measurement for right-sided abomasal diseases of the dairy cowUrinalysis in the dairy cow to evaluate the presence of ketosisMeasurement of blood urea nitrogen (BUN) and creatinine if urinary problems are suspectedAnalysis of peritoneal fluid prior to laparotomy for horses with colicFull chemistry panels when there are age or systemic considerations

If any laboratory parameters are abnormal, the underlying causes should be investigated and efforts made to correct them. In “elective” surgery this is possible, but it may not be possible in an emergency. The owner should be made aware of any problems prior to subjecting the animal to surgery. Risks are always present in normal elective surgery, and these should be explained to the owner. It is always better to have an early, frank discussion with the owner about the possible risks associated with the surgery than to have the discussion after the risk has been realized.

Fluid replacement should be performed if necessary. In the elective case, the surgical procedure should be postponed if the animal's physical condition or laboratory parameters are abnormal. In some animals, internal and external parasitism may have to be rectified to achieve this goal.

Medical records should be kept at all times. Obviously this can be difficult in such cases as castration of several litters of piglets. However, record keeping should become an essential part of the procedure for horses and cattle in a hospital, and herd records should be kept in all other situations. Finally, if the animal is insured, the insurance company must be notified of any surgical procedure; otherwise, the policy may be void.

Surgical Judgment

Surgical judgment cannot be learned overnight by reading a surgery textbook, nor is it necessarily attained by years of experience. The surgeon who continually makes the same mistake will probably never possess good surgical judgment. Not only should the surgeon learn from his own mistakes; he also should learn from the mistakes of others, including those documented in the surgical literature. As part of surgical judgment, the surgeon must ask the following questions:

Is the surgery necessary?What would happen if the surgery were not performed?Is the procedure within the capabilities of the surgeon, the facilities, and the technical help?

If the surgeon finds that the procedure is too advanced for his or her capabilities and/or facilities, the surgery should be referred. Some veterinarians have a fear that this will mean loss of the client's business in the future, but this is rarely the case. If the surgeon explains why the case should be referred elsewhere, most clients will be grateful for such frankness and honesty. It is inexcusable to operate on a patient and then have complications arise due to inadequate training and facilities, when the surgery could easily have been referred to a well-equipped, well-staffed hospital with specially qualified personnel. Clearly, this rule has exceptions—mainly the emergency patient, which may fare better by undergoing immediate surgery than being subjected to a long trailer ride to another facility.

Many of the procedures described in this book can be done “on the farm.” Some, such as arthrotomy for removal of chip fractures of the carpal and sesamoid bones in horses, should be done in a dust-free operating theater. If clients want these latter procedures to be done “in the field,” they should understand the disastrous consequences of postsurgical infection. The surgeon must be the final judge of whether his facilities or experience are suitable.

Principles of Asepsis and Antisepsis

There are four main determinants for a surgical site infection (SSI): host defense, physiologic derangement, bacterial contamination risk at surgery, and prolonged surgical time.1Other factors that impact infection of deep structures and organs include hypoalbuminemia and a prior operation.2 Perioperative blood loss also contributes to SSI.3 Control methods include aseptic surgical practices as well as identification of the high-risk patient, correction of systemic imbalances prior to surgery, and the proper use of prophylactic antibiotics.

We are sometimes reminded by fellow veterinarians in the field that we must teach undergraduates how to do surgery in the real world. By this they mean that we must ignore aseptic draping and gloving and lower the standard to a “practical” level. This is fallacious in our opinion. Although we recognize that while the ideal may be unattainable in private practice, one should always strive for the highest possible standard; otherwise, the final standard of practice may be so low that the well-being of the patient is at risk, not to mention the reputation of the veterinarian as a surgeon. For this reason, we believe that it behooves us as instructors of undergraduates to teach the best possible methods with regard to asepsis as well as technique.

