Potential Neurotoxicity of Spinal Anesthesia With Lidocaine
2000; Elsevier BV; Volume: 75; Issue: 9 Linguagem: Inglês
10.4065/75.9.921
ISSN1942-5546
Autores Tópico(s)Pain Mechanisms and Treatments
ResumoSpinal (intrathecal) anesthesia has evolved into a safe, widely accepted method of anesthesia with many advantages. However, the past decade has seen a large number of case reports and incidence studies that implicate the local anesthetic (LA) lidocaine as being more neurotoxic than other commonly used LAs such as bupivacaine and tetracaine, based on patterns of clinical use current at the time of those reports. Available studies suggest a risk of persistent lumbosacral neuropathy after spinal lidocaine by single injection in about 1 in 1300 procedures and a risk as high as about 1 in 200 after continuous spinal anesthesia with lidocaine. While uncommon, this risk is probably an order of magnitude higher than the risk reported for other commonly used LAs or for general anesthesia. Spinal lidocaine is also implicated in the syndrome of transient neurologic symptoms (previously referred to as transient radicular irritation), manifest by pain or dysesthesia in the buttocks or legs after recovery from anesthesia. Although the pain typically resolves within 1 week without lasting sequelae, it can be severe in up to one third of patients with the syndrome. In addition to clinical studies, both whole animal and in vitro studies have shown that lidocaine can be neurotoxic at clinically available concentrations and that lidocaine is more neurotoxic than equipotent concentrations of other commonly used LAs. The mechanism of this neurotoxicity may involve changes in cytoplasmic calcium homeostasis and mitochondrial membrane potential. Spinal (intrathecal) anesthesia has evolved into a safe, widely accepted method of anesthesia with many advantages. However, the past decade has seen a large number of case reports and incidence studies that implicate the local anesthetic (LA) lidocaine as being more neurotoxic than other commonly used LAs such as bupivacaine and tetracaine, based on patterns of clinical use current at the time of those reports. Available studies suggest a risk of persistent lumbosacral neuropathy after spinal lidocaine by single injection in about 1 in 1300 procedures and a risk as high as about 1 in 200 after continuous spinal anesthesia with lidocaine. While uncommon, this risk is probably an order of magnitude higher than the risk reported for other commonly used LAs or for general anesthesia. Spinal lidocaine is also implicated in the syndrome of transient neurologic symptoms (previously referred to as transient radicular irritation), manifest by pain or dysesthesia in the buttocks or legs after recovery from anesthesia. Although the pain typically resolves within 1 week without lasting sequelae, it can be severe in up to one third of patients with the syndrome. In addition to clinical studies, both whole animal and in vitro studies have shown that lidocaine can be neurotoxic at clinically available concentrations and that lidocaine is more neurotoxic than equipotent concentrations of other commonly used LAs. The mechanism of this neurotoxicity may involve changes in cytoplasmic calcium homeostasis and mitochondrial membrane potential. The evolution of spinal (intrathecal) anesthesia into a safe, widely accepted technique is a major accomplishment of 20th century anesthesiology. For surgery below the chest, spinal anesthesia offers the clinical advantages of fast onset, dense block of nociceptive impulses, and preservation of the patient's airway without tracheal intubation. However, at midcentury the safety of spinal anesthesia was fiercely debated; eg, a 1952 textbook opined that "spinal anesthesia … is the most dangerous type of anesthesia for pregnant women."1Greenhill JP Analgesia and Anesthesia in Obstetrics. Charles C Thomas, Spring-field, Ill1952: 37Google Scholar This concern derived in part from well-publicized case reports of devastating neurologic injury after spinal anesthesia.2Ferguson FR Watkins KH Paralysis of the bladder and associated neurological sequelae of spinal anaesthesia (cauda equina syndrome).BrJSurg. 