Estimation of Pain During Epidural Analgesia During Labor (PERIDANS)

Epidural regional anesthesia is a technique to eliminate or lessen pain during obstetric labor and childbirth. It consists in establishing a catheter into the epidural space and to block the transmission of pain sensations by injecting a local anesthetic and an opioid. In 10-25% of cases the epidural does not give perfect results, causing it to test its effectiveness, which is mainly done by questioning the patient on mitigation or disappearance of pain. This collaboration of patients is sometimes limited in our care structure by the inability to assess or express the pain, mainly due to cultural differences or language barriers, which can represent up to 15% of women in our institution. This led to develop objective measures of pain techniques used at the bedside.

Pupil diameter (PD) varies under the double influence of sympathetic system (Σ), dilator of the pupil, and parasympathetic system (pΣ).

The PD increases in response to painful stimulation, in proportion to the intensity of the nociceptive stimulus. This variation of PD has been proposed as a means of evaluation of pain in patients under general anesthesia, but has been little studied in conscious subjects.

There are other permanent changes in the PD, due to constant interaction between Σ and pΣ systems. Few data have been published to date on this PD variability (PDV).