The Pharmacokinetic of Ropivacaine in Patients Undergoing Ultrasound-guided Continuous Thoracic Paravertebral Block

Patients aged >18yrs, of ASA I-III undergoing open thoracotomy under combined ultrasound guided thoracic paravertebral block (TPVB) and general anesthesia will be enrolled in the study.

TPVB will be performed under ultrasound guidance on the side of the operation immediately after induction of anesthesia and patient intubation, with the patient in the lateral position at the T5 or T6 or T7 thoracic level using a Tuohy 17G needle and the catheter will be advanced 5 cm beyond the point of needle tip.

Dosage regimen Initially, after catheter placement and control, 0.5% ropivacaine is administered via the catheter in a 25 ml single dose, before the start of surgery.

After the end of surgery and patient awakening, the catheter will be connected with an electronic pump and the continuous infusion of ropivacaine 0.2% will start with a constant infusion rate of 14 ml/h for the first 3 postoperative days.

Postoperative pain will be assessed using the Visual Analogue Scale (VAS: 0-10). Postoperative analgesia will be managed with continuous PVB, and systemic administration of paracetamol (1 gr X 4 iv), tramadol (100 mg x 3 iv) and pregabalin (75 mg x 2 pos). Additionally, if VAS is ≥4-5 morphine (2.5 -5mg) will be administered subcutaneously as rescue analgesic drug (max 6 doses/day). In case of persistent pain (VAS > 4-5) despite the previously mentioned treatment measures, PCA morphine will be used.