B. Åkerman

Influence of Hyaluronidase Upon Local Infiltration Anaesthesia by Lidocaine: An Experimental Study in the Guinea-pig

A study was made in the guinea-pig to examine how the mucolytic enzyme hyaluronidase influenced the spread and duration of subcutaneously injected lidocaine with and without adrenaline. Addition of hyaluronidase 200 IU/ml to lidocaine 5 mg/ml plain solution diminished the spread of the analgesic efficacy but did not affect the duration of action. Addition of hyaluronidase 200 IU/ml to lidocaine 5 mg/ml containing adrenaline 5 micrograms/ml gave a significantly larger area of analgesia compared to the solution without the enzyme but slightly shortened the duration of action. The solution containing both adrenaline and hyaluronidase approximately doubled the distance necessary for satisfactory analgesia between two subcutaneous sites of administration, a finding that may have clinical implications.

EFFECT OF DIFFERENT TYPES OF ANAESTHESIA INCLUDING PERCUTANEOUS LOCAL ANAESTHESIA ON SURVIVAL OF EXPERIMENTAL SKIN FLAPS

Local anaesthesia by epicutaneous application of the ketocaine solution A2358 gave survival of experimental skin flaps in the guinea pig which corresponded on average to 71% of the total flap. The survival after pentobarbitone anaesthesia, general anaesthesia with ether, and infiltration of prilocaine without and with adrenalin varied between 41 and 53%. The difference in effect between percutaneous anaesthesia with A2358 and the other procedures was statistically significant (p less than 0.001). Epicutaneous application of A2358 followed by one of the other forms of anaesthesia gave a flap survival that did not differ from that following local anaesthesia with A2358 alone, except when followed by injection of prilocaine with adrenalin. The improved survival after epicutaneously applied A2358 is probably attributable to an effect on the peripheral vascular bed resulting in increasing blood supply and nutrition. It may be possible that A2358, for example, could be used in man as a complement to other forms of anaesthesia to provide enhanced tissue survival in skin flaps.

The effects of venous blood, silicone gel and prilocaine on capsular contraction around silicone implants studied with a new method in the rat.

The pressure exerted by wound tissue on a subcutaneously implanted silicone expander was studied in rats. A significant increase in pressure was noted four and eight weeks postoperatively when venous blood was instilled into the cavity around the expander, but this increase was significantly reduced at eight weeks if 1.0 ml of prilocaine 5 mg/ml with adrenaline 4 micrograms/ml was instilled at the same time as the blood. Instillation of silicone gel outside the expander tended to increase the pressure eight weeks postoperatively, but there was no increase when silicone gel was given together with prilocaine and adrenaline. The next step is to investigate whether prilocaine with adrenaline instilled around an implanted mammary prosthesis in humans is not only capable of reducing pain and bleeding but can also inhibit capsular contracture.