Generality
The epidural, or epidural anesthesia, is a particular technique of local anesthesia, characterized by the injection of anesthetics and analgesics at the level of the epidural space of the spinal cord.
The main medical circumstances that may require an epidural are childbirth, caesarean section and chest, knee or hip surgery.
The realization of an epidural is normally a doctor specialized in local and general anesthesia practices, that is the anesthesiologist.
An epidural is a safe, effective method that does not involve the patient falling asleep.
Brief anatomical revision of the spine
Supporting axis of the human body, the vertebral column or spine is a bone structure of about 70 centimeters (in the adult human being), which includes 33-34 vertebrae stacked on each other.
The vertebrae of the spine have a general structure quite similar to each other. In fact, they all have
- a body (anteriorly),
- an arch similar to a horseshoe (back)
- a vertebral hole, deriving from the union of the arch to the body.
The vertebral holes of each vertebra coincide and this determines the formation of a long canal - the so-called spinal canal or vertebral canal - which serves to house the spinal cord .
The spinal cord is, together with the brain, one of the two elements that make up the central nervous system ( CNS ).
What is an epidural?
Epidural or epidural anesthesia is a type of local anesthesia . Its execution generally rests with an anesthesiologist and involves the injection of anesthetics and painkillers (or analgesics) at the level of the spinal canal of the spine, to be precise in the so-called epidural space .
Figure: injection into the epidural space
The epidural space is the space between the outer surface of the dura mater of the spinal cord (NB: the dura mater is one of the three meninges of the CNS) and the internal bone wall of the spinal canal, formed by the vertebral holes.
In the epidural space there are lymphatic vessels, spinal nerve roots, loose connective tissue, adipose tissue, small arteries and a network of venous plexuses.
IS IT DIFFERENT FROM THE SPINAL ANESTHESIA?
Despite what many believe, epidural anesthesia and spinal anesthesia are two different types of local anesthesia.
In the case of spinal anesthesia, the anesthesiologist injects anesthetics and analgesics into the subarachnoid space of the spinal cord.
The subarachnoid space of the spinal cord is the space filled with cerebrospinal fluid (or cerebrospinal fluid), between the meninge called arachnoid and the meninge known as dura mater.
EPIDURAL INTENSE AS ADJECTIVE
Initially, the word "epidural" was used as an attribute of any injection of substance - be it an anesthetic, an analgesic, an anti-inflammatory or a diagnostic contrast medium - at the level of the epidural space.
Over time and due to the fact that it was often referred to the anesthetic practice mentioned above, the term has changed connotation, becoming in fact a noun (in fact we speak of "an epidural" or "the epidural")
ORIGIN OF THE NAME
The term "epidural" derives from the union of the prefix of Greek origin "epi" (ἐπί), which means "above", to the word "durale", which refers to the dura mater.
Thus, the literal meaning of "epidural" is "above the dura mater".
uses
The purpose of a local anesthesia is to cancel the pain sensation in a specific anatomical area of the human body, without putting the patient to sleep.
In the specific case of an epidural, the purpose of the latter is to cancel the sensitivity to pain in a large part of the trunk and along all the lower limbs.
After this necessary premise, the medical circumstances that, for the pain they produce, generally require the use of an epidural are:
- A painful, complicated and / or prolonged labor.
- A birth that involves the birth of two or more twins.
- An assisted birth, that is a birth that requires, for the birth of the child, the use of forceps or suction cup.
- Cesarean section .
- Knee, hip, thoracic and back surgery, and surgery to amputate one or both lower limbs.
- The presence of chronic pain in the lower part of the body due to a terminal illness. In these situations, the epidural is a palliative cure.
The annulment of the painful sensation extended to the whole body and the sleep of the patient are a prerogative of the so-called general anesthesia .
Preparation
If the epidural is part of a planned surgery, the doctor recommends to the future patient that, on the day of the procedure, he must be fasting from solid food for at least 6-8 hours and fasting from liquids for at least 2-3 hours.
