Bipolar Electrosurgery

In bipolar electrosurgery, as in unipolar electrosurgery, current enters the patient through one electrode. However, instead of traversing the body to be collected by a dispersive electrode at a site remote from the surgery, injected current is collected millimeters away from the first electrode by a second electrode that appears identical to the first. Bipolar surgery is performed by two pencilpoint electrodes arranged at the tips of a forceps. Electric current flows through patient tissue only at the site of surgery, where it is confined to the few millimeters between the electrodes. Bipolar devices are required when electrosurgery is performed on an ovary or a fallopian tube. Several cases of fatal bowel injury have occurred after female sterilizations with unipolar devices.^{[49] [50]}

Patients with implanted pacemakers frequently come to the operating room for procedures requiring electrosurgery (see Chapter 35 ). For such patients, bipolar devices are used whenever possible. Nevertheless, on rare occasions, pacemaker interference does occur. The avoidance of pacemaker interference depends on the type of pacing electrodes (i.e., unipolar or bipolar) in the patient, how well the pacemaker circuitry is shielded, and the strength and the proximity of the discharge from the electrosurgical unit. There are also cases in which patients have pacemakers, but surgery requires the use of unipolar electrocautery. In all electrosurgery for pacemaker patients, grounding pads should be placed as far away as possible from the pacemaker and its wires. The path from the grounding pad to the electrosurgical tip should not traverse the pacemaker circuit. Because of capacitive coupling, it is possible for electrosurgical noise to inhibit or turn off any pacemaker or to disrupt the pacing program in a programmable pacemaker. Such interference can result in complete heart block and no pacing or in severe tachycardia. Anesthesiologists should always be prepared to reset a pacemaker to the asynchronous mode (i.e., regular, uninhibited pacing). A preoperative consultation with a cardiologist from the electrophysiology laboratory is always appropriate. For sufficiently complex pacemakers or patients, it is important to have a cardiologist and appropriate pacemaker programming equipment present or immediately available during surgery. Isoproterenol, a pharmacologic pacer, should be available on the anesthesiologist's drug cart when the patient has a cardiac pacemaker. Concentrations of 1 µg/mL are appropriate for small bolus injections.