1938; 25: 735-752Google Scholar, 3Hutter CD The Woolley and Roe case: a reassessment.Anaesthesia. 1990; 45: 859-864Crossref PubMed Google Scholar, 4Kane RE Neurologic deficits following epidural or spinal anesthesia.Anesth Analg. 1981; 60: 150-161Crossref PubMed Google Scholar Because the needle is inserted below the termination of the spinal cord at L1–2, most neurologic complications of spinal anesthesia are manifest as a persistent lumbosacral radiculopathy. In the worst cases, this extends to a cauda equina syndrome with bowel and bladder sphincter incompetence, sexual dysfunction, sacral radicular paresthesias, and variable leg muscle weakness.5Adams RD Victor M Ropper AH Principles of Neurology. 6th ed. McGraw-Hill, New York, NY1997Google Scholar In the latter half of the century, the safety of spinal anesthesia appeared to improve significantly, probably because of the elimination of residual detergent and other contaminants from drugs and needles, better anesthesiologist education, and better patient selection to minimize the risk of neuraxial hematoma, infection, and exacerbation of preexisting neurologic disease.4Kane RE Neurologic deficits following epidural or spinal anesthesia.Anesth Analg. 1981; 60: 150-161Crossref PubMed Google Scholar By 1970, several large series of more than 10,000 spinal anesthetics had been published, with an incidence of persistent lumbosacral radiculopathy of only 1 to 2 per 10,000.6Nicholson MJ Eversole UH Neurologic complications of spinal anesthesia.JAMA. 1946; 132: 679-685Crossref PubMed Google Scholar, 7Phillips OC Ebner H Nelson AT Black MH Neurologic complications following spinal anesthesia with lidocaine: a prospective review of 10,440 cases.Anesthesiology. 1969; 30: 284-289Crossref PubMed Google Scholar, 8Moore DC Bridcnbaugh LD Spinal (subarachnoid) block: a review of 11,574 cases.JAMA. 1966; 195: 907-912Crossref PubMed Google Scholar, 9Dripps RD Vandam LD Long-term follow-up of patients who recei ved 10,098 spinal anesthetics: failure to discover major neurological sequelae.JAMA. 1954; 156: 1486-1491Crossref PubMed Google Scholar, 10Sadove MS Levin MJ Rant-Sejdinaj I Neurological complications of spinal anaesthesia.Can Anaestk Soc J. 1961; 8: 405-416Crossref PubMed Scopus (20) Google Scholar In 1981, the consensus was "that local anesthetics in concentrations normally used in clinical practice produce no direct toxic effects on the [spinal] cord.4Kane RE Neurologic deficits following epidural or spinal anesthesia.Anesth Analg. 1981; 60: 150-161Crossref PubMed Google Scholar Lidocaine was approved by the Food and Drug Administration (FDA) in 1948, and in time became the local anesthetic (LA) typically used when quick onset and regression of spinal anesthesia were desired. A single injection is appropriate for a 1- to 2-hour surgery, whereas multiple injections through a spinal catheter allow for longer surgery time while maintaining a rapid recovery profile. Lidocaine spinal anesthesia facilitates discharge of surgical outpatients within a few hours while decreasing recovery room time and nursing costs for surgical inpatients.11Frey K Holman S Mikat-Stevens M et al.The recovery profile of hyperbahc spinal anesthesia with lidocaine, tetracame, and bupivacainc.Clin Med. 1998; 23: 159-163Google Scholar Besides the convenience to patients, this also has considerable implications for decreasing the cost of health care. However, beginning in 1991, multiple reports appeared suggesting that spinal lidocaine causes a higher incidence of neurologic complications than does spinal anesthesia with other LAs. These reports do not contradict the large, frequently cited studies that established spinal anesthesia's safety.6Nicholson MJ Eversole UH Neurologic complications of spinal anesthesia.JAMA. 1946; 132: 679-685Crossref PubMed Google Scholar, 8Moore DC Bridcnbaugh LD Spinal (subarachnoid) block: a review of 11,574 cases.JAMA. 1966; 195: 907-912Crossref PubMed Google Scholar, 9Dripps RD Vandam LD Long-term follow-up of patients who recei ved 10,098 spinal anesthetics: failure to discover major neurological sequelae.JAMA. 1954; 156: 1486-1491Crossref PubMed Google Scholar, 10Sadove MS Levin MJ Rant-Sejdinaj I Neurological complications of spinal anaesthesia.Can Anaestk Soc J. 1961; 8: 405-416Crossref PubMed Scopus (20) Google Scholar With 1 exception7Phillips OC Ebner H Nelson AT Black MH Neurologic complications following spinal anesthesia with lidocaine: a prospective review of 10,440 cases.Anesthesiology. 