The effect of plain 0.5% 2–chloroprocaine on venous endothelium after intravenous regional anaesthesia in the rabbit

The possible venous endothelial toxicity of 0.5% 2–chloroprocaine without additives in intravenous regional anaesthesia (IVRA) was evaluated in rabbits. After exsanguination of a hind limb with an Esmarch's bandage a neonatal blood pressure cuff around the thigh was inflated (250 mmHg). For IVRA 4 ml of either plain 0.5% 2–chloroprocaine (pH 3.7), 0.9% NaCl (pH 6.0) or acidified NaCl (pH 3.7) was injected i.v. to the exsanguinated limb in a randomized, double–blind fashion. Each group comprised 15 rabbits. Eleven rabbits received 4 ml of 0.5 M or 1.0 M KC1, for the production of positive controls. Two hours after injection of the test solution the tourniquet was deflated and venous biopsies were taken one and 24 hours later for histological and immunocytochemical examination. Five to eight 24–hour samples from each group were also processed for electron microscopy. A macroscopic thrombus formation was observed in four rabbits after KC1 and in two after acidified NaCl administration. No inflammatory changes were observed at histologic and immunocytochemical examination of any of the vein samples. Electron microscopy revealed that KC1 had caused severe damage to the venous endothelium of four out of five samples and acidified NaCl had caused moderate damage to the endothelium of two out of seven samples. 2–chloroprocaine had caused moderate damage in four and severe damage in two of the vein samples; two samples were normal. No thrombus formation occurred. It is concluded that additive–free 2–chloroprocaine caused damage to the venous endothelium in rabbits when used for IVRA.