Human colonic smooth muscle electrical activity during and after recovery from postoperative ileus.

Colon smooth muscle electrical control (ECA) and response activities (ERA) were recorded for up to 4 wk postoperatively for 48 patients after major abdominal operations. Bipolar electrodes were implanted into right and left colon circular muscle and exteriorized through the flanks, and signals were tape recorded for 2-24 h daily beginning on the 1st postoperative day. A computer program was used for data reduction and analysis. Recorded signals were digitized and filtered. The ECA frequency components were identified by fast Fourier transformation, and their relative tenancy in low, mid, and high frequency ranges was determined. Short and long ERA burst duration and frequency and number and velocity of propagating long ERA bursts were determined. ECA was omnipresent and exhibited a downshift of the dominant frequency from the mid to the low range as recovery from postoperative ileus progressed. Concurrently, first in the right and then in the left colon, the frequency of long ERA bursts increased, followed by the appearance of propagating long ERA. After the 6th postoperative day, no further significant changes in parameters of colon electrical activity occurred with time.