QUANTITATIVE-EVALUATION OF TOURNIQUET LEAK DURING IV REGIONAL ANESTHESIA OF THE UPPER AND LOWER-LIMBS IN HUMAN VOLUNTEERS

Although it is accepted that during i.v. regional anaesthesia (IVRA) l ocal anaesthetic can leak under the tourniquet into the systemic circu lation, no published study has evaluated this leak quantitatively. In volunteers, during two random sessions, we have simulated IVRA using s tandard techniques with a radiolabelled compound which is chemically s imilar to lignocaine and has comparable tissue distribution (0.1 mg of HIDA labelled with 100 mu Ci of Tc-99m in 40 ml of saline). The decre ase in radioactivity was measured with a gamma camera for the 20 min o f tourniquet inflation and for the 20 min of washout after cuff deflat ion. While the tourniquet was inflated, the leak for the lower limb (m ean 29 (SD 8)%) was significantly greater (P < 0.004) than the leak fo r the upper limb (15 (5)%). Moreover, in each of 10 volunteers, the le ak was always greater for the lower than the upper limb. During the fi rst 3 min after tourniquet deflation the loss of radioactivity was 58 (8)% of the maximal amount for the upper limb and 39 (8)% for the lowe r limb (P < 0.001). As the leak under the tourniquet was significantly greater for the lower than the upper limb, we conclude that IVRA for the lower limb can be associated more frequently with a shorter durati on of successful anaesthesia and/or failure.