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Hypobaric versus isobaric spinal levobupivacaine for total hip arthroplasty.

BACKGROUND
Spinal anesthesia (SA) in the lateral decubitus position is often used to perform total hip arthroplasty (THA). Hypobaric local anesthetic ensures enhanced and prolonged sensory and motor block in the involved side. The aim of this study was to compare the intraoperative anesthetic efficacy of hypobaric with isobaric levobupivacaine solutions for THA.


METHODS
Forty patients scheduled to elective THA were allocated into two groups: isobaric levobupivacaine group (IL group) and hypobaric levobupivacaine group (HL group). All the patients were placed with the operative side uppermost on the surgical table and spinal anesthesia was performed with 4 mL (12.5 mg) of selected solution. The evolution of sensory and block on nondependent (operative) and dependent sides were checked.


RESULTS
Regarding the nondependent side the onset times for maximal sensory block level in the in HL group was 17.8±1.1 minutes vs. 24.2±4.1 minutes in IL group. In HL group the onset time for motor block was 9.2±3.5 minutes vs. 15.6±5.4 minutes in IL group. The sensory regression time to L2 was significantly prolonged in HL group (192±30.3 minutes vs. 111±13.4 min). After surgery in HL group the residual motor block degree was 2.4±0.9 vs. 0.2±0.4 in IL group.


CONCLUSIONS
In patients undergoing THA under spinal anesthesia 12.5 mg of hypobaric levobupivacaine, compared with the same dose of isobaric levobupivacaine, allow shorter onset time for sensory block and delayed regression of sensory and motor block in the nondependent side.