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Risks associated with anaesthesia
CLINICAL ANAESTHESIA
Risks associated with anaesthesia
Learning objectives After reading this article, you should be able to: C list the common and serious risks that occur during the conduct of regional and general anaesthesia C provide the patient with the incidence of each relevant complication (where available) C appreciate those risks that involve human error as a factor and take any necessary steps to avoid them in your working practice.
Sophie A Kimber Craig Ross Kitson
Abstract Anaesthesia is a necessary part of any operation and it carries with it certain risks to the patient. While every effort can be made to avoid errors secondary to human and system failures, complications can arise, whether they are idiosyncratic reactions, common side effects or unpredictable problems. For the anaesthetist to be able to adequately consent the patient for anaesthesia they must be aware of the risks. This article outlines the risks associated with the conduct of anaesthesia, from preparation and induction to emergence and postoperatively. We look at both general and regional anaesthesia and have given incidence data where they are available. It is not possible to list every possible complication that could occur during an anaesthetic, so we have focused on those that are common and those that are serious (in terms of potential outcome for the patient) and some other relevant procedural issues.
The complications of anaesthesia and their associated risk factors are given in Table 1.
Oral injury Dental damage is rare (1:4500 GAs). Lip and tongue lacerations or abrasions are common (5%). Sore throat occurs in 50% of patients who have an endotracheal tube (ETT) and 20% with laryngeal mask airways (LMA).2
Respiratory risk Atelectasis occurs commonly during anaesthesia. Lower respiratory tract infection (RTI) can develop as a consequence. Laryngospasm and bronchospasm are potentially fatal. The risk increases with: pre-existing respiratory disease paediatric patients recent upper or lower RTI airway manipulation and light anaesthesia.
Keywords Anaphylaxis; aspiration; awareness; cardiac risk; consent; death; general anaesthesia; neurological complications; regional anaesthesia; risk
Postoperative respiratory depression Respiratory depression is common in the recovery period. There are many anaesthetic causes which are listed in Table 1. Respiratory depression and airway issues postoperatively are a common cause of cardiac arrest and therefore must be identified and managed appropriately to prevent these catastrophic outcomes.
Airway management Ventilation and intubation Failure of bag-mask ventilation and intubation is, fortunately, rarely encountered during the course of anaesthesia but is extremely serious; hypoxia leading to brain damage and death can ensue. Difficult intubation (Cormack and Lehane laryngoscopy view of 3 or 4) occurs in 2e8% of attempted intubations. Failed intubation occurs more rarely, in 0.13e0.35% of cases. The rate is higher in obstetric patients (1:250e300).1 Bronchial or oesophageal intubation, oesophageal perforation, tracheobronchial damage and direct vocal cord injury are other potential complications of the intubation process.
Cardiovascular problems Hypotension is common; those with pre-existing end-organ pathology, hypertension and atherosclerosis are at increased risk of developing complications if it is prolonged. The incidence of myocardial infarction (MI) and cardiac ischaemia increases with certain risk factors (see Table 2). The aetiology of perioperative myocardial infarction is multi-factorial and may involve alterations in coronary plaque morphology and in myocardial oxygen supply-demand balance. Cardiac arrest has an incidence of 0.12e1.4:10,000 with a death rate of 0.06e0.6:10,000.
Aspiration Aspiration of the gastrointestinal contents occurs in 1:3000 general anaesthetics (GAs) with a mortality of 1:50,000. The risk factors are given in Table 1.
Sophie A Kimber Craig MB ChB FRCA is an Anaesthetic Specialist Registrar in the Northwest Deanery, UK. Conflicts of interest: none declared.
Neurological complications Peripheral nerve damage occurs most commonly in the ulnar and common peroneal nerves and the brachial and lumbosacral plexi.3 Nerve injury occurs through many mechanisms but those relevant to anaesthesia are:
Ross Kitson FRCA is a Consultant Anaesthetist at Tameside General Hospital, UK. Conflicts of interest: none declared.
