Preface to first edition A i OXFORD MEDICAL PUBLICATIONS Operative Surgery ii Oxford University Press makes no representation, express or implied, that the drug dosages in this book are correct. Readers must therefore always check the product information and c linical procedures with the most up-to-date published product information and data sheets p rovided by the manufacturers and the most recent codes of conduct and safety regulations. T he authors and the publishers do not accept responsibility or legal liability for any error s in the text or for the misuse or misapplica- tion of material in this work. iii Operative Surgery Second edition Edited by Greg R. McLatchie Professor of Sports Medicine and Surgical Sciences, University of Sunderl and, UK David J. Leaper Emeritus Professor of Surgery, University of Newcastle upon Tyne, UK iv Great Clarendon Street, Oxford OX2 6DP Oxford University Press is a department of the University of Oxford. It furthers the Univer sity \200\231s objective of excellence in research, scholarship, and education by publishin g worldwide in Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melb ourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hunga ry Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vi etnam Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York Oxford University Press 2006 The moral rights of the authors have been asserted Database right Oxford University Press (maker) First edition published 1996 Reprinted 1998, 2001, 2002 Second edition published 2006 All rights reserved. No part of this publication may be reproduced, stored in a retrieval s ystem, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, or under terms agreed with t he appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, a t the address above You must not circulate this book in any other binding or cover and you must impose the same condition on any acquirer British Library Cataloging in Publication Data Data available Library of Congress Cataloging in Publication Data Data available Typeset by Newgen Imaging Systems (P) Ltd., Chennai, India Printed in Italy on acid-free pa per by Legoprint S.p.A. ISBN 0 \200\22319 \200\223851056 \200\223X (flexicover: alk.paper) 978 \200\2230 \200\22319 \200\223851056 \200\2237 (flexicover: alk.paper) 10 9 8 7 6 5 4 3 2 1 v Preface to first edition This book is a practical guide for the surgeon or surgical trainee about to perform or assi st at an operation. The procedures described are those commonly carried out in general, uro logical, and orthopedic surgical practice with an introduction on perioperative management and anaes- thetics. These should also prove of interest to operating department nurses, ass istants, and students of medicine. Indications for and complica- tions of procedures are gi ven but more extensive descriptions of these can be found in surgical text books to which t he reader should refer. We emphasize that the book is not for the first-time operator nor does it embrace the philo sophy of \200\230see one, do one, teach one \200\231. Anyone aspiring to be a surgeon must acquire the basic skills of safe knot-tying and familiarity with surgical instruments. Onl y by witnessing, assisting at, and then performing many procedures within the structure of a formal surgical training course can the trainee develop the skill, judgment, and the abil ity to select patients correctly \200\224the recipe for safe surgery. GRM Hartlepool DJL Stockton on Tees 1996 Preface to second edition The text and increased numbers of contributors reflect the changes that have occurred in Ge neral Surgery over the past ten years. It is unlikely that in the future we will encounter General Surgical Units. They will be replaced by specialized departments catering for speci fic areas of surgical expertise. These changes will also fashion future editions of this te xt in that almost every chapter will become a handbook in itself and the train- ing of surg eons become significantly changed. GRM DL North Tees and Hartlepool NHS Trust April 2006 vi Dedications For Ross, Cameron, Ailidh, Claire, Calum, Charles, Alice, Stephen, Rebecca, and Amy vii Acknowledgements We are grateful to all who have helped us to produce this book, in particular the staff of Oxford University Press. We thank Luca Di Franco for some of the illustrations and Paul Rod gers who took photographs. Staff on the Surgical Wards at the University Hospital of Hartle pool; Debbie Blackwood, Dean Trainer, Nicola Jones and Elizabeth Redden, deserve special me ntion, as does Anneli Thornton who prepared the manuscript. This page intentionally left blank ix Contributors Mr A. K. Agarwal Consultant Surgeon, North Tees & Hartlepool NHS Trust Mr T. Friesem Consultant Spinal Surgeon, North Tees & Hartlepool NHS Trust Mr S. Aspinall Specialist Registrar, Northern Deanery Mr A. Gilliam Specialist