Spinal anaesthesia, also called spinal analgesia[citation needed] or sub-arachnoid block (SAB), is a form of regional anaesthesia involving injection of a local anaesthetic into the Subarachnoid space, generally through a fine needle, usually 3.5 inches (9 cm) long. For extremely obese patients, some anaesthesiologists prefer spinal needles which are seven inches (18 cm) long. The tip of the spinal needle has a point or small bevel. Recently pencil point needles have been made available (Whitacre, Sprotte, & others).
There are hyperbaric, isobaric and hypobaric solutions of anaesthetics to choose for the spinal anaesthesia. Usually, the hyperbaric is chosen, as its spread can be effectively and predictably controlled by the anaesthesiologist, by tilting the patient.
Bupivacaine is the local anaesthetic most commonly used, although lignocaine (lidocaine), tetracaine, procaine, ropivacaine, levobupivicaine and cinchocaine are also available. Sometimes a vasoconstrictor such as epinephrine is added to the local anaesthetic to prolong its duration. Of late, many anaesthesiologists are preferring to add opioids like fentanyl or buprenorphine, or non-opioids like clonidine, to the local anaesthetic used in spinal, to give a smoother 'effect' and to provide prolonged pain relief once the action of the 'spinal' has worn off.
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 unmylenated C-fibres associated with pain are blocked first, while thick, heavily mylenated A-alpha motor neurons 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 mechnorecptors. This allows surgical procedures to be performed with no painful sensation to the person undergoing the procedure.
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. Spinal anaesthetics are 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.
Baricity refers to the density of a substance compared to the density of human cerebral spinal fluid. Baricity is used in anaesthesia to determine the manner in which a particular drug will spread in the intrathecal space. Hyperbaric solutions (for example, hyperbaric bupivacaine) are made heavy by adding dextrose to the mixture.
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History
The first spinal analgesia was administered in 1885 by Leonard Corning (1855-1923), a neurologist in New York.[1] 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 in man 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.[2] After using it on 6 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.
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Present status
Current usage of this technique is waning in the developed world, with epidural analgesia or combined spinal-epidural anaesthesia emerging as the techniques of choice where the cost of the disposable 'kit' is not an issue.
However spinal analgesia is the mainstay of anaesthesia in countries like India and parts of Africa, excluding the major centres. Thousands of spinal anaesthetics are administered daily in hospitals and nursing homes. At a low cost, a surgery of up to two hours duration can be performed.
- Indications: This technique is very useful in patients having an irritable airway (bronchial asthma or allergic bronchitis), anatomical abnormalities which make endotracheal intubation very difficult (micrognathia), borderline hypertensives where administration of general anaesthesia or endotracheal intubation can further elevate the blood pressure, procedures in geriatric patients. It is the technique of choice for diabetic patients.
- Contraindications: Non-availability of patient's consent, local infection or sepsis at the site of lumbar puncture, bleeding disorders, space occupying lesions of the brain, disorders of the spine and maternal hypotension.
Operations
All surgical interventions below the umbilicus, is the general guiding principle:
- Abdominal & vaginal hysterectomies
- Laparoscopy Assisted Vaginal Hysterectomies (LAVH) combined with general anaesthesia
- Caesarean sections
- Hernia (inguinal or epigastric)
- Piles fistulae & fissures
- orthopaedic surgeries on the pelvis, femur, tibia and the ankle
- nephrectomy
- cholecystectomies
- trauma surgery on the lower limbs, especially if the patient is full-stomach
- Open tubectomies
- Trans-urethral resection of prostate
Complications
Can be broadly classified as immediate (on the operating table) or late (in the ward or in the P.A.C.U. post-anaesthesia care unit):
- Spinal shock.
- Cauda equina injury.
- Cardiac arrest.
- Hypothermia.
- Broken needle.
- Bleeding resulting in haematoma, with or without subsequent neurological sequelae due to compression of the spinal nerves
- Infection: immediate within six hours of the spinal anaesthetic manifesting as meningism or meningitis or late, at the site of injection, in the form of pus discharge, due to improper sterilization of the LP set.
- PDPH:post dural puncture head ache or post spinal head ache
See also
- Epidural
- Lumbar puncture
- Combined spinal and epidural anaesthesia
- Transparent reality simulation of spinal anesthesia
References
- ^ 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)
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