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CLINICAL ANAESTHESIA
Complications of general anaesthesia and their risk factors (not including death and risks posed by the theatre environment) Complication Airway management
Difficulty with intubation and/or ventilation
Oesophageal, tracheal or bronchial injury Vocal cord injury Aspiration
Respiratory risks
Oral injury Atelectasis Laryngospasm and bronchospasm
Postoperative respiratory depression
Pneumonia and postoperative pulmonary complications
Cardiac complications
Hypotension
Myocardial infarction and ischaemia Cardiac arrest Neurological complications
Peripheral and central axial nerve damage
Stroke and brain damage Headaches Confusion
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Risk factors Congenital and acquired facial and oral deformities (e.g. micrognathia, burn injuries, obesity, pregnancy); restricted neck movement (e.g. rheumatoid arthritis, cervical spine injury); oral, pharyngeal, laryngeal or tracheal tumours Pre-existing pathology (e.g. tumour); intubation injury (e.g. use of stylet, gum elastic bougie) Passage of oral ETT Emergency surgery (due to inadequate starvation period, pain and opioids reducing gastric emptying) Pregnancy (increased gastric acid production, reduced gastrooesophageal junction tone, increased intra-abdominal contents) Intra-abdominal pathology (increased intra-abdominal pressure) Hiatus hernia and/or gastro-oesophageal reflux disease Use of ETT and LMA; presence of loose, capped or crowned teeth Prolonged anaesthesia; failure to use PEEP; laparoscopic or abdominal procedures Pre-existing bronchial hyperreactivity (e.g. in asthma); paediatric patients; recent RTI (within 4 weeks); induction, intubation, positioning and emergence; light anaesthesia and stimulation during surgery Pre-existing medical conditions (e.g. respiratory disease, dementia, cardiac failure) Postoperative sedation (drug-related) Inadequate reversal of neuromuscular blockade Airway obstruction (e.g. retained secretions, failure of patient to maintain own airway) Respiratory narcosis (secondary to elevated carbon dioxide levels) Age >60 years; COPD; ASA grade of >1; functional dependency; congestive cardiac failure; prolonged surgery, surgery type (aneurysm, thoracic, head and neck, vascular, emergency); general anaesthesia; hypoalbuminaemia Drug-related (e.g. relative overdose of induction agent); hypovolaemia; regional anaesthesia; TIVA; purposeful anaesthetic technique (‘hypotensive anaesthesia’) See Table 2 Includes risks as in Table 2, and respiratory complications (causing hypoxaemia) Surgical positioning (see main text); use of tourniquets, BP cuffs, arm supports, etc.; conditions causing reduced perfusion of nerve tissue (e.g. diabetes, atherosclerosis); emaciated and obese patients; hypotensive anaesthesia; direct injury (due to chemical injection, needle injury, compression) Previous history of stroke; increasing age; surgery type (head, neck and cardiac); hypoxaemia; hypotension Caffeine withdrawal; drug-related (e.g. vasodilators, or withdrawal of opioids); dehydration/hypovolaemia Increasing age; pre-existing neurological conditions (e.g. previous stroke, dementia); pre-existing respiratory or cardiac conditions; high levels of preoperative alcohol consumption; poorly sighted or hard of hearing individuals (as they will find it difficult to orientate themselves); prolonged surgery; surgery type (cardiac surgery in particular)
Ó 2010 Elsevier Ltd. All rights reserved.
CLINICAL ANAESTHESIA
Eye injuries
Corneal abrasions Blindness
Drug-related complications
Anaphylaxis Awareness
Open eyes while under anaesthesia Hypotensive anaesthesia; pre-existing atherosclerotic or hypertensive eye disease; compression (e.g. in prone position) Previous exposure to allergen Emergency surgery; inadequate monitoring (e.g. failure of anaesthetist to notice changes in cardiovascular parameters); failure to deliver adequate anaesthesia; TIVA (e.g. with loss of cannula); intubation and extubation, patient positioning; Use of muscle relaxants Genetic predisposition Suxamethonium apnoea (genetic predisposition) Pregnancy; drug-related; neonates and elderly; liver disease; burns patients; malnutrition Drug-related (e.g. nitrous oxide, opioids); pain; surgery type (e.g. ENT, laparoscopic and gynaecological procedures); female; nonsmokers; previous PONV and travel sickness Anaesthetic-related (e.g. vasodilation); failure to warm patient adequately perioperatively; hypothermia prior to theatre admission
Malignant hyperpyrexia Pseudocholinesterase deficiency
PONV
Hypothermia and shivering
ASA, American Society of Anesthesiologists; BP, blood pressure; COPD, chronic obstructive pulmonary disease; CVA, cerebrovascular accident; ENT, ear, nose and throat; ETT, endotracheal tube; LMA, laryngeal mask airway; PEEP, positive end-expiratory pressure; PONV, postoperative nausea and vomiting; RTI, respiratory tract infection; TIVA, total intravenous anaesthesia.
Table 1
Perioperative cardiac risk factors. Defined by the ACC/AHA (2007) in their working party report by Fleischer et al. Active cardiac conditions
Unstable coronary syndromes (e.g. unstable or severe angina, recent MI) Decompensated heart failure (NYHA functional class IV; worsening or new-onset of heart failure) C Significant arrhythmias (e.g. third degree heart block, Mobitz type II block, symptomatic ventricular arrhythmias, uncontrolled AF, symptomatic bradycardia) 2 C Severe valvular disease (severe aortic stenosis [gradient >40 mmHg, area <1 cm , symptomatic], symptomatic mitral stenosis [exertional dyspnoea, presyncope, heart failure]) History of heart disease History of compensated or prior heart failure History of cerebrovascular disease Diabetes mellitus Renal insufficiency Age >70 years Abnormal ECG (LVH, LBBB, ST-T abnormalities) Rhythm other than sinus Uncontrolled systemic hypertension C Vascular surgery (reported risk of cardiac death and non-fatal MI >5%) e aortic and major vascular surgery, peripheral vascular surgery C Intermediate risk (1e5%) e cavity surgery, carotid endarterectomy, head and neck surgery. Orthopaediac surgery, prostate operation C Low risk (<1%) e endoscopic procedures, superficial surgery, cataract operations, ambulatory surgery <4 METs C C
Major risks
Minor risk factors (markers for cardiac disease that have not been proven to independently increase risk) Surgical factors
Functional capacity
ACC, American College of Cardiology; AF, atrial fibrillation; AHA, American Heart Association; ECG, electrocardiography; LBBB, left bundle branch block; LVH, left ventricular hypertrophy; MET, metabolic equivalent; MI, myocardial infarction; NYHA, New York Heart Association.
