Objective: To study the relation between cerebrospinal fluid (CSF) glucose levels, the highest level of sensory block, and the duration of motor block after intrathecal injection of 2 mL of hyperbaric bupivacaine. To determine CSF glucose levels upon recovery from motor block.
Patients and methods: A prospective study of 34 patients administered a spinal anesthetic in continuous infusion through a 22-gauge catheter. CSF samples were extracted through the catheter 5, 10, 15, 20, 30, 45, and 60 minutes after start of infusion and upon motor recovery. After each extraction the intensity of the motor block was assessed; the intensity of the sensory block was assessed after each extraction up to 20 minutes.
Results: Glucose concentrations in CSF tended to decrease from 5 minutes (1027.07 [SD 349.04] mg dL(-1)) until full motor recovery (247.50 [20.39] mg dL(-1)). The probability of finding a motor block at a CSF glucose concentration of 287.5 mg dL(-1) or higher was less than 5%. We identified a positive correlation between the highest level of sensory block and the duration of full motor block (r=0.62, P<0.01) and between CSF glucose levels at the moment of greatest sensory block and upon full motor recovery (r=0.50, P<0.01).
Conclusions: After continuous spinal anesthesia with hyperbaric bupivacaine, glucose concentrations in CSF are directly related to the highest level of sensory block, the course of the blockade, and its reversal.