The ciliospinal reflex in pentobarbital coma

Abstract

Object: This study was conducted to delineate the ciliospinal reflex (CSR), which is defined as pupillary dilation caused by a noxious stimulus to the face or head. The authors anecdotally observed that patients in a pentobarbital coma have a CSR that can mimic pathological conditions. A pentobarbital coma obscures the results of the neurological examination in patients with potentially life-threatening cerebral edema; pupil size and reactivity are the only readily monitored signs. Any condition that incorrectly suggests evolving intracranial pathological processes can lead to unnecessary clinical actions.

Methods: The authors evaluated six consecutive patients in the neurointensive care unit in whom a pentobarbital coma had been induced, documenting the presence and duration of the CSR. The CSR was always bilateral and symmetrical, manifesting as enlarged (6-8 mm), seemingly nonreactive pupils continuing from 1 to 6 minutes and was usually seen after routine nursing maneuvers. The pupils appeared nonreactive to short flashes of direct light but did react if longer flashes were used.

Conclusions: Recognition of the CSR can potentially lead to reduction of unnecessary transportation and complicating medical interventions in critically neurologically ill patients in whom a pentobarbital coma has been induced.