Do surgical trainees know how to administer local anaesthetic and deal with toxicity?

Transcription

1 Do surgical trainees know how to administer local anaesthetic and deal with toxicity? How junior surgeons measure up against their anaesthetic counterparts. N Blucher Core Surgical Trainee 1 D Pefanis Core Surgical Trainee 2 C Janes Registrar in Anaesthetics 3 R Ahluwalia Registrar in Trauma and Orthopaedics 2 1 Wirral University Teaching Hospital NHS Foundation Trust 2 Chelsea and Westminster Hospital NHS Foundation Trust 3 Oxford University Hospitals NHS Trust e4 DOI: / X

2 Figure 1 Questionnaire used in the study Local Anaesthesia Survey What is your present specialty?... What is your intended specialty?. What is your grade?. What postgraduate qualifications do you hold?.. Year How often do you administer local anaesthetic (LA) agents? a) Daily b) Weekly c) Monthly d) Rarely e) Never Please list the agent(s) you use most commonly and give the maximum toxic dose for each. a) Max dose: mg/kg With adrenaline: mg/kg b) Max dose: mg/kg With adrenaline: mg/kg What mass of LA is contained in the following solutions? a) 20ml of 1% lidocaine: mg b) 10ml of 0.5% bupivacaine: mg What are the signs and symptoms of LA toxicity?... Which treatment should be given to a patient with suspected LA toxicity? Which specific agent has recently been included in the guidelines for treating LA toxicity? Please give name and dose.... Local anaesthetic (LA) toxicity is a rare but potentially life-threatening consequence occurring in 7.5 to 20 per 10,000 peripheral nerve blocks. 1 Severe toxicity can induce seizures, coma, cardiac arrhythmias, circulatory collapse and even death if not recognised and treated promptly. It is generally resistant to standard resuscitation measures. Nowadays, many surgical procedures are performed using local anaesthesia outside the theatre setting, without the presence of an anaesthetist and immediate monitoring or resuscitation facilities. 2 Consequently, all surgeons using LA have the responsibility to be competent in managing severe toxicity. Preventative measures include access to a secure intravenous line and resuscitation equipment. Surgeons should be aware or have a working knowledge of the lowest effective safe dose of LA to be used and maximum dosing recommendations. Standard practice should include needle aspiration prior to injecting LA to prevent inadvertent intravenous administration. Appropriate use of adrenaline as an adjuvant may be used if larger doses of LA are required. 3 The Association of Anaesthetists of Great Britain and Ireland (AAGBI) regularly publish safety guidelines. Since 2007 and in subsequent updated guidelines, the AAGBI has recommend the use of lipid emulsion (Intralipid ; Fresenius Kabi, Bad Homburg, Germany) for the management of severe LA toxicity, 4 following evidence supporting its use in the reversal of cardiotoxicity in LA overdose. 5 The mechanism of action is proposed to be the creation of an expanded intravascular lipid phase, shifting the equilibrium of the toxic drug from tissue to the newly formed lipid sink. 6,7 These guidelines have been successfully disseminated in the field of anaesthetics. 8 The purpose of our study was to assess the knowledge of junior surgeons in the safe usage and administration of LAs compared with anaesthetic trainees, and whether they could recognise and manage severe toxicity in accordance with current guidelines compared with anaesthetic colleagues. METHODS This study was performed prospectively during two six-month periods of training ( ) in two deaneries, in the form of a questionnaire (Figure 1). The survey was split into sections concerning demographics, frequency of administration, maximum dosing of their standard LA and identification of signs of toxicity. Questions were asked to assess trainees specific knowledge on the use of Intralipid and the management of toxicity, with the AAGBI guidelines as the referenced standard. The format included closed, scaled and open-ended questions. Sample group Two hundred and two surgical and anaesthetic trainees in deanery-approved posts in all stages of training were directly approached and supervised to complete a questionnaire without any aids. The following surgical specialties were included: general, orthopaedic and plastic