Process and Effects (Magill’s Medical Guide, Sixth Edition)
In humans, pregnancy lasts an average of forty weeks, counting from the first day of the woman’s last menstrual cycle. Actually, ovulation, and therefore conception and the start of pregnancy, does not normally occur until about two weeks after the beginning of the last menstrual period, but because there is no good external indicator of the time of ovulation, obstetricians and other health care providers typically count the weeks of pregnancy using the easily observed last period of menstrual bleeding as a reference point. Because of the uncertainty about the actual time of ovulation and conception, the calculated due date for an infant’s birth may be inaccurate by as much as two weeks in either direction.
There is incomplete understanding of the processes that determine the timing and initiation of childbirth. Near the end of pregnancy, the uterus undergoes changes that prepare it for the birth process: The cervix softens and becomes stretchy, the cells in the uterus acquire characteristics that enable them to contract in a coordinated fashion, and the uterus becomes more responsive to hormones that cause contractions.
A number of substances are involved in the preparation of the uterus for birth, including the hormones estrogen and progesterone (produced within the placenta), the hormone relaxin (from the maternal ovary and/or uterus), and prostaglandins (produced within the uterus). The fetus participates...
(The entire section is 1539 words.)
Complications and Disorders (Magill’s Medical Guide, Sixth Edition)
If the labor and delivery do not progress normally, the attendant has available a number of medical interventions that will promote the safety of both the mother and the baby. For example, labor may be induced by administration of oxytocin through an intravenous catheter. Such induction is performed if the amniotic membrane ruptures without the spontaneous onset of uterine contractions, if the pregnancy progresses well beyond the due date, or in response to maternal indicators such as hypertension. The induction of labor has been found to be safe, but careful monitoring of the progress of labor is required.
Another fairly common procedure is the use of forceps to assist delivery. These tonglike instruments have two large loops that are placed on the sides of the fetal head when the head is in the birth canal. Forceps are not used to pull the fetus from the birth canal; instead, they are used to guide the fetus through the birth canal and to assist in the downward movement of the fetus during contractions. The use of forceps can help to speed the second stage of labor, and injury to the fetus or the mother is minimal when the forceps are not applied until the fetal head is well within the birth canal, as is the convention. Some type of anesthesia is always used with a forceps delivery. In some areas, vacuum extraction of the fetus is preferred. As the name implies, vacuum extraction makes use of a suction cup on...
(The entire section is 926 words.)
Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Prior to 1800 in the United States, most women were attended during childbirth by female midwives. In some areas, a midwife was provided a salary by the town or region; her contract might stipulate that she provide services to all women regardless of financial or social status. In other areas, midwives worked for fees paid by the clients. Midwives of this time had little, if any, formal training and learned about birth practices from other women. Because birth was considered a natural event requiring little intervention on the part of the attendant, the midwife’s medical role was limited and the few doctors available were consulted only in difficult cases. Although birth statistics were not kept at the time, anecdotal accounts from the diaries of midwives and doctors suggest that the births were most often successful, with rare cases of maternal or infant deaths.
The nineteenth century saw a gradual shift away from the use of midwives to a preference for formally trained male doctors. This shift was made possible by the establishment of medical schools that provided scientific training in obstetrics. Because these schools were generally closed to women, only men received this training and had access to the instruments and anesthesia that were coming into use.
Maternity hospitals came into being during the nineteenth century but were at first used primarily by poor or unmarried women. Women of higher social...
(The entire section is 678 words.)
For Further Information: (Magill’s Medical Guide, Sixth Edition)
Ammer, Christine. The New A to Z of Women’s Health: A Concise Encyclopedia. 6th ed. New York: Checkmark Books, 2009. A respected classic that covers the full spectrum of women’s health issues, including reproduction and childbearing.
Creasy, Robert K., and Robert Resnik, eds. Maternal-Fetal Medicine: Principles and Practice. 5th ed. Philadelphia: W. B. Saunders, 2004. This complete text covers all aspects of pregnancy and delivery, from conception to medical care of the newborn. Chapters cover normal physiology as well as problems and their treatment.
Cunningham, F. Gary, et al., eds. Williams Obstetrics. 23d ed. New York: McGraw-Hill, 2010. This standard medical school text is still named in honor of its first author, J. Whitridge Williams, who was a professor of obstetrics at Johns Hopkins Medical School at the beginning of the twentieth century. Although written for the medical specialist, this work is fairly easy to read.
