Neuraxial Labor Analgesia - Indications and Contraindications

Introduction:

Labor pain is among the most challenging experiences that women have in their lives. Painful labor causes physiological changes in the mother, which can impact both the mother and the child. In response to labor pain, the maternal catecholaminergic surge in norepinephrine and epinephrine tends to increase maternal oxygen uptake, which may result in incoordinate uterine action, resulting in decreased placental perfusion. In some cases, increased maternal oxygen uptake may harm the mother's and infant's health. Furthermore, maternal hyperventilation concerning labor pain has negative consequences, such as decreased fetal oxygen delivery. Aside from these acute maternal and fetal hemodynamic and metabolic responses, severe labor pain has been associated with the emergence of postpartum post-traumatic stress, postpartum depression, and chronic pain.

The most effective method for pain relief during labor is neuraxial analgesia. According to Hiltunen et al., neuraxial analgesia may decrease the likelihood of postpartum depression. Because of the benefits of neuraxial analgesia, its use for labor analgesia has steadily increased over the last few decades. However, one of the main reasons patients refuse neuraxial analgesia is complaints about how it might affect the course and outcome of labor. As a result, anesthetists must provide accurate, up-to-date information to pregnant women seeking labor pain relief about the effects of neuraxial analgesia on labor outcomes.

What Are the Stages of Labor?

Three stages of labor have been identified:

• The first stage lasts from the beginning of the cervical change to dilatation of ten centimeters. The latent stage can last up to eight hours without intervention. Finally, the active phase is connected with a faster rate of cervical dilatation and lasts for two to six hours.

• The second stage of labor lasts from complete cervical dilatation (10 centimeters) to baby delivery. The second stage usually lasts for two hours (approximately three hours with regional anesthesia) in primiparous and one hour (about two hours with regional anesthesia) in multipara.

• The third stage begins with the baby's delivery and ends with the detachment and ejection of the placenta and membranes.

What Are the Pain Pathways Associated during Labor?

• Labor pain is regarded as regular, painful contractions of the uterus that increase in intensity and frequency as the labor progresses. It possesses both a visceral and a somatic component.

• Visceral pain is caused by uterine contractions and dilatation of the cervix. These pain impulses are carried by afferent, slow-conducting A-delta and C fibers that travel with the sympathetic nerves and enter the spinal cord between the Tenth thoracic and first lumbar vertebrae. In addition, the descent of the fetal head and successive pressure on the pelvic floor, vagina, and perineum cause somatic pain, which is transferred by the pudendal nerve as labor progress (second sacral to fourth sacral).

• Supraspinal pain pathways begin with ascending pathways projecting to the pons and medulla, activating cardiorespiratory control centers and descending pathways together with the thalamus, which in turn pass projections to the anterior cingulate, motor, somatosensory, and limbic regions with projections to the cortex, actually results in the sensory-emotional experience of pain.

What Are the Methods of Pain Relief during Labour?

• Providing safe and effective analgesia during labor has yet to gain widespread acceptance, and it is associated with myths and controversies, making it even more difficult.

• The ideal local anesthetic for labor analgesia should produce a consistent sensory block, no motor block, no tachyphylaxis, and have a low risk of inadvertent overdose or accidental intravenous administration. Some drugs used are Fentanyl, sufentanil, Morphine, and Diamorphine.

• A comprehensive maternal history and physical examination should be performed for all women having labor analgesia to identify obstetric and anesthetic risk factors. The spine should be examined for structural deformity, obesity, and local edema that may obscure spinal alignment and make neuraxial access difficult. The fetal status should be determined and informed permission acquired.

What Are the Indications and Contraindications of Neuraxial Analgesia?