Table 2
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compression and stretching (which occur during positioning and through the use of automated blood pressure (BP) cuffs and tourniquets) hypoperfusion (which may be local compression of vessels supplying the nerve or more general hypotension) direct injury (e.g. during line insertions) chemical toxicity idiopathic. Risk factors include: prone, lateral and lithotomy positions and extended/rotated arm positions orthopaedic procedures and spinal, brain, cardiac or vascular surgery diabetes, rheumatoid or osteoarthritis and athelosclerosis increasing age extremes of body mass index (BMI) B Low BMIs (<20) have less fat deposits to protect bony areas B Obese patients are at risk of compression at flexed areas and the sacrum, for example, and require more supports for positioning which have the potential to impinge on nerves. The risk of permanent damage is <1:5000. Spinal cord damage secondary to general anaesthesia is rare but is usually permanent and serious in nature (e.g. loss of bladder and bowel function, paralysis). In terms of anaesthetic risk, this is usually caused by an inadequate spinal cord blood supply.
respiratory complications all increase the risk of this problem when it presents early. Age is the only risk factor for late POCD.
Eye injuries Corneal abrasions causing symptoms occur in 1:1750 anaesthetics. Blindness secondary to retinal artery occlusion or hypotension is very rare with an incidence of <1 in 120,000.5
Drug-related risks Anaphylaxis The incidence of anaphylactic reactions is 1:10,000e20,000. There is an increased prevalence of these reactions amongst anaesthetic patient populations, due mainly to the use of primarily intravenous agents and the potential for polypharmacy. Muscle relaxants are the most common cause of anaphylaxis (up to 60% of cases related to anaesthesia) with latex (20%), antibiotics (15%) and colloids (4%) also being precipitants. Local anaesthetics, intravenous induction agents, opioids and non-steroidal anti-inflammatory drugs are infrequent causes. There are no reported cases of anaphylaxis to inhalational anaesthetic agents. The most common presentation under anaesthesia is cardiovascular collapse for which there is a 10% mortality.6 Awareness The quoted incidence of awareness is very variable. The commonly stated risk is about 1%, but this includes different anaesthetic approaches to current practice and depends on how awareness is defined. A recent prospective study gave an incidence of awareness with recall of 0.6%,7 but a large retrospective study of American patients showed an incidence of approximately 1:14,000.8 Patients particularly at risk are those undergoing emergency (especially caesarean section and trauma surgery) and heart surgery and surgery performed at night. Premedication with benzodiazepines may confer some protective benefits.
Stroke and brain damage Stroke is more common in patients with a previous history, the elderly and those undergoing head, neck (especially carotid artery) and heart surgery. Brain damage as a consequence of anaesthesia is extremely rare. Likely causes are inadvertent hypoxia or prolonged hypotension. Headaches, drowsiness and postoperative confusion and cognitive dysfunction Neurological sequelae following anaesthesia are common but usually temporary. The anaesthetic agents used are often implicated, although headaches are frequently related to caffeine withdrawal. Postoperative confusion, manifesting as hallucinations, loss of orientation or changes in personality, can occur. Patients at risk of confusion: are the elderly have pre-existing acute or chronic illnesses have dementia, other neurological conditions or had previous strokes are heavy alcohol consumers (the usual precipitating cause of confusion being alcohol withdrawal) those with pre-existing visual or auditory disturbance. Postoperative cognitive dysfunction (POCD) has been described, where patients cannot perform higher order functions, have poor memory and lack of concentration, which may stop them returning to work. POCD is linked to cardiac surgery in particular, but occurs in other types of surgery too. One multicentre study into noncardiac surgery showed that approximately one-quarter of patients over 60 years old had POCD at one week postoperatively and one-tenth at 3 months (compared with 3.4% and 2.8%, respectively, in controls).4 Increasing age, duration of anaesthesia, low educational level, repeat surgery, postoperative infections and
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Malignant hyperpyrexia and pseudocholinesterase deficiency The incidence of malignant hyperpyrexia is 1:10,000e15,000 with a 2e3% mortality. Pseudocholinesterase deficiency is inherited or acquired. Four percent of the Caucasian population carry a version of the gene causing the genetic variety. Postoperative nausea and vomiting (PONV) At least one-third of patients experience PONV. Women, children, non-smokers and those with previous PONV or travel sickness are more commonly affected. Hypothermia and shivering The potential problems of perioperative temperatures <36 C include increased blood loss, longer recovery, morbid cardiac events, increased wound infection and longer hospital stays.9 Shivering can occur without a change in body temperature. Approximately 25% of patients experience this unpleasant but self-limiting side effect.
