It is assumed that the patient has been adequately prepared, has had the procedure fully explained, has reliable intravenous access, is in a comfortable position and that resuscitation equipment is immediately available.

1. Scrub and glove up carefully.

2. Check the equipment on the sterile trolley.

3. Draw up the local anaesthetic to be injected intrathecally into the 5ml syringe, from the ampoule opened by your assistant. Read the label. Draw up the exact amount you intend to use, ensuring that your needle does not touch the outside of the ampoule (which is unsterile).

4. Draw up the local anaesthetic to be used for skin infiltration into the 2ml syringe. Read the label.

5. Clean the patient's back with the swabs and antiseptic ensuring that unsterile skin is not touched by your gloves. Swab radially outwards from the proposed injection site. Discard the swab and repeat several times making sure that a sufficiently large area is cleaned. Allow the solution to dry on the skin.

6. Locate a suitable interspinous space. You may have to press hard to feel the spinous processes in an obese patient.

7. Raise an intradermal wheal of local anaesthetic with a disposable 25 gauge needle at the proposed puncture site.

8. Insert the introducer if using a 24-25 gauge needle. Ideally it should be advanced into the interspinous ligament but care should be exercised in thin patients that an inadvertent dural puncture does not occur.

9. Insert the spinal needle (through the introducer, if applicable). Ensure that the stylet is in place so that the tip of the needle does not become blocked by a tiny particle of tissue or clot. It is imperative that the needle is inserted and stays in the midline and that the bevel is directed laterally. It is angled slightly cephalad (towards the head) and slowly advanced. An increased resistance will be felt as the needle enters the ligamentum flavum, followed by a loss of resistance as the epidural space is entered. Another loss of resistance may be felt as the dura is pierced and CSF should flow from the needle when the stylet is removed. If bone is touched, the needle should be withdrawn a centimetre or so and then re-advanced in a slightly more cephalad direction again ensuring that it stays in the midline.

10. If a 25 gauge spinal needle is being used, be prepared to wait 20-30 seconds for CSF to appear after the stylet has been withdrawn. If no CSF appears, replace the stylet and advance the needle a little further and try again.

11. When CSF appears, take care not to alter the position of the spinal needle as the syringe of local anaesthetic is being attached. The needle is best immobilised by resting the back of the non-dominant hand firmly against the patient and by using the thumb and index finger to hold the hub of the needle. Be sure to attach the syringe firmly to the hub of the needle; hyperbaric solutions are viscous and resistance to injection will be high, especially through fine gauge needles. It is, therefore, easy to spill some of the local anaesthetic unless care is taken.

12. Aspirate gently to check the needle tip is still intrathecal and then slowly inject the local anaesthetic. When the injection is complete, withdraw the spinal needle, introducer and syringe as one and apply a sticking plaster to the puncture site.

 
Practical Problems.

Blood flows from the spinal needle. Wait a short time. If the blood becomes pinkish and finally clear, all is well. If blood only continues to drip, then it is likely that the needle tip is in an epidural vein and it should be advanced a little further or angled more medially to pierce the dura.

The patient complains of sharp, stabbing leg pain. The needle has hit a nerve root because it has deviated laterally. Withdraw the needle and redirect it more medially away from the affected side.

Wherever the needle is directed, it seems to strike bone. Make sure the patient is still properly positioned with as much lumbar flexion as possible and that the needle is still in the mid-line. If you think that you are not in the midline check with the patient which side they feel the needle. Alternatively, if the patient is elderly and cannot bend very much or has heavily calcified interspinous ligaments, it might be better to attempt a lateral approach to the dura.

This is performed by inserting the spinal needle about 1cm lateral to the mid line at the level of the upper border of a spinous process, then directing it both cephalad and medially. If bone is contacted it is likely to be the vertebral lamina. It should then be possible to "walk" the needle off the bone and into the epidural space, then advance through it to pierce the dura (fig. 6 ).

 
Assessing the Block.

Some patients are very poor at describing what they do or do not feel, therefore, objective signs are valuable. If, for example, the patient is unable to lift his legs from the bed, the block is at least up to the mid-lumbar region.

It is unnecessary to test sensation with a sharp needle and leave the patient with a series of bleeding puncture wounds. It is better to test for a loss of temperature sensation using a swab soaked in either ether or alcohol. Do this by first touching the patient with the damp swab on the chest or arm (where sensation is normal), so that they appreciate that the swab feels cold. Then work up from the legs and lower abdomen until the patient again appreciates that the swab feels cold.

If the replies are inconsistent or equivocal, the patient can be gently pinched with artery forceps or fingers on blocked and unblocked segments and asked if they feel pain. Using this method, there is rarely any difficulty in ascertaining the extent of the block.

Surgeons should be dissuaded from prodding the patient and asking "can you feel this?". Surgeons and patients should be reminded that when a block is successful, a patient may still be aware of touch but will not feel pain.

(Continued...)

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