Background and Goal of Study: No numeric measures of
nociception during general anaesthesia exist. For
monitoring of nociception a multi-parameter approach may
be needed (1). We studied the relation between
physiological responses and concentration of remifentanil
(Rem) at nociceptive stimuli in anaesthetised and
Materials and Methods: 55 females were anaesthetised with
propofol (Pr)-Rem target controlled infusions (TCI). Pr
was given to maintain EEG State Entropy (SE) at 35-60.
Rem TCI was randomised to 1, 3, or 5 ng/ml. Responses to
tetanic stimulation of the ulnar nerve (30 s) were
studied before surgery in a subgroup of 23 patients.
Responses to skin incision were analysed in all patients.
Comparison of responses in photoplethysmographic wave
amplitude (PPGA), ECG beat-to-beat interval (RRI), and
Response Entropy (RE) at different Rem levels was done
using the Kruskal-Wallis H test.
Results and Discussion: RRI (p=0.00001) and PPGA
(p=0.009) responses to tetanic stimulus differed
significantly between Rem levels, while for the incision
RRI (p=0.019), RRI SD1 (p=0.019) and RE-SE (p=0.018)
responses were different. A Response Index of Nociception
(RN), developed by combining RE, RRI and PPGA
variability, was significantly higher in the low doses of
Rem as compared with the higher doses for both tetanic
stimulus (p=0.00005) and skin incision (p=0.00003).
Conclusions: In paralysed patients anaesthetised with
propofol-remifentanil infusions: 1) Combination of
information from RE, PPG, and RRI provides promising
quantification of responses to abrupt noxious stimuli; 2)
Long-lasting 30 sec tetanic stimulus induces
qualitatively similar physiological responses as skin
Reference: 1) Seitsonen E. Anesthesiology 2002: 97: A-582