Pain Although not an anaesthetic risk per se, pain is a common complication of surgery that is under the remit of the
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3 Sawyer RJ, Richmond MN, Hickey JD, Jarratt JA. Peripheral nerve injuries associated with anaesthesia. Anaesthesia 2000; 55: 980e91. 4 Moller JT, Cluitmans P, Rasmussen LS, et al. Long-term postoperative dysfunction in the elderly: ISPOCD1 study. Lancet 1998; 351: 857e61. 5 Jenkins K, Baker AB. Consent and anaesthetic risk. Anaesthesia 2003; 58: 962e84. 6 Association of Anaesthetists of Great Britain & Ireland (AAGBI). Suspected anaphylactic reactions associated with anaesthesia [Online] Available at: http://www.aagbi.org/publications/guidelines/ docs/anaphylaxis_2009.pdf; 2009 (accessed 28 Apr 2010). 7 Errando CL, Sigl JC, Robles M, et al. Awareness with recall during general anaesthesia: a prospective observational study of 4001 patients. BJA 2008; 101: 178e85. 8 Pollard RJ, Coyle JP, Gilbert RL, Beck JE. Intraoperative awareness in a regional medical system: a review of 3 years’ data. Anesthesiology 2007; 106: 269e74. 9 National Institute for Health and Clinical Excellence. Clinical practice guideline: the management of inadvertent peri-operative hypothermia in adults (full guidance) [Online] Available at: http://www.nice.org.uk/ nicemedia/pdf/CG65Guidance.pdf; 2008 (accessed 9 Feb 2010). 10 Cook TM, Counsell D, Wildsmith JAW. Major complications of central neuraxial block: report on the Third National Audit Project of the Royal College of Anaesthetists. Br J Anaesth 2009; 102.
anaesthetist. A significant proportion of patients experience pain and this has implications in terms of lengthened hospital stay and patient satisfaction ratings. It has also been linked with PONV. Poorly controlled postoperative thoracic or abdominal pain increases the chances of respiratory complications, secondary to reduced secretion clearance and atelectasis, and significant pain will prevent early mobilization.
Death The risk of death related solely to anaesthesia is approximately 1:100,000 for American Society of Anesthesiologists (ASA) grade I and II patients. The risk increases with higher ASA grading and emergency surgery. According to the last two Confidential Enquiry into Maternal and Child Health (CEMACH) reports, death attributable to anaesthesia in obstetric patients is low (0.3:100,000 maternities).
Regional anaesthesia Major complications of regional anaesthesia, as defined by the Royal College of Anaesthetists in their recent National Audit Project, include paraplegia, death, spinal or epidural infection or bleeding, nerve injury, spinal cord ischaemia and wrong route drug errors. Permanent injury occurs in 2e4.2:100,000 times and perioperative epidurals confer the most risk (8.2e17.4:100,000). The incidence of paraplegia and death is 0.7:100,000.10 Post-dural puncture headache is seen in approximately 1% of patients. Transient neurological damage occurs in 4e80:10,000 spinals and 1e10:10,000 epidurals. Urinary retention is common. Systemic toxicity has an incidence of 1:10,000, and seizures and cardiac arrest may result.
FURTHER READING Confidential enquiry into perioperative deaths (CEPOD) and confidential enquiry into maternal and child health (CEMACH) reports. (Triennial reports into the risks associated with surgery and the risks posed to the mother and newborns, which gives detailed analysis of the anaesthetic complications associated with these groups.) Difficult Airway Society. Guidelines [Online] Available at: http://www.das. uk.com/guidelines/guidelineshome.html; 2010 (accessed 28 Apr 2010). (The society’s guidelines on the management of “can’t intubate, can’t ventilate” situations is available here and other algorithms for the managing the difficult airway are also available. The results of the National Audit Project 4, which is looking at complications resulting from airway management, are also due to be published on the society’s website shortly.) Inouye SK. Delirium in older persons. N Engl J Med 2006; 354: 1157e65. (A review article looking at the epidemiology, clinical characteristics, methods of prevention and management of delirium in people over 65 years of age.) Royal College of Anaesthetists. Risk information leaflets [Online] Available at: http://www.rcoa.ac.uk/index.asp?PageID¼1209; 2009 (accessed 28 Apr 2010). (These are very useful patient information leaflets pertaining to the common concerns of patients prior to an anaesthetic and the potential serious consequences.)
Equipment and theatre risks The theatre poses a constant risk to the patient. Diathermy burns, theatre fires and cross infection are examples that are not considered in detail here, but historically have made headlines. All equipment has the potential to fail and even simple devices such as blood pressure cuffs can harm patients. The anaesthetist as a member of the multidisciplinary team has a duty to ensure that all policies implemented to improve patient safety are followed in the hazardous environment of the operating theatre.A
REFERENCES 1 Heard AMB, Green RJ, Eakins P. The formulation and introduction of a “can’t intubate, can’t ventilate” algorithm into clinical practice. Anaesthesia 2009; 64: 601e8. 2 Contractor S, Hardman JG. Injury during anaesthesia. Cont Educ Anaesth Crit Care Pain 2006; 6: 67e70.
