Anesth Analg 2004;99:1875-1876
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000138550.57760.22
LETTERS TO THE EDITOR
Lipid, Not Propofol, Treats Bupivacaine Overdose
Guy Weinberg, MD,
Paul Hertz, MD, and
Janet Newman, MD
Department of Anesthesiology, University of Illinois, Chicago, IL, guyw@uic.edu
To the Editor:
Mayr et al. (1) recently reported the comparative efficacies of epinephrine, vasopressin, and a combination of the two drugs in a porcine model of bupivacaine overdose. They used a single 5 mg/kg IV bolus of bupivacaine, applied advanced cardiac life support 1 min after asystole, and administered drugs 2 min later and at 5-min intervals thereafter. Monophasic countershocks were applied as dictated by rhythm disturbance. Rates of survival were 5/7 for vasopressin, 4/7 for epinephrine, 7/7 in the combined treatment group, and 0/7 in controls.
By comparison, we reported that injecting a 20% lipid emulsion in combination with cardiac massage leads to successful return of normal hemodynamics in 9/9 dogs after a bolus injection of 10 mg/kg bupivacaine (2). Lipid infusion in 6 of these dogs was delayed for 10 min to approximate a clinical scenario. A normal rhythm was established in all 9 dogs within 5 min; no electrical counter shock was required. No control animal demonstrated return of BP or HR.
Dogs and pigs may differ in terms of susceptibility to bupivacaine cardiac toxicity; the porcine and canine models may not be completely comparable for this and other reasons. However, we and others (3) believe the rapid return of normal rhythm and hemodynamics in both dogs and rats following massive bupivacaine overdose (twice the dose used in Mayr’s study), indicates superior efficacy of lipid rescue for bupivacaine toxicity to drugs, such as epinephrine and vasopressin that are components of the generic ACLS protocol for cardiopulmonary arrest (4). Perhaps Dr. Mayr will consider comparing combined epinephrine/vasopressin with lipid rescue in the porcine model of bupivacaine cardiac toxicity.
Mayr et al. (1) also incorrectly cite us as indicating that "....a lipid infusion such as propofol increases the dose of bupivacaine required to induce cardiac arrest, and, therefore, this strategy has been suggested as a potential means to improve outcomes from such toxicity." We have never recommended use of propofol for treating bupivacaine overdose, and strongly suspect that its use in cardiac arrest will impede resuscitation.
We have recommended treating bupivacaine-associated cardiac arrest by injecting a 1 mL/kg bolus of 20% lipid emulsion (such as Intralipid) and starting an infusion of 0.25 mL/kg/min for 10 min, while continuing basic life support (5). The bolus could be repeated every 5 min, two or three times if needed. The upper dose limit of 20% lipid emulsion is not known, but a total of more than 8 mL/kg is not likely to be needed, nor successful if lower doses are not. Note that this protocol will deliver a significant volume load (several hundred mL in an adult). The standard formulation of propofol is 10% lipid and 1% propofol. Therefore, gram quantities of propofol would accompany our recommended regimen and only half the dose of lipid, the necessary ingredient, would be delivered.
Propofol is not an acceptable treatment for bupivacaine overdose.
References
- Mayr VD, Raedler C, Wenzel V, et al. A comparison of epinephrine and vasopressin in a porcine model of cardiac arrest after rapid intravenous injection of bupivacaine. Anesth Analg 2004; 98: 1426–31.[Abstract/Free Full Text]
- 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.[Web of Science][Medline]
- Groban L, Butterworth J. Lipid reversal of bupivacaine toxicity: has the silver bullet been identified? Reg Anesth Pain Med 2003; 28: 167–9.[Web of Science][Medline]
- Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Part 8: advanced challenges in resuscitation: section 2: toxicology in ECC. The American Heart Association in collaboration with the International Liaison Committee on Resuscitation. Circulation 2000; 102 (suppl 8): I223–8.[Medline]
- Weinberg G. Lipid rescue: caveats and recommendations for the "Silver Bullet" [letter]. Reg Anesth Pain Med 2004; 29: 74–5.
Response
Viktoria D. Mayr, MD,
Claus Raedler, MD,
Volker Wenzel, MD,
Karl H. Lindner, MD, and
Hans-Ulrich Strohmenger, MD
Univ. Klinik f. Anaesthesie u. Allg. Intensivmedezin, Innsbruck, Austria, Viktoria.Mayr@uibk.ac.at
In Response:
We would like to thank Weinberg et al. for their interest in our work, as well as for their constructive comments. First, we sincerely apologize for having incorrectly cited Weinberg et al. by confounding propofol and intralipid; we completely agree with their statement that propofol administration cannot be recommended for managing a bupivacaine overdose. When indicating in the Discussion section that "... a lipid infusion such as propofol increases the dose of bupivacaine required to induce cardiac arrest, and therefore, this strategy has been suggested as a potential means to improve outcomes from such toxicity," we did not suggest to use propofol for treating bupivacaine toxicity, nor that Dr. Weinberg et al. used propofol for treating bupivacaine toxicity. We share the same opinion that usage of propofol in cardiac arrest may impede resuscitation. With our statement about a "lipid infusion such as propofol...", we only wanted to state the reason why we did not use propofol but isoflurane and nitrous oxide to maintain anesthesia in our experiment. Instead of saying "... a lipid infusion such as propofol...", it would have been better to state "... as propofol is a lipid infusion which may increase the dose of bupivacaine required to induce cardiac arrest..." Second, beneficial lipid effects during massive bupivacaine overdose as described by Weinberg et al. resulted in impressive outcome data. However, their conclusion drawn in the letter that these results indicate the superiority of this treatment regime in comparison to advanced cardiac life support including epinephrine and vasopressin has not been proven. The comparative investigation of the epinephrine/vasopressin combination and the lipid rescue protocol in the same animal model of bupivacaine cardiac toxicity can only provide reliable information in this respect.
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