Impact of bupivacaine on the neonate delivered by caesarean section under spinal anaesthesia

Background and aim Very few data are available on the overall impact of bupivacaine (BUP) on the neonate delivered by caesarean section under spinal anaesthesia. The aim of this study was to investigate a) the maternal-foetal transfer of BUP; b) the neonate's ability to metabolize BUP; and c) the clinical impact of BUP on the neonate. Materials and methods Twenty-two neonates (gestational age, 32.2 ± 3.2 weeks; birth weight, 1562 ± 572 g) delivered by caesarean section under spinal anaesthesia (hyperbaric bupivacaine 0.75%) and admitted to the Neonatal Intensive Care Unit (NICU) were prospectively enrolled. Two serial urine samples were non-invasively collected in each patient at 0-24 h (T0) and 48-72 h (Tl) of life. The urinary concentrations of BUP and its metabolite 3'-hydroxybupivacaine (3'-OH-BUP) were determined by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry. Moreover, Apgar scores, acid-base status, clinical indicators of cardiovascular and neurological dysfunctions (0-48 h of life) and in-hospital mortality were recorded. Results BUP was found in urine of all patients at T0 (mean+SD, 0.205 ± 0.198 ppb), and significantly decreased at T1 (0.094 ± 0.102 ppb; p=0.0052). In contrast, urinary 3'-OH-BUP concentration did not change significantly in the same time interval (0.143 ± 0.173 ppb at T0, and 0.165 ± 0.298 ppb at T1; p=NS). Mean Apgar scores at 1 and 5 min were 7.0 and 8.2, respectively, while mean capillary blood pH was 7.28 at NICU admission. Urinary BUP at T0 was not correlated either to 1 - and 5-minute Apgar scores, or to blood pH. All patients survived and there were no significant cardiovascular or neurological dysfunctions. Conclusions Our findings show that BUP readily crosses the placenta to the foetus, and is metabolized by the newborn since birth. Nonetheless, no clinically significant effect of BUP was detectable in our patients during the first 48 h of life.