Klaus, Marshall H., John H. Kennell, and Phyllis H. Klaus. Doula Book: How a Trained Labor Companion Can Help You Have a Shorter, Easier, and Healthier Birth. 2d ed. Reading, Mass.: Perseus, 2002. Explores the growing trend of doulas in the labor room. Provides advice on finding and working with a doula and details how doulas statistically reduce the need for cesarean section, shorten the length of labor, decrease the pain medication...
(The entire section is 466 words.)
Childbirth (Encyclopedia of Medicine)
Childbirth includes both labor (the process of birth) and delivery (the birth itself); it refers to the entire process as an infant makes its way from the womb down the birth canal to the outside world.
Childbirth usually begins spontaneously, following about 280 days after conception, but it may be started by artificial means if the pregnancy continues past 42 weeks gestation. The average length of labor is about 14 hours for a first pregnancy and about eight hours in subsequent pregnancies. However, many women experience a much longer or shorter labor.
Labor can be described in terms of a series of phases.
First stage of labor
During the first phase of labor, the cervix dilates (opens) from 00 cm. This phase has an early, or latent, phase and an active phase. During the latent phase, progress is usually very slow. It may take quite a while and many contractions before the cervix dilates the first few centimeters. Contractions increase in strength as labor progresses. Most women are relatively comfortable during the latent phase and walking around is encouraged, since it naturally stimulates the process.
As labor begins, the muscular wall of the uterus begins to contract as the cervix relaxes and...
(The entire section is 3419 words.)
Childbirth (Encyclopedia of Children's Health)
Childbirth is formally divided by the medical field into three stages. The first stage is labor, which has three phases: early, active, and transitional. The first stage ends with complete dilatation (opening) of the cervix. The second stage is delivery, which involves pushing and the actual birth of the baby. The third stage is delivery of the placenta or afterbirth.
A full-term pregnancy is considered to be 280 days, nine calendar months or ten lunar months calculated from the first day of the last menstrual period. This is a fairly arbitrary number that may, in fact, vary with genetic differences and depends on a normal menstrual cycle, which varies considerably from woman to woman. The average actual length from conception to birth is estimated as 267 days. Childbirth is a natural process,
(The entire section is 4081 words.)
Childbirth (Encyclopedia of Alternative Medicine)
Childbirth, or parturition, is the process of labor that dilates the cervix, as well as the delivery of the baby and placenta through the birth canal.
Most babies are born following approximately nine calendar months of pregnancy. Delivery between 372 weeks of gestation is considered normal and full-term. A baby born prior to 37 weeks of gestation is considered premature, or preterm. After 42 weeks, it is considered postterm. Each of the latter circumstances is considered a higher risk delivery.
Labor occurs in three stages. The first is the dilation of the cervix, the second is the delivery of the baby, and
the third is the expulsion of the placenta. However, approximately 25% of babies born in the United States are surgically delivered by Caesarean section. This can be a necessary and even life-saving procedure, but this percentage is probably much larger than it could be with better management of labor and more informed birthing consumers.
A 2001 report showed that...
(The entire section is 2742 words.)
Childbirth (Encyclopedia of Nursing & Allied Health)
Childbirth includes both labor (the process of birth) and delivery (the birth itself); it refers to the entire process as an infant makes its way from the womb down the birth canal to the outside world.
Childbirth usually begins spontaneously, following about 280 days after conception, but it may be started by artificial means if the pregnancy continues past 42 weeks gestation, or if complications develop. Labor may also begin prematurely. The average length of labor is about 14 hours for a first pregnancy and about eight hours in subsequent pregnancies. However, many women experience a much longer or shorter labor.
Labor can be described in a series of phases.
First phase of labor
During the first phase of labor, the cervix dilates (opens) from 00 cm (0 in). This phase has an early, or latent, phase and an active phase. During the latent phase, progress is usually very slow. It may take quite a while and many contractions before the cervix dilates the first few centimeters. Contractions increase in strength and frequency as labor progresses. Most women are relatively comfortable during the latent phase.
As labor begins, the muscular wall of the uterus contracts and relaxes as the cervix thins and expands. As a portion of the amniotic sac surrounding the baby is pushed into the opening, it bursts under the pressure, releasing amniotic fluid (water breaking). Sometimes the amniotic sac breaks before labor begins.
