Spinal anaesthesia is administered by
injecting small amounts of local anaesthetic into the cerebrospinal fluid (CSF). The injection is usually made in the lumbar spine below the level at which the spinal cord ends (L2).
Epidural anaesthesia is given in the epidural space of the spine which is just outside the dura. It can be given in a single shot or continuous with an indwelling catheter.
Spinal, epidural together with caudal anaesthesia are called central neuraxial block. The first spinal Anaesthesia was administered by Bier in 1898 using cocaine.
Initially epidural was given by the caudal route popularly known as caudal block and by 1930 lumbar epidural was introduced.
The advantages of epidural block over spinal block are
1) Avoidance of dural puncture
2) Surgical time is not a restriction as “top up” doses can be given
3) Excellent post operative pain relief.
Another excellent technique is combined SA/EA. The epidural is the standard 16 or 18 G and the spinal needle is 27 G.
Mechanism of Action
The injected local anaesthetic solution blocks conduction of impulses along all nerves with which it comes in contact. Motor, sensory and autonomic nerves are all blocked. SA/EA are useful methods of anaesthesia for all surgeries below the level of umbilicus
Children : It is generally avoided until full height gain. However it is documented to have been used safely.1
Technique of Spinal and Epidural Anaesthesia
Adequate knowledge of the relevant anatomy is necessary for performing a good block and avoiding complications (Fig 1).
A Needle is introduced in the back in either sitting or lying down position. The direction of needle at the start is also very important in getting the dural puncture or location of epidural space accurately. Epidural requires more skill, experience and precision and the aim is to avoid dural puncture at all costs.
Sitting makes the procedure technically easier. A good position is all important
Needles are available from size 16 to 29. Commonly used are 22 to 25 needle. The finer the needle lesser are the chances of post spinal headache.2
Drugs-local Anaesthetics
Indian Scenerio
Bupivacaine commonly known to us as sensorcain.
Lignocaine
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Commonly Used But Not Available In India
Cinchocaine
Amethocaine also known as tetracain
Mepivacaine
Preoperative Visit
Patients should be told about their anaesthetic during the pre-operative visit. It is important to explain the relevant details to the patient and address their concerns honestly and scientifically Fears about –an injection in the back-should be addressed. They must be reassured that, if they feel pain they will be given a general anaesthetic unless there is a significant medical contraindication for GA. A premedication should be prescribed at the visit.
Basic Precautions and Safety Measures
1) A good reliable IV line
2) IV fluid preloading
3) Basic resuscitation drugs particularly vasopressors available in the operating room.
4) Adequate haemodynamic monitoring i.e. pulse, ECG, blood pressure and pulse oximetry.
5) Steady supply of oxygen.
Post Spinal Headache
It is a low pressure headache caused by leakage of CSF from dural hole. It begins within 12-24 hours and may last a week or more. It is postural, being made worse by raising the head and relieved by lying down.
Prevention of Post Spinal Headache
1) Smaller size needle- 25 to 27 G. (25 G freely available in India)
2) Good intravenous and oral hydration
3) Avoidance of eye strain such as reading newspaper for 2 days
4) Maintain lying down and head low positon (nowadays debatable)
Treatment of Post Spinal Headache
1) Bed rest
2) Good hydration
3) Reassurance and a visit by the anaesthesiologist
4) Analgesics such as paracetamol, aspirin, NSAIDs and anti emetics..
5) Oral caffeine 300 mg 3 to 4 times per day3
6) Theophylline4
7) Sumatriptan5
8) Abdominal binder
9) Epidural fluids and epidural blood patch6
10) Epidural fibrin glue
Conclusion
Spinal and epidural anaesthesia are excellent anaesthesia techniques when used for the right indications. Complications is very low and preventable with good aseptic technique reasonable experience and a careful and judicious working attitude. It is a good idea for the patient, surgeon and referring doctor to be aware of the pros and cons of these techniques and helps to make choice of anaesthesia technique in the best interest of the patient.
References
1. Kokki H, Tuovinen K, Hendolin H. Spinal anaesthesia for paediatric day-case surgery: a double-blind, randomized, parallel group, prospective comparison of isobaric and hyperbaric bupivacaine. British J Anaesthesia 1998; 81 (4) : 502-06.
2. Tourtellotte WW. A randomized double-blind clinical trial comparing the 22 versus 26 gauge needle in the production of post-lumbar puncture syndrome in normal individuals. Headache 1972; 12 :73.
3. Camann WR, Murray RS, Mushlin PS, Lambert DH. Effects of oral caffeine on postdural puncture headache. A double-blind, placebo-controlled trial. Anesth Analg 1990; 70 : 181.
4. Schwalbe SS, Schiffmiller MW, Marx GF. Theophylline for post-dural puncture headache (abstract). Anesthesiology 1991; 75 : A1082.
5. Carp H, Singh PJ, Vadhera R, Jayaram A. Effects of the serotonin receptor agonist sumatriptan on postdural puncture headache: report of six cases. Anesth Analg 1994; 79 : 180-2.
6. Crawford JS. Experiences with epidural blood patch. Anaesthesia 1980; 35 : 51.
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