Spinal anesthesia failure after local anesthetic injection into cerebrospinal fluid: a multicenter prospective analysis of its incidence and related risk factors in 1214 patients.

Background And Objectives: Different mechanisms have been proposed to explain spinal anesthesia failure even after LA injection into the subarachnoid space. The aim of this prospective multicenter study was to assess the incidence of spinal anesthesia failure, excluding technical problems, and then to suggest independent factors leading to failure.

Methods: Consecutive spinal anesthetic procedures performed in 21 centers were included. Exclusion criteria were contraindications to spinal anesthesia and technical difficulties. Primary end point was the calculation of failure incidence. Factors leading to spinal anesthesia failure were investigated.

Results: One thousand two hundred fourteen spinals were included. Failure rate, reported by 17 of 21 centers, was 3.2% (95% confidence interval [CI], 2.2-4.2). A total failure (no sensory block) was noted in 41% of the 39 cases of failed block. Patients in the failure group were younger as compared with patients in the success group. Using backward logistic regression, factors associated with failure were the number of puncture attempts at 3 or more (odds ratio [OR], 2.86; 95% CI, 1.20-6.79) and the absence of the use of an adjuvant medication with the local anesthetic injected (OR, 2.32; 95% CI, 1.2-4.5). Age older than 70 years (OR, 0.3; 95% CI, 0.20-0.93) was associated with a decrease of failure.

Conclusions: The results of this study showed that the incidence of spinal anesthesia failure was 3.2%. The number of puncture attempts at 3 or more and the absence of adjuvant medication associated with local anesthetic were independent factors associated with the increased risk of failure. The failure of spinal anesthesia was rare in patients older than 70 years.