Influence of Variations of Systemic Venous Return on Analgesia Nociception Index (ANI) During General Anaesthesia

Study Overview
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Brief Summary
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The purpose of this study is to determine whether the value of analgesia nociception index (ANI) is influenced by variations of systemic venous return (cardiac preload) under general anaesthesia.

Detailed Description
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In the context of opioid sparing goal during general anaesthesia, the Analgesia nociception index (ANI) is an analgesia/nociception balance monitoring tool computed from high frequency heart rate variability analysis, and developed by MetroDoloris (Lille, France). Its sensitivity to detect noxious stimulus was studied in several studies. However, its specificity is not established in particular in the presence of factors influencing autonomic nervous system other than analgesia/nociception balance. In the context of anaesthesia, one of the most relevant factor is hypovolemia. This study aims to assess the effect of blood volume variations on ANI under general anaesthesia, independently of analgesia/nociception balance status. Variations of systemic venous return (SVR) (cardiac preload), which reflects blood volume status, will be induced by changes of operating table slope, from head-down tilt (Trendelenburg), with increased SVR, to head-up tilt position, with decreased SVR. Variations of SVR will be attested by changes in the arterial pulse pressure variation, a well-established indice of preload responsiveness in the mechanically ventilated anaesthetized patient.

Official Title
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Influence of Variations of Systemic Venous Return on Analgesia Nociception Index (ANI) During General Anaesthesia

Conditions
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Hypovolemia, Somatic Pain

Intervention / Treatment
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* Procedure: noxious stimulus
* Procedure: change in operating table slope: head-down tilt position
* Procedure: change in operating table slope: head-up tilt position


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: neurosurgical operation requiring invasive monitoring of arterial blood pressure Exclusion Criteria: pacemaker, arrhythmia chronic medication with beta blocker possible disorder of autonomic nervous system: diabetes, alcoholism, chronic pain anticholinergic drug administration before measures intracranial hypertension no social security coverage pregnancy

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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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: patients<br>noxious stimulus change in operating table slope: head-down tilt position change in operating table slope: head-up tilt position | Procedure: noxious stimulus<br>* standardized noxious stimulus with tetanic stimulation<br>Procedure: change in operating table slope: head-down tilt position<br>* -30°<br>* Other names: Trendelenburg position;Procedure: change in operating table slope: head-up tilt position<br>* +30°<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change in ANI between head-down tilt (Trendelenburg) position and head-up tilt position | Position -20° to +20° | during changes of operating table slope (i.e., for 1-2 min in each condition, 10-15 min after initial measurements in basal conditions) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change in ANI between horizontal position and head-down/head up tilt position | Position 0° to -20° Position +20° to 0° | during changes of operating table slope (i.e., for 1-2 min in each condition, 10-15 min after initial measurements in basal conditions) | 
| change in pulse pressure variation between head-down tilt position and head-up tilt position | Position -20° to +20° | during changes of operating table slope (i.e., for 1-2 min in each condition, 10-15 min after initial measurements in basal conditions) | 
| change in ANI induced by standardized noxious stimulus (tetanic stimulation) | ANI measurement following tetanus | during a 5sec-tetanic stimulation (measurement for 1-2 min, 2-5 min after initial measurements in basal conditions) | 
| variations of low frequency variability of arterial blood pressure | Position 0° to -20° Position -20° to +20° Position +20° to 0° | during changes of operating table slope (i.e., for 1-2 min in each condition, 10-15 min after initial measurements in basal conditions) | 
| change in pulse pressure variation between horizontal position and head-down/head up tilt position | Position 0° to -20° Position +20° to 0° | during changes of operating table slope (i.e., for 1-2 min in each condition, 10-15 min after initial measurements in basal conditions) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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analgesia nociception index, heart rate variability, autonomic nervous system, specificity, systemic venous return, pulse pressure variation, Intraoperative Monitoring