Although oxytocin has been used to augment labor for more than 100 years,1 it is still the leading cause of malpractice claims and liability payout in obstetrics.2 There are controversies about high-dose oxytocin versus low-dose oxytocin, when to stop oxytocin induction/augmentation, when to start oxytocin induction/augmentation, how fast to increase the dose of oxytocin, how to treat hyperstimulation of the uterus from oxytocin inductin/augmentation, what is hyperstimulation of the uterus, among others. In 2007, oxytocin was designated a high-alert medication by the Institute for Safe Medication Practice, meaning that it is a drug that bears a heightened risk of harm and may require special safeguards to reduce the risk of error.3 Oxytocin is one of only 13 medications on the Institute for Safe Medication Practice high-alert list.4

Many of the controversies surrounding the use of oxytocin for induction or augmentation of labor can be answered by an understanding of the chemical mechanism of oxytocin. However, the true starting point for any question regarding oxytocin induction or augmentation of labor begins with qualifying the concept of normal labor. The publication of Friedman's5 curve in 1955 quantified a concept of normal labor as progressing 1 cm/h. Simpson and Miller6 point out that contemporary laboring women differ from those in Friedman's study. Women today are more apt to be electively induced prior to cervical ripeness, to use regional analgesia, to be more obese, and to experience augmentation of labor than laboring women in the 1950s.6 If the practitioner understands that labor may not progress according to a chart or a predetermined curve, the practice of augmentation of labor may decrease.

The practitioner should also understand the normal growth and development of the fetus. The practice of induction prior to 39 weeks has been shown repeatedly to cause problems with infants, now known as late preterm infants. Yet obstetrical practitioners continue this practice and represent the intervention to patients as safe.7 Obstetricians are reluctant to deny induction to an insured, educated population even though there is increased risk to the infant, including increased jaundice, respiratory distress, hypoglycemia, and even death.8

Oxytocin is produced in the hypothalamus, stored in the pituitary, and secreted into the cerebrospinal fluid and then into the maternal circulation.1 Oxytocin receptors are found in the uterus myometrium and decidua and increase dramatically in late pregnancy.1 This is a highly simplified description. Uterine response to synthetic oxytocin, which is used in induction and augmentation, may differ depending on gestational age of the fetus, the mother's myometrial sensitivity to oxytocin, the presence or absence of uterine contractions, and cervical status.1

Physiologically, although initial uterine response to oxytocin is swift, the maximal uterine response may take 40 minutes.1 Clark and colleagues3 point out that increasing an oxytocin dosing regimen at an infusion rate significantly less than 40 minutes will be a "blind" procedure, meaning that an increase in oxytocin is done before the response to the current dose is known.

The exposure to risk associated with oxytocin use is a classic cascade. Oxytocin use may lead to hyperstimulation of the uterus. Hyperstimulation of the uterus may lead to uteroplacental insufficiency, impairing fetal oxygenation. Decreased fetal oxygenation may lead to fetal metabolic acidosis and myocardial depression.2 Ironically, when some practitioners detect this pattern, they may give more oxytocin to accelerate labor or "pit through."

Simpson describes the concept of "normalization of deviance" that occurs in obstetrical care as pertinent to practice in the augmentation and induction of labor.2 Most mothers and fetuses will tolerate hyperstimulation without adverse effects, leading practitioners to practice by anecdote-the previous fetus with hyperstimulation was healthy, so the practice of using oxytocin for labor augmentation or induction outside of guidelines can be safe. Simpson points out that this normalization of deviance usually persists until there is an adverse outcome,2 at which point the practitioner may change practice based on evidence, change practice based on experience, or blame the system for the problem. Clark and colleagues3 state that they know of no other specialty of medicine where practitioners use a potentially dangerous medication that is often clinically unnecessary. This normalization of deviance may also lead to a nursing climate in which staffing ratios are inadequate because risk is not recognized or is minimized.3

Disagreements between the labor nurse at the laboring woman's bedside and the practitioner who is not necessarily in the hospital cause quite a lot of exasperation and dissatisfaction between disciplines. Clark and colleagues3 recognize this source of disagreement and its effect on patient safety and state in strong terms that the person with the greatest actual hands-on experience with the patient and who is actually at the bedside will generally be more credible and able to judge and assess the effect of oxytocin augmentation or induction on the fetus and laboring woman. However, Simpson and Lyndon9 found that only 22% of nurses questioned in a study of labor nurses' responses to clinical disagreements with physicians said that they would follow their own clinical judgment when in conflict with a physician's order to increase oxytocin.9

The myths of "pitting through," halving the amount of oxytocin as a response to hyperstimulation, and "pitting to distress" among others refuse to go away despite good clinical evidence to the contrary. This persistence of non-evidence-supported practice is consistent with the idea of the normalization of deviance. Most infants and mothers tolerate labor and birth without problems. However, good evidence-based practice will support the mechanisms of normal labor and birth and avoid the cascade of intervention that may not harm infants and mothers but does not show benefit and adds cost.

Labor and delivery nurses have the most current information about the laboring woman, the information that takes into account the objective information about contractions, dilatation and the fetal heart rate, as well as subjection information about coping mechanisms, pain, and maternal fatigue. This information is synthesized by the nurse at the bedside into a continuing database about the woman and the fetus. The labor and delivery nurse is the best source of truth about the labor. Failure to update or enforce guidelines can be dangerous, costly, and inefficient. Oxytocin augmentation and induction can be hazardous to mother and fetus and should not be routine but should be tailored to specific situations. Increasing the oxytocin rate should be done according to accepted guidelines that follow the physiologic mechanisms of the drug and of labor and birth, not according to intuition.

As a practicing nurse-midwife who first trained more than 25 years ago and began working as a labor and delivery nurse in the early eighties when synthetic oxytocin was administered through open intravenous catheters without a pump, I found I had also normalized the deviance of increasing the oxytocin dosage for induction, even though I consider myself a strong advocate of normal birth and low intervention when needed. My rationale was by anecdote; I had no untoward outcomes with oxytocin induction. I began the research for this column after experiencing frustration between myself and the labor and delivery nurses I worked with when the nurses would not increase the oxytocin dose on a schedule I considered more practical-every 20 minutes. Discussions with other midwives led me to think about a column to demonstrate that increasing oxytocin dosages on a more frequent basis is safe and could lead to vaginal birth more readily than a dosage based on 30- to 40-minute increases. After reviewing current physiologic knowledge and research regarding the safety of oxytocin induction and augmentation, I plan to change my practice. Increasing oxytocin for laboring women every 20 minutes is changing management without the full picture of a woman's response to the medication and may result in hyperstimulation.

The evidence is clear that injudicious use of oxytocin for induction and augmentation can be harmful for women and fetuses and does not lead to improved birth outcomes. I have learned an important lesson about the normalization of deviance and the attitudes toward intervention that this normalization can foster.

-Jackie Tillett, ND, CNM, FACNM

Associate Clinical Professor

Department of Obstetrics and Gynecology

University of Wisconsin School of Medicine and Public Health

Madison, Wisconsin

References