Laser Doppler measurement of rectal mucosal blood flow

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Abstract
BACKGROUND Gut mucosal blood flow measurement is used to study a variety of disorders and possibly extrinsic neural function. AIMS To determine optimal measurement criteria and validate this technique as a measure of level of activity of extrinsic autonomic gut innervation. METHODS In 26 healthy volunteers a laser Doppler mucosal probe was applied 10 cm from the anus. Response to inhaled salbutamol 200 μg and ipratropium 40 μg, intravenous metoprolol 2.5 mg, and direct sacral nerve electrostimulation (in nine incontinent patients) was also studied. RESULTS The coefficient of variation for subjects studied under identical conditions on two, three, and four days was 0.06, 0.05, and 0.06, respectively. Mean mucosal blood flow increased after a standard meal. Blood flow decreased for 15 minutes after smoking and returned to baseline at 30 minutes. Fasted measurements at 0900, 1200, 1600, and 2200 were similar. There was a negative correlation between blood flow and body size but not age. Follicular phase mucosal flow was less and more reproducible than luteal. Mucosal blood flow was highest in men and lowest in postmenopausal women. Inhaled salbutamol did not change blood flow; ipratropium significantly reduced, and metoprolol and sacral nerve stimulation increased flow. CONCLUSIONS Measurement of gut mucosal blood flow by laser Doppler flowmetry is highly reproducible. Eating, smoking, body size, sex, ovulatory status, and menstrual phase influence blood flow. Changes in mucosal blood flow induced by autonomically active drugs and nerve stimulation confirm the role of the mucosal microcirculation as a measure of extrinsic nerve activity.