Fetal Oxygenation

1. Fetal Oxygenation

2. Oxygen Oxygen Oxygen Three most important things are:

3. What this talk is about….. • Oxygen has always been considered to be good…… • Recent findings with free radicals • May be good or bad • Clarify the issues surrounding oxygen & obstetric anaesthesia

4. Supplementary oxygen for elective Caesarean section Regional Anaesthesia

5. Objective • Respiratory effects • Deterioration after regional anaesthesia • Improved oxygen transfer to fetus • Better storage for adverse events • Prolonged uterine incision delivery time • Long time to spontaneous breathing

6. Maternal Respiratory Effects Spinal Anaesthesia: • Denser Motor Block • Respiratory muscles • Concurrent use of opioids • Respiratory drive

7. Summary of findings

8. Maternal Respiratory Effects Deterioration (15 - 30%) Kelly MC, Fitzpatrick KT, Hill DA. Respiratory effects of spinal anaesthesia for caesarean section. Anaesthesia 1996; 51: 1120-2

9. Maternal Respiratory Effects Conn,D.A, Moffat,A.C., McCallum,G.D, Thorburn,J.Changes in pulmonary function tests during spinal anaesthesia for caesarean section. Int Journal of Obst Anaesthesia. 1993 (2) p12-4

10. Maternal Respiratory Effects • Deterioration in respiratory functions • May lead to poor coughing • No maternal desaturation • Supplementary oxygen not necessary for this purpose

11. What about fetal oxygenation?

12. Placental Circulation • Concurrent Exchange (Fetal oxygen reflects maternal uterine veins) • High metabolic rate • ‘Functional shunting’ • Large gradient of PO2 between maternal and fetus circulation

14. Methods • 44 parturients elective CS • Randomly - 21 vs 60% (Ventimask) • Arterial catheter • Blood gas analysis (5min) intervals • Umbilical blood gases at delivery • Assays for Lipid Peroxides

15. Relationship of Maternal Arterial & Umbilical Venous Blood Gases

16. 20% Umbilical Blood Gases

17. Maternal Lipid Peroxidation +P<0.05 * P<0.01

18. Fetal Lipid Peroxidation

19. Umbilical Lipid Peroxides

20. Summary • 60% supplementary oxygen increases the partial pressure of oxygen in the fetus • However, this induces lipid peroxidation in the mother and fetus • In low risk cases, oxygen supplement is not necessary

21. What if the U-D interval is prolonged?

22. Prolonged Uterine incision to delivery interval (UD) • Uterine incision disrupts blood flow • Placental hypoperfusion • Associated with fetal acidosis, low Apgar scores • Assumption that supplementary oxygen may be beneficial Bader AM, Datta S, Arthur GR, Benvenuti E, Courtney M, Hauch M: Maternal and fetal catecholamines and uterine incision-to-delivery interval during elective cesarean2. Obstet Gynecol 1990; 75: 600-3 Datta S, Ostheimer GW, Weiss JB, Brown WU, Jr., Alper MH: Neonatal effect of prolonged anesthetic induction for cesarean section. Obstet Gynecol 1981; 58: 331-5

24. Methods • Recruited 204 patients • Randomly – 21% vs 40% vs 60% • Umbilical blood gas and co-oximetry • UD interval noted • Study completed when 3 groups have at least 13 patients with prolonged UD interval

25. 12% same Fetal Oxygenation

26. Fetal Outcomes

27. Summary • Prolonged UD interval was NOT associated with • Fetal acidosis • Low Apgar scores • Supplementary oxygen did not improve the oxygen content

29. General Anaesthesia and Oxygen

30. Issues involved Volatile Anaesthesia • Fetal depression • Uterine relaxation & blood loss Oxygen • Fetal oxygenation • Maternal awareness • Placental vasoconstriction • Premature closure of ductus arteriosus

34. Follow up study Lipid peroxidation

35. Maternal Isoprostane

36. Maternal Isoprostane

37. Fetal Oxygen Indices

38. Fetal Isoprostane • Significantly higher !! • Mean (SD) = 135 (67) μmol. l-1 (Air) • Mean (SD) = 403 (100) μmol. l-1(Oxygen)

39. Fetal Isoprostane • PRE OXYGENATION • Duration should be limited

40. Summary Volatile Anaesthesia • MAC Equivalent of volatile agents should be used • No difference Uterine tone & blood loss • Apgar scores or Fetal depression Oxygen • Fetal oxygenation increased >50% used • MAC Equiv – No maternal awareness • Lipid peroxidation induced by preoxygenation

41. Emergency Caesarean section Regional Anaesthesia

42. Fetal oxygen during labour • Episodic blood flow • Ischaemic during uterine contraction • Followed by reperfusion • Hypoxic environment • Role of supplementary oxygen?

43. Pros and cons of Oxygen • Improvement in fetal oxygen • Most of fetal distress are hypoxia related • Decided for surgery thus only for short duration • Exacerbation of ischaemia reperfusion injury • UNPROVEN • Augment generation of free radicals • Depletion of antioxidants

45. Yamada T, Yoneyama Y, Sawa R, et al. Effects of maternal oxygen supplementation on fetal oxygenation and lipid peroxidation following a single umbilical cord occlusion in fetal goats. J.Nippon Med.Sch 2003; 70: 165-71

46. Implication - Supplementary oxygen • Potentiates Ischaemia reperfusion injury • Augments lipid peroxidation • Further research - to clarify the role of Supplementary oxygen in Emergency Caesarean section

47. The Effects of Maternal Oxygen Therapy during Emergency Caesarean Section. RGC Competitive Earmarked Research Grant

48. Kim S. Khaw, Warwick D. Ngan Kee, Chi C. Wang, Floria F. Ng, MichaelS. Rogers. .Supplementary Oxygen for Emergency Cesarean Section under Regional Anesthesia. Anesthesiology 2004; 101: A1229

49. Methods • Stratified randomized double blinded study • Urgency (<30 min for decision - delivery) • Pre-consented - breathe 21% or 60% oxygen • Primary outcome measures • Umbilical venous oxygen content • Secondary outcome measures • Fetal well being – UA pH, Apgar Scores • Umbilical arterial isoprostane level

50. Results • 125 participated • 88 cases urgent • 37 cases emergent • Demographics of mother and fetus similar • No maternal desaturation requiring intervention • Similar incidences of hypotension • No babies required NICU admission