Microprocessor controlled movement of solid colonic content using sequential neural electrical stimulation

Abstract

Background and aims: Invoked peristaltic contractions and movement of solid content have not been attempted in normal canine colon. The purpose of this study was to determine if movement of solid content through the colon could be produced by microprocessor controlled sequential stimulation.

Methods: The study was performed on six anaesthetised dogs. At laparotomy, a 15 cm segment of descending colon was selected, the proximal end closed with a purse string suture, and the distal end opened into a collecting container. Four sets of subserosal stimulating electrodes were implanted at 3 cm intervals. The segment of bowel was filled with a mixture of dog food and 50 plastic pellets before each of 2-5 random sessions of non-stimulated or stimulated emptying. Propagated contractions were generated using microprocessor controlled bipolar trains of 50 Hz rectangular voltage having 20 V (peak to peak) amplitude, 18 second stimulus duration, and a nine second phase lag between stimulation trains in sequential electrode sets.

Results: Electrical stimulation using the above mentioned parameters resulted in powerful phasic contractions that closed the lumen. By phase locking the stimulation voltage between adjacent sets of electrodes, propagated contractions could be produced in an aboral or orad direction. The number of evacuated pellets during the stimulation sessions was significantly higher than during the non-stimulated sessions (p<0.01).

Conclusions: Microprocessor controlled electrical stimulation accelerated movement of colonic content suggesting the possibility of future implantable colonic stimulators.

Figure 1

Schematic diagram of the implantation of four sets of longitudinal subserosal electrodes (15×0.25 mm) at 3 cm intervals. The electrode sets were attached to a multichannel stimulator controlled by specially designed software on a personal computer. A 15 cm segment of descending colon was filled with 40–50 ml of viscous material plus 50 pellets through a transversal opening made 2.0 cm proximal to the first set of electrodes and maintained closed with a purse string suture. The colon was transected 2.5 cm distal to the last set of electrodes. The resulting distal stoma was positioned in a metallic dish to collect eventual emptied material during stimulation and non-stimulation sessions.

Figure 2

Time characteristics of the stimuli applied to the electrode sets that produced aboral propagation of contractions (starting with the most proximal pair).

Figure 3

Time characteristics of the stimuli applied to the electrode sets that produced orad propagation of contractions (starting with the most distal pair).