Anaesthesia for Caesarean section and neonatal acid‐base status: a meta‐analysis*

Abstract

SummarySpinal anaesthesia is generally preferred for Caesarean section. Its superiority for the baby is often assumed. Umbilical artery acid-base status provides a valid index of fetal welfare. Twenty-seven studies reporting neonatal acid-base data with different types of anaesthesia were used to compare umbilical artery or vein pH and base deficit, using random-effect meta-analysis. Cord pH was significantly lower with spinal than with both general (difference: )0.015; 95% CI )0.029 to )0.001; 13 studies, 1272 subjects) and epidural anaesthesia (difference )0.013; 95% CI )0.024 to )0.002; 11 studies, 828 subjects). Larger doses of ephedrine contributed to the latter effect (p = 0.023). Sixteen studies reported a base deficit, which was significantly higher for spinal than for general (difference 1.109; 95% CI 0.434-1.784 mEq.l )1 ; seven studies, 695 subject) and epidural anaesthesia (difference 0.910; 95% CI 0.222-1.598 mEq.l ; seven studies, 497 subjects). Spinal anaesthesia cannot be considered safer than epidural or general anaesthesia for the fetus. In labour, regional analgesia has a more favourable effect on the newborn than systemic analgesia [1][2][3], a fact that tends to be neglected by consumers and carers alike. By contrast, it is widely accepted that regional anaesthesia for Caesarean section is preferable to general anaesthesia. Spinal anaesthesia is commonly considered both more practical and safer than other techniques for the mother, and is therefore widely used [4]. It is often assumed, similarly, that spinal anaesthesia for Caesarean section must be better for the baby than general or epidural anaesthesia. There are several reasons for this assumption.• General anaesthesia was shown in the 1970s to depress the Apgar score, although this is reversible and rarely significant by 5 min [5,6].• Maternal hypotension, which is believed to be detrimental to fetal wellbeing, can be minimised by appropriate vasopressor control. Cardiac output, however, is more likely to be impaired by spinal than by epidural anaesthesia [7], is rarely measured and may not be so easily corrected.• The doses of drugs required to induce spinal anaesthesia are small and are therefore unlikely to produce systemic effects in the baby. With the brief duration of anaesthesia before delivery of the baby, however, pharmacological fetal depression is likely to be less important than that following prolonged maternal administration of depressant drugs, as may occur during labour. It must be borne in mind, moreover, that drugs may affect the baby in two ways: firstly via a direct effect, resulting from placental drug transfer, which is transient even when general anaesthesia is used for Caesarean section, and clearly unimportant with spinal anaesthesia; and secondly, through an indirect effect resulting from maternal physiological or biochemical changes, which Anaesthesia, 2005, 60 , pages 636-653 .........................................................................................................................................

Emergency Caesarean section: best practice*

“…Preservative-free morphine is also available at an appropriate dilution (2 mg in 10 ml); 0.1 mg (0.5 ml of this solution) provides comparable postoperative analgesia to diamorphine 0.25 mg [23]. Obsessive maintenance of left-lateral tilt to offset aortocaval compression and prompt use of phenylephrine (now widely regarded as the vasopressor of choice) should mitigate the slight fetal acidosis that has been observed after spinal compared with epidural or general anaesthesia [24,25]. Preload (administration of fluid before spinal anaesthesia) has been superseded by 'coload' -a fluid bolus coinciding with the sympathetic blockade.…”

A randomised controlled trial comparing weight adjusted dose versus fixed dose prophylactic phenylephrine infusion on maintaining systolic blood pressure during caesarean section under spinal anaesthesia

“…Spinal anaesthesia is the preferred mode of anaesthesia for elective caesarean delivery 1,2 . Benefits include avoiding the risks involved during general anaesthesia such as difficult intubation and aspiration of gastric contents 3,4 .…”

Evidence-Based Obstetric Anesthesia: An Update on Anesthesia for Cesarean Delivery

“…Apgar and neonatal neurobehavioral scores are relatively insensitive measures of neonatal well-being, and umbilical cord blood gas and pH measurements may reflect an obstetric bias (indication for the cesarean delivery rather than differences in anesthetic techniques). Some previous studies have found that umbilical artery pH was greater in the neonate delivered with general anesthesia, but clinical parameters (e.g., Apgar score and the need for assisted ventilation) were better when regional anesthesia was used [28]. The acidemia found following regional anesthesia seems to be increased after spinal as compared to epidural anesthesia, but has not been related to any clinically significant neonatal complication [20,28].…”