Analgesia means relief of pain; anesthesia means loss of sensation. There are ways of injecting certain drugs in particular areas of the body to cause a loss of all sensation (numbness) in a limited area. Local anesthetic agents, like Novocain (procaine) used by your dentist, are used in this way.
Agents such as lidocaine and bupivacaine are used in obstetrics. Depending on where they are injected, they cause varying amounts of pain relief. For example, a spinal or saddle block creates a rather large area of total numbness. An injection of anesthetic is made in the lower part of the back, and the medicine enters the spinal fluid. The anesthetic is heavy and stays low in the spine. You might become numb from your ribs down to your toes (spinal block) or from your buttocks and lower part of the abdomen down your inner thighs (saddle block). The amount of numbness is determined by how low the injection is given, how low in the spinal canal the medicine remains, and what concentration of anesthetic solution is used. You can have a spinal headache after a spinal anesthetic; this is very painful, can last for days, and usually requires you to lie down much of the time.
Because spinals can stop labor at a critical time, they tend to be used for very late labor and for cesarean births.
Epidural and caudal blocks differ from spinal blocks; they are given with the same anesthetic agents but in slightly different places. The main difference is they are not injected into the spinal fluid. The medicine is placed low in the back, just outside the canal where the spinal fluid is (therefore, you do not get a spinal headache). Although trickier to give than a spinal block, anesthesiologists prefer them for labor because they are not as likely to stop labor, and the actual area of anesthesia can be better controlled (especially with the epidural).
The main difference between the caudal and the epidural block is the site at which they are administered: The caudal is given at the top of the separation of your buttocks; the epidural, a few inches higher. As a result, the area of numbness with the epidural tends not to extend as far down into your birth canal and legs as with the caudal. You can push better and move your legs better with an epidural.
Both spinal and epidural blocks are also used for cesarean births, allowing the mother to remain awake and alert to greet her baby.
Pain relief with these forms of regional anesthesia can be excellent; in fact, many women report total relief of pain. This welcome relief comes with no effects on your mental capacity. You do not become groggy or sleepy.
Forceps-assisted deliveries tend to be more common after regional anesthesia because women cannot push as well when anesthetized. Anesthesia can be light or heavy; women can push better (and feel more) if the anesthesia is light.
Another drawback to regional anesthesia is the possibility of a sudden drop in blood pressure soon after receiving the anesthetic. This sudden drop can temporarily reduce the amount of oxygen available to the baby. Since this side effect is well known, measures are taken to prevent it, identify it as soon as it happens (blood pressure is checked constantly while the anesthetic takes effect), and treat it, if necessary, with drugs.
Three types of local anesthesia may be used for childbirth: the paracervical block, the pudendal block, and local infiltration of the perineum.
The paracervical block is given during the late first stage. Two injections of local anesthetic drugs are made into the cervix and bring pain relief during contractions. Although this form of anesthesia rarely causes problems for the mother, it frequently causes sudden drops in the fetal heart rate and noticeable effects on the baby's muscle tone and reactivity after birth.
Although the amount of pain relief provided by a paracervical block is far less than with the regional blocks, a significantly greater amount of the anesthetic agent is used -- thus, more serious side effects occur. So this form of block has been discontinued in many areas of the country.
The pudendal block causes anesthesia in the birth canal and is given in the second stage. Local anesthetic agents are injected into each side of the vaginal wall. Again, a larger amount of medication is used than for an epidural, but the incidence of drops in fetal heart rate appears not as serious as with the paracervical block. A pudendal block can be used for forceps delivery or pain in the second stage. Most doctors also give a pudendal block before an episiotomy is performed.
Local infiltration of the perineum consists of several injections to numb the area of skin and muscle between the vagina and the anus. It is most commonly used after natural childbirth if stitches are needed. It can also be given in the second stage before an episiotomy is performed. Side effects of a local block appear to be slight.
General anesthesia means a loss of consciousness along with pain relief. In other words, a woman is put to sleep and wakes up after the anesthetic has worn off. Nowadays, general anesthesia is uncommonly used-and is generally reserved for emergency situations.
General anesthetics are usually gases, which are inhaled. They cause a total loss of awareness. Nitrous oxide, Trilene (trichloroethylene), and Penthrane (methoxyflurane) are examples of such inhalation agents. Sometimes these are used along with sedatives that cause drowsiness. The sedatives might be injected into your vein.
One reason general anesthetics are used less often today is that they have profound side effects. The mother's breathing may slow down or stop; her blood pressure may drop and cause her heart rate to change. General anesthetics may also stop contractions of the uterus and cause excessive bleeding after birth. The baby is also affected. Babies often have breathing difficulties, sucking difficulties, and poor muscle tone after the use of general anesthetics.
Now that you have a basic understanding of childbirth medications, talk to your doctor about what the right choices will be for you during your birth process.
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ABOUT THE AUTHOR:
Elizabeth Eden, M.D. is a practicing obstetrician with her own private practice in New York City. She serves as an attending physician at the Tisch Hospital of the New York University Medical Center, as well as a Clinical Assistant Professor at the New York University School of Medicine.