Pain assessment in the postanaesthesia care unit using pupillometry: A cross-sectional study after standard anaesthetic care.
BACKGROUND
Patients assess their own pain with a numerical rating scale (NRS). In the postanaesthesia care unit (PACU), NRS helps to determine and monitor analgesic administration, but is useless in patients who are unable to communicate. In non-PACU patients, acute pain increases pupillary diameter and pupillary light reflex amplitude (PLRA), the difference between pupillary diameter before and after light stimulation.


OBJECTIVE
To study the association between postoperative pain (NRS) and pupillary diameter or PLRA in PACU patients after routine anaesthetic care.


METHODS
Cross-sectional cohort study.


METHODS
Bichat-Claude Bernard Hospital, Paris.


METHODS
One hundred and forty-five patients undergoing planned surgery under general anaesthesia.


METHODS
NRS, pupillary diameter and PLRA were measured on arrival in the PACU. When NRS was more than 4, intravenous morphine titration was started and a second measurement performed.


METHODS
Association between NRS and pupillary diameter or PLRA was assessed with Pearson correlation coefficient (r) as was association between changes in these variables after morphine titration.


RESULTS
Mean NRS was 4.7, and was more than 4 in 79 patients (55%). No statistically significant association was observed between NRS and pupillary diameter (r = 0.10, P = 0.54) or PLRA (r = 0.03, P = 0.72). Twenty-seven patients (19%) received morphine titration with significant decreases in NRS, pupillary diameter and PLRA afterwards. No association was observed between NRS changes and pupillary diameter or PLRA changes.


CONCLUSIONS
Acute postoperative pain is not associated with pupillary diameter or PLRA. Further research is required to develop tools to assess pain in the PACU.
From the Département d'Anesthésie-Réanimation, Hôpital Bichat, AP-HP (EK, PM, DL, JG), Université Paris Diderot, Sorbonne Paris Cité (PM, DL, JG) and INSERM, UMR 738 (JG), Paris, France.
Elie
E
Kantor
Philippe
P
Montravers
Dan
D
Longrois
Jean
J
Guglielminotti
D059787:Acute Pain; D000368:Aged; D000700:Analgesics / Q000627:therapeutic use*; D000758:Anesthesia / Q000379:methods*; D000768:Anesthesia, General; D000777:Anesthetics / Q000627:therapeutic use*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000627:therapeutic use; D010146:Pain; D010147:Pain Measurement; D010149:Postoperative Pain; D011184:Postoperative Period; D011446:Prospective Studies; D011680:Pupil / Q000187:drug effects*; D012025:Reflex, Pupillary / Q000187:drug effects*; D013564:Sympathetic Nervous System
D000700:Analgesics; D000777:Anesthetics; D009020:Morphine