TOPICS

Labor is different for every woman, and the methods chosen for pain relief will depend on the obstetric/medical condition, the techniques locally available, and the preference of the patient. Neuraxial analgesia is the most effective method. However, there are many mothers who wish to avoid intervention or in whom the technique is contraindicated or impossible to perform. Contraindications for regional labor analgesia may include coagulopathy, local infection, allergy to local anesthetics, and uncorrected hypovolemia. Difficulties in placing epidurals can arise from anatomical deformities, postsurgical spine corrections, and obesity. For this group of parturients, alternative methods may be required and often will involve alternatives to neuraxial analgesia such as nonpharmacologic and pharmacologic techniques.

NONPHARMACOLOGIC LABOR ANALGESIA

Childbirth Education

Antenatal childbirth education is a critical first step for a labor analgesia plan. This dates back to the 1930s, when Grantley Dick-Read in England suggested that childbirth did not require medical intervention if the mother was adequately prepared. In the 1950s, Dr Lamaze, a French obstetrician, developed psychoprophylaxis. This technique involves education regarding the physiologic process of labor and delivery with trained relaxation response to contractions. The technique also uses patterned breathing with two goals: increasing maternal oxygenation and interfering with pain signal transmission to the cerebral cortex from the uterus. Although antenatal education will undoubtedly alleviate some of the fear and anxiety associated with labor, it is unrealistic to suggest that it will lead to painless childbirth for the majority of mothers.

Doulas

Coming from the Greek word for “servant or slave,” a doula is a woman trained to attend to the emotional and physical needs of the parturient. Research has suggested that continuous support and encouragement from doulas throughout labor reduces the need for epidural, analgesic interventions, and the rate of operative deliveries.¹

Transcutaneous Electrical Nerve Stimulation

Transcutaneous electrical nerve stimulation (TENS) is a noninvasive method using surface electrodes placed over the T10-L1 dermatomes and is most effective in early labor. A second set of electrodes can be placed over the S2-S4 dermatomes for second stage pain relief. Conventional TENS utilizes low-intensity, high-frequency biphasic pulsed currents in a repetitive manner with pulse durations of 50 to 250 ms and pulse frequencies of 1 to 200/s. The efficacy of TENS relates to the gate control theory of pain. The electrical current is postulated to reduce pain via nociceptive inhibition at a presynaptic level in the dorsal horn of the spinal cord, thus limiting central transmission of pain impulses. The electrical cutaneous stimulation preferentially activates low-threshold myelinated nerve fibers. This afferent activity inhibits propagation of nociception in small unmyelinated C fibers by blocking transmission to the target cells located within laminae 2 and 3 of the substantia gelatinosa of the dorsal horn.² Another proposed theory is that TENS enhances the release of endorphins and enkephalins, which are naturally occurring neuropeptides.² Currently, there is no evidence that TENS is superior to placebo; however, it is minimally invasive, allows mobilization during use, and is widely available.³

Hydrotherapy

Immersion in warm water to where the abdomen is covered is thought to benefit the mother by facilitating muscular relaxation. There is some evidence that it can reduce women’s perceptions of pain and the demand for regional analgesia in the first stage of labor.⁴ It is not associated with adverse outcomes on duration of labor, operative delivery, or neonatal outcome.⁵ Continuous fetal monitoring cannot be carried out in the birthing pool, so it is not suitable for mothers carrying an at-risk fetus. Similarly, for mothers requiring any kind of continuous monitoring, intravenous infusions, or pharmacologic analgesia, the birthing pool is inadvisable.

Hypnosis, Acupuncture, Aromatherapy, and Reflexology

Hypnosis can be described as an altered state of consciousness with reduced awareness of external stimuli and an increased response to verbal or nonverbal communications. Highly motivated mothers can learn self-hypnosis to dampen the perception of pain and the physiologic responses to pain. Currently, available evidence suggests that it does lead to increased maternal satisfaction and reduces the need for pharmacologic pain relief, including epidurals, in labor.⁶

Acupuncture involves the insertion of fine needles into the body to a depth of 2.5 to 3 cm at specified areas. There are about 400 acupuncture points and 20 meridians connecting these points. Each of the 20 meridians corresponds to an organ. The acupuncture points used in labor are on the hands, feet, and ears. Acupuncture is thought to stimulate the body to produce endorphins and thereby reduce pain. There are few studies concerning its use in obstetric practice, but it does appear to reduce pain and analgesic requirements in labor.⁷

Aromatherapy utilizes the healing power of plants, and reflexology involves manipulating and pressing parts of the feet. There is no strong evidence that either of these is effective in the management of labor pain. However, some mothers gain emotional support and satisfaction from the aforementioned alternative therapies and, because they are harmless, there is little reason to discourage their use.

PHARMACOLOGIC LABOR ANALGESIA

Inhalational Agents

Since Sir James Young Simpson began using chloroform ether for labor pain relief in 1847, volatile agents and anesthetic gases have been used in childbirth. In the United Kingdom and Europe, a mixture of 50% nitrous oxide and 50% oxygen (Entonox) is used extensively. Nitrous oxide has a low blood-gas partition coefficient and accordingly, a rapid onset and offset of action. It is self-administered through a mouthpiece incorporating a two-stage reducing and on-demand valve. Should the mother become drowsy, the delivery system will be released before unconsciousness occurs. Entonox needs to be inhaled for at least 45 seconds to achieve maximum analgesic effect, so deep inhalation must start as soon as the contraction is first felt. It may cause disorientation, drowsiness, and nausea in some mothers. However, it does relieve labor pain to some degree, and it is easy to use, inexpensive, has minimal accumulation with intermittent use, and is safe for mother and fetus.

Sevoflurane has a physical profile similar to nitrous oxide. As well as having a rapid uptake and washout rate, it is nonirritant. Some research has suggested that in subanesthetic concentrations (0.8%), sevoflurane provides better pain relief than Entonox in the first stage of labor.⁸ Sevoflurane may also be associated with less nausea and vomiting. Despite this, it has not been widely utilized because of the potential risk of somnolence and technical difficulties related to an effective scavenging system.

Systemic Opioids

MEPERIDINE

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