1969; 30: 284-289Crossref PubMed Google Scholar (discussed subsequently), those studies did not include lidocaine because it was a relatively new agent, at the time of those studies (1954–1966), and ambulatory surgery was not a major element of many surgical practices at that time. More recent clinical, animal model, and in vitro studies strongly suggest that lidocaine has an intrinsic neurotoxic effect and that it is more neurotoxic than other commonly used LAs. This review focuses on the intrinsic neurotoxicity of lidocaine compared with other LAs administered during spinal anesthesia. Hence, in each of the cases and studies cited subsequently, the following classic causes of neurologic injury after spinal anesthesia, other than a direct neurotoxic effect of lidocaine, were excluded if possible12Wedel DJ Complications of central neuraxial blockade.Anesth Analg. 1999; 88: 111-116Google Scholar: direct physical trauma (manifest by a paresthesia with needle placement in an awake patient), a spinal or epidural hematoma or abscess (seen on computed tomography or magnetic resonance imaging), ischemic nerve injury in a patient subjected to prolonged hypotension or hypoxia, or preservatives or other contaminants inadvertently given with the anesthetic. Although the addition of vasoconstrictors and glucose to the spinal anesthetic may modulate the toxicity of the LA,13Drasner K Lidocaine spinal anesthesia: a vanishing therapeutic index? [editorial].Anesthesiology. 1997; 87: 469-472Crossref PubMed Scopus (62) Google Scholar this review concentrates on the effects of the LA itself. Because the mechanism of lidocaine neurotoxicity is still poorly understood, it does not provide an organizing framework for discussing the clinically observed neurotoxicity. This article first addresses the clinical manifestations of lidocaine neurotoxicity, reviewing its recent history as an unexpected sequela to the introduction of spinal microcatheters and the reappraisal of lidocaine prompted thereby. Available data on models and potential mechanisms are then reviewed. Continuous spinal anesthesia via a catheter in the subarachnoid space is an established anesthetic technique with several clinical advantages. In contrast to single injection, continuous spinal anesthesia can be titrated carefully to the desired dermatomal level and reinjected as needed, with improved hemodynamic stability.14Favarel-Garrigues JF Sztark F Petitjean ME Thicoipe M Lassie P Dabadie P Hemodynamic effects of spinal anesthesia in the elderly: single dose versus titration through a catheter.Anesth Analg. 1996; 82: 312-316PubMed Google Scholar, 15Schnider TW Mueller-Duysing S Johr M Gcrbcr H Incremental dosing versus single-dose spinal anesthesia and hemodynamic stability.Anesth Analg. 1993; 77: 1174-1178Crossref PubMed Google Scholar, 16Robson SC Samsoon G Boys RJ Rodeck C MoTgan B Incremental spinal anaesthesia for elective caesarean section: maternal and fetal haemodynamic effects.Br J Anaesth. 1993; 70: 634-638Crossref PubMed Google Scholar In contrast to epidural anesthesia, continuous spinal anesthesia offers a definite end point for appropriate placement (cerebrospinal fluid [CSF] aspiration)17Hurley RJ Lambert DH Continuous spinal anesthesia with a microcatheter technique: preliminary experience.Anesth Analg. 1990; 70: 97-102Crossref PubMed Google Scholar and requires only a fraction (0.1–0.2) of the epidural LA dose, with much faster onset and denser block. Before December 1989 in the United States, continuous spinal anesthesia was performed with a macrocatheter (19 or 20 gauge) placed through a 17- or 18-gauge needle. This large dural puncture greatly increased the risk of postdural puncture headache; thus, the technique was reserved for high-risk patients for whom its benefits were particularly attractive18Underwood RJ Experiences with continuous spinal anesthesia in physical status group IV patients.Anesth Analg. 