1. Obstetric Anesthesia & Analgesia
Prepared by
Dr. Mahmoud Abdel-Khalek
August 2015

2. Physiologic changes of pregnancy
Physiologic and anatomic changes develop across many organ systems during pregnancy and the postpartum period
The Metabolic, hormonal and physical changes all have impact on anesthetic management
To the anesthesiologist, the most important changes are those that affect the respiratory and circulatory systems

3. Respiratory system
There is an increased risk of difficult or failed intubation in the parturient:
Mucosal vascular engorgement → airway edema and friability
Laryngoscopy may be impeded by the presence of large breasts

4. Respiratory system
Increased risk of pulmonary aspiration of stomach contents due to:
Upward displacement of the stomach
Decreased gastric motility and increased gastric secretions (Progesterone)
Incompetent gastro-esophageal junction

5. Respiratory system
With the apnea that occurs at induction of anesthesia, the parturient becomes hypoxic much more rapidly than the non-pregnant patient due to 2 main reasons:
Oxygen requirement has increased by 20% by term
Decrease of FRC, which serves as an “oxygen reserve” by 20% due to upward displacement of the diaphragm
Minute ventilation increases to 150% of baseline leading to a decrease in PaCO2 (32 mmHg)

6. CVS
Blood volume increases by 40% during pregnancy in preparation for the anticipated cc average blood loss during vaginal or Caesarian delivery, respectively
When the pregnant patient is in the supine position, the heavy gravid uterus compresses the major vessels in the abdomen leading to maternal hypotension and fetal distress (supine hypotensive syndrome)
Left lateral tilt, usually achieved with a pillow under the woman’s right hip, is an important positioning maneuver

7. PAIN PATHWAYS IN LABOUR AND CAESAREAN SECTION
The pain of the first stage of labour is referred to the spinal cord segments associated with the uterus and the cervix, namely T10, 11, 12 and LI
Pain of distension of the birth canal and perineum is conveyed via S2-S4 nerves

8. PAIN PATHWAYS IN LABOUR AND CAESAREAN SECTION
When anesthesia is required for caesarean section, all the layers between the skin and the uterus must be anaesthetized
The most sensitive layer is the peritoneum, and therefore the block should extend up to at least T4 and also include the sacral roots (S1-S5)

9. Anatomy& Physiology of Airway in Pregnancy
Incidence of difficult intubation in term parturients:
1 in 300 cases, compared with 1 in 2200 in the non-pregnant population

10. Normal labour The first stage of labour
Cervix effaces then cervical dilatation begins
Rate of cervical dilatation:
Primigravida: 1 cm/ hour
Multigravida: 2 cm/ hour
Routine observations:
Fetal HR every 15 minutes
Maternal pulse and BP every 30 minutes
Temperature 4-hourly
Urine analysis at each emptying of bladder

11. Normal labour The second stage of labour
Commences at full dilatation of the cervix and terminates at the delivery of the baby
If prolonged more than 1 hour the fetus may become acidotic
At the delivery of anterior shoulder, IM oxytocin is given to hasten the delivery of the placenta and to stimulate the uterine contraction

12. Normal labour The third stage of labour
The complete delivery of the placenta& membranes& contraction of the uterus
Placental blood flow (15% of CO) redistribute to maternal circulation and may precipitate heart failure immediately postpartum in women with cardiac disease

13. Fetal monitoring The most commonly used:
Serial ultrasonography
Serial Doppler flow studies
Cardiotocograph (CTG) monitoring
The degree of urgency for the delivery depends on the condition of the fetus
Routine methods to monitor fetal well-being:
Fetal heart auscultation, Fetal heart cardiotocography, Color of the liquor& Fetal blood sampling
Normal fetus baseline heart rate: beats per minute

14. Fetal monitoring
The ability of the fetus to maintain oxygenation is diminished with each uterine contraction
The normal CTG trace simultaneously records fetal heart sounds and uterine contractions
Decelerations:
Early: Benign
Variable: may or may not hypoxemia
Late: Pathological
Abnormal trace is an indication for fetal blood sampling for pH which is more accurate assessment of fetal well-being

