Abstract
BACKGROUND: Differences in epidural pressure (EP) may influence the spread of blockade in thoracic epidural anesthesia. We evaluated if EP and the incidence of subatmospheric EP differ between the mid- and low-thoracic epidural space. METHODS: Patients received an epidural catheter at the T3-5 (MID group, n = 20) or T7-10 (LOW group, n = 20) intervertebral space, respectively. The epidural space was identified using a Tuohy needle connected to a pressure transducer, after which EP was measured. RESULTS: The epidural space could not be identified in three patients who were excluded from the study. EP data are presented as median value (interquartile range). Median EP was 1 mm Hg (-1 to 4.5) in the MID group, and 4 mm Hg (2-7.8) in the LOW group (P = 0.04). The incidence of an EP <or=0 mm Hg was 8 of 17 patients in the MID group and 2 of 20 patients in the LOW group (P = 0.02). CONCLUSIONS: We conclude that EP is lower, and the incidence of subatmospheric EP is higher in the mid-thoracic epidural space when compared with that in the low-thoracic epidural space. However, median EP was positive in both groups. It remains to be investigated whether this pressure gradient is sufficient to influence the spread of thoracic epidural blockade.
