Ischemic small intestine-in vivo versus ex vivo bioimpedance measurements.
OBJECTIVE
Bioimpedance has been used to investigate changes in electrical parameters during ischemia in various tissues. The small intestine is a multi-layered structure, with several distinct tissue types, and ischemia related changes occur at different times in the different intestinal layers. When investigating how the electrical properties in the small intestine is affected by ischemia, some researchers have used ex vivo models while others have used in vivo models. In this study, we compare ischemic time development of electrical parameters in ischemic in vivo versus ex vivo small intestine.


METHODS
Measurements were performed using a two-electrode setup, with a Solartron 1260/1294 impedance gain-phase analyser. Electrodes were placed on the surface of ischemic pig jejunum, applying a voltage and measuring the resulting electrical admittance. In each pig, 4 segments of the jejunum were made ischemic by clamping the mesenteric arteries and veins, resulting in a 30 cm central zone of warm ischemia and edema. The in vivo part of the experiment lasted 10 h, after which 3 pieces of perfused small intestine were resected, stored in Ringer-acetat at 38 °C, and measured during a 10 h ex vivo experiment. Main results and significance: We found significant differences (p  <  0.0001) between the values of electric parameters when comparing the in vivo and ex vivo measurements as a function of ischemic time development. We also observed some similarities in the trends. In vivo, we measured an overall decrease in impedance during the duration of the experiment, probably as a result from the formation of edema. Ex vivo, the low frequency impedance increased initially for approximately 3 h before starting to decrease.
Department of Clinical and Biomedical Engineering, Oslo University Hospital-Rikshospitalet, Postboks 4950 Nydalen, 0424 Oslo, Norway. Department of Physics, University of Oslo, Postboks 1048 Blindern, 0316 Oslo, Norway.
Runar J
RJ
Strand-Amundsen
Henrik M
HM
Reims
Christian
C
Tronstad
Håvard
H
Kalvøy
Ørjan G
ØG
Martinsen
Jan O
JO
Høgetveit
Tom E
TE
Ruud
Tor I
TI
Tønnessen
D000818:Animals; D017097:Electric Impedance; D004566:Electrodes; D005260:Female; D007421:Intestine, Small / Q000098:blood supply*; D007511:Ischemia / Q000473:pathology*; D008297:Male; D034421:Sus scrofa