Registrar, Northern Deanery Professor B. S. Avery Consultant Oral & Maxillofacial Surgeon, James Cook University Hospit al, Middlesbrough Mr C. Harding Consultant Urologist, North Tees & Hartlepool NHS Trust Mr R. Carter Lister Department of Pancreatico-biliary surgery, Glasgow Royal Infirmary Mr L. Horgan Consultant Surgeon, Upper GI and Laproscopic Surgical Unit, North Tyneside Gen eral Hospital Mr A. E. Clason Consultant Vascular Surgeon, James Cook University Hospital, Middlesbrough Professor C. W. Imrie Lister Department of Pancreatico-biliary Surgery, Glasgow Royal Infir mary Mr F. Di Franco Specialist Registrar, Northern Deanery Dr P. Kalia Consultant Anesthetist, North Tees & Hartlepool NHS Trust A. J. Dickenson Consultant Maxillofacial Surgeon Mr. S. Dresner Consultant Surgeon, James Cook University Hospital, Middlesbrough Mr V. J. Kurup Consultant Surgeon, North Tees & Hartlepool NHS Trust Mr H. El-Khalifa Associate Specialist, North Tees & Hartlepool NHS Trust Mr Q. King Consultant Urologist, North Tees & Hartlepool NHS Trust Mr M. El-Sheik Consultant Surgeon, Nottingham City Hospital NHS Trust x CONTRIBUTORS Contributor Professor David J. Leaper Emeritus Professor of Surgery, North Tees & Hartlepoo l NHS Trust Mr P. Raine Royal Hospital for Sick Children, Glasgow Mr S. Rawat Upper GI and Laparoscopic Surgical Unit, North Tyneside General Hospital Mr P. A. Lear Consultant Vascular and Transplant Surgeon, North Bristol NHS Trust Mr C. M. S. Royston Department of General Surgery, Hull Royal Infirmary Professor T. Lennard School of Surgical and Reproductive Sciences, Newcastle upon Tyne Mr J. Shenfine Specialist Registrar Professor G. R. McLatchie Consultant Surgeon, North Tees & Hartlepool NHS Trust Mr D. Southward Consultant in Accident & Emergency, North Tees & Hartlepool NHS Trust Dr D. Monkhouse Specialist Registrar, Anesthetics, Northern Deanery Mr Y. K. S. Visnarath Consultant Surgeon, James Cook University Hospital, Middlesbrough A. N. Morritt Consultant Cardiothoracic Surgeon, James Cook University Hospital, Middlesbro ugh Mr G. Walker Specialist Registrar in Pediatric Surgery, Glasgow Mr G. O \200\231Dair Specialist Registrar Northern Deanery xi Contents Symbols and abbreviations xii 1 Perioperative anesthetic care and practical procedures 1 2 Theater procedures and prophylaxis 29 3 Anatomy for surgeons 45 4 Surgical instruments, materials, and the acquisition of surgical skills 91 5 Breast and endocrine surgery 147 6 Upper gastrointestinal surgery 185 7 Colorectal surgery, appendix, and small bowel 225 8 Hepatobiliary surgery 305 9 Laparoscopic surgery 323 10 Stapling in surgery 351 11 Hernias 367 12 Peripheral vascular surgery 379 13 Urology 475 14 Pediatric surgery 567 15 Head and neck surgery 639 16 Thoracic surgery 691 17 Principles of plastic surgery 759 18 Trauma surgery 813 19 Transplantation 833 Index 857 xii Symbols and abbreviations > < greater than less than increased (cid:165) decreased (cid:160) and/or (cid:183) \211 greater than or equal to accident and emergency airway, breathing, circulation Association of the British Pharmaceutical Industry angiotensin-converting enzyme adrenocorticotropic ho rmone aerobic Gram-negative bacilli American Joint Committee on Cancer abdomino-perineal ex cision antiphospholipid antibody syndrome activated partial thromboplastin time ratio acute respiratory distress syndrome American Society for Information Science or anterior superio r iliac spine advanced trauma life support below knee amputation body mass index beats per minute balanitis xerotica obliterans chronic beryllium disease congestive cardiac failure C oronary Care Unit congenital diaphragmatic hernia Creutzfeld \200\223Jakob disease cytomega lovirus central nervous system or coagulase negative staphylococcus congenital diaphragmati c hernia chronic renal failure A&E ABC ABPI ACE ACTH AGNB AJCC APE APLS APTTR ARDS ASIS ATLS BKA BMI Bpm BXO CBD CCF CCU CDH CJD CMV CNS COH CRF xiii SYMBOLS AND ABBREVIATIONS CSF CT CVP CXR DGF DJ DPL DVT EBV ECG EHL EMLA ENT ERCP ESWL EUA EUS FBC FEV1 FHL cerebrospinal fluid computed tomography central venous pressure chest X-ray delayed graft f unction duodenal-jejunal diagnostic peritoneal lavage deep vein thrombosis Epstein \200\223 Barr virus electrocardiogram extensor hallucis longus entectic mixture of local anesthetic ear, nose, throat endoscopic retrograde cholangio-pancreatography extracorporeal shockwave lithotripsy examination under anesthetic endoscopic ultrasound full blood count forced expi ratory volume (in 1 second) familial erythrophagocytic lymphohistiocytosis or flexor halluc is longus fine needle aspiration cytology forced expiratory vital capacity gastrooesophagea l reflux disease gastro-jejunal glucose/potassium/insulin gastro-oesophageal junction Great Ormond Street history and physical examination high dependency unit