Pain Management in Labour

Experience of Pain During Childbirth

Pain accompanies labor contractions for a number of different reasons.

Etiology of Pain During Labor and Birth

Normally, contractions of involuntary muscles, such as the heart, stomach, and intestine, do not cause pain. This concept makes uterine contractions unique because they do cause it. Several explanations exist for why this happens. During contractions, blood vessels constrict, reducing the blood supply to uterine and cervical cells, resulting in anoxia to muscle fibers. This anoxia can cause pain in the same way that blockage of the cardiac arteries causes the pain of a heart attack. As labor progresses and contractions become longer and harder, the ischemia to cells increases, the anoxia increases, and the pain intensifies.

Pain also probably results from stretching of the cervix and perineum. This phenomenon is the same as that causing intestinal pain when accumulating gas stretches the intestines. At the end of the transitional phase in labor, when stretching of the cervix is complete and the woman feels she has to push, pain from the contractions often disappears as long as the woman is pushing, until the fetal presenting part causes the final stretching of the perineum.

Additional discomfort in labor may stem from the pressure of the fetal presenting part on tissues, including pressure on surrounding organs, such as the bladder, the urethra, and the lower colon. Pain at birth largely results from stretching of the perineal tissue.

Physiology of Pain

Pain is a basic protective mechanism that alerts a person that something harmful is happening somewhere in the body. Pain sensation begins in nociceptors, the end points of afferent nerves, when they are activated by mechanical, chemical, or thermal stimuli. Nociceptors are located predominantly in the skin, bone periosteum, joint surfaces, and arterial walls. When end terminals are stimulated, chemical mediators such as prostaglandins, histamine, bradykinin, and serotonin are synthesized and sensitize the nociceptors. The pain impulse is transmitted along small, unmyelinated C fibers and large, myelinated A-delta fibers to the spinal cord. The more numerous C fibers conduct slowly and apparently carry dull, low-level pain; the fewer A-delta fibers apparently carry sharp, well-localized pain such as labor contractions.

In the dorsal horn of the spinal cord, somatostatin, cholecystokinin, and substance P serve as neurotransmitters or assist the pain impulse across the synapse between the peripheral nerve and the spinal nerve. The pain impulse then ascends the spinal cord to the brain cortex, where it is interpreted as pain.

The Melzack-Wall gate control theory of pain control, the most widely accepted theory of pain response today, proposes that pain can be halted at three points: the peripheral end terminals, the synapse points in the dorsal horn, or the point at which the impulse is interpreted as pain in the brain cortex.

Pain in peripheral terminals is automatically reduced by the production of endorphins and enkephalins, naturally occurring opiates that limit transmission of pain from the end terminals. Pain can be reduced further by mechanically irritating nerve fibers by an action such as rubbing the skin. This technique blocks nerve transmission.

A major action of pain medications is to block spinal cord neurotransmitters, never allowing the pain impulse to cross to a spinal nerve. The brain cortex can be distracted from sensing impulses as pain by such techniques as imagery, thought stopping, aromatherapy, or yoga.

Sensory impulses from the uterus and cervix synapse at the spinal column at the level of T10 through T12 and L1. Pain relief measures for the first stage of labor, therefore, must block these upper synapse sites. For the elimination of pain during cesarean birth, receptors at the level of T6 through T8 must be blocked, so that both the upper and lower uterus are blocked.

Sensory impulses from the perineum are carried by the pudendal nerve to join the spinal column at S2, S3, and S4. When the perineum is initiating the pain, pain relief must block these lower receptor sites. This is an important point to remember when talking to a woman in labor about pain relief. Some interventions relieve pain for both the first and second stages of labor, whereas others work for one stage but not both.

Perception of Pain

The amount of discomfort a woman experiences during contractions differs according to her expectations of and preparation for labor, the length of her labor, the position of her fetus, and the availability of support people around her. The discomfort she experiences can become compounded when fear and anxiety are also present.

Pain is perceived differently by different individuals because of psychosocial, physiologic, and cultural response. The body's ability to produce and maintain endorphins (naturally occurring opiate-like substances) may influence a person's overall pain threshold and the amount of pain a person perceives at any given time. Women who come into labor believing the pain will be horrible are usually surprised afterward to realize that the agony they expected never materialized. On the other hand, expectations of pain may make a woman so tense during labor that her pain is worse than it would have been if she had been relaxed. A woman cannot relax simply because she is instructed to do so by another person, however. Some additional interventions must be used.