1968; 47: 18-26Crossref PubMed Google Scholar and for older patients whose risk of headache was less than that for younger patients. Microcatheters (28–32 gauge) were then introduced, allowing continuous spinal anesthesia in younger patients with an acceptably low risk of headache and increasing its use. Case Reports.—In 1991, Rigler et al19Rigler ML Drasner K Krejcie TC et al.Cauda equina syndrome after continuous spinal anesthesia.Anesth Analg. 1991; 72: 275-281Crossref PubMed Google Scholar reported 4 cases from 3 different institutions where continuous spinal anesthesia resulted in the cauda equina syndrome, with causes other than direct neurotoxicity of the LA excluded. Of the 4 cases, 3 involved 5% lidocaine delivered through a microcatheter; the other case involved tetracaine delivered through a macrocatheter. Between December 1989 and May 1992, 11 cases of cauda equina syndrome occurred after 5% lidocaine was administered through spinal microcatheters; these were reported to the FDA, and the FDA took action to remove all spinal microcatheters from the market.20Benson JS FDA safety alert: cauda equina syndrome associated with small-bore catheters in continuous spinal anesthesia [press release]. Food and Drug Administration, Rockville, Md1992Google Scholar Studies Studies suggested that microcatheter-administered LA mixed poorly with CSF, resulting in sacral pooling with the potential for high perineural concentrations of drug.21Lambert DH Hurley RJ Cauda equina syndrome and continuous spinal anesthesia.Anesth Analg. 1991; 72: 817-819Crossref PubMed Google Scholar, 22Drasner K Models for local anesthetic toxicity from continuous spinal anesthesia.Reg Anesth. 1993; 18: 434-438PubMed Google Scholar The ability to reinject LA when the first dose did not spread adequately may have increased perineural LA concentration and exacerbated neurotoxicity in some instances. Between 1991 and 1993, 3 more microcatheter23Schell RM Brauer FS Cole DJ Applegate II, RL Persislent sacral nerve root deficits after continuous spinal anaesthesia.Can J Anaesth. 1991; 38: 908-911Crossref PubMed Google Scholar, 24Ross BK Coda E Heath CH Local anesthetic distribution in a spinal model: a possible mechanism of neurologic injury after continuous spinal anesthesia.Reg Anesth. 1992; 17: 69-77PubMed Google Scholar and 1 more macrocatheter25Mangar D Gonzalez Jr, W Linden C Gadolinium-enhanced magnetic resonance imaging and autopsy findings in a patient with cauda equina syndrome.Anesthesiology. 1993; 78: 785-787Crossref PubMed Google Scholar case of cauda equina syndrome, all involving 5% lidocaine, were reported. Additionally, 2 more cases involving 5% lidocaine delivered through a macrocatheter23Schell RM Brauer FS Cole DJ Applegate II, RL Persislent sacral nerve root deficits after continuous spinal anaesthesia.Can J Anaesth. 1991; 38: 908-911Crossref PubMed Google Scholar, 24Ross BK Coda E Heath CH Local anesthetic distribution in a spinal model: a possible mechanism of neurologic injury after continuous spinal anesthesia.Reg Anesth. 1992; 17: 69-77PubMed Google Scholar and through a catheter of undefined size27Auroy 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: 479-486Crossref PubMed Scopus (635) Google Scholar have been described as part of incidence studies. Except for the initial single case report involving tetracaine through a macrocatheter,19Rigler ML Drasner K Krejcie TC et al.Cauda equina syndrome after continuous spinal anesthesia.Anesth Analg. 1991; 72: 275-281Crossref PubMed Google Scholar there have been no other published reports of cauda equina syndrome occurring after continuous spinal anesthesia with any LA other than lidocaine. Incidence Studies.—There are few studies involving large numbers of patients to determine the actual incidence of the cauda equina syndrome after continuous spinal anesthesia with lidocaine. Most of the large studies of the safety of spinal anesthesia excluded continuous spinal anesthesia or included it as a small, unspecified portion of all spinal anesthetics.4Kane RE Neurologic deficits following epidural or spinal anesthesia.Anesth Analg. 