Physiology of delivery. Analgesia in labor. Korda I.

Labor Labor is the physiologic process by which a fetus is expelled form the uterus to the outside world. It involves the sequential integrated changes in the uterine decidua, and myometrium. Changes in the uterine cervix tend to precede uterine contractions Dilatation: the enlarging of the cervix to 10 centimeters. Effacement: the thinning of the cervix. Your cervix starts out being two inches long, and 50% effaced would be a 1 inch cervix.

To push the fetus through the birth canal Labor - Mechanics Uterine contractions have two major goals: To dilate cervix To push the fetus through the birth canal Success will depend on the three P’s: Powers Passenger Passage

Power Uterine contractions Power refers to the force generated by the contraction of the uterine myometrium Activity can be assessed by the simple observation by the mother, palpation of the fundus, or external tocodynamometry. Contraction force can also be measured by direct measurement of intrauterine pressure using internal manometry or pressure transducers.

Power There is no specific criteria for adequate uterine activity Generally 3-5 contractions in a 10 minute period is considered adequate labor

Passenger Passenger =fetus Fetal variables that can affect labor: Fetal size Fetal Lie – longitudinal, transverse or oblique Fetal presentation – vertex, breech, shoulder, compound (vertex and hand), and funic (umbilical cord). Attitude – degree of flexion or extension of the fetal head Position Number of fetuses Presence of fetal anomalies – hydrocephalus, sacrococcygeal teratoma

Cervical effacement and dilation

Station -5 is a floating baby, Station – degree of descent of the presenting part of the fetus, measured in centimeters from the ischial spines in negative and positive numbers. -5 is a floating baby, 0 station is said to be engaged in the pelvis, and +5 is crowning.

Passage Passage = Pelvis Consists of the bony pelvis and soft tissues of the birth canal (cervix, pelvic floor musculature) Small pelvic outlet can result in cephalopelvic disproportion Bony pelvis can be measured by pelvimetry but it not accurate and thus has been replaced by a clinical trial of labor

Passage www.uptodate.com

The Stages of Labor First Stage Interval between the onset of labor and full cervical dilation Two phases: Latent phase – onset o f labor with slow cervical dilation to ~4 cm and variable duration Active phase – faster rate of cervical change, 1-1.2 cm /hour, regular uterine contractions

The Labor Curve First stage - A: latent phase; B + C + D: active phase; B: acceleration; C: maximum slope of dilation; D: deceleration; E: second stage.

Labor Freidman’s curve is a good guideline for expected progression in labor and therefore helpful to note abnormal labor patterns. Labor NulliG MultiG 1st Stage Active phase Duration 6-18 h 2-10 h Dilation ~1 cm/h ~1.5 cm/h Arrested >2 h >2h 2nd Stage 0.5-3 h 5-30 min 3rd Stage 0-30 min

Fig 1: An idealized labor pattern Fig 1:  An idealized labor pattern.  The normal patterns of cervical dilation (solid line) and descent (broken line) as they are traced against elapsed time in labor. The distinctive phases of the first stage are shown. The active phase comprises the interval from the onset of the acceleration phase to the beginning of the second stage.

Labor – Second Stage Interval between full cervical dilation to delivery of the infant. Characterized by descent of the presenting part through the maternal pelvis and expulsion of the fetus. Indications of second stage: Increased maternal show Pelvic/rectal pressure Mother has active role of pushing to aid in fetal descent.

Labor – Second Stage Molding is the alteration of the fetal cranial bones to each other as a result of compressive forces of the maternal bony pelvis. Examining the fetal head during the second stage may become difficult due to molding Caput is the localized edematous area on the fetal scalp caused by pressure on the scalp by the cervix. PrimiG – 0.5-3 h; mulitG 0-30min

Suctioning the nasopharynx Cut between the clamps Clamp the umbilical cord

Labor – Third Stage Placental separation and delivery. The time from fetal delivery to delivery of the placenta Signs of placental separation: a. The uterus becomes globular in shape and firmer. b. The uterus rises in the abdomen. c. The umbilical cord descends three (3) inches or more further out of the vagina. d. Sudden gush of blood.

Labor – Third Stage Placenta is delivered using one hand on umbilical cord with gentle downward traction. Other hand on abdomen supporting the uterine fundus. Risk factor for aggressive traction is uterine inversion. Obstetrical emergency!! Normal duration between 0-30 min for both PrimiG and MultiG

Inspect the placenta for completeness

AMTSL = Active management of third stage of labour AMTSL = Active management of third stage of labour. RP = retained placenta. CCT = controlled cord traction. Hb = Haemoglobin. BP = Blood pressure. MRP = Manual removal of placenta. Hb = haemoglobine.

Labor – Fourth Stage Refers to the time from delivery of the placenta to 1 hour immediately postpartum Blood pressure, uterine blood loss and pulse rate must be monitor closely ~ 15 minutes High risk for postpartum hemorrhage from: Uterine atony, retained placental fragments, unrepaired lacerations of vagina, cervix or perineum. Occult bleeding may occur – vaginal hematoma Be suspicious with increased heart rate, pelvic pain or decreased BP!!!!!!

