SPINAL ANAESTHESIA – A Practical Tips

The spinal needle feels as if it is in the right position but no CSF flows. Wait at least 30 seconds, then try rotating the needle 90 degrees and wait again. If there is still no CSF, attach an empty 2ml syringe and inject 0.5-1ml of air to ensure the needle is not blocked then use the syringe to aspirate whilst slowly withdrawing the spinal needle. Stop as soon as CSF appears in the sy­ringe.

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 bebetter 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.

No apparent block at all. If after 10 minutes the patient still has full power in the legs and normal sensation, then the block has failed probably because the injection was not intrathecal. Try again.

The block is one-sided or is not high enough on one side.

a). When using a hyperbaric solution, lie the patient on the side that is inadequately blocked for a few minutes and adjust the table so that the patient is slightly “head down”.

b). When using an isobaric solution, lie the patient on the side that is blocked. (Moving a patient around in any way at all in the first 10-20 minutes following injection will tend to increase the height of the block)

Block not high enough.

a). When using a hyperbaric solution, tilt the patient head down whilst they are supine (lying on the back), so that the solution can run up the lumbar curvature. Flatten the lumbar curvature by raising the patients knees.

b). When using a plain solution turn the patient a complete circle from supine to prone (lying on the front) and back to supine again.

Block too high. The patient may complain of difficulty in breathing or tingling in the arms or hands. Do not tilt the table “head up”.

Nausea or vomiting. This may occur with high spinal blocks which may be associated with hypotension. Check the blood pressure and treat accordingly.

Shivering. This occurs occasionally. Reassure the patient and give oxygen by mask.

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.

The site to be operated on should not be repeatedly touched and the patient asked “Can you feel this?” as this increases the patient’s anxiety. 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.

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.

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

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.

Treatment of Hypotension

All hypotensive patients should be given OXYGEN by mask until the blood pressure is re­stored. A simple and effective way of rapidly increasing the patient’s circulating volume is by raising their legs thus increasing the return of venous blood to the heart. This can either be done manually by an assistant or by tilting the lower half of the operating table. Tilting the whole operating table head down will also achieve the same effect, but is unwise if a hyperbaric spinal anaesthetic has been injected in the preceding 15 minutes as it will result in the block spreading higher and the hypotension becoming more severe. If an isobaric spinal solution has been used, tilting the table at any time will have very little effect on the height of the block.

Numbness or weakness of the arms and hands, indicating that the block has reached the cervico[1]thoracic junction.

Difficulty breathing – as the intercostal nerves are blocked the patient may state that they can’t take a deep breath. As the phrenic nerves (C 3,4,5) which supply the diaphragm become blocked, the patient will initially be unable to talk louder than a whisper and will then stop breathing.

Loss of consciousness.

Action:

Ask for help – several pairs of hands may be useful!

Intubate and ventilate the patient with 100% oxygen.

Treat hypotension and bradycardia with intravenous fluids, atropine and vasopressors.

Source: Update in Anaesthesia. Dr Chris Ankcorn & Dr William F Casey.