Spinal anaesthesia | |
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Backflow of cerebrospinal fluid through a 25 gauge spinal needle after puncture of the arachnoid mater during initiation of spinal anaesthesia | |
MeSH | D000775 |
Spinal anaesthesia (or spinal anesthesia), also called spinal block, subarachnoid block, intradural block and intrathecal block, [1] is a form of neuraxial regional anaesthesia involving the injection of a local anaesthetic or opioid into the subarachnoid space, generally through a fine needle, usually 9 cm (3.5 in) long. It is a safe and effective form of anesthesia usually performed by anesthesiologists that can be used as an alternative to general anesthesia commonly in surgeries involving the lower extremities and surgeries below the umbilicus. The local anesthetic with or without an opioid injected into the cerebrospinal fluid provides locoregional anaesthesia: true anaesthesia, motor, sensory and autonomic (sympathetic) blockade. Administering analgesics (opioid, alpha2-adrenoreceptor agonist) in the cerebrospinal fluid without a local anaesthetic produces locoregional analgesia: markedly reduced pain sensation (incomplete analgesia), some autonomic blockade (parasympathetic plexi), but no sensory or motor block. Locoregional analgesia, due to mainly the absence of motor and sympathetic block may be preferred over locoregional anaesthesia in some postoperative care settings. The tip of the spinal needle has a point or small bevel. Recently, pencil point needles have been made available (Whitacre, Sprotte, Gertie Marx and others). [2]
Spinal anaesthesia is a commonly used technique, either on its own or in combination with sedation or general anaesthesia. It is most commonly used for surgeries below the umbilicus, however recently its uses have extended to some surgeries above the umbilicus as well as for postoperative analgesia. Procedures which use spinal anesthesia include:[ citation needed ]
Spinal anaesthesia is the technique of choice for Caesarean section as it avoids a general anaesthetic and the risk of failed intubation (which is probably a lot lower than the widely quoted 1 in 250 in pregnant women [3] ). It also means the mother is conscious and the partner is able to be present at the birth of the child. The post operative analgesia from intrathecal opioids in addition to non-steroidal anti-inflammatory drugs is also good.
Spinal anesthesia may be favored when the surgical site is amenable to spinal blockade for patients with severe respiratory disease such as COPD as it avoids the potential respiratory consequences of intubation and ventilation. It may also be useful in patients where anatomical abnormalities may make tracheal intubation relatively difficult.
In pediatric patients, spinal anesthesia is particularly useful in children with difficult airways and those who are poor candidates for endotracheal anesthesia such as increased respiratory risks or presence of full stomach. [4]
This can also be used to effectively treat and prevent pain following surgery, particularly thoracic, abdominal pelvic, and lower extremity orthopedic procedures. [5]
Prior to receiving spinal anesthesia, it is important to provide a thorough medical evaluation to ensure there are no absolute contraindications and to minimize risks and complications. Although contraindications are rare, below are some of them: [4] [5]
Relative Contraindication
Complications of spinal anesthesia can result from the physiologic effects on the nervous system and can also be related to placement technique. Most of the common side effects are minor and are self-resolving or easily treatable while major complications can result in more serious and permanent neurological damage and rarely death. These symptoms can occur immediately after administration of the anesthetic or be delayed. [7]
Common and minor complications include: [5]
Serious and permanent complications are rare but are usually related to physiologic effects on the cardiovascular system and neurological system or when the injection has been unintentionally at the wrong site. [5] The following are some major complications:
Regardless of the anaesthetic agent (drug) used, the desired effect is to block the transmission of afferent nerve signals from peripheral nociceptors. Sensory signals from the site are blocked, thereby eliminating pain. The degree of neuronal blockade depends on the amount and concentration of local anaesthetic used and the properties of the axon. Thin unmyelinated C-fibres associated with pain are blocked first, while thick, heavily myelinated A-alpha motor neurons are blocked moderately. Heavily myelinated, small preganglionic sympathetic fibers are blocked last. The desired result is total numbness of the area. A pressure sensation is permissible and often occurs due to incomplete blockade of the thicker A-beta mechanoreceptors. This allows surgical procedures to be performed with no painful sensation to the person undergoing the procedure.[ citation needed ]
Some sedation is sometimes provided to help the patient relax and pass the time during the procedure, but with a successful spinal anaesthetic the surgery can be performed with the patient wide awake.
