Gastric Stimulator in Gastroparesis
Gastric electrical stimulation (GES) is used as a rescue therapy for patients with medically refractory gastroparesis to reduce nausea and vomiting symptoms, not primarily to accelerate gastric emptying. 1
Mechanism and FDA Approval
GES (Enterra Therapy) is FDA-approved under a Humanitarian Device Exemption (HDE) specifically for drug-refractory nausea and vomiting in gastroparesis. 1 The device delivers high-frequency (12 cycles per minute), low-energy electrical stimuli to the stomach. 1
The mechanism works primarily through activating vagal afferent pathways to influence central control mechanisms for nausea and vomiting, rather than by directly improving gastric motility. 2 This explains why symptom improvement occurs without necessarily normalizing gastric emptying rates. 1, 3
Clinical Positioning in Treatment Algorithm
GES should be reserved for patients who have failed standard medical management. 1 According to the American Gastroenterological Association, the treatment hierarchy is:
- First-line: Dietary modifications (small frequent meals, low fat/fiber, liquid-based nutrition), antiemetics, and prokinetic agents (metoclopramide, erythromycin) 1
- Second-line: Switching or combining prokinetic agents, neuromodulators for pain 1
- Third-line (refractory cases): GES implantation, botulinum toxin injection into pylorus, gastrostomy/jejunostomy tubes 1
Clinical Efficacy Evidence
The evidence shows GES provides significant symptom relief despite modest effects on gastric emptying:
- Symptom improvement: 97% of patients experienced >80% reduction in vomiting and nausea in multicenter studies, with effects persisting throughout follow-up periods. 3
- Gastric emptying: Initially unchanged, but improved in most patients at 12 months. 3 Studies consistently show improvement in symptoms with only modest changes in gastric emptying. 1
- Nutritional status: Average weight gain of 5.5% at 1 year, with 64% of patients on enteral/parenteral nutrition able to discontinue it. 3
- Healthcare utilization: Significant reduction in hospital admission days. 4
Patient Selection Criteria
Not all gastroparesis patients benefit equally from GES. Selection should be based on: 2
Favorable Predictors:
- Diabetic gastroparesis etiology (better outcomes than idiopathic) 2, 5
- Predominant symptoms of nausea and vomiting (rather than pain) 2
- Absence of significant abdominal pain 2
Negative Predictors (Poor Outcomes):
- Significant abdominal pain as predominant symptom 2
- Daily opiate use 2
- Idiopathic gastroparesis (compared to diabetic etiology) 2
Important Caveats
Temporary GES using percutaneous electrodes has been utilized to identify responders before permanent implantation (33/38 patients responded in one series), though this strategy lacks controlled study validation. 3, 2
The evidence base has limitations: randomized controlled trials in adults with diabetic and idiopathic gastroparesis show conflicting results, and no RCTs exist for chronic unexplained nausea and vomiting with normal gastric emptying or for pediatric gastroparesis. 2 However, large unblinded studies demonstrate long-term efficacy in selected adults. 2
Common pitfall: Expecting GES to normalize gastric emptying rates. The primary benefit is symptomatic relief through neuromodulation of nausea/vomiting pathways, not restoration of normal gastric motility. 1, 3, 2
Surgical complications are rare, with laparoscopic implantation being low morbidity. 5 Device removal rates are approximately 7% (4/55 patients in one large series). 4