Contraindications - when an epidural cannot be given

Contraindications – when we cannot give an epidural


The benefits of epidural must outweigh its risks by a large margin. When risks of severe complications are high neuraxial blocks – labor epidural or spinal for cesarean section – must not be performed.

Contra-indications are divided into absolute and relative. As the rule, in the presence of absolute contraindications epidural cannot be used. When relative contraindications are present the risk of epidural is higher, however in special circumstances it can be administered if risks are outweighed by benefits. The decision in such cases is always taken after discussing the risks with the patient.


Absolute contraindications to neuraxial anesthesia:

Woman’s refusal

Patient’s autonomy is the basic human right, and no procedure may be performed without consent. Violating this rule is equivalent to physical assault and constitutes an offence.

When giving the consent for a procedure it is crucial that the patient understands its nature, the risks and the benefits. This – to provide thorough understanding of the options of pain relief in labor – is the ultimate purpose of this site. The assessment of risk is also a personal process, and the decision to proceed with epidural or not must be treated with respect and understanding by everyone else. All others involved in childbirth – the family members, midwives, doctors, birth educators – can only act as advisers and cannot force the decision on the woman. The opposite is also true, and nobody should discourage the woman from using labor epidural because it is in conflict with their beliefs.

Coagulopathy

Coagulopathy is the inability of blood to form clots. This contraindication relates to the worst fear of patients receiving epidural: becoming permanently paralyzed.

Coagulation – the ability to form clots – is one of the functions of blood. When human tissue is damaged certain chemicals are released which attract platelets and trigger the chain of biochemical reactions, the cascade of coagulation. The final result of the process is the conversion of soluble protein fibrinoged into insoluble fibrin. Interlaced with platelets it forms a plug that closes the damaged blood vessels and stops the bleeding.

Epidural space contains veins, and when epidural needle is introduced into the space these veins are often damaged. In the presence of normal blood physiology it does not lead to problems: a clot is formed and the bleeding in the epidural space is quickly terminated. However, if for some reason the ability of blood to coagulate is impaired the bleeding continues and leads to the development of epidural (or spinal) hematoma. As the result the spinal cord becomes compressed and its blood supply becomes compromised. After several hours the damage becomes irreversible, and the patient develops permanent paralysis.

Coagulopathy can be congenital or acquired. The former is the result of inborn defects, and the nost common examples are hemophilia and Von Willebrand’s disease. The severity of these conditions varies from patient, however in the majority of cases by the time of childbirth the condition is diagnosed and the woman is aware of it. In less common cases coagulopathy may be detected by blood tests during routine pre-natal workup. Acquired coagulopathy is caused either by pathological conditions or medication. The condition of particular concern in laboring woman is pre-eclampsia, relatively uncommon complication of pregnancy that is characterized by elevated blood pressure and the presence of protein in the urine. Small proportion of patients who develop pre-eclampsia also develop so called HELLP syndrome. The abbreviation stands for Hemolysis, Elevated Liver enzymes and Low Platelets, HELLP. If the platelet count in the blood falls below certain level coagulation is impaired. Normal platelet count is between 200,000 and 400,000, and levels above 100,000 are considered safe when performing an epidural. Levels below 75,000 are considered an absolute contraindication to neuraxial block by most anesthetists.

Drugs causing coagulopathy may be divided into two large groups. The first one includes drugs that have been specifically designed to reduce the ability of the blood to clot. Typical representatives are heparin and warfarin, which are prescribed in conditions such as deep vein thrombosis and pulmonary embolism, as well as some problems in pregnancy. These drugs are powerful in terms of their ability to impair coagulation and their use is generally accepted as the absolute contra-indication to epidural. The second group of drugs represents medication which are prescribed for other purposes but their side-effect is interference with coagulation, to various degrees. Such drugs include aspirin and NSAIDs, non-steroidal anti-inflammatory drugs used as analgesics. Generally in the presence of these drugs the risk of spinal hematoma is not increased, and epidural can be performed. However, caution should be taken when other risk factors are present.

Every anesthetist who performs labor epidural makes sure that no coagulopathy is present by asking relevant question, examining the patient and, if necessary, checking relevant blood tests. Typical questions are: “are you taking any medication that may interfere with blood clotting” and “do you experience significant or even excessive bleeding that is difficult to stop from minor cuts?” If the answer to these is yes, further questioning will follow. Routine blood tests ordered in ante-natal clinic include coagulation screening, and it is unlikely that serious clotting disorders will be missed.

Infection at the site of epidural injection

Labor epidural is performed with sterile equipment using aseptic technique in order to avoid septic complications. If epidural or spinal needle passes through the infected area on the skin infectious flora will be introduced into the epidural space and cause epidural abscess. Epidural abscess is discussed in detail in the chapter on severe neurological injury.


Relative contraindications:

As mentioned above, relative contra-indications constitute situations where going ahead with epidural may be associated with increased risk of complications. The presence of such contraindications does not mean that the woman is automatically denied labor epidural, however certain factors are taken into account and some aspects of practice and/or technique are modified as necessary. Most common relative contra-indications to neuraxial anesthesia are listed below.

