All About Epidural - Information summary on labor epidural

Executive Summary

What is epidural?

During epidural a special needle is inserted into the epidural space, which is the space just outside dura mater (or just dura), a tough membrane that forms a sack inside which spinal cord and nerves connected to it are suspended. Thin plastic catheter is passed through the needle and the needle removed.

Local anesthetic drugs and opioids injected into epidural space diffuse through the dura and interfere with the function of the nerve roots. As the result, all sensation, including pain, in areas supplied by the affected nerve roots will be reduced to the degree proportionate to the strength of local anesthetic mixture.

Epidural catheter may remain in the epidural space for hours and even days, and local anesthetics administered for as long as it takes for labor to progress.

What is spinal anesthetic?

During spinal anesthetic thin needle is advanced through the dura mater and anesthetic drugs are injected straight into the fluid surrounding spinal cord and nerve roots, which are then affected in the same manner as during epidural block.

What is the difference between epidural and spinal?

Epidural has relatively slow onset, between ten and thirty minutes for the full effect. Its advantage is that it can be maintained for as long as it takes to deliver the baby. This makes epidural more suitable for labor where time factor is uncertain.

The effect of spinal is fast, within minutes, and the block dense. Its duration is limited, and spinal anesthetic is most commonly used for procedures that are unlikely to last longer than and hour or two, such as cesarean section.

Why epidural?

Epidural is by far the most effective and reproducible method of pain relief in labor. In other words, it will produce superior pain relief every time it is administered to a woman in labor. Other modalities, such as opioid injections, nitrous oxide and non-pharmacological methods (doula support, massage, warm baths, TENS, acupuncture, aromatherapy and so on) are significantly less efficient and their effect much less predictable in each and every patient.

Are epidurals safe?

Labor epidurals have very good safety record, and hundreds of thousands of them are performed around the world every year without problems. However, like any other invasive medical procedure epidural analgesia can lead to complications and undesirable side-effects that may affect the mother and/or the baby. Serious complications of epidural are rare. Also, in spite of the absence of evidence, epidural is often blamed for things it doesn’t do or cause.

Indications for labor epidural

In the absence of contra-indications labor epidural should be provided on woman’s request. There is no evidence that initiating epidural in early labor leads to increased risk of cesarean, therefore it can be started at any time in labor.

Epidural is also indicated for prolonged and complicated labors and instrumental delivery.

Contra-indications for epidural

Absolute contra-indications:

  • Woman’s refusal
  • Allergy or increased sensitivity to drugs used in epidural
  • Infection at the site of insertion of epidural needle
  • Disorders of blood clotting leading to increased bleeding.

Relative contra-indications:

  • Anatomical abnormalities of the spine
  • Previous spinal surgery
  • Certain neurological conditions (such as multiple sclerosis)
  • Certain cardiac problems, such as mitral stenosis
  • Septicemia, the presence of bacteria in the blood.

In each patient the risk of complications is balanced against the benefits of epidural. For example, it is generally accepted that women with mitral stenosis benefit from epidural analgesia, either for their labor or cesarean section, even though this condition is a relative contra-indication.

Can epidural or spinal kill?

Fatalities from epidural anesthesia are extremely rare and happen in one of two ways: unexpectedly high block or local anesthetic toxicity. Even if these complications occur, if the patient is properly looked after they will be detected early and serious injury or death will be prevented.

In rare cases spinal block leads to severe slowing of heart rate and cardiac arrest. The survival depends on early recognition and aggressive treatment of this complication.

Paralysis from epidural

Paralysis is a rare devastating complication of epidural. It is caused either by epidural (spinal) hematoma, epidural abscess or direct injury to the spinal cord. Some cases of severe neurologic injury leading to paralysis is unexplained and may be the result. Overall incidence of severe neurologic injury is between 1:100,000 and 1:250,000 patients receiving labor epidural.

Epidural hematoma

Spinal canal that contains spinal cord is a rigid structure. If bleeding occurs in that area the pressure builds up and eventually leads to spinal cord compression and necrosis. Most patients who develop spinal hematoma have abnormal blood clotting due to congenital defects or medication. Epidural hematoma also more commonly occurs in patients where placement of epidural catheter is technically difficult and requires multiple attempts.

Symptoms of spinal hematoma are persistent or new loss of sensation and movement after epidural has been discontinued, as well as back pain. Final diagnosis is made on the basis of MRI or CT scan. Treatment of spinal hematoma is surgical: spinal canal is opened and blood evacuated. It is important that surgery is performed in the first eight hours of the development of hematoma, otherwise the damage is likely to be permanent.