Factors Influencing Pain Perception

• Fetal position is a physical variable that can influence the degree of pain a woman experiences. If the fetus is in an occiput posterior position, for example, the woman often reports intense or nagging back pain, even between contractions.
• Psychological factors that can influence pain include fear, anxiety, worry, expectation of pain, body image, and self-efficacy. Women who believe that they can control their situation (have self-efficacy) are more apt to report a satisfactory birth experience than those who do not feel in control
• Responses to pain are, in part, culturally determined. Based on this, some women believe that being stoic and nonverbal is what is expected of them. Others believe that expressing their discomfort by screaming or verbalizing their feelings will best reduce pain. Assess each woman individually to determine not only what level of comfort she feels is right for her during labor but also the manner in which she feels most able to express discomfort. Depend on facial expression, body posture, and tension, as well as voiced expressions, to determine a client's level of comfort.
• The amount of analgesia that women desire or will accept is both situationally and culturally determined. In a culture in which birth is seen as a “natural” process, less analgesia is generally desired. Women who have an effective support person with them may need less pharmacologic pain relief than those who do not. Providing nursing support can have a positive influence on pain relief in labor.

Comfort and Pain Relief Measures

Nurses play a key role in educating women and their support persons about the numerous comfort and pain relief strategies available and making sure couples understand the choices available to them along with the benefits and risks. Throughout their decision-making process, couples need support for their choices so that they can feel confidence in the method chosen.

Support from a Doula or Coach

A woman's husband or the father of her child has traditionally served as the chief support person in labor. However, some husbands or fathers find it difficult to provide effective coaching or support in labor because of their own emotional involvement in the birth. Women who are aware that they may not have effective one-to-one support in labor from their baby's father should be encouraged to identify an additional person who could come with them and provide this support. A doula is a woman who is experienced in childbirth, but without professional credentials, who guides and assists women in labor. Having a doula can increase a woman's self-esteem as well as decrease rates of oxytocin augmentation, epidural anesthesia, and cesarean birth.

Complementary and Alternative Therapies for Pain Relief

Complementary and alternative therapies for pain relief involve nonpharmacologic measures that may be used either as a woman's total pain management program or to complement pharmacologic interventions. Most of these interventions are based on the gate control theory concept that distraction can be effective in preventing the brain from processing pain sensations coming into the cortex.

Relaxation

Relaxation keeps the abdominal wall from becoming tense, allowing the uterus to rise with contractions without pressing against the hard abdominal wall. It also serves as a distraction technique because, while concentrating on relaxing, a woman cannot concentrate on pain. In addition to conscious relaxation, having a woman shift position or find the position in labor that is most comfortable for her can be helpful. Asking a woman to bring favorite music tapes or aromatherapy with her to enjoy in the birthing room is a good way to aid relaxation.

Focusing and Imagery

Concentrating intently on an object is another method of distraction, or another method of keeping sensory input from reaching the cortex of the brain. For this technique, a woman uses a photograph of someone important to her or some image she finds appealing. She concentrates on it during contractions (focusing). Other women concentrate on a mental image, such as waves rolling onto a beach (imagery). Do not ask questions or talk to a woman while she is using imagery or focusing, because it breaks her concentration.

Breathing Techniques

Breathing patterns are also taught in most preparation for childbirth classes. They are advantageous because they help to relax a woman's abdomen. They are largely distraction techniques, because a woman concentrating on slow-paced breathing cannot concentrate on pain. Breathing strategies can be taught to a woman in labor if she is not familiar with their advantages before labor.

Herbal Preparations

Several herbal preparations have traditionally been used to reduce pain with dysmenorrhea or labor, although there is little factual support for their effectiveness. Examples include raspberry leaves, fennel, and life root. Blue cohosh (squaw root), used to induce uterine contractions, is not recommended because of the risk of acute toxic effects (e.g., cerebrovascular accident) to the mother or fetus.

Aromatherapy and Essential Oils

Aromatherapy is the use of aromatic oils to complement emotional and physical well-being. Their use is based on the principle that the sense of smell plays a significant role in overall health. When an essential oil is inhaled, its molecules are transported via the olfactory system to the limbic system in the brain. The brain responds to particular aromas with emotional responses. When applied externally, they are absorbed by the skin and then carried throughout the body. The oils used may be able to penetrate cell walls and transport nutrients or oxygen to the inside of cells. Jasmine and lavender are oils thought to be responsible for an easier labor. When a drop of oil, such as lavender, is placed on the skin, a woman is able to taste it within 15 seconds.

Heat or Cold Application

Heat and cold have always been used for pain relief after injuries such as minor burns or strained muscles. It is only lately that they have been investigated as effective ways to help relieve the pain of labor contractions. Women who are having back pain may find application of heat to the lower back by a heating pad or a moist compress very comforting.

Women who become warm from the exertion of labor find a cool washcloth to the forehead comforting. Ice chips to suck on to relieve mouth dryness are also refreshing.