1981; 60: 150-161Crossref PubMed Google Scholar, 7Phillips OC Ebner H Nelson AT Black MH Neurologic complications following spinal anesthesia with lidocaine: a prospective review of 10,440 cases.Anesthesiology. 1969; 30: 284-289Crossref PubMed Google Scholar, 8Moore DC Bridcnbaugh LD Spinal (subarachnoid) block: a review of 11,574 cases.JAMA. 1966; 195: 907-912Crossref PubMed Google Scholar, 9Dripps RD Vandam LD Long-term follow-up of patients who recei ved 10,098 spinal anesthetics: failure to discover major neurological sequelae.JAMA. 1954; 156: 1486-1491Crossref PubMed Google Scholar, 10Sadove MS Levin MJ Rant-Sejdinaj I Neurological complications of spinal anaesthesia.Can Anaestk Soc J. 1961; 8: 405-416Crossref PubMed Scopus (20) Google Scholar, 27Auroy 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: 479-486Crossref PubMed Scopus (635) Google Scholar The available data for lidocaine and other LAs, together with approximate 95% confidence intervals (CIs), are summarized in Table 1. Most studies are too small to give compact CIs. However, the CIs for nonlidocaine studies showing no neurotoxicity are much smaller than those for lidocaine studies showing no neurotoxicity, and the incidence and CIs for lidocaine studies demonstrating neurotoxicity are fairly consistent. The preponderance of data is consistent with an incidence of about 50 cases of cauda equina syndrome per 10,000 continuous spinal anesthetics. This is 1 to almost 2 orders of magnitude greater than previous estimates of a 1 in 10,000 risk of cauda equina syndrome for all types of spinal anesthesia using several different nonlidocaine LAs.4Kane RE Neurologic deficits following epidural or spinal anesthesia.Anesth Analg. 1981; 60: 150-161Crossref PubMed Google Scholar, 7Phillips OC Ebner H Nelson AT Black MH Neurologic complications following spinal anesthesia with lidocaine: a prospective review of 10,440 cases.Anesthesiology. 1969; 30: 284-289Crossref PubMed Google Scholar, 8Moore DC Bridcnbaugh LD Spinal (subarachnoid) block: a review of 11,574 cases.JAMA. 1966; 195: 907-912Crossref PubMed Google Scholar, 9Dripps RD Vandam LD Long-term follow-up of patients who recei ved 10,098 spinal anesthetics: failure to discover major neurological sequelae.JAMA. 1954; 156: 1486-1491Crossref PubMed Google Scholar, 10Sadove MS Levin MJ Rant-Sejdinaj I Neurological complications of spinal anaesthesia.Can Anaestk Soc J. 1961; 8: 405-416Crossref PubMed Scopus (20) Google ScholarTable 1Incidence of Probable Local Anesthetic Toxicity After Continuous Spinal Anesthesia*Dataare from studies thai reported a systematic investigation of all neurologic complications and the local anesthetics used. Microcatheter and macrocatheter data are combined. C = consecutive cases studied; CI = confidence interval; P = prospective; R – retrospective.ReferenceStudy designNo. of continuous spinal anestheticsLocal anestheticIncidencet†Cases of persistent lumbosacral neuropathy in which causes other than local anesthetic toxicity were excluded or clinically unlikely (eg, preexisting neurologic disease, needle trauma, hematoma, infection). per 10,000 continuous spinal anesthetics (95% CI‡Approximate 95% CI, calculated from data given in original report.37)Brown,28Brown S Fractional segmentai spinal anesthesia in poor risk surgical patients: report of 600 cases.Anesthesiology. 1952; 13: 416-428Crossref PubMed Google Scholar 1952R,C600Tetracaine0.0 (0.0–70)Dripps & Vandam,9Dripps RD Vandam LD Long-term follow-up of patients who recei ved 10,098 spinal anesthetics: failure to discover major neurological sequelae.JAMA. 1954; 156: 1486-1491Crossref PubMed Google Scholar 1954P, C839Tetracaine, procainc, dibucaine, piridocaine, pyrrolocaine0.0 (0.0–50)Mörch et al,29Mörch ET Rosenberg MK Truant AT Lidocaine for spinal anesthesia: a study of the concentration in the spinal fluid.Acta Anaesthiol Scand. 1957; 1: 105-115Crossref Google Scholar 1957P,C19Lidocaine0.0 (0.0–1 973)Moore & Bridenbaugh,8Moore DC Bridcnbaugh LD Spinal (subarachnoid) block: a review of 11,574 cases.JAMA. 1966; 195: 907-912Crossref PubMed Google Scholar 1966R,C433Tetracaine0.0 (0.0–97)Rao & Fl-Etr,30Rao TL El-Etr AA Anticoagulation following placement of epidural and subarachnoid catheters: an evaluation of neurologic sequelae.Anesthesiology. 