Practical Problems

The spinal needle feels as if it is in the right position but no CSF appears. 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 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 are not sure whether you are in the midline, ask the patient on 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 paramedian approach to the dura. This is performed by inserting the spinal needle about 0.5-1cm 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 through it to pierce the dura. When using this technique inject some local anaesthetic into the muscle before inserting the spinal needle.

The patient complains of pain during needle insertion. This suggests that the spinal needle is passing through the muscle on either side of the ligaments. Redirect your needle away from the side of the pain to get back into the midline or inject some local anaesthetic.

The patient complains of pain during injection of the spinal solution. Stop injecting and change the position of the needle. 

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. 

Problems with the Block

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. 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". 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. 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 patient's knees. 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 of tingling in the arms or hands. Do not tilt the table "head up". (See later under Treatment of a total spinal).

Nausea or vomiting. This may occur with high spinal blocks that may be associated with hypotension. Check the blood pressure and treat accordingly (see later).

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

Monitoring

It is essential to monitor the respiration, pulse and blood pressure closely. The blood pressure can fall precipitously following induction of spinal anaesthesia, particularly in the elderly and those who have not been adequately preloaded with fluid.

Warning signs of falling blood pressure include pallor, sweating, nausea or feeling generally unwell. A moderate fall in systolic blood pressure to say 80-90mm Hg in a young, healthy patient or 100mmHg in an older patient is acceptable, provided the patient looks and feels well and is adequately oxygenated.

Bradycardia is quite common during spinal anaesthesia particularly if the surgeon is manipulating the bowel or uterus. If the patient feels well, and the blood pressure is maintained, then it is not necessary to give atropine. If, however, the heart rate drops below 50 beats per minute or there is hypotension, then atropine 300-600mcg should be given intravenously. If the heart rate does not increase try ephedrine (see below).

It is generally considered good practice for all patients undergoing surgery under spinal anaesthesia to be given supplemental oxygen by facemask at a rate of 2-4 litres/minute, especially if sedation has also been given. 

Treatment of Hypotension

Hypotension is due to vasodilation and a functional decrease in the effective circulating volume. The treatment is, therefore, to reverse the vasodilatation with vasoconstrictor drugs and increase the circulating volume by giving fluids. 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 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.

Increase the speed of the intravenous infusion to maximum until the blood pressure is restored to acceptable levels and, if the pulse is slow, give atropine intravenously. Vasoconstrictors should be given immediately if the hypotension is severe, and to patients not responding to fluid therapy. 

Vasopressors

Ephedrine is probably the vasopressor of choice. It causes peripheral blood vessels to constrict and raises the cardiac output by increasing the heart rate and the force of myocardial contraction. It is safe for use in pregnancy, as it does not reduce placental blood flow. Ephedrine is generally available in 25 or 30mg ampoules. It is best diluted to 10mls with saline and then given in increments of 1-2ml (2.5-6mg) titrated against the blood pressure. Its effect generally lasts about 10 minutes and it may need repeating. Alternatively, the ampoule may be added to a bag of intravenous fluid and the rate of infusion altered to maintain the desired blood pressure. It can also be given intramuscularly but its onset time is delayed although its duration is prolonged. Larger doses are necessary when it is given intramuscularly.

Methoxamine (Vasoxine). It is available in 20mg ampoules and must be diluted before injection. A suitable adult dose is 2mg intravenously or 5-20mg by intramuscular injection. It is a pure peripheral vasoconstrictor and reflex bradycardia, needing treatment with atropine can occur. It is particularly useful to treat hypotension during spinal anaesthesia when the patient has a tachycardia.

Phenylephrine. A pure peripheral vasoconstrictor which is available in 10mg ampoules; it must be diluted before use. Suitable adult doses for intravenous use are 100-500mcg repeated after 15 minutes if necessary, or 2-5mg intramuscularly. It lasts about 15 minutes. A reflex bradycardia may occur.

Metaraminol (Aramine). It is supplied in 10mg ampoules and should be diluted and used incrementally (1-5mg) as with ephedrine. Alternatively, it can be added to 500ml of fluid and titrated against the blood pressure. It has a slower onset time (at least 2 minutes after intravenous injection) but lasts longer (20-60 minutes).

Epinephrine/Adrenaline. Available as 1mg/ml (1:1,000) and 1mg/10ml (1:10,000) ampoules. Dilute 1ml of 1:1,000 adrenaline to at least 10ml with saline and give increments of 50mcg (0.5ml of 1:10,000) repeating as necessary. Monitor the effect of epinephrine/adrenaline closely - it is a very powerful drug but only lasts a few minutes. It may be used during spinal anaesthesia if hypotension does not respond to first line drugs listed above or when they are not available.

Norepinephrine/Noradrenaline (Levophed). A powerful vasoconstrictor available in 2mg ampoules which must be diluted in 1000ml of intravenous fluid before use. It is then given at an initial rate of 2-3ml/minute and thereafter titrated against the blood pressure. Control the infusion with the utmost care taking particular care that to avoid extravasation. 

(Continued ...)

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