During this first phase the birth attendant or nurse will do periodic pelvic exams to determine how the labor is progressing. If the contractions aren't forceful enough to open the cervix, a drug called oxytocin (Pitocin) may be given to make the uterus contract.
As pain and discomfort increase, women may be tempted to request pain medication or anesthetics. If possible, though, these should be delayed until the active phase of labor beginst which point the medication will not slow down or stop the labor.
The active stage of labor is faster and more efficient. In this phase, contractions are longer and more regular, usually occurring about every two to three minutes. These stronger contractions are also more painful. Women who use the breathing exercises learned in childbirth classes find that these can help them cope with the pain experienced during this phase. Many women also receive some pain medication at this pointither a short-term narcotic or epidural anesthesia.
As the cervix dilates to 8 cm (3.15.54 in), the transition phase begins. This refers to the progression from the first phase, during which the cervix dilates, to the second phase, during which the baby is pushed out through the birth canal. As the cervix dilates completely and the baby's head begins to descend, women feel the urge to push or bear down.
Second stage of labor
When the top of the baby's head appears at the opening of the vagina, the birth is nearing completion. First the head passes under the pubic bone. It fills the lower vagina and stretches the perineum. This position is called "crowning," since only the crown of the head is visible. When the entire head is out, the shoulders follow. The attending practitioner may suction the baby's mouth and nose to ease its first breath. The rest of the baby usually slips out easily, and the umbilical cord is cut.
As the baby's head appears, the perineum may be stretched so tightly that the baby's progress is slowed. If there is risk of tearing the mother's tissue, the doctor or midwife may make a small incision, called an episiotomy, into the perineum to enlarge the vaginal opening. If the woman has not had an epidural or pudendal block, she will get a local anesthetic to numb the area. Once the episiotomy is made, the baby is born with a few pushes.
In the final stage of labor, the placenta is pushed out of the vagina by the continuing uterine contractions. The placenta is pancake shaped and about 10 in (25.4 cm) in diameter. During the pregnancy it was attached to the uterine wall and conveyed nourishment from the mother to the fetus. Continuing uterine contractions release it from the uterus at this point. It is important that all of the placenta be removed from the uterus. If it is not, the uterine bleeding that is normal after delivery may be much heavier, and uterine infection may occur.
Approximately 4% of babies are in what is called a "breech" position when labor begins. In breech presentation, the baby's bottom or legs press against the cervix and are positioned to enter the birth canal. An obstetrician may attempt to turn the baby to a head-down position using a technique called version before labor begins. This is only successful approximately half the time.
The risks of vaginal delivery with breech presentation are much higher than with a head-first presentation. In these cases the mother and attending practitioner will need to weigh the risks and decide whether to deliver via cesarean section or attempt a vaginal birth. The extent of the risk depends to a great extent on the type of breech presentation, of which there are three:
- Frank breechhe baby's legs are folded up against its body. This is the most common and the safest for vaginal delivery.
- Complete breechhe baby's legs are crossed under and in front of the body.
- Footling breechne or both legs are positioned to enter the birth canal. Vaginal delivery with this presentation is considered unsafe.
Several factors should be considered before attempting a vaginal breech birth. An ultrasound examination should be done to be sure the baby's head is not unusually large, and that it is flexed (tilted forward) rather than hyperextended (tilted back). Fetal monitoring and close observation of the progress of labor are also important. If labor slows or there is any sign that it will be difficult for the baby to pass through the pelvis it may be safer to consider a cesarean section.
If the labor is not progressing as it should, the baby appears to be in distress, or the mother is too exhausted to push, the doctor may opt for a forceps delivery. A forceps is a spoon-shaped device that resembles a set of salad tongs. It is placed around the baby's head so the doctor can pull the baby gently out of the vagina. Forceps can be used after the cervix is fully dilated.
Before placing the forceps around the baby's head, pain medication or anesthesia may be given to the mother. The doctor may use a catheter to empty the her bladder, and may clean the perineal area with soapy water. Often an episiotomy is done before a forceps birth, although tears can still occur.
The obstetrician slides half of the forceps at a time into the vagina and around the side of the baby's head to gently grasp the head. When both halves are in place, the doctor pulls on the forceps to help the baby through the birth canal as the uterus contracts. Sometimes the baby can be delivered this way after the very next contraction.