Haemophilus influenza type b human immunodeficiency virus human leucocyte antigen hormone replacement therapy her pes simplex virus intensive care unit interleukin 1 intramuscular FNAC FVC GERD GJ GKI GOJ GOS H&P HDU Hib HIV HLA HRT HSV ICU IL-1 IM xiv SYMBOLS AND ABBREVIATIONS IMA IMV INR IPF IPMT ITU IVC JVP kPa LES LFT LIF LMU LMWH LOS LSV LUS MAO-A MI MIBG MIBI MI DN MITS MOA MRCP MRI MRSA NG NHB OA OGD OTE PAC PAIs PAK PALS PCA inferior mesenteric artery inferior mesenteric vein international normalized ratio initial poor function intraductal papillary mucinous tumor intensive therapy unit inferior vena cav a jugular vein catheterization kilo Pascals lower esophageal sphincter liver function tests left iliac fossa lower, middle, upper low molecular weight heparin lower oesophageal sphin cter long saphenous vein laproscopic ultrasonography monoamine oxidase A myocardial infarct ion meta iodo benzyl guanidine myocardial perfusion imaging minimally invasive donor nephre ctomy minimally invasive thoracoscopic splanchnicectomy monoamine oxidase inhibitors magnet ic resonance cholangio-pancreatography magnetic resonance imaging methicillin-resistant Sta phylococcus aureus naso-gastric non-heart beating oesophageal atresia oesophagogastroduoden oscopy otitis media with effusion pulmonary artery catheterization plasminogen activator in hibitor pancreas after kidney pediatric advanced life support patient-controlled analgesia xv SYMBOLS AND ABBREVIATIONS PCNL PE PEEP per anum PNF PONV PPPD PSARP PT PTA PTFE PTH PTLD PTT PUJ PVC RA RCC RI RIF RI ND RSTL rTPA SAGB SEPS SFA SMA SMV SPK SSRIs SSSI SVC TAPP TB TBSA TCC TED percutaneous nephrolithotomy pulmonary embolism positive end expiratory pressure though the anus primary non-function postoperative nausea and vomiting pylorus preserving pancreatico -duodenectomy posterior sagittal anorectoplasty prothrombin time pancreas transplantation a lone polytetrafluoroethylene parathormone post-transplant lymphoproliferative disease parti al thromboplastin time pelviureteric junction polyvinylchloride right atrium renal cell car cinoma resistance index right iliac fossa reversible ischaemic neurological deficit relaxed skin tension line recombinant tissue plasminogen activator Swedish adjustable gastric band subfascial endoscopic perforator surgery superficial femoral artery superior mesenteric ar tery superior mesenteric vein simultanous pancreas-kidney selective serotonin reuptake inhi bitors superficial surgical site infection superior vena cava transabdominal preperitoneal tuberculosis total body surface area transitional cell carcinoma thromboembolic deterrent xvi SYMBOLS AND ABBREVIATIONS TEP TNF TOF TOR tPA streetcar TURBT TURP U ULTRA UTI UVPPP VATS VT YAG totally extraperitoneal tumor necrosis factor tetralogy of Fallot target of rapamycin tissu e plasminogen activator tranverse rectus abdominis myocutaneous transurethral resection of bladder tumor transurethral resection of prostate units Unrelated Live Transplant Regulator y Authority urinary tract infection uvulopalatopharyngoplasty video assisted thoracic surge ry ventricular tachycardia yttrium aluminum garnet Chapter 1 1 Perioperative anesthetic care and practical procedures P. Kalia and D. Monkhouse Preoperative evaluation 2 Airway assessment 2 Respiratory system 2 Cardiovascular system 2 Myocardial infarction (MI) and congestive cardiac failure (CCF) 3 Supraventricular arrhythmias 11 Ventricular arrhythmias 11 Ventricular fibrillation 12 Respiratory complications 12 Adverse drug reactions 15 Postoperative Hypertension 3 Valvular and congenital complications 18 Hypoxia 18 Nausea and vomiting 18 Hypotension 18 Hypertension 19 Sore throat 19 Practical p rocedures 19 Peripheral venous cannulation 19 heart disease 3 Diabetes mellitus 3 Renal system 3 Hepatic system 4 Haemopoetic system 4 Pr egnancy 4 Social history 4 Family history 5 Laboratory investigations 5 Arterial cannulation 20 Central venous cannulation 21 Pulmonary artery Preoperative medication \200\224 continue or stop? 6 catheterisation (PAC) 22 Medications to be continued 6 Oropharyngeal airway insertion 23 Medications to be stopped 6 Nasopharyngeal airway Intraoperative insertion 24 complications 8 Laryngeal mask airway (LMA) 25 Orotracheal intubation 27 Indications of intubation 27 Compl ications of intubation 27 Cricothyroidotomy 27 Tracheostomy 28 Patient factors 8 Surgical factors 8 Anesthetic factors 8 Cardiovascular problems 8 CHAPTER 1 Perioperative anesthetic care 2 Preoperative evaluation Assessment of the patient before elective inpatient, day case, or e mergency surgery is mandatory. Unnecessary cancelations are thereby avoided. Lack of preope rative assessment increases the risks associated with anesthetics and surgery. The main goa ls of the preoperative visit are to: (cid:142)(cid:3) Establish rapport with the patient be sides