[Modification of the guanethidine block for diagnosing reflex sympathetic dystrophy.]

For diagnosis of the pain origin in reflex sympathetic dystrophy (RSD), sympathetic blocks, including the intravenous regional guanethidine (IVRG) block after Hannington-Kiff, are recommended. Since the results obtained with this kind of block are sometimes unsatisfactory, modifications were made to increase its technical efficacy.

Forty-seven RSD patients were investigated. Among the typical triad of RSD symptoms, all patients showed distally generalized oedema of the affected extremity and complained of spontaneous pain. This pain showed an orthostatic component in all but two patients. The modifications of the IVRG-block were: (1) distal (in contrast to proximal) suprasystolic compression of the affected extremity before i.v. injection of guanethidine (GA); (2) reduction of the recommended dose of GA (10-30 mg) to 2.5 mg GA for each block; (3) no additional local anaesthetics, which are recommended for suppression of the typical pain following GA injection, since this pain allows identification of the distribution of the GA (complete? incomplete?) within the symptomatic area; (4) repeated subsequent injection of physiological saline to improve the distribution of GA within the symptomatic area.

Injection of GA and repeated injections of saline (mean: 43 ml, range: 10-95 ml) elicited pain-lessening in intensity with repetition-in the same region as the spontaneous pain of RSD in all but the two patients mentioned above. Following the modified IVRG block, all but these two patients experienced significant pain reduction (Table 1). In total, 87% of all 47 patients under study were acutely (for at least 1 day) pain-free after the block.

The modified IVRG block seems to have a high diagnostic value with respect to the presence of a sympathetic contribution to the pain in RSD. As a reduced GA dose/block is used, this form of the block appears to be safer than other kinds of sympathetic blocks.