In spinal anesthesia, the needle is placed past the dura mater in subarachnoid space and between lumbar vertebrae. In order to reach this space, the needle must pierce through several layers of tissue and ligaments which include the supraspinous ligament, interspinous ligament, and ligamentum flavum. Because the spinal cord (conus medullaris) is typically at the L1 or L2 level of the spine, the needle should be inserted below this between L3 and L4 space or L4 and L5 space in order to avoid injury to the spinal cord.
Patient positioning is essential to the success of the procedure and can affect how the anesthetic spreads following administration. There are three different positions which are used: sitting, lateral decubitus, and prone. The sitting and lateral decubitus positions are the most common.
Sitting – The patient sits upright at the edge of the exam table with their back facing the provider and their legs hanging off the end of the table and feet resting on a stool. Patients should roll their shoulders and upper back forward.
Lateral decubitus – In this position, the patient lies on their side with their back at the edge of the bed and facing the provider. The patient should curl their shoulder and legs and arch out their lower back.
Prone – The patient is positioned face down and their back facing upwards in a jackknife position.
Spinal anaesthetics are typically limited to procedures involving most structures below the upper abdomen. To administer a spinal anaesthetic to higher levels may affect the ability to breathe by paralysing the intercostal respiratory muscles, or even the diaphragm in extreme cases (called a "high spinal", or a "total spinal", with which consciousness is lost), as well as the body's ability to control the heart rate via the cardiac accelerator fibres. Also, injection of spinal anaesthesia higher than the level of L1 can cause damage to the spinal cord, and is therefore usually not done.
Epidural anaesthesia is a technique whereby a local anaesthetic drug is injected through a catheter placed into the epidural space. This technique is similar to spinal anaesthesia as both are neuraxial, and the two techniques may be easily confused with each other. Differences include:
Bupivacaine (Marcaine) is the local anaesthetic most commonly used, although lidocaine (lignocaine), tetracaine, procaine, ropivacaine, levobupivicaine, prilocaine, or cinchocaine may also be used. Commonly opioids are added to improve the block and provide post-operative pain relief, examples include morphine, fentanyl, diamorphine, and buprenorphine. Non-opioids like clonidine or epinephrine may also be added to prolong the duration of analgesia (although Clonidine may cause hypotension). In the United Kingdom, since 2004 the National Institute for Health and Care Excellence recommends that spinal anaesthesia for Caesarean section is supplemented with intrathecal diamorphine and this combination is now the modal form of anaesthesia for this indication in that country. In the United States, morphine is used for cesareans for the same purpose since diamorphine (heroin) is not used in clinical practice in the US.
Baricity refers to the density of a substance compared to the density of human cerebrospinal fluid. Baricity is used in anaesthesia to determine the manner in which a particular drug will spread in the intrathecal space. Usually, the hyperbaric, (for example, hyperbaric bupivacaine) is chosen, as its spread can be effectively and predictably controlled by the Anaesthesiologist, by tilting the patient. Hyperbaric solutions are made more dense by adding glucose to the mixture.
Baricity is one factor that determines the spread of a spinal anaesthetic but the effect of adding a solute to a solvent, i.e. solvation or dissolution, also has an effect on the spread of the spinal anaesthetic. In tetracaine spinal anaesthesia, it was discovered that the rate of onset of analgesia was faster and the maximum level of analgesia was higher with a 10% glucose solution than with a 5% glucose spinal anaesthetic solution. Also, the amount of ephedrine required was less in the patients who received the 5% glucose solution. [11] In another study this time with 0.5% bupivacaine the mean maximum extent of sensory block was significantly higher with 8% glucose (T3.6) than with 0.83% glucose (T7.2) or 0.33% glucose (T9.5). Also the rate of onset of sensory block to T12 was fastest with solutions containing 8% glucose. [12]
The first spinal analgesia was administered in 1885 by James Leonard Corning (1855–1923), a neurologist in New York. [13] He was experimenting with cocaine on the spinal nerves of a dog when he accidentally pierced the dura mater.
The first planned spinal anaesthesia for surgery on a human was administered by August Bier (1861–1949) on 16 August 1898, in Kiel, when he injected 3 ml of 0.5% cocaine solution into a 34-year-old labourer. [14] After using it on six patients, he and his assistant each injected cocaine into the other's spine. They recommended it for surgeries of legs, but gave it up due to the toxicity of cocaine.