allaying apprehensions and anxieties. (cid:142)(cid:3) Assess fitness for anesthesia and surgery by detailed history, physical examination, and laboratory investigations. (cid:142)(cid:3) Control of medical conditions before elective surgery. (cid:142)(cid:3) Pl an the anesthetic technique. (cid:142)(cid:3) Discuss options with the patient (general ver sus local anesthesia). (cid:142)(cid:3) Prescribe premedication and drugs that need to be c ontinued or stopped. (cid:142)(cid:3) Plan postoperative care, including pain relief, HDU, or ICU care. (cid:142 )(cid:3) Obtain informed consent. Airway assessment Factors leading to difficult intubation should be identified. Assessment of the airway is the most important part of preoperative assessment, as failure to maintain the airway can result in life-threatening hypoxia. Any past history of a difficult intubat ion should be documented. Obesity, short neck, limited neck movement, decreased mouth openi ng, pro- minent upper incisors, micrognathia, congenital abnormalities (cystic hygroma, Pie rre Robin, and Treacher Collins syndrome), and facial trauma can lead to difficult intubati on. A thyromental distance of less than 6.5cm can be indicative of a difficult intubation. Respiratory system Patients with pre-existing lung disease (such as chronic obstructive air way disease or asthma) and poor lung function have a higher incidence of postoperative pulm onary complications. Upper respiratory tract infection should be treated before elective su rgery. Asthmatic patients have increased airway reactivity and can develop acute bronchospa sm during laryngoscopy or intubation. Local or regional anesthesia may be a safer option. Cardiovascular system A detailed history should be taken regarding dyspnoea, angina, palpit a- tions, orthopnoea and paroxysmal nocturnal dyspnoea. The patient \200\231s functional ca pacity should be determined as this correlates well with maximum oxygen uptake on treadmill testing and can be prognostically significant. Physical examination should include assessm ent of heart rate and rhythm with measurement of blood pressure and JVP. The chest should b e auscultated to detect murmurs or additional heart sounds. PREOPERATIVE EVALUATION1 3 Myocardial infarction (MI) and congestive cardiac failure (CCF) A history of recent MI or C CF places the patient in a high-risk category. This necessitates full investigation and tre atment prior to elective sur- gery. The reported to range from 0 \200\22337% depending on t he timing of surgery rela- tive to MI. Surgery performed 3 \200\2236 months after MI is ass ociated with a reinfarction rate of 15%. Mortality from postoperative infarction is in the order of 40 \200\22360%. Consequently, elective surgery should be deferred until 6 months a fter a MI. incidence of reinfarction following surgery has been Patients with symptomatic coronary artery disease should be investi- gated preoperatively t o stratify risk. Exercise stress testing and angiogra- phy may be of value in deciding whet her the patient will benefit from coronary revascularisation prior to elective general surg ery. The duration and type of surgery is also important. Vascular surgery carries a higher risk of perioperative MI (10.9%) than abdominal surgery (4.3%). Hypertension Affected patients should be assessed for adequacy of control and in- volvement of target organs (heart and kidney). Patients with uncontrolled hypertension exhibit wide fluctuations of blood pressure intraoperatively because of increased reactivity of blood ve ssels to sympathetic stimula- tion. Wide swings of blood pressure can precipitate myocardia l ischaemia or stroke. Valvular and congenital heart disease Patients with either valvular pathology or congenital heart disease present a major anesthetic challenge. The exact nature of the cardiac proble ms should be known preoperatively and the condition optimized. Concurrent problems such as chest infection and cardiac failure should be treated aggressively. These patients are at r isk of acquiring infective endocarditis and prophylactic antibiotic administration is manda tory. Diabetes mellitus Diabetic control should be assessed. Random blood glucose levels are of l imited value. Glycosylated hemoglobin levels are preferable. Patients should be assessed fo r complications of diabetes such as hypertension, ischaemic heart disease, renal disease, i nfection and autonomic and peri- pheral neuropathy. Preoperative assessment should be geare d towards optimizing perioperative blood glucose control and minimizing complica- tions ass ociated with the coexisting pathologies. Renal system There is a broad clinical spectrum of disease from mild renal dysfunction to e nd-stage renal failure. Patients with preoperative renal dysfunction are more likely to dev elop postoperative renal failure, particularly after aortic or