Correlation of the lumbar dural sac dimension with the spread of spinal anesthesia in elderly female patients: A prospective observational study

Background: To test a hypothesis that the dural sac dimension would be correlated with the spinal block level, we evaluated the correlation between the lumbar dural sac dimension and the spread of spinal anesthesia in elderly women. Methods: In 40 women over the age of 65 years, the lumbar dural sac dimensions were measured at the L2-L3, L3-L4, L4-L5, and L5-S1 intervertebral spaces using ultrasonography in the lateral decubitus position, followed by the administration of spinal anesthesia. The correlation coefficients were analyzed for the lumbar dural sac dimension at each intervertebral level, peak sensory block level, peak motor block, time to peak sensory and peak motor blockade, durations of sensory and motor blockade, and patient characteristics. We subsequently analyzed the partial correlations between the lumbar dural sac dimension and the outcomes of spinal anesthesia, while adjusting for age, body mass index, and waist circumference. Results: Peak sensory block level was inversely correlated with each lumbar sac dimension: L2-L3 (ρ = −0.37, P =.029), L3-L4 (ρ = −0.57, P <.001), L4-L5 (ρ = −0.65, P <.001), and L5-S1 (ρ = −0.49, P =.002) intervertebral spaces. Partial correlation analysis with adjustment for age, body mass index, and waist circumference revealed inverse correlations between the lumbar dural sac dimension at the following intervertebral spaces and peak sensory block level: L3-L4 (r = −.52, P =.003), L4-L5 (r = −.76, P <.001), and L5-S1 (r = −.65, P <.001). Conclusions: Outcomes of ultrasonographic investigation revealed an inverse correlation between the lumbar dural sac dimension and peak sensory block level in elderly women.