Peterborough, UK
It is a common misconception amongst anaesthetists who continue to administer supplementary oxygen to mothers during regional anaesthesia, that it does no harm but might possibly do some good.5 However, evidence to support this practice is lacking. Drs Mandal and Gulati have highlighted the potential detrimental effects that hypotension may have on fetal well-being. Surely the correct approach to this is to improve our management of hypotension,2 and we have provided some clues on how this may be achieved.6 Specifically, we showed that, in patients who received neither supplementary oxygen nor volume expansion, maternal and fetal hypoxia did not occur to any important degree when maternal blood pressure was maintained using a liberal infusion of phenylephrine.6
In our previous work, we found that administration of high-concentration oxygen during elective Caesarean section resulted in maternal and fetal lipid peroxidation, but achieved only a marginal increase in umbilical venous that was not clinically important.4 As a result, we discontinued the practice of giving oxygen to uncomplicated cases. Nevertheless, there remained a concern that this overlooked the potential benefit of oxygen in the event that the uterine incision-to-delivery (UD) interval is prolonged. Our current study1 shows that this concern is unfounded: despite earlier work that showed that a prolonged UD interval was associated with fetal acidosis,7 8 we found no benefit from administration of oxygen 60% to the mother when the UD interval was >180 s.
We believe that clinical practice should be evidence-based. In the absence of data to support any benefit from maternal oxygenand the possibility that there may even be potential harm from increased free radical activity4we stand by our recommendation that routine administration of supplementary oxygen during uncomplicated elective Caesarean section under regional anaesthesia is not necessary.
Hong Kong, China
References
1 Khaw KS, Ngan Kee WD, Lee A, et al. Supplemtary oxygen therapy for elective Caesarean section under spinal anaesthesia: useful in prolonged uterine incision-to-delivery interval. Br J Anaesth 2004; 92: 51822
2 Riley ET. Spinal anaesthesia for Caesarean delivery: keep the pressure up and don't spare the vasoconstrictors. Br J Anaesth 2004; 92: 45961
3 Shnider S, Levinson G. Anesthesia for Cesarean section. In: Shnider S, Levinson G, eds. Anesthesia for Obstetrics, 3rd Edn. Williams and Wilkins: Philadelphia, 1993; 217
4 Khaw KS, Wang CC, Ngan Kee WD, Pang CP, Rogers MS. Effects of high inspired oxygen fraction during elective caesarean section under spinal anaesthesia on maternal and fetal oxygenation and lipid peroxidation. Br J Anaesth 2002; 88: 45
5 Backe SK, Lyons G. Oxygen and elective Caesarean section. Br J Anaesth 2002; 88: 45
6 Ngan Kee WD, Khaw KS, Ng FF, Lee BB. Prophylactic phenylephrine infusion for preventing hypotension during spinal anesthesia for cesarean delivery. Anesth Analg 2004; 98: 81521
7 Bader AM, Datta S, Arthur GR, Benvenuti E, Courtney M, Hauch M. Maternal and fetal catecholamines and uterine incision-to-delivery interval during elective Cesarean. Obstet Gynecol 1990; 75: 6003[Abstract]
8 Datta S, Ostheimer GW, Weiss JB, Brown WU, Jr, Alper MH. Neonatal effect of prolonged anesthetic induction for Cesarean section. Obstet Gynecol 1981; 58: 3315[Abstract]