Evaluation of the depth of sedation in an intensive care unit based on the photo motor reflex variations measured by video pupillometry

Abstract

BackgroundEvaluating depth of sedation in the intensive care unit (ICU) is crucial for the management of mechanically ventilated patients but can be challenging in some situations. Because the depth of hypnosis is correlated with the decrease in photomotor reflex (PMR), we suggest using pupillometric video as an automated, noninvasive, simple, and reproducible technique to evaluate the depth of sedation in ICU patients. We compare the effectiveness of this procedure to the bispectral index (BIS).MethodsThirty-one patients requiring sedation and ventilation were included in this monocentric, observational study. The posology of hypnotics and morphinics were based on the Richmond Agitation and Sedation Scale (RASS). PMR was measured by the Neurolight® (IDMED) system and BIS value by BIS Vista® (Anandic Medical Systems). RASS, PMR, and BIS were measured three times daily in all patients. Data acquired by pupillometric video included variation in pupillary diameter (ΔPD), latency time (LT), and maximal speed of pupillary constriction (Vmax). These parameters were analyzed after having classified BIS values in three groups (<40 heavy sedation; 40 ≤ BIS ≤ 60 acceptable sedation; >60 light sedation). Exclusion criteria were neurological or ophthalmologic pathologies that could interfere with PMR.ResultsThere was a significant difference in Vmax and ΔPD between the BIS < 40 group and 40 ≤ BIS ≤ 60 groups (p < 0.0001 for each) and between the BIS < 40 and BIS > 60 groups (p < 0.0001 for each). There were no significant differences in Vmax and ΔPD between the 40 ≤ BIS ≤ 60 and BIS > 60 groups. There was no correlation between any of the BIS groups and LT.ConclusionsVmax and ΔPD seem to be relevant criteria compared with the BIS and the RASS. Pupillometric video monitoring of depth of sedation could be beneficial in ICU patients, especially for those under myorelaxant drugs, where no clinical evaluation of sedation is possible.

Assessing pain objectively: the use of physiological markers

“…It measures both pupillary diameter and the light‐induced pupillary dilatation reflex, shown to change in response to noxious stimuli . However, the pupillary response can be influenced by drugs, including analgesic, antiemetic, anticholinergic and vasoactive agents, environmental luminance, age and rare entities such as Horner's syndrome . In addition, the mechanism of pupillary response in sedated patients remains unclear.…”

Can hypnosis and virtual reality reduce anxiety, pain and fatigue among patients who undergo cardiac surgery: a randomised controlled trial

“…We will assess heart rate: normal heart rate is from 60 to 110 heart beats per minute (depending on whether or not the patient regularly pratices sport) [61]; arterial pressure: normal arterial pressure is from 9.5 to 14.9 [62]; respiratory rate: normal respiratory rate is from 12 to 20 cycles per minute [61]; oxygen saturation: normal values of oxygen saturation are from 95% to 100% [61]; and pupil size: pupil diameter varies from 1 to 10 mm and normal range is from 2 to 8 mm [63].…”

Pupillary abnormalities in non-selected critically ill patients: an observational study

“…Indeed, identification of drug-induced PAs, which was a common finding in the present study, might help clinicians to adapt treatments and/or surveillance. The occurrence of pupillary areflexia in relation to the administration of an anesthetic drug (e.g., opioids) should encourage the reappraisal of the treatment dose and/or the use of an automated pupillometer able to detect a small light reflex missed by clinical examination (11,15). In the present work, anisocoria was observed in 9 awake patients after nebulization of ipratropium bromide.…”

“…Moreover, clinical examinations performed with a penlight are often unable to detect a light reflex when pupils constrict less than 0.3 mm and/or when pupils are very small (10,12). This scenario might be very frequent in ICUs, notably because of the routine use of morphine derivatives, which promote the occurrence of miosis (15). Indeed, several reports indicate that opioids given at anesthetic doses likely result in a decreased pupillary light constriction below the threshold of 0.3 mm (12,16,17).…”