Physiology of delivery. Analgesia in labor.

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Physiology of delivery.Analgesia in labor.
Korda I.
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Labor

• Labor is the physiologic process by which a fetus
  is expelled from 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. cervix
  starts out being two inches long, and 50 effaced
  would be a 1 inch cervix.

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Cervical effacement and dilation
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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 Ps
• Powers
• Passenger
• Passage

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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.

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Power

• Generally 3-5 contractions in a 10 minute period
  is considered adequate labor

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Passenger

• Passenger fetus
• Fetal variables that can affect labor
• Fetal Lie the relationship of the long axis of
  the fetus to the long axis of the mother
• longitudinal, transverse or oblique

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Fetal size

• 40 weeks 20.16 inches 7.63 pounds 51.2 cm 3462
  grams
• 41 weeks 20.35 inches 7.93 pounds 51.7 cm 3597
  grams
• 42 weeks 20.28 inches 8.12 pounds 51.5 cm 3685
  grams

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Fetal presentation

• the part of the fetus that lies closest to or has
  entered the true pelvis. Cephalic presentations
  are vertex, brow, face, and chin. Breech
  presentations include frank breech, complete
  breech, incomplete breech, and single or double
  footling breech. Shoulder presentations are rare
  and require cesarean section or turning before
  vaginal birth. Compound presentation involves the
  entry of more than one part in the true pelvis,

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• Attitude degree of flexion or extension of the
  fetal head

A--Complete flexion. B-- Moderate flexion.
C--Poor flexion. D--Hyperextension
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• Position - the relationship of the part of the
  fetus that presents in the pelvis to the four
  quadrants of the maternal pelvis, identified by
  initial L (left), R (right), A (anterior), and P
  (posterior). The presenting part is also
  identified by initial O (occiput), M (mentum),
  and S (sacrum)
• Number of fetuses
• Presence of fetal anomalies hydrocephalus,
  sacrococcygeal teratoma

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The Fetal Skull
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Fetal Positions for Labor and Birth

• Left Occiput Anterior (LOA)

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Left Occiput Transverse (LOT)

• Left Occiput Transverse (LOT)

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Left Occiput Posterior (LOP)
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Right Occiput Anterior (ROA)
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Right Occiput Transverse (ROT)
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Right Occiput Posterior (ROP)
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Leopold's Maneuvers
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Station

• 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.

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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

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Passage
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The Stages of Labor

• First Stage
• Interval between the onset of labor and full
  cervical dilation
• Two phases
• Latent phase onset of 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

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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.

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Labor
Labor NulliG MultiG
1st Stage Active phase
Duration 6-18 h 2-10 h
Dilation 1 cm/h 1.5 cm/h
2nd Stage 0.5-3 h 5-30 min
3rd Stage 0-30 min 0-30 min

• Freidmans curve is a good guideline for expected
  progression in labor and therefore helpful to
  note abnormal labor patterns.

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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.
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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.

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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

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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

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Seven distinct movements

• Engagement
• Descent
• Flexion
• Internal rotation
• Extension
• External rotation/restitution
• Expulsion

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Descent As the fetal head engages and descends,
it assumes an occiput transverse position because
that is the widest pelvic diameter available for
the widest part of the fetal head.
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Flexion While descending through the pelvis, the
fetal head flexes so that the fetal chin is
touching the fetal chest. This functionally
creates a smaller structure to pass through the
maternal pelvis. When flexion occurs, the
occipital (posterior) fontanel slides into the
center of the birth canal and the anterior
fontanel becomes more remote and difficult to
feel. The fetal position remains occiput
transverse.
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Internal Rotation With further descent, the
occiput rotates anteriorly and the fetal head
assumes an oblique orientation. In some cases,
the head may rotate completely to the occiput
anterior position
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Extension The curve of the hollow of the sacrum
favors extension of the fetal head as further
descent occurs. This means that the fetal chin is
no longer touching the fetal chest.
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• External Rotation The shoulders rotate into an
  oblique or frankly anterior-posterior orientation
  with further descent. This encourages the fetal
  head to return to its transverse position. This
  is also known as restitution.

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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.

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• Suctioning the nasopharynx

• Cut between the clamps

• Clamp the umbilical cord

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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.

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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

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Inspect the placenta for completeness
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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!!!!!!

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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

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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

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Factors influencing pain response

• Physiologic factors
• Culture
• Anxiety
• Previous experience
• Childbirth preparation
• Comfort and support
• Environment

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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-coloredshadin
  g indicates areas of intense discomfort.)

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Nonpharmacologic Managementof 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

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Nonpharmacologic Managementof Discomfort

• Childbirth education
• Dick-Read method(recommended the need for
  education and his teaching method included
  lectures, exercise, and a focus on breathing and
  relaxation techniques.
• 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

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Pharmacologic Managementof Discomfort

• 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

• Sedatives
• Analgesia and anesthesia
• Anesthesia
• Systemic analgesia
• Opioid agonist analgesics
• Opioid (narcotic) agonistantagonist analgesics
• Co-drugs
• Ataractics
• Opioid (narcotic) antagonists

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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

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• Membranes and spaces of spinal cord and levels
  of sacral, lumbar, and thoracic nerves

• Cross section of vertebra and spinal cord

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Levels of Anesthesia Necessary for Cesarean and
Vaginal Births
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• Administration of medication
• Intravenous route
• Intramuscular route
• Spinal nerve block
• 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

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• 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

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Regarding Labour

• the latent phase may last for more than four
  hours 
• the active phase should be associated with
  cervical dilatation at a rate of at least 1 cm.
  per hour 
• the active phase starts when the cervix is
  effaced and 2 cm. dilated 
• involves artificial rupture of the membranes 
• is best charted using a partogram 
• epidural anaesthesia has an adverse effect on the
  rate of progress in the 1st. stage of labour

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• the latent phase may last for more than four
  hours 
• the active phase should be associated with
  cervical dilatation at a rate of at least 1 cm.
  per hour 
• the active phase starts when the cervix is
  effaced and 2 cm. dilated 
• involves artificial rupture of the membranes 
• is best charted using a partogram 
• epidural anaesthesia has an adverse effect on the
  rate of progress in the 1st. stage of labour

T T F F T F
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• During delivery, what comes next after
  Engagement, Descent, and Flexion?
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• 1. Internal Rotation.
•  
• 2. Extension.
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• 3. External Rotation.
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• 4. Expulsion.

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• During delivery, what comes next after
  Engagement, Descent, and Flexion?
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• 1. Internal Rotation.
•  
• 2. Extension.
•  
• 3. External Rotation.
•  
• 4. Expulsion.

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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

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Thank you for your attention!