The extent to which the practice of asepsis or even antisepsis is carried out depends on the classification of the operation, as shown in Table 1.1. This classification may also help the veterinarian decide whether antibiotics are indicated or whether postoperative infection can be anticipated.

Table 1.1. Surgical classifications.

ClassificationDescriptionExamplesCleanGastrointestinal, urinary, or respiratory tract is not entered.Arthrotomy for removal of a chip fracture of a carpal bone of a horseClean-contaminatedGastrointestinal, respiratory, or urinary tract is entered. There is no spillage of contaminated contents.Abomasopexy for displaced abomasum in the dairy cowContaminated-dirtyGross spillage of contaminated body contents or acute inflammation occurs.WoundsAbscessesDevitalized bowel

Surgical Classifications

Once the surgeon has categorized the surgical procedure, appropriate precautions to avoid postoperative infection can be determined. In all cases, however, the surgical site is prepared properly, including clipping and aseptic scrubbing.

Whatever category of surgery is performed, clean clothing should be worn. The wearing of surgical gloves is good policy even if only to protect the operator from infectious organisms that may be present at the surgical site. Surgical gowns, gloves, and caps are recommended for clean surgical procedures, although such attire has obvious practical limitations for the large animal surgeon operating in the field. The purpose of this book is to present guidelines rather than to lay down hard-and-fast rules. For example, the decision between wearing caps, gowns, and gloves and wearing just gloves can be made only by the surgeon. Good surgical judgment is required. In general, it is better to be more careful than what may appear necessary in order to be better prepared when problems arise.

Role of Antibiotics

Antibiotics should never be used to cover flaws in surgical technique. The young surgeon is often tempted, sometimes under pressure from the client, to use antibiotics prophylactically. However, the disadvantages of antimicrobial therapy often outweigh its benefits. Extended periods of antimicrobial therapy can select for resistant organisms and adversely affect the gastrointestinal tract by eliminating many of the normal enteric organisms and allowing outgrowths of pathogenic bacteria, such as Clostridia spp., which can result in colitis and diarrhea.4 When selecting an antibiotic regimen, the surgeon should consider the following aspects:

Does the diagnosis warrant antibiotics?Which organisms are most likely to be involved, and what is their in-vitro antimicrobial susceptibility?What is the location or likely location of the infection?How accessible is the location of the infection to the drug?What possible adverse reactions and toxicities to the drug could occur?What dosage and duration of treatment are necessary to obtain sufficient concentrations of the drug?

Again, some judgment is required, but suffice it to say, antibiotics should never be substitutes for “surgical conscience.” Surgical conscience consists of the following: dissection along tissue planes, gentleness in handling tissues, adequate hemostasis, selection of the best surgical approach, correct choice of suture material (both size and type), closure of dead space, and short operating time.

If the surgeon decides that antibiotics are indicated, special attention should be given to selecting the type of antimicrobial drug, the dosage, and the duration of use. Ample scientific literature indicates that for maximum benefit, antimicrobials should be administered prophylactically prior to surgery and, at the latest, during surgery. Beyond 4 hours postsurgically, the administration of prophylactic antibiotics has little to no effect on the incidence of postoperative infection.1 The duration of treatment should not exceed 24 hours because most research indicates that antimicrobial use after this period of time does not confer further benefits. If longer duration of antimicrobial coverage is necessary, the full duration of the specific antimicrobial drug selected should be given. This varies depending on the drug; however, in most cases the duration is at least 3 and up to 5 days. If the surgeon is operating on a food animal, there are regulations for withdrawal times from different antimicrobial drugs prior to slaughter that must be taken into account.

If topical antibiotics are used during surgery, they should be nonirritating to the tissues; otherwise, tissue necrosis from cellular damage will outweigh any advantageous effects of the antibiotics. It is also beneficial when using topical antibiotics to use antibiotics that are not generally used systemically.

