The ultrasonic coagulating and cutting system injures nerve function.

BACKGROUND

Although, many surgeons have used ultrasonic coagulating and cutting systems and shears (LCS) when carrying out endoscopic thyroidectomies and parathyroidectomies, in our experience some patients had temporary paralysis of the recurrent laryngeal nerve (RLN) after these operations. We had sometimes noticed that the heat of the blade of the LCS was increased just after use; therefore, we designed an RLN model, and investigated the damage to the RLN which could be attributed to the heat of the LCS.

METHODS

We investigated the effects of the heat of the LCS blade on rat femoral and sciatic nerves, using temperature measurement, histological examination and evoked electromyography.

RESULTS

The temperature of the LCS blade exceeded 150 degrees C after 30 seconds when it was not used for cutting. When we used the LCS to cut rat muscle or fat tissue, the temperature of the blade exceeded 100 degrees C after 20 seconds. There was no damage to the nerve histologically when the LCS was used for less than 20 seconds at a distance of 3 mm. Electrophysiological study showed that touching the nerve with the LCS blade after only 5 seconds of use resulted in damage to the nerve.

CONCLUSIONS

Our results suggest that the RLN should not be touched directly with the blade just after it has been used, and that it is possible to use the LCS at a distance of 3 mm from the RLN for less than 20 seconds at level 3. In order to maintain these distances, the RLN must be endoscopically visualized during surgery of the neck.