15. Fetal Monitoring
Color of the liquor may be monitored when the membranes are ruptured
The liquor color is observed for the presence of mechonium which may indicate fetal hypoxia
The appearance of new thick mechonium is an indication for urgent delivery
If mechonium is aspirated into the lungs of the neonate severe lung damage may ensue

16. Fetal monitoring Values for fetal pH: pH > 7.25: Normal
pH : borderline to be repeated 30 minutes later
pH < 7.20: significant acidosis requiring urgent delivery of the baby

17. Urgency of CS delivery Grade 1. Emergency:
Immediate threat to life of woman or fetus
Grade 2. Urgent:
Maternal or fetal compromise which is not immediately life threatening
Grade 3. Scheduled:
Needing early delivery but no maternal or fetal compromise
Grade 4. Elective:
At a time to suit the patient and the maternity team

18. GI physiology and antacid therapy
During pregnancy an increase in progesterone a decrease in the tone of the lower esophageal sphincter and, combined with the increased abdominal mass, results in an increased possibility of regurgitation and pulmonary aspiration of gastric contents
The pH of the gastric contents is low, and therefore there is an increased incidence of heartburn in pregnancy
Gastric emptying is not delayed during pregnancy but is delayed in labour, especially by pain, anxiety and opioids

19. GI physiology and antacid therapy
Mendelson Syndrome
Mendelson first described the syndrome of aspiration of gastric contents in 1946 leading to chemical pneumonitis

20. GI physiology and antacid therapy
Recommendations:
Withhold oral feeding during labour& give parenteral administration
Use of local anesthetic technique where indicated and feasible
Alkalinization and emptying of stomach contents before GA
Competent administration of general anesthesia, with appreciation of the dangers of aspiration during induction and recovery
Adequate delivery room equipment, including transparent masks, suction, laryngoscope and tilting table
Anesthetist to remain with the patient until return of laryngeal reflexes

21. Reducing the acidity of the stomach contents
Emergency surgery:
immediately before surgery:
30 mL 0.3 molar sodium citrate orally
50 mg ranitidine by slow IV injection
10 mg metoclopramide IV injection
Elective surgery:
150 mg ranitidine orally
10 mg metoclopramide

22. Pain& Pain Relief in labour
It is only in the last 150 years that effective methods of pain relief have been available
Pain of labour is amongst the most severe in the human experience of pain
Studies assessing pain of labour in primigravidae:
9.2% very mild
29.5% mild
37.9% moderate
23.4% severe

23. The effect of Pain& Analgesia on the mother and fetus
A long painful labour may → an exhausted, frightened and hysterical mother incapable of decision making
Pain compromises placental blood flow& renders uterine contractions less effective
Increase catecholamines secretions results in increased myocardial work and arterial pressure and may compromise blood flow to the placenta by peripheral VC
Activation of adrenocortical hormones may adversely affect electrolyte, carbohydrate& protein metabolism

24. The effect of Pain& Analgesia on the mother and fetus
The Ideal Analgesic for Labour:
Rapid-onset , Excellent pain relief in both 1st & 2nd stages without risk or side-effects to mother or fetus
Retain the mother's ability to mobilize and be independent during labour
There is no ideal analgesic at the present time
It can be closely approached by spinal or epidural techniques which provide effective analgesia while preserving motor function to a large degree

25. The effect of Pain& Analgesia on the mother and fetus
The Ideal Analgesic for Labour:
Effective epidural (or spinal) analgesia reverses the adverse physiological effects of labour pain listed above by blocking the psychological and biochemical stress response, resulting in improved maternal well-being and placental perfusion

26. labour analgesia Parenteral (systemic) analgesia Inhalation analgesia
Regional analgesia for labour

27. Parentral Analgesia
Pethidine is given by intramuscular injection and the maximum effect is seen about 1 h after administration
The analgesic effects are variable and pethidine may also cause significant side-effects:
maternal sedation, nausea and vomiting, dysphoria and inhibition of gastric emptying
Fetal respiratory and neurobehavioural depression

