Obstetric Analgesia & Anesthesia

1. Obstetric Analgesia & Anesthesia

2. PHYSIOLOGIC AND ANATOMIC CHANGES DURING PREGNANCY AND LABOR-ANESTHETIC IMPLICATIONS

3. Innrvation

4. Innrvation

6. Causes of Pain During Labour • Myometrial hypoxia • Stretching of the cervix • Pressure on the nerve ganglia adjacent to the cervix and vagina • Traction on the tubes, ovaries and peritoneum • Traction and stretching of the supporting ligaments • Pressure on the urethra, bladder and rectum • Distention of the muscles of the pelvic floor and perineum

7. Objectives and Methods • MOTHER: • Relief of pain • By relieving pain the changes of ventilation, circulation, hormonal function that ordinarily accompany pain can be controlled • Freedom from fear • Safe and comfortable delivery • INFANT: • To be given a favorable physiologic milieu for delivery • To use techniques not associated with fetal depression or long term poor outcome • OBSTETRICIAN: • Reduction of pressure from patient & relatives to do something prematurely • Optimum conditions at delivery

8. Criteria for ideal method • The method must ensure that: • The health of the mother is not endangered • The newborn should not be depressed at delivery. Drugs cross the placenta • The technique effectively controls pain • The efficiency of uterine contractions is not decreased • The ability of the patient to cooperate intelligently with the medical and nursing staff is maintained • There is no need for operative interference because of anesthesia • The method is relatively simple to use

9. Training for childbirth “to prepare a woman for labor and delivery so that she approaches the end of her pregnancy with knowledge, understanding and confidence rather than apprehension and fear” • Aims of perinatal training: • Counteract apprehension of young women caused by exaggerated tales of horror • The patient is given an opportunity to gain confidence • Exercises are taught which strengthen certain muscles and relaxes others • The patient is trained in breath control • The patient told about labor pains and analgesic options • Patient to choose the method most suitable for her away from others experiences • Emphasis on the fact that most labors are normal

11. Relief of Pain During Pregnancy • Simple analgesia: • Aspirin • Paracetamol • Non-steroidal Anti-Inflammatory Drugs • Early in pregnancy • Third trimester • Opioid analgesics: • Codeine • Pethidine/morphine

12. Relief of Pain During First Stage of Labor • Non-pharmacological: • Breathing exercise • TENS machine • Inhalation anesthesia: “Nitrous Oxide” • Insoluble in blood, rapid induction and recovery • Rapidly transported to maternal tissue, placenta and fetus • Effective when taken during contractions • Nontoxic • NO 50:50 O2, decreasing the chance of maternal hypoxia • Prolonged use may lead to neonatal depression • No/little effect on labor

13. Relief of Pain During First Stage of Labor • Systemic medications “Narcotics”… alleviate pain. If given in large doses in the latent phase < contractions & cx dilatation. When labor established, relief of pain and anxiety make the uterine contractions more efficient • S.Effect: resp. depression, ortho hypotenb, <gastric motility, nausea & vomitting. Affects neonatal neurobehavior • Morphine: 0.1mg/kg 3-4 hrs peak effect1-2 hrs (I.m.)/20 min (I.v.). Duration 4-6 hrs. if given< 3 hrs before delivery…. Fetus affected • Demerol(meperidine, pethidine): synthetic narcotic with atropine-like action. 1mg/kg 3-4 hrs peak effect 40-50 min(I.m.)/5-10 min (I.v.). Duration 3-4 hrs. the greatest effect on the fetus reached within 1.5 hrs after I.m. Narcotic effects on the newborn are best antagonised with Naloxone 5-10 micg/kg

14. Relief of Pain During First Stage of Labor • Paracervical block: XXXXXXXXXX • Lumber Epidural block: • Injecting of Marcaine 0.25-0.5% or others in a continuous infusion • Advantages: • Almost pain free labor • Can be kept as long as desired • Level of analgesia can be controlled • Mother is alert and cooperative. Retains ability to bear down. If forceps req. • Can be used when converting to C/S • Minimal effect on the fetus!!!!!!!!!!!!!!!!!!!

