Pain perception with pH buffered peribulbar anaesthesia: a pilot study

Abstract

Aims-To determine the relation between pH of anaesthetic solutions and patient perception of pain with peribulbar injection of local anaesthesia. Methods-This prospective randomised controlled double blind pilot study involved 60 consecutive patients who received a peribulbar block with either a standard acidic local anaesthetic of 5 ml 2% lignocaine and 5 ml of 0.5% bupivacaine (solution A), or an alkalinised solution composed of the same anaesthetic agents but with a pH of 7.44 (solution B). Before surgery patients were asked to grade the pain of both the preoperative dilating drops and the peribulbar injection using a visual analogue scale. Results-The mean pain scores were similar in the two treatment groupsslightly higher (4.97) in group B who received the buVered solution, compared with group A (4.84) who received the plain solution. The small diVerence (−0.13, 95% confidence limits −1.6 and +1.3) was not significant. There was, however, a highly significant association between pain threshold ("drop pain") and injection pain levels (p<0.0001). Conclusion-This study showed no diVerence in the reduction in the pain experienced by patients undergoing peribulbar anaesthesia with pH buVered local anaesthetic. The study suggests the importance of "pain threshold" as a confounder and also showed the considerable pain felt by some patients on instillation of the preoperative dilating drops. (Br J Ophthalmol

Peribulbar anesthesia for cataract surgery: Effect of lidocaine warming and alkalinization on injection pain, motor and sensory nerve blockade

“…[1] The increase in relative concentration of the non-ionized form allows for a more rapid diffusion through the tissues and might result in almost immediate sensory nerve blockade. [2–4] The nociceptor receptors are also less sensitive to the non-ionized form of the drug.…”

“…Pain during injection of local anesthetic solution is common and this is partly explained by the direct tissue irritation caused by injecting an acidic solution, Lidocaine hydrochloride (L-HCL). [ 1 ] The increase in relative concentration of the non-ionized form allows for a more rapid diffusion through the tissues and might result in almost immediate sensory nerve blockade. [ 2 – 4 ] The nociceptor receptors are also less sensitive to the non-ionized form of the drug.…”