When used by an experienced physician, forceps can save the life of a baby in distress. Complications from this type of delivery include nerve damage or bruises to the baby's face. The frequency of forceps delivery varies from one hospital to the next, depending on the experience of staff and the types of anesthesia offered at the hospital. Some obstetricians accept the need for a forceps delivery as a way to avoid cesarean birth. Others don't use forceps at all.
This method of helping a baby out of the birth canal was developed as a gentler alternative to forceps. As with forceps, vacuum-assisted birth can only be used after the cervix is fully dilated and the head of the fetus has begun to descend through the pelvis. In this procedure, the doctor uses a device called a vacuum extractor, placing a large rubber or plastic cup against the baby's head. A pump creates suction that gently pulls on the cup to gently ease the baby down the birth canal. The force of the suction may cause a bruise on the baby's head, but it fades in a day or so.
The vacuum extractor is not as likely as forceps to injure the mother, and it leaves more room for the baby to pass through the pelvis. However, there may be problems in maintaining the suction with this method, and there is the potential for brain damage if repeated attempts are made, so forceps may be a better choice if it is important to remove the baby quickly.
A cesarean section, also called a C-section, is a surgical procedure in which incisions are made through a woman's abdomen and uterus to deliver her baby. The procedure is used to deliver nearly 25% of babies born in the United States; the rate can be as high as 60% for mothers who have had a previous C-section. Cesarean sections are performed whenever abnormal conditions complicate labor and vaginal delivery, threatening the life or health of the mother or the baby.
Labor complications include: abnormalities in the mother's birth canal; abnormalities in the fetus's position; an unusually large baby; and abnormalities in the labor, including weak or infrequent contractions. Another complication is fetal distress, a condition in which the fetus does not get enough oxygen. This can lead to fetal brain damage. The mother's health can also influence the decision to deliver by C-section, especially if she has vaginal herpes, pregnancy-induced hypertension, or diabetes.
Causes and symptoms
One of the earliest signs of approaching labor is loss of the "mucous plug," the thick secretion that covers the cervix during the nine months of pregnancy to protect the fetus from infection. Another is the "bloody show," which is produced by broken capillaries in the cervix. Both the mucous plug and the bloody show appear as the cervix begins to expand and dilate in preparation for labor.
The most common indication that labor has begun is the onset of contractions. Sometimes women have trouble telling the difference between early contractions and and false labor pains, but the biggest distinction is that true labor pains develop a regular pattern, with contractions coming closer together.
Another less common sign that labor is beginning is the breaking of the amniotic sac that cushioned the baby during the pregnancy. When it breaks, it releases water in a trickle or a gush. Only about 10% of women actually experience this water flow in the beginning of labor, however. Most of the time, the rupture occurs sometime later in labor. If the amniotic sac doesn't rupture on its own, the birth-attendant may break it during labor.
A few women have diarrhea or nausea as labor begins. Others notice a sudden surge of energy and the urge to clean or arrange things right before labor begins; this is known as "nesting."
The progression of labor can be determined by measuring how much the cervix has dilated. The degree of dilation is estimated by feeling the opening cervix during a pelvic exam. Dilation is measured in centimeters, from 00 cm (0 in). Contractions that cause the cervix to dilate are the sign of true labor.
Fetal monitoring is a process in which the baby's heart rate is monitored for indicators of stress during labor and birth. There are several types of fetal monitoring.
A special stethoscope called a fetoscope may be used. This is a simple and noninvasive method.
The Doppler method uses ultrasound; it involves a handheld listening device that transmits the sounds of the heart rate through a speaker or into an attached ear piece. It can usually pick up the heart sounds 12 weeks after gestation. This method offers intermittent monitoring. It allows the mother freedom to move about and is also useful during contractions.
Electronic (external) fetal monitoring, in which a monitor is strapped to the mother's abdomen, uses ultra- sound to measure the fetal heartbeat in relation to the mother's contractions. It is often used in high-risk pregnancies, and is not always recommended for low-risk ones because it renders the mother immobile. External monitoring can be done intermittently, as needed.
Internal monitoring provides continuous monitoring for the high-risk mother. It requires the mother's water to be broken and that she be 2 cm (0.75.25 in) dilated. An electrode is attached to the baby, usually on the head, and a pressure catheter records the strength of uterine contractions. Internal monitoring is more accurate than external fetal monitoring, because external monitors are more likely to slip off. Internal monitoring is continuous.
Telemetry monitoring, the newest type, is similar to electronic monitoring, but uses radio waves beamed from a transmitter worn by the mother to measure the fetal heartbeat. The mother is able to remain mobile while still being monitored continuously.
FETAL MONITORING RESULTS. The results of internal and external fetal monitoring are both displayed and printed. Most interpretations are based on the printed tracing. The top tracing reflects fetal heart rate; the bottom tracing measures contractions. Baseline fetal heart rate is considered normal if it is between 120 and 160 beats per minute (bpm). Monitoring of contractions with an external fetal monitor gives the frequency and duration of the contractions. Internal monitoring of contractions can provide contraction intensity values.
Most women choose some type of pain relief during childbirth, ranging from relaxation and imagery to powerful drugs. The specific choice may depend on what's available, the woman's preferences, her doctor or midwife's recommendations, and how the labor is proceeding. All drugs have some risks and some advantages.
REGIONAL ANESTHETICS. Regional anesthetics include epidurals and spinals. Depending on the type of medication used, these types of anesthesia can block nerve signals, causing temporary pain relief, or a loss of sensation from the waist down. An epidural or spinal block can provide complete pain relief during cesarean birth.
An epidural is placed with the woman lying on her side or sitting up in bed with the back rounded to allow more space between the vertebrae. Her back is scrubbed with antiseptic, and a local anesthetic is injected in the skin to numb the site. The needle is inserted between two
vertebrae and through the tough tissue in front of the spinal column. A catheter is threaded through the needle and the needle is then removed. The anesthetic then drips continuously through the catheter.
Epidurals provide complete pain relief and can help conserve a woman's energy, allowing her to relax or even sleep during labor. This method requires an IV and fetal monitoring. It may be harder for a woman to bear down when it comes time to push, although the amount of anesthesia can be adjusted as this stage nears.
Spinal anesthesia is used primarily for C-section delivery. Unlike epidural anesthesia, which is administered continuously in the space around the spinal column, spinal blocks are one-time injections of anesthetic that go directly into the fluid that surrounds the spine. Although this method disables motor nerves, preventing women who use it from pushing during delivery, this is not an issue during a C-section. Spinals provide quick and strong anesthesia and permit major abdominal surgery with minimal pain.
NARCOTICS. Short-acting narcotics can ease pain and do not interfere with a woman's ability to push. However, they can cause sedation, dizziness, nausea, and vomiting. Narcotics cross the placenta and may slow down a baby's breathing. For this reason they can not be given too close to the time of delivery.
METHODS OF PREPARATION. Health care providers often use psychoprophylaxis to help expectant mothers prepare for childbirth. These techniques use relaxation and breathing exercises along with other methods to diminish the discomfort and fear many women experience in childbirth. Although several distinct methods have evolved since the 1930s, when psychoprophylaxis first gained acceptance in the medical community, most doctors, nurses, and midwives today use a combination of approaches to instruct their patients.
The Read method is named for Dr. Grantly Dick- Read, the English obstetrician who developed it in the 1930s. This method aims to decrease the fear and tension surrounding childbirth by educating the mother about the birth process, and using relaxation and deep breathing techniques.
Lamaze, or Lamaze-Pavlov, is probably the best- known method in the United States today, although the pure Lamaze method is rarely used. It first became widely popular in the 1960s. The Lamaze method combines breathing exercises with concentration on a focal point to allow mothers to control pain while maintaining consciousness. This also allows the flow of oxygen to the baby and to the muscles in the uterus to be maintained. A partner coaches the mother throughout the birthing process.
The LeBoyer method stresses a relaxed delivery in a quiet, dim room that prevents overstimulation of the baby. Mother-child bonding is fostered by placing the baby on the mother's abdomen and by having the mother massage the baby immediately after delivery. Then the father washes the baby in a warm bath.
The Bradley method is called father-coached childbirth because it encourages the father to serve as coach throughout the labor. It encourages normal activities during the first stages of labor.
A newer method, called water birthing, allows mothers to labor and sometimes deliverrovided a doctor, nurse, or midwife is at handn a pool of warm water. The water supports and relaxes the mother, making labor more comfortable.
National U.S. health goals are to reduce the maternal mortality rate to no more than 3.3 deaths per 100,000 live births. The baseline in 1998 was 7.1 maternal deaths per 100,000 live births. The target for fetal and infant death reduction during the perinatal period (28 weeks of gestation to seven days or more after birth) is no more than 4.5 per 1,000 live births plus fetal deaths. The baseline in 1997 was 7.5 per 1,000.
Health care team roles
The nurse or nurse-midwife caring for the patient during labor and delivery will perform the following:
- Obtain an initial history and perform a physical examination upon admission.
- Determine the position of the baby.
- Assess for rupture of membranes.
- Determine the cervical dilation, effacement, and level of descent (station), and confirm presenting part through vaginal exam.
- Monitor vital signs.
- Monitor baby's heartrate and measure frequency and duration of contractions. Apply fetal monitoring apparatus if ordered. Observe tracing and record results in patient's record.
- Encourage involvement of the father and provide explanations to him as requested.
- Insert IV if ordered. Obtain laboratory specimens; evaluate results.
- Provide comfort measures through emotional support, changing pads, giving ice chips if allowed, giving back massages, assisting with breathing during contractions, administering pain medications, and assisting with regional anesthesia administration.
- Implement emergency measures if necessary.
- Assist with vaginal exams, rupturing the membranes (amniotomy) and other procedures as indicated.
- Prepare for delivery by setting up instruments, transporting to delivery room or readying birthing bed, and preparing equipment for initial newborn care.
- Provide coaching during pushing and delivery.
- Receive the baby after delivery and perform initial newborn care.
- Administer medications as ordered.
- Assess the mother and baby frequently after delivery.
- Provide perineal care for the mother.
- Monitor mother's and baby's vital signs.
- Assist mother with breastfeeding.
- Facilitate bonding of baby with mother, father, and other family members.
Amniotic sache membranous sac that surrounds the embryo and fills with watery fluid as pregnancy advances.
Breech birthirth of a baby bottom- or feet-first, instead of the usual head first delivery. This can add to labor and delivery problems because the baby's bottom doesn't mold a passage through the birth canal as well as the head.
Cervix small cylindrical organ, about an inch(2.54 cm) or so long and less than an inch around, that makes up the lower part and neck of the uterus. The cervix separates the body and cavity of the uterus from the vagina.
Embryohe unborn child during the first eight weeks of its development following conception.
Gestationhe period from conception to birth, during which the developing fetus is carried in the uterus.
Perineumhe area between the thighs that lies behind the genital organs and in front of the anus.
Placentahe organ that develops in the uterus during pregnancy and that links the blood supplies of mother and baby.
Cunningham, F. Gary, et.al. Williams Obstetrics. 20th ed. Stamford, CT: Appleton & Lange, 1997.
Pillitteri, Adele. Maternal & Child Health Nursing. 3rd ed. Philadelphia: Lippincott, 1999.
American Academy of Husband-Coached Childbirth. PO Box 5224, Sherman Oaks, CA 91413. (800) 423-2397; in California (800) 422-4784. www.bradleybirth.com.
The American College of Nurse-Midwives. 818 Connecticut Ave. NW, Suite 900, Washington, D.C. 20006. (202) 728-9860. www.acnm.org.
Association of Women's Health, Obstetric, and Neonatal Nurses. 2000 L Street, NW, Suite 740, Washington, D. C. 20036. (800) 673-8499 U.S., (800) 245-0231 Canada. www.awhonn.org.
International Childbirth Education Association. PO Box 20048, Minneapolis, MN 55420. (612) 854-8660. www.icea.org.
Burgess, Traci. "Benefiting from Childbirth Education." <<a href="http://www.spindlepub.com/emg/library/EBKed5.htm">http://www.spindlepub.com/emg/library/EBKed5.htm>.
Department of Health and Human Services. "Healthy People 2010" <<a href="http://www.health.gov/healthypeople/default.htm">www.health.gov/healthypeople/default.htm>.
Hargett, Dave, "Anesthesia and the Apnea Patient." <<a href="http://www.apneanet.org/anesthes.htm">http://www.apneanet.org/anesthes.htm>.
McKesson HBOC Clinical Reference Systems: Adult Health Advisor. "Anesthesia."
<<a href="http://www.realage.com/Connect/healthadvisor/adulthealth/crs/anesthes.htm">http://www.realage.com/Connect/healthadvisor/adulthealth/cr... >.
Nadine M. Jacobson, R.N.