Effect of phentolamine and propranolol on the survival of experimental skin flaps

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.

Role of noradrenaline in the pathogenesis of skin flap ischemic necrosis in the pig

Clinically, ischemic necrosis is one of the most common complications in skin flap surgery, but the etiology is still unclear. The objective of the present experiments was to study the important role of the locally released noradrenaline in the pathogenesis of ischemic necrosis in acute and delayed random pattern skin flaps (4 x 10 cm) raised on both flanks of the pig. In Experiment 1, it was observed that 93, 96, and 94% of the skin contents of noradrenaline were depleted in skin flaps delayed for 2, 4, and 14 days, respectively, compared to the acute skin flaps (n = 8) raised in the same pig. Although the maximum depletion of noradrenaline in the delayed flaps occurred within 2 days of delay, significant (P less than 0.001) increase in the length of dye penetration in the delayed skin flaps was seen after 2 days of delay, compared to the acute skin flaps (n = 12). In Experiments 2 and 3, 5 days of intravenous phenoxybenzamine treatment, starting 2 days preoperatively and at the doses of 0.25, 0.5, 1.0, or 1.5 mg/kg/day, did not have any significant effect on the skin blood flow (n = 24) or viability (1 mg/kg/day; n = 32) in the acute skin flaps compared with the saline-treated control. Similarly, 5 days of intravenous phentolamine treatment (5 mg/kg/day) also did not have any significant effect on the skin blood flow (n = 24) or viability (n = 32) of acute skin flaps compared with the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of electrical nerve stimulation (ENS) in ischemic tissue

Blood flow was measured in the skin flaps of 20 patients who had undergone reconstructive surgery. All flaps were showing clinical signs of deficient circulation. Local blood flow in skin flaps was significantly increased by electrical nerve stimulation (ENS) (p less than 0.001), but not by placebo ENS. Repeated ENS treatment reduced stasis and oedema significantly (p less than 0.001), and the capillary refill was also significantly improved (p less than 0.001).

Increased survival of ischaemic musculocutaneous flaps in rats after acupuncture

The effects of acupuncture on survival of ischaemic musculocutaneous flaps were investigated in the rat. A dorsal cranially based standard flap (2 X 7 cm) was elevated and sutured back in position. The percentage survival of the flaps was estimated after 6 days. Manual acupuncture, electro-acupuncture but not superficial acupuncture significantly increased the survival of the flaps compared to untreated controls. The highest flap survival (92%) was obtained with repeated post-operative high-intensity electro-acupuncture. It is concluded that acupuncture treatment markedly increases experimental flap survival and may be of clinical importance for treatment of local ischaemia.

The anatomy and histology of the cranially based dorsal musculocutaneous flap of the rat

The cranially based dorsal musculocutaneous flap of the rat is commonly used to study the effects of various pharmacological compounds of flap survival. In the present study the anatomy and histology of the flap are described. It is shown that the central vessel of the flap is a vein and that this vein can be used for injection of substances into the capillary network of the flap. The sensory innervation of the flap is studied using indirect immunohistochemical technique.

Degeneration release of noradrenaline in skin flaps in rats

To study if noradrenaline released from degenerating sympathetic nerves may contribute to metabolic stimulation and low blood flow in an experimental skin flap, we have determined noradrenaline levels in such skin flaps. Attempts to use radioenzymatic methodology for the determination of noradrenaline in rat skin extracts were unsuccessful due to interference with the assay. High performance liquid chromatography with electrochemical detection was, however, found to give accurate estimates of rat skin noradrenaline contents. Rat skin contained approximately 2.7 nmol (455 ng) noradrenaline per gram dry weight. Extensive depletion of skin flap noradrenaline, occurring mainly between 6 and 24 h postoperatively, was found. At 48 h nearly all sympathetic nerves in the skin flaps had degenerated as evidenced by noradrenaline levels of 0.13 nmol/g. The degeneration of sympathetic nerve endings appears to proceed from the sides towards the middle of the flap, indicating a segmental distribution of the nerves. Noradrenaline released from degenerating sympathetic nerves may adversely affect the survival of critical skin flaps by causing vasoconstriction and metabolic stimulation.

