| Objective: To observe influences of different values of negative pressure drainage on blood perfusion, subcutaneous temperature, and oxygen partial pressures under transplanted flaps in the back of rabbits; to provide experimental basis for clinical flap repairmen and enclosed negative pressure drainage during transplantation.Methods: 24 rabbits(3-4 months age) weighting 1.5-2.0kg were randomly divided into 4 groups, including normal pressure group,-80 mm Hg group,-180 mm Hg group and-280 mm Hg group. Except different negative values of pressure drainage, the other treatments were the same among groups. A rectangular pedicle flap(2cm×4cm) was made vertically on a rabbit’s left back. And a small hole was made 1cm below the free end of the rectangular flap. Through the small hole, the plastic tube with scalp intravenous injector was introduced to the area below the pedicle flap, sutured and fixed for negative pressure extraction and pressure measurement by mercury manometer. The pressure changes were monitored. If the pressure was reduced by 5mm Hg, it was re-extracted to certain level of negative pressure. And negative pressure animal models of transplanted flap were established. 20 GA venous indwelling needle were inserted from the flap’s free-end and fixed in the middle of the free flap between the skin and the subcutaneous area. The venous indwelling needle was sutured and fixed and the flap was carefully sutured. The venous indwelling needle was injected with saline to exhaust the air. Detecting probes of Oxy Lite Pro and Oxy Flo Pro instrument were placed to subcutaneous area by venous indwelling needle, to monitor the blood perfusion, temperature and oxygen partial pressure changes under the flaps and to dynamically observe flap’s microcirculation.Results: Blood perfusion of the common pressure group was gradually decreased in the beginning and reached a relatively stable status(300 BPU) around 100 min. There would be a small increase from 240 min and reached 350 BPU at 350 min. From then on, it was reduced and maintained at about 120 BPU from 375 min. Blood perfusion of the-80 mm Hg group was decreased fastest in the beginning and fell to 480 BPU around 60 min and then it was increased to 580 BPU with a small fluctuation. Local blood perfusion on flap wound was continuously maintained at a higher level. Blood perfusion of the-180 mm Hg group was decreased quickly in the beginning, and fell to 390 BPU around 60 min. A small amplitude of increase appeared. It was increased to 420 BPU at 190 min and then fell till 200 BPU. Blood perfusion of the-280 mm Hg group was decreased to 380 BPU at 140 min. It maintained till 270 min and then fell to 120 BPU. There was an obvious curve change of blood perfusion in each of the groups with different pressure values. It showed a tendency of ascending and descending and repeating, with a circle of about 60 min. It was greatly fluctuated. R value was relatively small and the correlation degree was not higher.In both common pressure group and negative pressure group, the flap temperature was decreased at first and increased from 60 min. The temperature was increased to 35.93±0.43 ℃ in the common pressure group, to 37.58±0.23 ℃ in-80 mm Hg group, to 36.62±0.20 ℃ in-180 mm Hg group, and to 35.72±0.44 ℃ in-280 mm Hg group. Temperature change curves of 4 groups were in same trend, all of which were obviously increased. Temperature at each time point after 100 min was obviously higher in-80 mm Hg group than those of the other three groups. The difference was about 5℃ and the difference was significant. There was no significant difference between common pressure group and-280 mm Hg group. For different experimental group, temperatures of local tissue under flap in rabbit were all fluctuated. The amplitude was small, so the correlation coefficient was high, namely R2 was high and the trend was obvious.Oxygen partial pressure in flap of each group was decreased at the beginning to different degrees. In common pressure group, oxygen partial pressure was stable and maintained at about 32 mm Hg at 100 min. It was decreased at 240 min and fell to 10 mm Hg and maintained.-80 mm Hg group is the first group reaching the balance. It took about 60 min. The oxygen partial pressure was maintained at about 32 mm Hg. After small amplitude of descending at 180 min, it was increased to 32 mm Hg again. In-180 mm Hg group, oxygen partial pressure was continued to decline. Oxygen partial pressure was maintained at 18 mm Hg after about 300 min. In-280 mm Hg group, oxygen partial pressure was continued to decline. And it was maintained at 12 mm Hg after about 300 min.Common pressure group and-80 mm Hg group were compared. There were only slight differences in oxygen partial pressure after stability, and small amplitude of fluctuation was appeared. The oxygen partial pressure was decreased in-80 mm Hg group at 180 min, while was decreased in common pressure group at 260 min. The two groups were intersected around 330 min, and the oxygen partial pressure was about 24 mm Hg. In the subsequent common pressure group, oxygen partial pressure was declined till about 10 mm Hg. It was reversal in-80 mm Hg group. The oxygen partial pressure rose to about 32 mm Hg and the difference was significant. The oxygen partial pressure of common pressure group,-180 mm Hg group and-280 mm Hg group were stable and maintained at low levels after stability. And there were significant differences between groups at each time point.It took 19-42 min for oxygen partial pressure of tissue under flap to reach 50 mm Hg in common pressure group, 12-24 min in-80 mm Hg group, 8-11 min in-180 mm Hg group, and 13-14 min in-280 mm Hg group. Then in three groups with negative pressure drainage under flap, time for local oxygen partial pressure on wound reaching stable and maintaining below 50 mm Hg was significantly lower than the common pressure group. Rank-sum inspection result was P<0.05 in total comparison, suggesting statistical significance.Correlation coefficients of local tissue oxygen partial pressure on flap wound and blood flow perfusion were 0.389, 0.402, 0.255 and 0.506 in common pressure group,-80 mm Hg group,-180 mm Hg group and-280 mm Hg group. P < 0.001 showed statistically significant differences.Experimental results indicated that microcirculation perfusion of flap was recovered fastest in-80 mm Hg group. Average temperature was highest in-80 mm Hg group. The temperature was fastest in increase and the amplitude was highest, promoting local tissue metabolism was the most robust in-80 mm Hg group. Average oxygen partial pressure was the highest in-80 mm Hg group. And with the extension of the time, the oxygen partial pressure rose progressively, promoting the most abundant oxygen in-80 mm Hg group. Conclusion: Certain degree of sealed negative pressure drainage can quickly remove the subcutaneous air produced in flap suture, make continuous drainage and hematocele under drainage flap, and increase blood flow and oxygen partial pressure of transplanted flap and local metabolism, which is conducive to living of flap. An excessive negative pressure can easily cause both hypoxia and ischemia of tissue, which is not good for metabolism of tissue cells and may influence the living and healing of flap. The best pressure value for enclosed negative pressure drainage of flap in rabbit back was-80 mm Hg. |
PDF Full Text Request