Dynamic Assessment of Pupillary Reflex in Patients on High-dose Opioids

Pupil size reflects the balance between sympathetic and parasympathetic systems. Pupil size and reaction are also influenced by drugs, where opioids result in miosis, an effect that is not considered to be influenced by opioid tolerance. However, cancer patients on high-dose opioids do not always present small pupil size.

We want to perform a dynamic assessment of pupillary reflex in patients on high-dose opioids. In addition to pupil size measurements under standard room light conditions, two pupil size reflexes will by assessed: the pupillary light reflex when the pupil is exposed to light, and the reflex dilation during a standardized noxious stimulus. On the same time we will assess pain intensity, sedation score, and other side effects of opioids while measuring the concentration of opioids and their active metabolites in blood. In addition we will register all concomitant medication that also might influence pupil size and reaction. Patients on more than 60 morphine equivalents pr day will be included.