Anne Quirinia

THE EFFECT OF RECOMBINANT BASIC FIBROBLAST GROWTH FACTOR (bFGF) IN FIBRIN ADHESIVE VEHICLE ON THE HEALING OF ISCHAEMIC AND NORMAL INCISIONAL SKIN WOUNDS

Normal and ischaemic incisional wounds in rats were treated with recombinant human basic fibroblast growth factor (rbFGF) in fibrin adhesive vehicle. After 10 days of healing the maximum load*S and stress*S (S denotes correction for shrinkage) of ischaemic wounds were increased by 45% and 39%, respectively, after treatment with 20 micrograms rbFGF and by 67% and 56% after treatment with 60 micrograms rbFGF. After 20 days only 20 micrograms rbFGF had any effect and increased maximum load*S by 31% and energy at maximum (load*S, stress*S) by 40%-48%. In normal wounds 0.6-20 micrograms and 60 micrograms rbFGF decreased the strength parameters by 19%-34% and 49%-52%, respectively, after 10 days. After 20 days there was no negative influence but 60 micrograms rbFGF increased the biomechanical properties by 15%-24%. Treatment with the fibrin adhesive vehicle alone decreased the biomechanical properties of ischaemic wounds after 20 days, and of normal wounds after both 10 and 20 days. In conclusion, rbFGF can improve the healing of ischaemic wounds and may be used in the treatment of ischaemic wounds in patients, but it can have negative effects on normal wound healing.

Ischemia in Wound Healing I: Design of a Flap Model—Changes in Blood Flow

A standardized ischemic, H-shaped, double flap model in rats was developed for investigating the influence of different factors that could potentially increase flap survival. The blood flow was measured in the flaps as well as in normal healing incisional wounds on day -1 (intact skin) and on days 1, 4, 8, and 16 by the xenon-133 (133Xe) clearance technique. The flow in normal healing incisional wounds remained the same as the flow in intact skin. The flow in the flaps, however, initially decreased to ischemic levels, but afterwards gradually increased to that of normal healing incisional wounds and intact skin. Further, the cutaneous blood flow in both the cranially and the caudally based ischemic dorsal flap was independent of the width of the flap.

Ischemia in Wound Healing II: Design of a Flap Model—Biomechanical Properties

A standardized reproducible H-shaped double flap model for biomechanical testing of ischemic wounds was developed in rats. After 10 days of healing all the biomechanical parameters of the flap wounds decreased significantly, compared with normal healing incisional wounds. After 20 days of healing the extensibility as well as the most important biomechanical parameters were still significantly decreased. In part I of this study we showed that on day 1 the blood flow had decreased to 7% of the flow in normal incisional wounds, though it returned to normal on day 16. Here we show that this drop in blood flow results in a significant decrease in all the biomechanical parameters and thereby caused significant delay in the healing of the test wounds. There was no correlation between any of the biomechanical parameters and the length of surface necrosis on the flaps. These necroses thus do not necessarily reflect necrosis of the dermis, where the healing is responsible for the continuity and strength of the skin.

Diclofenac and indomethacin influence the healing of normal and ischaemic incisional wounds in skin

The influence of diclofenac and indomethacin on the healing of normal (non-ischaemic) incisional wounds, and of ischaemic incisional wounds using a flap model, was studied in 192 rats. Both drugs improved the strength of normal wounds as the energies at maximum load and stress increased by 23% - 33% after 10 days. After 20 days the treated normal wounds were stiffer. In ischaemic wounds neither drug influenced the biomechanical properties after 10 days, which reflects the healing of the deep dermis, but both countered the ischaemia of the superficial skin as the necroses on the skin flaps decreased. After 20 days the drugs decreased some of the strength parameters of ischaemic wounds, indomethacin in particular, which decreased these parameters by about 20% - 35%. In conclusion, in certain doses the drugs improved the healing of normal wounds. The healing of ischaemic wounds was unaffected after 10 days but decreased after 20 days. The drugs may, however, be used for reducing superficial necroses of skin flaps.

Freezing for postmortal storage influences the biomechanical properties of linear skin wounds

Specimens for biomechanical investigations are often stored frozen between sampling and testing. Several authors have analysed the effects of freezing on a variety of intact tissues; while some have found mostly minor changes, others have reported no adverse effects. Healing wounds contain more fragile tissue components than other tissues and are therefore more sensitive to possible adverse effects. This study on rat skin wounds (healed for 10 and 20 days) demonstrates that freezing has a significant adverse influence on the mechanical properties. It is concluded that fresh tissue should be used whenever possible. In case storage in a freezer is necessary great care should be taken when designing the experimental protocol.

