Nerve Stimulator-guided Thoracic Paravertebral Block for Elderly Patients Undergoing Thoracotomy: analgesia characteristics and pharmacokinetics of ropivacaine

Thoracic paravertebral block (TPVB) can be used for surgical anesthesia and analgesia in thoracotomy. Few studies on pharmacokinetics of ropivacaine in elderly patients with a nerve-stimulator technique have been reported. The objective of this study was to describe the analgesic characteristics and pharmacokinetics of ropivacaine in elderly patients undergoing thoracotomy after nerve stimulator-guided thoracic paravertebral block combined with general anesthesia. Ten male elderly patients who underwent elective posterolateral thoracotomy successfully received a single-injection nof erve stimulator-guided TPVB with 0.5% ropivacaine 2mg/kg before general anesthesia. The intraoperative profiles and postoperative visual analogue pain scale (VAS) was recorded and arterial and venous blood was collected at the time of 2, 5, 10, 20, 30, 45, 60, 90, 120, 180min after ropivacaine injection. Plasma ropivacaine concentrations were mearsured by high performance liquid chromatography. All elderly patients tolerated well after TPVB without developing relevant complications. Most of them (8/10) experienced hypotension intraoperatively and required ephedrine when maintained with 1.0 MAC sevoflurane during general anesthesia. TPVB provided good postoperative analgesia at rest during immediate postoperative period. The pharmacokinetic parameters of ropivacaine were C-max1 (1.87 +/- 0.72) and (1.93 +/- 0.57) mu g/mL, C-min (0.85 +/- 0.35) and (0.78 +/- 0.34) mu g/mL, T-max1 10(2-45) and 15(5-20) min in arterial and venous plasma, respectively. There was no significant difference in C-max1 and T-max1 of ropivacaine between arterial and venous plasma (P=0.60, 0.81, and 0.60 respectively). In conclusion, TPVB with a nerve stimulator offered a safe plasma concentration in elderly patients undergoing thoracotomy whilst producing effective anesthesia and analgesia during the operation and shortly after the operation.