1981; 55: 618-620Crossref PubMed Google Scholar 1981P,C847Tetracaine12 (0.0–73)Hurley & Lambert,17Hurley RJ Lambert DH Continuous spinal anesthesia with a microcatheter technique: preliminary experience.Anesth Analg. 1990; 70: 97-102Crossref PubMed Google Scholar 1990P33Lidocaine0.0 (0.0–1233)20Bupivacaine (90%), procainc0.0 (0.0–1886)Baxter,31Baxter AD Continuous spinal anesthesia: the Canadian perspective.Reg Anesth. 1993; 18: 414-418PubMed Google Scholar 1993R1000Lidocaine50 (12–125)Bevacqua,32Bevacqua BK Continuous spinal anesthesia: operative indications and clinical experience.Reg Anesth. 1993; 18: 394-401PubMed Google Scholar 1993P,C190Lidocaine, followed by bupivacaine or tetracaine52 (0.0–320)Bayhi et al,33Bayhi D Cork RC Hcaton JF Nolan TE Prospective survey of continuous versus single-injection spinal anesthesia in obstetrics.South Med J. 1995; 88: 1043-1048Crossref PubMed Google Scholar 1995P,C118Lidocaine0.0(0.0–351)Standl et al,34Standl T Eckert S Schulteam Esch J Microcatheter continuous spinal anaesthesia in the post-operative period: a prospective study of its effectiveness and complications.EurJ Artaesthesiol. 1995; 12: 273-279PubMed Google Scholar 1995P,C100Bupivacaine0.0 (0.0–413)Van Gcssel et al,35Van Gessel E Forster A Gamulin Z A prospective study of the feasibility of continuous spinal anesthesia in a university hospital.Anesth Analg. 1995; 80: 880-885PubMed Google Scholar 1995P,C100Bupivacaine (94%), tetracaine0.0 (0.0–413)Auroy et al,27Auroy 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: 479-486Crossref PubMed Scopus (635) Google Scholar 1997P540§Conservative estimation that continuous spinal anesthetics comprised 5% of all spinal anesthetics in the study by Auroy et al27 and others.26,38,39Lidocaine19(0.0–114)Horlocker et al,26Horlocker TT McGregor DG Matsushige DK Chantigian RC Schroeder DR Besse JA Perioperative Outcomes Group Neurologic complications of 603 consecutive continuous spinal anesthetics using macrocatheter and microcatheter techniques.Anesth Analg. 1997; 84: 1063-1070PubMed Google Scholar 1997R,C161Lidocaine62 (0.0–378)490Bupivacaine, tetracaine, procaine0.0 (0.0–86)Ilias et al,36Ilis WK Klimscha W Skrbensky G Weinstabl R Widhalm A Continuous microspinal anaesthesia: another perspective on mechanisms inducing cauda equina syndrome.Anaesthesia. 1998; 53: 618-623Crossref PubMed Scopus (12) Google Scholar 1998R,C915Bupivacaine0.0 (0.0–46)* Dataare from studies thai reported a systematic investigation of all neurologic complications and the local anesthetics used. Microcatheter and macrocatheter data are combined. C = consecutive cases studied; CI = confidence interval; P = prospective; R – retrospective.† Cases of persistent lumbosacral neuropathy in which causes other than local anesthetic toxicity were excluded or clinically unlikely (eg, preexisting neurologic disease, needle trauma, hematoma, infection).‡ Approximate 95% CI, calculated from data given in original report.37Altman DG Practical Statistics for Medical Research. Chapman and Hall, London, England1991Google Scholar§ Conservative estimation that continuous spinal anesthetics comprised 5% of all spinal anesthetics in the study by Auroy et al27Auroy 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: 479-486Crossref PubMed Scopus (635) Google Scholar and others.26Horlocker TT McGregor DG Matsushige DK Chantigian RC Schroeder DR Besse JA Perioperative Outcomes Group Neurologic complications of 603 consecutive continuous spinal anesthetics using macrocatheter and microcatheter techniques.Anesth Analg. 1997; 84: 1063-1070PubMed Google Scholar, 38Bouaziz H Mercier FJ Narchi P Poupard M Auroy Y Ben-hamou D Survey of regional anestheiic practice among French residents at time of certification.Reg Anesth. 1997; 22: 218-222Crossref PubMed Google Scholar, 39Horlocker TT McGregor DG Matsushige DK Schroeder DR Bcsse JA Perioperative Outcomes Group A retrospective review of 4767 consecutive spinal anesthetics: central nervous system complications.Anesth Analg. 