#ONE DILATED PUPIL SERIES#
The participants were then told to listen to a series of statements about some of the objects they had seen, such as “The car was facing to the left” and asked to indicate as quickly as possible if each was true or false. Authors’ contributionsĭata collection, data analysis and writing up of first draft: S.N.įinal approval: H.W.S.S.They recruited 24 students and asked each one to carefully examine a series of objects displayed to them in one corner of a computer screen. sedation might be preferred for patients at risk for increases in intracranial pressure in order to avoid potentially risky transfers to carry out unnecessary imaging procedures. 6, 7 If our reports are verified by appropriate investigations, i.v. The importance of this knowledge is emphasized by the increased use of volatile anaesthetics for the sedation of critically ill patients. Therefore, it is crucial to know that volatile anaesthetics may be able to induce mydriasis under special circumstances. The relevance of our finding is not restricted to neurosurgery, because patients with potentially increased intracranial pressure and mydriasis are often first investigated in the emergency room or intensive care unit. Why was pupillary dilatation reversed only after days in one patient, and why did an increase in isoflurane concentration during 20 h result in mydriasis in one patient? Future studies are warranted to understand the underlying mechanisms. 5 Given that volatile anaesthetics were stopped immediately in all patients, no additional information in this regard can be derived from the presented patients. In this context, clonidine, fentanyl, and repeated increases in volatile anaesthetic concentration prevent volatile anaesthetic-induced pupillary dilatation by an unknown mechanism of habituation. Notably, mydriasis is not induced in every patient by volatile anaesthetics. 5 Instead, it is hypothesized that volatile anaesthetics inhibit the pupilloconstrictor nucleus. Current evidence suggests that pupillary dilatation is not mediated by the sympathetic nervous system. The mechanism of mydriasis is not fully understood. In two of the patients, the sevoflurane concentration was increased within 0.5 h (2.0 vol% increased to 2.5 vol%, and 1.4 vol% increased to 2.5 vol%), and in the third patient the isoflurane dose was more than doubled (from 4 to 10 ml h −1) during 20 h. 4 However, there is currently no evidence-based cut-off dose. Nevertheless, our results are supported by small studies demonstrating that sedation with desflurane can induce mydriasis 4, 5 and that pupillary dilatation is correlated with rapid increases in dose. To the best of our knowledge, there are no reported clinical cases of isoflurane- and sevoflurane-induced pupillary dilatation. In one patient (sevoflurane), pupillary regression was delayed over a few days. In two patients (sevoflurane and isoflurane), pupil size status normalized within 1 or 2 h after cessation, respectively. The hypothesis that volatile anaesthetics caused the pupillary dilatation in these patients is strongly supported by the temporal correlation between cessation of volatile anaesthetics and reversion of mydriasis. Taken together, the common explanations for pupillary dilatation were excluded. Local anaesthetics containing epinephrine, which are frequently used for the pin-sites for head fixation in functional neurosurgery and can cause unilateral or bilateral pupillary dilatation, 1, – 3 were not used in the reported instances. Medications with potentially mydriatic effects, such as atropine and ketamine, but also antiarrhythmic and anti-asthmatic drugs, were not administered before the observed pupillary changes. In all three patients, emergency imaging excluded intracranial hypertension as the most common cause of mydriasis in the acute setting. Clinicians should be aware of this rare phenomenon to avoid unnecessary imaging or even neurological interventions based on false-positive results.
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We observed three instances of transient pupillary dilatation during sedation with volatile anaesthetics without corresponding intracranial pathology. Editor-Pupillary dilatation is one of the few warning signs for increased intracranial pressure in sedated patients, which would necessitate immediate treatment.