Obstetric Topic 24. Preparation for delivery. Obstetric anesthesia

I. Preparation for Delivery

True vs False Labor

• True labor: regular contractions, intervals shorten, intensity increases, low back + abdominal pain, progressive cervical dilatation/effacement.
• True labor pain: not relieved by sedation/rest.
• False labor / Braxton Hicks: irregular contractions, long intervals, unchanged intensity, mainly lower abdominal discomfort, no cervical change.
• False labor pain: often relieved by rest/sedation.
• Normal labor: term singleton, vertex presentation, spontaneous vaginal birth, no maternal/fetal complication.

Initial Maternal Evaluation

• History: obstetric history, medical/surgical disease, allergies, medications, previous cesarean/uterine scar.
• General exam: skin, edema, height/weight, abdominal scars.
• Vitals: BP, pulse, respiratory rate, temperature.
• Heart and lung examination.
• Urinalysis: protein, glucose, ketones, infection signs.
• Check records/labs: blood group/Rh, CBC, infection screening if missing.

II. Fetal Presentation and Position

Leopold Maneuvers

1. Fundal grip: palpate fundus → hard round part = head; soft irregular part = breech.
2. Umbilical grip: palpate both sides → smooth firm side = fetal back; irregular mobile parts = extremities.
3. Pawlik's grip: grasp lower abdomen above symphysis → identify presenting part and engagement.
4. Pelvic grip: examiner faces feet; palpate lower uterus → confirm presenting part, attitude and descent.

Vaginal Examination and Fetal Monitoring

• Assess cervix: dilation, effacement, position, consistency.
• Assess membranes: intact/ruptured; after ROM exclude cord prolapse.
• Assess presentation/position: in vertex, palpate sagittal suture and anterior/posterior fontanelles.
• Assess station: presenting part relative to ischial spines.
• Avoid digital vaginal examination if placenta previa/low placenta is possible and location is unknown.
• Fetal heart auscultation or CTG; CTG especially for high-risk labor.
• Ultrasound: use if Leopold/vaginal exam is uncertain, especially obesity, rigid abdominal wall, abnormal lie or unclear placenta.

III. Obstetric Analgesia and Anesthesia

General Principles

• Goal: effective maternal pain relief with minimal maternal, fetal and labor-progress effects.
• Non-drug options: emotional support, breathing, massage, hydrotherapy, TENS.
• Pain pathways: T10-L1 uterus/cervix; S2-S4 pudendal nerve for lower vagina/perineum.
• Maternal request is sufficient indication for labor analgesia if no contraindication.

Regional / Neuraxial

• Epidural analgesia: catheter into lumbar epidural space; local anesthetic ± opioid (bupivacaine/ropivacaine ± fentanyl).
• Use: 1st and 2nd stage labor; can be topped up for cesarean if adequate.
• Onset: slower, adjustable and continuous.
• Side effects: hypotension, nausea, motor block, urinary retention, fever, post-dural puncture headache if accidental dural puncture.
• Spinal anesthesia: single injection into subarachnoid space, usually L3-L4 or L4-L5.
• Use: elective/urgent cesarean; rapid dense block but limited duration.
• Side effects: rapid hypotension, post-dural puncture headache, high spinal block if excessive spread.
• Combined spinal-epidural: rapid spinal onset + epidural catheter for continuation.

Local, Opioid and General Anesthesia

• Pudendal nerve block: S2-S4; perineal pain, episiotomy, instrumental delivery when no epidural.
• Local infiltration: episiotomy or laceration repair.
• Parenteral opioids: useful early; cross placenta → neonatal respiratory depression risk.
• Nitrous oxide: self-administered inhalational analgesia where available; maintain verbal contact.
• General anesthesia: emergency cesarean, failed regional anesthesia, or contraindication to regional anesthesia.
• Risks of general anesthesia: aspiration, difficult airway, maternal and fetal/neonatal respiratory depression.

IV. Contraindications and Practical Choice

Contraindications to Regional Anesthesia

• Absolute/major: patient refusal, coagulopathy/thrombocytopenia, anticoagulation not safely timed, local infection at puncture site, severe hypovolemia/ongoing bleeding, raised intracranial pressure from mass lesion.
• Relative: severe aortic stenosis/selected cardiac lesions, severe spinal deformity or previous spine surgery, systemic infection unless treated/stable.

Practical Exam Choice

• Vaginal delivery analgesia: epidural most common.
• Elective cesarean: spinal anesthesia usually preferred.
• Emergency cesarean: general anesthesia if no time for neuraxial, regional failed, or regional contraindicated.
• Episiotomy/repair: pudendal block or local infiltration if neuraxial absent/inadequate.