cardiac surgery. CHAPTER 1 Perioperative anesthetic care 4 Anemia, hypertension, ischaemic heart disease and diabetes may complicate the picture. Care should be exercised when administering drugs requiring renal metabolism or excretion. This has a major impact upon the choice of anesthetic agents and provision of postoperative ana lgesia. Meticulous attention to fluid and electrolyte balance is essential. Hepatic system Patients with liver dysfunction represent a high-risk group for anesthesia. They must be fully assessed and optimized prior to theater. Preoperative clinical assessmen t should be geared towards detecting jaundice, ascites and signs of decompensated liver dis ease. All medication administered should take into account altered drug handling. Correctio n of coagulopathy may be required. Deranged electrolytes and acid \200\223base balance are common findings. Deeply jaundiced patients may require preoperative hydration and mannitol to reduce the risk of postoperative renal failure. Haemopoetic system Anemia should be treated preoperatively before elective surgery as oxyge n carrying capacity is decreased. Hemoglobin values of 10g/dL are acceptable as decreased b lood viscosity improves blood flow with a consequent increase in oxygen delivery to the tis sues. In patients with chronic anemia, hemoglobin values of 8g/dL are satisfactory as there is an increase in 2,3 diphosphoglycerate which causes a right shift in the oxygen dissocia tion curve promoting release of oxygen at tissue level. Patients of certain ethnic origin or with a family history of haemoglobi- nopathy should ha ve hemoglobin estimation and electrophoresis performed. If scheduled for emergency surgery, a Sickledex test should be used for screening and followed by electrophoresis if positive to distinguish between sickle cell disease and trait. Pregnancy Elective surgery is best delayed until the second trimester of pregnancy because of potentially detrimental effects on the fetus during organogenesis. In addition, conditio ns requiring abdominal surgery are associated with an increased risk of premature labor or miscarriage. From 16 weeks onwards there is an increased risk of acid aspiration during anesthesia. Hypo tension can occur due to aortocaval compres- sion if the patient is placed in supine positi on. Social history Smoking decreases the oxygen carrying capacity, increases irritability of ai rway and decreases ciliary function. Ideally smoking should be stopped 4 \200\2236 weeks pr ior to surgery. Cessation of smoking 24 hours before sur- gery increases oxygen carrying ca pacity as carbon monoxide is rapidly eliminated. PREOPERATIVE EVALUATION1 5 Chronic alcoholics require increased doses of anesthetics drugs due to enzyme induction. Substance abuse may present problems in the form of difficult venous access, high risk of h epatitis and HIV, resistance to intravenous anaes- thetic agents, opiate analgesia and acut e withdrawal states. Family history There are several genetically inherited diseases that influence anesthetic m anagement, notably malignant hyperthermia, suxemethonium apnoea, porphyria, and myotonic dy strophy. A detailed family history should be taken preoperatively to allow conduct of a saf e, appropriate anesthetic technique. Laboratory investigations Most fit patients (ASA 1) undergoing minor surgery do not need an y investigations. (cid:142)(cid:3) Hemoglobin should be checked in female patients of repro ductive age group and clinically anemic patients. (cid:142)(cid:3) Full blood count, urea and electrolytes should be checked in patients with cardiac, respiratory, or renal disease and in patients on digoxin, diuretics, and ACE inhi bitors. (cid:142)(cid:3) Patients with a history of liver disease or heavy alcohol consumption should have liver function tests performed. (cid:142)(cid:3) A coagulation screen should be checked on all patients with impaired liver function, coagulopathies and those treated with anticoagulants. (cid:142)(cid:3) Chest X-r ay and ECG should be performed in patients with a history of respiratory or cardiac disease respectively. (cid:142)(cid:3) Patients with symptomatic pulmonary disease should be subjected to spirome try and blood gas analysis. Obstructive lung disease can be differentiated from restrictive lung disease by measuring the FEV1/FVC ratio. CHAPTER 1 Perioperative anesthetic care 6 Preoperative medication \200\224continue or stop? It is important to review the prescribed medications. The surgical team and ward staff must be aware of which medications to continu e and which to stop in the preoperative period. Lack of knowledge can lead to dangerous con sequences. Medications to be continued (cid:142)(cid:3) Cardiovascular medication such as calcium chan nel blockers, (cid:168) blockers, nitrates, and antiarrhythmic agents should be continued as sudden withd rawal