Laser Doppler velocimetry and the measurement of colostomy blood flow

Intraoperative assessment of colonic perfusion using scanning laser Doppler flowmetry during colonic resection

BACKGROUND

Ischemia occurring on mobilization and mesenteric division is thought to be a major factor in the etiology of anastomotic dehiscence after colorectal resection. This study assessed the ability of the new technique of scanning laser Doppler flowmetry to measure changes in human colonic perfusion during mobilization at and adjacent to the anastomotic site.

STUDY DESIGN

Colonic perfusion was measured in 10 patients undergoing large-bowel resection by making laser Doppler scans of the proximal bowel before mobilization, after mobilization and mesenteric division, and after resection of the specimen. Mean perfusion was calculated within 1-cm2 regions of interest, each of which contained 1,750 individual measurements of perfusion. These regions represented the anastomosis site and adjacent areas 1 cm and 2 cm proximal and distal to this. The results were expressed as mean perfusion units (PUs).

RESULTS

After mobilization, there were significant decreases in perfusion in all the subjects between each time point and in all areas of the colon scanned. Median perfusion at the anastomosis site was 491 PUs before mobilization, and this fell to 212 PUs after mobilization, representing a decrease of 57%; the median within-person decrease was also 57% (p < 0.01). There was a gradient of reduced perfusion between the area 2 cm proximal to the mesenteric division (median within-person fall 25%; p < 0.05) and the area 2 cm distal to the mesenteric division (median within-person fall 84%; p < 0.01). After resection of the specimen, perfusion increased slightly at the anastomosis site to a median of 240 PUs (median within-person fall 41%; p < 0.01), but 2 cm proximal to this, median perfusion remained depressed at 330 PUs.

CONCLUSIONS

This new technique can be used intraoperatively and appears to overcome the limitations of single-point laser Doppler flowmetry. In this small preliminary study, it measured large decreases in colonic perfusion during mobilization, and it may have widespread clinical applications.

Complications of abdominal stoma surgery

PURPOSE

This study was undertaken to review and summarize the complications of ileostomy and colostomy creation and subsequent closure.

METHODS

The English-language medical literature for at least the past 15 years was reviewed comprehensively.

RESULTS

Complications of surgery for the creation of end, loop, and "end loop" stomas are presented. Technical factors, which might influence complication rates, are discussed. Optimal management of ostomy complications is presented, especially for peristomal hernias. Similarly, techniques and complications for stoma closure are analyzed.

CONCLUSIONS

Stoma creation is not a trivial undertaking; careful surgical technique minimizes complications (which are relatively frequent), and promotes good ostomy function. Peristomal hernias are difficult to cure permanently. The morbidity of ileostomy and colostomy closure is also appreciable.

Non-invasive measurement of colonic blood flow distribution using laser Doppler imaging

BACKGROUND

This study tested a prototype laser Doppler scanner for the measurement of human colonic blood flow.

METHODS

Blood flow distribution was assessed in human colon during operation in six controls and in six patients with inflammatory bowel disease undergoing colectomy. Image processing software analysed several hundred reading points, expressing average flow in perfusion units.

RESULTS

Blood flow in the colon was not significantly lower in the control group than in patients with inflammatory bowel disease (mean(s.e.m.) 297.8(24.5) versus 347.2(59.0) perfusion units, P = 0.12). Intestinal colonic mural blood supply was demonstrated up to a distance of 6 cm and ischaemia demarcation lines were identified before the onset of visible changes.

CONCLUSIONS

This prototype laser Doppler flowscanner overcomes the previous limitations of laser Doppler flowmeters and may have many clinical and research applications.

The significance of probe design in evaluation of colonic perfusion with laser Doppler flowmetry

The significance of probe design for laser Doppler flowmetry measurement depth and variation was investigated by determining flux versus pressure relations and spatial variability with various probes placed on the serosal surface of porcine sigmoid colon. For two large probes (three optical fibers with diameter and center separation > or = 500 microns) the flux versus pressure relations showed autoregulation, indicating that the mucosal perfusion contributed to the flux signal. The curves were reproducible between individuals. With two smaller probes linear flux versus pressure relations were obtained, indicating a shallow measurement not influenced by the autoregulated mucosal perfusion. The spatial variation expressed as coefficients of variation of repeated recordings at each pressure level was significantly greater with the smaller probes (p < 0.001). For clinical use the larger probes should be preferred. These include all wall layers, and only 3 repeated recordings are needed to obtain a reproducible mean flux value within +/- 10%, as opposed to 10 with the smaller probes.