Improved regional anesthesia techniques and less toxic local anesthetics (LA) appear to be associated with a declining number of reported episodes of severe LA toxicity over the past quarter century. The current incidence of clinically important LA toxicity in adults may be subject to under-reporting, but estimates range from 7.5 to 20 per 10,000 peripheral nerve blocks (PNBs) and about 4 per 10,000 epidurals (1). Before the reports of cardiac arrest from labor epidurals with 0.75% bupivacaine and etidocaine (2) and the “black box” warning in the package insert (for the United States) of bupivacaine in 1983 (3), the rate of LA systemic toxicity with epidurals ranged from 20 to 320 per 10,000 (4–7). Although rare, LA toxicity may be lethal, and clinicians should formulate provisions for a rapid and educated response to such events. Unfortunately, despite more than 20 yr of animal research and case reports of potentially effective treatments, there appears to be no consensus for optimum management of catastrophic LA toxicity.
The primary aim of this survey was to determine how U.S. academic anesthesiology departments prepare for and treat LA cardiotoxic events, and secondarily, to assess variation in practice patterns in PNB performance. We hypothesized that we would encounter a wide range of practice patterns and preparation for treatment of toxicity, and that departments where larger numbers of PNBs are performed would have responses more in line with current literature.
The 19-question survey with return envelope was mailed to the chairs of the 135 academic anesthesiology departments listed by the Society of Academic Anesthesiology Chairs-Association of Anesthesiology Program Directors. Questions were designed to identify preferred LAs and typical dosage, monitoring during PNB, level of training of those performing PNBs, location where PNBs were performed, volume of PNBs performed, and choice of pharmacologic resuscitation used in the event of a cardiac complication (Fig. 1). We also asked whether lipid emulsion infusions and/or mechanical cardiopulmonary support would be used if initial attempts at pharmacologic resuscitation failed. We asked that the department chair, the director of regional anesthesia, or the director of acute pain management complete the survey. No follow-up survey was sent to nonresponders.
Institutions were categorized by the number of PNBs performed per month, and we arbitrarily defined high-volume centers as those performing >70 per month, and low-volume as ≤70 month. Responses were analyzed relative to the number of procedures performed in a responder’s medical setting using χ2. Care was taken to artificially dichotomize the procedure volume categories so that >5 responses were expected in each cell. Odds ratios with 95% confidence intervals (CI) were used to index the effect size of the observed differences. The α-value was set at 0.05. All analyses were conducted using SPSS 13.0 (SPSS, Chicago, IL).
Survey Response and PNB Volume
Sixty-seven percent of surveys were completed and returned. The distribution of the number of PNBs performed monthly was: >70 PNBs (38%), 51–70 PNBs (13%), 31–50 PNBs (20%), 11–30 PNBs (23%), and <10 PNBs (6%). PNBs were performed by trainees (residents or fellows) 88% of the time. At 9% of the programs, only staff anesthesiologists performed PNBs. The location of block administration and supervision included the preoperative holding area (50%), a dedicated regional anesthesia induction area (30%), and the operating room (24%). Some programs reported that PNBs were performed in multiple locations.
LA Choice and Dosage
A substantial variation was observed in preferred long-acting LAs. Although 19% of respondents selected multiple drugs, the preferred long-acting LA was either bupivacaine (55% of respondents) or ropivacaine (43%) (P = 0.26) (Fig. 2A). Though most centers preferred bupivacaine, there was a slight trend for high-volume institutions to choose ropivacaine, odds ratio = 1.7 (95% CI 0.70–3.9, P = 0.24).
The choice of intermediate-acting LAs reflected similar variability. The two most cited single drugs were mepivacaine (50%) and lidocaine (32%), with a trend for centers to prefer mepivacaine, χ2 = 3.46, P = 0.06 (Fig. 2B).
When performing an infraclavicular or axillary block with bupivacaine, most institutions chose doses of 125–200 mg (71%). Few centers used >200 mg (10%) or <125 mg (19%). High-volume centers were 7.5-times more likely to use >200 mg (95% CI 1.4–40.3, P = 0.02). When performing infraclavicular or axillary blocks with ropivacaine, most institutions chose 125–200 mg (66%).
Monitoring During Block Placement
Standard monitoring during PNB varied among institutions. There was no apparent relationship between monitoring procedures and the number of PNBs performed per month or the level of training of the practitioner performing the block. Standard monitoring consisted of pulse oximetry, noninvasive arterial blood pressure (BP), and electrocardiogram (ECG) for 69% of centers, while 15% used only pulse oximetry and BP, and 16% used only pulse oximetry while performing regional blocks.
Centers stored emergency drugs variously in a “code blue” cart (63%), designated regional anesthesia lock box (26%), or another location (11%) for emergency treatment of LA toxicity. In response to ventricular tachycardia from presumed bupivacaine toxicity, 59% would use amiodarone, while 19% would choose bretylium, 13% esmolol, and 2% would use lidocaine. Low-volume centers, defined as ≤30 PNBs for this analysis only, were 3.6-times (95% CI 1.3–10.3) more likely to choose bretylium for bupivacaine-induced ventricular tachycardia than high-volume centers (40% vs 16%, P = 0.016).
For an episode of hypotension, 87% of respondents would choose ephedrine and/or phenylephrine followed by epinephrine (8%) or vasopressin (3%). For persistent hypotension 71% of programs would choose epinephrine, 20% ephedrine and/or phenylephrine, and 11% vasopressin.
Lipid Emulsion: Choice and Availability
With respect to the potential use of lipid emulsion infusion to treat bupivacaine toxicity, 74% of centers would not use it, and 26% would consider its use. High-volume centers were 3.9-times more likely (95% CI 1.4–10.6) than low-volume centers to use lipid infusion for bupivacaine toxicity (44% vs 17%, P = 0.008) (Fig. 3). Of those considering the use of lipid infusion, storage location was the operating room pharmacy (39%), the hospital pharmacy (35%), the code cart/lock box (22%), or a drug-dispensing machine (4%). It could be obtained in <10 min for 59%, 10–30 min for 26%, and >30 min for 15% of the centers.
Mechanical Circulatory Support
For failed resuscitation, 59% of respondents have no established plan for mechanical cardiopulmonary support, with no difference by PNB volume (Fig. 4). For those with an established plan, most often it included cardiopulmonary bypass (CPB) (89%), intraaortic balloon pump counterpulsation (22%), and extracorporeal membrane oxygenation (14%). Cardiothoracic surgeons could respond in <10 min for 33%, 10–30 min for 51%, and >30 min for 15% of respondents.
Our results show a wide range of current practice patterns for PNB in U.S. academic centers, and variability in nearly all aspects of treatment strategies for managing severe LA toxicity. Much of the observed variability (PNB performance site, monitoring, preferred intermediate-duration LA, resuscitation drugs, and so forth) was independent of PNB volume. Conversely, the finding that high-PNB volume centers showed a trend to favor ropivacaine, and to be significantly more likely to consider lipid emulsion infusion and less likely to list bretylium as a treatment for severe LA toxicity than low-volume centers (≤30 PNBs) merits closer examination. It is possible that process variation could lead to poorer outcome from relatively rare, but catastrophic, toxic reactions (8).
The findings of Aberg (9) and Akerman et al. (10), that S-bupivacaine requires larger doses than R-bupivacaine to produce convulsions and mortality, led to the development of levobupivacaine and its S-enantiomer homologue ropivacaine (11,12). Subsequent animal studies have demonstrated differences in mortality or inability to resuscitate between racemic bupivacaine-treated dogs (50% mortality) and ropivacaine-treated dogs (10% mortality) after anesthetized dogs received continuous, escalating infusions of LA. (13) Still, severe toxicity in patients has been reported with ropivacaine (14–17), but ropivacaine toxicity may be more amenable to treatment than reactions to bupivacaine, and no ropivacaine-induced deaths have been reported.
Despite the apparent increased safety margin with ropivacaine, our study demonstrates that bupivacaine is widely, and even exclusively, used in many institutions. Factors other than safety during rare toxic events, such as acquisition cost and perceived quality or duration of PNB, may influence LA choice, but these factors were not evaluated in our survey.
