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Baricity CSF Density — FRCA Primary MCQ

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ModeratePharmacology - AnalgesicsBaricity CSF DensityFRCA Primary

Regarding spinal anaesthesia baricity refers to the density of the local anaesthetic solution relative to:

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Correct answer: B — CSF at 37°C

Baricity = density of LA solution / density of CSF at 37°C. Hyperbaric solutions (baricity >1.0 e.g. heavy bupivacaine 0.5% in 8% glucose) sink to dependent areas. Isobaric solutions (baricity ~1.0) spread less predictably. Hypobaric solutions (baricity <1.0) rise to non-dependent areas. Patient position during and after injection determines spread.

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care