Lidocaine Anal Block Limits Autonomic Dysreflexia During Anorectal Procedures in Spinal Cord Injury: A Randomized, Double-Blind, Placebo-Controlled Trial

PURPOSE Autonomic dysreflexia is a common and potentially dangerous hypertensive response to stimulation below the level of injury that occurs in patients with spinal cord injury at T6 or above. Rectosigmoid distention and anal manipulation are among the stimuli that may precipitate autonomic dysreflexia. Instillation of topical local anesthetic into the rectum is the recommended prophylaxis against autonomic dysreflexia of anorectal origin. However, a previous randomized, double-blind, placebo-controlled trial showed that topical lidocaine in the rectum does not blunt the autonomic dysreflexia response to anorectal procedures. The purpose of this study was to determine whether lidocaine anal sphincter block would be effective in limiting anorectal procedure-associated autonomic dysreflexia.METHODS We enrolled patients with chronic, complete spinal cord injury above T6, who were having anorectal procedures (flexible sigmoidoscopy and/or anoscopic hemorrhoid ligation). In a double-blind fashion, patients were randomized for intersphincteric anal block with 1 percent lidocaine or normal saline (placebo) before the procedure. Blood pressure was measured before, during, and after the block and procedure.RESULTS Thirteen patients received lidocaine, and 13 received placebo. The groups were similar in age, level of injury, duration of spinal cord injury, type of procedure, and procedure duration. The mean maximal systolic blood pressure increase for the lidocaine group was 22 ± 14 mmHg, significantly lower than the placebo group’s 47 ± 31 mmHg (P = 0.01).CONCLUSIONS Lidocaine anal block significantly limits the autonomic dysreflexia response in susceptible patients undergoing anorectal procedures.