Effect of stellate ganglion block on the plasma concentration of noradrenaline in rabbits suffering from acute pain / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effect of stellate ganglion block(SGB) on the plasma concentration of noradrenaline(NE) in rabbits suffering from acute pain and the possible mechanism.Methods Fourteen healthy rabbits of both sexes weighing 2.5 2.8 kg were anesthetized with 20% urethane 1 g?kg -1 . Spontanous breathing was maintained. Right stellate ganglion was exposed aseptically. An epidural catheter was fixed with one end placed close to stellate ganglion and the other end outside the neck through a hole on the skin for administration of drugs. One week later 3% formalin 0.2ml was injected subcutaneously into plantar region of the right paw. Pain response was observed . 60 min after formalin injection 0.25% bupivacaine 0.5ml was injected through catheter (bupivacaine group n=7) while in control group (n=7) normal saline 0.5ml was injected. The effect of SGB was confirmed by ptosis and miosis. Blood samples were taken from edge vein of the ear 10 min before (T 0) and 10(T 1), 30(T 2), 50min(T 3) after subcutaneous injection of formalin and 10min(T 4), 30min(T 5), 50min(T 6) after bupivacaine or normal saline injection for determination of plasma NE concentration by radioimmunoassay.Results Plasma NE concentration increased significantly after subcutaneous formalin injection and peaked at T 1,then decreased slightly at T 2 and T 3. In group B, plasma NE concentration decreased significantly after bupivacaine injection, while in control group there was no significantly change in plasma NE concentration after normal saline injection.Conclusions SGB reduces the increased plasma NE concentration in rabbits suffering from acute pain. This may be the possible mechanism of analgesia provided by SGB.