One of the least desirable effects of propofol is the burning sensation a patient feels when it is injected into the vein. I've had many patients complain about the irritation from a previous anesthetic experience. Being in GI anesthesia, I've had much experience with this as a consequence of the high turnover of patients and the near universal use of propofol. After years of trying different methods to reduce the pain, I've had great success with a protocol of lidocaine followed by a propofol chaser.
It's very simple. When the patient is ready for induction, I give 30 mg of lidocaine and immediately follow that with 30 mg propofol. I then wait 30-60 seconds and then give another bolus of propofol of 30-40 mg. Continue this cycling of propofol boluses until the desired level of sedation is achieved. I've found that this eliminates the propofol burn greater than 90% of the time. The key I think is the small amount of propofol injected each time. The first bolus given as a 1:1 ratio with lidocaine seems to give good relief from vein irritation. Waiting 30 seconds before giving the next bolus allows the patient to achieve some level of sedation so that they have less awareness of the burning with the subsequent boluses. Another advantage of giving small intermittent boluses is decreased risk of having the patient go apneic, which can happen if they are given a large initial amount of the drug.
Why not give a benzo like Versed as a sedative? In GI the cases are very quick. Even though Versed is short acting it is not short enough. You wind up with a recovery room full of patients sleeping off their Versed. Patients achieve alertness much faster after using only propofol. Versed induced amnesia is also inconsistent; some patients still remember the pain while others are amnestic five seconds after Versed is given. Patients are also happier when they wake up faster from anesthesia. Many patients complain of being drowsy for hours when they go home after being given Versed. They report feeling alert and normal when only given propofol.
Fentanyl has also been advocated as a preop sedative to alleviate the burn. My experience has been that narcotics have an unpredictable effect on respiration, especially when given with propofol. Some patients do fine while others go into prolonged apnea when propofol is given. And again the patient takes longer to wake up in recovery. There is also an increased risk of post operative nausea and vomiting when adding a narcotic to your anesthesia. PONV is something patients find extremely unpleasant and want to avoid at all cost.
Of course there are some instances where this intermittent bolusing of propofol doesn't work. If you are trying to achieve a rapid sequence intubation, screw the burning pain. Just inject and go. The pain is the last thing you should be worried about. Also patients who have tiny veins will almost always have pain with injection no matter what protocol you use to prevent it. They just have to live with it for a few seconds until they fall asleep.
Obviously there is no scientific basis for this method of induction. It was arrived through years of propofol injections. But give it a try. I would like to hear how other anesthesiologists minimize the amount of burning when they give the milk of amnesia.