Epidural during labor causes fever , temperature goes up. Mechanism was not found yet. We found possible mechanism on Wikipedia. God bless Wikipedia.
Another problem—local anesthetics burn on injection(when you go to your dentist–it burns when he shoots you).Why? Feeling of burning is mediated thru vanilloid receptor(TRPV1) .Anything that burns has to work thru vanilloid receptor (pepper , garlic, mace, acid). Menthol blocks it.Besides pain this receptor is is excited by high temperature too—thats why cooling bruise with ice will reduce pain—its the same receptor.
http://en.wikipedia.org/wiki/Vanilloid_receptor
TRPV1 is the most popular, pepper works thru that
http://en.wikipedia.org/wiki/TRPV1
so Lidocaine when injected works on this receptor, stimulates it and causes pain (and blocks it after.
antagonist of this receptor are proved to cause hyperthermia:(same wikipedia page)
Antagonists block TRPV1 activity, thus reducing pain. These agents could be useful when applied systemically.[8] Numerous TRPV1 antagonists have been developed by pharmaceutical companies. TRPV1 antagonists have shown efficacy in reducing nociception from inflammatory andneuropathic pain models in rats.[9] This provides evidence that TRPV1 is the capsaicin‘s sole receptor.[10] In humans, drugs acting at TRPV1 receptors could be used to treat neuropathic pain associated with multiple sclerosis, chemotherapy, or amputation, as well as pain associated with the inflammatory response of damaged tissue, such as in osteoarthritis.[11]
The major roadblock for the usefulness of these drugs is their effect on body temperature (hyperthermia). The role of TRPV1 in the regulation of body temperature has emerged in the last few years. Based on a number of TRPV-selective antagonists‘ causing an increase in body temperature (hyperthermia), it was proposed that TRPV1 is tonically active in vivo and regulates body temperature[12] by telling the body to “cool itself down”. Without these signals, the body overheats. Similarly, this explains the propensity of capsaicin (a TRPV1 agonist) to cause sweating (i.e.: a signal to reduce body temperature). In a recent report, it was found that tonically active TRPV1 channels are present in the viscera and keep an ongoing suppressive effect on body temperature.[13] Recently, it was proposed that predominant function of TRPV1 is body temperature maintenance [14]Experiments have shown that TRPV1 blockade increases body temperature in multiple species, including rodents and humans, suggesting that TRPV1 is involved in body temperature maintenance.[12] Recently, AMG 517, a highly selective TRPV1 antagonist was dropped out of clinical trials due to the undesirable level of hyperthermia.[15]
soooo—local anesthetics (bupivacaine) in epidural will block this receptor and will cause fever. So cool.And lidocaine on injection will stimulate this receptor and will cause burning.
couple of articles :Lidocaine and TRPV1
2 plus 2 equal 4 —-Lidocaine burning and hypertermia during labor epidural—same cause
there a couple of articles on this topic:
The vanilloid receptor TRPV1 is activated and sensitized by local anesthetics in rodent sensory neurons
Andreas Leffler1, Michael J. Fischer2, Dietlinde Rehner1, Stephanie Kienel1, Katrin Kistner2, Susanne K. Sauer2, Narender R. Gavva3, Peter W. Reeh2 and Carla Nau1
1Department of Anesthesiology and
2Department of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany.
3Department of Neuroscience, Amgen Inc., Thousand Oaks, California, USA.
Address correspondence to
Coapplication of lidocaine and the permanently charged sodium channel blocker QX-314 produces a long-lasting nociceptive blockade in rodents.
Binshtok AM, Gerner P, Oh SB, Puopolo M, Suzuki S, Roberson DP, Herbert T, Wang CF, Kim D, Chung G, Mitani AA, Wang GK, Bean BP, Woolf CJ.
Source
Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Cochrane Database Syst Rev. 2004 Oct 18;(4):CD004457.
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