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Analgesics for obstetrics: Nursing Pharmacology

Notes

Notes

ANALGESICS FOR OBSTETRICS
DRUG NAME
Systemic analgesics: fentanyl, remifentanyl (Ultiva)
Regional analgesics: bupivacaine (Marcaine, Sensorcaine), ropivacaine (Naropin)
CLASS
Opioids
Local anesthetics
MECHANISM OF ACTION
Bind to the opioid receptors to increase the pain threshold and alter pain transmission
Reversibly block the sodium channels on the neurons to prevent the transmission of pain
INDICATIONS
Pain during vaginal delivery
Pain during vaginal delivery or cesarean delivery
ROUTE(S) OF ADMINISTRATION
  • IV
  • IM
  • SUBQ
  • Pudendal
  • Epidural
  • Spinal
SIDE EFFECTS
  • Respiratory depression
  • Nausea, vomiting, and constipation
  • Pruritus
  • Hypotension
  • Sedation, euphoria, and confusion
  • Decrease frequency and duration of uterine contractions
  • Fetal bradycardia, reduced variability of fetal heart rate, and hypotonia
  • Accidental spinal cord injury, dural puncture
  • Motor weakness
  • Infection
  • Maternal hypotension
  • Fetal asphyxia
  • Respiratory depression
  • Anesthetic migration
  • Intravascular injection, cardiac arrest or death
CONTRAINDICATIONS AND CAUTIONS
  • Respiratory depression
  • Bleeding disorders
  • Skin infection at injection site
NURSING CONSIDERATIONS: ANALGESICS FOR OBSTETRICS
PRE-ADMINISTRATION
  • Baseline vital signs, SpO2, pain rating, uterine activity, FHR
  • Comfort measures and nonpharmacological pain interventions
POST-ADMINISTRATION
  • Continued assessment and monitoring; vital signs, uterine activity, FHR; monitor for side effects
  • For hypotension (100 mmHg or 20 mmHg drop from baseline readings) or fetal bradycardia, decreased FHR variablilty
    • Initiate intrauterine resuscitation procedures: IV fluid bolus, oxygen 8–10 L/minute per nonrebreather mask, stop oxytocin
CLIENT EDUCATION
  • Potential effects on labor, fetus, newborn
OPIOIDS
  • Administer after labor pattern is established
  • Hold if RR < 12/minute
  • Avoid administration within 1–4 hours of expected delivery
EPIDURAL
  • Review laboratory results for hemoglobin, hematocrit, platelets, coagulation studies
  • Obtain baseline vital signs and FHR
  • Administer IV bolus of crystalloid fluid
  • Assist with positioning
  • Encourage breathing and relaxation during insertion
  • Monitor for occurrence of high regional block
    • Dyspnea, bradycardia, weakness or numbness of the upper extremities, altered level of consciousness
  • Insert foley catheter if indicated
  • Clearly label catheter tubing
  • Assess catheter insertion site, level of sensory block, motor function
  • If intrauterine resuscitation required, notify the anesthesia provider and prepare to administer ephedrine
Transcript

Analgesics are medications used to relieve pain, and can be used for various reasons in obstetrics, such as during pregnancy to manage headaches, back, or pelvic pain during delivery to help reduce pain from uterine contractions, cervical stretching, and vaginal distension; as well as following vaginal delivery for perineal lacerations, and following cesarean delivery for pain at the incisional site.

Commonly used analgesics in obstetric settings include acetaminophen, which is mainly used during pregnancy; as well as systemic analgesics like opioids and regional analgesics like local anesthetics, which are typically used once the client goes into labor.

However, other analgesics like NSAIDs, such as ibuprofen, should be avoided during pregnancy, since they can cause fetal harm, including fetal renal impairment, oligohydramnios, and premature closure of the fetal ductus arteriosus.

Now, opioids can be full opioid agonists like fentanyl and remifentanil; and partial opioid agonists like butorphanol and nalbuphine; whereas regional anesthetics include bupivacaine and ropivacaine.

Now, in general, analgesics act by blocking neurons that transmit pain sensations. Opioids act on opioid receptors called the mu, kappa, and delta receptors. These receptors are typically located on the pre- and post-synaptic membranes of the pain-conducting neurons in the spinal cord and brain.

Now, opioids are primarily given orally, intramuscularly, and intravenously. When opioids bind to their receptors, they result in a decreased sensitivity to pain by increasing the pain threshold and altering pain transmission.

On the other hand, regional anesthetic medications act by reversibly blocking sodium channels on the neurons and prevent the transmission of pain.

Regional anesthetics can either be injected locally into the pudendal nerve area, called a pudendal anesthesia or nerve block, to numb the lower vagina, vulva, and perineum, which is often used in the repair of episiotomy, or perineal tears.

Now, neuraxial anesthesia, which refers to the injection of opioids combined with a local anesthetic into either the epidural space or the subarachnoid space of the spinal cord, is an effective way to numb larger areas, especially in clients who experience severe labor pains or require a cesarean birth.

Okay, so each class of analgesics has its own set of side effects. Opioids can result in respiratory depression, nausea, vomiting, and constipation, as well as pruritus, hypotension, sedation, euphoria, and confusion.

Additionally, opioids can cause a decrease in the frequency and duration of uterine contractions. Finally, opioids can cross the placenta and cause fetal bradycardia and reduced variability of fetal heart rate, as well as hypotonia, or reduced muscle tone at birth.

On the other hand, side effects of regional anesthetics vary based on the medication and route of administration. Common side effects seen with epidural and spinal anesthesia include accidental injury to the spinal cord, motor weakness, infection, and maternal hypotension, which can further reduce placental blood flow and cause fetal asphyxia.

Occasionally, the anesthetic agent can migrate above the administered level and even reach the brainstem, leading to respiratory depression.

When the client is recovering from spinal anesthesia or if there is an accidental dural puncture during epidural catheter placement, a common side effect is headache.

Lastly, systemic toxicity with a local anesthetic during epidural anesthesia may result in cardiac arrest or even death.

Now, most analgesics are generally avoided after the first trimester of pregnancy and until labor begins. And, due to their addictive potential, prolonged use of opioids can cause neonatal abstinence syndrome.

Opioids are also contraindicated in those with respiratory disorders like asthma, since they may cause respiratory depression.

Moreover, opioids should not be combined with central nervous system or CNS depressants, such as barbiturates or benzodiazepines, since their effects may add up, causing coma or even death.

Lastly, local anesthetics are contraindicated in those with bleeding disorders, or with a skin infection at the catheter insertion site that may spread to the spinal cord and brain.

As a nurse caring for a client in labor, you will be providing non-pharmacological comfort measures and administering medications for pain management.

Sources
  1. "Focus on Nursing Pharmacology" LWW (2019)
  2. "Pharmacology" Elsevier Health Sciences (2014)
  3. "Mosby's 2021 Nursing Drug Reference" Mosby (2020)
  4. "Saunders Comprehensive Review for the NCLEX-RN Examination" Saunders (2016)