Labor Flashcards
First stage of labor:
The first stage begins with the onset of regular contractions and ends with full cervical
dilation. It is divided into a slow latent phase (up to 3 cm cervical dilation) and a rapidly progressive
active phase (from 3 cm to full cervical dilation).
Second and third stage of labor:
The second stage extends from full cervical dilation
to delivery of the infant and the third stage begins with the delivery of the infant and ends with delivery
of the placenta.
Labor pain in the first stage is caused by?
Pain during the first stage of labor is primarily caused by uterine contractions and by
progressive distension and dilatation of the cervix together with that of the lower uterine segment.
Which spinal segments are responsible for labor pain in stage 1?
The
first stage nociceptive afferents travel in thoracic fibers T10-T12 and L1. As it arises from visceral
nociceptors it has a diffuse distribution (referred to the skin dermatornes TII-L1 even L2).
Second stage labor pain affected spinal segments:
Second stage labor pain, in contrast, activates somatic fibers in sacral segments S2, 3, 4 (pudendal nerve)
Cause of second stage labor pain?
Due to intense vaginal pressures that cause stretching and tearing of the lower
birth canal and perineum. Uterine contractions still contribute to the mother’s pain, but the sharp,
localized somatic pain predominates.
Nonpharmacological methods of analgesia:
Prepared childbirth
Hypnosis
Acupuncture
Trancutaneous electrical nerve stimulation
Ideal drug for labor:
It is essential that every drug used during labor:
1. has no maternal or fetal toxicity
2. doesn’t provoke maternal hypotension
3. no effects 00 motor function or the progress of labor
4. doesn’t provoke maternal or neonatal respiratory depression
5. is easily to be administered, possibly to be antagonized and rapidly to be eliminated
When is respiratory depression most prevalent with opioid analgesics?
Respiratory depression is most prevalent in the 2nd and 3rd hours after
intramuscular (im) injection but most frequent in the l” hour after intravenous (iv) injection of an
equipotent dose.
Typical labor what is the typical inhaled anesthetic mixture?
50% NO
50% O2
- We commonly use potent halogenated agents - at 0.5 MAC minimum
Paracervical block:
For the pain of the, first stage of labor. Stops afferent nerve transmission
at the paracervical or Frankenhauser ‘s plexus. Timing: during active
labor ‘with the cervix 4-6 ern dilated. After the cervix is dilated 8 ern and fully effaced, the risk of
intrafetal injection increases greatly. Site of injection: two lO-ml injections at the 3 and 9 o’clock cervical
positions. Limit the depth of injection to 3 mm deposits local anaesthetic just below epithelium and
limits risk of injection into paracervical venous plexus. The drug used depends on the desired duration
of effect: 1% CHLORPROCAINE is for short duration and 1% LIDOCAINE for medium duration (without
epinephrine). Bupivacaine is no longer employed for paracervical block because of the possibility of
prolonged fetal myocardial depression. Because of the proximity of fetoplacental unit, placental transfer
of these drugs is rapid and marked, so that fetal bradycardia, occurring 2 to 10 minutes following the
block and lasting 5 to 30 minutes may be developed. Maternal complications: intravascular injection,
postpartum parametritis, subgluteal and retropsoal abscesses
Pudendal block:
Each pudendal nerve arises from the sacral plexus (S2-S4). It is the major
source of sensation in the lower vagina, vulva and perineum. provides the motor innervation of the
perineal muscles. Pudendal block provides pain relief during: the second stage of labor, low forceps
delivery, repair of vaginal and perineal lacerations. It does not allow uterine exploration or manual
removal of the placenta, and it doesn’t relieve the pain of uterine contractions. It is most commonly
performed transvaginally but a transperineal approach is also is possible. Pudendal nerve block is
performed 10-20 minutes before perineal analgesia is needed. Each pudendal nerve arises from the sacral plexus (S2-S4). It is the major
source of sensation in the lower vagina, vulva and perineum. provides the motor innervation of the
perineal muscles. Pudendal block provides pain relief during: the second stage of labor, low forceps
delivery, repair of vaginal and perineal lacerations. It does not allow uterine exploration or manual
removal of the placenta, and it doesn’t relieve the pain of uterine contractions. It is most commonly
performed transvaginally but a transperineal approach is also is possible. Pudendal nerve block is
performed 10-20 minutes before perineal analgesia is needed
Gold standard for obstetrical analgesia?
- Epidural anesthesia
Considered as “the gold standard” in. obstetrical analgesia. Remains the
most reliable, effective method of maternal pain relief. Can provide analgesia through labor and
delivery, as. well as provide anaesthesia for cesarean section. Epidural analgesia usually is initiated
when active labor has been achieved: regular uterine contractions and cervix dilated 5-6 em in a
primipara (3-4 em in a multipara). Institution of epidural analgesia may minimally slow the progress of
labor such that oxytocics may be necessary. Usually the epidural block does not affect the rate of cervical
dilation, or the duration of first stage labor, but it may slightly prolong second stage labor. Although no
consensus yet exists on whether the epidural block influences the rate of instrumental deliveries.
Advantages of epidural anesthesia in labor:
- the risk of neonatal respiratory depression is decreased
- the mother is awake.and able to participate in labor and delivery
- lower risk of pulmonary aspiration
- practically the duration of analgesia is not limited;
- can be used to provide anaesthesia for cesarean section
An important part of the procedure before epidural anesthesia:
A large-bore IV catheter should be placed and at least 500-1000 ml of crystalloid should
be infused before placement of the epidural. This helps prevent hypotension. Also prior to beginning
epidural:
