Effect of thoracic epidural etidocaine 1.5% on somatosensory evoked potentials, cortisol and glucose during cholecystectomy

The effect of thoracic (T_7–8) epidural etidocaine 1.5%, 9 ml, and continuous per‐ and postoperative epidural infusion of etidocaine 1.5%, 4 ml/h, on early (?<500 ms) somatosensory evoked potentials (SEPs), and cortisol and glucose in plasma during cholecystectomy, was examined in ten patients. Spread of analgesia (pin‐prick) was T₃ (T₁–T₃) to L₂ (T₁₁–L₃) 35 min after injection of etidocaine, and T₃ (T₂–T₄) to T₁₂ (T₈–L₄) 3 h after surgical incision (median (range)). Before operation, epidural etidocaine had no significant effects on peak‐to‐peak amplitude of SEPs to electrical stimulation at the L₁ T₁₀ or T₆ dermatomal level (P>0.09). SEPs were abolished in only two patients at T₆, and no patient had SEPs abolished at T₁₀ or L₁. The plasma concentrations of cortisol and glucose were significantly increased 20 min after surgical incision and remained increased throughout the study. No correlation was found between the block‐induced decrease in the peak‐to‐peak amplitude at T₆ or T₁₀ and increase in plasma cortisol, except for a negative correlation at T₁₀ and the initial increase in cortisol (Rs = 0.72, P = 0.03). In conclusion, thoracic epidural administration of 9 ml of etidocaine 1.5% does not provide total afferent somatic blockade assessed by SEP and the stress response to cholecystectomy.