Monitoring During PNB
BP, three-lead ECG, and pulse-oximetry are among the standard monitors endorsed by the American Society of Anesthesiologists for use during all anesthetics (www.asahq.org/publicationsAndServices/standards/02.pdf), but only 69% of respondents used all three monitors during PNB. Although the American Society of Anesthesiologists Standards acknowledge that practitioners may circumvent standard monitoring when indicated (and documented), both BP and ECG monitoring may supplement pulse oximetry to demonstrate early signs of LA toxicity (18). Specifically, the ECG is necessary to characterize arrhythmias should severe toxicity occur.
Treatment Strategies for LA Toxicity
There is no consensus strategy for how best to treat severe LA toxicity. Indeed, there is no ethical way to conduct meaningful clinical trials in this area. Our survey showed, however, that high-PNB volume institutions are more likely to choose amiodarone (as opposed to lidocaine or bretylium) for ventricular tachycardia. The stated preference of some centers for bretylium is particularly alarming, since this drug is no longer available in North America or included in Advanced Cardiac Life Support Guidelines.
Lipid Emulsion Infusion and Mechanical Circulatory Support for Severe LA Toxicity
We presumed that all centers would institute ventilatory support and chest compression per Advanced Cardiac Life Support Guidelines for complete cardiopulmonary collapse after PNB, and we did not include survey questions for those interventions. Lipid emulsion infusion may be a consideration after institution of cardiopulmonary resuscitation in such severe toxic events. Animal studies by Weinberg and co-workers (19–21) have shown lipid emulsion infusions to be effective as a means of resuscitation from bupivacaine toxicity after chest compression (rat) or cardiac massage (dog) failed to resuscitate the animals. The mechanism of lipid resuscitation remains under investigation, but may be due to the migration of amphiphilic LA molecules from binding sites in the heart into the plasma-born lipid. Dog studies show that after circulatory collapse secondary to bupivacaine toxicity, lipid treatment increased the survival rate from 0% in the control group to 100% in the lipid-treated group (19). Enthusiasm for lipid treatment must be tempered by the absence of published reports of successful use of lipid to resuscitate humans with LA toxicity. Results of this survey show that the high-volume centers are significantly more receptive to the use of lipid emulsion for refractory LA cardiotoxicity than the low-volume centers. One case report documents the successful use of lipid for bupivacaine cardiac toxicity (22).
CPB has resulted in survival in human cases of bupivacaine cardiovascular toxicity. Bupivacaine may have a prolonged duration of action in cases of cardiovascular collapse; thus, patients may require cardiopulmonary support for >45 min (23–25). In the event of failed pharmacologic resuscitation, our results show that only 41% of centers have a plan for mechanical cardiopulmonary support (Fig. 4). Most institutions report that cardiothoracic surgeons could arrive in 30 min or less, although the most important variable, time from identification of the need until onset of bypass, was not ascertained. There are no documented reports of the successful use of extracorporeal membrane oxygenation for LA toxicity; nevertheless, if available, it may be instituted more rapidly than CPB.
This study has a number of limitations. The inability to show differences between high and low-volume centers can indicate that differences were not present or that there was simply a lack of statistical power to detect them. Although a response rate of 67% is good, our findings should be interpreted cautiously because of limited statistical power, which enabled us to detect only moderate to large effect sizes in the differences between categories (26). In addition, only academic anesthesiology departments were surveyed, and the results may not reflect the much broader practice of regional anesthesia in non-academic departments. Furthermore, there may be a range of practice within responding departments not reflected by the survey, and an assumption was made that a department chair would provide the same responses as the director of regional anesthesia in a given institution, which may not be accurate. This limitation, however, would most likely lead to our survey results under-estimating the variability in PNB practice and preparedness for LA toxicity.
Our finding of wide variability in preparedness for LA toxicity and lack of consensus for treatment is noteworthy. Lessons learned from malignant hyperthermia show that well-established treatment guidelines could allow for early intervention to effectively save lives (27). LA cardiac toxicity is likely at least as common as malignant hyperthermia, and potentially as frequently fatal. Our survey results support efforts to determine and disseminate optimal treatment strategies for severe LA toxicity.
1. Mulroy MF. Systemic toxicity and cardiotoxicity from local anesthetics: incidence and preventive measures. Reg Anesth Pain Med 2002;27:556–61.
2. Albright GA. Cardiac arrest following regional anesthesia with etidocaine or bupivacaine. Anesthesiology 1979;51:285–7.
3. Horlocker TT, Wedel DJ. Local anesthetic toxicity—does product labeling reflect actual risk? Reg Anesth Pain Med 2002;27:562–7.
