Low-dose Bupivacaine in Spinal Anaesthesia
Low-dose Bupivacaine in Spinal Anaesthesia
Spinal anaesthesia is the preferred anaesthetic technique for elective Caesarean deliveries. Hypotension is the most common side-effect and has both maternal and neonatal consequences. Different strategies have been attempted to prevent spinal-induced hypotension, including the use of low-dose bupivacaine. We conducted a systematic search for randomized controlled trials comparing the efficacy of spinal bupivacaine in low dose (LD ≤8 mg) with conventional dose (CD >8 mg) for elective Caesarean delivery. Thirty-five trials were identified for eligibility assessment, 15 were selected for data extraction, and 12 were finally included in the meta-analysis. We investigated sources of heterogeneity, subgroup analysis, and meta-regression for confounding variables (baricity, intrathecal opioids, lateral vs sitting position, uterine exteriorization, and study population). Sensitivity analysis was performed to test the robustness of the results. In the LD group, the need for analgesic supplementation during surgery was significantly higher [risk ratio (RR)=3.76, 95% confidence interval (95% CI)=2.38–5.92] and the number needed to treat for an additional harmful outcome (NNTH) was 4 (95% CI=2–7). Furthermore, the LD group exhibited a lower risk of hypotension (RR=0.78, 95% CI=0.65–0.93) and nausea/vomiting (RR=0.71, 95% CI=0.55–0.93). Conversion to general anaesthesia occurred only in the LD group (two events). Neonatal outcomes (Apgar score, acid–base status) and clinical quality variables (patient satisfaction, surgical conditions) showed non-significant differences between LD and CD. This meta-analysis demonstrates that low-dose bupivacaine in spinal anaesthesia compromises anaesthetic efficacy (risk of analgesic supplementation: high grade of evidence), despite the benefit of lower maternal side-effects (hypotension, nausea/vomiting: moderate grade of evidence).
Regional anaesthesia is a major factor in patient safety during Caesarean delivery. Resurgence of spinal anaesthesia as a popular technique was possible due to the development of small-bore needles with pencil-point tips and has become the preferred method of anaesthesia for elective and for many emergency Caesarean deliveries if an epidural catheter is not already in situ. While effective surgical anaesthesia is the primary objective of the spinal technique, it must be accomplished while minimizing maternal and neonatal side-effects.
Although various factors influence the appropriate sensory nerve block for surgical anaesthesia, the local anaesthetic dose is the main determinant of its success. Anaesthesia textbooks recommend bupivacaine in a dose of between 12 and 15 mg. However, the use of this dose range has been associated with an incidence of maternal arterial hypotension of 69% to >80%, resulting in maternal and neonatal morbidity. A number of studies have sought an optimal dose of bupivacaine, but produced dissimilar findings with doses ranging from 5 to 20 mg. The use of a lower dose aims to decrease maternal side-effects (hypotension, intraoperative nausea/vomiting), reduce the time to discharge from the post-anaesthesia care unit, and improve maternal satisfaction. However, such a strategy could compromise the adequacy of anaesthesia, and require supplementary analgesia, with possible neonatal consequences and may require conversion to general anaesthesia, a situation known as a risk factor for anaesthesia-related maternal morbidity and mortality.
Recent narrative reviews have addressed the controversy of spinal bupivacaine in low dose (LD). Although useful, they are essentially descriptive and conclude with opinion-based recommendations. Systematic reviewing allows the efficient integration of the evidence due to explicit methods used to summarize the data, limiting bias and improving the accuracy of the conclusions, and thus providing a reliable source and basis that can be used for rational decision-making. We therefore conducted a systematic review of the literature and meta-analysis on the efficacy and adverse effects of spinal bupivacaine in LD compared with conventional dose (CD) for elective Caesarean delivery.
Abstract and Introduction
Abstract
Spinal anaesthesia is the preferred anaesthetic technique for elective Caesarean deliveries. Hypotension is the most common side-effect and has both maternal and neonatal consequences. Different strategies have been attempted to prevent spinal-induced hypotension, including the use of low-dose bupivacaine. We conducted a systematic search for randomized controlled trials comparing the efficacy of spinal bupivacaine in low dose (LD ≤8 mg) with conventional dose (CD >8 mg) for elective Caesarean delivery. Thirty-five trials were identified for eligibility assessment, 15 were selected for data extraction, and 12 were finally included in the meta-analysis. We investigated sources of heterogeneity, subgroup analysis, and meta-regression for confounding variables (baricity, intrathecal opioids, lateral vs sitting position, uterine exteriorization, and study population). Sensitivity analysis was performed to test the robustness of the results. In the LD group, the need for analgesic supplementation during surgery was significantly higher [risk ratio (RR)=3.76, 95% confidence interval (95% CI)=2.38–5.92] and the number needed to treat for an additional harmful outcome (NNTH) was 4 (95% CI=2–7). Furthermore, the LD group exhibited a lower risk of hypotension (RR=0.78, 95% CI=0.65–0.93) and nausea/vomiting (RR=0.71, 95% CI=0.55–0.93). Conversion to general anaesthesia occurred only in the LD group (two events). Neonatal outcomes (Apgar score, acid–base status) and clinical quality variables (patient satisfaction, surgical conditions) showed non-significant differences between LD and CD. This meta-analysis demonstrates that low-dose bupivacaine in spinal anaesthesia compromises anaesthetic efficacy (risk of analgesic supplementation: high grade of evidence), despite the benefit of lower maternal side-effects (hypotension, nausea/vomiting: moderate grade of evidence).
Introduction
Regional anaesthesia is a major factor in patient safety during Caesarean delivery. Resurgence of spinal anaesthesia as a popular technique was possible due to the development of small-bore needles with pencil-point tips and has become the preferred method of anaesthesia for elective and for many emergency Caesarean deliveries if an epidural catheter is not already in situ. While effective surgical anaesthesia is the primary objective of the spinal technique, it must be accomplished while minimizing maternal and neonatal side-effects.
Although various factors influence the appropriate sensory nerve block for surgical anaesthesia, the local anaesthetic dose is the main determinant of its success. Anaesthesia textbooks recommend bupivacaine in a dose of between 12 and 15 mg. However, the use of this dose range has been associated with an incidence of maternal arterial hypotension of 69% to >80%, resulting in maternal and neonatal morbidity. A number of studies have sought an optimal dose of bupivacaine, but produced dissimilar findings with doses ranging from 5 to 20 mg. The use of a lower dose aims to decrease maternal side-effects (hypotension, intraoperative nausea/vomiting), reduce the time to discharge from the post-anaesthesia care unit, and improve maternal satisfaction. However, such a strategy could compromise the adequacy of anaesthesia, and require supplementary analgesia, with possible neonatal consequences and may require conversion to general anaesthesia, a situation known as a risk factor for anaesthesia-related maternal morbidity and mortality.
Recent narrative reviews have addressed the controversy of spinal bupivacaine in low dose (LD). Although useful, they are essentially descriptive and conclude with opinion-based recommendations. Systematic reviewing allows the efficient integration of the evidence due to explicit methods used to summarize the data, limiting bias and improving the accuracy of the conclusions, and thus providing a reliable source and basis that can be used for rational decision-making. We therefore conducted a systematic review of the literature and meta-analysis on the efficacy and adverse effects of spinal bupivacaine in LD compared with conventional dose (CD) for elective Caesarean delivery.