Effect of adrenergic stimulation on cutaneous microcirculation immediately after surgical adventitiectomy in a rat skin flap model

Abstract

Chronic sympathetic denervation leads to the development of supersentivity to adrenergic agents. Free flap surgery results in the disruption of the autonomic nerve fibers running along the anastomosed vessels. We therefore investigated the early effect of surgical sympathectomy on the reactivity of cutaneous microcirculation challenged to adrenergic agents. Two epigastric flaps were elevated and exposed in 15 rats. On the right flap (Side A), a circular adventitiectomy of the feeder vessels was realized to provide surgical sympathectomy. On the left flap (Side N), vessels were kept intact. The following drugs were then given intravenously successively: phenylephrine (10 and 15 microg kg(-1)), norepinephrine (10 microg kg(-1)), prazocin (1 mg kg(-1)) followed by norepinephrine (10 microg kg(-1)). Cutaneous microcirculation was assessed using Laser-Doppler Flowmeters simultaneously on the two flaps after each drug administration. Mean arterial pressure was also measured. On side N, phenylephrine and norepinephrine resulted in a transient increase in cutaneous microcirculation followed by a more prolonged reduction. On side A, only the initial increase was observed, which was greater and longer as compared with side N, and paralleled the increase in mean arterial pressure. After prazocin pre-treatment, norepinephrine produced a transient increase in cutaneous microcirculation similar on both sides, and parallel to the changes in arterial pressure. No decrease in cutaneous microcirculation was observed. Immediately after surgical adventitiectomy, the vasoconstriction produced by alpha-adrenergic agents is prevented. No denervation-induced hypersentivity is observed. Surgical sympathectomy might protect cutaneous flaps from vasoconstriction induced by endogenous catecholamines release.

Impact of vasopressors on outcomes in head and neck free tissue transfer

“…5,6 The microvascular surgeon's fear of vasopressors likely stems from the belief that these drugs may provoke pedicle vasospasm, which can lead to thrombosis and flap failure. The existing animal literature is controversial on the issue of pedicle vasospasm, with some authors reporting that the pedicle is alpha-agonist resistant 7 while other authors report that the pedicle is highly sensitive to alpha-agonists. 1 These changes in vessel sensitivity are presumed to occur secondary to the sympathectomy resulting from the dissection and division of the vascular pedicle.…”

Emerging Paradigms in Perioperative Management for Microsurgical Free Tissue Transfer

“…[29][30][31]33,73 Animal studies have demonstrated an attenuated response to norepinephrine and phenylephrine following surgical sympathectomy. 91 Following vasopressor administration, cutaneous microcirculation actually increased in an amount proportional to the change in mean arterial pressure in postsympathectomy tissue, whereas flow in normal tissue was reduced. When the effects of phenylephrine, dopamine, and dobutamine were compared in a swine musculocutaneous flap model, phenylephrine reduced cardiac output and flap flow.…”

Epinephrine, Norepinephrine, Dobutamine, and Dopexamine Effects on Free Flap Skin Blood Flow

“…A similar effect has been observed when innervated and denervated pedicle flaps were raised in a rat model. 14 In these studies, the denervated flaps had an increase in blood flow after norepinephrine or phenylephrine (␣ 1 agonist) administration, with a simultaneous reduction in flow in the innervated flap. The effect was blocked by prazosin, a selective blocker of ␣ 1 receptors on vascular smooth muscle, suggesting the effect was due to a decreased sensitivity to ␣ 1 agonists.…”