title: Lumbar plexus block using high-pressure injection leads to contralateral and epidural spread.
abstract: BACKGROUND
  The main advantage of lumbar plexus block over neuraxial anesthesia is unilateral blockade; however, the relatively common occurrence of bilateral spread (up to 27%) makes this advantage unpredictable. The authors hypothesized that high injection pressures during lumbar plexus block carry a higher risk of bilateral or neuraxial anesthesia.
  
  
  METHODS
  Eighty patients undergoing knee arthroscopy (age 18-65 yr; American Society of Anesthesiologists physical status I or II) during a standard, nerve stimulator-guided lumbar plexus block using 35 ml mepivacaine, 1.5%, were scheduled to be studied. Patients were randomly assigned to receive either a low-pressure (< 15 psi) or a high-pressure (> 20 psi) injection, as assessed by an inline injection pressure monitor (BSmart; Concert Medical LLC, Norwell, MA). The block success rate and the presence of bilateral sensory and/or motor blockade were assessed.
  
  
  RESULTS
  An interim analysis was performed at n = 20 after an unexpectedly high number of patients had neuraxial spread, necessitating early termination of the study. Five of 10 patients (50%) in the high-pressure group had a neuraxial block with a dermatomal sensory level T10 or higher. In contrast, no patient in the low-pressure group (n = 10) had evidence of neuraxial spread. Moreover, 6 patients (60%) in the high-pressure group demonstrated bilateral sensory blockade in the femoral distribution, whereas no patient in the low-pressure group had evidence of a bilateral femoral block.
  
  
  CONCLUSIONS
  Injection of local anesthetic with high injection pressure (> 20 psi) during lumbar plexus block commonly results in unwanted bilateral blockade and is associated with high risk of neuraxial blockade.
authors.affiliation: Columbia University College of Physicians and Surgeons, New York, New York, USA. jeffgadsden@gmail.com
authors.forename: Jeff C
authors.initials: JC
authors.lastname: Gadsden
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Lindenmuth
authors.forename: Admir
authors.initials: A
authors.lastname: Hadzic
authors.forename: Daquan
authors.initials: D
authors.lastname: Xu
authors.forename: Lakshmanasamy
authors.initials: L
authors.lastname: Somasundarum
authors.forename: Kamil A
authors.initials: KA
authors.lastname: Flisinski
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae; D008297:Male; D008619:Mepivacaine / Q000008:administration & dosage / Q000493:pharmacokinetics; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D011312:Pressure
chemical_list: D008619:Mepivacaine