Nonparallel cutaneous microcirculatory responses to pharmacologic alterations of systemic arterial pressure in rats

Both hypotension and hypertension aggravate the damage of reperfusion injury after reconstructive microsurgery. The purpose of this study is to establish a theoretical guide for postoperative blood pressure control in optimizing the cutaneous perfusion and flap survival. Systemic arterial pressure was altered by the intravenous infusion of saline, sodium nitroprusside, phentolamine, and phenylephrine in thirty-two 280-350 g anesthetized Sprague Dawley rats. Power spectral analysis of systemic arterial pressure (SAP) and laser Doppler flowmetry (flux) of epigastric skin were used to reveal the blood pressure and cutaneous blood flow variabilities. Nonparallel responses of cutaneous perfusion and blood pressure were found. The baseline SAP and flux were 126.0 +/- 1.4 mmHg and 57.2 +/- 1.8 au, respectively. Sodium nitroprusside and phentolamine significantly decreased the SAP (71.1 +/- 2.7 and 70.5 +/- 1.5 mmHg, P < 0.0001). However, the corresponding responses in cutaneous perfusion were opposite (56.2 +/- 3.1 au, P = 0.7389 and 36.2 +/- 2.3 au, P < 0.0001). Phenylephrine significantly increased the SAP (171.7 +/- 3.0 mmHg, P < 0.0001) but the flux of epigastric skin was decreased (44.4 +/- 2.6 au, P < 0.0001). Phentolamine and phenylephrine showed negative effects on the systemic cardiac and vascular sympathetic modulations. Sodium nitroprusside had a trend in increasing systemic vasomotor activity. We suggested not using vasoconstrictors in treating intra and postoperative hypotension associated with free flap transfer. Nitric oxide donors are superior to alpha-adrenoceptor antagonists in preserving the cutaneous flap perfusion when treating postoperative hypertension.