Isoflurane has the dual effects on nociceptive stimulation. It produces hyperalgeia at low partial pressure (0.1 MAC), while displays an antinociceptive effect at higher concentrations (0.4 MAC^0.6 MAC). The different actions of isoflurane on Aδ and C fibers of the spinal cord, and the neuronal nicotinic acetylchlorine receptors (nAChRs), adrenoceptors (including α1 and α2 receptors), excitatory neuronal synaptic transmission ( NMDAergic and AMPAergic), and inhibitory neuronal synaptic transmission ( GABAergic and glycinergic), substance P, and c-fos gene in the central never system may contribute to the mechanisms of isoflurane’s dual effects.
Objective To compare the entropy with narcotrend indexes during the period of propofol induction and tracheal intubation. Methods Eighteen patients of ASA Ⅰ-Ⅱ were inducted by target-controlled infusion (TCI) of propofol, target was set according to the effect compartment concentration (Ce), stepwise increasing (0.5 mg/L) method was used, after the final Ce (6 mg/L) was achieved, orotracheal intubation was performed. Observer’s assessment of alertness/sedation scale (OAA/S) was used to detect the changes of consciousness. Response entropy (RE), state entropy (SE), stages and values of narcotrend (NT), MAP and HR were recorded at each step of Ce, and the time-point of before, immediately, and 1min to 10min after tracheal intubation. Results Scores of OAA/S scale were decreased with the increases of Ce of propofol. Ce according to OAA/S score of 2 and 0 were 2.0±0.6 mg/L and 2.2±0.6 mg/L, respectively. Values of RE, SE, and NT were decreased gradually with the increases of Ce, especially the NT values. The Spearman rank correlation coefficient between Ce and RE, SE, NT values were -0.83,-0.80 and -0.86 (P<0.01), respectively. RE, SE, and NT values at the point of 2.0 mg/L of Ce were significantly lower than those of baseline. Compared to the values of before intubation, RE and SE of immediately after intubation were significantly increased (P<0.05), MAP and HR at the time-point of 1min and 2min after intubation were also increased(P<0.05), however, values and stages of NT had no statistically significant changes during the period of intubation. Conclusions Both Entropy and Narcotrend indexes can reflect promptly the changes of consciousness during the induction of propofol, and they have a close correlation with the effect compartment concentration of propofol, especially the stages and values of NT. Entropy index (RE and SE) and hemodynamic indictors (MAP and HR), but Narcotrend index (stages and values), can reflect the stimulation of tracheal intubation.
