MedWire News: Use of the antecubital vein and “a small dose” of opioids are probably the best interventions to use in clinical practice to prevent pain on injection of propofol, say the authors of a systematic review and meta-analysis.

The analysis of 177 randomized trials, involving 25,260 adults, revealed that use of an antecubital vein instead of a hand vein was the most effective single intervention, reducing risk for pain by 86%.

Use of opioids halved the risk. Other single interventions were more effective, but Christian Apfel (University of California, San Francisco, USA) and colleagues say that, as opioids are commonly used in anesthesia protocols, it “seems reasonable” to incorporate them at this early stage of anesthesia induction.

The overall risk for pain on propofol injection was about 60%. The researchers calculated that, if the effects of the two approaches are additive, then their combined use should therefore reduce the risk for pain on propofol injection to just 5%.

“In other words, further interventions are unlikely to benefit more than one out of 20 patients,” they write in the BMJ. “Thereby, additional interventions would only provide limited additional benefit from a clinical standpoint.

Another very effective intervention, when using a hand vein, was pretreatment with lidocaine in conjunction with venous occlusion, which reduced the risk for pain by 71%.

Many previous studies have shown the efficacy of this approach, yet it has not become widespread.

“A reason for this may be the additional procedural steps involved in the intervention, leading to some delay when swift induction is expected,” say Apfel and team.

Other effective interventions were use of a lidocaine-propofol admixture, lidocaine pretreatment, and use of ketamine, non-steroidal anti-inflammatory drugs, and propofol emulsions containing medium- and long-chain triglycerides. Reductions in pain risk with these interventions ranged from 25% to 60%.

If it is deemed necessary to use a hand vein for propofol injection, the researchers suggest pretreatment with lidocaine or ketamine and use of a propofol emulsion containing medium- and long-chain triglycerides. This strategy would reduce overall risk for pain to 10%, they say.

But they caution: “These estimates of multiplicative treatment effects are based on the assumption of independence and, strictly speaking, require confirmation in randomized, controlled trials.”