Assessment of thoracic epidural analgesia during general anesthesia using pupillary reflex dilation: a preliminary study.
OBJECTIVE
Pupillary reflex dilation (PRD) secondary to noxious stimulation accurately predicts sensory block during combined lumbar epidural/general anesthesia. Therefore, the adequacy of PRD-guided thoracic epidural infusion during general anesthesia for thoracotomy was studied.


METHODS
Prospective study.


METHODS
University hospital.


METHODS
Thirteen patients undergoing thoracotomy.


METHODS
An epidural catheter was placed at the T3-T4 level with initial infusion rate of 5 mL/h of ropivacaine 0.5%. Propofol/remifentanil target-controlled infusion was used for induction and maintenance of general anesthesia. Remifentanil effect site concentration was maintained constant at 0.5 ng/mL during surgery. By using a portable pupillometer, PRD secondary to tetanic stimulation of the C8, T2, and T4 segments were evaluated. Ropivacaine flow rate was adapted half hourly, according to PRD testing and a predefined algorithm. At the end of surgery, PRD was tested in the 3 investigated segments, and general anesthesia was stopped. After emergence, these zones were tested for their sensitivity to cold. Pain was evaluated by using the visual analog scale.


RESULTS
Pain scores were <3 of 10 in 84.6% of the patients. Mean PRD was 0.9 +/- 0.6 mm in unblocked levels versus 0.2 +/- 0.5 mm in blocked segments (p = 0.02). PRD >or= 0.5 mm was predictive of incomplete block (sensitivity 76%, specificity 79%, and positive predictive value 86%). PRD >or= 1 mm was highly predictive of inadequate block (sensitivity 73%, specificity 91%, and positive predictive value 94%).


CONCLUSIONS
PRD-guided continuous thoracic epidural analgesia under low-dose remifentanil/propofol anesthesia is feasible and ensures good postoperative analgesia.
Huybrechts
Isabelle
I
Department of Anesthesiology, Erasme University Hospital, Free University of Brussels, Brussels, Belgium. isabelle.huybrechts@ulb.ac.be <isabelle.huybrechts@ulb.ac.be>
Barvais
Luc
L
Ducart
Anne
A
Engelman
Edgard
E
Schmartz
Denis
D
Koch
Marc
M
D000577:Amides / Q000008:administration & dosage; D000767:Anesthesia, Epidural / Q000379:methods*; D000768:Anesthesia, General / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage; D002404:Catheterization; D005260:Female; D006801:Humans; D007268:Injections, Epidural; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010147:Pain Measurement; D011446:Prospective Studies; D012025:Reflex, Pupillary / Q000502:physiology*; D000077212:Ropivacaine; D013904:Thoracic Vertebrae; D013908:Thoracotomy; D016896:Treatment Outcome
D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine