Predicting difficulty score for spinal anesthesia in transurethral lithotripsy surgery

Background: Spinal anesthesia (SA) is the most common regional anesthesia (RA) conducted for many surgical procedures.

Objectives: The current study aimed to predict the difficulty score of SA, by which to reduce the complications and ultimately improve the anesthesia quality.

Materials and methods: 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.

Results: Hundred and one patients were enrolled. Of these patients, 50 (49.5%) underwent SA by the first attempt of the first space, in 36 patients (35.6%) it was moderate and in 15 patients (14.9%) it was difficult. There was no significant relationship between difficulty score of SA and gender, age, height, and history of previous difficult SA. But there was a significant relationship between difficulty score of SA and lumbar spinous process status (P =0.0001), radiological profile of the lumbar spine (P = 0.0001), the status of lumbar deformity (P = 0.007), and BMI (P = 0.006). Then using the ROC curve to predict the difficult SA, the cutoff point was 8.5 with 86.7% and 86% sensitivity and specificity, respectively.

Conclusions: It seems that considering the clinical examination of patients before SA focusing on lumbar spinous process status, presence of lumbar deformity, calculation of BMI and radiological signs of lumbar vertebrae can be helpful in predicting SA difficulty.