Analgesics for obstetrics: Nursing pharmacology

Definitions & Key takeaways

Analgesics are medications that relieve pain. There are several different types of analgesics, including opioid analgesics, non-opioid analgesics, and adjuvant analgesics. Adjuvant analgesics are medications that are used in addition to opioid or non-opioid analgesics to provide better pain relief.

There are several different types of analgesics available for use in obstetrics. Some of the most common include morphine, fentanyl, hydromorphone, and oxycodone. These medications can be used to provide relief from labor pain as well as pain associated with postpartum hemorrhage or cesarean section.

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Introduction0:00–0:57

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 and Anesthetics0:57–1:14

Mechanism1:14–2:37

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.

Side Effects2:37–4:36

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.

Nursing Considerations and Client Teaching4:36–8:51

Your goal is to work with your client and safely manage pain in order to minimize the harmful effects of severe labor pain, including anxiety, decreased blood flow and oxygen delivered to the fetus, and uncoordinated uterine contractions.Now, there are several considerations that should be taken into account before administration of any analgesic.
First, assess the baseline uterine activity and determine the baseline fetal heart rate or FHR, variability, and the presence of accelerations or decelerations.
Then obtain baseline vital signs and SpO2; assess your client's pain rating and pain tolerance. If an opioid analgesic is prescribed, keep in mind that opioids may temporarily decrease the frequency and duration of uterine contractions, so ideally you’ll administer the medication after a pattern of labor contractions is well established.
Be sure your client understands the medication will blunt but not eliminate pain, and that the medication may cause sedation, which can actually help her to rest between contractions.
Also teach your client that opioids cross the placenta and can cause neonatal respiratory depression, so let her know you will avoid administering an opioid within 1 to 4 hours of expected delivery.
After administration, continue to reassess pain levels and tolerance. Monitor for side effects such as respiratory depression, and hold the medication if respirations are less than 12 breaths per minute; also monitor for nausea and vomiting and manage these with comfort measures and antiemetic medications, as ordered.
When assisting with epidural anesthesia, be sure your client understands the procedure and informed consent is obtained.
Review laboratory results, especially hemoglobin, hematocrit, platelets, and coagulation studies, and report any abnormal results to the anesthesia provider.
Before the procedure, establish IV access and administer the prescribed bolus of IV crystalloid fluid, which will reduce the risk of hypotension.
Let your client know that they may feel a little pressure as the catheter is placed into the epidural space, then assist her into either a seated or lateral position with the back curved outward, which will increase the distance between the spinous process of the vertebrae, which will make the insertion of the epidural catheter much easier.
During catheter insertion, encourage breathing and relaxation, and keep a close eye on the client’s blood pressure and oxygen saturation as well as the FHR.Monitor for indications that the medication has spread above the area of administration, referred to as a high regional block, including dyspnea, bradycardia, weakness or numbness of the upper extremities, and altered level of consciousness.
While you care for your client receiving epidural analgesia and anesthesia, monitor vital signs, especially blood pressure.If your client’s systolic blood pressure drops to less than 100 mmHg, or if a 20 mmHg drop from baseline readings occurs; if fetal bradycardia develops; or if there’s a decrease in FHR variablilty, initiate intrauterine resuscitation procedures by administering an IV fluid bolus, oxygen per nonrebreather mask at 8-10 L/minute, stop the oxytocin, if infusing, and notify the anesthesia provider.
Prepare to administer the alpha/beta agonist ephedrine as ordered to increase your client’s blood pressure. Other ongoing monitoring and assessments include pain perception; level of sensory block and motor function; SpO2; level of consciousness; FHR; uterine activity; and progression of labor.
Assess the catheter insertion site and ensure the catheter is clearly labeled so it is not confused with IV tubing. And because the epidural can interfere with your client’s ability to empty her bladder you may need to place an indwelling urinary catheter.
Alright, as a quick recap … Analgesics are medications used to relieve pain in obstetric settings to manage pain in pregnancy, during labor and delivery, and post delivery by blocking neurons that transmit pain sensations.

Summary8:51–9:18

Nurses are responsible for safely administering and assisting with the administration of analgesics. While clients are receiving analgesics, nursing considerations include monitoring for side effects and for the continual monitoring and assessments of