The Perioperative Use of Dexmedetomidine and Magnesium Sulfate Compared With Traditional Anesthetic Technique for Open Resection of Pheochromocytoma.

Pheochromocytoma (pheo) is a catecholamine secreting tumor arising from chromaffin cells of the adrenal medulla in 90% of cases & in 10% is extra-adrenal arising from the sympathetic chain. It is malignant in 10% of cases, bilateral in 10% of patients & 10% of all pheo are inherited (Familial Pheo) as autosomal dominant either alone or as a part of multiple endocrine neoplasia (MEN) syndrome.The anesthetic management of Pheo during surgical resection is usually challenging & faces many cardiovascular risks as tachycardia, arrhythmias, severe hypertension & may be pulmonary edema & profound hypotension after surgical devascularization of the tumor. These dangerous events are sequelae of catecholamine excess and often are refractory to management . The proper anesthetic control is based on the use of α₁ & β-adrenergic blockers (phenoxy-benzamine, phentolamine, propranolol, labetalol) and vasodilators such as glycerine trinitrate (GTN) & sodium nitroprusside (SNP) .The rational of using magnesium sulphate MgSo₄ infusion to control catecholamine levels & catecholamine-related crisis has been established in several clinical emergencies such as severe tetanus & preoperative management of pre-eclampsia & eclampsia . MgSo₄ beneficial cardiovascular effects may be attributed to its ability to reduce catecholamine release from the adrenal medulla & to reduce α-adrenergic receptors sensitivity to catecholamines . MgSo₄ is also a direct vasodilator & a potent anti-arrhythmic drug particularly with high circulatory catecholamine level . The safety of MgSo₄ in the routine clinical range of 2-4 mmol/Liter is well settled in many clinical works.

There is strong evidence that the sympathetic nervous system is intact in Pheo patients & neurons-released noradrenaline plays a fundamental role in blood pressure BP regulation. Dexmedetomidine is a short acting & highly selective central α₂-agonist that inhibits neuronal firing & thereby induces analgesia, anxiolysis, bradycardia & hypotension. It has been tried to attenuate the sympathetic pressor effect of tracheal intubation, cardiac surgeries & emergence from anesthesia .The unique adventitious anesthetic pharmacology induces preoperative sedation, intra-operative hemodynamic stability beside reducing the anesthetic requirements and adding to post-operative analgesia . Its peri-operative use has been suggested in both pediatric & adult patients of Pheo.

In this prospective work,the investigators tried to compare the peri-operative hemodynamic course of Dexmedetomidine & MgSo₄ infused patients with the traditional anesthetic technique (α₁ & β-adrenergic blockers plus vasodilators) during open surgical resection of Pheo. The investigators are aiming to check the safety & efficacy of this recommended technique on the peri-operative hemodynamic stability & controlling the hypertensive crisis during tumor manipulation.