The aim of this study is to evaluate the validity of perfusion index to determine the level of anesthesia in comparison with auditory evoked potential in children undergoing tonsillectomy.

The use of the perfusion index as an added monitoring tool during anesthesia provides the anesthetist with a number of benefits. It is a useful tool to forewarn the clinician of possible light planes of anesthesia, allowing for agent dose adjustment. It is a preexisting technology that is already widely available and used in most urban, regional,and rural centers, in both developed and developing countries, is noninvasive, continuous, and inexpensive.

The AEP Monitor/2 (Danmeter A/S, Odense, Denmark), a commercialized system for depth of anesthesia monitoring, extracts the middle latency auditory evoked potentials (MLAEP) from the EEG-signal by using an autoregressive model with an exogenous input adaptive method

Inclusion Criteria:

• Patients aged 3-12 years
• Elective tonsillectomy due to recurrent or chronic tonsillitis

Exclusion Criteria:

• Cerebral disease
• Cardiac disease,
• Renal disease,
• Pulmonary disease
• Hepatic disease.

ASA physical status I-II patients aged 4-12 years and scheduled for elective tonsillectomy due to recurrent or chronic tonsillitis will be included in the study. Excluded from the study will be patients with significant cardiac, renal, pulmonary or hepatic disease.