Bathing or Hydrotherapy

Standing under a warm shower or soaking in a tub of warm water, jet hydrotherapy tub, or whirlpool is another way to apply heat to help reduce the pain of labor. The temperature of water used should be between 95°F and 100°F (35.0°C and 37.8°C) to prevent hyperthermia. This type of pain relief measure usually is not recommended for women whose membranes have ruptured because of the risk of infection.

Therapeutic Touch and Massage

Therapeutic touch is the use of touch to comfort and relieve pain. It is based on the concept that the body contains energy fields that, when plentiful, lead to health and, when in less supply, result in ill health. Therapeutic touch is defined as the laying on of hands to redirect the energy fields that lead to pain. Although the action is not well documented, touch and massage probably work to relieve pain by increasing the release of endorphins. It also is a form of distraction. Effleurage, the technique of gentle abdominal massage often taught with Lamaze preparation for childbirth classes, is a form of therapeutic touch

Yoga

Yoga, a term derived from the Sanskrit word for union, denotes a series of exercises that were originally designed to bring people who practice it closer to their God. It offers a significant variety of proven health benefits, including increasing the efficiency of the heart, slowing the respiratory rate, improving fitness, lowering blood pressure, promoting relaxation, reducing stress, and allaying anxiety. Exercises consist of deep breathing exercises, body postures to stretch and strengthen muscles, and meditation to focus the mind and relax the body. It may be helpful in reducing the pain of labor through its ability to relax the body and possibly through the release of endorphins that may occur.

Reflexology

Reflexology is the practice of stimulating the hands, feet, and ears as a form of therapy. Professional reflexologists apply pressure to specific areas of the hands, feet, and ears to alleviate common ailments such as headaches, back pain, sinus colds, and stress. The theory behind reflexology is that each of the body's organs and glands are linked to corresponding areas of the hands and feet. The body is divided into 10 zones that run in longitudinal lines from the top of the head to the tips of the toes. Application of pressure to the specific area aims to restore energy to the body and improve the overall condition.

Crystal or Gemstone Therapy

Some gemstones or crystals are thought to have healing powers, and women may bring these into a birthing room to use during labor. A woman who uses crystals or gemstones may believe that their healing power is magnified when they are positioned around her body. Be especially careful when changing bedding or rearranging equipment in a birthing room to respect the position of these crystals. A woman may feel that they do not work their healing powers in an altered position.

Hypnosis

Hypnosis is yet another method of pain relief for labor. A woman who wants to use this modality needs to meet with her hypnotherapist during pregnancy. At these visits, she is evaluated for and further conditioned for susceptibility to hypnotic suggestion. At the last prenatal visit, she is given the posthypnotic suggestion that she will experience reduced pain or absence of pain during labor. For a woman who is susceptible to hypnotic suggestion, the method can provide a very satisfactory drug-free method of pain relief.

Biofeedback

Biofeedback is based on the belief that people have control and can regulate internal events such as heart rate and pain response. Women who are interested in using biofeedback for pain relief in labor must attend several sessions during pregnancy to condition themselves to regulate their pain response. During these sessions, a biofeedback apparatus is used to measure muscle tone or the woman's ability to relax.

Transcutaneous Electrical Nerve Stimulation

Transcutaneous electrical nerve stimulation (TENS) relieves pain by counterirritation on nociceptors. With two pairs of electrodes attached to a woman's back to coincide with the T10–L1 nerve pathways, low-intensity electrical stimulation is given continuously or is applied by the woman herself as a contraction begins. This stimulation blocks the afferent fibers, preventing pain from traveling to the spinal cord synapses from the uterus. As labor progresses and the pelvic division begins, the electrodes are moved to stimulate the S2–4 level. High-intensity stimulation is generally needed to control the pain at this stage.

TENS can be as effective as epidural anesthesia for pain relief in labor, but some women may object to being “tied down” to the equipment. Women with extreme back pain during labor may benefit the most from a TENS unit, because this type of pain is difficult to relieve with controlled breathing exercises. TENS is also discussed in Chapter 20 as it applies to the postoperative pain of a cesarean birth.

Acupressure and Acupuncture

Acupuncture is based on the concept that illness results from an imbalance of energy. To correct the imbalance, needles are inserted into the skin at designated susceptible body points (tsubos) located along meridians that course throughout the body to supply the organs of the body with energy. These points are not necessarily near the affected organ. Activation of these points apparently results in release of endorphins, so the system can be helpful, especially in the first stage of labor.

Acupressure, in contrast, is the application of pressure or massage at these points. A common point used for a woman in labor is Co4 (Hoku or Hegu point) located between the first and second metacarpal bones on the back of the hand. When a support person holds and squeezes a woman's hand in labor, he or she may be accidentally triggering this point.

Pharmacologic Pain Relief During Labor

Pharmacologic management of pain during labor and birth includes analgesia, which reduces or decreases awareness of pain, and anesthesia, which causes partial or compete loss of sensation. Many choices are available today. For the best results, be sure women are included in a selection that is right for them.

