Two methods were studied: lidocaine pretreatment and propofol mixture. The use of lidocaine as a pretreatment to reduce the pain of propofol injection is based on its local anesthetic effect on the veins. Due to the different methods used in the studies, different reductions in the incidence of pain caused by propofol injections have been reported. McCulloch and Lees[26] showed that when using the dorsal hand vein, 10 mg of lidocaine given immediately before propofol injection reduced the incidence of pain from 37.5% to 17.5%. This result was not statistically significant. 

However, Ganta and Fee[33] reported that the incidence of pain with 10 mg of lidocaine administered immediately before propofol injection was significantly reduced from 49.4% to 21.1%. The differences between the two studies may be due to differences in the pre-medication used and the rate of propofol injection. McCulloch and Lees did not use pre-medication and administered propofol within 20 seconds, while Ganta and Fee used 10 mg of diazepam as pre-medication and administered propofol within 30-40 seconds. Lyons et al. [34] reported that preconditioning with 10 mg of lidocaine 10 s before propofol injection significantly reduced the incidence of injection pain from 64% to 44%. 

Nicol et al. [30] reported that lidocaine 10 mg 15 s before propofol injection could significantly reduce the incidence of pain from 51% to 35%. Mangar and Holak[6] found that giving 100 mg of lidocaine 1 minute before propofol injection reduced the severity of pain, but did not reduce the incidence of pain. The administration of 100 mg lidocaine (modified Bier block) after inflating the arm tourniquet to 50 mmHg for 1 minute actually eliminates the pain associated with propofol injections.

Ewart and Whitwam found that the incidence of pain increased with the increase in the time interval between injections of two drugs. 20 mg of lidocaine is injected into a vein in the back of the hand and a tourniquet is placed at the proximal end of the forearm to create a "mini Bier block." The tourniquet is released at various intervals and propofol is injected. Pain was significantly reduced in the lidocaine group given 10 or 30 seconds before propofol. Their study showed that lidocaine was effective in reducing pain when given before propofol. Mixing lidocaine with propofol The rationale for mixing lidocaine with propofol is based on the premise that lidocaine can act as a stabilizer for the kinin cascade, as proposed by Scott et al.