title: Time course of the soleus M response and H reflex after lidocaine tibial nerve block in the rat.
abstract: OBJECTIVE
  In spastic subjects, lidocaine is often used to induce a block predictive of the result provided by subsequent surgery. Lidocaine has been demonstrated to inhibit the Hoffmann (H) reflex to a greater extent than the direct motor (M) response induced by electrical stimulation, but the timecourse of these responses has not been investigated.
  
  
  METHODS
  An animal (rat) model of the effects of lidocaine on M and H responses was therefore developed to assess this time course. M and H responses were recorded in 18 adult rats before and after application of lidocaine to the sciatic nerve.
  
  
  RESULTS
  Two to five minutes after lidocaine injection, M responses were markedly reduced (mean reduction of 44%) and H reflexes were completely abolished. Changes were observed more rapidly for the H reflex. The effects of lidocaine then persisted for 100 minutes. The effect of lidocaine was therefore more prolonged on the H reflex than on the M response.
  
  
  CONCLUSIONS
  This study confirms that lidocaine blocks not only alpha motoneurons but also Ia afferent fibres responsible for the H reflex. The authors describe, for the first time, the detailed time course of the effect of lidocaine on direct or reflex activation of motoneurons in the rat.
authors.affiliation: CNRS UMR 7338 Biomécanique et Bioingénierie, Université de Technologie de Compiègne, BP 20529, 60205 Compiègne, France. kevin.buffenoirbillet@chu-nantes.fr
authors.forename: Kévin
authors.initials: K
authors.lastname: Buffenoir
authors.forename: Philippe
authors.initials: P
authors.lastname: Decq
authors.forename: Chantal
authors.initials: C
authors.lastname: Pérot
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage*; D000818:Animals; D008012:Lidocaine / Q000008:administration & dosage*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013977:Tibia / Q000294:innervation*
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine