General anesthesia refers to anesthesia that produces loss of consciousness, in addition to pain relief. It involves the administration of both intravenous and inhaled drugs in order to achieve a balance of the following factors:
- hypnosis-a state of altered consciousness with the ability to respond;
- amnesia-loss of memory;
- analgesia-pain relief; and
- skeletal muscle relaxation.
When general anesthesia is used during pregnancy or delivery, it is important to reduce the baby's exposure to anesthetic as much as possible.
There are several benefits of general anesthesia over alternative methods:
- General anesthesia can be administered rapidly so that additional procedures, such as a cesarean section, can be performed quickly. This is very useful if an emergency cesarean section is required.
- The mother does not have to sit up to have general anesthesia. Thus, if part of the baby is already in the birth canal when anesthesia is needed, this can be administered without requiring a change in position.
- General anesthesia always provides adequate pain relief. Once under general anesthesia, pain relief is usually not an issue because the patient is essentially asleep. Sometimes an epidural may only give partial relief of pain.
- For some women who require a cesarean section and have had prior back surgery or have back deformities, general anesthesia may be an acceptable alternative to regional or epidural/spinal anesthesia, which can be difficult to administer in these situations. As well, some patients with brain tumors or increased intracranial pressure may not be able to receive an epidural or spinal anesthetic.
The risks associated with general anesthesia can be life threatening and include:
- inability to place an endotracheal tube (breathing tube);
- aspiration (breathing in of fluids or foreign bodies), which can cause pneumonia or permanent brain damage and death;
- toxicity with anesthetic medications; and
- respiratory depression in the newborn.
To avoid these complications, the following steps should be taken:
- Rapid-acting medications that cause muscle relaxation should be used in order to make it easier to place the breathing tube.
- A liquid antacid should be given to lower the acidity of the stomach contents.
- Oxygen should be given before the anesthesia.
- Pressure should be applied to the throat (to compress the cricoid bone located in the neck above the thyroid gland) to block the esophagus and decrease the risk of aspiration.
- Rapid-acting medications that produce amnesia should be used.
General anesthesia may be used for cesarean section delivery. Although regional blocks (spinal or epidural) are preferable, general anesthesia is often used in patients who have bleeding disorders or who require immediate delivery. General anesthesia is also used during cesarean sections when regional anesthesia isn't sufficient.
General anesthesia is rarely used in vaginal delivery because of the risks it poses for both mother and baby. It may be used to protect the mother or baby in emergency situations, such as:
- an unanticipated breech (buttocks-first) birth;
- shoulder dystocia (when the baby's shoulder gets caught in the birth canal);
- internal cephalic version (manipulation of the fetus into a head-first presentation while still in the uterus); and
- extraction of a second twin.
In addition, general anesthesia may be necessary during difficult forceps deliveries in women who should not have regional blocks because of health concerns.