A guide to preoperative pregnancy testing for the nurse practitioner

AORN Journal, March, 2000 by Kathy Pearson

This article addresses a major concern facing physicians, advanced practice nurses, and nurse practitioners in preoperative settings: When should a clinician order a serum or urine pregnancy test preoperatively? This article discusses the risk of general anesthesia to both the pregnant patient and the fetus in early pregnancy and offers an algorithm that allows clinicians to make appropriate clinical decisions when ordering pregnancy tests. In these situations, concern for the mother's safety is emphasized, and accurate history taking is of utmost importance, in conjunction with prudent, necessary, and timely testing. The result is the avoidance of anesthetizing and performing a procedure on a patient with an undiagnosed pregnancy.

BACKGROUND

In 1995, the nurse practitioners' collaborating physician of the day of surgery admissions/ ambulatory surgery center (DOSA/ASC) at Rochester (New York) General Hospital requested that the obstetric/gynecologic liaison nurse practitioner conduct a review to ascertain the risks involved with performing a surgical procedure on a patient with an unknown early pregnancy. The nurse practitioner was charged with developing a set of guidelines for preoperative pregnancy testing on the female preoperative population (Table 1). These guidelines were written and later approved by the DOSA/ASC advisory committee, the obstetric/gynecologic department, and the medical director of the ambulatory surgery department. A copy of the protocol was provided to department surgical services staff members for future reference, and clinicians and nursing staff members in the preoperative arena of the DOSA/ ASC participated in inservice programs to learn the guidelines.

Table 1

PREOPERATIVE PREGNANCY TESTING GUIDELINES

Preoperative pregnancy testing is recommended only in the presence of

* absent or irregular menses,

* use of contraceptive injections (Depo-Provera) for contraception and the patient is not compliant with the recommended regimen,

* unreliable repealing of last menstrual period,

* uncertain use of contraception in an otherwise fertile female, or

* the surgeon's order.

Preoperative pregnancy testing is not recommended if

* there is a history of tubal ligation, hysterectomy, or bilateral oophorectomy or a history of a monogamous partner with a vasectomy;

* there is a one-year history of amenorrhea consistent with menopause;

* a pregnancy test has been performed within the last five days, and those results can be physically obtained before surgery;

* a patient reports consistent use of oral contraceptives and has normal menses;

* a patient reports consistent use of a intrauterine device or levonorgestrel implants (Norplant system);

Physicians may override these guidelines and order a pregnancy test if desired.

General considerations

Urine tests positive after missed menses.

Serum tests positive within seven to 10 days after conception.

When feasible, order urine pregnancy test because of cost-effectiveness and efficiency in obtaining results.

In 1996, the issue of substituting urine pregnancy tests for serum testing was raised. The literature supported the use of urine pregnancy testing because of its accuracy. In addition, results could be obtained more quickly with urine tests than with serum pregnancy tests, thus decreasing OR delays.(1)

According to the ambulatory surgery medical director at the DOSA/ASC, a quarterly quality review of patients' records revealed inappropriate or excessive ordering of pregnancy tests. Physicians were inconsistent, with some surgeons ordering serum pregnancy tests on all patients less than 55 years of age, regardless of birth control status or gynecologic history (eg, menopausal status; surgical status after hysterectomy, tubal ligation, salpingo-oophorectomy procedures). Other physicians did not request pregnancy tests under any circumstances, even when indicated by the guidelines. Nurse practitioners expressed a need for clarification of the definition of reliable birth control.

In 1998, confusion regarding when to order pregnancy tests--along with an incident of a reported positive pregnancy on a postoperative patient--prompted further research and the creation of a simplified, straightforward algorithm that provides a quick, easy assessment of the female preoperative patient. The algorithm enables clinicians to make clinical decisions that are in the best interest of the patient, and it avoids unnecessary surgical delays and costs.

LITERATURE REVIEW

Existing literature raises many questions about exposure of pregnant women to anesthesia. One study revealed an association between anesthesia exposure in the first trimester and hydrocephalus, although the findings were not totally conclusive.(2) Another study found an increased risk of neural tube defects in the offspring of women who underwent surgery in their first trimester(3) Another researcher stipulated that elective surgery--even with local anesthesia--be postponed until six weeks postpartum to prevent the risk to the fetus of teratogenicity of anesthetic agents.(4) These studies indicate that medicolegal concerns involving the performance of anesthesia and surgery in early pregnancy abound.