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Ó 2010 Elsevier Ltd. All rights reserved.
Risks associated with anaesthesia
Learning objectives After reading this article, you should be able to: C list the common and serious risks that occur during the conduct of regional and general anaesthesia C provide the patient with the incidence of each relevant complication (where available) C appreciate those risks that involve human error as a factor and take any necessary steps to avoid them in your working practice.
Sophie A Kimber Craig Ross Kitson
Abstract Anaesthesia is a necessary part of any operation and it carries with it certain risks to the patient. While every effort can be made to avoid errors secondary to human and system failures, complications can arise, whether they are idiosyncratic reactions, common side effects or unpredictable problems. For the anaesthetist to be able to adequately consent the patient for anaesthesia they must be aware of the risks. This article outlines the risks associated with the conduct of anaesthesia, from preparation and induction to emergence and postoperatively. We look at both general and regional anaesthesia and have given incidence data where they are available. It is not possible to list every possible complication that could occur during an anaesthetic, so we have focused on those that are common and those that are serious (in terms of potential outcome for the patient) and some other relevant procedural issues.
The complications of anaesthesia and their associated risk factors are given in Table 1.
Oral injury Dental damage is rare (1:4500 GAs). Lip and tongue lacerations or abrasions are common (5%). Sore throat occurs in 50% of patients who have an endotracheal tube (ETT) and 20% with laryngeal mask airways (LMA).2
Respiratory risk Atelectasis occurs commonly during anaesthesia. Lower respiratory tract infection (RTI) can develop as a consequence. Laryngospasm and bronchospasm are potentially fatal. The risk increases with: pre-existing respiratory disease paediatric patients recent upper or lower RTI airway manipulation and light anaesthesia.
Keywords Anaphylaxis; aspiration; awareness; cardiac risk; consent; death; general anaesthesia; neurological complications; regional anaesthesia; risk
Postoperative respiratory depression Respiratory depression is common in the recovery period. There are many anaesthetic causes which are listed in Table 1. Respiratory depression and airway issues postoperatively are a common cause of cardiac arrest and therefore must be identified and managed appropriately to prevent these catastrophic outcomes.
Airway management Ventilation and intubation Failure of bag-mask ventilation and intubation is, fortunately, rarely encountered during the course of anaesthesia but is extremely serious; hypoxia leading to brain damage and death can ensue. Difficult intubation (Cormack and Lehane laryngoscopy view of 3 or 4) occurs in 2e8% of attempted intubations. Failed intubation occurs more rarely, in 0.13e0.35% of cases. The rate is higher in obstetric patients (1:250e300).1 Bronchial or oesophageal intubation, oesophageal perforation, tracheobronchial damage and direct vocal cord injury are other potential complications of the intubation process.
Cardiovascular problems Hypotension is common; those with pre-existing end-organ pathology, hypertension and atherosclerosis are at increased risk of developing complications if it is prolonged. The incidence of myocardial infarction (MI) and cardiac ischaemia increases with certain risk factors (see Table 2). The aetiology of perioperative myocardial infarction is multi-factorial and may involve alterations in coronary plaque morphology and in myocardial oxygen supply-demand balance. Cardiac arrest has an incidence of 0.12e1.4:10,000 with a death rate of 0.06e0.6:10,000.
Aspiration Aspiration of the gastrointestinal contents occurs in 1:3000 general anaesthetics (GAs) with a mortality of 1:50,000. The risk factors are given in Table 1.
Sophie A Kimber Craig MB ChB FRCA is an Anaesthetic Specialist Registrar in the Northwest Deanery, UK. Conflicts of interest: none declared.
Neurological complications Peripheral nerve damage occurs most commonly in the ulnar and common peroneal nerves and the brachial and lumbosacral plexi.3 Nerve injury occurs through many mechanisms but those relevant to anaesthesia are:
Ross Kitson FRCA is a Consultant Anaesthetist at Tameside General Hospital, UK. Conflicts of interest: none declared.
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Ó 2010 Elsevier Ltd. All rights reserved.
