Transcript محاضرة المسكنات في الولادة

Obstetric Analgesia and
Anesthesia
Dr. Rayan G. Albarakati, MBBS, SB-OB
Assistant Professor OB/GYN
Head Of Obsterics & Gynecology
Al Majmaah university
The goal ?
1. Effective pain relief for the mother during the course of labor and delivery
2. That is safe for her and her baby
3. That has minimal adverse effects on the progress & outcome of labor.
* Maternal mortality due to anesthesia has decreased to less than 1 in 500,000
mothers.
Analgesia and Anesthesia
• Analgesia: the relief of pain without loss of consciousness.
• Anesthesia: Total or partial loss of sensation, especially tactile sensibility,
induced by an anesthetic.
Pain pathways of parturition:
• T10 to L1 supply innervation to the uterus.
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L1 to S4 supply pain pathways to the vagina and deep pelvic structures.
• S2 to S4 supply nerve fibers to the pudendal nerve.
Pain Path ways In Labor
ADVERSE EFFECTS OF LABOR PAIN
A) Maternal hyperventilation:
B) Hyperventilation-hypoventilation:
during contractions causes respiratory alkalosis
that results in :
The cyclical nature of contraction pain may cause this
syndrome whereby the mother blows off so much
carbon dioxide during a contraction that she
hypoventilates between contractions and become
mildly hypoxemic between contractions.
(1) a shift of the oxyhemoglobin dissociation
curve to the left.
(2) increased affinity of maternal hemoglobin for
oxygen.
(3) decreased oxygen offloading to the fetus. The
cyclical nature of contraction pain may cause a
hyperventilation-hypoventilation syndrome
whereby the mother blows off so much carbon
dioxide during a contraction that she
C) labor pain results in increased levels
of circulating catecholamines:
The α-adrenergic effects of the catecholamines may
reduce uterine blood flow, whereas the β 2 -adrenergic
effects may impair uterine contractility.
OPTIONS FOR LABOR PAIN RELIEF
A) Pharmacologic treatment
options
B) Nonpharmacologic methods
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Parenteral narcotics
Regional analgesia (epidural, spinal,
combined spinal-epidural, paracervical,
caudal, and pudendal nerve blocks)
Inhalational analgesia
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Education and psychoprophylaxis
Emotional support
Back massage
Hydrotherapy
Biofeedback
Transcutaneous electrical nerve
stimulation
Acupuncture
Hypnosis (hypnobirthing).
Parenteral narcotics
• have very limited efficacy for the relief of labor pain.
• They work best in the early first stage when the pain is primarily visceral and
less intense.
• All opioids readily cross the placental barrier and may cause neonatal
respiratory depression depending on the dose and timing relative to
delivery.
• They may also cause decreased fetal heart rate variability and impair
neonatal breastfeeding.
• Fentanyl and nalbuphine have the shortest neonatal half-lives of the
commonly used parenteral narcotics.
Neuraxial analgesia
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The most effective form of labor pain relief.
Lumbar epidural analgesia is the most common form of neuraxial analgesia used to
treat labor pain
Its use has been steadily increasing to 60 % nationally.
It may be used to provide pain relief for the first and second stages of labor0
by injecting a higher concentration of local anesthetic, the block may be
intensified and extended to provide surgical anesthesia for cesarean delivery or
postpartum tubal ligation.
Anesthetics (bupivacaine, ropivacaine, or lidocaine)
Narcotics (fentanyl or sufentanil) .
The goal is to avoid motor block to minimize any adverse effects on maternal
expulsive efforts in the second stage.
Pudendal Nerve Block
• anesthetizes somatic afferent nerve fibers entering the spinal cord at sacral
segments S2 to S4.
• It is usually effective at relieving the perineal pain of the second stage of
labor , along with the pain of episiotomy and episiotomy repair.
• It does not affect the ongoing pain of uterine contractions.
• Main complications: Nerve injury, hematoma, hypersensitivity.
Pudendal Nerve Block
in a trans-vaginal
approach
Inhalational anesthesia
• Widely used analgesics for labor pain because of their:
1.Availability 2.Simplicity of administration
3.Low cost.
4.Safety
• Their analgesic efficacy is limited compared with regional analgesia.
• Nitrous oxide in oxygen (Entonox) provides moderate pain relief and is safe
for use in labor
Unintended Consequences of Regional
Anesthesia or Analgesia
• Delayed second stage of labor
• Fever (0.5°C increased body temperature)
• Headache: The risk is about 1% to 2% with spinal anesthesia, while in
epidural it is (less than 1%).
• Backache**
• Hypotension
** The risk for new, chronic back pain in parturients is high (up to 47%) whether
or not they have had an epidural
Delayed second stage of labor
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Effects of the release of endogenous oxytocin, prostaglandin
F2a hormones responsible for the propagation of labor.
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Impaired ability to push (unlikely as long as motor block is
avoided).
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Decreased maternal urge to push due to sensory blockade.
Fever
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an alteration in the thermoregulatory threshold
interference with peripheral thermoreceptor input to the central nervous
system
• shifting heat calories from the core to the periphery by vasodilation
• an imbalance between maternal heat production and loss (decreased
hyperventilation, decreased lower body sweating, increased shivering).
Postdural puncture headaches
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These are self-limited
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usually resolving within 5 to 7 days.
Cerebrospinal fluid leaks through the
hole in the dura, resulting in low
intracranial pressure.
The hallmark is a severe positional
headache —little or no headache supine,
sudden onset of severe headache when
sitting upright or standing.
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The dural hole will heal in about 1
week or can be sealed with an
epidural blood patch.
Symptomatic treatment includes
narcotics, nonsteroidal
antiinflammatory drugs, caffeine,
sumatriptan, and abdominal binder.
Contraindications to Regional Anesthesia
Absolute Contraindications
• Patient refusal
• Coagulopathy
• Infection at needle insertion site
• Severe hypovolemia with ongoing
blood loss
Relative Contraindications
• Prior back surgery
• Certain cardiac lesions, especially
aortic stenosis
• Increased intracranial pressure
ANESTHESIA FOR CESAREAN DELIVERY
The type of anesthesia for cesarean delivery is determined by:
• Urgency of the surgery.
• Presence or absence of a preexisting epidural catheter for labor.
• Patient’s medical condition.
• Pregnancy-related complications.
• Presence of any contraindications to regional anesthesia.
ANESTHESIA FOR CESAREAN DELIVERY
• For cesarean delivery, regional anesthesia is preferred because the airway is
maintained .
• General anesthesia carries a 16-fold higher risk of anesthesia-related
maternal mortality compared with regional anesthesia .
• If no epidural is in place, a spinal block is frequently used.
General anesthesia is employed for cesarean
delivery in three situations:
• Extreme urgency without a preexisting, functional epidural catheter
• There is a contraindication to regional anesthesia
• Regional anesthesia has failed.
Parturients have a higher risk for airway
complications than non pregnant patients:
1. An 8 times higher chance of failed intubation
2. 60% increased oxygen consumption
3. Decreased functional residual capacity (FRC) resulting in a lower oxygen
store
4. Increased risk for aspiration.
The protocol for general anesthesia for cesarean
birth includes:
1. Oral administration of nonparticulate antacid (sodium citrate)
2. routine monitoring.
3. Left uterine displacement.
4. Preoxygenation for at least four vital capacity breaths.
5. Rapid sequence induction of anesthesia with cricoid pressure followed by
intubation
6. Once the correct position of the endotracheal tube has been confirmed by
end-tidal CO 2 and auscultation of the lungs, surgery may begin.
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