title: Adding a selective obturator nerve block to the parasacral sciatic nerve block: an evaluation.
abstract: Our aim was to objectively evaluate the efficacy of obturator nerve anesthesia after a parasacral block. Patients scheduled for knee surgery had a baseline adductor strength evaluation. After a parasacral block with 30 mL 0.75% ropivacaine, sensory deficit in the sciatic distribution (temperature discrimination) and adductor strength were assessed at 5-min intervals. Patients with an incomplete sensory block (defined as a temperature discrimination score of less than 2 in the 3 cutaneous distributions of the sciatic nerve tested) 30 min after the parasacral block were excluded from the study. Subsequently, a selective obturator block was performed with 7 mL 0.75% ropivacaine and adductor strength was reassessed at 5 min intervals for 15 min. Finally, a femoral block was performed using 10 mL 0.75% ropivacaine. Patient discomfort level during each block was assessed using a visual analog scale (VAS). Thirty-one patients completed the study. Five patients were excluded as a result of inadequate sensory block in the sciatic distribution 30 min after the parasacral block (success rate of 89%). Thirty min after the parasacral block, adductor strength decreased by 11.3% +/- 7% compared with baseline (85 +/- 24 versus 97 +/- 28 mm Hg, P = 0.002). Fifteen min after the obturator nerve block, adductor muscle strength decreased by an additional 69% +/- 7% (16.6 +/- 15 versus 85 +/- 24 mm Hg, P < 0.0001). VAS scores were similar for all blocks (26 +/- 19, 28 +/- 24, and 27 +/- 19 mm for parasacral, obturator, and femoral respectively). Four parasacral blocks were simulated in 2 fresh cadavers using 30 mL of colored latex solution. The spread of the die in relation to the obturator nerve was assessed. Injection of 30 mL colored latex into cadavers resulted in spread of the injectate restricted to the sacral plexus. These findings demonstrate the unreliability of parasacral block to achieve anesthesia of the obturator nerve. A selective obturator block should be considered in the clinical setting when this is desirable.
authors.affiliation: *Department of Anesthesiology and Intensive Care Medicine, Private Hospital Group of Center Alsace, Colmar, France; †Department of Anesthesiology and Intensive Care Medicine, Nancy University Hospitals, Nancy, France; ‡Department of Anesthesiology, Hôpital de la Conception, Marseille, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Jochum
authors.forename: Gabriella
authors.initials: G
authors.lastname: Iohom
authors.forename: Olivier
authors.initials: O
authors.lastname: Choquet
authors.forename: Dioukamady
authors.initials: D
authors.lastname: Macalou
authors.forename: Samba
authors.initials: S
authors.lastname: Ouologuem
authors.forename: Pascal
authors.initials: P
authors.lastname: Meuret
authors.forename: Freddy
authors.initials: F
authors.lastname: Kayembe
authors.forename: Michel
authors.initials: M
authors.lastname: Heck
authors.forename: Paul-Michel
authors.initials: PM
authors.lastname: Mertes
authors.forename: Hervé
authors.initials: H
authors.lastname: Bouaziz
mesh_terms: D000368:Aged; D000577:Amides / Q000009:adverse effects; D000779:Anesthetics, Local / Q000009:adverse effects; D019645:Arthroplasty, Replacement, Knee; D001182:Arthroscopy; D005260:Female; D006801:Humans; D007022:Hypotension / Q000139:chemically induced; D007717:Knee / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D009407:Nerve Block / Q000009:adverse effects; D009460:Neurologic Examination; D009776:Obturator Nerve; D010147:Pain Measurement; D000077212:Ropivacaine; D012584:Sciatic Nerve; D013126:Spinal Nerve Roots / Q000502:physiology
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine