In the recent years, the popularity of the combined spinal-epidural anesthesia (CSEA) has increased considerably. This technique involves the placement of a catheter in the epidural space, along with the injection of a drug in the spinal fluid within the subarachnoid space. It is believed that this technique reduces the rate of anesthetic failure, when compared to the cases wherein spinal or epidural block is used alone.
The administration of an anesthetic agent is an integral part of medical procedures, especially the ones involving a surgery. An anesthetic agent is a drug or a numbing agent that brings about a temporary loss of bodily sensation. Anesthesia is mainly classified into general, regional, and local anesthesia. General anesthesia induces a loss of consciousness, which is why it is suggested for extensive surgical procedures. However, it can sometimes give rise to certain complications. Regional anesthesia involves blocking sensation in a particular region of body. Though it doesn't cause loss of consciousness, it could be combined with sedation in some cases. Spinal blocks and epidural are a form of regional anesthesia that might be recommended for surgeries of the lower abdominal region, pelvis, or the lower extremities.
Though both spinal block and epidural induce a loss of bodily sensation, there are certain differences between the two. The major differences between spinal and epidural block lie in the method of administration and the duration of their effect on the body.
Spinal Block vs. Epidural
When an anesthetic is administered around the major nerves or the spinal cord in the lumbar spine, it blocks the pain signals from reaching the brain, thereby providing relief from pain. The preparation is the same for these procedures. First of all, the patient is asked to sit or lie down on his/her side. The area of the lumbar spine where the block has to be administered is cleaned with a sterile solution. The area is numbed with a local anesthetic. In some cases, fluids and/or sedatives might be administered intravenously.
Though the goal of administering spinal block or epidural is the same, the procedures are different in the following ways.
The Site and the Method of Administration
The spinal block involves the injection of a local anesthetic into the subarachnoid space, which is the area around the spinal cord that contains the cerebrospinal fluid. The spinal fluid is a clear, watery fluid that transports nutrients and wastes. Acting like a cushion, it protects the nerve tissues from getting damaged by the insides of the vertebrae. It must be noted that small doses of the local anesthetic can suffice, as it spreads easily and quickly through the spinal fluid. The anesthetic may or may not be combined with a narcotic. The anesthetic agent and/or drug is injected into the subarachnoid space through a small needle. Thereafter, the needle is removed. The administration of the spinal block might take anywhere between 5 and 20 minutes.
For the epidural, the patient will be asked to lie (on the stomach or side) or sit on the table. Thereafter, the site of injection will be cleaned and numbed with a local anesthetic. A larger dose of the local anesthetic will be required, as the drug has to spread through tissues. Intravenous administration of fluids is also required. First, a special needle is inserted into the epidural space, which is the outermost part of the spinal canal that lies outside the dura mater, which in turn is the space that contains the spinal cord, cerebrospinal fluid, subarachnoid space, and the arachnoid mater. Once the needle is in place, a small catheter is placed into the epidural space through the needle. Thereafter, the needle is removed. Unlike spinal block that involves a one-time shot, an epidural gives the option of providing the patient with a continuous supply of anesthetic and/or narcotics through the catheter. This can certainly help the patients to deal with postoperative pain. This procedure can take anywhere between 10 to 25 minutes.
Spinal blocks are usually recommended for procedures that are shorter and simpler. Since the anesthetic is directly injected into the cerebrospinal fluid, its effect can be felt soon after the administration. The effect is stronger, and the patient might not experience any bodily sensation. On the other hand, the effect of an epidural might be felt after 10 to 20 minutes. Once the epidural takes effect, the patient will not experience pain. However, he might still experience some sensation. Epidural works well for longer procedures. The use of a catheter makes it possible to administer anesthetics and narcotics, which helps in extensive procedures that might be associated with postoperative pain.
A spinal block might be administered for surgical procedures involving the lower abdominal region, lower limbs, hernia repair in the groin, prostate or gynecological surgery, etc. Though an epidural block is mostly recommended in case of pregnant women during labor and women who would be undergoing a Cesarean (C-section), it might also be suggested in case of surgeries of the gastrointestinal tract. Similarly, a spinal block could also be administered for C-sections. It must be noted that the effect felt by the patient would also vary, depending on the type and the dose of the drug that is injected.
Though certain side effects can occur, these can be easily managed. Many of the side effects can be avoided, if the right technique is followed and care is taken to avoid adverse drug interactions.
A spinal block can cause back pain, headaches, or low blood pressure. However, complications are more likely to occur in the event of damage to the nerve fibers due to the direct placement of the needle into a spinal nerve. In rare cases, the patient might develop an infection or seizures. Such complications can be avoided, if the proper technique is followed while administering a spinal block.
Epidural anesthesia is considered to be a safe procedure, but there's still a risk of anesthesia-related complications. For instance, problems can arise if the tip of the catheter enters a vein, thereby causing the local anesthetic to enter the blood vessels. This can give rise to seizures or disturbances in the heart rhythm. The patient might experience headaches in case of a dural puncture. A dural puncture is said to occur, when the needle punctures the dura, thereby entering the spinal space. Problems could also arise due to the compression of nerves by a hematoma in the epidural space.
On a concluding note, spinal block and epidural block are both effective methods of the administration of anesthesia or other drugs. However, each of these methods has its own set of advantages and disadvantages. While spinal block has an almost instant effect, the epidural block is preferred, when the effect of anesthesia or painkillers is needed for a longer duration.