Gastrointestinal application of laser Doppler flowmetry. An experimental and clinical study in cat and man

Laser Doppler flowmetry (LDF) was evaluated as a method for study of gastrointestinal blood flow with emphasis on clinical applicability in man. Measuring depth of LDF in the gastrointestinal tract was studied in cat and man. The LD-signal was attenuated in an exponential manner by unperfused intestinal tissue between the probe and the perfused organ. With a probe with optical fibre diameter of 0.7 mm, the measuring depth was approximately 6 mm i.e. transmural in most parts of the gastrointestinal tract. In experimental mesenteric vascular occlusion on feline small intestine, it was possible to discriminate arterial and venous occlusion by simultaneous recording of the total amount of backscattered light. The effect of epidural anaesthesia on intestinal blood flow was studied in 15 patients during large bowel resections. A significant increase of total blood flow was found in the colon (p less than 0.01) and the small intestine (p less than 0.05), with an average increase of 41% and 15% respectively. LDF was used intraoperatively for assessment of the extent and degree of disturbed microcirculation in 8 patients with late radiation injury of the gastrointestinal tract. The flow values obtained were compared with reference values earlier obtained in unaffected tissue from corresponding gastrointestinal sites. Severe reduction of blood flow was demonstrated in segments with visible fibrosis. Five segments also showed varying degrees of disturbed blood flow in adjacent macroscopically normal bowel with histological radiation injury. In patients with radiation injury of the rectum, it was possible to assess the extent of vascular damage in the rectum prior to surgery by endoscopic flowmeter recording. The post-operative course was uneventful in all patients. In 23 patients with small bowel ischemia of different origins, LDF proved valuable for assessment of blood flow and tissue viability. In patients with mechanical strangulation, bowel resection was avoided in 9 out of 10 segments of clinically uncertain viability following flowmeter recording. In 6 patients with mesenteric vascular occlusion, the extent of severe ischemia seemed underestimated by clinical judgement compared to the results obtained with LDF. The ability of LDF to detect small ischemic areas and to select the proper level of resection was demonstrated. It is concluded that LDF is a suitable method for study of gastrointestinal blood flow in experimental and clinical work. LDF provides substantial information in the intraoperative management of small bowel ischemia and late radiation injury of the gastrointestinal tract.