Lord S M, Barnsley L, Bogduk N
Cervical Spine Research Unit, University of Newcastle, Callaghan, Australia.
Clin J Pain. 1995 Sep;11(3):208-13. doi: 10.1097/00002508-199509000-00008.
The development of target-specific local anesthetic blocks has enabled pain physicians to explore the anatomical source of chronic spinal pain. However, such blocks rely on subjective responses and may be subject to the placebo effect. Comparative local anesthetic blocks have been advocated as a means of identifying true-positive cases and excluding placebo responders. This paradigm employs two local anesthetics with different durations of action; only patients who obtain reproducible relief and correctly identify the longer-acting agent are considered positive.
Our objective was to evaluate the reliability of comparative blocks of the medial branches of the cervical dorsal rami in the diagnosis of cervical zygapophysial joint pain.
We compared comparative blocks and the criterion-standard of randomized, double-blind, placebo-controlled blocks.
The study was conducted at a tertiary referral center.
We studied the first 50 consecutive patients referred for assessment of chronic neck pain (> 3 months' duration) after a motor vehicle accident, who completed a series of placebo-controlled blocks after an initial positive response. Patients were 41 +/- 11 years (mean +/- SD) old with a male/female ratio of 1:2.
Patients underwent three blocks using three different agents-lignocaine, bupivacaine, and normal saline--administered on separate occasions, in random order and under double-blind conditions. The diagnostic decision based on comparative blocks alone was compared with that based on placebo-controlled blocks.
Comparative blocks were found to have a specificity of 88%, but only marginal sensitivity (54%). Although comparative blocks result in few false-positive diagnoses, their liability is that they result in a high proportion of false-negative diagnoses. Expanding the comparative blocks diagnostic criteria to include all patients with reproducible relief, irrespective of duration, increases sensitivity to 100% but lowers specificity to 65%.
Whether physicians use comparative or placebo-controlled blocks depends upon the implications of their results. If innocuous therapy will be prescribed, comparative blocks might suffice. However, when diagnostic certainty is critical, such as in a medicolegal context or when surgical intervention is contemplated, placebo-controlled blocks are recommended.
针对特定靶点的局部麻醉阻滞技术的发展，使疼痛科医生能够探寻慢性脊柱疼痛的解剖学根源。然而，此类阻滞依赖主观反应，可能会受到安慰剂效应的影响。比较性局部麻醉阻滞被提倡作为一种识别真阳性病例并排除安慰剂反应者的方法。该模式采用两种作用时间不同的局部麻醉药；只有那些获得可重复缓解且能正确识别作用时间较长药物的患者才被视为阳性。
我们的目的是评估颈背神经内侧支比较性阻滞在诊断颈椎小关节疼痛中的可靠性。
我们比较了比较性阻滞与随机、双盲、安慰剂对照阻滞的标准方法。
该研究在一家三级转诊中心进行。
我们研究了首批50例因机动车事故后慢性颈部疼痛（病程>3个月）前来评估的连续患者，这些患者在初始阳性反应后完成了一系列安慰剂对照阻滞。患者年龄为41±11岁（平均±标准差），男女比例为1:2。
患者在双盲条件下，分三次使用三种不同药物——利多卡因、布比卡因和生理盐水——进行阻滞，给药顺序随机。将仅基于比较性阻滞的诊断决策与基于安慰剂对照阻滞的诊断决策进行比较。
发现比较性阻滞的特异性为88%，但敏感性仅为边际水平（54%）。虽然比较性阻滞导致的假阳性诊断较少，但其缺点是会导致较高比例的假阴性诊断。将比较性阻滞的诊断标准扩大到包括所有获得可重复缓解的患者，而不考虑缓解持续时间，可将敏感性提高到100%，但特异性降至65%。
医生选择使用比较性阻滞还是安慰剂对照阻滞，取决于结果的影响。如果将采用无害治疗，比较性阻滞可能就足够了。然而，当诊断确定性至关重要时，例如在法医学背景下或考虑进行手术干预时，建议采用安慰剂对照阻滞。