Epidural hematoma is rare and occurs in approximately 5 – 6 out of 1 million patients receiving labor epidural (1: 170,000).

Epidural abscess

Epidural abscess is the result of infection in the epidural space. It damages spinal cord in a manner similar to that of spinal hematoma, by compression. In addition, it can directly erode neural structures.

Symptoms include pain, fever and neurological signs, such as loss of sensation and movement. Diagnosis is made by MRI.

Treatment consists of antibiotics and surgical evacuation of abscess. Success rate depends on early diagnosis and intervention.

Epidural abscess occurs in approximately 7 – 9 out of 1 million patients receiving labor epidural.

High block

Unexpectedly high spread of local anesthetic mixture may result in high block, resulting in drop in blood pressure and difficulty breathing. In severe cases high spread of local anesthetic may lead to paralysis of phrenic nerve that controls the movement of the main respiratory muscle and respiratory arrest. High block may also be accompanied by significant drop in blood pressure.

Incidence of this complication is low, and according to one study it was observed in 0.07% of patients with epidurals.

Treatment is supportive and depends on symptoms and their severity. Breathing is supported if necessary, and in rare cases the patient may require artificial ventilation for several hours. Blood pressure is maintained with medication. The level of the block usually subsides rapidly, and usually within one hour symptoms should resolve.

Failure of epidural

According to the latest and one of the most comprehensive clinical reviews up to 12% of labor epidurals did not provide adequate pain relief. However, almost half of these could be corrected by simple manipulations: administration of additional dose of local anesthetic mixture, partially withdrawing the catheter or changing patient’s position. About 7% of patients had to have their epidurals re-done.
Epidural failure occurs due to various reasons, such as incorrect catheter placement or anatomical abnormalities. Less commonly epidural failure is due to subdural-extra-arachnoid block discussed in separate section.

What is post-dural puncture headache

Post-dural puncture headache, or PDPH, is a complication of spinal anesthesia or inadvertent dural puncture by epidural needle and is caused by the leak of cerebro-spinal fluid. The headache usually becomes apparent within 24 hour from administration of epidural or spinal and is located in fronto-occipital areas. It is aggravated by upright position, bright light and loud sound and may be accompanied by nausea and vomiting.

Depending on the source, reported incidence of PDPH is between 0.3 and 3%. Diagnosis is clinical, also based on the exclusion of other possible causes of headache: migraine, meningitis, cerebral aneurism etc.

Initial treatment is conservative and consists of increasing fluid intake and painkillers. If not resolved within 24 hours blood patch is indicated, whereby patient’s blood is injected into the epidural space and seals the defect leading to leakage of CSF.

Temporary neurologic deficit

Temporary neurologic deficits are loss of sensation and/or motor function following neuraxial blockade for less than one year. Reported incidence varies significantly. It is also unclear if temporary neurologic deficits are caused by epidural or spinal or actual birthing process.

Local anesthetic toxicity

Local anesthetics are toxic drugs which, if inadvertently administered into the circulation in sufficient quantities, may cause nausea, vomiting, confusion, seizures, arrhythmias and cardiac arrest. Bupivacaine is the most toxic local anesthetic, while ropivacaine seems to be the safest.

Standard procedure of administering labor epidural includes measures aimed at reducing inadvertent administration of local anesthetics into the bloodstream. In recent years ropivacaine, the safest local anesthetic, has become most popular drug used for labor epidural. Moreover, its concentration and quantity are low and unlikely to cause adverse effects associated with toxicity, even when full dose is administered intravenously. As the result, overall incidence of local anesthetic toxicity (including non-life threatening reactions) is low, probably around 0.13%. This number includes all toxic reactions, not only those observed in obstetric anesthesia.

In recent years the outcome of local anesthetic toxicity has been considerably improved by using Intralipid, the suspension of lipids commonly used for intravenous nutrition of critically ill patients. Intralipid binds local anesthetic molecules and facilitates their removal in cases of serious toxicity.

Extra-arachniod block

Also called subdural or subdural-extra-arachnoid block, it is characterized by slow onset of epidural block, its unexpectedly high distribution, slow onset of various degrees of muscle weakness and, in rare cases, Horner’s syndrome and trigeminal nerve palsy. This complication occurs when local anesthetic mixture is inadvertently placed between dura mater and arachnoid mater.

The incidence varies. It seems that though some subdural spread of local anesthetic can be observed by x-ray relatively frequently, symptomatic subdural block is rare, probably around 0.024% as stated by one large observational study.

