Peak plasma concentration of total and free bupivacaine after erector spinae plane and pectointercostal fascial plane blocks.

PURPOSE

Erector spinae plane blocks (ESPB) and pectointercostal fascial (PIFB) plane blocks are novel interfascial blocks for which local anesthetic (LA) doses and concentrations necessary to achieve safe and effective analgesia are unknown. The goal of this prospective observational study was to provide the timing (T) and concentration (C) of maximum total and free plasma bupivacaine after ESPB in breast surgery and after PIFB in cardiac surgery patients.

METHODS

Erector spinae plane blocks or PIFBs (18 patients per block; total, 36 patients) were performed with 2 mg⋅kg of bupivacaine with epinephrine 5 μg⋅mL. Our principal outcomes were the mean or median C of total and free plasma bupivacaine measured 10, 20, 30, 45, 60, 90, 180, and 240 min after LA injection using liquid chromatography with tandem mass spectrometry.

RESULTS

For ESPB, the mean (standard deviation [SD]) total bupivacaine C was 0.37 (0.12) μg⋅mL (range, 0.19 to 0.64), and the median [interquartile range (IQR)] T was 30 [50] min (range, 10-180). For ESPB, the mean (SD) free bupivacaine C was 0.015 (0.017) μg⋅mL (range, 0.003-0.067), and the median [IQR] T was 30 [20] min (range, 10-120). After PIFB, mean plasma concentrations plateaued at 60-240 min. For PIFB, the mean (SD) total bupivacaine C was 0.32 (0.21) μg⋅mL (range, 0.14-0.95), with a median [IQR] T of 120 [150] min (range, 30-240). For PIFB, the mean (SD) free bupivacaine C was 0.019 (0.010) μg⋅mL (range, 0.005-0.048), and the median [IQR] T was 180 [120] min (range, 30-240). For both ESPB and PIFB, we observed no correlations between pharmacokinetic and demographic parameters.

CONCLUSION

Total and free bupivacaine C observed after ESPB and PIFB with 2 mg⋅kg of bupivacaine with epinephrine 5 μg⋅mL were five to twenty times lower than levels considered toxic in the literature.