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A Tuohy needle, or Tuohy epidural needle, is a long hollow needle with a curved tip used to administer anesthetic through an epidural, a type of anesthesia commonly preferred during labor and delivery. The curved tip of this type of hypodermic needle helps to prevent the dura layer of the spinal cord from being accidentally penetrated. An increase in the lumen diameter of this epidural needle helps the anesthesiologist to insert the needle precisely with a controlled force.
An epidural Tuohy needle has several special design features. The gauge of this needle is larger than other types of needles used in a medical setting. On two sides of the needle’s shaft are wing shaped protrusions that are used to exert additional force during the insertion of the Tuohy needle into the subarachnoid space of the spinal cord. Visible on the shaft of the needle are alternating colored bands that are spaced an equal distance apart from each other. These markings allow for the precise measurement of the length of the needle already inside the body.
Tuohy needles can be ordered through a medical supply warehouse or from an Internet website. Most Tuohy needles are sterilized and then individually packaged for a single use. Disposable Tuohy needles are made with a plastic hub and metal stylet, and some feature removable wings.
Before inserting the Tuohy needle into the patient, the anesthesiologist will carefully clean the insertion site. The patient will be instructed to lean forward and grasp her knees with both arms. When the patient is completely still, the anesthesiologist will carefully insert the needle into the space between the vertebrae of the spine.
After the anesthesiologist has inserted the Tuohy needle through the spinal ligaments, a thin flexible epidural catheter is threaded through the needle into the subarachnoid space. Once the presence of cerebrospinal fluid (CSF) dripping from the needle has confirmed the correct placement of the catheter, the needle will be removed. The epidural catheter is secured in position with a medical grade adhesive tape to reduce the risk of the catheter moving within the subarachnoid space. It is left in place until pain relief is no longer necessary for the patient’s comfort.
Most of the anesthetic properties of the medication will usually take effect within four minutes of the removal of the Tuohy needle from the patient's body. During the administration of the epidural anesthesia, the anesthesiologist will carefully monitor the patient’s pulse and respiration rate. The patient’s blood pressure and oxygen saturation levels will also observed throughout the epidural to ensure that an unsafe drop in either level is promptly treated.