title: A description of the spread of injectate after psoas compartment block using magnetic resonance imaging.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) provides for excellent visualization of spread of solution after peripheral nerve block. The aim of this observational study was to utilize MRI to describe the distribution of injectate (gadopentetate dimeglumine) administered for continuous psoas compartment block (PCB) performed by use of two approaches (Capdevila and modified Winnie) and to describe the spread of injectate to the lumbar plexus.
  
  
  METHODS
  Four volunteers were enrolled in a prospective crossover study. Each volunteer underwent PCB with catheter placement performed by use of Capdevila's approach followed 1 week later by PCB, with catheter placement performed by use of a modified Winnie approach. MRI of injectate distribution was performed after each PCB.
  
  
  RESULTS
  The catheter was unable to be inserted in 1 volunteer undergoing Winnie's approach; therefore, 7 sets of MR images were analyzed. In 6 of 7 cases (4 Capdevila and 2 Winnie) spread was primarily within the psoas muscle. Contrast surrounded the L2-3 lumbar branch of the femoral nerve at L4 and cleaved the fascial plane within the psoas muscle and spread cephalad to reach the lumbar nerve roots. In 1 case (Winnie approach) contrast spread between the psoas and quadratus lumborum muscles. Contrast surrounded the femoral and obturator nerves where they lie outside the psoas muscle at L5.
  
  
  CONCLUSIONS
  The most common pattern of injectate spread seen on MRI with both approaches to PCB was spread within the body of the psoas muscle around the lumbar branches (L2-4), with cephalad spread to the lumbar nerve roots. One catheter resulted in injectate between the psoas and quadratus lumborum muscles.
authors.affiliation: Department of Anaesthesia and Intensive Care, Cork University Hospital & University College, Cork, Ireland. mannionstephen@hotmail.com
authors.forename: Stephen
authors.initials: S
authors.lastname: Mannion
authors.forename: Jack
authors.initials: J
authors.lastname: Barrett
authors.forename: Denis
authors.initials: D
authors.lastname: Kelly
authors.forename: Damian B
authors.initials: DB
authors.lastname: Murphy
authors.forename: George D
authors.initials: GD
authors.lastname: Shorten
mesh_terms: D000328:Adult; D003287:Contrast Media / Q000008:administration & dosage*; D018592:Cross-Over Studies; D019786:Gadolinium DTPA / Q000008:administration & dosage*; D006801:Humans; D008160:Lumbosacral Plexus / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009407:Nerve Block / Q000379:methods*; D011446:Prospective Studies; D016658:Psoas Muscles / Q000294:innervation / Q000473:pathology
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA