الفهرس 
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Abstract
Summary
Controlled hypotensive anesthesia represents a great challenge for the otolaryngologists and anesthetists.
It is the elective lowering of arterial blood pressure.
The primary advantages of this technique are minimization of surgical blood loss and better wound visualization.
Studies stated a decrease of MAP of 50 to 65 mmHg or a 30% reduction of baseline MAP at the surgical site was believed to decrease blood loss significantly.
There are many techniques to deliberate hypotension as physiological, mechanical and pharmacological methods.
In Pharmacological methods reducing BP act either by lowering the systemic vascular resistance (SVR) or by lowering the cardiac output (CO).
The ideal pharmacological agent for controlled hypotension would have an ease of administration, predictable and dose dependent effect, rapid onset and recovery from effect, quick elimination without production of toxic metabolites, minimal effects on blood flow to vital organs and should not increase the brain size or affect cerebral auto regulation.
Monitoring of hypotensive anesthesia should be done by, blood pressure measurement, electrocardiography, gas exchange, monitoring of central venous pressure, blood gases, acid-base balance, urine output and cerebral blood flow monitoring.
When a clear indication for hypotensive anesthesia exists, several relative contraindications must be considered such as hypertension, myocardial ischemia, cerebrovascular diseases, respiratory diseases, diabetes mellitus, renal and liver dysfunction, congestive heart failure, anemia, pregnancy and old age.
This study included 40 healthy patients ASA I or II who underwent Functional endoscopic sinus surgery (FESS), they were enrolled after provision of consent to participation. They were randomly divided into two equal groups (20 patients each) .
group GTN received an infusion of glyceryl trinitrate at the level of 25-200 μg/min, according to the response diluted in 0.9% saline which will start after sterilization and positioning of the patients..
group DEX received loading dose of 1μg/kg dexmedetomidine diluted in 100 ml 0.9% saline over 10 minutes just before induction of anesthesia, followed by continuous infusion of 0.2-0.7 μg/kg/h.
Monitoring for Patients was done using electrocardiography (ECG), non- invasive blood pressure, pulse oximetry and capnography.
The goals in this thesis are to compare the effects of glyceryl trinitrate and dexmedetomidine, on the visibility of the surgical site and to compare these two agents in terms of satisfaction of the surgeon, recovery period, adverse effects and postoperative analgesia.
In our study, it was confirmed that dexmedetomidine causes significant stable hemodynamics, excellent surgical field and significant surgeon satisfaction compared to glyceryl trinitrate. It also causes sedation effect so less extra doses of fentanyl was used.
We do conclude that during ambulatory FESS, dexmedetomidine is more effective than glyceryl trinitrate for providing controlled hypotension and rendering an excellent surgical field with higher surgeon’s satisfaction score and lesser analgesic requirement without major hemodynamic alteration.