The Enterra GES is placed surgically under general anesthesia, commonly via laparotomy or minimal access surgical techniques (laparoscopically or robotically assisted). Preoperative intravenous antibiotics are given. The system consists of a pair of electrodes connected to a pulse generator. The 2 stimulation leads are inserted into the gastric muscularis propria 1 cm apart along the greater curvature 10 cm proximal to the pylorus. Upper endoscopy is performed to ensure that the leads do not penetrate through the mucosa into the stomach lumen; if this occurs, repositioning of the lead is necessary. A horizontal incision through the skin is made, and the distal ends of the stimulating wires are tunneled through the abdominal wall and connected to the pulse generator. The impedance (resistance) between the wires is measured to ensure the appropriate range (200-800 Ohms). The neurostimulator with the distal ends of the stimulating wires is then placed into the subcutaneous pocket and sutured to the underlying fascia. The pulse generator delivers a high-frequency, low-energy, 0.1-second train of pulses at a frequency of 12 cpm. Within each pulse train, individual pulses oscillate at a frequency of 14 cycles per second. The voltage of the stimulations is set to provide a current of 5 milliamps (mA; remembering that voltage = current × resistance).
Patients are often hospitalized with a recovery time of 1 to 3 days. Immediate postoperative care usually includes intravenous fluids, controlling any postoperative ileus, advancing diet, and providing analgesic pain medications. Hospital length of stay can be impacted by surgical technique.25 Patients are seen several weeks after discharge for assessment of the incision and toleration of diet. Medications for gastroparesis that patients were taking prior to the GES implantation are usually continued postoperatively, with a goal of reducing these medications over time. Patients are then followed every 3 to 12 months, depending on their clinical condition.
At follow-up visits, medications are reviewed and new treatments can be added if appropriate. The gastric stimulator is interrogated to determine if changes in resistance occurred; if necessary, minor readjustments can be made to keep the current at desired levels (5 mA). For persistent symptoms with GES treatment, the stimulator parameters can be adjusted after 3 months of follow up, typically first increasing the current from 5 to 7.5 mA and then to 10 mA. After this, the frequency can be increased from 14 Hz to 28 Hz, and then to 55 Hz. Rarely, the ON duration is increased from 0.1 to 1 second. Increasing the ON time can worsen symptoms in some patients, cause abdominal pain, and decrease the battery life from the usual 7 years.
Complications of GES
In an analysis of the Manufacturer and User Facility Device Experience (MAUDE) databank, Bielefeldt identified 1587 reports of adverse effects related to the gastric electric stimulator from January 2001 to October 2015.27 The most common adverse effects are reviewed here.
Skin erosion/wound dehiscence is one of the most common reported complications; it may be related to superficial placement or inadequate securing of the device to the fascia. Abscess can develop postoperatively due to hematogenous seeding or may be a sign of lead erosion into the lumen, tracking along the leads into subcutaneous tissue.28 It is important to warn patients to protect the area over the device from needle injections as this also can lead to hematoma formation and direct contamination of the device. If the device gets infected, it cannot be salvaged and requires explantation. Implantation of a new device can be attempted once all wound issues resolve.
