European Society of Anaesthesiologists COMPLICATIONS RELATED TO REGIONAL ANAESTHESIA - A NEW LOOK AT EPIDEMIOLOGIC DATA

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1 European Society of Anaesthesiologists COMPLICATIONS RELATED TO REGIONAL ANAESTHESIA - A NEW LOOK AT EPIDEMIOLOGIC DATA 8RC2 YVES AUROY, RENÉ AMALBERTI*, DAN BENHAMOU** Département d'anesthésie-réanimation, hôpital d'instruction des armées Percy, Clamart, France *Department of cognitive science, Aerospace Medical Research Institute (IMASSA), Brétigny-sur Orge, France **Département d'anesthésie réanimation, hôpital de Bicètre, université Paris Sud, France Saturday June 5, :00-15:45 Auditorium 3&4 INTRODUCTION In France, the number of regional anesthetic procedures performed annually has increased twelve-fold between 1980 and This tremendous increase can be linked to the perception that regional anaesthesia is associated with numerous advantages and with very few severe complications. This increase has been seen in both obstetrics and surgical procedures. Numerous new techniques have been described during these two decades and old techniques, such as lumbar plexus block, have been used again. Their use also explains the large development of regional anaesthesia. Because major complications related to traditional techniques are rare, their exact incidence is known only approximately 2. In 1998, Pr. K. Samii created a hot line service. The service is free of charge and is availble 24 hours a day. French anesthesiologists can phone to take advice from an expert about a complication which has occurred during or after regional anesthesia. Each expert remains on call during a one week period. Information about cases which have been declared is recorded and sent by to the other experts for reading and comments 3. This article comprises two sections. The first summarizes general epidemiologic data related to regional anaesthesia. In the second section, a new approach to analyse complications about regional anaesthesia is developed. EPIDEMIOLOGIC DATA MORTALITY The reported incidence of mortality related to regional anaesthesia varies greatly with the clinical setting. The mortality rate related to regional anaesthesia is about 1.9 deaths per million of caesarean deliveries 4 whereas, in non obstetrical studies, the mortality rate may be greater 2. It has been suggested that the mortality rate associated with regional anaesthesia is less than that with general anaesthesia 5-7. However, this is controversial 8, 9. The difficulty in establishing such a benefit may be due to confounding factors such as a patient s co-morbidity and the low overall mortality rate. Perhaps, such a comparison can only be made if the overall quality of perioperative care is optimal. MORBIDITY Systemic toxicity Systemic toxicity occurs due to excessive plasma concentration of local anaesthetic drugs occur, related to inadvertent intravascular injection or to significant absorption from the injection site. In studies performed before the use of ropivacaine, very few cardiac complications were described compared with a high incidence of seizures despite the widespread use of bupivacaine, known for its unquestionable cardiotoxicity Furthermore, the incidence of systemic toxicity of local anaesthetics and related seizures may have decreased recently. We believe that better physician information and improved practice patterns (lower doses, slow injection, test dose, fractionated injection ) are the major reasons for the decreased incidence and the excellent outcome. It is also possible that the introduction of ropivacaine in clinical practice during this period has played a role. Caution is necessary to prevent and detect systemic toxicity even when ropivacaine is administered. Cardiac arrest can indeed occur following administration of ropivacaine 14. The addition of a vasoconstrictor (usually adrenaline) to the anaesthetic solution (except with ropivacaine) decreases the peak plasma concentration Clinical signs which can precede seizures include light- headedness, dizziness, difficulty in eye focusing and tinnitus. 125