can precipitate hypertension, ischaemia, and myocardial infarction. (cid:142)(cid:3) Bronchodilators should be continued as withdrawal can precipitate bronchospasm. (cid:142)(cid:3) Antiepileptic treatment should be continued. (cid:142)(cid:3) Steroid inta ke can cause adrenal suppression. History of steroid intake (prednisolone 10mg or more) wit hin the last three months requires hydrocortisone supplementation perioperatively. (cid:142)(cid:3) Aspirin inhibits platelet function and is the mainstay of secondary prevention in patients with history of myocardial infarction or stroke. It should be contin ued unless major bleeding is expected (cardiac or prostate surgery) or minor bleeding is be st avoided (retinal or intra cranial surgery). The risk of bleeding should be weighed again st the risk of precipitating a thromboembolic event. Medications to be stopped (cid:142)(cid:3) Anticoagulants Warfarin should be stopped at lea st four days before surgery as these patients are at increased risk of bleeding. The effect of warfarin can be reversed with vitamin K (or fresh frozen plasma in an emergency). An In ternational Normalized Ratio (INR) of 1.5 \200\2232 is acceptable. In patients with a high risk of thromboembolism, a continuous intravenous infusion of unfractionated heparin should be commenced at 1000 U/hour and the rate adjusted to keep APTTR between 1.5 \200\2232.5. T his should be stopped 6 hours before surgery, recommenced 12 hours post surgery and continu ed until warfarin is reinstituted and INR >2.0. For patients with a low risk of thrombo- em bolism, the use of subcutaneous low molecular weight heparin is recommended until warfarin therapy can be restarted and INR >2.0. (cid:142)(cid:3) Anticoagulants and central neuraxial block (spinal and epidural) These techniques should be avoided in patients with a coagulopathy or those on warfarin the rapy. In patients requiring DVT prophylaxis, a spinal or epidural can be performed six hour s after subcutaneous injection of unfractionated heparin and 12 hours after low molecular w eight heparin. Aspirin is not a contraindication to use these blocks. PREOPERATIVE MEDICATION \200\224CONTINUE OR STOP?1 7 (cid:142)(cid:3) ACE inhibitors and angiotensin II receptor antagonists may be associated w ith severe hypotension on induction or during maintenance of anesthesia. These drugs are us ually stopped 24 hours prior to surgery. (cid:142)(cid:3) Oral hypoglycaemic agents like chlorpropamide and metformin should be stopped 48 hours before surgery. Long-acting agents should be substituted by shor t-acting drugs like gliclazide. For minor surgery, it is acceptable to omit the morning dos e of oral hypoglycaemic agent. However, a GKI infusion is required for those undergoing maj or surgery and patients with poor preoperative glycaemic control. (cid:142)(cid:3) Contraceptive pill and anesthesia Synthetic oestrogens increase the risk of thromboembolism by increasing the activity of clotting factors. Estrogen-only and t he combined pill should be stopped four weeks before elective surgery; other forms of contr aception should be offered. Heparin should be given if emergency surgery is contemplated. T he progestogen-only pill and HRT do not need to be discontinued. (cid:142)(cid:3) Monoamine oxidase inhibitors should be discontinued two weeks before elect ive surgery. They can precipitate a fatal reaction if used concurrently with indirectly act ing vasopressors (ephedrine) or pethidine. The reaction occurs as a consequence of excessiv e levels of monoamines and inhibition of hepatic enzymes. Non-selective MAO inhibitors (phe nelzine, and tranylcypromine) can be replaced with meclobemide, a short acting selective in hibitor of MAO-A. Meclobemide can be stopped 12 hours before surgery. (cid:142)(cid:3) Selective serotonin reuptake inhibitors (SSRIs) lack anticholinergic effec ts and are frequently used as alternative to tricyclic antidepres- sants. Fluoxetine and pa roxetine increase serotonergic transmission. When concurrent serotonergic medications such as pethidine, tramadol, and pentazocine are used, a fatal serotonin syndrome can occur (hyp ertension, fever, hyperreflexia, and coma). CHAPTER 1 Perioperative anesthetic care 8 Intraoperative complications Most intraoperative problems are foreseeable and preventable. They are minimized by a thorough preoperative assessment of the patient, meticu- lous check ing of anesthetic equipment and use of appropriate anaes- thetic and surgical techniques by suitably skilled personnel. Intraoperative problems occur in 9% of all patients undergoing surgery. The risks of intraoperative complications can be related to: Patient factors (cid:142)(cid:3) Extremes of age (cid:142)(cid:3) Morbid obesity (cid:142)( cid:3) Nature of underlying disease process (cid:142)(cid:3) Co-existing morbidity. Surgical factors (cid:142)(cid:3) Complexity, timing, and