The effects of ornipressin and adrenaline on lignocaine nerve blocks

An electrophysiological method measuring nerve conduction following the electrical stimulation of a sciatic nerve branch in anaesthetised rats was used to evaluate under strictly controlled conditions the effects of 1:100,000 adrenaline and of 0.03 IU X ml-1 ornipressin on the speed of onset, depth and duration of lignocaine anaesthesia. It was shown that compared with plain lignocaine, lignocaine with ornipressin produced shorter onset of anaesthesia and improved its depth and duration. Adding adrenaline to lignocaine merely extended its duration of action. Ornipressin, therefore, even at low concentration, can be considered as a viable alternative vasoconstrictor to adrenaline, the use of which is undesirable in some categories of patients.