Pulse Transit Time as a Predictor of the Efficacy of a Celiac Plexus Block in Patients With Chronic Intractable Abdominal Pain

Objective: There is no well-defined predictor of satisfactory pain relief after celiac plexus block (CPB) at the early stage of treatment. This study evaluated whether measurement of the electrocardiographic R-wave and the arrival time of the pulses at the toe pulse transit time (E-T PTT) can be an early predictor of pain response and success of CPB in patients with chronic intractable visceral pain. Methods: Twelve patients aged between 20 and 80 years who underwent CPB for treatment of chronic intractable cancer-related abdominal pain were included. A successful CPB was determined as a > 50% decrease on the numerical rating scale measured 24 hours after the procedure. The E-T PTT at baseline and at 5, 10, 20, and 30 minutes after the injection of local anesthetic was measured as the time between the R-wave on the electrocardiogram and the peak point of the corresponding plethysmogram wave from the ipsilateral great toe. The change in the E-T PTT that was predictive of a successful CPB was analyzed using receiver operating characteristic curve analysis. Results: A CPB was successful in 9 of 12 cases; the dE-T PTT5/E-T PTT0 of the success group was 6.84% +/- 5.04% versus 0.72% +/- 0.78% in the failure group (P = 0.021). The mean E-T PTTx differed significantly between timepoints (F = 9.313, P = 0.014) and between the success and failure groups (P < 0.01). The best value of dE-T PTT5/E-T PTT0 indicating a successful CPB, estimated by receiver operating characteristic curve analysis, was 2.30% (sensitivity 88.9%, specificity 100%). The area under the curve was 96% (95% confidence interval, 85.7%-100%). Conclusions: Prolongation of E-T PTT at 5 minutes after CPB correlates closely with a significant analgesic effect.