Treatment is symptomatic. In vast majority of patients subdural block resolves spontaneously after discontinuation of epidural infusion. Defective epidural catheter is removed and another epidural performed at higher or lower level.

Transient Neurologic Syndrome

Transient Neurologic Syndrome, or TNS, is a complication of neuraxial anesthesia, more common after spinal block. It is rare in modern days and is characterized by pain in the lower extremities: buttocks, thighs and legs after the spinal has worn off. Pain is usually burning, cramping or aching in character. There are no abnormalities on neurological examination.

Vast majority of patients who develop TNS had lignocaine used in their spinals, though it has been observed with other local anesthetics as well. TNS is very rare after epidural anesthesia.

Treatment of TNS is aimed at relieving pain. Symptoms typically disappear within 24 hours, though in rare instances they may last for several days.

Cauda Equina Syndrome

Cauda Equina Syndrome (CES) is a serious complication of neuraxial anesthesia. It results from the dysfunction of multiple lumbar and sacral nerve roots that supply lower limbs and perineum. CES is diagnosed only when symptoms include impairment of bladder, bowel, or sexual function, and perianal (“saddle”) numbness. Impairment of bladder function can manifest either as urinary incontinence – inability to hold urine – or retention, or difficulty of urinating. Bowel dysfunction manifests as fecal incontinence, inability to control bowel movements. The symptoms of impaired sensory or motor function in the lower limbs may or may not accompany CES. Long term prognosis of this complication is poor, and it is likely result in permanent disability.

CES has initially been observed after continuous spinal anesthesia with 5% lignocaine administered for prolonged periods of time through spinal microcatheters. Currently, neither spinal microcatheters nor lignocaine at this concentration are used in obstetric anesthesia, and as the result CES in obstetrics is very rare.

Risk of caesarean section

Currently there is no evidence to support earlier claims that labor epidural administered in accordance with current professional guidelines may increase the risk of caesarean section, as confirmed by various studies. There are many factors that influence cesarean birth rates, and epidural analgesia is just one of them. The way labor epidural is administered – concentration and quantity of local anesthetic mixture, choice of local anesthetic – may play a role in modifying the risk of caesarean section. There is no difference in caesarean section rates between women receiving epidural early in labor or during its later stages.

Prolongation of labor

There is some evidence that labor epidural makes prolongs second stage of labor. On the other hand, some studies demonstrated that superior pain relief by epidural may in fact reduce the duration of labor. There are many other, more significant factors that may prolong labor, such as parity, maternal age, position of the fetus, body mass index and others. Incidentally, these factors are also associated with increased use of epidurals. Most importantly, there is no evidence that longer labours associated with the use of epidural leads to adverse effects in babies.

Chronic back pain

Back pain is common during and after pregnancy. It is likely to be caused by the production of relaxin, hormone leading to increasing laxity of ligaments of the spine and pelvis, as well as unfavourable body position due to large fetus. There is no difference between the incidence of back pain between those receiving labor epidural and those using other methods of pain relief.

Instrumental delivery

Labor epidural is associated with higher use of instrumental forceps and vacuum to assist childbirth. Causes remain controversial. Epidural may affect the woman’s ability to push during the second stage of labor. On the other hand, obstetrician use forceps and vacuum more willingly on patients with working epidurals because of superior pain relief. Epidural does not increase the use of forceps and vacuum because of dystocia (obstructed labor). Even though labor epidural may lead to increased use of forceps and vacuum, it is not associated with increased incidence of perineal tears. One randomized study has demonstrated that the incidence of instrumental delivery is reduced when lower concentration of local anesthetic is used in epidural mixture. It is likely that the use of 0.2% ropivacaine, which is popular in modern labor epidurals, is associated with reduced use of forceps and vacuum. However, studies are needed to derive definite statistics.

Breastfeeding

Opioids in local anesthetic mixture used for labor epidural are absorbed from the epidural stream into the bloodstream and eventually enter the fetus. Potentially it can lead to sedation of the newborn baby and interference with its attempts at breastfeeding. The results of earlier observational studies are conflicting. Based on the latest properly conducted randomized studies there is no evidence that labor epidural negatively affects breastfeeding.

Fever and neonatal evaluation for sepsis

Women who have labor epidural are more likely to develop significant fever compared to those using other methods of pain relief. On the other hand, other factors are involved in the development of fever, such as duration of labor and primiparity. Potentially raise in maternal temperature may lead to unnecessary evaluation and treatment of newborns for sepsis, which includes blood tests and antibiotics. However, as the popularity of labor epidural increases pediatricians become more familiar with this potential side-effect and are less likely to conduct unnecessary investigations.

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