Abnormal anatomy of the spinal column

Giving an epidural to a patient whose spine is deformed, either due to a disease or spinal surgery – is technically more difficult, may take longer time and generally may cause more tissue trauma than usual. This may increase the risk of complications. Several studies have demonstrated that serious complications of labor epidural happen more often where the procedure has been technically difficult and required multiple attempts. Severity of anatomical abnormalities varies, and some spinal deformities, such as scoliosis related by incorrect posture, are very common in the modern society. Therefore, each case is considered on individual basis. If necessary the technique of needle insertion is changed, and in some cases paramedian approach can be used. When employing this technique epidural needle is inserted not in the midline but between one and two centimeters to either side of the spine. In case of serious spinal deformities diagnosed in ante-natal clinic MRI may be performed in order to identify the best ways of establishing working epidural with minimal attempts. If serious spinal deformities are present epidural is usually performed by more senior, more experienced anesthetist.

Septicemia

Septicemia is the presence of significant amount of micro-organisms in the blood. Septicemia often accompanies various infections, such as pneumonia or pyelonephritis (the infection of the kidney). When the needle is passed through tissue it is possible to introduce microbes into the epidural space which, in turn, may increase the risk of infectious complications, such as epidural abscess or meningitis.

The risk of epidural abscess with septicemia is considerably lower than that when epidural is performed in the presence of skin infection at the site of needle puncture. Severity of septicemia varies, and every case must be considered individually. In the presence of serious bacterial infection associated with fever significant fever epidural is best avoided. If benefits outweigh the risks the antibiotics are given to the patient before performing the block.

Special case of septicemia is that caused by Human Immunodeficiency Virus, or HIV. The virus may be present in the blood for years without the symptoms of AIDS. At some time it has been hypothesized that by doing epidural or spinal block in HIV-positive patient HIV viruses may be transferred from blood to neural structures and accelerate the development of neurological complications of AIDS. This theory was eventually disproven, and HIV-positive patients can safely receive spinal and epidural anesthesia when indicated.

Neurological disease

During neuraxial block the needle and the catheter are placed in close proximity of the spinal cord and its surrounding structures: the dura and nerve roots. The needle causes small trauma to the tissues, and this process is accompanied by some degree of inflammation. In addition, drugs in the epidural mixture affect neural tissue to some degree. At least in theory, the combination of these factors may lead to worsening of chronic neurological disease, such as multiple sclerosis.

The evidence regarding the effect of epidural on neurological disease is controversial and inconsistent. However, any new neurological symptoms are likely to be attributed to epidural. Because of this many anesthetists are reluctant to administer epidurals in patients with neurological disease.

This is a relative contra-indications, and epidural can still be performed in patients with such conditions after appropriate discussion of possible complications with the patient. As the rule, it is safe to administer epidural or spinal in the presence of stable disease. Existing neurological signs must be carefully documented and the patient thoroughly examined after delivery and removal of epidural.

Severe aortic or mitral stenosis

The heart has four valves, of which aortic and mitral have the most impact on cardiac function when they become diseased. Stenosis means narrowing of the valve, so that the blood flow through it is impaired.

Epidural causes vasodilatation of the blood vessels in the areas of the body affected by the block, and as the result the blood pressure drops. Normal physiological response to this decrease is the increase in cardiac output, the amount of blood the heart pumps through the vessels. This way the pressure in the arterial system and the amount of oxygen delivered to the tissues remains constant.

The aortic and mitral valves are positioned in the left ventricle, the chamber of the heart that supplies the blood to most organs of the body. Narrowing – stenosis – of either of these valves – limits the ability of the left ventricle to increase cardiac output. In such patients the decrease in blood pressure cannot be compensated by normal physiological response, and blood supply to vital organs – including the heart muscle itself – decreases to unacceptably low levels. This can lead to serious complications and, in severe cases, death.

Normal area of the mitral valve area is 4 to 6cm2. Symptoms occur when it narrows below 2cm2, and severe stenosis is diagnosed when it decreases to below 1cm2. The area of normal aortic valve is 3 to 4cm2, with severe stenosis diagnosed at the area below 1cm2.

Stenosis of mitral or aortic valve is listed as relative contraindication to epidural, and in some clinical scenarios epidural may even be beneficial to patients with these conditions. An example of such scenario is anesthesia for cesarean section in a patient with mitral stenosis.

Patients with mitral stenosis do not tolerate significant increases in heart rate, or tachycardia. On the other hand, tachycardia is common during cesarean section performed under general anesthesia, either during the induction or surgical stress. To avoid sharp changes in heart rate cesarean section is best performed under epidural anesthesia. The onset of epidural block is relatively slow, between ten and twenty minutes, and vasodilatation can be counteracted by administering vasoconstrictors, drugs that increase vascular tone. Analgesia achieved by epidural block is superior to that of general anesthesia, and as the result hemodynamic parameters remain stable during surgery, and the chance of adverse effects of anesthesia is reduced.

On the other hand, in the presence of mitral or aortic stenosis spinal block is generally avoided. The onset of spinal is fast, and significant vasodilatation may occur within seconds of spinal injection, leading to dangerous cardiovascular collapse.

In the presence of most contraindications the decision to proceed with epidural or spinal is tailored to the needs of particular patient. The risk of complications is always weighted against established benefits. Ensuring understanding of the situation by the patient is imperative.

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Dr. Eugene Smetannikov is a practicing anesthesiologist with the interest in obstetric anesthesia. He is the author of the most comprehensive book on the subject, The Truth About Labor Epidural