Spinal anaesthesia
Spinal anaesthesia | |
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MeSH | D000775 |
Spinal anaesthesia (or spinal anesthesia), also called spinal block, subarachnoid block, intradural block and intrathecal block,
Indications
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]
- Orthopaedic surgery on the pelvis, hip, femur, knee, tibia, and ankle, including arthroplasty and joint replacement
- Vascular surgery on the legs
- Endovascular aortic aneurysm repair
- Hernia (inguinal or epigastric)
- Haemorrhoidectomy
- Nephrectomy and cystectomy in combination with general anaesthesia
- Transurethral resection of the prostate and transurethral resection of bladder tumours
- Hysterectomy in different techniques used
- Caesarean sections
- Pain management during vaginal birth and delivery
- Urology cases
- Examinations under anaesthesia
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]
Contraindications
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]
- Patient refusal
- Local infection or sepsis at the site of injection
- Bleeding disorders, thrombocytopaenia, or systemic anticoagulation (secondary to an increased risk of a spinal epidural hematoma)
- Severe aortic stenosis
- Increased intracranial pressure
- Space occupying lesions of the brain
- Anatomical disorders of the spine such as scoliosis (although where pulmonary function is also impaired, spinal anaesthesia may be favored)[6]
- Hypovolaemia e.g. following massive haemorrhage, including in obstetric patients
- Allergy
Relative Contraindication
- Ehlers–Danlos syndrome, or other disorders causing resistance to local anesthesia
Risks and complications
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]
- Mild hypotension
- Bradycardia
- Nausea and vomiting[8]
- Transient neurological symptoms (lower back pain with pain in the legs) [9]
- spinal needle to lower the risk of PDPH – specifically, the Braun Atraucan 26G needle.[10]
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:
- Nerve injuries: Cauda equina syndrome, radiculopathy
- Cardiac arrest
- Severe hypotension
- sequelaedue to compression of the spinal nerves.
- Epidural abscess
- Infection (e.g. meningitis)
Technique
Regardless of the
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.
Anatomy
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.
Positioning
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.
Limitations
Spinal anaesthetics are typically limited to procedures involving most structures below the upper
Differences with epidural anaesthesia
- A spinal anaesthetic delivers drug to the subarachnoid space and into the cerebrospinal fluid (CSF), allowing it to act on the spinal cord directly. An epidural delivers drugs outside the dura (outside CSF), and has its main effect on nerve roots leaving the dura at the level of the epidural, rather than on the spinal cord itself.
- A spinal gives profound block of all motor and sensory function below the level of injection, whereas an epidural blocks a 'band' of nerve roots around the site of injection, with normal function above, and close-to-normal function below the levels blocked.
- The injected dose for an epidural is larger, being about 10–20 mL compared to 1.5–3.5 mL in a spinal.
- In an epidural, an indwelling catheter may be placed that allows for redosing injections, while a spinal is almost always a one-shot only. Therefore, spinal anaesthesia is more often used for shorter procedures relative to procedures which require epidural anaesthesia.
- The onset of analgesia is approximately 25–30 minutes in an epidural, while it is approximately 5 minutes in a spinal.
- An epidural often does not cause as significant a neuromuscular blockas a spinal, unless specific local anaesthetics are also used which block motor fibres as readily as sensory nerve fibres.
- An epidural may be given at a L2to avoid piercing the spinal cord.
Injected substances
History
The first spinal analgesia was administered in 1885 by
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.
See also
References
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- ^ Effect of Glucose Concentration on the Intrathecal Spread of 0.5% Bupivacaine
- ^ Corning J. L. N.Y. Med. J. 1885, 42, 483 (reprinted in 'Classical File', Survey of Anesthesiology 1960, 4, 332)
- ^ Bier A. Versuche über Cocainisirung des Rückenmarkes. Deutsch Zeitschrift für Chirurgie 1899;51:361. (translated and reprinted in 'Classical File', Survey of Anesthesiology 1962, 6, 352)