28. Inhalation analgesia
Entonox, which is 50% nitrous oxide and 50% oxygen premixed in cylinders
Entonox is administered usually via an on-demand valve with a face mask or mouthpiece
Although Entonox is a reasonably effective analgesic, many women feel faint and nauseated and may vomit or become out of control

29. Regional Analgesia for Labour
Epidural and Subarachnoid Analgesia
This is the most effective form of analgesia in labour, with up to 90% women reporting complete or near-complete pain relief
However, it is invasive and patients require careful monitoring

30. Indications for Epidural Analgesia
In addition to relief of pain and distress, there are several indications for which epidural analgesia may be helpful in securing a good outcome from labour

31. Technique of Epidural Analgesia
Preparation
Informed consent
Intravenous cannulation
Baseline ABP recording
Urinary bladder should be emptied
Clothing
Positioning: sitting or lateral (See table)

32. Technique of Epidural Analgesia

33. Conduct of Epidural

34. Conduct of the Epidural

35. Regional Anesthesia for the Parturient
Obstetric indications CS
Forceps and ventouse delivery
Retained placenta
Suturing of trauma to the birth canal

36. Elective CS Regional anesthesia is the technique of choice
The woman should be warned about:
Hypotension
Nausea and vomiting
Post dural puncture headache (PDPH)
Possibility of imperfect block
Available techniques:
Spinal anesthesia
Epidural anesthesia
Combined spinal- Epidural anesthesia

37. Emergency CS Topping up of an existing epidural General Anesthesia
Spinal Anesthesia

38. Complications of Regional Anesthesia in Obstetrics
Shearing of the epidural catheter
Unlikely to cause problems (aseptic, inert)
Post dural puncture headache
Incidence: %
Bed rest, IV and oral fluids
Simple analgesics
Caffeine infusion
ADH?
Blood patch

39. Complications of Regional Anesthesia in Obstetrics
Backache
Epidural hematoma
Very rare but potentially disastrous complication
Signs:
Severe back pain
Prolonged profound motor weakness for more than 6 hours
Sudden onset of incontinence
Requires prompt neurosurgical intervention
Epidural abscess or meningitis
Compression of spinal cord and blood supply (paraplegia)

40. Complications of Regional Anesthesia in Obstetrics
Systemic toxic reaction
Overdose of LA
Hypotension
Defined as 25% decrease of systolic or MAB OR absolute decrease of 40 mm Hg
Dizziness, nausea
Vasopressors e.g. phenylephrine, Ephedrine
Neurological deficit
Reassurance that recovery will occur in 3- 6 months
Delivery may be causative and not the epidural

41. General Anesthesia for the parturient
Safety of anesthesia has increased in obstetrics:
Increasing use of epidural in labour
Increasing use of regional anesthesia for operative delivery
Improved teaching
Improved assistance to the anesthetist
Currently only 5- 10% of CS In the UK are performed under GA

42. General Anesthesia for the parturient
Indications
Extreme emergency: severe fetal distress, maternal hemorrhage
If regional is contraindicated
Patient refuses regional

43. General Anesthesia for the parturient

44. General Anesthesia for the parturient

45. Emergencies in Obstetrics Anesthesia
Hemorrhage
Failed intubation
Pre-eclampsia and eclampsia
Total spinal block
Amniotic fluid embolism
Maternal r neonatal resuscitation

46. Failed Inubation
High incidence of airway difficulties in obstetric patients (approximately 1 in 300 compared with 1 in 2220 in non-pregnant patients)
Causes:
Swollen upper airway mucosa
swollen and engorged breasts and full dentition
The decreasing use of general anesthesia in obstetrics may lead to a relative lack of experience in this technique with increased anxiety for both junior and senior anesthetists

47. Failed Inubation
Call for help when unexpected difficulty with laryngoscopy or intubation arises and to avoid repeated attempts at intubation without maintaining oxygenation
The placement of a laryngeal mask airway (LMA) may facilitate ventilation and, if used, cricoid pressure should be applied continuously

48. Failed Intubation

49. Thank you