Procedure
The first step in the correct execution of an epidural is that the patient, once he has settled on a hospital bed, takes up a position with his back that allows anesthetic and analgesic injection into the epidural space.
The positions that make it possible to reach the epidural space, through the tools for pharmacological infusion, are two:
- Sitting position, with the back bent forward.
- Position lying on one side and with knees bent.
These two positions of the body favor the insertion of the instruments for injection, because they "open" those spaces between the vertebrae, in which the anesthesiologist will have to infuse the anesthetics and analgesics.
The phase dedicated to the placement of instruments for pharmacological infusion consists of three stages:
- Injection point sterilization . The anesthesiologist will sterilize by rubbing a small cloth or piece of cotton in the area of interest, soaked in a sterilizing solution.
- The insertion in the spinal canal, through the perforation of the skin, of a needle-cannula . A generic needle-cannula is a hollow needle, of discrete dimensions, which allows the passage inside it of small tubes (or catheters) for the infusion of drugs.
- The introduction of a small plastic tube - the so-called epidural catheter - inside the cannula needle and its placement in the epidural space. The epidural catheter is the instrument for the infusion of anesthetics and analgesics.
The anesthesiologist starts the pharmacological injection only once he has properly placed the epidural catheter.
Generally, after a few minutes from the beginning of the pharmacological infusion, the anesthesiologist tests the effects of anesthetics on the patient, to realize if everything is proceeding correctly.
A classic test for evaluating the effects of anesthesia is to spray a cold spray solution on the anesthetized areas and to ask the patient for a description of the sensation.
When the pharmacological infusion is no longer necessary (for example at the end of the caesarean section), the anesthesiologist interrupts the anesthetic and analgesic administration and first withdraws the epidural catheter and then the needle-cannula.
SENSATIONS AND TYPICAL EFFECTS OF AN EPIDURAL
When the anesthesiologist inserts the needle-cannula or the epidural catheter, the patient may experience a slight discomfort or short-term pain, at the level of the insertion zone.
In some circumstances, it is even possible that the positioning of the epidural catheter determines a sensation similar to an electroshock: this occurs when the plastic tube grazes the roots of the spinal nerves located in the epidural space.
Typically, shortly after the injection of anesthetics and other medications begins, the patient begins to experience a warm numbness in the lower back and along both lower limbs. Furthermore, it warns that the legs gradually become heavier and more difficult to move.
Usually, the drugs used for an epidural reach the peak of their effects (anesthetics and analgesics) after 20-30 minutes from the beginning of the administration .
It is highly probable that anesthetics cancel bladder sensitivity . This means that the patient is unable to "feel" if the bladder is full or needs to urinate.
Types of epidurals
There are two types of epidural: the classical epidural (or regular epidural) and the mobile epidural (in English, it is called the walking epidural ).
The classical epidural involves the administration of anesthetics so that the patient can no longer move his lower limbs and feels a very significant sense of numbness.
The mobile epidural, on the other hand, provides a more contained administration of anesthetics and does not induce the same heaviness and the same numbness as a classical epidural.
DURATION OF EFFECTS
The effects of an epidural last as long as the anesthesiologist continues to administer the prescribed medications.
At the conclusion of the administration, the sense of numbness, the insensitivity to pain and the feeling of heaviness in the legs begin to gradually disappear until the complete disappearance.
In general, the patient must wait 1 to 3 hours before everything returns to normal.
Parallel to the disappearance of the sense of numbness, etc., the progressive recovery of bladder sensitivity also takes place.
Main differences between epidural anesthesia spinal anesthesia:
- An epidural produces the same anesthetic and analgesic effects as spinal anesthesia with higher pharmacological quantities (an epidural of 10-20 milliliters is equivalent to a spinal anesthesia of 1.5-3.5 milliliters).
- The effects of an epidural appear more slowly, compared to the effects of spinal anesthesia.
- The injection for an epidural can take place in any section of the vertebral column (cervical, thoracic, lumbar or sacral), while the injection for spinal anesthesia can only occur below the second lumbar vertebra.