2 COMPLICATIONS RELATED TO CENTRAL NEURAXIAL BLOCKADE. Central neuraxial blockade leads to sympathetic block, which predisposes to systemic hypotension. Hypotension can occur as long as the sympathetic block persists. Precautions should be maintained as long as sympathetic blockade persists. The extent of sympathetic blockade is not easily quantified. As a surrogate, the sensory level can be clinically assessed. However, the sensory level consistently underestimates the sympathetic level of block. In order to decrease the likelihood of hypotension in elderly patients, it is advisable to decrease the dose of local anaesthetic administered. Treatment of hypotension due to sympathetic blockade often requires administration of vasopressor agents. The incidence of cardiac arrest is approximately 5 / neuraxial blocks performed. Bradycardia often precedes the onset of cardiac arrest. The following observations derive from analysis of accidents declared to the SOS RA system: i) several factors which predispose to cardiac arrest during anaesthesia for hip surgery. The risk probably increases from the start of the procedure to its end as the number of factors which can cause haemodynamic instability increase with time. Cardiac arrest can occur early because of an excessive dose of local anaesthetic administered to a relatively hypovolemic patient (due to a combination of undernutrition, preoperative fasting and diuretic therapy). Cardiac arrest can occur late when the patient becomes unable to cope with the cumulative additional risk factors: haemorrhage, cementing or position change. ii) the attention of anaesthesiologist is may be focused only on the sympathetic mechanism of hypotension while other causes (e.g haemorrhage, dehydration) are overlooked. iii) IV administration of a direct vasopressor (ie: adrenaline) should be early performed especially if ephedrine seems to be ineffective. NEUROLOGICAL COMPLICATIONS Neurological complications can occur after any type of regional anaesthesia. Mechanisms to explain these complications include direct nerve injury, nerve compression (ie haematoma) or neurological toxicity. Reports of spinal haematomas after spinal or epidural anaesthesia have generated concern regarding the safety of spinal or epidural anaesthesia in patients receiving low molecular weight heparins (LMWH) or platelet inhibitors drugs. New guidelines were recently published for the management of central neuraxial blockade in patients receiving perioperative LMWH 18. These guidelines could be extended to deep peripheral blocks (ie lumbar plexus block). Even if all local anaesthetics are potentially neurotoxic, this risk is actually clinically relevant only for spinal anaesthesia, probably because of the anatomical configuration of the spinal column. In animal models, lidocaine appears more neurotoxic than bupivacaine. Hyperbaric lidocaine has been implicated as a causative agent of cauda equina syndrome To minimize the risk of toxicity, it has been proposed that the dose of lidocaine be limited to 60 mg, the concentration to less than 2.5% and that the addition of adrenaline be avoided 22. Another proposition has also been discussed: if an alternative to lidocaine (as bupivacaine) exists, why not use it? Schneider et al have published reports of patients in whom pain in the buttocks and lower extremities occurred after spinal anaesthesia with 5% hyperbaric lidocaine 23. The lithotomy position is also a risk factor for this complication 24. These complications were named transient neurologic symptoms (TNS). The aetiology of TNS remains a subject to research and debate. However, TNS is mainly associated with lidocaine. Decreasing the concentration or the dose of lidocaine does not appear to decrease the incidence of TNS. COMPLICATIONS RELATED TO PERIPHERAL BLOCKS Although the posterior lumbar plexus block is considered to be a peripheral block, anaesthesiologists should be warned against the risk of cephalad diffusion of the local anaesthetic to the epidural or intrathecal space and should manage this block with at least the same vigilance as for a central neuraxial blockade. Indeed, this technique has gained popularity especially in elderly patients scheduled for hip or lower limb surgery because it is felt to be a safer alternative to spinal anaesthesia in terms of the associated risk of hypotension. It can also be combined with a sciatic nerve block. Both blocks can easily be performed without altering the patient s position. Severe cardiorespiratory complications associated with this lumbar plexus may be more frequent than after traditional spinal anaesthesia 3. According to recently published French guidelines, peripheral blocks should be performed with a nerve stimulator in awake, quiet and cooperative patients. However, several complications have been reported despite the use of a nerve stimulator 25. Inadequate patient positioning and/or non cooperative patients, insufficient physician experience, insufficient patient information on the procedure, excessive sedation or a less than gentle technique are factors that increase the risk of neurologic complications