4. Blundell AE, Bodell B, Andorko JE, et al. Clinical evaluation of drugs used in obtaining lumbar epidural anesthesia. Anesthesiology 1955;16:386–93.
5. Bonica JJ, Backup PH, Anderson CE, et al. Peridural block: analysis of 3,637 cases and a review. Anesthesiology 1957;18:723–84.
6. Moore DC. Toxic effects of local anesthetics. JAMA 1978;240:434.
7. Kenepp NB, Gutsche BB. Inadvertent intravascular injections during lumbar epidural anesthesia. Anesthesiology 1981;54:172–3.
8. Shewhart WA. Statistical methods from the viewpoint of quality control. Mineola, NY: Dover, 1986.
9. Aberg G. Toxicological and local anaesthetic effects of optically active isomers of two local anaesthetic compounds. Acta Pharmacol Toxicol (Copenh) 1972;31:273–86.
10. Akerman B, Hellberg IB, Trossvik C. Primary evaluation of the local anaesthetic properties of the amino amide agent ropivacaine (LEA 103). Acta Anaesthesiol Scand 1988;32:571–8.
11. Mather LE, Chang DH. Cardiotoxicity with modern local anaesthetics: is there a safer choice? Drugs 2001;61:333–42.
12. Groban L. Central nervous system and cardiac effects from long-acting amide local anesthetic toxicity in the intact animal model. Reg Anesth Pain Med 2003;28:3–11.
13. Groban L, Deal DD, Vernon JC, et al. Cardiac resuscitation after incremental overdosage with lidocaine, bupivacaine, levobupivacaine, and ropivacaine in anesthetized dogs. Anesth Analg 2001;92:37–43.
14. Chazalon P, Tourtier JP, Villevielle T, et al. Ropivacaine-induced cardiac arrest after peripheral nerve block: successful resuscitation. Anesthesiology 2003;99:1449–51.
15. Huet O, Eyrolle LJ, Mazoit JX, Ozier YM. Cardiac arrest after injection of ropivacaine for posterior lumbar plexus blockade. Anesthesiology 2003;99:1451–3.
16. Klein SM, Pierce T, Rubin Y, et al. Successful resuscitation after ropivacaine-induced ventricular fibrillation. Anesth Analg 2003;97:901–3.
17. Polley LS, Santos AC. Cardiac arrest following regional anesthesia with ropivacaine: here we go again. Anesthesiology 2003;99:1253–4.
18. Takahashi S, Tanaka M, Toyooka H. The efficacy of hemodynamic and T-wave criteria for detecting intravascular injection of epinephrine test dose in propofol-anesthetized adults. Anesth Analg 2002;94:717–22.
19. Weinberg GL. Current concepts in resuscitation of patients with local anesthetic cardiac toxicity. Reg Anesth Pain Med 2002;27:568–75.
20. Weinberg G, Ripper R, Feinstein DL, Hoffman W. Lipid emulsion infusion rescues dogs from bupivacaine-induced cardiac toxicity. Reg Anesth Pain Med 2003;28:198–202.
21. 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;88:1071–5.
22. Rosenblatt MA, Abel M, Fischer GW, et al. Successful use of a 20% lipid emulsion to resuscitate a patient after a presumed bupivacaine-related cardiac arrest. Anesthesiology 2006;105:217–8.
23. Soltesz EG, van Pelt F, Byrne JG. Emergent cardiopulmonary bypass for bupivacaine cardiotoxicity. J Cardiothorac Vasc Anesth 2003;17:357–8.
24. Tsai MH, Tseng CK, Wong KC. Successful resuscitation of a bupivacaine-induced cardiac arrest using cardiopulmonary bypass and mitral valve replacement. J Cardiothorac Anesth 1987;1:454–6.
25. Long WB, Rosenblum S, Grady IP. Successful resuscitation of bupivacaine-induced cardiac arrest using cardiopulmonary bypass. Anesth Analg 1989;69:403–6.
26. Cohen JC. Statistical power analysis for the behavioral sciences, 2nd ed. Hillsdale, NJ: Lawrence Erlbaum Associates, 1988.
27. Halliday NJ. Malignant hyperthermia. J Craniofac Surg 2003;14:800–2.