Journal Article

P270 Blending the block: measuring baricity when morphine meets hyperbaric bupivacaine

Callewaert Nico, Desmet Matthias, Marie-Camille, Vanderheeren, Lapere Matthias, Croes, Kathleen, Vanthourenhout Sanne

2025

Overview

Application for ESRA Abstract Prizes:Background and AimsIn spinal anesthesia, baricity determines intrathecal drug spread and block characteristics. Hyperbaric bupivacaine is widely used for lower limb arthroplasties. In our institution, it is routinely combined with preservative-free morphine to enhance postoperative analgesia. While this combination is common in clinical practice, its physicochemical effect on baricity has not been quantified. We aimed to evaluate the density - and hence baricity - of this custom-made intrathecal mixture.MethodsThe density of hyperbaric bupivacaine (Marcaine® Spinal 0.5% Heavy), morphine (100 µg/mL in saline), and their 2.2:1 mL and 2.4:1 mL (Marcaine®:morphine) mixtures were measured at room temperature using the Menarini Aution MAX AE-4030 system. Three samples of each solution were analyzed. Theoretical calculations were performed for validation.ResultsMean measured densities (standard deviation) in g/cm3 were: morphine 100 µg/mL: 1.004 (0.001); hyperbaric bupivacaine: 1.029 (0); mixture (2.2 + 1 mL): 1.021 (0.001); mixture (2.4 + 1 mL): 1.021 (confirmed in duplicate). Theoretically calculated densities for these mixtures were 1.0212 and 1.0216 g/cm3, respectively. Despite the dilution, the final mixture remains hyperbaric relative to CSF (~1.0003 g/cm3 at 37°C).ConclusionsThis is the first study to quantify the baricity of a commonly used morphine-bupivacaine spinal mixture. Although addition of the morphine solution lowers the density of hyperbaric bupivacaine, the mixture remains hyperbaric, supporting its continued clinical use with expected spread behavior. These findings reinforce the importance of physicochemical validation in custom-made intrathecal preparations.

• Publisher: BMJ Publishing Group LTD
• Subject: Morphine