27 August 2008

Gastric electrical stimulation is performed using an implantable device designed to treat chronic drug-refractory nausea and vomiting secondary to gastroparesis of diabetic or idiopathic etiology. Gastric electrical stimulation is also proposed as a treatment of obesity.

Currently, there is only one gastric electrical stimulator that has received approval from the U.S. Food and Drug Administration (FDA) The EnterraTM Therapy System (formerly named Gastric Electrical Stimulation (GES) System) manufactured by Medtronic is approved for treatment of chronic refractory gastroparesis. No gastric stimulation device is FDA approved for treatment of obesity. The GES system consists of four components :
  1. The implanted pulse generator
  2. Two unipolar intramuscular stomach leads
  3. The stimulator programmer
  4. The memory cartridge
With the exception of the intramuscular leads, all other components have been used in other implantable neurological stimulators, such as spinal cord or sacral nerve stimulators. The intramuscular stomach leads are implanted on the greater curvature of the stomach either laparoscopically or during a laparotomy and are connected to the pulse generator that is implanted in a subcutaneous pocket. The programmer sets the stimulation parameters, which are typically set at an on time of 0.1-sec alternating with an off time of 5.0 sec.

Gastroparesis is a chronic disorder of gastric motility characterized by delayed emptying of a solid meal. Symptoms include bloating, distension, nausea, and vomiting. When severe and chronic, gastroparesis can be associated with dehydration, poor nutritional status, and poor glycemic control in diabetics. While most commonly associated with diabetes, gastroparesis is also found in chronic pseudo-obstruction, connective tissue disorders, Parkinson disease, and psychological pathology. Treatment of gastroparesis includes prokinetic agents such as metoclopramide, and antiemetic agents such as metoclopramide, granisetron, or odansetron. Severe cases may require enteral or total parenteral nutrition.

Gastric electrical stimulation has also been investigated as a treatment of obesity as a technique to increase a feeling of satiety with subsequent reduced food intake and weight loss. The exact mechanisms resulting in changes in eating behavior are uncertain but may be related to neuro-hormonal modulation and/or stomach muscle stimulation. There are no gastric electrical stimulation devices approved by the FDA for the treatment of obesity. However, the Transcend® implantable gastric stimulation device, manufactured by Transneuronix Corporation, is currently available in Europe for treatment of obesity. Transneuronix is currently funding clinical trials in the United States and hopes to obtain FDA approval in a couple of years for use of the Transcend® device to promote weight loss in the management of obesity.

Policy/Criteria
  1. Gastric electrical stimulation may be considered medically necessary in the treatment of chronic intractable nausea and vomiting secondary to gastroparesis of diabetic or idiopathic etiology when all three of the following criteria are met :
    • Significantly delayed gastric emptying as documented by standard scintigraphic imaging of solid food
    • Patient is refractory or intolerant of two out of three classes of prokinetic medications and two out of three antiemetic medications. (see appendix for classes)
    • Patient's nutritional status is sufficiently low that total parenteral nutrition is medically necessary as defined in Regence Allied Health Policy, No. 6: Parenteral Nutrition; Home and Intradialytic
  2. Gastric electrical stimulation is investigational for all other indications including but not limited to the treatment of obesity.

Gastric Stimulation for the Treatment of Obesity

Gastric electrical stimulation is also proposed as a method of weight reduction in morbidly obese individuals. Gastric stimulation may make patients feel full with less food. Small clinical trials have reported positive outcomes in weight loss and maintenance of weight loss along with minimal complications. However, due to lack of long term outcomes from well-designed randomized clinical trials, conclusions cannot be made concerning the safety and efficacy of chronic gastric stimulation in morbidly obese individuals. No gastric electrical stimulation devices have received FDA approval for treatment of obesity.

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