surgery (all specialties where LA administration is common). All participants were stratified according to whether they had completed the membership examination and also depending on their LA usage (daily, weekly, monthly or rarely). Statistical analysis Data were analysed using R statistical software version (R Foundation for Statistical Computing, Vienna, Austria). The relationship between binary and categorical variables was analysed using logistic regression analysis, with calculation of odds ratio (OR) and 95% confidence interval (CI). Groups were also compared using Student s t-test. All p-values were two-sided and a p-value of <0.05 was considered statistically significant. RESULTS A total of 202 trainees were approached and asked to complete the questionnaire. The response rate was 67.8% (96/140 surgical and 41/62 anaesthetic). The surgeons were a mixture of registrars, core trainees and F2 doctors. Twenty-eight surgeons (29.2%) had completed the fellowship and forty-six e5

3 % Lidocaine 0.5% Bupivacaine Figure 2 Percentage of correct answers for the calculation of local anaesthetic mass in 1% lidocaine and 0.5% bupivacaine Surgeons Anaesthetists Figure 3 Percentage of respondents aware of Intralipid in their practice Both Surgeons Anaesthetists (47.9%) had completed the membership examination. Of the surgical trainees assessed, there was a slight predominance of orthopaedic trainees (n=36, 37.5%) compared with general surgery (n=33, 34.3%) and plastic surgery (n=27, 28.1%) trainees. Most administered LA on a weekly or daily basis (n=84, 87.5%). Twenty-three (56.1%) of the anaesthetic trainees had successfully completed fellowship examinations and all were at level CT3 or above. All routinely administered LA regularly (either daily or weekly). Most surgeons used either lidocaine (n=82) or bupivacaine (n=65). All anaesthetists used bupivacaine (or a derivative such as levobupivacaine) and lidocaine. Basic science knowledge of local anaesthetic One question posed to the trainees was: What mass of LA is contained in the following solutions? a) 20ml of 1% lidocaine; b) 10ml of 0.5% bupivacaine. Only 24 surgical trainees (25.0%) could calculate the correct amount of the two types of LA of a certain concentration and volume, with a further 28 (29.2%) calculating the amount of only one of the LAs correctly (Figure 2). Another question asked whether trainees could calculate the maximum single safe volume of a particular concentration of LA. A total of 46 surgical trainees (47.9%) answered this correctly. Twenty of these surgeons administered LA on a weekly or daily basis and twenty-three were at registrar level or above. In contrast, all the anaesthetic trainees administered LA daily or weekly, and 40 (97.6%) knew the correct maximum toxic limit of at least two agents and could calculate the LA amount correctly. Ability to deal with severe toxicity The systemic toxic effects due to LA overdose primarily involve the central nervous and cardiovascular systems. In mild toxicity, this may well present with lightheadedness, dizziness, tinnitus, circumoral numbness, abnormal taste, confusion and drowsiness, and can include tachycardia and a rise in blood pressure. In severe cases, this can lead to tonic clonic convulsion resulting in progressive loss of consciousness, coma, respiratory depression and respiratory arrest. For cardiovascular collapse to occur, four to seven times the LA dose needs to be injected intravascularly. 9 Most trainee surgeons could recognise these signs and symptoms of LA toxicity (n=59, 61.4%). Fifty-nine surgeons (61.4%) were also able to name supportive therapy to be implemented in the case of recognised toxicity. Fifteen of these fifty-nine surgeons also calculated the correct maximal dose required for their chosen LA. Surgeon grade and frequency of use of LA was not associated with any statistically significant difference in the general approach to managing LA toxicity. Only seven surgical trainees (7.3%) were aware of the use of Intralipid for the management of severe toxicity (Figure 3). There was no difference in the knowledge of Intralipid according to the frequency of e6

