Change in pulse transit time in the lower extremity after lumbar sympathetic ganglion block: an early indicator of successful block

OBJECTIVE: To investigate the change in pulse transit time (PTT)—time between the electrocardiographic R wave and the highest point of the corresponding plethysmographic wave—after lumbar sympathetic ganglion block (LSGB) and evaluate PTT as an indicator of successful LSGB. METHODS: Sixteen cases of sympathetically mediated lower extremity neuropathic pain treated with LSGB were studied. Correlations between the changes in PTT and temperature were used to identify the cutoff point indicating successful LSGB. RESULTS: PTT rate of change at 5 min relative to the baseline PTT (dPTT5/PTT0) significantly correlated positively with the temperature change at 20 min (correlation coefficient 0.734). The dPTT5/PTT0 ratios of the Success and Failure groups were 6.46 ± 2.81% and 2.77 ± 1.72%, respectively. The dPTT5/PTT0 cutoff indicating successful LSGB, based on receiver operating characteristic curve analysis, was 4.23%. CONCLUSION: PTT measurement 5 min after local anesthetic injection was an early, objective indicator of successful or failed LSGB.