Topical vasoconstriction technique After oral intubation, vital signs and all anaesthetic parameters will be kept as constant as possible for the duration of the surgery. Three cotton neuropatties will be soaked with 4% cocaine. One neuropattie will be placed in the sphenoethmoidal recess, one in the middle meatus, and one in the anterior end of the middle turbinates on the side that the randomization has determined. In the other side, three cotton neuropaties will be soaked with adrenaline 1:1000 and placed in the same positions than the others. Then the patient will be draped and both sides will be injected with xylocaine 2% and adrenaline 1:100.000. After this we will wait for 10 minutes and the surgery will be initiated.