Memory During Inhalation Anesthesia Performed With or Without Bispectral Index (BIS) in Patients Undergoing Thyroidectomy

Study Overview
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Brief Summary
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The purpose of this study is 1) to investigate whether the use of BIS as a guide to the administration of inhaled anesthetic (sevoflurane or desflurane) compared with the use of hemodynamic parameters (blood pressure and heart rate) would affect the occurrence of implicit memory and /or dreams recall and 2) to check whether the occurrence of implicit memory and/or dreams recall is related with MAC (Minimal Alveolar Concentration) of inhalational anesthetics and/or preoperative anxiety levels.

Conditions
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Thyroidectomy

Intervention / Treatment
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* Drug: Inhaled anesthetics
* Drug: Inhaled anesthetics


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age between 18 and 70 years Class-ASA Physical Status I-II Exclusion Criteria: Psychiatric or neurological disorders and/or hearing disorders Obesity (Body Mass Index > 30) Drug addiction, alcoholism Patient with difficulty in understanding italian language and/or education level below middle school

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Hemodynamic parameters<br>Hemodynamic parameters will be used as a guide for anesthesia. | Drug: Inhaled anesthetics<br>* Inhaled anaesthetic drugs (sevoflurane or desflurane) concentration will be changed on the basis of hemodynamic parameters (mean arterial pressure and heart rate greater or less than 20% compared to preoperative values).<br>|
| BIS<br>Bispectral Index (BIS) will be used as a guide for anesthesia. | Drug: Inhaled anesthetics<br>* Inhaled anaesthetic drugs (sevoflurane or desflurane) concentration will be changed on the basis of Bispectral Index (BIS) value which will be maintained between 40 and 50.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Implicit memory | Implicit memory will be investigated using free association test: patients, during maintenance of anesthesia, will listen a piece of one of two stories, Puss in Boots or Pinocchio, each followed by four keywords. Approximately 24 hours after surgery, patients will be asked to associate the first thing that comes to mind with these keywords in order to highlight the presence of implicit memory. The test will be repeated twice and will be positive if the patient will reply with the title of the story or a word of it. | Approximately 24 hours after surgery | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Dreams recall | A first interview about dreams recall will be carried out 5 minutes after awakening from anesthesia. Patients will be asked about dream content. | Approximately 5 minutes after awakening from anesthesia | 
| Explicit memory | Patients will be asked about the last thing they remembered before going to sleep; the first thing they remember when they woke up; and anything which happen in between, including sounds, dreams and imagination. | Approximately 24 hours after surgery | 
| Dreams recall | Patients will be asked again about dreams recall. The content of dreams will be analyzed using the 5-point Likert scales which contains the following dreams characteristics: memory content, emotional content, emotional intensity, vivid description, amount of sounds, meaning, how much movement, strange, episodic content, references to episodes of life. | Approximately 24 hours after anaesthesia |