Biomedical subjects

D H Stewart

Publications and source records attributed to D H Stewart.

14 recordsLinked to original sources

PubMed1992

Is reversed venous flow safe in free-flap transfer? A dilemma with the radial forearm flap.

The distally based radial artery forearm flap has become our workhorse flap for hand and finger coverage, relying on reversed or retrograde venous outflow through the venae comitantes. Free-flap transfer, however, has been used by us only with antegrade venous anastomoses. This study was intended to determine if a single retrograde venous anastomosis would be adequate for flap viability. Six groups of saphenous flaps were developed in New Zealand White rabbits. In situ flaps compared antegrade with retrograde venous outflow in groups 1 and 2. Microvascular venous anastomoses with antegrade or retrograde outflow were compared in groups 3 and 4. Free-flap transfer with antegrade or retrograde venous outflow was compared in groups 5 and 6. No significant differences in survival was found between groups 1 and 2. A significant difference in survival (p = 0.025) was found between groups 3 and 4, but technical differences make these groups incomparable. Significantly better survival (p = 0.014, chi-squared test) was found in group 5 with antegrade outflow versus group 6 with retrograde outflow.

Animals↗

PubMed1991

Abnormal scleral collagen in nanophthalmos. An ultrastructural study.

Ten patients with bilateral nanophthalmos underwent sclerectomies for uveal effusion. Ultrastructural examination of the sclera revealed abnormal collagen in seven patients. Four showed dramatic fraying of the collagen fibrils into fine filaments 2 to 3 nm in diameter. In three of these cases and three other cases without fraying, there were foci of 10- to 35-nm small collagen fibrils, some appearing to arise by splitting of otherwise normal collagen fibrils. In areas of fraying, elastic fibers were absent. All patients had a wider range of collagen diameters than did control subjects. The youngest patient with fraying also had Hallermann-Streiff syndrome. In three patients, no collagen abnormality was found. The clinical feature correlating best with the presence of abnormal collagen was an extremely small eye, since the three patients without collagen abnormality had the largest eyes (range of anteroposterior diameters, 19.2 to 20.3 mm). Nanophthalmos appears to result from several distinct defects.

Adult↗

PubMed1991

Impedance plethysmography: a new method for continuous muscle perfusion monitoring.

Vigilant postoperative monitoring of the buried muscle flap is critical after free transfer because early diagnosis of vascular insufficiency is essential to allow prompt correction. We have identified a monitoring method utilizing needle electrodes and impedance plethysmography that gives a beat-to-beat representation of muscular perfusion. In 25 New Zealand White rabbits the gastrocnemius muscle was isolated on its vascular pedicle, and two intramuscular needle electrodes were placed. The instantaneous impedance changes of the muscle (corresponding to the pulsatile volume changes of perfusion) were measured and recorded. Using this representation of perfusion, an independent judge was able to correctly diagnose muscular ischemia 100 percent of the time (n = 25). Further, the judge was able to correctly distinguish the ischemia as arterial (n = 10) or venous (n = 10) in origin 100 percent of the time. Additionally, we monitored muscle perfusion transcutaneously in five free muscle flaps and demonstrated a reliable impedance signal that correlated with perfusion.

Animals↗

PubMed1979