duration of operation (cid:142)(c id:3) Urgency of procedure (cid:142)(cid:3) Experience of surgeon. Anesthetic factors (cid:142)(cid:3) Adequacy of preoperative preparation (cid:142)(cid:3) L ack of appropriate monitoring (cid:142)(cid:3) Urgency of anesthesia (cid:142)(cid:3) Exper ience of anesthetist. Should an adverse event occur, it is imperative that it is promptly r ecog- nised and effectively managed to minimize the risk to the patient. Cardiovascular problems Hypotension during surgery may be defined as a fall in systolic blo od pressure in excess of 25% of the patient \200\231s preoperative value. This may result i n inadequate tissue perfusion, ischaemia, and ultimately organ dysfunction. The causes of hypotension are usually multifactorial and are often con- founded by hypovola emia due to inadequate preoperative fluid replace- ment or excess intraoperative loss. Immediate management involves confirmation of the blood pressure reading, delivery of a hig h concentration of oxygen, and implementation of measures to restore cardiac output (fluid bolus, head down tilt, reduc- tion in concentration of anesthetic agents or administration of vasopres- sor agents). In most instances, these measures are adequate to restore BP. If hypotension persists despite these measures, causes such as pneu- mothorax, myocardial isch aemia, embolism, and anaphylaxis should be considered. Subsequent management should be dire cted towards cor- recting the underlying problem. Hypertension during surgery may be defined as an increase in systolic pressure in excess of 25% of the patient \200\231s preoperative value. This results in increased myocardial work load and hence oxygen demand. If myocar- dial oxygen supply is inadequate to meet demand, t hen ischaemia ensues. Hypertension also results in increased risk of cerebrovascular events . INTRAOPERATIVE COMPLICATIONS1 9 The use of perioperative beta-blockade may circumvent this problem. Immediate management sh ould involve a systematic search for the under- lying cause. If hypertension persists, the alternative options include increasing the depth of anesthesia and/or analgesia and adminis tration of alpha-blockers, beta-blockers or vasodilators. Bradycardia may be defined as a heart rate of <60bpm. It is commonly seen during anesthesia , particularly in young healthy adults or where opioids are used as part of the anesthetic. Surgical procedures which increase vagal tone may also produce bradycardia, for example, c ervical dilatation, anal stretch, traction on extraocular muscles, and peritoneal traction. Treatment is reserved for clinically significant bradycardias where there is a reduction in cardiac output or where escape beats are seen on the ECG. Treatment options include antich olinergics such as glycopyrrolate and atropine. For refractory bradycardia with haemodynami c compro- mise, it may be necessary to use either an isoprenaline infusion or a temporary t ransvenous cardiac pacing wire. Causes of intraoperative hypotension Decreased preload (cid:142)(cid:3) Hypovolaemia Dehydration/inadequate replacement Hemorrhage Gastrointestinal losses Insensible or third space losses Embolism (t hrombus, gas, fat, air) Aorto \200\223caval compression Pericardial tamponade (cid:142)(cid:3) Obstructed venous return (cid:142)(cid:3) Increased intra-thoracic pressure Positive pressure ventilation Pneumothorax Decreased afterload (cid:142)(cid:3) Drugs Induction agents Volatile agents Antihypertensives Histamine release Anaphylaxis/hypersensi tivity reactions (cid:142)(cid:3) Anesthetic technique Spinal anesthesia Epidural anesthesia (cid:142)(cid:3) Sepsis Decreased contractility (cid:142)(cid:3) Drugs Anesthetic agents Beta-blockers Calcium antagonists (cid:142)(cid:3) Myocardial ischaemia (cid:142)(cid:3) Acidosis (cid:142)(cid:3) Arrhythmia s CHAPTER 1 Perioperative anesthetic care 10 Causes of intraoperative hypertension Patient factors (cid:142)(cid:3) Pre-existing hyperte nsion (cid:142)(cid:3) Raised intracranial pressure (cid:142)(cid:3) Pre-eclampsia (cid:142 )(cid:3) Rebound hypertension (cessation of therapy) (cid:142)(cid:3) Phaeochromocytoma (ci d:142)(cid:3) Thyroid storm Surgical factors (cid:142)(cid:3) Prolonged tourniquet time (ci d:142)(cid:3) Aortic-cross clamping (cid:142)(cid:3) Post-myocardial revascularisation (cid :142)(cid:3) Bladder distension Anesthetic factors (cid:142)(cid:3) Inadequate depth of ane sthesia (cid:142)(cid:3) Inadequate analgesia (cid:142)(cid:3) Hypoxaemia (cid:142)(cid:3) Hypercapnia (cid:142)(cid:3) Instrumentation of airway (cid:142)(cid:3) Hypothermia (cid:14 2)(cid:3) Malignant hyperthermia (cid:142)(cid:3) Hypervolaemia Tachycardia may be defined as a heart rate of >100bpm. It can occur as a normal physiologic al response to sympathetic stimulation or as part of a pathological process such as