CLINICAL ANAESTHESIA
Complications of general anaesthesia and their risk factors (not including death and risks posed by the theatre environment) Complication Airway management
Difficulty with intubation and/or ventilation
Oesophageal, tracheal or bronchial injury Vocal cord injury Aspiration
Respiratory risks
Oral injury Atelectasis Laryngospasm and bronchospasm
Postoperative respiratory depression
Pneumonia and postoperative pulmonary complications
Cardiac complications
Hypotension
Myocardial infarction and ischaemia Cardiac arrest Neurological complications
Peripheral and central axial nerve damage
Stroke and brain damage Headaches Confusion
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Risk factors Congenital and acquired facial and oral deformities (e.g. micrognathia, burn injuries, obesity, pregnancy); restricted neck movement (e.g. rheumatoid arthritis, cervical spine injury); oral, pharyngeal, laryngeal or tracheal tumours Pre-existing pathology (e.g. tumour); intubation injury (e.g. use of stylet, gum elastic bougie) Passage of oral ETT Emergency surgery (due to inadequate starvation period, pain and opioids reducing gastric emptying) Pregnancy (increased gastric acid production, reduced gastrooesophageal junction tone, increased intra-abdominal contents) Intra-abdominal pathology (increased intra-abdominal pressure) Hiatus hernia and/or gastro-oesophageal reflux disease Use of ETT and LMA; presence of loose, capped or crowned teeth Prolonged anaesthesia; failure to use PEEP; laparoscopic or abdominal procedures Pre-existing bronchial hyperreactivity (e.g. in asthma); paediatric patients; recent RTI (within 4 weeks); induction, intubation, positioning and emergence; light anaesthesia and stimulation during surgery Pre-existing medical conditions (e.g. respiratory disease, dementia, cardiac failure) Postoperative sedation (drug-related) Inadequate reversal of neuromuscular blockade Airway obstruction (e.g. retained secretions, failure of patient to maintain own airway) Respiratory narcosis (secondary to elevated carbon dioxide levels) Age >60 years; COPD; ASA grade of >1; functional dependency; congestive cardiac failure; prolonged surgery, surgery type (aneurysm, thoracic, head and neck, vascular, emergency); general anaesthesia; hypoalbuminaemia Drug-related (e.g. relative overdose of induction agent); hypovolaemia; regional anaesthesia; TIVA; purposeful anaesthetic technique (‘hypotensive anaesthesia’) See Table 2 Includes risks as in Table 2, and respiratory complications (causing hypoxaemia) Surgical positioning (see main text); use of tourniquets, BP cuffs, arm supports, etc.; conditions causing reduced perfusion of nerve tissue (e.g. diabetes, atherosclerosis); emaciated and obese patients; hypotensive anaesthesia; direct injury (due to chemical injection, needle injury, compression) Previous history of stroke; increasing age; surgery type (head, neck and cardiac); hypoxaemia; hypotension Caffeine withdrawal; drug-related (e.g. vasodilators, or withdrawal of opioids); dehydration/hypovolaemia Increasing age; pre-existing neurological conditions (e.g. previous stroke, dementia); pre-existing respiratory or cardiac conditions; high levels of preoperative alcohol consumption; poorly sighted or hard of hearing individuals (as they will find it difficult to orientate themselves); prolonged surgery; surgery type (cardiac surgery in particular)
Ó 2010 Elsevier Ltd. All rights reserved.
CLINICAL ANAESTHESIA
Eye injuries
Corneal abrasions Blindness
Drug-related complications
Anaphylaxis Awareness
Open eyes while under anaesthesia Hypotensive anaesthesia; pre-existing atherosclerotic or hypertensive eye disease; compression (e.g. in prone position) Previous exposure to allergen Emergency surgery; inadequate monitoring (e.g. failure of anaesthetist to notice changes in cardiovascular parameters); failure to deliver adequate anaesthesia; TIVA (e.g. with loss of cannula); intubation and extubation, patient positioning; Use of muscle relaxants Genetic predisposition Suxamethonium apnoea (genetic predisposition) Pregnancy; drug-related; neonates and elderly; liver disease; burns patients; malnutrition Drug-related (e.g. nitrous oxide, opioids); pain; surgery type (e.g. ENT, laparoscopic and gynaecological procedures); female; nonsmokers; previous PONV and travel sickness Anaesthetic-related (e.g. vasodilation); failure to warm patient adequately perioperatively; hypothermia prior to theatre admission
Malignant hyperpyrexia Pseudocholinesterase deficiency
PONV
Hypothermia and shivering
ASA, American Society of Anesthesiologists; BP, blood pressure; COPD, chronic obstructive pulmonary disease; CVA, cerebrovascular accident; ENT, ear, nose and throat; ETT, endotracheal tube; LMA, laryngeal mask airway; PEEP, positive end-expiratory pressure; PONV, postoperative nausea and vomiting; RTI, respiratory tract infection; TIVA, total intravenous anaesthesia.
Table 1
Perioperative cardiac risk factors. Defined by the ACC/AHA (2007) in their working party report by Fleischer et al. Active cardiac conditions
Unstable coronary syndromes (e.g. unstable or severe angina, recent MI) Decompensated heart failure (NYHA functional class IV; worsening or new-onset of heart failure) C Significant arrhythmias (e.g. third degree heart block, Mobitz type II block, symptomatic ventricular arrhythmias, uncontrolled AF, symptomatic bradycardia) 2 C Severe valvular disease (severe aortic stenosis [gradient >40 mmHg, area <1 cm , symptomatic], symptomatic mitral stenosis [exertional dyspnoea, presyncope, heart failure]) History of heart disease History of compensated or prior heart failure History of cerebrovascular disease Diabetes mellitus Renal insufficiency Age >70 years Abnormal ECG (LVH, LBBB, ST-T abnormalities) Rhythm other than sinus Uncontrolled systemic hypertension C Vascular surgery (reported risk of cardiac death and non-fatal MI >5%) e aortic and major vascular surgery, peripheral vascular surgery C Intermediate risk (1e5%) e cavity surgery, carotid endarterectomy, head and neck surgery. Orthopaediac surgery, prostate operation C Low risk (<1%) e endoscopic procedures, superficial surgery, cataract operations, ambulatory surgery <4 METs C C
Major risks
Minor risk factors (markers for cardiac disease that have not been proven to independently increase risk) Surgical factors
Functional capacity
ACC, American College of Cardiology; AF, atrial fibrillation; AHA, American Heart Association; ECG, electrocardiography; LBBB, left bundle branch block; LVH, left ventricular hypertrophy; MET, metabolic equivalent; MI, myocardial infarction; NYHA, New York Heart Association.
Table 2
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compression and stretching (which occur during positioning and through the use of automated blood pressure (BP) cuffs and tourniquets) hypoperfusion (which may be local compression of vessels supplying the nerve or more general hypotension) direct injury (e.g. during line insertions) chemical toxicity idiopathic. Risk factors include: prone, lateral and lithotomy positions and extended/rotated arm positions orthopaedic procedures and spinal, brain, cardiac or vascular surgery diabetes, rheumatoid or osteoarthritis and athelosclerosis increasing age extremes of body mass index (BMI) B Low BMIs (<20) have less fat deposits to protect bony areas B Obese patients are at risk of compression at flexed areas and the sacrum, for example, and require more supports for positioning which have the potential to impinge on nerves. The risk of permanent damage is <1:5000. Spinal cord damage secondary to general anaesthesia is rare but is usually permanent and serious in nature (e.g. loss of bladder and bowel function, paralysis). In terms of anaesthetic risk, this is usually caused by an inadequate spinal cord blood supply.
respiratory complications all increase the risk of this problem when it presents early. Age is the only risk factor for late POCD.
Eye injuries Corneal abrasions causing symptoms occur in 1:1750 anaesthetics. Blindness secondary to retinal artery occlusion or hypotension is very rare with an incidence of <1 in 120,000.5
Drug-related risks Anaphylaxis The incidence of anaphylactic reactions is 1:10,000e20,000. There is an increased prevalence of these reactions amongst anaesthetic patient populations, due mainly to the use of primarily intravenous agents and the potential for polypharmacy. Muscle relaxants are the most common cause of anaphylaxis (up to 60% of cases related to anaesthesia) with latex (20%), antibiotics (15%) and colloids (4%) also being precipitants. Local anaesthetics, intravenous induction agents, opioids and non-steroidal anti-inflammatory drugs are infrequent causes. There are no reported cases of anaphylaxis to inhalational anaesthetic agents. The most common presentation under anaesthesia is cardiovascular collapse for which there is a 10% mortality.6 Awareness The quoted incidence of awareness is very variable. The commonly stated risk is about 1%, but this includes different anaesthetic approaches to current practice and depends on how awareness is defined. A recent prospective study gave an incidence of awareness with recall of 0.6%,7 but a large retrospective study of American patients showed an incidence of approximately 1:14,000.8 Patients particularly at risk are those undergoing emergency (especially caesarean section and trauma surgery) and heart surgery and surgery performed at night. Premedication with benzodiazepines may confer some protective benefits.
Stroke and brain damage Stroke is more common in patients with a previous history, the elderly and those undergoing head, neck (especially carotid artery) and heart surgery. Brain damage as a consequence of anaesthesia is extremely rare. Likely causes are inadvertent hypoxia or prolonged hypotension. Headaches, drowsiness and postoperative confusion and cognitive dysfunction Neurological sequelae following anaesthesia are common but usually temporary. The anaesthetic agents used are often implicated, although headaches are frequently related to caffeine withdrawal. Postoperative confusion, manifesting as hallucinations, loss of orientation or changes in personality, can occur. Patients at risk of confusion: are the elderly have pre-existing acute or chronic illnesses have dementia, other neurological conditions or had previous strokes are heavy alcohol consumers (the usual precipitating cause of confusion being alcohol withdrawal) those with pre-existing visual or auditory disturbance. Postoperative cognitive dysfunction (POCD) has been described, where patients cannot perform higher order functions, have poor memory and lack of concentration, which may stop them returning to work. POCD is linked to cardiac surgery in particular, but occurs in other types of surgery too. One multicentre study into noncardiac surgery showed that approximately one-quarter of patients over 60 years old had POCD at one week postoperatively and one-tenth at 3 months (compared with 3.4% and 2.8%, respectively, in controls).4 Increasing age, duration of anaesthesia, low educational level, repeat surgery, postoperative infections and
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Malignant hyperpyrexia and pseudocholinesterase deficiency The incidence of malignant hyperpyrexia is 1:10,000e15,000 with a 2e3% mortality. Pseudocholinesterase deficiency is inherited or acquired. Four percent of the Caucasian population carry a version of the gene causing the genetic variety. Postoperative nausea and vomiting (PONV) At least one-third of patients experience PONV. Women, children, non-smokers and those with previous PONV or travel sickness are more commonly affected. Hypothermia and shivering The potential problems of perioperative temperatures <36 C include increased blood loss, longer recovery, morbid cardiac events, increased wound infection and longer hospital stays.9 Shivering can occur without a change in body temperature. Approximately 25% of patients experience this unpleasant but self-limiting side effect.