Virtually all medication given during labor crosses the placenta and has some effect on the fetus, which makes it important for a woman to receive as little systemic medication as possible. On the other hand, labor should not test a woman to the limit of her endurance, especially since local anesthesia is available. Be sure to caution women not to take acetylsalicylic acid (aspirin) for pain in labor. Aspirin interferes with blood coagulation, increasing the risk for bleeding in the newborn or mother.

Goals of Pharmacologic Management of Pain During Labor

Medication effectively used during labor must relax a woman and relieve her discomfort, yet have minimal systemic effects on her uterine contractions, her pushing effort, or her fetus. Whether a drug affects a fetus depends on its ability to cross the placenta. Drugs with a molecular weight of more than 1,000 cross poorly, whereas those with a molecular weight of less than 600 cross very readily. Drugs with highly charged molecules or molecules strongly bound to protein cross more slowly than others. Fat-soluble drugs cross most easily. A preterm fetus, which has an immature liver and is unable to metabolize or inactivate drugs, is generally more affected by drugs than a term fetus. If a drug causes a systemic response, such as hypotension, in a woman, it can result in a decreased oxygen (PO2) gradient across the placenta and fetal hypoxia. If it causes confusion or disorientation, she may be unable to work effectively with contractions, prolonging labor. If a medication causes changes in a fetus, such as a decreased heart rate or central nervous system (CNS) depression, it may be difficult for the newborn infant to initiate respirations at birth, severely compromising the infant in the important first minutes of life.

Because pain is a subjective sensation, women experience different levels of pain during labor. Some women are most aware of pain early in labor, whereas some report the second stage of labor as the most difficult. The point at which pain medication is needed, therefore, differs from one individual to another.

Preparation for Medication Administration

The type of medication used during labor varies among different health care agencies and also changes based on new research as the effectiveness and safety of new drugs for use during labor are tested. To be safe, remember the criteria that a drug must fulfill to be used in pregnancy, or expand the rule of basic medication administration from “Never give any drug unless you know it is safe for your individual client” to “Never give a drug during labor without knowing it is safe for both of your clients: the mother and the fetus.”

Medicines frequently used in labor and birth are shown in TABLE 19.1. Prepare the woman for the type of agent to be given, how it will be administered (e.g., “You'll need to lie on your side”), and what she can expect to happen after administration (e.g., “I'll be taking your blood pressure frequently”). Women in labor are under stress. Experiencing surprising body sensations from a drug without preparation can be so frightening that it can defeat their individual coping abilities. When a person struggles against medication administration because she does not understand the strange feeling it is causing, the risk of inadvertent problems increases.

Narcotic Analgesics

Narcotics are often given during labor because of their potent analgesic effect. All drugs in this category cause fetal CNS depression to some extent. Be sure to question an order for a narcotic if a woman is in preterm labor. Because of possible lung immaturity, a preterm infant may have extreme difficulty coping with the added insult of respiratory depression at birth.

Narcotic analgesics commonly used include meperidine hydrochloride (Demerol), morphine sulfate, nalbuphine (Nubain), fentanyl (Sublimaze), and butorphanol tartrate (Stadol). Meperidine is advantageous as an analgesic in labor because it has additional sedative and antispasmodic actions; these make it effective not only for relieving pain but also for helping to relax the cervix and providing a feeling of euphoria and well-being. It may be given either intramuscularly or intravenously. The dose is 25 to 100 mg, depending on a woman's weight and the route of administration. The drug begins to act about 30 minutes after intramuscular (IM) injection and about 5 minutes after intravenous (IV) administration. Its duration of action is 2 to 3 hours. Demerol also may be self-administered by a patient-controlled analgesic (PCA) pump for low-dose but frequent administration during labor . Intrathecal administration (injection into the cerebral spinal fluid) is used less frequently.

Because Demerol crosses the placenta, it can cause respiratory depression in a fetus. The drug crosses the placenta minutes after either IV or IM administration to the mother. However, because the fetal liver takes 2 to 3 hours to activate the drug into the fetal system, the effect will not be registered in the fetus for 2 to 3 hours after maternal administration. For this reason, Demerol is given when the mother is more than 3 hours away from birth. This allows the peak action of the drug in the fetus to have passed by the time of birth.

Whenever a narcotic is given during labor, a narcotic antagonist such as naloxone (Narcan) should be available for administration to the infant at birth. Carefully observe an infant who receives naloxone in the immediate postpartum period, because the infant's respirations may become severely depressed again when the drug's effect wears off. If severe infant respiratory depression is anticipated, Narcan can be given to the mother just before birth. It readily crosses the placenta and, because it interferes with or competes for narcotic binding sites, may increase the chance for spontaneous respiratory activity in the newborn.