Rat Flap Model Research Articles

Involvement of reactive oxygen species in post-ischaemic flap necrosis and its prevention by antioxidants

In attempts to substantiate the possible participation of reactive oxygen species, and the significance of the xanthine oxidase system in both post-ischaemic reperfusion necrosis of the island flap and distal necrosis of the pedicle flap, and to develop new pharmacological measures for salvaging flap necrosis, a series of experiments were made using an island flap model and a random-pattern flap model in rats. The results were as follows: (1) Epoxysuccinyl derivative (E-64c), allopurinol and L-SOD salvaged post-ischaemic reperfusion necrosis of the island flaps; (2) E-64c and allopurinol did not salvage anticipated necrosis of the distal region of random flaps but L-SOD did; (3) tissue SOD activity did not reflect the fate of the island flap, but did of the distal region of the random flap. These results demonstrated a possible involvement of ROS in both post-ischaemic necrosis of island flaps and distal necrosis of random flaps. However, xanthine oxidase was significant in producing ROS only in the former.

The Efficacy of Absorbable Suture for Microvascular Anastomoses

Although microvascular anastomoses are routinely performed with nonabsorbable sutures, a foreign body reaction can be stimulated that acts as a nidus for inflammation, infection, and possible thrombosis. Absorbable sutures should be able to diminish this reaction. There are sparse data describing the use of absorbable sutures for both arterial and venous anastomoses. This investigation compares standard microvascular anastomotic technique using nonabsorbable 10-0 sutures (nylon) with absorbable 10-0 sutures (polyglactin 910), using a previously reported tubed superficial epigastric flap model in rats. Patency rates and histologic responses are compared at intervals of 3 days and 1, 2, 8 and 12 weeks postoperatively. Arterial and venous patency rates were similar for both materials (overall nonabsorbable, 85.9%; overall absorbable, 84.4%). A somewhat increased inflammatory response was noted in the arterial absorbable group at 1 week and in both the venous and arterial nonabsorbable groups at 8 and 12 weeks postoperatively. The later finding most probably represents the continued presence of the nylon sutures. The incidence of intraluminal thrombosis was greater for nonabsorbable suture, occurring in two arterial and four venous anastomoses, compared with only one absorbable suture venous anastomosis. We conclude that nonabsorbable suture is as efficacious as standard absorbable material in both arterial and venous microanastomoses with the potential benefit of diminished foreign body reaction.

Significance of reactive oxygen species in distal flap necrosis and its salvage with liposomal SOD

In an attempt to elucidate whether reactive oxygen species (ROS) have a role in causing distal necrosis of random pattern flaps, and to develop measures to prevent necrosis, three experiments were made using a rat flap model. The flap-salvaging effect of liposomal supperoxide dismutase (L-SOD) was assessed. The results were as follows: (1) Measurements of changes in cutaneous blood flow in a flap, with time, revealed an initial remarkable decrease followed by gradual but significant increase in the distal portion 24 hours after operation. (2) The SOD activity in the flap continued to decrease gradually with time until 24 hours after operation both in L-SOD treated and control groups. However, SOD activity in L-SOD treated flaps was always significantly higher than in the control. (3) S-D value (survival length minus dye distance) was significantly greater in the L-SOD treated flap than in the control flap, indicating a significant effect of L-SOD in preventing the expected flap necrosis. These results suggest a possible role, in causing flap necrosis, of ROS which are generated by reperfusion following ischaemia, and the effectiveness of L-SOD in salvaging distal flap necrosis.

Deferoxamine increases skin flap survival: additional evidence of free radical involvement in ischaemic flap surgery

This study presents further evidence of free radical involvement in skin flap necrosis in a dorsal rat flap model. Rats receiving deferoxamine, a free radical scavenger and iron chelator had significantly less necrosis (p<0.001) than saline treated rats. In a separate experiment, tissue determinations for malonyldialdehyde (MDA) were consistent with the survival results in showing a significant decrease in MDA in all biopsy sites (p<0.05 or less), indicative of reduced lipoperoxidation in the deferoxamine treated rats.

Standardization of the dorsal rat flap model.

In an effort to standardize use of the dorsal rat flap model originally described by McFarlane, we determined the following. The effect of delay is readily demonstrated but does not prevent necrosis entirely. Almost all flaps showed some necrosis, but delayed flaps showed approximately 15% less necrosis. Measurement of surviving flap length is simpler and as reliable as the calculations of flap area. Flap survival shows little change after fifteen days, making longer periods of observation unnecessary. The simplest landmarks for flap length are the scapular tips and the palpable hip joint. No difference in survival is demonstrated by repositioning the flap's base 1 cm caudally. A one-week delay was found to be as effective as a two- or three-week delay. These observations are offered to encourage use of the dorsal rat flap model and to lessen the cost, time, and effort needed for flap research.

A quantitative examination of the use of fluorescein in predicting viability of skin flaps.

The use of fluorescein as a predictor of skin viability in the rat flap model of avascular skin necrosis is well known in the field of plastic surgery. Inherent in this model are several faults that must be corrected if it is to become a valid standard. Fluorescence readings are one of the main variables in flap models. By carefully shaving rat backs with a double-edged razor, taking fluorescence readings in a uniformly darkened space, carefully tattooing the exact extent of both the bright and the mottled areas of fluorescence on the flap, and placing a plastic barrier between the flap and the body to prevent any part of the flap from acting as a graft, we were able to quantitatively predict which portions of a flap would survive and which would die after fourteen days. The bright fluorescent area (mean = 11.99 cm2, SEM +/- 0.53 cm2) is equal to the amount of tissue that will survive (mean = 11.91 cm2, SEM +/- 0.50 cm2; NS), while the sum of the nonfluorescent area and the mottled fluorescent area (mean = 27.69(2), SEM +/- 0.52 cm2) is equal to the amount of tissue that will die (mean = 27.99 cm2, SEM +/- 0.52 cm2; NS).