All equine surgical patients should have tetanus prophylaxis. If the immunization program is doubtful, the horse can receive 1500–3000 units of tetanus antitoxin. Horses on a permanent immunization program that have not had tetanus toxoid within the previous 6 months should receive a booster injection.

Tetanus prophylaxis is generally not provided for food animals, but an immunization program may be considered, especially if a specific predisposition is thought to exist.

Preoperative Planning

The surgeon should be thoroughly familiar with the regional anatomy. In this book we illustrate what we consider to be the important structures in each technique. If more detail is required, a suitable anatomy text should be consulted. Not only should the procedure be planned prior to the surgery, but the surgeon also should visit the dissection room and review local anatomy on cadavers prior to attempting surgery on a client's animal. We are fortunate in veterinary surgery to have greater access to cadavers than our counterparts in human surgery.

Preparation of the Surgical Site

For the large animal surgeon, preparation of the surgical site can present major problems, especially in the winter and spring when farms can be muddy. Preparation for surgery may have to begin with removal of dirt and manure. Some animals that have been recumbent in mud and filth for various reasons may have to be hosed off. Hair should then be removed, not just from the surgical site, but from an adequate area surrounding the sur­­gical site.

The clipping should be done in a neat square or rectangular shape with straight edges. Surprisingly, this, along with the neatness of the final suture pattern in the skin, is how the client judges the skill of the surgeon. Clipping may be done initially with a no. 10 clipper blade, and then the finer no. 40 blade may be used. The incision site can be shaved with a straight razor in horses and cattle, but debate exists regarding the benefit or problems associated with this procedure. In sheep and goats, in which the skin is supple and pliable, it is difficult to shave the edges.

Preparation of the surgical site, such as the ventral midline of a horse about to undergo an exploratory laparotomy, may have to be performed when the animal is anesthetized. If surgery is to be done with the animal standing, an initial surgical scrub, followed by the appropriate local anesthetic technique and a final scrub, is standard procedure.

For cattle or pigs, the skin of the surgical site can be prepared for surgery with the aid of a stiff brush. For horses, gauze sponges are recommended. Sheep may require defatting of the skin with alcohol prior to the actual skin scrub. The antiseptic scrub solution used is generally a matter of personal preference. Either povidone-iodine scrub (Betadine Scrub) alternated with a 70% alcohol rinse, or Chlorhexidine alternated with water, can be used. Finally, the skin can be sprayed with povidone-iodine solution (Betadine Solution) and allowed to dry.

Scrubbing of the proposed surgical site is done immediately prior to the operation. Scrubbing should commence at the proposed site of the incision and progress toward the periphery; one must be sure not to come back onto a previously scrubbed area. Some equine surgeons clip and shave the surgical site the night before the surgery, perform an aseptic preparation as previously described, and wrap the limb in a sterile bandage until the next day. A shaving nick made the day before surgery may be a pustule on the day of surgery, however, so this is generally not recommended for anything proximal to the pastern region.

When aseptic surgery is to be performed, an efficient draping system is mandatory. Generally, time taken to drape the animal properly is well spent. The draping of cattle in the standing position can be difficult, especially if the animal decides to move or becomes restless. It can be difficult to secure drapes with towel clamps in the conscious animal because only the operative site is anesthetized. However, if the surgeon applies slow pressure when closing the towel clamps, most animals will tolerate their application, even if the local site is not desensitized. If draping is not done, the surgeon must minimize contact with parts of the animal that have not been scrubbed. The tail must be tied to prevent it from flicking into the surgical field.

Several operations described in this book require the strictest of aseptic technique; sterile, antimicrobial, adhesive, incise drapes are indicated. Characteristics of sterile plastic adhesive drapes include their ability to adhere, their antimicrobial activity, and their clarity when applied to the skin. Probably the most desirable feature is the one first mentioned. With excessive traction or manipulation, some brands of drapes quickly separate from the skin surfaces, and this separation instantly defeats their purpose.

