title: The contribution of sympathetic mechanisms to postamputation phantom and residual limb pain: a pilot study.
abstract: Postamputation pain (PAP) affects over 60% of major limb amputees. One of the main challenges in treating PAP is the difficulty involved in identifying pain mechanism(s), which pertains to both residual limb pain (RLP) and phantom limb pain (PLP). In this study, sympathetic blocks were performed on 17 major limb amputees refractory to treatment, including 2 placebo-controlled blocks done for bilateral amputations. One hour postinjection, mean RLP scores at rest declined from 5.2 (SD 2.8) to 2.8 (SD 2.6) (P = .0002), and PLP decreased from 5.3 (SD 3.1) to 2.3 (SD 2.1) (P = .0009). By 1 week, mean pain scores for RLP and PLP were 4.3 (SD 2.9) and 4.2 (SD 3.0), respectively. Overall, 8 of 16 (50%) patients experienced ≥50% reduction in RLP 1-hour postinjection, with the beneficial effects being maintained at 1 and 8 weeks in 4 and 1 patient(s), respectively. For PLP, 8 of 15 (53%) patients obtained ≥50% decrease in pain 1-hour postblock, with these numbers decreasing to 2 patients at both 1 and 8 weeks. In the 2 bilateral amputees who received controlled injections, mean PLP and RLP at rest scores went from 4.0 and 3.3 to 4.0 and 2.5 1-hour postblock, respectively, on the placebo side. On the treatment side, mean PLP and RLP scores decreased from 7.5 and 6.5, respectively, to 0.
  
  
  CONCLUSIONS
  The results of this study suggest that sympathetic mechanisms play a role in PLP and to a lesser extent, RLP, but that blocks confer long-term benefits in only a small percentage of patients.
authors.affiliation: Pain Management Division, Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, 550 North Broadway, Baltimore, MD 21029, USA. scohen40@jhmi.edu
authors.forename: Steven P
authors.initials: SP
authors.lastname: Cohen
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Gambel
authors.forename: Srinivasa N
authors.initials: SN
authors.lastname: Raja
authors.forename: Sam
authors.initials: S
authors.lastname: Galvagno
mesh_terms: D000759:Adjuvants, Anesthesia / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000671:Amputation, Surgical; D000674:Amputees / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008874:Midazolam / Q000627:therapeutic use; D008875:Middle Aged; D010146:Pain / Q000150:complications* / Q000188:drug therapy / Q000523:psychology*; D010147:Pain Measurement; D010591:Phantom Limb / Q000150:complications* / Q000188:drug therapy / Q000473:pathology; D010865:Pilot Projects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D013565:Sympatholytics; D055815:Young Adult
chemical_list: D000759:Adjuvants, Anesthesia; D013565:Sympatholytics; D008874:Midazolam