4 use or indeed with any other subgroup. All anaesthetic trainees could name at least three signs of toxicity, were familiar with the use of Intralipid and identified the safe dose of their chosen LA correctly. Analysis by surgical seniority Among F2 doctors (n=16), seven could calculate the correct maximal dose and three the correct amount of LA used. Twelve could instigate some treatment for toxicity and one mentioned the use of Intralipid in the event of toxicity. There were 33 core surgical trainees of various levels in the study; 17 could calculate the safe maximal dose. There were 25 who were able to recognise 3 signs or symptoms of toxicity and 16 could name a form of treatment, with one person identifying Intralipid. Grouping all the SpR grade surgeons (n=47), 22 could calculate the safe dose of LA. There were 29 who correctly named 3 or more symptoms and signs of toxicity, 19 could start recovery treatment and 5 identified Intralipid. Even so, a large number of the surgical trainees failed to calculate the safe dose of both their chosen LAs (n=50, 52.1%, p<0.05). Thirty-two of them had completed either membership and/or fellowship examinations. There was a trend for core trainees to be more aware of dose calculation than foundation doctors (OR: 10, 95% CI: , p=0.051) and they also seemed more aware of dose calculation than all other grades of surgical trainee (OR: 10, 95% CI: , p=0.051). Analysis by frequency of usage Surgeons using LA very frequently (weekly or daily) were more likely to be able to calculate the correct dose of their chosen anaesthetic (OR: 8.4, 95% CI: , p=0.013). In comparison, all anaesthetic trainees knew the maximum and safe LA doses and treatment of toxicity. DISCUSSION Until recently, LA toxicity was deemed difficult to manage with standard Advanced Life Support resuscitation. 10 The increasing body of evidence led to the formulation of the current guidelines by the AAGBI and has also been taken up by some surgical groups (eg American Academy of Orthopaedic Surgeons). 11 Current evidence indicates Intralipid should be considered, alongside standard resuscitation, as an essential part of managing LA toxicity, especially when bupivacaine has been used. 11 This is a common LA administered by surgical trainees, as shown in this study. Owing to the recent evidence and guidelines, Intralipid should be known about and readily available in areas where surgical trainees use LA. 12 Hamann et al suggest Intralipid is available in the majority of acute London hospitals but perhaps not in settings outside theatre and obstetric departments. 13 According to another study, the AAGBI guidelines are available in most hospitals, 8 which may indicate a lack of effective dissemination from within trusts, as our results indicate. This study implies an important difference in the training of anaesthetists and surgeons in LA administration even though both groups use LAs routinely. This may reflect the fact that most surgical trainees administer LA in a theatre environment, where an anaesthetist is available. Even so, some of these LAs are administered in the outpatients department or in the community. For example, bupivacaine is used for LA injections into joints, nerve injections (eg Morton s neuroma) and field blocks by a large number of orthopaedic surgeons. Another reason why less educational importance is given to surgeons on the availability and use of Intralipid may be the low risk of toxicity by peripheral nerve block (incidence of 20 out of 10,000 peripheral nerve blocks resulting in systemic LA toxicity). 9 This study highlights the lack of knowledge of dosing, a skill that is supposed to be taught and examined at medical school but that is not reinforced in later years or by membership or fellowship examinations. It also identifies a lack of knowledge of Intralipid in surgical trainees. With the recent incorporation of the AAGBI guidelines into the Advanced Life Support manuals, a precedent has been set to increase awareness of Intralipid. Should it be included into the syllabus for surgical training? This has had an obvious impact in dissemination of this innovation among anaesthetic colleagues. 8 Knowledge of Intralipid is important for safe medical practice and it is worth remembering, as is General Medical Council guidance stating that doctors should work within the limits of your competence and that they should provide effective treatments based on the best available evidence. 