comparative study between lidocaine iontophoresis, intravenous lidocaine, and magnesium sulfate pretreatment for reduction of pain during propofol injection

ABSTRACT

Propofol produces anesthcsia with rapid recovery[1]- It has become the induction agent of choice for elective surgery in many countries. However, it causes pain or discomfort on intravenous injection in 28 - 90% of patients, which is a recognized complication that is recalled post operatively by 52-62% of those who experience it, and several methods have been advocated to reduce its incidence and severity [2]. The aim of the study is to compare the efficacy of three different techniques in attenuating pain induced propofol injection, which are magnesium sulfate pretreatment prior to propofol administration, in comparison to iontophoretically applied lidocaine, which is a transdermal anesthesia technique and i.v. injection of 2% lidocaine prior to propofol injection. A prospective, randomized double blind clinical study was conducted in 90 ASA I and II adults undergoing elective surgery. After obtaining a written informed consent, they were divided into 3 groups 30 patients in each. Group I [lidocaine group] pretreated with 2 ml. 2% lidocaine [40 mg], the pretreatment injection given over 30 seconds, 1 minute before the start of propofol infusion. This is accompanied by venous occlusion for 1 min.In group II [lontophoresis group], the negative electrode containing 4% lidocaine in a hydrogel was placed on the test area on the dorsum of the hand while, the positive electrode was placed 10 cm proximally, and both electrodes were connected to the iontophoresis unit [lomed Phoresor 11, Croydon, UK]. Electric current was set at 0.0 mA and was increased gradually to a maximum 4.0 mA. lontophoresis was discontinued when 40 mA min-1 dose was delivered and the time required was recorded, since, drug delivery is proportional to the total electrical charge, measured as a product of the current strength and duration of application [units miliampere x minutes, [mA.min-[1]][3]. In group III was pretreated with 2ml 50% magnesium sulfate [1 g] the pretreatment solutions were given over 30 seconds. 1 minute before the start of propofol infusion-This is accompanied by venous occlusion for 1 min. followed by propofol infusion. The infusion was stopped when the patient lost consciousness as detected by loss of eye lash reflex. Pain was assessed on a four point scale 0 = no pain, 1 = mild pain, 2 = moderate pain, 3= severe pain, at the start of propofol infusion and at 20 seconds intervals for 1 minute. The incidence of pain following i.v injection of propofol after pretreatment with lidocaine 2% was 17%in group I [lidocaine] compared to 39% and 46% in group II [lontophoresis] and group III [magnesium] respectively [P < 0.05]. Intravenous lidocaine pretreatment was more effective in attenuating pain during propofol administration than iontophoretically applied lidocaine and magnesium sulfate pretreatment. There was no statistically significant difference between group II and group Ill as regard pain reduction during propofol injection. intravenous lidocaine pretreatment is more effective in attenuating pain induced by propofol injection than topically applied lidocaine and magnesium sulfate pretreatment