3 LIMITATIONS OF THE CLASSICAL EPIDEMIOLOGIC APPROACH TO RISK FACTOR ANALYSIS. The classical epidemiologic approach has several limitations when applied to analysis of risk factor for adverse events associated with regional anaesthesia. The first is the low incidence of complications. A very large number of procedures must be examined to calculate an odd ratios of sufficient statistical power. This problem cannot be adequately addressed by grouping different regional anaesthesia procedures as each technique has its own inherent risks.increasing the time over which data are collected is also problematical for several reasons: - Catastrophe requires multiple failures The anaesthesia process entails changing mixtures of latent failures - Change introduces new patterns of failure - Changes are frequent in the anaesthesia process (new drugs, new devices, new techniques, new guidelines, etc.). Analysis of rare events requires specific statistical tools 26 27, 28. Since the incidence of complications is low, complications or incidents should be collected in a large database in order to improve the identification of root causes. Experience with non - medical incident reporting systems offers lessons applicable to the design of a medical reporting system. A medical reporting system should be non punitive, protected and voluntary A second limitation relates to factors which should be included in the investigation of complications. Most incidents have multiple contributory causative factors. In most of the published studies of anaesthetic complications, the causative factors studied are generally related to patients co-morbidities and physiologic or pathophysiologic effects of the anaesthetic. In the analysis of non medical accidents, human errors are generally identified. In the SOS RA database, the number of cases associated with wrong drug injection is similar to the number of neurological complications. Perhaps this observation should encourage us to extend our analysis to include errors, adverse events, accidents and complications and to investigate human factors in order to assess the real patient risk. The third limitation is related to the question: Does the complication relate to anaesthesia or not?. Perhaps as a result of medicolegal pressure, the analysis of a complication is mainly oriented to the question of imputation or blame. Risk evaluation in medicine comprises combined in three elements: the risk of the disease itself (or the patient co-morbidities), the risk entailed by the medical decision made, and the risk linked to implementing the therapy selected. These three risks, which are generally interrelated, make the issue of safety difficult to address. The question of imputation or blame is often directed to the different categories of of medical carers (surgery vs. anaesthesia). This orientation could dramatically limit the analysis of contributors of complications or accidents. For instance, in the SOS RA database, several cases refer to compartment syndromes of lower limbs. These complications occurred in patients who had lower limb surgery. Postoperative analgesia provided with a regional analgesia procedure (femoral catheter). We could consider these complications as unrelated to the regional anaesthesia procedure and more related to the surgical procedure. Thus, these complications may not be included in the analysis process. However, analysis of these complications showed that the excellent quality of analgesia (no pain at all) could have contributed to the delayed diagnosis of compartment syndrome. Complications usually described as related to regional anaesthesia are very specific and do not include human errors or adverse events. This point of view is probably too restrictive if one wants to explore the real risk. Complications or adverse events positioned at the interface of two (or more than two) groups of factors (ie surgery, anaesthesia) require careful investigation because of the additional potentials inadequacy of communication, training, turn-over, or team management. Tools exist to investigate and analyse clinical incidents 31. Using a process of analysis of adverse events, we can decrease the chance of oversimplified explanations. Such analysis focuses less on individuals and more on organisational factors. In non medical high risk systems (aviation, nuclear industries for instance), the formal investigation of adverse outcome is well established. An adverse event is always preceded by a complex chain of events and is generally multifactorial in origin. These factors relate problems with to communication or supervision, or insufficiency of training. From analysis of adverse events collected in SOS RA data base, several root causes have been identified. At least, four fundamental causes specific to regional anaesthesia have been identified. The first relates to the dual purposes of regional procedures: anaesthesia and postoperative analgesia. The doses of local anaesthetic administered for each purpose are different. In several cases, inappropriately great concentrations have been administered for postoperative analgesia (7.5% ropivacaine), contributing to the occurrence of convulsions. 127