Anesthesia or anaesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia, paralysis, amnesia, and unconsciousness. An individual under the effects of anesthetic drugs is referred to as being anesthetized.
A local anesthetic (LA) is a medication that causes absence of all sensation in a specific body part without loss of consciousness, providing local anesthesia, as opposed to a general anesthetic, which eliminates all sensation in the entire body and causes unconsciousness. Local anesthetics are most commonly used to eliminate pain during or after surgery. When it is used on specific nerve pathways, paralysis also can be induced.
Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is to help diagnose diseases of the central nervous system, including the brain and spine. Examples of these conditions include meningitis and subarachnoid hemorrhage. It may also be used therapeutically in some conditions. Increased intracranial pressure is a contraindication, due to risk of brain matter being compressed and pushed toward the spine. Sometimes, lumbar puncture cannot be performed safely. It is regarded as a safe procedure, but post-dural-puncture headache is a common side effect if a small atraumatic needle is not used.
General anaesthesia (UK) or general anesthesia (US) is a method of medically inducing loss of consciousness that renders a patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general anaesthetic medications, which often act in combination with an analgesic and neuromuscular blocking agent. Spontaneous ventilation is often inadequate during the procedure and intervention is often necessary to protect the airway. General anaesthesia is generally performed in an operating theater to allow surgical procedures that would otherwise be intolerably painful for a patient, or in an intensive care unit or emergency department to facilitate endotracheal intubation and mechanical ventilation in critically ill patients. Depending on the procedure, general anaesthesia may be optional or required. Regardless of whether a patient may prefer to be unconscious or not, certain pain stimuli could result in involuntary responses from the patient that may make an operation extremely difficult. Thus, for many procedures, general anaesthesia is required from a practical perspective.
Combined spinal and epidural anaesthesia is a regional anaesthetic technique, which combines the benefits of both spinal anaesthesia and epidural anaesthesia and analgesia. The spinal component gives a rapid onset of a predictable block. The indwelling epidural catheter gives the ability to provide long lasting analgesia and to titrate the dose given to the desired effect.
An anesthetic or anaesthetic is a drug used to induce anesthesia — in other words, to result in a temporary loss of sensation or awareness. They may be divided into two broad classes: general anesthetics, which result in a reversible loss of consciousness, and local anesthetics, which cause a reversible loss of sensation for a limited region of the body without necessarily affecting consciousness.
Epidural administration is a method of medication administration in which a medicine is injected into the epidural space around the spinal cord. The epidural route is used by physicians and nurse anesthetists to administer local anesthetic agents, analgesics, diagnostic medicines such as radiocontrast agents, and other medicines such as glucocorticoids. Epidural administration involves the placement of a catheter into the epidural space, which may remain in place for the duration of the treatment. The technique of intentional epidural administration of medication was first described in 1921 by Spanish military surgeon Fidel Pagés.
Intrathecal administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF). It is useful in several applications, such as for spinal anesthesia, chemotherapy, or pain management. This route is also used to introduce drugs that fight certain infections, particularly post-neurosurgical. Typically, the drug is given this way to avoid being stopped by the blood–brain barrier, as it may not be able to pass into the brain when given orally. Drugs given by the intrathecal route often have to be compounded specially by a pharmacist or technician because they cannot contain any preservative or other potentially harmful inactive ingredients that are sometimes found in standard injectable drug preparations.
Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease sensation in a specific small area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural space. It is available mixed with a small amount of epinephrine to increase the duration of its action. It typically begins working within 15 minutes and lasts for 2 to 8 hours.
Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block is a short-term block, usually lasting hours or days, involving the injection of an anesthetic, a corticosteroid, and other agents onto or near a nerve. Neurolytic block, the deliberate temporary degeneration of nerve fibers through the application of chemicals, heat, or freezing, produces a block that may persist for weeks, months, or indefinitely. Neurectomy, the cutting through or removal of a nerve or a section of a nerve, usually produces a permanent block. Because neurectomy of a sensory nerve is often followed, months later, by the emergence of new, more intense pain, sensory nerve neurectomy is rarely performed.
