Palsy of the recurrent laryngeal nerves in association with an ultrasonic activated device during thoracoscopic esophagectomy with three-field lymphadenectomy

Background Ultrasonic activated devices (USADs) may produce inadvertent injuries due to heat or shock waves. However, thermal injury and shock waves are considered to be avoidable if these devices are used appropriately. Methods Utilizing a porcine model, we examined the relationship between the occurrence of tissue damage around the iliac artery and sciatic nerve and the usage of an USAD. Thereafter, we prospectively determined the clinical outcomes following the usage of the USAD during dissection along the recurrent laryngeal nerves (RLN) in 114 consecutive patients who underwent thoracoscopic esophageal surgery. Results The temperatures measured in the pig iliac artery and sciatic nerve more than 2 mm from the activating blade (at a power setting of 70 %, within 2 s) did not increase to 42 °C. In a subsequent clinical series using the short activating technique according to the findings of in vivo experiments, scheduled laryngoscopic studies showed the rate of vocal cord palsy after esophagectomy to be 39 %, which was more sensitive than the substantial presence of hoarseness (28 %). Conclusions Adverse effects by using the USAD on the nerves may be avoidable if the activation of the current using an USAD is conducted within 2 s at positions more than 2 mm from the nerves. This short activation technique using the USAD is therefore considered to be safe and feasible for lymph node dissection along the RLNs during thoracoscopic esophagectomy, although the apparent reasons for postoperative dysfunction in the vocal cords remain unclear.