Morphine injected around the stellate ganglion does not modulate the sympathetic nervous system nor does it provide pain relief

Abstract

Six patients with a presumptive diagnosis of upper limb reflex sympathetic dystrophy and 1 patient with anaesthesia dolorosa had pain and sympathetic activity assessed before and after injection of bupivacaine and morphine around the stellate ganglion. Sympathetic modulation was assessed by measuring the effect of each injection on the inspiratory gasping response (IGR), a measure of central arousal, the sympathetic skin response (SSR), a measure of peripheral sudomotor activity and the plethsymographic wave (PW), a measure of peripheral vasomotor activity. There were 5 women and 2 men with a mean age of 49 years (range: 41-66 years). The duration of pain varied from 9 months to 7 years. Bupivacaine abolished the IGR and SSR and increased the amplitude of the PW in all patients without any demonstrable sensory or motor blockade in the treated limb, nor did it have any effect on the contralateral IGR or PW. Bupivacaine did provide short-term pain relief in 4 out of 7 patients. Morphine did not produce any demonstrable effect on the sympathetic nervous system nor did it provide pain relief for any patient. Thus these data do not support injection of morphine around the stellate ganglion as it neither modulated sympathetic activity nor provided pain relief.