Elderly patients, those above the age of 60 years are the ideal candidates for continuous spinal anesthesia when undergoing pelvic or lower extremity surgery. Hip or knee replacement surgery, lower extremity trauma or vascular surgery are excellent examples of where continuous spinal anesthesia can be the best choice for anesthetic management. The older the patient, the greater the benefits. What are the benefits? First, the spinal anesthetic will relieve the pain of the injury and/or surgery, and will provide excellent muscle relaxation for the surgeon. Second, the continuous technique will provide anesthesia for whatever duration of surgery is required. The anesthesia provider does not have to guess the likely duration of the operation as he/she would with a single-shot technique. Third, the total quantity of local anesthetic drug injected is much smaller than with a single-shot technique, because the amount of drug injected can be titrated to reach just above the analgesic level required for the operation. Fourth, because of the limited extent of the spinal level compared to a single-shot spinal, the likelihood of extensive sympathetic blockade and hypotension or other complications from a higher level is much less. Finally, the amount of analgesic or sedative-hypnotic drugs that need to be administered during the operation is usually none or minimal. If the patient has been in pain, such as from a fractured hip, once the pain is relieved with a continuous spinal the patient will usually sleep throughout the operation.

The biggest drawback to doing a continuous spinal block is getting the patient into a position that permits performing the block. The ideal position is having the patient lie lateral with the operative side down or dependent with the legs and head flexed toward the abdomen. This may be a formidable task in patients who are in pain from a fracture or trauma, and may necessitate administration of a low dose of a short acting analgesic such as fentanyl or alfentanil to lessen the pain. Once the patient is in position, the remainder of the procedure is relatively easy.

The next step is identifying the ideal interspace, which is usually L_2–3 or L_3–4. A standard adult epidural catheter set is opened for use. Once the anesthesia provider has been appropriately dressed and gloved and the back sterilely prepped and draped, local anesthesia is generously injected at the selected interspace. The anesthesia provider then inserts a 19 g epidural needle (e.g. Huber-tipped, Tuohy needle) into the interspace at a slightly cephalad angle. Because of bony spurs or ossification, the provider may have to redirect the needle several times or even go to another interspace. Once cerebrospinal fluid is obtained, it is important to inject a small amount of rapidly-acting local anesthetic before inserting the 20 g epidural catheter. The local anesthetic will prevent the patient from jumping or complaining should the catheter touch a nerve as it is being advanced. The catheter should only be advanced a few centimeters beyond the needle tip, and observed to drip CSF before removing the needle. If the catheter does not advance easily, it is advisable to insert the needle in another millimeter to insure that the bevel is fully in the subarachnoid space. Also, rotating the needle slightly to one side or the other may facilitate insertion of the catheter. Once the catheter is firmly secured and bandaged, the patient returned to the position required for the operation. Usually the dose of local anesthetic given to insert the catheter is sufficient to provide pain relief for the surgical positioning.