Cardinal Movements of Labor This refers to the movements made by the fetus during the first and second stage of labor. As the force of the uterine contractions stimulates effacement and dilatation of the cervix, the fetus moves toward the cervix. When the presenting part reaches the pelvic bones, it must make adjustments to pass through the pelvis and down the birth canal

Seven distinct movements: Engagement Descent Flexion Internal rotation Extension External rotation/restitution Expulsion

Cardinal Movements of Labor Engagement Passage of the widest diameter fetal presenting part below the plane of the pelvic inlet The head is said to be engaged if the leading edge is at the level of the ishial spines. Descent Refers to the downward passage of the presenting part through the bony pelvis Not steady process Greatest at deceleration phase of first stage and during 2nd stage of labor

Cardinal Movements of Labor Flexion Occurs passively as the head descends due to the shape of the bony pelvis. Partial flexion occurs naturally but complete flexion usually occurs only in the labor process Complete flexion places the fetal head in optimal smallest diameter to fit through the pelvis Internal Rotation Rotation of the fetal head from occiput transverse to occiput either in anterior or posterior position Occurs passively due to the shape of the bony pelvis

Cardinal Movements of Labor Extension Occurs when the fetus has descended to the level of the vaginal introitus When occiput is just past the level of the symphysis, the angle of the birth canal changes to upward position External Rotation/Restitution As the head is delivered, it rotates back to its original position prior to internal rotation It aligns anatomically with the fetal torso The release of the passive forces on the fetal head allows it to return to appropriate position

Expulsion Delivery of the fetus After delivery of the fetal head, descent and intraabdominal pressure by mother brings shoulder to the level of the symphysis Downward traction allows release of the shoulder and the fetus is delivered.

Analgesia in labor Discomfort during Labor and Birth Pain and discomfort experienced during labor have two neurologic origins: visceral and somatic Neurologic origins Visceral pain: from cervical changes, distention of lower uterine segment, and uterine ischemia Located over the lower portion of abdomen Referred pain: originates in uterus, radiates to abdominal wall, lumbosacral area of back, iliac crests, gluteal area, and down the thighs Somatic pain: pain described as intense, sharp, burning, and well localized Stretching and distention of perineal tissues and pelvic floor to allow passage of fetus, from distention and traction on peritoneum and uterocervical supports during contractions, and from lacerations of soft tissue

Perception of pain Threshold remarkably similar in all, regardless of gender, social, ethnic, or cultural differences Differences play definite role in person’s perception of and behavioral responses to pain

Expression of pain Pain results in physiologic effects and sensory and emotional (affective) responses Emotional expressions of suffering often seen Increasing anxiety Writhing, crying, groaning, gesturing (hand clenching and wringing), and excessive muscular excitability Cultural expression of pain varies

Factors influencing pain response Physiologic factors Culture Anxiety Previous experience Childbirth preparation Comfort and support Environment

Distribution of labor pain A. Distribution of labor pain during first stage B. Distribution of labor pain during later phase of first stage and early phase of second stage C. Distribution of labor pain during later phase of second stage and during birth (Gray shading indicates areas of mild discomfort; light-colored shading indicates areas of moderate discomfort; dark-colored shading indicates areas of intense discomfort.)

Nonpharmacologic Management of Discomfort Nonpharmacologic measures often simple, safe, and inexpensive Provide sense of control over childbirth and measures best for woman Methods require practice for best results Try variety of methods and seek alternatives, including pharmacologic methods, if measure used is not effective

Nonpharmacologic Management of Discomfort Childbirth education Dick-Read method Lamaze method Bradley method Relaxing and breathing techniques Relaxation Imagery and visualization Music Touch and massage Breathing techniques Effleurage and counterpressure Water therapy (hydrotherapy) Transcutaneous electrical nerve stimulation

Pharmacologic Management of Discomfort Sedatives Analgesia and anesthesia Anesthesia Systemic analgesia Opioid agonist analgesics Opioid (narcotic) agonist–antagonist analgesics Co-drugs Ataractics Opioid (narcotic) antagonists Nerve block analgesia and anesthesia Local perineal infiltration anesthesia Prudendal nerve block Spinal anesthesia (block) Disadvantages Medication reactions (allergy) Hypotension Ineffective breathing Headache Autologous epidural blood patch

Pain Pathways and Sites of Pharmacologic Nerve Blocks A. Pudendal block; suitable during second and third stages of labor and for repair of episiotomy B. Epidural block; suitable during all stages of labor and for repair of episiotomy

Pain Pathways and Sites of Pharmacologic Nerve Blocks Nerve block analgesia and anesthesia Epidural anesthesia/analgesia Lumbar epidural anesthesia/analgesia Walking epidural analgesia Epidural and intrathecal opioids

Membranes and spaces of spinal cord and levels of sacral, lumbar, and thoracic nerves Cross section of vertebra and spinal cord

Levels of Anesthesia Necessary for Cesarean and Vaginal Births Cesarean birth Vaginal birth

Care Management Plan of care and interventions (cont’d) Administration of medication Intravenous route Intramuscular route Spinal nerve block Signs of potential problems Safety and general care Anesthesia in the obese woman

Key Points Expected outcome of preparation for childbirth and parenting is “education for choice” Nonpharmacologic pain and stress management strategies are valuable for managing labor discomfort alone or in combination with pharmacologic methods Gate-control theory of pain and stress response are bases for many of the nonpharmacologic methods of pain relief Type of analgesic or anesthetic used is determined in part by stage of labor and method of birth Opioid effects can be potentiated with ataractics

In Summary Know the different stages of labor Know the labor curve Know the cardinal movements of labor Know the causes of postpartum hemorrhage MD must understand medications, expected effects, potential adverse reactions, and methods of administration Maternal fluid balance is essential during spinal and epidural nerve blocks Maternal analgesia or anesthesia potentially affects neonatal neurobehavioral response Use of opioid agonist-antagonist analgesics in women with preexisting opioid dependence may cause symptoms of abstinence syndrome (opioid withdrawal) General anesthesia rarely used for vaginal birth May be used for cesarean birth or when needed in emergency childbirth situation

Thank you for your attention!