ANI Monitor V1 - Continuous analgesia monitoring system
10
MD/PRD/IN16.ANIV1 V.14 - 12 MAR 2020
ANI (Analgesia Nociception Index) is a standardized continuous measurement of the relative
p
tone. Each respiratory cycle (spontaneous and artificial) induces a fast, temporary decrease
of the p
tone, which accounts for Respiratory Sinus Arrhythmia, and leads to a transient
shortening of the R-R intervals (increased heart rate). ANI quantifies these "respiratory
patterns" in order to measure the "relative quantity" of p
tone (see 5.2).
The series of normal, non-ectopic, R-R intervals is displayed on the screen of the ANI
Monitor V1 after normalization, resampling and filtering. The amount of p
tone is measured
in relation to the total window surface through the area comprised between the lower and the
upper envelope of the RR series, which is continuously displayed as a shaded area. The higher
the p
, the higher the shaded surface, and reciprocally.
ANI measurement cannot be interpreted in the following situations:
•
arrhythmia
•
apnea (e.g. apnea induced by anesthesia)
•
respiratory rate lower than 9 cycles/min
•
electric noise during the measurement period (64 seconds)
•
irregular spontaneous ventilation (patient speaking, laughing or coughing)
•
pace maker (certain types)
•
heart transplant
•
drugs affecting the sinus node (atropine and other anticholinergic drugs, etc.)
The ANI is expressed between 0 and 100. Each ANI value is computed on one time window
of 64 sec. This number shows the relative p
activity as a part of ANS activity: it expresses
the relative amount of p
tone present as compared to sum of sympathetic and p
activities.
The ANI Monitor V1 displays two averaged ANI measurements: ANIi results from the
average of ANI measured over the last 120 sec, and ANIm results from the average of ANI
measured over the last 240 sec.
There are multiple ways of interpreting an ANI value: one is probabilistic, as this index has
been developed in order to predict hemodynamic reactivity during nociceptive stimulation.
When surgical stimulation was constant, all hemodynamic reactivity episodes (20% increase
of heart rate or systolic blood pressure compared to a reference) were associated with a
decreased ANI up to 10 min beforehand. The predictive thresholds need yet to be established,
but preliminary studies suggest:
