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Biomedical subjects

R H Lowndes

Publications and source records attributed to R H Lowndes.

11 recordsLinked to original sources
PubMed1995

High tie of the inferior mesenteric artery in distal colorectal resections--a safe vascular procedure.

Division of the inferior mesenteric artery flush with the aorta (high tie) allows a tension-free anastomosis in distal colorectal resections but may also diminish the blood supply. Tissue oxygen tension was measured proximal to the resection margin before and after either low or high division of the inferior mesenteric artery in 62 patients undergoing elective colorectal resections. Oxygenation was maintained or improved when the transverse (median change after vs before resection for low tie +9 mmHg (P < 0.05), high tie +8 mmHg (P = 0.3)) and descending colon (low tie +7 mmHg (p < 0.01), high tie +1 mmHg (p = 0.67)) were used for the anastomosis but diminished for sigmoid anastomoses (low tie -4 mmHg (P = 0.42), high tie -9 mmHg (P < 0.05)). Change in oxygenation was significantly affected by location of proximal resection site but not by choice of high or low tie. These results suggest that the marginal artery provides a more than adequate vascular supply to the transverse and descending colon, but that the sigmoid colon is not suitable for anastomosis. We conclude that the sigmoid colon be sacrificed and there should be no hesitation in performing a high tie to avoid tension in low pelvic anastomoses.

Aged↗
PubMed1994

Anorectal physiological testing in defecatory disorders: a prospective study.

A prospective study of anorectal physiological testing in 26 patients with obstructed defecation and 20 patients with faecal incontinence was performed. There were overlaps in individual test parameters between the two groups of patients. However, patients with severely blunted rectal sensation (maximum tolerated volume > 300 mL) and anismus were more likely to have obstructed defecation. Patients with very low anal canal pressures, a short (< 2.0 cm) anal canal, bilaterally prolonged (> 2.1 ms) pudendal nerve terminal motor latency and a grossly distorted and canal (vector symmetry index < or = to 0.75) were more likely to have faecal incontinence. Thus, patterns of anorectal physiological test results together with clinical evaluation, rather than individual test measurements, are more valuable in defining the underlying defecatory disorders and providing guidance on therapy.

Adult↗
PubMed1992

Determination of a critical level of tissue oxygenation in acute intestinal ischaemia.

Tissue oxygen tension (PtO2) was measured using a miniaturised polarographic oxygen electrode in 134 segments of rat small intestine of varying degrees of ischaemia. Without knowledge of the PtO2 levels, the viability of each segment was scored using clinical parameters and tissue damage scored by independent histological examination. Histologically non-viable bowel had significantly impaired tissue oxygenation when compared with viable bowel (t test, p less than 0.001). Marked degrees of tissue hypoxia were frequently tolerated before major histological damage became apparent, a critical PtO2 level of 1.9 mmHg being identified. The overall accuracy rate of PtO2 measurement in the operative prediction of intestinal viability was 92.5%, which contrasts with a rate of only 57.7% for clinical criteria alone.

Animals↗
PubMed1991

Oxygenation in the stomach and the effect of truncal vagotomy.

A Clark polarographic oxygen electrode allowed detailed mapping of tissue oxygen (PtO2) levels on the anterior surface of the stomach in five patients undergoing cholecystectomy. No significant difference in mean PtO2 was detectable between greater and lesser curvatures. A significant difference in mean PtO2 was detected between the body of the stomach and the pylorus (Mann-Whitney, P less than 0.01). The effect of truncal vagotomy on PtO2 was evaluated in six patients undergoing this procedure for duodenal ulceration. Mean postvagotomy stomach PtO2 levels (46 +/- 12 mmHg) were significantly lower (Wilcoxon test, P less than 0.001) than prevagotomy levels (59 +/- 14 mmHg). Truncal vagotomy did not have any significant effect on small intestinal PtO2. This work provides the first objective evidence of the relatively diminished tissue oxygenation in the gastric antrum and pyloric region, and confirms blood flow studies of the effects of vagotomy.

Adult↗
PubMed1990

Intraoperative tissue oximetry in the human gastrointestinal tract.

Tissue oxygen tension was measured using a modified Clark oxygen electrode in the gastrointestinal tract of 33 patients undergoing laparatomy. The electrode, which incorporated a thermistor, had a linear response to oxygen tension (r = 0.995, p less than 0.001). The patients were all maintained on an inspired oxygen concentration of 33 +/- 3% and had a mean arterial oxygen tension (PaO2) of 124.9 +/- 31.9 mm Hg. Tissue oxygen tension measurements (mm Hg, mean +/- SD) were recorded from the serosal surfaces of the stomach (46.3 +/- 15.4), mid-ileum (36 +/- 9.7), terminal ileum (33.5 +/- 11.5), cecum (30.3 +/- 7.4), transverse colon (38.5 +/- 10), descending colon (29.3 +/- 11), and sigmoid colon (39.2 +/- 7.7) and tended to increase with increasing PaO2 (r = 0.70, p less than 0.001). Arterial occlusion resulted in a gradual decrease in tissue oxygen tension. It is concluded that intraoperative tissue oxygen tension measurement is feasible, and that the technique may have clinical applications in the assessment of intestinal viability.

Adult↗
PubMed1987

Tissue oxygen tension as a predictor of colonic anastomotic healing.

Inadequate blood flow causing tissue hypoxia can result in failure of anastomotic healing. Tissue oxygen tension (ptO2) measurement has been used to predict anastomotic leakage in animals, but its use in humans has not been described previously. A Clark-type oxygen electrode was used to measure ptO2 on the colon of 50 patients undergoing colonic resection and anastomosis. Baseline ptO2 levels were lowest on the descending colon (31.8 +/- 7.4 mmHg, mean +/- SD) and tended to increase at all sites with increasing arterial paO2 (r greater than .76, P less than .001). Perianastomotic ptO2 levels were predictive of subsequent anastomotic leakage when they were less than either 20 mmHg; 50 percent of the preresection ptO2; 15 percent of the arterial paO2; or 40 percent of the ptO2 at a control site (ileum). It is concluded that perioperative ptO2 measurements are of value in the prediction of anastomotic leakage.

Adult↗
PubMed1986

A versatile light microscope heating stage for biological temperatures.

A light microscope heating stage suitable for biological temperatures is described. A novel feature of the design is the use of cupro-nickel foil heaters (0.1 mm thick). With a temperature sensor mounted on the slide clip and a temperature controller unit, this apparatus maintains a temperature of 310 K with a precision of 0.1 K. The apparatus is inexpensive, reliable, not confined to use with one microscope and does not interfere significantly with the stage movement or optical alignment.

Hot Temperature↗