Pain Although not an anaesthetic risk per se, pain is a common complication of surgery that is under the remit of the
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3 Sawyer RJ, Richmond MN, Hickey JD, Jarratt JA. Peripheral nerve injuries associated with anaesthesia. Anaesthesia 2000; 55: 980e91. 4 Moller JT, Cluitmans P, Rasmussen LS, et al. Long-term postoperative dysfunction in the elderly: ISPOCD1 study. Lancet 1998; 351: 857e61. 5 Jenkins K, Baker AB. Consent and anaesthetic risk. Anaesthesia 2003; 58: 962e84. 6 Association of Anaesthetists of Great Britain & Ireland (AAGBI). Suspected anaphylactic reactions associated with anaesthesia [Online] Available at: http://www.aagbi.org/publications/guidelines/ docs/anaphylaxis_2009.pdf; 2009 (accessed 28 Apr 2010). 7 Errando CL, Sigl JC, Robles M, et al. Awareness with recall during general anaesthesia: a prospective observational study of 4001 patients. BJA 2008; 101: 178e85. 8 Pollard RJ, Coyle JP, Gilbert RL, Beck JE. Intraoperative awareness in a regional medical system: a review of 3 years’ data. Anesthesiology 2007; 106: 269e74. 9 National Institute for Health and Clinical Excellence. Clinical practice guideline: the management of inadvertent peri-operative hypothermia in adults (full guidance) [Online] Available at: http://www.nice.org.uk/ nicemedia/pdf/CG65Guidance.pdf; 2008 (accessed 9 Feb 2010). 10 Cook TM, Counsell D, Wildsmith JAW. Major complications of central neuraxial block: report on the Third National Audit Project of the Royal College of Anaesthetists. Br J Anaesth 2009; 102.
anaesthetist. A significant proportion of patients experience pain and this has implications in terms of lengthened hospital stay and patient satisfaction ratings. It has also been linked with PONV. Poorly controlled postoperative thoracic or abdominal pain increases the chances of respiratory complications, secondary to reduced secretion clearance and atelectasis, and significant pain will prevent early mobilization.
Death The risk of death related solely to anaesthesia is approximately 1:100,000 for American Society of Anesthesiologists (ASA) grade I and II patients. The risk increases with higher ASA grading and emergency surgery. According to the last two Confidential Enquiry into Maternal and Child Health (CEMACH) reports, death attributable to anaesthesia in obstetric patients is low (0.3:100,000 maternities).
Regional anaesthesia Major complications of regional anaesthesia, as defined by the Royal College of Anaesthetists in their recent National Audit Project, include paraplegia, death, spinal or epidural infection or bleeding, nerve injury, spinal cord ischaemia and wrong route drug errors. Permanent injury occurs in 2e4.2:100,000 times and perioperative epidurals confer the most risk (8.2e17.4:100,000). The incidence of paraplegia and death is 0.7:100,000.10 Post-dural puncture headache is seen in approximately 1% of patients. Transient neurological damage occurs in 4e80:10,000 spinals and 1e10:10,000 epidurals. Urinary retention is common. Systemic toxicity has an incidence of 1:10,000, and seizures and cardiac arrest may result.
FURTHER READING Confidential enquiry into perioperative deaths (CEPOD) and confidential enquiry into maternal and child health (CEMACH) reports. (Triennial reports into the risks associated with surgery and the risks posed to the mother and newborns, which gives detailed analysis of the anaesthetic complications associated with these groups.) Difficult Airway Society. Guidelines [Online] Available at: http://www.das. uk.com/guidelines/guidelineshome.html; 2010 (accessed 28 Apr 2010). (The society’s guidelines on the management of “can’t intubate, can’t ventilate” situations is available here and other algorithms for the managing the difficult airway are also available. The results of the National Audit Project 4, which is looking at complications resulting from airway management, are also due to be published on the society’s website shortly.) Inouye SK. Delirium in older persons. N Engl J Med 2006; 354: 1157e65. (A review article looking at the epidemiology, clinical characteristics, methods of prevention and management of delirium in people over 65 years of age.) Royal College of Anaesthetists. Risk information leaflets [Online] Available at: http://www.rcoa.ac.uk/index.asp?PageID¼1209; 2009 (accessed 28 Apr 2010). (These are very useful patient information leaflets pertaining to the common concerns of patients prior to an anaesthetic and the potential serious consequences.)
Equipment and theatre risks The theatre poses a constant risk to the patient. Diathermy burns, theatre fires and cross infection are examples that are not considered in detail here, but historically have made headlines. All equipment has the potential to fail and even simple devices such as blood pressure cuffs can harm patients. The anaesthetist as a member of the multidisciplinary team has a duty to ensure that all policies implemented to improve patient safety are followed in the hazardous environment of the operating theatre.A
REFERENCES 1 Heard AMB, Green RJ, Eakins P. The formulation and introduction of a “can’t intubate, can’t ventilate” algorithm into clinical practice. Anaesthesia 2009; 64: 601e8. 2 Contractor S, Hardman JG. Injury during anaesthesia. Cont Educ Anaesth Crit Care Pain 2006; 6: 67e70.
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