Welcome to the MedLibrary.org Wikipedia Supplement on Local anesthetic toxicity -- Please Click to Return to Front Page

While generally safe, local anesthetic agents can be toxic if used in excessive doses or administered improperly. Even when administered properly, patients may still experience unintended reactions to local anesthetics.^[1]

Excessive doses may be unintentionally administered in several ways.

1. Repetitive (small) doses of local anesthetic to achieve an adequate level of anesthesia may lead to eventual adminitration of toxic doses.
2. Injection of anesthesia in a confined space may result in excesive fluid pressure that may damage nerves.
3. Doses intended for epidural or intra-support-tissue administration may be accidentally delivered as intravascular injection resulting in accelerated systematic absorption.^[2]

The toxic effects of local anesthetics can be classified by localized and systemic effects.

Contents 1 Localized toxicity 2 Systemic toxicity 2.1 Immune system effects 2.2 Hematologic effects 2.3 Cardiovascular effects 3 See also 4 References

Localized toxicity

A cause of local toxicity is allergic reaction to para-aminobenzoic acid (PABA). These reactions range from urticaria to anaphylaxis.

PABA is a metabolic product of the degradation of Ester class of local anesthetics, such as Procaine (Novocaine), Benzocaine, and, to a lesser degree, amide class anesthetics such asLidocaine, and Prilocaine. It is also a metabolic by-product of Methylparaben, a preservative in multi-dose vials of Lidocane. When allergic response to injected anesthetics does occur, it is most likely due to the ester class local anesthetics. The amide class of local anesthetics is far less likely to produce allergic reaction.^[3].^[4]

Systemic toxicity

Systemic toxicity of anesthetics involves the central nervous system (CNS), the cardiovascular system, and the immune system.

It can be described by the direct effects on the immune system, blood (hematologic), and cardiovascular system.

Immune system effects

As noted previously, allergic reaction to metabolic break-down of anesthetic agents and preservatives (PABA) can cause anaphylaxis.

Hematologic effects

Methemoglobinemia is a process where iron in hemoglobin is altered, reducing its oxygen-carrying capability, which produces cyanosis and symptoms of hypoxia. Benzocaine, Lidocaine, and Prilocaine all produce this effect, especially Benzocaine.^[5]

Cardiovascular effects

Cardiovascular effects are primarily those of direct myocardial depression and bradycardia, which may lead to cardiovascular collapse.^[6].

Systemic toxic reactions to locally administered anesthetics are progressive as the level of the anesthetic agent in the blood rises. Initial symptoms suggest some form of central nervous system excitation such as a ringing in the ears (tinnitus), a metallic taste in the mouth, or tingling or numbness of the mouth. advanced symptoms include motor twitching in the periphery followed by grand mal seizures, coma, and eventually respiratory arrest. At extremely high levels, cardiac arrhythmia or hypotension and cardiovascular collapse occur.^[7]

See also

• Local anesthetic

References

1. ^ Zamanian, R., Toxicity, Local Anesthetics (2005)
2. ^ Zamanian, R., Toxicity, Local Anesthetics (2005)
3. ^ Dolan, R., ed. (2004), Facial Plastic, Reconstruction, and Trauma Surgery
4. ^ Univ. of Wisconsin, Local Anesthesia and Regional Anesthetics
5. ^ Dolan, R., ed. (2004), Facial Plastic, Reconstruction, and Trauma Surgery
6. ^ Zamanian, R., Toxicity, Local Anesthetics (2005)
7. ^ Mulroy, M., Systemic Toxicity and Cardiotoxicity From Local Anesthetics (2002)

|Zamanian, Roham T. (June 20, 2005), Toxicity, Local Anesthetics, eMedicine by WebMD, <http://www.emedicine.com/emerg/topic761.htm>. Retrieved on 10 October 2007 

Local Anesthesia and Regional Anesthetics, University of Wisconsin at Madison, <http://www.anesthesia.wisc.edu/med3/localanes/localhandout.html>. Retrieved on 10 October 2007 

Drasner, Kenneth (2002), "Local Anesthetic Neurotoxicity: Clinical Injury and Strategies That May Minimize Risk", Regional Anesthesia and Pain Medicine (American Society of Regional Anesthesia and Pain Medicine) Vol 27(No 6 (November–December)): pp 576–580, <http://asra.com/consensus-statements/Drasner.pdf>. Retrieved on 10 October 2007 

"Nerve damage associated with peripheral nerve block", Risks associated with your anaesthetic, (The Royal College of Anaesthetists) Section 12, January 2006, <http://www.rcoa.ac.uk/docs/nerve-peripheral.pdf>. Retrieved on 10 October 2007 

Mulroy, Michael F. (2002), "Systemic Toxicity and Cardiotoxicity From Local Anesthetics: Incidence and Preventive Measures", Regional Anesthesia and Pain Medicine (Department of Anesthesiology, VirginiaMason Medical Center, Seattle, Washington) Vol. 27(No 6 (November–December)): pp 556–561, <http://asra.com/consensus-statements/Mulroy.pdf>. Retrieved on 10 October 2007 

Dolan, Robert W., ed. (2004), Facial Plastic, Reconstruction, and Trauma Surgery, Informa Health Care, pp. pp 30-31, ISBN 0-8247-4595-7, <http://books.google.com/books?id=uBB_vaBNyXIC&pg=PA30&lpg=PA30&dq=paba+provokes+allergic+reaction&source=web&ots=gKHqScNptQ&sig=RdrkgUF4V0gpCgim8leFoE8TWtk#PPA30,M1>. Retrieved on 10 October 2007 

Wikipedia content modification information:

• This page was last modified on 5 May 2008, at 13:48.

Wikipedia Authorship and Review

Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.

Wikipedia Usage Guidelines

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Local anesthetic toxicity".

The URL for this specific entry is:

• http://medlibrary.org/medwiki/Local_anesthetic_toxicity

All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.