- The procedure for placing the plastic tube, for pharmacological injection, is simpler in the case of an epidural.
AFTER AN EPIDURAL
After an epidural, the patient should observe a short period of rest, in a sitting or lying position. Generally, it is a rest of a few hours.
During this time, the medical staff offers maximum assistance to the patient and periodically monitors the vital parameters (blood pressure, heart rate, body temperature, etc.).
If the patient complains of annoying pain at the needle-cannula insertion zone, the doctor may resort to using painkillers, such as paracetamol.
DRUGS USED
The typical local anesthetics, used for an epidural, are: bupivacaine, chloroprocaine and lidocaine.
The most common analgesics, however, are: fentanyl and sufentanil.
On the occasion of an epidural for a birth, the administration of local anesthetics and painkillers requires the use of additional pharmacological substances, such as epinephrine and / or clonidine: these medicines serve not only to prolong the effects of the same anesthetics and painkillers, but also (and above all) to stabilize the pregnant woman's blood pressure.
Risks and complications
An epidural is a safe local anesthetic technique that rarely leads to complications.
The possible adverse effects and possible complications of an epidural include:
- Hypotension . Hypotension is the most frequent adverse effect of an epidural. It is caused by anesthetics, which, in addition to "blocking" the nerve endings that regulate pain, also "block" the nerve endings of the blood vessels.
- Reduced bladder control . As stated, it derives from a compromised bladder sensitivity.
- Skin itching . It can result from the combination of anesthetic drugs and analgesic drugs.
- Sense of nausea and vomiting . If the patient complains of nausea and vomiting, doctors may prescribe certain anti-nausea and anti-vomiting medications.
- Backache . Doctors believe that it can arise because the patient remains in a certain position with his back for a long time.
- Strong headache . Epidural headaches appear when the anesthesiologist accidentally stings the dura mater of the spinal cord, causing little damage to it.
It is a complication that occurs once every 500 epidurals or so.
- Development of an infection at the injection site . It is a complication that can develop several weeks after the operation that made an epidural necessary.
An infection can result in an abscess. An abscess in the epidural space could cause neurological damage to the peripheral nerve roots.
Such neurological damage can compromise the ability of movement of the lower limbs (paraplegia).
- Formation of an epidural hematoma . It is a collection of blood in the epidural space, which is formed as a result of the involuntary puncture, with the epidural catheter or the needle-cannula, of a venous blood vessel.
Serious complications, fortunately very rare (1 case every 80, 000 - 320, 000), of an epidural: |
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WHY IS EPIDURALITY NOT WORKING?
The epidural is not always successful.
Among the reasons that could compromise its correct implementation are:
- The inability to reach the epidural space with the epidural catheter.
- Failure to spread anesthetic in the epidural space, once injected.
- The exit of the epidural catheter from the injection site.
Contraindications
Doctors believe that an epidural is not possible when:
- The patient is allergic to one of the prescribed anesthetic drugs.
- The patient is taking an anticoagulant drug, such as warfarin . This type of recruitment predisposes to bleeding.
- The patient suffers from some congenital coagulation disease, which predisposes to bleeding. One of the best known congenital coagulation disorders is haemophilia .
- In the past, the patient underwent back surgery .
- The patient has severe back problems .
- The patient has some serious spinal deformity or suffers from a severe form of arthritis in the spine .
- The patient suffers from neurological problems due to some spinal cord malformation. One of the best known spinal cord malformations is spina bifida .
Results
An epidural is a type of local anesthesia that is very effective in relieving pain.
Just to give an idea of how much its anesthetic power is appreciated, the outcome of a US statistical survey regarding pregnant women is reported: according to this study, in the USA, more than 50% of pregnant women giving birth in the hospital are favorable to the use of epidural anesthesia on them.
| Advantages and disadvantages of the use of epidural, during a birth |
Advantages: |
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Disadvantages (for the expectant mother): |
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