Indications:

1. Continuous Lumbar Epidural: Pain relief was requested by the mother (technique of choice for local anesthesia).

2. Combined Spinal-Epidural Analgesia:

   1. To begin early local anesthesia.

   2. In advanced labor, for immediate pain relief.

   3. Difficult spine and obesity.

   4. Epidural catheter resting for poor pain relief.

3. Single Shot Spinal:

   1. Severe pain and agitation in a parturient in advanced labor.

   2. For instances where there are limited resources.

4. Continuous Spinal Analgesia:

   1. Difficult epidural catheter placement due to earlier spine surgery and morbid obesity

   2. Airway obstruction.

   3. Severe heart disease

   4. Salvage technique after an accidental dural puncture during labor epidural was used.

5. Dural Puncture Epidural Analgesia:

   1. To enhance the effectiveness of epidural analgesia.

   2. To begin early local anesthesia.

   3. In advanced labor, for immediate pain relief.

   4. Difficult spine and obesity.

   5. Epidural catheter resting for poor pain relief.

Contraindications:

1. Absolute:

   1. Coagulation disorders and bleeding disorders.

   2. Any infection at the site.

   3. Elevated intracranial pressure.

   4. Any allergic reaction to the local anesthetic drugs.

   5. The patient refused even after senior anesthetist counseling.

2. Relative:

   1. Established neurological disorder.

   2. Severe anatomical spine deformity.

   3. Fixed cardiac output status.

   4. Thrombocytopenia.

   5. The patient is receiving prophylactic low-dose Heparin therapy.

   6. The patient is unwilling to cooperate.

What Are the Advantages and Disadvantages of Neuraxial Techniques for Labor Analgesia?

Advantages:

1. Continuous Epidural Analgesia:

   1. Continuous analgesia is provided.

   2. No need for a dural puncture.

   3. Capacity to transform from analgesia to anesthesia for cesarean delivery.

2. Combined Spinal-Epidural Analgesia:

   1. Low doses of local anesthetics and opioids are required.

   2. Analgesia starts rapidly.

   3. Fast onset of sacral analgesia.

   4. In the early stages, opioids alone provide complete analgesia.

   5. Lower rate of failed epidural analgesia.

3. Continuous Spinal Analgesia:

   1. Continuous analgesia.

   2. Common local anesthetic and opioid doses.

   3. Analgesia begins quickly.

   4. Capability to extend analgesia to anesthesia for cesarean delivery.

4. Single Shot Spinal:

   1. Simple technically.

   2. Analgesia begins quickly.

   3. Rapid sacral analgesia.

   4. Low doses of drugs are required.

5. Dural Puncture Epidural Analgesia:

   1. Onset is immediate, superior quality When compared to epidural blocks.

   2. Onset is earlier for sacral analgesia compared to continuous epidural infusion.

   3. Low occurrence of side effects.

   4. Fewer physician-administered additional doses of anesthetics.

   5. Very low incidence of asymmetrical blocks.

Disadvantages:

1. Continuous Epidural Analgesia:

   1. Analgesia with a gradual onset.

   2. When compared to spinal techniques, higher drug doses are required.

   3. The risk of maternal systemic toxicity is more elevated.

   4. High fetal drug exposure.

2. Combined Spinal-Epidural Analgesia:

   1. Verification of a properly placed and functioning epidural catheter is delayed.

   2. Pruritus is becoming more common.

   3. Increased risk of fetal bradycardia.

3. Continuous Spinal Analgesia:

   1. The risk of postdural puncture headache increases with the size of the dural puncture.

   2. If the spinal catheter is mistaken for an epidural catheter, there is a risk of overdose and total spinal anesthesia.

4. Single Shot Spinal:

   1. Analgesia for a limited time,

   2. The procedure may have to be repeated.

   3. Maternal hypotension is more likely.

5. Dural Puncture Epidural Analgesia:

   1. The risk of postdural puncture headache may increase with a larger dural puncture.

   2. Compared to the continuous spinal epidural, the onset of analgesia is delayed.

What Are the Complications of Regional Analgesia in Labor?

1. Immediate and Severe Complications:

   1. Misplaced injection into intravascular, intrathecal, or subdural space.

   2. High or total spinal block.

   3. Decrease in blood pressure.

   4. Convulsions caused by a local anesthetic.

   5. Cardiac arrest caused by local anesthetic.

2. Delayed Complications:

   1. Postdural puncture.

   2. Temporary backache.

   3. Permanent neurological deficit.

   4. Retention of urine.

   5. Epidural hematoma, abscess, or infection of the meninges.

Conclusion:

Studies to improve obstetric results in women who prefer neuraxial analgesia must continue and must be customized analgesia techniques to the requirements of individual patients. Improving the protocol with ultra-low-dose (0.1 percent ) local anesthetic-opioid solutions reduces adverse effects on labor progress and outcome while enhancing analgesia, patient satisfaction, and reducing motor block.