Neuroplasticity Induced by General Anaesthesia

Study Overview
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Brief Summary
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The aim of this study is to use magnetic resonance imaging to explore and compare possible de novo neuroplastic changes induced by the isolated effects of the hypnotic agents sevoflurane and propofol, respectively. In addition, to explore possible associations between neuroplastic changes and clinical and/or biochemical outcomes. It is a randomised, cross-over, single blinded clinical study. N = 30. Female:male ratio 1:1.

Detailed Description
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Background In the perioperative period, severe changes can be observed in the endocrine, immune, and nervous system. These changes are called the surgical stress response. Clinically, this can be observed as increased pain response and disturbances in the circadian rhythm, memory, cognitive and executive functions, and may lead to post-operative delirium. The post-operative cognitive dysfunction is associated with increased mortality and risk of prematurely leaving occupation. Post-operative delirium with fluctuating levels of attention and consciousness is a serious condition associated with poor outcome, including longer hospitalisation and increased early mortality. General anaesthesia may contribute to the surgical stress response. Some data indicate that general anaesthesia per se can cause alterations and disturbances in the brain such as sleep and circadian disturbances. Recent evidence suggests that anaesthetic agents may impair neurogenesis and cause memory impairment. In addition, inhalation anaesthesia may result in more cerebral disturbances compared to total intravenous anaesthesia (TIVA). In this study, we will isolate the effects of the two primary hypnotic agents used in general anaesthesia, sevoflurane and propofol, without the interactions and confounders of polypharmacy and varying levels of disease among a surgical population. Materials The study consists of two study sessions. In each study session magnetic resonance imaging (MRI) scans will be obtained before and after general anaesthesia, and in addition after one and eight days. The following imaging modalities will be employed: (i) T1-weighted 3D anatomy (T1w3D), (ii) Diffusion Tensor Imaging (DTI), (iii) resting state functional MRI (rsfMRI). The MRI scans will be supplemented with cognitive testing, sleep evaluation and blood sampling. Thus, the set-up for each volunteer will be: Session one: Day 0: MRI 1, cognitive testing, questionnaires, and blood sampling. General anaesthesia (maintenance phase with sevoflurane OR propofol according to randomisation), and post-anaesthesia care. MRI 2 and repeated cognitive testing, questionnaires, and blood sampling. Day +1: MRI 3, cognitive testing, questionnaires, and blood sampling. Day +8: MRI 4, cognitive testing, and questionnaires. Session two: Identical to session one, except the volunteer will receive the remaining type of general anaesthesia (sevoflurane or propofol, opposite to session one). Data evaluation will be conducted with assessor blinded to anaesthesia type.

Official Title
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Neuroplasticity Induced by General Anaesthesia

Conditions
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Healthy Volunteers, General Anaesthesia, Neuroplasticity

Intervention / Treatment
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* Drug: Sevoflurane-propofol


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age ≥18 and ≤35. Healthy individual. BMI ≥18 kg/m2 and ≤30kg/m2. Normal electrocardiogram (ECG). Normal physical examination, including neurological examination, auscultation of the heart and lungs, and measurement of blood pressure and pulse. American Society of Anaesthesiologists (ASA) class 1. Mallampati I-II and simplified airway risk index (SARI) 0-2 (i.e. no indication of difficult intubation). See appendix for details. Right-handed. Female participants must use safe contraceptives (hormonal or mechanical, including intrauterine devices). Speaks and understand Danish. Provides oral and written informed consent. Exclusion Criteria: Contraindications to MRI. Left-handedness or ambidexterity. History of complications to general anaesthesia, including malignant hyperthermia. Family history of malignant hyperthermia. Known incident of malignant hyperthermia or any unexplained complication to general anaesthesia among close relatives. Allergy to any kind of medication or material to which the volunteer could be exposed during this study. History of serious illness. History of cancer, immune disease, autoimmune disease, chronic pain or neurological / psychiatric illness. Major trauma or head trauma with any symptoms present at the time of inclusion. Surgery less than six weeks prior to the study period. Infection (with fever) less than two weeks prior to or during the study sessions. Daily use of any medication (not counting contraceptives). Consumed anti-depressants during the last 30 days before study days. Weakly intake of >21 (for females >14) units of alcohol. Heavy intake of caffeine (> 5 cups/day). Smoking during the last 30 days before study days. Substance abuse (assessed by the investigator). Pregnancy Reflux or dyspepsia. Poor dental status or oral health. Expected or suspected difficult airway. Declines receiving information regarding accidental pathological findings during MRI scans of the brain. Cannot cooperate to tests. Otherwise judged unfit for participation by the investigator. Exclusion Criteria during the study: Any of the above-mentioned exclusion criteria. Major trauma or head trauma during the study period. Surgery during the study period. Infection (with fever) during the study period. Consumption of more than 3 units of alcohol within 24 hours before each study day (intervention day or MRI scan day) Consumed analgesics within 3 days before each study day Consumed anti-histamines less than 48 hours before each study day Intake of caffeine 12 h prior to each study day Smoking

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Randomisation to one of two options in session 1: sevoflurane or propofol. In session 2, the remaining option is administered.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Sevoflurane-Propofol<br>Session one: Sevoflurane as maintenance anaesthetic during general anaesthesia. Session two: Propofol as maintenance anaesthetic during general anaesthesia. | Drug: Sevoflurane-propofol<br>* General anaesthesia with a maintenance phase of two hours duration with either sevoflurane or propofol.<br>* Other names: Propofol-sevoflurane;|
| Active Comparator: Propofol-Sevoflurane<br>Session one: Propofol as maintenance anaesthetic during general anaesthesia. Session two: Sevoflurane as maintenance anaesthetic during general anaesthesia. | Drug: Sevoflurane-propofol<br>* General anaesthesia with a maintenance phase of two hours duration with either sevoflurane or propofol.<br>* Other names: Propofol-sevoflurane;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in T1w3D | Volume and morphology of selected brain regions and anatomical structures as recorded by T1w3D anatomy MRI. | 8 days | 
| Changes in DTI | White matter microstructure as measured using Diffusion Tensor Imaging (DTI) | 8 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in rsfMRI | Differences in resting state functional MRI induced by general anaesthesia | 8 days | 
| Changes in fatigue | Differences in severity and characteristics of fatigue related to general anaesthesia, as measured by Multidimensional Fatigue Inventory (MFI-20, a scale of 0-5 in each of 20 questions, with higher scores indicating more fatigue). | 8 days | 
| Cognitive performance | Changes in cognitive function related to general anaesthesia, measured with a combination of Test of Attentional Performance, Paced Auditory Serial Addition Test and Conners Continuous Performance Test. | 8 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Sevoflurane, Neuroplasticity, Neuroplastic changes, General anaesthesia, Magnetic resonance imaging, Propofol, Healthy volunteers, Consciousness, Cognitive, Fatigue