M. Curatolo et al., Block of pinprick and cold sensation poorly correlate with relief of postoperative pain during epidural analgesia, CLIN J PAIN, 15(1), 1999, pp. 6-12
Objective: To test the following hypotheses: there is a correlation between
spread of epidural analgesia as assessed postoperatively by pinprick/cold
test and postoperative pain intensity; block of pinprick/cold sensation is
associated with absence of postoperative pain.
Design: Correlation analysis on prospectively collected data
Setting: University hospital.
Patients: One hundred patients undergoing major surgery. Consecutive sample
.
Interventions: Patients received an epidural infusion of bupivacaine 1 mg/m
l, fentanyl 2 mu g/ml, and epinephrine 2 mu g/ml for at least 48 hours post
operatively. The infusion rate was adjusted according to pain intensity, oc
currence of hypotension, or motor block.
Outcome Measures: Assessments were made on three time points: 20-24 hours,
32-36 hours, and 42-48 hours after extubation. Assessments included pinpric
k and cold sensitivity from C2 to S5, pain intensity (visual analogue scale
, VAS) at rest, after cough, and after mobilization. Data were analyzed by
multiple regression.
Results: VAS significantly decreased with increasing spread (number of derm
atomes for which hyposensitivity to pinprick or cold was observed). Spread
could explain only 2-5% of the variability of VAS. Absence of both pinprick
and cold sensation at all dermatomes corresponding to the surgical wound w
as frequently associated with pain. A high proportion of patients manifesti
ng an upper level of block above T5 had pain after abdominal surgery.
Conclusions: Spread and efficacy of epidural analgesia. as assessed by pinp
rick and cold stimulation correlate poorly with postoperative pain. These m
ethods are of limited value both as clinical indicators of the efficacy of
postoperative pain control and for investigating the effect of epidural dru
gs and techniques.