Energy based surgical instruments : With particular focus on collateral thermal injury

Iatrogenic post-operative nerve dysfunction is a significant problem in many areas of surgery and can be caused by collateral thermal injury from activation of energy based surgical devices (EBD). The aims of this thesis were to: create an animal model in order to compare mono- and bipolar electrosurgery (ES) and an ultrasonic dissection (UD) with regard to collateral thermal nerve injury, and with data of a national multicenter register to study the use of EBD and their potential effects on operation time and complication rates in thyroid surgery.urgical devices (EBD). Material and Methods: The biceps femoris muscle of 104 anesthetized rats was cut in a standard manner adjacent to the sciatic nerve using clinical relevant settings of mono- and bipolar ES and UD. The sciatic nerve was stimulated supramaximally and the electromyographic (EMG) potential recorded before and after each experiment. Nerve dysfunction was defined as > 10% reduction of the evoked EMG potential. In Paper II and III temperature was measured before, during and after instrument activation. The sciatic nerves were coded and examined blinded with light (LM) and electron microscopy (EM). Advanced temperature measurements were conducted in Paper II and III. In Paper IV, the use of EBD was specifically registered in the Scandinavian Quality Register for Thyroid, Parathyroid and Adrenal Surgery (SQRTPA) during one year and 1297 patients were included. Operation time, recurrent laryngeal nerve (RLN) injury, post-operative hypoparathyroidism and the use of topical haemostatic agents were compared between bipolar ES, electric vessel sealing (EVS) and UD. Clamp and Tie technique (C-A-T) being without thermal risk constituted the control group. Results: In Paper I the EMG potential was significantly more frequent reduced in the monopolar and bipolar ES group compared to the UD group and LM showed significantly less nerve damage in the UD group. In Paper II exact temperature measurements was possible with thermoelectric micros sensors and the thermal dose was significantly less and with less variation for the UD compared to the bipolar ES. Similar to the Paper I the EMG potential was significantly more frequent reduced in the ES group. Moderate and severe morphological damage was significantly less common in the UD group compared to monopolar ES. We found no statistical correlation between the highest temperatures/doses and the degree of morphological damage or functional loss. In Paper III the temperature increase was significantly less and with shorter duration in the UD group, compared to bipolar ES. LM and EM demonstrated loss of density in the myelin sheet only in a small number of nerves in all groups after instrument activation 1 mm from the nerve. In Paper IV, operation time was significantly shorter in the UD group and significantly longer in the EVS and bipolar ES group, compared to C-A-T. Postoperative hypoparathyroidism with need for Calcium treatment at discharge and at 6 weeks was significantly higher with ES instruments compared to UD. The incidence of reported RLN injury was 2.5% at 6 weeks postoperatively without statistical differences between the groups. Topical haemostatic agents were more frequently used in the EBD groups compared to C-A-T. Conclusion: The experimental Papers (I-III) demonstrated a lower risk of adverse collateral thermal nerve injury with activation of the mechanical UD technique compared to ES techniques. In the nationwide multicenter register Paper (IV), the use of UD shortened end EVS increased operation time compared to the low cost C-A-T. The UD instruments had a lower risk of hypoparathyroidism than electrosurgery