Lack of effect of sphenopalatine ganglion block with intranasal lidocaine on submaximal effort tourniquet test pain.

Abstract

The present study examined whether sphenopalatine ganglion block (SPGB) causes a reduction in the response to acute nociceptive input that may account for the SPGB-induced relief reported by many patients with chronic pain. In a double-blind, crossover design, 16 healthy volunteers underwent separate 15-minute submaximal effort tourniquet tests before and after SPGB with 20% lidocaine plus 1:100,000 epinephrine (SPGBlidocaine) or placebo (SPGBsaline). Responses during each minute of tourniquet inflation were converted to a 1 to 16 scale and classified as nothing (1), mild sensation (2-4), strong sensation (5-7), slightly painful (8-10), definitely painful (11-13), and severely painful (14-16). Maximum pain scores reached 12.6 +/- 2.5 (mean +/- SD) pre-SPGB, 10.9 +/- 3.5 after SPGBsaline, and 11.1 +/- 2.5 after SPGBlidocaine. No significant differences were noted between SPGBlidocaine and SPGBsaline at any of the 15 time points (p = NS by repeated measures ANOVA and paired t-test). However, retrospective grouping of time points noted that scores after SPGBlidocaine were lower in the "strong sensation" range. SPGB does not lessen acute extremity pain to a significant degree and is not in and of itself an effective means of analgesia for acute pain. Its potential impact on nociceptive stimuli that elicit a "strong sensation" (i.e., a score of 5-7 in the present study) should be evaluated in hyperpathic pain states and in states with exaggerated aversive responses.