“Shock treatment” reduces postoperative nausea and vomiting

December 30, 2007

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).

The Study:

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.

Placing the electrodes for monitoring and prevention of PONV

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