Dexmedetomidine Versus Nitroglycerin on Surgical Field Quality and Drug Cost in Functional Endoscopic Sinus Surgeries

Plain-language summary

Sinus surgery is one of the most prevalent ear, nose, and throat (ENT) surgeries, which is mainly carried out nowadays through functional endoscopic sinus surgery (FESS) and leads to significant improvement in the clinical symptoms of patients with rhinosinusitis. It is necessary to maintain safe conditions for this surgery, and the major problem reported during FESS under general anesthesia (GA) is impaired visibility due to excessive amount of bleeding. This is particularly important for the successful surgery of the ethmoid and sphenoid sinuses because even minimum amount of bleeding might seriously impair the successful completion of the surgery, increase the operational risk, and increase surgery time which are major concerns for both anesthesiologist and ENT specialist. Controlled hypotension is the commonly used technique to limit blood loss and improve visualization in the surgical field during FESS, various techniques have been adopted to achieve controlled hypotension, one of them is the use of pharmacological drugs in the form of volatile anesthetics, direct-acting vasodilators, autonomic ganglion-blockers, and α-adrenergic receptor blockers. Alpha-2 (α-2) receptors are found in the peripheral and central nervous systems, platelets and many other organs including the liver, pancreas, kidney, and eye. Stimulation of the receptors in the brain and spinal cord inhibits neuronal firing causing hypotension, bradycardia, sedation, and analgesia. Alpha-2 (α-2) agonist drugs have sympatholytic, sedative, anesthetic, and analgesic sparing effects, as well as vasoconstrictive effects and thereby reduce intraoperative bleeding. Also, the use of α-2 agonists in the perioperative period has been associated with reduced anesthetic requirements, decreased heart rate and blood pressure. Dexmedetomidine is a highly selective α-2 adrenergic receptor agonist (selectivity ratio for α2: α1 is 1600:1). The sympatholytic effect of dexmedetomidine made it attractive to be used as a hypotensive drug during surgery because of decreasing heart rate (HR) and cardiac output (CO) without decreasing stroke volume unless the plasma concentrates reaches above 5.1 μg/mL. The cardiovascular effects of dexmedetomidine begin with initial hypertension following the administration of a loading dose, due to the activation of α 2B receptors located on vascular smooth muscle, with subsequent hypotension and bradycardia due to centrally mediated decrease in sympathetic tone. Dexmedetomidine also has sedative, amnesic, anxiolytic, hypnotic, and analgesic effects with minimal changes in respiratory variables. Furthermore, it reduces postoperative nausea, vomiting, and shivering. It also reduces delirium in patients after cardiac surgery. Nitroglycerin is a directly acting vasodilator drug frequently used to produce controlled hypotension because it is easily titratable and having very rapid onset as well as rapid offset of action. However, the disadvantages of nitroglycerin are reflex tachycardia and venous congestion which leads to increased blood loss. Aim of the work was improving surgical field quality and drug cost in patients undergoing Functional Endoscopic Sinus Surgeries by comparing between dexmedetomidine and nitroglycerin.

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