Chloroprocaine is a local anesthetic given by injection during surgical procedures and labor and delivery. Chloroprocaine vasodilates; this is in contrast to cocaine which vasoconstricts. Chloroprocaine is an ester anesthetic.
Levobupivacaine (rINN) is a local anaesthetic drug indicated for minor and major surgical anaesthesia and pain management. It is a long-acting amide-type local anaesthetic that blocks nerve impulses by inhibiting sodium ion influx into the nerve cells. Levobupivacaine is the S-enantiomer of racemic bupivacaine and therefore similar in pharmacological effects. The drug typically starts taking effect within 15 minutes and can last up to 16 hours depending on factors such as site of administration and dosage.
Veterinary anesthesia is a specialization in the veterinary medicine field dedicated to the proper administration of anesthetic agents to non-human animals to control their consciousness during procedures. A veterinarian or a Registered Veterinary Technician administers these drugs to minimize stress, destructive behavior, and the threat of injury to both the patient and the doctor. The duration of the anesthesia process goes from the time before an animal leaves for the visit to the time after the animal reaches home after the visit, meaning it includes care from both the owner and the veterinary staff. Generally, anesthesia is used for a wider range of circumstances in animals than in people not only due to their inability to cooperate with certain diagnostic or therapeutic procedures, but also due to their species, breed, size, and corresponding anatomy. Veterinary anesthesia includes anesthesia of the major species: dogs, cats, horses, cattle, sheep, goats, and pigs, as well as all other animals requiring veterinary care such as birds, pocket pets, and wildlife.
Post-dural-puncture headache (PDPH) is a complication of puncture of the dura mater. The headache is severe and described as "searing and spreading like hot metal", involving the back and front of the head and spreading to the neck and shoulders, sometimes involving neck stiffness. It is exacerbated by movement and sitting or standing and is relieved to some degree by lying down. Nausea, vomiting, pain in arms and legs, hearing loss, tinnitus, vertigo, dizziness and paraesthesia of the scalp are also common.
An epidural blood patch (EBP) is a surgical procedure that uses autologous blood, meaning the patient's own blood, in order to close one or many holes in the dura mater of the spinal cord, which occurred as a complication of a lumbar puncture or epidural placement. The punctured dura causes cerebrospinal fluid leak. The procedure can be used to relieve orthostatic headaches, most commonly post dural puncture headache (PDPH).
Brachial plexus block is a regional anesthesia technique that is sometimes employed as an alternative or as an adjunct to general anesthesia for surgery of the upper extremity. This technique involves the injection of local anesthetic agents in close proximity to the brachial plexus, temporarily blocking the sensation and ability to move the upper extremity. The subject can remain awake during the ensuing surgical procedure, or they can be sedated or even fully anesthetized if necessary.
Interventional pain management or interventional pain medicine is a medical subspecialty defined by the National Uniforms Claims Committee (NUCC) as, " invasive interventions such as the discipline of medicine devoted to the diagnosis and treatment of pain related disorders principally with the application of interventional techniques in managing sub acute, chronic, persistent, and intractable pain, independently or in conjunction with other modalities of treatment". Medicare Payment Advisory Commission (MedPAC) defined interventional techniques as, "minimally invasive procedures including, percutaneous precision needle placement, with placement of drugs in targeted areas or ablation of targeted nerves; and some surgical techniques such as laser or endoscopic diskectomy, intrathecal infusion pumps and spinal cord stimulators, for the diagnosis and management of chronic, persistent or intractable pain". Minimally invasive interventions such as facet joint injections, nerve blocks, neuroaugmentation, vertebroplasty, kyphoplasty, nucleoplasty, endoscopic discectomy, and implantable drug delivery systems are utilized in managing subacute or chronic pain.
The history of neuraxial anaesthesia dates back to the late 1800s and is closely intertwined with the development of anaesthesia in general. Neuraxial anaesthesia, in particular, is a form of regional analgesia placed in or around the Central Nervous System, used for pain management and anaesthesia for certain surgeries and procedures.
Caudal anaesthesia is a form of neuraxial regional anaesthesia conducted by accessing the epidural space via the sacral hiatus. It is typically used in paediatrics to provide peri- and post-operative analgesia for surgeries below the umbilicus. In adults, it can be used in the context of anorectal surgery or for chronic low back pain management.