Presentation on theme: "Physiology of delivery. Analgesia in labor."— Presentation transcript:
1 Physiology of delivery. Analgesia in labor. Korda I.
2 LaborLabor 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 contractionsDilatation: 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.
3 To push the fetus through the birth canal Labor - MechanicsUterine contractions have two major goals:To dilate cervixTo push the fetus through the birth canalSuccess will depend on the three P’s:PowersPassengerPassage
4 PowerUterine contractionsPower refers to the force generated by the contraction of the uterine myometriumActivity 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.
5 Power There is no specific criteria for adequate uterine activity Generally 3-5 contractions in a 10 minute period is considered adequate labor
6 Passenger Passenger =fetus Fetal variables that can affect labor: Fetal sizeFetal Lie – longitudinal, transverse or obliqueFetal presentation – vertex, breech, shoulder, compound (vertex and hand), and funic (umbilical cord).Attitude – degree of flexion or extension of the fetal headPositionNumber of fetusesPresence of fetal anomalies – hydrocephalus, sacrococcygeal teratoma
8 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.
9 PassagePassage = PelvisConsists of the bony pelvis and soft tissues of the birth canal (cervix, pelvic floor musculature)Small pelvic outlet can result in cephalopelvic disproportionBony pelvis can be measured by pelvimetry but it not accurate and thus has been replaced by a clinical trial of labor
11 The Stages of Labor First Stage Interval between the onset of labor and full cervical dilationTwo phases:Latent phase – onset o f labor with slow cervical dilation to ~4 cm and variable durationActive phase – faster rate of cervical change, cm /hour, regular uterine contractions
12 The Labor CurveFirst stage - A: latent phase; B + C + D: active phase; B: acceleration; C: maximum slope of dilation; D: deceleration; E: second stage.
13 LaborFreidman’s curve is a good guideline for expected progression in labor and therefore helpful to note abnormal labor patterns.LaborNulliGMultiG1st StageActivephaseDuration6-18 h2-10 hDilation~1 cm/h~1.5 cm/hArrested>2 h>2h2nd Stage0.5-3 h5-30 min3rd Stage0-30 min
14 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.
15 Labor – Second StageInterval 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 showPelvic/rectal pressureMother has active role of pushing to aid in fetal descent.
16 Labor – Second StageMolding 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 moldingCaput is the localized edematous area on the fetal scalp caused by pressure on the scalp by the cervix.PrimiG – h; mulitG 0-30min
17 Suctioning the nasopharynx Cut between the clampsClamp the umbilical cord
18 Labor – Third Stage Placental separation and delivery. The time from fetal delivery to delivery of the placentaSigns 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.
19 Labor – Third StagePlacenta 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
22 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.
23 Labor – Fourth StageRefers to the time from delivery of the placenta to 1 hour immediately postpartumBlood pressure, uterine blood loss and pulse rate must be monitor closely ~ 15 minutesHigh risk for postpartum hemorrhage from:Uterine atony, retained placental fragments, unrepaired lacerations of vagina, cervix or perineum.Occult bleeding may occur – vaginal hematomaBe suspicious with increased heart rate, pelvic pain or decreased BP!!!!!!
24 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
26 Cardinal Movements of Labor EngagementPassage of the widest diameter fetal presenting part below the plane of the pelvic inletThe head is said to be engaged if the leading edge is at the level of the ishial spines.DescentRefers to the downward passage of the presenting part through the bony pelvisNot steady processGreatest at deceleration phase of first stage and during 2nd stage of labor
27 Cardinal Movements of Labor FlexionOccurs 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 processComplete flexion places the fetal head in optimal smallest diameter to fit through the pelvisInternal RotationRotation of the fetal head from occiput transverse to occiput either in anterior or posterior positionOccurs passively due to the shape of the bony pelvis
28 Cardinal Movements of Labor ExtensionOccurs when the fetus has descended to the level of the vaginal introitusWhen occiput is just past the level of the symphysis, the angle of the birth canal changes to upward positionExternal Rotation/RestitutionAs the head is delivered, it rotates back to its original position prior to internal rotationIt aligns anatomically with the fetal torsoThe release of the passive forces on the fetal head allows it to return to appropriate position
29 Expulsion Delivery of the fetus After delivery of the fetal head, descent and intraabdominal pressure by mother brings shoulder to the level of the symphysisDownward traction allows release of the shoulder and the fetus is delivered.
30 Analgesia in labor Discomfort during Labor and Birth Pain and discomfort experienced during labor havetwo neurologic origins: visceral and somaticNeurologic originsVisceral pain: from cervical changes, distention of lower uterine segment, and uterine ischemiaLocated over the lower portion of abdomenReferred pain: originates in uterus, radiates to abdominal wall, lumbosacral area of back, iliac crests, gluteal area, and down the thighsSomatic pain: pain described as intense, sharp, burning, and well localizedStretching 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
31 Perception of painThreshold remarkably similar in all, regardless of gender, social, ethnic, or cultural differencesDifferences play definite role in person’s perception of and behavioral responses to pain
32 Expression of painPain results in physiologic effects and sensory and emotional (affective) responsesEmotional expressions of suffering often seenIncreasing anxietyWrithing, crying, groaning, gesturing (hand clenching and wringing), and excessive muscular excitabilityCultural expression of pain varies
34 Distribution of labor pain A. Distribution of labor pain during first stageB. Distribution of labor pain during later phase of first stage and early phase of second stageC. 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.)
35 Nonpharmacologic Management of Discomfort Nonpharmacologic measures often simple, safe, and inexpensiveProvide sense of control over childbirth and measures best for womanMethods require practice for best resultsTry variety of methods and seek alternatives, including pharmacologic methods, if measure used is not effective
36 Nonpharmacologic Management of Discomfort Childbirth educationDick-Read methodLamaze methodBradley methodRelaxing and breathing techniquesRelaxationImagery and visualizationMusicTouch and massageBreathing techniquesEffleurage and counterpressureWater therapy (hydrotherapy)Transcutaneous electrical nerve stimulation
38 Pain Pathways and Sites of Pharmacologic Nerve Blocks A. Pudendal block; suitable during second and third stages of labor and for repair of episiotomyB. Epidural block; suitable during all stages of labor and for repair of episiotomy
39 Pain Pathways and Sites of Pharmacologic Nerve Blocks Nerve block analgesia and anesthesiaEpidural anesthesia/analgesiaLumbar epidural anesthesia/analgesiaWalking epidural analgesiaEpidural and intrathecal opioids
40 Membranes and spaces of spinal cord and levels of sacral, lumbar, and thoracic nerves Cross section of vertebra and spinal cord
41 Levels of Anesthesia Necessary for Cesarean and Vaginal Births Cesarean birthVaginal birth
42 Care Management Plan of care and interventions (cont’d) Administration of medicationIntravenous routeIntramuscular routeSpinal nerve blockSigns of potential problemsSafety and general careAnesthesia in the obese woman
43 Key PointsExpected 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 methodsGate-control theory of pain and stress response are bases for many of the nonpharmacologic methods of pain reliefType of analgesic or anesthetic used is determined in part by stage of labor and method of birthOpioid effects can be potentiated with ataractics
44 In Summary Know the different stages of labor Know the labor curve Know the cardinal movements of laborKnow the causes of postpartum hemorrhageMD must understand medications, expected effects, potential adverse reactions, and methods of administrationMaternal fluid balance is essential during spinal and epidural nerve blocksMaternal analgesia or anesthesia potentially affects neonatal neurobehavioral responseUse 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 birthMay be used for cesarean birth or when needed in emergency childbirth situation