Isoxsuprine and the rat abdominal pedicle flap: a controlled study

In a controlled study of the rat abdominal pedicle flap the area of flap necrosis was not reduced by a course of treatment with isoxsuprine. Animals receiving placebo injections of saline showed significantly less flap necrosis than those treated with the drug.

Early changes in ATP and cyclic AMP levels in experimental critical skin flaps

A cranially based pedicle skin flap, 2 cm wide and 7 cm long, was prepared in the midline of the rat dorsum. The contents of ATP and cyclic AMP were determined in the proximal, middle and distal parts of the flap. The basal level of ATP was 1.3 +/- 0.1 nmol/g dry weight. Following the operation the level of ATP fell rapidly. The fall was more marked in those parts of the flap that eventually do not survive. During the first 12 h the level of cyclic AMP fell at least as rapidly. However, thereafter the cyclic AMP level remained constant or even increased while the ATP showed a further decrease. It is suggested that the rapid fall in ATP may be used to assess the eventual survival of skin flap. The results are also compatible with the opinion that a period of metabolic stimulation in the skin flap starts 12--18 h after operation, i.e. at the time when the adrenergic nerves in the flap degenerate.

The assessment and enhancement of skin flap viability

One of the most difficult tasks facing the reconstructive surgeon is the successful transfer of skin flaps. Despite recent dramatic advances in the application of skin flaps and despite the skill and experience of the surgeon, flaps still fail. This review discusses the methods regarded as most accurate in assessing skin flap viability, and the techniques used to augment flap survival.

Effect of different types of anaesthesia including percutaneous local anaesthesia on survival of experimental skin flaps

Local anaesthesia by epicutaneous application of the ketocaine solution A2358 gave survival of experimental skin flaps in the guinea pig which corresponded on average to 71% of the total flap. The survival after pentobarbitone anaesthesia, general anaesthesia with ether, and infiltration of prilocaine without and with adrenalin varied between 41 and 53%. The difference in effect between percutaneous anaesthesia with A2358 and the other procedures was statistically significant (p less than 0.001). Epicutaneous application of A2358 followed by one of the other forms of anaesthesia gave a flap survival that did not differ from that following local anaesthesia with A2358 alone, except when followed by injection of prilocaine with adrenalin. The improved survival after epicutaneously applied A2358 is probably attributable to an effect on the peripheral vascular bed resulting in increasing blood supply and nutrition. It may be possible that A2358, for example, could be used in man as a complement to other forms of anaesthesia to provide enhanced tissue survival in skin flaps.

Increased survival of experimental skin flaps in rats following treatment with antiadrenergic drugs

The effect upon the survival of skin flaps of several drugs which affect the adrenergic system was studied in rats. In control animals 41% of the skin flaps had survived seven days after the operation. Reserpine (1 mg/kg) injected intraperitoneally (i.p.) three days and one day before the flap operation increased the surviving flap area by 75% (p less than 0.001) as compared to control rats injected with saline. I.p. injection of guanethidine (5 mg/kg) or bretylium (10 mg/kg) every 12 hours, starting 24 hours before surgery and continued for 5 consecutive days, also increased the surviving flap area (19 and 33% respectively p less than 0.001). The surviving flap area was unchanged when desipramine (5 mg/kg) was injected in the same way and was decreased by 15% (p less than 0.05) following i.p. injection of the MAO inhibitor pheniprazine (5 mg/kg). Treatment with alpha-methyl-p-tyrosine (75 mg/kg), i.p. 30 min before surgery or 6-hydroxydopamine (50 mg/kg) i.v. 24 hours prior to surgery also increased the flap survival (56 and 49% increase in surviving flap area, respectively, p less than 0.001). The results demonstrated that the survival of skin flaps increased when the function of the adrenergic nervous system was inhibited. Enhanced sympathetic nervous activity slightly reduced or did not affect skin flap survival.