Predictors of successful neuraxial block: a prospective study

Background and objective: The epidural and subarachnoid spaces should be identified at the first attempt, since multiple punctures increase the risk of postdural puncture headache, epidural haematoma and neural trauma. The study aimed to describe the predictors of successful neuraxial blocks at the first attempt. Methods: After institutional Review Board approval, 1481 patients undergoing spinal or epidural anaesthesia were prospectively enrolled. For each block we recorded: gender, age, height, weight, body habitus, anatomical landmarks (palpability of the spinous processes), spinal anatomy, patient positioning, premedication, needle type and gauge, approach, spinal level of the block, and the provider’s level of experience. Retrieval of cerebrospinal fluid or loss of resistance to saline or air identified the subarachnoid and epidural spaces, respectively. The outcome variable was the first attempt success or failure (whether or not the needle was correctly located with one skin puncture and produced adequate surgical anaesthesia). Backward stepwise logistic regression tested its association with the other variables. Results: The first-attempt rate of success was 61.51%. Independent predictors (Odds ratio, 95% confidence limits) were the quality of anatomical landmarks (1.92 (1.57; 2.35)), the provider’s level of experience (1.24 (1.15; 1.33)) and the adequacy of patient positioning (3.84 (2.84; 5.19)). Conclusions: The successful location of the subarachnoid or the epidural space at the first attempt is influenced by the quality of patients’ anatomical landmarks, the adequacy of patient positioning and the provider’s level of experience.