SYMPATHETIC - BLOCKADE DOES NOT ENHANCE TISSUE WARMING DURING ISOLATED HEATED LIMB PERFUSION

Isolated, heated limb perfusion is used for the treatment of locally r ecurrent melanoma, intransit metastases, and acral lentiginous melanom as. Tissue warming during this procedure requires adequate perfusion w ithin the isolated extremity. At our institution, spinal or epidural a nesthesia was used to produce sympathetic blockade and vasodilation fo r lower extremity procedures. More recently, we began using mild syste mic hyperthermia to produce active thermoregulatory vasodilation. In t he presence of heat stress, sympathetic blockade may actually decrease skin blood flow because active cutaneous vasodilation, which is assoc iated with sweating, is dependent on intact sympathetic innervation. W e therefore investigated whether the continued use of neuraxial blocka de was justified. Twenty patients undergoing lower extremity perfusion s were alternately assigned to receive either combined general and spi nal anesthesia or general anesthesia alone. All were aggressively warm ed using forced air and circulating water. There were no significant d ifferences in tissue temperatures (measured at four sites in the isola ted limb) between groups at any time before or after the start of perf usion. Similarly, pump flow (715 +/- 211 ml/min versus 965 +/- 514 ml/ min) and the time required to achieve an average tissue temperature of 39 degrees C (43 +/- 16 vs 34 +/- 13 min) were not different between groups (spinal versus no spinal). Sweating was observed in all but thr ee patients at esophageal temperatures of 37.9 +/- 0.6 degrees C. We c onclude that sympathetic blockade confers no added benefit for tissue warming during isolated limb perfusions in the presence of induced mil d systemic hyperthermia. Implications: Sympathetic blockade prevents a drenergic vasoconstriction, but also inhibits active, neurally mediate d cutaneous vasodilation (a normal thermoregulatory response to heat). In slightly hyperthermic patients, we demonstrated that spinal anesth esia does not improve convective tissue warming during isolated, heate d limb perfusion. Mild systemic hyperthermia may promote greater vasod ilation than sympathetic blockade.