The impact of ischemia on wound healing is increased in old age but can be countered by hyperbaric oxygen therapy.

The healing of normal incisional wounds and ischemic flap wounds was investigated in young (10 weeks) and old (102-104 weeks) rats, together with the effect of treatment with hyperbaric oxygen on day 0-3 of healing. After 10 days of healing all biomechanical strength parameters of normal wounds were decreased by 30-40% and of ischemic wounds by 40-51% in the old animals compared with the young controls. After 20 days all strength parameters of normal wounds and ischemic wounds were decreased by 29-37% and 46-58%, respectively, in the old rats compared with those of the young ones. Treatment with hyperbaric oxygen of ischemic wounds in old animals increased all strength parameters by 36-50% after 10 days and by 67-88% after 20 days. For young animals, the corresponding increase was only 21-35% after 10 days and no effect was seen after 20 days. The shrinkage of ischemic wounds was decreased by 48% in the old animals compared with the young ones. It can be concluded that ischemia intensifies the impairment of the healing seen in old age. On the other hand, treatment of ischemia with hyperbaric oxygen is much more effective in old animals, despite the fact that it also has a pronounced effect in young animals. Furthermore, the results suggest a decreased wound contraction with age.

Failure of Buflomedil to Improve Wound Healing in Ischaemic Skin Flaps

The effect of buflomedil and isoxsuprine on the healing of ischaemic wounds was investigated using an ischaemic flap model previously evaluated on rats. The drugs were given twice daily intraperitoneally for a total of nine days starting on the day before operation. The wounds were tested biomechanically after 10 and 20 days of healing, respectively, and the length of surface necrosis on the flaps was measured after 10 days. The study showed no differences in any of the biomechanical (functional) parameters of the ischaemic wounds compared with the control groups, either after 10 or 20 days of healing. There were no differences in the length of surface necrosis on the flaps. Neither of these drugs has so far convincingly proved to be effective in the treatment of ischaemic wounds or flaps.

THE INFLUENCE OF OCCLUSIVE DRESSING AND HYPERBARIC OXYGEN ON FLAP SURVIVAL AND THE HEALING OF ISCHAEMIC WOUNDS

The effect of dressing with Duoderm (hydrocolloid) and treatment with hyperbaric oxygen was investigated on the healing of ischaemic incisional wounds and on flap survival in rats. After 10 days, Duoderm dressing of ischaemic wounds decreased all strength parameters (load*S, stress*S) by 41%-44% and the improvement of ischaemic wound healing by hyperbaric oxygen treatment shown in our previous study was not seen. After removal of Duoderm on day 10 the biomechanical properties had improved but not returned to normal on day 20. In the dressed animals the shrinkage of ischaemic wounds and the extension of necrosis on the ischaemic flaps were reduced. Dressing may be useful clinically in preventing superficial dermal necroses. One must, however, be aware of the impairment of the wound strength of the incisional wounds.

THE INFLUENCE OF DRESSINGS ON THE HEALING OF NORMAL AND ISCHAEMIC WOUNDS AND FLAP SURVIVAL

The effects of dressing with Duoderm (occlusive hydrocolloid) and Mepore (permeable viscose) on the healing of normal and ischaemic incisional wounds, and on flap survival, were investigated in 60 rats. The biomechanical properties of dressed normal wounds after 14 days did not differ from those of the undressed controls. In contrast, energies at maximum and breaking (load*S, stress*S) of dressed ischaemic wounds decreased by 30%-42% after 14 days of healing, compared with undressed ischaemic controls. Dressing decreased the shrinkage of ischaemic wounds and necrosis length of ischaemic flaps. Normal incisional wounds can safely be dressed for 14 days without the wound strength being affected. Dressings may be useful clinically in preventing superficial dermal necroses. One must, however, be aware of the impairment of the wound strength of ischaemic incisional wounds.

Effect of delayed primary closure on the healing of ischemic wounds.

OBJECTIVE To study the influence of delayed primary closure on the healing of ischemic wounds in rats. METHODS Wounds sutured after a delay of 3 days were compared with primary closed wounds by biomechanical testing. RESULTS The delayed wounds were as strong as primary closed wounds when tested 10 days after wounding. Thirteen days after wounding (10 days after closure), nearly all the biomechanical parameters of the delayed wounds were increased, compared with those of primary closed wounds that had healed for 10 days. The wounds closed after a delay were weaker, however, when tested 20 days after wounding. CONCLUSION An ischemic wound can safely be left open for 3 days before suturing, i.e., for prevention of infection in contaminated wounds, without affecting the biomechanical properties at the time of removing the sutures, which is often performed clinically 10 to 12 days after the operation.