LACK OF EFFECT OF SPHENOPALATINE GANGLION BLOCK WITH INTRANASAL LIDOCAINE ON SUBMAXIMAL EFFORT TOURNIQUET TEST PAIN

Background and Objectives. The present study examined whether sphenopa latine ganglion block (SPGB) causes a reduction in the response to acu te nociceptive input that may account for the SPGB-induced relief repo rted by many patients with chronic pain. Methods. In a double-blind, c ross-over design, 16 healthy volunteers underwent separate 15-minute s ubmaximal effort tourniquet tests before and after SPGB with 20% lidoc aine plus 1:100,000 epinephrine (SPGB(lidocaine)) or placebo (SPGB(sal ine)). Responses during each minute of tourniquet inflation were conve rted to a 1 to 16 scale and classified as nothing (1), mild sensation (2-4), strong sensation (5-7), slightly painful (8-10), definitely pai nful (11-13), and severely painful (14-16). Results. Maximum pain scor es reached 12.6 +/- 2.5 (mean +/- SD) pm-SPGB, 10.9 +/- 3.5 after SPGB (saline) and 11.1 +/- 2.5 after SPGB(lidocaine). No significant differ ences were noted between SPGB(lidocaine) and SPGB(saline) at any of th e 15 time points (p = NS by repeated measures ANOVA and paired t-test) . However, retrospective grouping of time points noted that scores aft er SPGB(lidocaine) were lower in the ''strong sensation'' range. Concl usion. SPGB does not lessen scute extremity pain to a significant degr ee and is not in and of itself an effective means of analgesia for acu te pain. Its potential impact on nociceptive stimuli that elicit a ''s trong sensation'' (i.e., a score of 5-7 in the present study) should b e evaluated in hyperpathic pain states and in states with exaggerated aversive responses.