How Much Pain-Killer Can a Foetus Take?
How Much Pain-Killer Can a Foetus Take?
December 23, 1983 – January 7, 1984
By Nutan Pandit
Almost every woman hopes for a miracle drug that would do away with labour pains. With the availability of analgesics this is now possible. Nutan Pandit discusses the side effects of these new drugs
Ever since science brought forth its wonder drugs to kill pain in labour, the stress has been to relieve pain. However, presently the limelight has shifted to the welfare and feelings of the baby.
The thalidomide tragedy in 1962 jolted people into realizing that drugs taken by the mother affect not only her but also reach and affect the baby. Thalidomide was a tranquillizer prescribed to pregnant women, which stopped the normal growth of the child in the womb.
Drugs used in labour, likewise pass through the placenta to reach the baby’s blood circulation, exerting an effect similar to that which is exerted on the mother. Hence the drugs given to a woman in labour have to be carefully controlled.
The correct does varies from woman to woman. It also depends on the woman’s condition and stage of labour. The dose has to be strong enough to the desired effect, and not so strong as to have unpleasant or dangerous side effects.
As Dr. R.A. Bradley put it. “The mother weighs 140 pounds, while the baby weighs seven; yet they both get the same dosage (of drug). So if you give the mother an adequate dose, you are giving the baby 20 times as heavy a dose.” Hence a drug which stays in the mother’s bloodstream for two hours, could take the baby two days to eliminate. Thus babies born to drugged mothers are initially sluggish.
Since anesthetics are nervous depressants along with pain they depress all other nervous mechanisms too. The baby consequently is slower to breathe, cry out and develop the sucking reflex.
The ideal labour therefore is, a labour in which the mother and baby receive a minimum of drugs. It was Dr. Dick Reed and Dr. La Maze who taught women how they can cope with labour without recourse to drugs. While Dr. Read stressed relaxation and understanding labour in order to remove fear of it. Dr. La Maze stressed his theory of ‘conditioned reflex’, that is, teaching pre-conditioned breathing responses to women to use at the time of labour.
Dr. Reed felt that civilization introduces fear and anxiety in a pregnant woman. It is reinforced by literature films and other media. The expectation of fear creates a protective tension hampers the uterus in its efforts to open up and thus accentuates pain. This is known as the ‘fear-tension-pain’ response. However, if tension is absent, the woman remains relaxed, her uterine muscles work unhampered by tension and with each contraction get closer to complete dilation, so that a woman has a shorter, less painful labour.
Let us briefly scan the drugs given to women in labour, and the effect they have on mother and child. Pethidine, an intra muscular injection, is an analgesic commonly given to lessen pain at the beginning of labour. Women vary in their reaction to it. Some find it a great help. They may even sleep a few hours, and awake refreshed. Others become drowsy, but are still aware of pain. They dose off only to awaken at the height of pain. This distresses them and reduces their ability to cope. If given two or three hours before the birth, it can result in a depression of the baby’s breathing.
Ihalent analgesics are usually administered in the final stages of labour, by means of a rubber mask held over the mother’s face.
Either trilene or a mixture of nitrous oxide and oxygen is used. Elimination of trilene from the blood and tissues is comparatively slow, since it is not exhaled immediately by the lungs.
As the baby is born, the perineum is injected with local anesthesia, so that a cut can be made to widen the vaginal opening to ease out the baby.
Local anesthesia is also used for paracervical and pudental blocks. A paracervical block is done in the first stage of labour. A local anesthetic is injected into the tissues around the cervix (mouth of the womb) to block the nerves, so that, the uterus or womb becomes insensitive to pain for two or three hours. This can cause a temporary decrease in the supply of oxygen to the baby.
In a study, 93 mothers in America were given paracervical block anesthesia. There was a temporary drop in the babies’ heart rate in half the group. A drop in the heart rate would indicate a decrease in the supply of oxygen. Nobody knows yet how much oxygen loss can be sustained by a child in labour or just after birth before there is neurological damage.
A pudental block is used more often just before a forceps delivery. Not only does it anesthetize the vagina and perineum, but it also relaxes the pelvic floor muscles, thus facilitating delivery. The woman is aware of the urge to bear down, and is able to do so even though forceps are used.
An epidural is another nerve block. An analgesic is injected into the epidural space that runs along the spinal cord inside the backbone. This is done between two vertebrae. It numbs the entire region from the lower abdomen to the feet. Although the epidural is an effective pain killer, it might reduce the mother’s ability to push, and may result in a forceps delivery. A fall in the mother’s blood pressure is also a common complication and occurs in about 5 per cent of the cases. In order to detect this, the blood pressure is taken frequently after an epidural is administered.
Since it is highly skilled and time consuming process, it is important to have a well trained and expert anesthesiologist. A dural puncture can occur if the anesthetic is given inefficiently, or if the woman inadvertently moves during administration. This could result in severe headache after delivery.
However, there are times when an epidural can have valid medical reasons. If the mother has high blood pressure or respiratory distress, heart disease or an abnormal position of the baby in the womb, causing acute labour discomfort.
General anesthesia is given in case of Caesarean section, knowing that the placenta is not a barrier, and everything the mother takes in, including drugs, pass to the baby through it, what we take in, is our responsibility.
It is important to remember any kind of anesthetic or analgesic can, like alcohol leave mighty hangovers. Besides, one intervention tends to lead to another. For instance, drugs that induce labour bring on contractions of such force, that painkillers are used. Painkillers in turn, render a woman less able to manage her own labour and push her baby out, so that forceps are used.
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