Predicting difficulty score for spinal anesthesia in transurethral lithotripsy surgery.

Transurethral Lithotripsy (TUL) surgery candidates were enrolled in this observational study from 2010 to 2011. Before SA, the patient`s demographic information along with the Body Mass Index (BMI), lumbar spinous process status, spinal deformity, radiological signs of lumbar vertebrae, and a history of spinal surgery or difficult SA were recorded, then the patients underwent SA in L3-L4 interspinous process space. Information about Cerebrospinal Fluid (CSF) visibility at the first attempt (easy SA) and the times of trying with shifting in that space or trying the second space (moderate SA) and the third space (difficult SA) were recorded. Multinominal regression and relative operating characteristic (ROC) curve were used for statistical analysis.