RESUMO
BACKGROUND: Minimally invasive thoracic surgery is associated with substantial pain that can impair pulmonary function. Fascial plane blocks may offer a favorable alternative to opioids, but conventional local anesthetics provide a limited duration of analgesia. We therefore tested the primary hypothesis that a mixture of liposomal bupivacaine and plain bupivacaine improves the overall benefit of analgesia score (OBAS) during the first three postoperative days compared to bupivacaine alone. Secondarily, we tested the hypotheses that liposomal bupivacaine improves respiratory mechanics, and decreases opioid consumption. METHODS: Adults scheduled for robotically or video-assisted thoracic surgery with combined ultrasound-guided pectoralis II and serratus anterior plane block were randomized to bupivacaine or bupivacaine combined with liposomal bupivacaine. OBAS was measured on postoperative days 1-3 and was analyzed with a linear mixed regression model. Postoperative respiratory mechanics were estimated using a linear mixed model. Total opioid consumption was estimated with a simple linear regression model. RESULTS: We analyzed 189 patients, of whom 95 were randomized to the treatment group and 94 to the control group. There was no significant treatment effect on total OBAS during the initial three postoperative days, with an estimated geometric mean ratio of 0.93 (95% CI: 0.76, 1.14; p = 0.485). There was no observed treatment effect on respiratory mechanics, total opioid consumption, or pain scores. Average pain scores were low in both groups. CONCLUSIONS: Liposomal bupivacaine did not improve OBAS during the initial postoperative three days following minimally invasive thoracic procedures. Furthermore, there was no improvement in respiratory mechanics, no reduction in opioid consumption, and no decrease in pain scores. Thus, the data presented here does not support the use of liposomal bupivacaine over standard bupivacaine to enhance analgesia after minimally invasive thoracic surgery. SUMMARY STATEMENT: For minimally invasive thoracic procedures, addition of liposomal bupivacaine to plain bupivacaine for thoracic fascial plane blocks does not improve OBAS, reduce opioid requirements, improve postoperative respiratory mechanics, or decrease pain scores.
RESUMO
STUDY OBJECTIVE: To investigate the timing of peak blood concentrations and potential toxicity when using a combination of plain and liposomal bupivacaine for thoracic fascial plane blocks. DESIGN: Pharmacokinetic analysis. SETTING: Operating room. PATIENTS: Eighteen adult patients undergoing robotically-assisted mitral valve surgery. INTERVENTIONS: Ultrasound-guided pecto-serratus and serratus anterior plane blocks using a mixture of 0.5% bupivacaine HCl up to 2.5 mg/kg and liposomal bupivacaine up to 266 mg. MEASUREMENTS: Arterial plasma bupivacaine concentration. MAIN RESULTS: Samples from 13 participants were analyzed. There was substantial inter-patient variability in plasma concentrations. A geometric mean maximum bupivacaine concentration was 1492 ng/ml (range 660 to 4650 ng/ml) at median time of 30 min after injection. In 4/13 (31%) patients, plasma bupivacaine concentrations exceeded our predefined 2000 ng/ml toxic threshold. A second much smaller peak was observed about 32 h after the injection. No obvious signs of local anesthetic toxicity were observed. CONCLUSIONS: Combined injection of plain and liposomal bupivacaine for pecto-serratus/serratus anterior plane blocks produced a biphasic pattern, with the highest arterial plasma concentrations observed within 30 min. Maximum concentrations exceeded the potential toxic threshold in nearly a third of patients, but without clinical evidence of toxicity. Clinicians should not assume that routine combinations of plain and liposomal bupivacaine for thoracic fascial plane blocks are inherently safe.