Article
Comparison of quantitative pupillometry and intracranial pressure (ICP) in patients with increased ICP
Vergleich der quantitativen Pupillometrie mit dem intrakraniellen Druck (ICP) bei Patienten mit erhöhtem ICP
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Published: | May 8, 2019 |
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Objective: Testing the pupillary light reflex (PLR) plays a role in neurosurgical conditions. Changes of the pupil’s dynamics may parallel an elevated ICP. Quantitative pupillometry is a reliable tool to quantify the pupil dynamics.
To calculate the pupillary dynamics in patients with increased ICP and to observe whether pupillary dynamic index (NPi) may indicate an elevated ICP.
Methods: Quantitative pupillometry with bedsize device NPi®-200 (Neuroptics Inc.). Infrared-light based recognition of the pupil followed by a white light pulse to induce a light reflex. Recording of pupillary constriction/dilation (PC/PD), measurement of parameters max. and min. size (MAX/MIN), constriction latency (CL), constriction/dilation velocity (CV/DV) as well as the neurological pupil index (NPi; normal 3–5, pathological 0–2.9) reflecting the overall pupil dynamic.
Repeated bilateral PLR of 20 ICU-patients with ICP-recording. Normal values from 50 healthy test persons without neurological disorders as normalized values.
Results: In healthy persons, illumination caused PC from 5.5 mm to 3.5 mm in diameter (37±4 %), mean CV was faster than DV (3.0±0.5 vs. 1.0±0.2 mm/sec; p<0.001), mean NPi was 4.3±0.3. 20 pts (14 m/6f; 36–78y) with ICP above 15 mmHg were included. PLR was heterogeneously depending on the underlying pathological processes (i.e. type of herniation). Eight of these 20 patients had episode ICP episodes between 15 and 20 mmHg and all PLR including NPi were normal (3.0–5.0). 12 patients showed spikes of ICP above 20 mmHg and in 9 out of these 12 patients. NPi showed well marked signs of abnormalities during the 24 hours preceding the increase of ICP. Signs of abnormalities in the NPi are: i) drop of baseline of NPi, ii) asymmetry between the left/right NPi, iii) at least one NPi below 3. Changes of the individual pupillary parameters (mostly size of the pupil and CV) varied across patients and they did not show the same relevance. Significant NPi abnormalities were often transitory and not only seen in transtentorial herniation. No patient died of herniation during the observation period.
Conclusion: Pupillometry may indicate important changes of intracranial dynamics in patients with increased ICP. In some cases low NPi may precede a life threatening ICP increase. In all pts. it returned to normal after immediate therapeutic measures to decrease ICP. Pupillometry does not substitute ICP recording but provides important clinical information.