LAUSR

BACKGROUND Multiple patient and clinical characteristics contribute to the variable outcome of spinal anaesthesia (SPA). Acute reduction of cerebrospinal fluid (CSF) volume may alter the effect of SPA. The objective of the present study was to test if aspiration of 10 mL CSF immediately prior to SPA is associated with higher extent of sensory block. METHODS Interventional cohort study. 102 patients undergoing total hip arthroplasty (THA) were included. Fifty-one patients underwent sampling of 10 mL CSF prior to SPA (CSF aspiration group); 51 consecutive patients were used as controls. The primary outcome was the extent of sensory block to cold stimulus 20 minutes after injection of hyperbaric bupivacaine. Secondary outcome measures included duration of motor block and incidence of failed SPA. RESULTS Acute reduction of CSF volume by 10 mL increased the extent of sensory anaesthesia (thoracic level [T] 4.3 ± 2.4 [mean ± SD] vs T7.1 ± 2.6, p<0.001). There were no significant between-group differences regarding motor block duration (p≥0.30) or failed SPA (3/51 [CSF aspiration group] vs 1/51 [control group], p=0.31). In a retrospective data analysis, 10 of 13 patients in the CSF aspiration group who had previously received SPA had a higher sensory block after 10 mL CSF aspiration compared to the previous SPA (T4.1 [range, 0-11] vs T8.2 [4-10], p<0.01). CONCLUSIONS Acute reduction of CSF volume by 10 mL prior to SPA leads to a higher thoracic level of sensory block.