Based on a pilot study of 20 participants, 10 in each group, the mean visual analogue score of pain at rest (VAS) ± Standard Deviation (SD) at 6 hours postoperatively for Thoracic paravertebral block group (TPVB) participants were 3.0 ± 1.4 and that for systemic analgesia (SA) participants were 4.2 ± 1.6. The calculated significant sample size with a power of 0.85 and alpha error of 0.05 was 60 participants, with 1:1 allocation in each group.
Eighty two participants were assessed for eligibility criteria to be included in the study, 18 participants were excluded pre-randomization, and one participant was excluded post-randomization due to re-exploration for bleeding. Sixty three participants were analyzed in the study. Thoracic paravertebral block group (TPVB group) included 32 participants and systemic analgesia group (SA group) included 31 participants.
Technique of intraoperative paravertebral catheter insertion:
The investigators used the technique that was described by Sabanathan et al in 1988\[14\] and modified by them in 1990 \[15\]. After completing the surgical pulmonary procedure and with the chest is still open, starting from the posterior end of the thoracotomy, parietal pleura is raised from the posterior chest wall to the vertebral body and for two spaces above and below the incision of thoracotomy creating a pouch. A 16-gauge disposable Tuohy needle is inserted percutaneously through a low posterior interspace. The needle is advanced until the tip appeared in the created pouch. The stylet is removed, and a 16-gauge side-holed epidural catheter is advanced into the created pouch and the needle is withdrawn. Using a curved forceps, a small defect is done in the extrapleural fascia to be directly in the paravertebral space. The cannula is passed to the paravertebral space through the defect and advanced cranially for 2 to 3 cm. The parietal pleura is reattached to the posterior edge of the wound and the catheter is secured. Then a bolus dose 15-20 ml of 1% lidocaine is injected through the catheter and the chest is closed as usual with one or two intercostal drainage tubes according to the surgical procedure.
Protocol of analgesia:
All participants, in both groups, received intravenous analgesia with 1gm paracetamol and 30 mg ketorolac half an hour before the end of surgery.
Systemic analgesia (SA) group continue to receive 1gm paracetamol and 30 mg ketorolac by intravenous infusion every 6 hours for 3 days. Thoracic paravertebral block (TPVB) group received continuous infusion of 0.1 ml/kg/h of 1.0% lidocaine (l mg/kg/h) using infusion pump through the inserted paravertebral catheter for 3 days. Intravenous morphine sulfate (0.05mg/kg) was given as a rescue medication if the VAS ≥ 4 for both groups. A senior nurse was responsible for handling the analgesia regimen and another nurse was responsible for recording pain score on visual analogue scale (VAS) and morphine consumption, as scheduled.
