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Spinal Needle - The Key Tool Used to Deliver Anaesthesia for Lumbar Puncture
Spinal Needle - The Key Tool Used to Deliver Anaesthesia for Lumbar Puncture
The spinal needle is the key tool used to deliver anaesthesia for lumbar puncture (also known as a'spinal tap'). It is inserted into the back just above the hip bone. The anaesthetist may ask you to sit up or lie on your side during the procedure. The needle is inserted into the sac that contains cerebrospinal fluid, which surrounds the spinal cord. The fluid is a clear liquid that bathes the nerves in your lower spine. It helps to cushion the spinal cord and is a source of pain-killing chemicals called neurotransmitters. The spinal needle can cause a headache but this is usually mild and short-lived. The needle might feel uncomfortable when it goes in, and there could be a small amount of bleeding from the skin site, but this is not very common.
There are several different ways that a lumbar puncture can be performed, but the most common is to have you sit on an exam table and lean forward with your head on a pillow while the doctor inserts a small needle into the skin. A special cream might be put on the skin before the needle is inserted, which will help to numb the area. In some cases, a spinal anaesthetic may be given through this needle to ease the pain of the test.
Spinal anaesthesia became widely accepted in Europe and America in the 1920s and 1930s. Gaston Labat, who had been one of the main proponents of this technique, adapted the design of his syringe to create a spinal needle with a closed tip. This needle was made from unbreakable nickel and had a short bevel with a lateral orifice that opened when seated. He believed that this design minimised trauma to the dura and allowed the needle to pass between fibres rather than through them.
In 1951, Whitacre published a paper describing a 'pencil point needle' to prevent post spinal headache. His needle was also a 20 gauge, but instead of having a solid tip it had a hollow cannula with an opening on the side, close to the solid end. He hoped that this would allow the needle to separate the longitudinal fibres of the dura and arachnoid, without damaging them.
Since then, various modifications have been made to the needle tip shape, including the development of the atraumatic and pencil-point tips in current use. Despite these improvements, PDPH and inadequate titration of the local anaesthetic are still concerns in many centres.
The latest innovation is to use a clear needle hub, as with the BD Whitacre and BD Quincke spinal needles, which makes it easier for anaesthetists to see the position of the spinal needle through the hub, ensuring that the needle is in the correct place for the injection.
In addition, an electronic system can monitor the CSF pressure at the spinal needle tip. This allows the anaesthetist to titrate the dose of local anaesthetic more precisely, minimising the risk of a hypotonic spinal.
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