4 The second fundamental cause relates to the large number of regional anaesthetic techniques available. Several different regional procedures (or combinations thereof) can be used for a particular surgical procedure. This complicates the process of identifying causative factors for adverse events. The third fundamental cause relates to the (sometimes) long duration of the effects of regional anaesthetic procedures. For instance, due to the long duration of effect (in particular for postoperative analgesia), patients, leaving the PACU, are considered as being still anaesthetised by nurses. Are ward nurses trained to take care of such patients? The fourth fundamental cause relates to the potential failure of regional anaesthesia. In several reported cases, it is clear that no back up plan had been made in the event of a failure of the regional anaesthetic technique. In conclusion, data related to complications and adverse events should be collected in large databases. The investigation of complications of anaesthesia should be performed with protocols directed to analyse systemic factors. The concept of complication should be enlarged to include errors and adverse events. REFERENCES 1. Clergue F, Auroy Y, Pequignot F, Jougla E, Lienhart A, Laxenaire MC. French survey of anesthesia in Anesthesiology 1999; 91: Auroy Y, Narchi P, Messiah A, Litt L, Rouvier B, Samii K. Serious complications related to regional anesthesia: results of a prospective survey in France. Anesthesiology 1997; 87: Auroy Y, Benhamou D, Bargues L, et al. Major complications of regional anesthesia in France: The SOS Regional Anesthesia Hotline Service. Anesthesiology 2002; 97: Hawkins JL, Koonin LM, Palmer SK, Gibbs CP. Anesthesia-related deaths during obstetric delivery in the United States, Anesthesiology 1997; 86: Rodgers A, Walker N, Schug S, et al. Reduction of postoperative mortality and morbidity with epidural or spinal anaesthesia: results from overview of randomised trials. Bmj 2000; 321: Ballantyne JC, Carr DB, deferranti S, et al. The comparative effects of postoperative analgesic therapies on pulmonary outcome: cumulative meta-analyses of randomized, controlled trials. Anesth Analg 1998; 86: Sorenson RM, Pace NL. Anesthetic techniques during surgical repair of femoral neck fractures. A meta-analysis. Anesthesiology 1992; 77: Rigg JR, Jamrozik K, Myles PS, et al. Epidural anaesthesia and analgesia and outcome of major surgery: a randomised trial. Lancet 2002; 359: Urwin SC, Parker MJ, Griffiths R. General versus regional anaesthesia for hip fracture surgery: a meta-analysis of randomized trials. Br J Anaesth 2000; 84: Brown DL, Ransom DM, Hall JA, Leicht CH, Schroeder DR, Offord KP. Regional anesthesia and local anestheticinduced systemic toxicity: seizure frequency and accompanying cardiovascular changes. Anesth Analg 1995; 81: Urban MK, Urquhart B. Evaluation of brachial plexus anesthesia for upper extremity surgery. Reg Anesth 1994; 19: Scott DB, Tunstall ME. Serious complications associated with epidural/spinal blockade in obstetrics : a two-year prospective study. Int J Obstet Anesth 1995; 4: Tanaka K, Watanabe R, Harada T, Dan K. Extensive application of epidural anesthesia and analgesia in a university hospital: incidence of complications related to technique. Reg Anesth 1993; 18: Klein SM, Pierce T, Rubin Y, Nielsen KC, Steele SM. Successful resuscitation after ropivacaine-induced ventricular fibrillation. Anesth Analg 2003; 97: Braid DP, Scott DB. Dosage of lignocaine in epidural block in relation to toxicity Effect of adrenaline on the systemic absorption of local anaesthetic drugs. Br J Anaesth 1966; 38: Mather LE, Tucker GT, Murphy TM, Stanton-Hicks DA, Bonica JJ. The effects of adding adrenaline to etidocaine and lignocaine in extradural anaesthesia II: Pharmacokinetics. Br J Anaesth 1976; 48: Wildsmith JA, Tucker GT, Cooper S, Scott DB, Covino BG. Plasma concentrations of local anaesthetics after interscalene brachial plexus block. Br J Anaesth 1977; 49: Horlocker TT, Heit JA. Low molecular weight heparin: biochemistry, pharmacology, perioperative prophylaxis regimens, and guidelines for regional anesthetic management. Anesth Analg 1997; 85: Rigler ML, Drasner K, Krejcie TC, et al. Cauda equina syndrome after continuous spinal anesthesia. Anesth Analg 1991; 72: Gerancher JC. Cauda equina syndrome following a single spinal administration of 5% hyperbaric lidocaine through a 25-gauge Whitacre needle. Anesthesiology 1997; 87: Loo CC, Irestedt L. Cauda equina syndrome after spinal anaesthesia with hyperbaric 5% lignocaine: a review of six cases of cauda equina syndrome reported to the Swedish Pharmaceutical Insurance Acta Anaesthesiol Scand 1999; 43:

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