15. Disadvantages: • Might mask the strength of contractions esp. with syntocinone • 10% significant hypotension if lie supine. Epidural anesthesia>>20mm Hg drop in syst or diast in 30% of pnt. Due to: • Sympathetic vasomotor blockade >>> 20% drop in arteriolar resistance • Increased venous capacitation and pooling>>>decreased in venous return and COP • Uterine pressure on aorta and vena cava To prevent hypotension: • Infuse 1 L RL or Saline • Wedge under right hip to displace the uterus to the left and reduce vascular pressure • Use Ephedrine as vasopressor if required • Intravascular injection: convulsion and hypotension • If dura is punctured>> headache. Subarachnoid >>>massive motor block, hypotension and respiratory distress

16. Disadvantages: • Fetal heart rate patterns may be affected • Infection at site of injection,,rare • Backache • Neurological side effect debatable • Might affect uterine contractions needing oxytocin • If large dose, would paralyze pelvic floor>> failure to rotate and mother not bearing down due to lack of sensation>>> instrumental delivery • Contraindications: • Drug allergy • Skin infection • Coagulopathy(severe PET,active Hg) • Severe supine hypotension • Certain cardiopulmonary diseases

18. Relief of Pain During Second Stage of Labor • Inhalation Anesthesia: • Halothane, Enflorane, Isoflorane • Intravenous Anesthesia: • Thiopentone, Ketamine • Not routinely used in every days work. Mainly in private sector. Consider side effect of general anesthesia and need to be administered by anesthetist.

19. Relief of Pain During Second Stage of Labor • Local Anesthesia: • Advantages • Disadvantages 1. Direct infiltration >>>>>>>

20. Relief of Pain During Second Stage of Labor 2. Pudendal Nerve Block

21. Anesthesia for Cesarean Section • Topped up ongoing epidural • Spinal block anesthesia • General anesthesia >90% of C/s in UK

23. Epidural Spinal Onset 10---30 min 5---10 min Duration & effect Continuous Single shot. effect lasts for 2 hours Success rate Higher incidence of patchy, one-sided blocks Block quality Less-dense sensory block More dense sensory block Less motor block More motor block Hypotension Same incidence, slower onset Same incidence, more rapid onset Risk of PDPH Approximately 1% Approximately 1% Risk of systemic local anesthetic toxicity Inadvertent intravenous injection may cause systemic toxicity Dose too small to cause systemic toxicity if inadvertently injected intravascular Risk of total spinal Possible with inadvertent subarachnoid injection or “overdose” epidural injection Less likely because of small drug dose Post---cesarean delivery analgesia Continuous or single-shot Single-shot only Effects on the fetus Greater drug exposure Minimal drug exposure

24. Block Clinical Use Advantage Disadvantages/Side Effects/Complications/ Spinal (saddle block) Instrumental vaginal delivery anesthesia Rapid onset analgesia with perineal motor block Single shot, not continuous Caudal block Labor and delivery analgesia Another access to epidural space Technically more difficult than lumbar epidural Useful for patients with lumbar spine fusion Requires large volume of local anesthetic to provide labor analgesia to T10 level Paracervical block Early---mid 1st stage labor analgesia No motor block Not continuous Risk of fetal bradycardia Lumbar sympathetic block Early---mid 1st stage labor analgesia No motor block. Speeds labor Not continuous. Requires bilateral injections Useful for patients with lumbar spine fusion Technically more difficult to learn Pudendal block 2nd stage analgesia; instrumental vaginal delivery anesthesia Performed by obstetrician before delivery Not continuous Complications rare Perineal infiltration Episiotomy or repair anesthesia Technically simple No motor relaxation Performed by the obstetrician as needed Complications rare

25. General Anesthesia • Inhalation Anesthesia: • Halothane, Enflorane, Isoflorane • Intravenous Anesthesia: • Thiopentone, Ketamine Can operate in relaxed state in difficult cases. If >3 min before delivering baby >>drowsy • Aspiration of vomitus during anesthesia. Commonest morbidity • Methods to prevent its occurrence • Failed intubation • Mendelson Syndrome