Time course of action and pharmacokinetics of ropivacaine in adult and elderly patients following combined lumbar plexus-sciatic nerve block.

OBJECTIVE

Large doses of local anesthetics are needed in combined lumbar plexus-sciatic nerve block. The safety of local anesthetics is important among elderly patients. This study investigates the pharmacokinetics of ropivacaine in elderly patients with combined lumbar plexus-sciatic nerve block.

METHODS

Ropivacaine pharmacokinetics and the time of onset, duration of sensory and motor block were studied in adult patients (18 - 60 y) and elderly patients (>= 60 y). Combined lumbar plexus-sciatic nerve block was performed using a nerve stimulator. 0.375% ropivacaine was injected in patients. Plasma concentration of ropivacaine was determined by high performance liquid chromatography.

RESULTS

There was no significant difference in onset time and time to peak (tmax1, tmax2) between elderly patients and adult patients. Half-life time (t1/2alpha, t1/2beta) and the duration of sensory and motor block were longer in elderly patients (p < 0.05). While the peak plasma concentrations of (double peaks, Cmax1, Cmax2) wer lower in elderly patients than that in adult patients.

CONCLUSIONS

Age does not affect the onset time of ropivacaine after combined lumbar plexus-sciatic nerve block but can influence the motor and sensory recovery. Local absorption of ropivacaine is slower in elderly patients compared to adults.