1997; 84: 578-584PubMed Google Scholar Open table in a new tab A retrospective survey of Canadian anesthetists shortly after microcatheters were withdrawn from the market found 5 cases of cauda equina syndrome of 1000 micro catheter anesthetics given by the survey respondents. All 5 cases involved 5% lidocaine.31Baxter AD Continuous spinal anesthesia: the Canadian perspective.Reg Anesth. 1993; 18: 414-418PubMed Google Scholar Two studies that failed to identify neurologic complications due to continuous lidocaine spinal anesthesia lacked sufficient statistical power to detect reliably an incidence of 50 in 10,000, reporting on 1929Mörch ET Rosenberg MK Truant AT Lidocaine for spinal anesthesia: a study of the concentration in the spinal fluid.Acta Anaesthiol Scand. 1957; 1: 105-115Crossref Google Scholar and 11833Bayhi D Cork RC Hcaton JF Nolan TE Prospective survey of continuous versus single-injection spinal anesthesia in obstetrics.South Med J. 1995; 88: 1043-1048Crossref PubMed Google Scholar patients. Another report referred to 800 cases of continuous spinal anesthesia being performed over 4 years but provided outcome data only for a prospectively studied series of 190 patients, including 66 in whom microcatheters were used, who received 1 dose of lidocaine followed by bupivacaine or tetracaine. Of the 190 patients, 1 developed leg weakness that resolved over several months.32Bevacqua BK Continuous spinal anesthesia: operative indications and clinical experience.Reg Anesth. 1993; 18: 394-401PubMed Google Scholar A recent prospective study of regional anesthesia in France described 1 patient with cauda equina syndrome after continuous spinal anesthesia with 5% lidocaine.27Auroy 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: 479-486Crossref PubMed Scopus (635) Google Scholar Continuous spinal anesthesia was not the focus of this study, and its use compared to single-injection spinal anesthesia was not specified. However, by conservatively estimating that 5% of the total spinal anesthetics were continuous26Horlocker TT McGregor DG Matsushige DK Chantigian RC Schroeder DR Besse JA Perioperative Outcomes Group Neurologic complications of 603 consecutive continuous spinal anesthetics using macrocatheter and microcatheter techniques.Anesth Analg. 1997; 84: 1063-1070PubMed Google Scholar, 38Bouaziz H Mercier FJ Narchi P Poupard M Auroy Y Ben-hamou D Survey of regional anestheiic practice among French residents at time of certification.Reg Anesth. 1997; 22: 218-222Crossref PubMed Google Scholar, 39Horlocker TT McGregor DG Matsushige DK Schroeder DR Bcsse JA Perioperative Outcomes Group A retrospective review of 4767 consecutive spinal anesthetics: central nervous system complications.Anesth Analg. 1997; 84: 578-584PubMed Google Scholar and that 26.6% used lidocaine,13Drasner K Lidocaine spinal anesthesia: a vanishing therapeutic index? [editorial].Anesthesiology. 1997; 87: 469-472Crossref PubMed Scopus (62) Google Scholar the incidence of cauda equina syndrome is 19 in 10,000 continuous lidocaine spinal anesthetics. The most complete large-scale study of neurologic complications after continuous spinal anesthesia with lidocaine involved 603 consecutive patients in whom both macrocatheter and microcatheter techniques were used.26Horlocker TT McGregor DG Matsushige DK Chantigian RC Schroeder DR Besse JA Perioperative Outcomes Group Neurologic complications of 603 consecutive continuous spinal anesthetics using macrocatheter and microcatheter techniques.Anesth Analg. 1997; 84: 1063-1070PubMed Google Scholar There was 1 cauda equina syndrome of 161 lidocaine anesthetics vs none of 402 bupivacaine, 83 tetracaine, and 5 procaine anesthetics (a few patients received more than 1 LA through a catheter). The patient who developed the cauda equina syndrome had a 20-gauge macrocatheter and had received only clinically appropriate doses of 5% lidocaine-30 mg initially, 45 mg 60 minutes later, and 50 mg 10 minutes after that. An incidence of 1 cauda equina syndrome in 161 continuous lidocaine spinal anesthetics is far higher than the baseline risk of 1 in 10,000 for all spinal anesthetics4Kane RE Neurologic deficits following epidural or spinal anesthesia.Anesth Analg. 1981; 60: 150-161Crossref PubMed Google Scholar, 7Phillips OC Ebner H Nelson AT Black MH Neurologic com
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