14 Clearly, these two fundamental principles need urgent attention among the surgical community who frequently use LA. Limitations to this study include a small sample size and statistical significance was therefore rarely attained. Nevertheless, the fundamental point that there is lack of knowledge about Intralipid still attains significance. There may also have been a selection bias in sampling due to the fact that surgeons were based in the UK. There have been criticisms that Intralipid itself lacks robust evidence in the form of randomised controlled trials 15,16 as LA toxicity is rare and such a study may not be ethically approved. Despite this, there have been several case reports published 17,18 and convincing animal studies that have been systematically reviewed. 19,20 It appears reasonable to consider Intralipid in the case of cardiac arrest that is refractory to standard resuscitation since relatively little harm could come to the patient at such a stage. 21 CONCLUSIONS Although surgical trainees use LA regularly, there appear to be deficits in their basic science knowledge of LA in terms of safe dosing and calculating the correct doses of commonly used LAs for administration. The current AAGBI guidelines, including Intralipid administration in LA toxicity, are largely unknown among trainee surgeons. These are issues that should be addressed e7

5 in surgical training to prevent dependence on anaesthetic colleagues and ensure patient safety. REFERENCES 1. Corcoran W, Butterworth J, Weller RS et al. Local anesthetic-induced cardiac toxicity: a survey of contemporary practice strategies among academic anesthesiology departments. Anesth Analg 2006; 103: 1,322 1, Culp WC, Culp WC. Practical application of local anesthetics. J Vasc Interv Radiol 2011; 22: Lui KC, Chow YF. Safe use of local anaesthetics: prevention and management of systemic toxicity. Hong Kong Med J 2010; 16: Association of Anaesthetists of Great Britain and Ireland. AAGBI Safety Guideline: Management of Severe Local Anaesthetic Toxicity. London: AAGBI; Rosenblatt MA, Able M, Fischer GW et al. Successful use of a 20% lipid emulsion to resuscitate a patient after a presumed bupivicaine-related cardiac arrest. Anesthesiology 2006; 105: Weinberg GL, VadeBoncouer T, Ramaraju GA et al. Pretreatment or resuscitation with a lipid infusion shifts the dose-response to bupivacaine-induced asystole in rats. Anesthesiology 1998; 88: 1,071 1, Rothschild L, Bern S, Oswald S, Weinberg G. Intravenous lipid emulsion in clinical toxicology. Scand J Trauma Resusc Emerg Med 2010; 18: Picard J, Ward SC, Zumpe R et al. Guidelines and the adoption of lipid rescue therapy for local anaesthetic toxicity. Anaesthesia 2009; 64: Bukbirwa H, Conn D. Toxicity from local anaesthetic drugs. Update in Anaesthesia 1999; 10: Dix SK, Rosner GF, Nayar M et al. Intractable cardiac arrest due to lidocaine toxicity successfully resuscitated with lipid emulsion. Crit Care Med 2011; 39: ASRA Recommendations on Systemic Toxicity of Local Anesthetics. American Academy Of Orthopaedic Surgeons. clinical2.asp (cited September 2014). 12. Bern S, Akpa BS, Kuo I, Weinberg G. Lipid resuscitation: a life-saving antidote for local anesthetic toxicity. Curr Pharm Biotechnol 2011; 12: Hamann P, Dargan PI, Parbat N et al. Availability of and use of Intralipid (lipid rescue therapy, lipid emulsion) in England and Wales. Emerg Med J 2010; 27: General Medical Council. Good Medical Practice. London: GMC; Alfred SP. Intralipid: having leapt, should we now check the view? Emerg Med J 2010; 27: Kosh MC, Miller AD, Michels JE. Intravenous lipid emulsion for treatment of local anesthetic toxicity. Ther Clin Risk Manag 2010; 6: LipidRescue Resuscitation. lipidrescue.org. (cited September 2014). 18. Leskiw U, Weinberg GL. Lipid resuscitation for local anesthetic toxicity: is it really lifesaving? Curr Opin Anaesthesiol 2009; 22: Felice K, Schumann H. Intravenous lipid emulsion for local anesthetic toxicity: a review of the literature. J Med Toxicol 2008; 4: Jamaty C, Bailey B, Larocque A et al. Lipid emulsions in the treatment of acute poisoning: a systematic review of human and animal studies. Clin Toxicol 2010; 48: Corman SL, Skledar SJ. Use of lipid emulsion to reverse local anesthetic-induced toxicity. Ann Pharmacother 2007; 41: 1,873 1,877. e8