Rubberized drapes are helpful when large amounts of fluids (such as peritoneal and amniotic fluid) are encountered during the procedure. Rubberized drapes are also useful to isolate the bowel or any other organ that is potentially contaminated, to prevent contamination of drapes. Newer fluid-impermeable paper drapes that are disposable make the surgeon's job even easier.

Postoperative Infection

Prevention of postoperative infection should be the goal of the surgeon, but infection may occur despite all measures taken to prevent it. If infection occurs, the surgeon must decide whether antibiotic treatment is indicated, or whether the animal is strong enough to fight it using its own defense mechanisms. Some surgical wounds require drainage at their most ventral part, whereas others require more aggressive treatment. If, in the judgment of the surgeon, the infection appears to be serious, a Gram stain, culture, and sensitivity testing of the offending microorganism(s) will be indicated. A Gram stain may give the surgeon a better idea of what type of organism is involved and may in turn narrow the selection of antibiotics. Sometimes in-vitro sensitivities have to be ignored because the antibiotic of choice would be prohibitively expensive. This is especially true for adult cattle and horses. A broad-spectrum antibiotic should be given, if possible, as soon as practical.

References

1. Barie, P.S. Modern surgical antibiotic prophylaxis and therapy—less is more. Surgical Infections, 1:23–29, 2000.

2. Haridas, M., and Malangoni, M.A. Predictive factors for surgical site infection in general surgery. Surgery, 144:496–503, 2008.

3. Sorensen, L.T., Hemmingsen, U., Kallehave, F., Wille-Jorgensen, P., Kjoergaard, J., Moller, L.N., and Jorgensen, T. Risk factors for tissue and wound complications in gastrointetstinal surgery. Annals of Surgery, 241:654–658, 2005.

4. Papich, M.G. Antimicrobial therapy for gastrointestinal disease. The Veterinary Clinics of North America. Equine Practice, 19:645–663, 2003.

Chapter 2

Anesthesia and Fluid Therapy

Khursheed Mama, DVM, DACVA

Objectives

1. Describe routine regional anesthetic techniques in large animals.

2. Discuss selected species differences in reference to anesthetic techniques.

3. Describe the indications for, advantages of, and disadvantages of general anesthesia in large animal species.

4. Provide a basic discussion of the fundamentals of fluid therapy including methods for ascertaining fluid deficits, acid-base imbalances, and electrolyte abnormalities.

5. Discuss specific fluid therapies in patients undergoing elective surgery and in compromised patients, either with or without preliminary data.

Anesthesia

The purpose of this section is not to present an in-depth discussion of all aspects of anesthesia. Details on the principles of anesthesia, recognition of stages of anesthesia, monitoring during anesthesia, and the pharmacology and physiology associated with anesthesia are well documented in other texts.1–3 Rather, information pertaining to routinely used anesthetic techniques for large animals is provided. The interested reader is referred to additional sources for more in depth information.4,5

Local and Regional Anesthesia (Analgesia)

Regional anesthesia results from desensitization of sensory nerves to a given area. This may be performed by infiltration into the desired location or by “blocking” sensory nerve(s) innervating a region. Both techniques may be used to desensitize the surgical site. Depending on the required duration of anesthesia, local anesthetic agents including lidocaine hydrochloride (shortest onset and duration), mepivacaine hydrochloride and bupivacaine hydrochloride (longest onset and duration) may be used. Due to cardiovascular toxicity with vascular absorption, bupivacaine use is usually limited to epidural and perineural administration; lidocaine and mepivacaine may be used by any route. Mepivacaine is often selected because of its rapid onset, intermediate duration, and reduced tissue reactivity.6

Regional anesthesia techniques are still commonly used as primary means to facilitate noxious intervention in many ruminant species. Sedation may be used as an adjunct. In horses, while these techniques may be used in sedated patients, they are also commonly used as adjuncts to general anesthesia. A description of selected regional anesthesia techniques follows.