Predicting difficult spinal anesthesia: development of a neuraxial block assessment score

BACKGROUND: Spinal anesthesia is a commonly performed procedure with unpredictable difficulty. The objective of this study was to predict a difficult lumbar spinal anesthesia with clinical elements that are easy to collect. METHODS: A questionnaire-based, observational study named NBA, conducted from February 2018 to June 2018. The questions regarded clinical elements and the eventual spinal anesthesia difficulty encountered. A total of 427 questionnaires were filled by the operators. The clinical elements were selected upon literature search and have been integrated with new ones. All the answers were recorded from the anesthesiologist performing the procedure. RESULTS: The NBA Score was derived from a total number of 427 questionnaires. Among them, 26 patients had "previous history of difficult spinal anesthesia;" 277 had "spinous processes not visible;" 83 had "spinous processes not palpable;" 77 had "spinal deformities" and 28 had "previous spinal surgery" in the puncture area; 138 patients received lumbar spinal anesthesia in lateral position. There were 328 (76.8%) single puncture successes. Seventy-nine (18.5%) patients required more than one skin puncture to obtain a successful spinal anesthesia. 20 (4.7%) required an alternative anesthesia technique (general anesthesia). Multivariate analysis indicated that each element is a risk factors for difficult spinal anesthesia, except for previous spinal surgery. CONCLUSIONS: The combination of more than one element increased the chance of a second skin puncture of more than 50%. This work proposes a simple clinical scoring system predicting the probability of a difficult spinal anesthesia.