A feasibility study of the Pupillary Pain Index measurement in Anesthetized Children

Author(s): Nathalie Kegels, Saldien Vera, Hans Guy, Wildemeersch Davina

What we already know

(a) Pain assessment in anesthetized children is challenging and currently used methods are not specific

(b) Pupillometry has already shown to be interesting and the pupillary pain index (PPI) in anesthetized adults shows promising results What new information this study ads

(c) PPI can be a useful tool for non-invasive nociceptive assessments, in anesthetized, pediatric patients

Background: Inadequate treatment of pain has numerous negative consequences. However, treatment with opioids can also be detrimental, with potential harmful effects after overdosing. Intraoperative hemodynamic parameters used today are non-specific nociceptive surrogate markers and insufficient to provide an objective nociceptive assessment. Furthermore, those variables have a wide variety depending on age.

Aim: This study aims to evaluate whether pupillary pain index (PPI), via pupillary dilation reflex (PDR), can be used as a feasible nociceptive monitoring tool in the pediatric surgical population. Furthermore, pupil characteristics in two age classes (A = 28 days to 23 months, B = 24 months to 11 years) are identified.

Methods: Twenty pediatric patients scheduled for elective surgery under general anesthesia at the Antwerp University Hospital (UZA, Edegem, Belgium) were included. PDR was determined by an automatic stimulation pattern whereby intensity was increased (1s stimulation, 10-60mA, steps of 10mA). Pupil measurements were executed at two standardized times during a steady state sevoflurane. T0 and T1, respectively without and with opioids. Vital signs were registered during measurement.

Results: PPI score decreased after opioid administration (group A: 2 vs 1, P<0.05; group B: 2 vs 1 P<0.05). Vital signs did not change significantly during noxious stimulation. In both groups the PDR amplitude and pupil variation decreased when opioids were administered (amplitude A: 0,24mm vs 0,06mm, B: 0,24mm vs 0,07mm; variation A: 12,1% vs 2,9%; B: 10,3% vs 2,5%, respectively). At T1, miosis was only observed in group B (group A: 1.87mm vs 1.84mm, P=0.7; group B: 2.27mm vs 2.51mm, P<0.05).

Conclusions: These preliminary results clearly confirm earlier novel research. The PPI via PDR evaluation provides a fast and easy approach to assist in the evaluation of the nociceptive – anti-nociceptive balance in anesthetized children. The pupil differs in size depending on age and opioid dosage. Further research is essential to evaluate opioid dosing effects on PDR.

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