Nausea and vomiting after anesthesia, known as PONV (postoperative nausea and vomiting) is still common, despite new anesthetic agents and anti-nausea medications tested in hundreds of clinical studies. Acupuncture, and related techniques that use pressure (acupressure) or electrical pulses (transcutaneous electrical nerve stimulation) instead of needles, are fairly well studied in the prevention of PONV. These prevention measures seem to be as effective as the standard drugs. There are commercial bracelet devices that exploit this effect. The standard acupuncture point is called Nei guan, or P6, and is located on the inside of the wrist, between two tendons. These systems also appear to be effective in the prevention of motion sickness.
Neuromuscular blocking agents, also known as muscle relaxants (they are in fact reversible, paralyzing drugs), are used routinely in anesthesia for certain surgical procedures. The effect of these drugs is monitored with nerve stimulators, portable devices that deliver small electrical pulses via adhesive electrode patches applied to the skin. As the paralysis wears off, muscles supplied by the nerve that is stimulated begin to twitch in response to the electrical stimulation. Electrodes used for nerve stimulation are usually placed on the face (facial nerve monitoring) or on the wrist (ulnar nerve monitoring).
In a simple but clever clinical study done in hospitals in Switzerland and Austria and published in the flagship specialty journal Anesthesiology, investigators have combined nerve stimulation for monitoring of muscle relaxation, with the effects of acupuncture.
By moving one of the wrist electrodes about 2 cm from its usual (ulnar nerve) location toward the center of the wrist, corresponding with the location of both the median nerve and the P6 point, investigators guessed they might achieve both goals – that is, monitor paralysis while providing an anti-nausea effect. The stimulator was set at 1Hz, that is one electrical impulse per second, for the duration of each case.
The results of their experiment appear to confirm their hypothesis. The patients who got their stimulation/monitoring at P6 had roughly 25% less nausea after surgery than those who got conventional stimulation/monitoring at the ulnar nerve. All study patients were female, which may seem surprising unless you are aware that females are at greater risk of PONV than males – so its easier to prove in this population that your treatment is effective.
This and other acupuncture-related techniques seem to be more effective in the prevention of nausea than of vomiting, thus complementing the use of medications, which are better at preventing vomiting than nausea.
This is a surprisingly simple and effective approach to PONV prevention. Because of its low cost, and apparent lack of side-effects, this technique, which uses standard, readily available equipment might get rapidly adopted – assuming others can show the same results. We can be sure in the mean time that other researchers will attempt to replicate these results in their own studies.
If you are at high risk for PONV your anesthesiologist can easily emulate the methods of this study. (To estimate your risk, try the SurgiPrep PONV interview). The beneficial effect seems to wear off at about 6 hours, but this is the period when patients are most likely to feel sick or throw up. It may be possible to prolong the effect through use of one of the devices mentioned above.
Arnberger M, Stadelmann K, Alischer P, Ponert R, Melber A, Greif R. Monitoring of neuromuscular blockade at the P6 acupuncture point reduces the incidence of postoperative nausea and vomiting. ANESTHESIOLOGY 2007; 107:903–8. Read the abstract here.