sepsis, burns, hyperthyroidism or malig- nant hyperthermia. Increased sympathetic tone can be exac erbated by hypoxaemia, hypercapnia, hypotension, hypovolaemia and inadequate anesthesia/ana lgesia. Treatment involves correction of the underlying cause. Pharmacological intervention may be required if persistent tachy- cardia produces myocardial ischaemia. Arrhythmias occur frequently in the intraoperative period. They can be precipitated by the following: (cid:142)(cid:3) Hypoxaemia (cid:142)(cid:3) Hypercapnia (cid:142)(cid:3) Hypo/h yperkalaemia (cid:142)(cid:3) Myocardial ischaemia (cid:142)(cid:3) Surgical stimulation an d light anesthesia (cid:142)(cid:3) Deep inhalational anesthesia, particularly halothane (c id:142)(cid:3) Central venous cannulation (cid:142)(cid:3) Mediastinal manipulation (cid:14 2)(cid:3) Chronotropic drugs, particularly epinephrine. INTRAOPERATIVE COMPLICATIONS1 11 General management (cid:142)(cid:3) Correct the cause (hypoxia, hypercarbia, electrolyte im balance, and acidosis). (cid:142)(cid:3) Inform the surgeon to stop the surgery as reflex bradycardia can occur dur ing various procedures such as eye surgery, mesenteric traction, anal stretch, and laparosc opic procedures. (cid:142)(cid:3) Correct the hypotension. Specific management Aggressive management is requ ired in the presence of haemodynamic instability. Specific treatment of various arrhythmias is described below. Supraventricular arrhythmias Atrial fibrillation. ECG shows loss of P waves with complete i rregularity of the QRS complex. Because atrial contraction contributes up to 30% of the nor mal ventricular filling, the onset of AF often produces a marked fall in cardiac output. Treatment (cid:142)(cid:3) Amiodarone to slow down the ventricular rate and chemically cardiovert. (cid:142)(cid:3) Digoxin to slow ventricular rate. (cid:142)(cid:3) Flecainide to restore s inus rhythm (but caution with LV dysfunction). (cid:142)(cid:3) Synchronized DC cardioversi on in event of haemodynamic compromise. Atrial flutter is seen in the intraoperative period as a paroxysmal ar- rhythmia precipitat ed by anesthesia and surgery in a susceptible individual. ECG shows the classical \200\230 saw-tooth \200\231 pattern of flutter waves. Treatment (cid:142)(cid:3) Synchronized DC shock in an anesthetized patient with any degree of cardiovascular compromise is the first-line treatment. (cid:142)(cid:3) Digoxin or amiodaro ne infusion would be an alternative. Junctional/AV nodal tachycardias. ECG shows a narrow c omplex tachy- cardia with ventricular rate of 150 \200\223200/minute. A broad complex patte rn may be seen if there is antegrade conduction down an accessory pathway. Treatment (cid:142)(cid:3) Synchronized DC shock in a haemodynamically compromised patient. (cid:142)(cid:3) Carotid sinus massage or vagal maneuvers may slow the rate to reveal the underlying rhythm. (cid:142)(cid:3) Adenosine slows atrioventricular conduction and is particularly useful for terminating the re-entry tachycardia of Wolff \200\223Parkinson \200\223White syndrome. (cid:142)(cid:3) Verapamil, beta-blockers or amiodarone may improve rate control or convert to sinus rhythm. Ventricular arrhythmias Ventricular tachycardia. The ECG shows a broad complex tachycardia with capture and fusion beats. CHAPTER 1 Perioperative anesthetic care 12 Treatment (cid:142)(cid:3) Synchronized DC shock is the first-line treatment of VT with cardiovascular compromise. Synchronization is not required if the VT is very rapid or the p atient is pulseless. (cid:142)(cid:3) Amiodarone is the first line pharmacological agent. Ventricular fibrillation There is chaotic ventricular contraction with no identifiable QRS complexes on ECG. Treatment This should be promptly managed with DC cardioversion according to the European R esuscitation Council guidelines. Myocardial ischaemia occurs when myocardial oxygen demand exceeds supply. Oxygen supply to the myocardium is determined by coronary blood flow and oxygen content. Demand is determine d by heart rate, contractility and wall tension. Tachycardia is the most important deter- m inant of the supply/demand ratio because it causes a reduction in diastolic coronary fillin g, with a simultanous increase in myocardial work. Patients most at risk perioperatively ar e those with a recent MI, poorly controlled angina, decompensated heart failure or severe v alvular disease. Monitoring susceptible patients with a V5 ECG electrode and with continuou s ST segment analysis will improve ischaemia detection rates. Intraoperative management sho uld be geared towards ensuring adequate arterial oxygenation, maintaining normocapnia, norm otension, and avoidance of tachycardia whilst ensuring adequate depth of anaesthe- sia and effective analgesia. The use of glyceryl trinitrate as a coronary vasodilator may be necess ary if ischaemic changes persist.