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.
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.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
30
standardized noxious stimulus with tetanic stimulation
University Hospital
Lille, Nord, France
change in ANI between head-down tilt (Trendelenburg) position and head-up tilt position
Position -20° to +20°
Time frame: 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 between horizontal position and head-down/head up tilt position
Position 0° to -20° Position +20° to 0°
Time frame: 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°
Time frame: 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
Time frame: 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°
Time frame: 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°
Time frame: during changes of operating table slope (i.e., for 1-2 min in each condition, 10-15 min after initial measurements in basal conditions)
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