Number of dermatomes blocked by conventional dose single shot spinal anesthesia for cesarean section is not positively related to hyperbaric bupivacaine dose – a retrospective analysis of 362 cases

Background Increasing the dose of local anesthetic administered into intrathecal space is associated with higher level of sensory blockade. Despite this common wisdom, the literature data on this relation in population of term parturients is scarce. The aim of this retrospective study was to assess the relation between intrathecal dose of 0,5% hyperbaric bupivacaine and the height of the sensory block level. Methods Medical notes of cesarean section cases were reviewed. All procedures under single – shot spinal anesthesia performed with the dose of more than 9 mg of hyperbaric bupivacaine were identified and scrutinized for availability and quality of the data required for analysis. Demographic and pregnancy – related data were noted. The dose of 0,5% hyperbaric bupivacaine, sensory block after 5 minutes, maximum sensory block level and spinal – related complications were recorded and analyzed. Study group was divided into three groups depending on their height. Results The maximum block level was > T6 in 96% of cases included. Weak negative correlation between the dose of local anesthetic and maximum sensory block level was found (Spearman correlation coefficient − 0.17, p = 0.002). This was confirmed in the two groups of taller women, while in parturients of less than 164 cm of height this relation was not present. With the increase in the dose of bupivacaine, the risk of nausea increased (OR 1.45), no relation was found between vomiting and lowest blood pressure parameters within 30 min of spinal injection. Conclusions No positive relation between the dose and maximum sensory block level was found in this study. Weak but negative relation was present between these variables in the whole study group, as well as in women of more than 165 cm of height.