title: Differential epidural block.
abstract: OBJECTIVE
  Loss of sensation to pinprick and cold are commonly used to test the extent of epidural anesthesia. To see what difference exists between the level of epidural block determined by various sensory modalities, we performed this study in ten volunteers using epidural anesthesia with plain 3% chloroprocaine hydrochloride.
  
  
  METHODS
  Four injections of chloroprocaine were made via an epidural catheter inserted at L2-3 with increasing larger volumes. Sensory modalities tested were (1) absence of sensation when tested by pinprick (anesthesia), (2) loss of a sharp sensation compared to an unblocked dermatome when tested by pinprick (analgesia), and (3) loss of cold sensation when tested with an alcohol swab compared to an unblocked dermatome.
  
  
  RESULTS
  At 20 minutes after each injection the level of anesthesia was found to be most caudad and the level of analgesia most cephalad. The zone of differential block was greater than four dermatomes at the highest level of block tested. The level of loss of cold sensation was found between the other two levels. Differences between the levels of analgesia and cold sensation tended to be greater with more extensive block. Differences between levels of anesthesia and cold sensation did not significantly change as the extent of epidural anesthesia was increased.
  
  
  CONCLUSIONS
  This study establishes the existence of a differential epidural anesthesia during high thoracic block with chloroprocaine and suggests that the intensity of block diminishes as distance from site of injection increases.
authors.affiliation: Department of Anesthesiology, National Naval Medical Center, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
authors.forename: R A
authors.initials: RA
authors.lastname: Stevens
authors.forename: J G
authors.initials: JG
authors.lastname: Bray
authors.forename: J D
authors.initials: JD
authors.lastname: Artuso
authors.forename: T C
authors.initials: TC
authors.lastname: Kao
authors.forename: L
authors.initials: L
authors.lastname: Spitzer
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local; D003080:Cold Temperature; D005260:Female; D006801:Humans; D008297:Male; D010146:Pain; D011343:Procaine / Q000031:analogs & derivatives*; D012677:Sensation
chemical_list: D000779:Anesthetics, Local; D011343:Procaine; C004616:chloroprocaine