Acute pain after serratus anterior plane or thoracic paravertebral blocks for video-assisted thoracoscopic surgery: A randomised trial.

BACKGROUND:Serratus anterior and paravertebral blocks can both be used for video-assisted thoracic surgery. However, serratus anterior blocks are easier to perform, and possibly safer. We therefore tested the primary hypothesis that serratus anterior plane blocks and thoracic paravertebral blocks provide comparable analgesia for video-assisted thoracic surgery. Secondarily, we tested the hypothesis that both blocks lengthen the time to onset of surgical pain and reduce the need for rescue tramadol. METHODS:Patients having video-assisted thoracic lobectomy or segmentectomy were randomly allocated to ultrasound-guided thoracic paravertebral blocks, n = 30; ultrasound-guided serratus anterior plane blocks, n = 30; or, general anaesthesia alone, n = 30. Visual analogue pain scores analogue pain scores at rest, during coughing and Prince-Henry pain scores were used to assess postoperative analgesia. Our primary analysis was noninferiority of serratus anterior blocks compared with paravertebral blocks. RESULTS:Baseline characteristics were comparable among the three groups. Two hours after surgery, the mean difference in visual analogue pain scores between the serratus anterior and paravertebral blocks was 0.0 (96.8% CI -0.4 to 0.3) cm at rest, -0.2 (-0.8 to 0.4) cm during coughing and -0.1(-0.5 to 0.3) for Prince-Henry pain scores. After 24 h, the mean difference was 0.0 (-0.7 to 0.8) cm at rest, 0.1 (-0.8 to 0.9) cm during coughing and 0.1(-0.4 to 0.6) for Prince-Henry pain scores. All differences were significantly noninferior. Time to onset of pain after surgery was 19 ± 5 (SD) hours with serratus anterior blocks, 16 ± 5 h with paravertebral blocks and 12 ± 5 h with general anaesthesia. Anaesthesia with either block was associated with significantly less intra-operative propofol and sufentanil, reduced postoperative rescue analgesia (tramadol) and less postoperative nausea and vomiting compared with general anaesthesia alone. Patients with serratus anterior block had a significantly lower incidence of intra-operative hypotension and requirement for intra-operative vasopressor (3.4%), compared with general anaesthesia alone. Serratus anterior block took less time to perform than paravertebral block (5.1 ± 1.1 min versus 10.1 ± 2.9 min). CONCLUSION:Serratus anterior plane blocks, which are easier and quicker than paravertebral blocks, provide comparable analgesia in patients having video-assisted thoracic surgery. CLINICAL TRIAL NUMBER AND REGISTRY URL:ChiCTR1800017671; http://www.chictr.org.cn/hvshowproject.aspx?id=13510.