Authors: Stephen H. Jackson, M.D.
ASA Monitor 11 2018, Vol.82, 24-27.
Ethical Principles and Informed Consent1-3
The ethical implications of routine (“screening,” non-con-sented) preoperative pregnancy testing often are obscured by scientific and legal misinformation that creates unfounded uncertainty. The process of informed consent honors what the patient wants through respecting the ethical principle of patient autonomy (self-determination). Ethically, a woman has the right to be offered pregnancy testing and to choose to consent – or refuse – testing upon being informed of the scientific facts. Awareness of an unrecognized pregnancy could affect her further decision as to whether or not to proceed with an elective procedure.
Preanesthetic Pregnancy Testing Is NOT an ASA “Standard of Care?”4
“The Task Force recognizes that patients may present for anesthesia with early undetected pregnancy. The Task Force believes thatthe literature is inadequate to inform patients or physicians on whether anesthesia causes harmful effects on early pregnancy. Pregnancy testing may beofferedto female patients of childbearing age and for whom the result would alter the patient’s management.”5
Pregnancy Testing in Women Having Non-obstetric Surgery
Those who argue for mandating pregnancy testing invoke the acknowledged unreliability of menstrual histories. In the U.S., 0.3 percent to 2.2 percent of pregnant women (100,000/year) undergo non-obstetric surgery.6 –8 When screened for pregnancy, 0.15-2.2 percent of adult females of child-bearing age scheduled for surgery test positive.9 –11 Note that there is a high background incidence (31-89 percent) of fetal loss in all pregnancies, half before becoming clinically detectable. These losses implant, yet two-thirds abort before the sixth week of pregnancy, briefly delaying menses (known as a biochemical pregnancy). The remaining third abort spontaneously after the sixth week (blood/urine tests are likely to be falsely positive).
Teratogenicity and Miscarriage
Teratogenicity is any significant alteration (defect) in an infant’s physical form or functional ability caused by prenatal exposure to a teratogen. First trimester organogenesis is the most vulnerable period to teratogenic influences.7,12 There now exists a large body of scientific evidence supporting the safety of anesthesia for the fetus and pregnancy.13 –19 No anesthetic drug (excepting possibly cocaine) is a human teratogen.
Prospective human clinical studies of anesthesia-induced teratogenicity would be unethical.20,21 There are, however, three well-designed retrospective studies on largehuman populations (strongly supported by a number of smaller studies) that do not implicate anesthesia and surgery as causing teratogenicity or early fetal loss.
A Canada (Manitoba) study22 examined health records of all Manitobans during 1971-1978. There was no increase in the incidence of congenital malformations. The incidence of miscarriage was not statistically increased, even when stratified by surgical site. However, a small increase was noted (risk ratio = 1.58) for miscarriage in women receiving general anesthesia, especially for obstetric-gynecologic procedures. Expert commentary concluded, “The magnitude or nature of the surgical procedure is the most relevant [factor] … capable of disturbing the conceptus.”23
A Sweden study24 reviewed all citizens’ health records from 1973 through 1981. There was no increase in the incidence of congenital anomalies, including during the first trimester. The Swedish registries were designed to study only live births and thus failed to capture the incidence of miscarriage; however, there was no increase in the incidence of stillbirths.
A United Kingdom study25 investigated all admissions to the National Health Service during 2002-2012. The estimated risk of a spontaneous miscarriage for pregnant females having surgery was 6.6 percent compared with 5.8 percent for those withoutsurgery. Again, the risk rose with abdominal surgery. The relative risk for miscarriage was significantly lower than Manitoba’s already low figure. This modern study was “unable to disassociate the risk of surgery from the risk of anesthesia or the underlying [surgical] condition … [and] our analysis may provide some reassurance to mothers concerning the risks to their pregnancy.”25
Pregnancy Testing Misinformation
Pre-anesthetic point-of-care (POC) urine testing, while practicable, non-invasive and inexpensive, is unreliable and frequently inaccurate, especially in early pregnancy when urinary human chorionic gonadotropin (HCG) levels may not have reached the detection threshold.26,27 Same-day serum testing is more sensitive and less prone to false negative results.
Placental HCG largely replaces pituitary HCG synthesized during a menstrual cycle.28 Beginning with implantation, the placenta produces two forms of HCG: HCG and hyperglycosylated HCG (HCG-H). HCG-H is the principal or sole form of HCG during the first week of pregnancy and remains the predominant form in the second through fifth weeks.29 The problem is that HCG-H is not detected by most (if not all) urine POC tests! The FDA mandates urine tests to identify only HCG, not HCG-H.30,31 A positive urine HCG result is >10 IU/L. POC urine testing can detect >20 IU/L, but laboratory serum testing can only detect fourfold lesser concentrations (>5 IU/L). Therefore, given the intent to identify an unrecognized early pregnancy, the more sensitive serum test should be deployed.
A false negative test result is especially likely in early pregnancy and erroneously assures a patient that she is not pregnant, upending the process of informed decision-making, and depriving her of choices and options appropriate to her pregnant state. The significant incidence of false negative urine tests resulting from most POC urinetesting methodologies can be caused by 1) inadequate sensitivity for detecting the low concentrations of HCG inherent to early pregnancy; 2) no ability to detect HCG-H; 3) dilutional effects of non-fasting urine; and 4) a HCG renal degradation product, HCG beta-core-fragment (HCG-BCF), that causes false negative results.30,31 Because no POC urine test detects HCG-BCF, false negatives are likely to occur before the fifth week of gestation when HCG levels are low and HGG-H predominates; and after the fifth week when HCG-BCF levels are high and interfere with the HCG assay.
The variable date of implantation is a determinant of the huge range of HCG levels encountered during the 16th-30th days of the menstrual cycle.32 Implantation will occur only as late as the day of missed menses. This suggests a test should not be ordered as early as the time of the missed menses because a negative result could reflect a true negative or a false negative due to the insensitivity of the test to low levels of HCG and/or a late implantation. Therefore, it is recommended that a pregnancy test result should not be considered definitive until, at the least, five days after an expected/missed menses (five weeks after the last menses).
A false positive result might reflect an aborted or biochemical pregnancy. Biochemical pregnancies are accompanied by brief increases in HCG levels that can cause a false positive. Persistent low-level elevation of pituitary HCG (in the absence of pregnancy) can be encountered post miscarriage or pregnancy termination and also in peri- and post-menopause.
The United Kingdom acknowledges that a negative pregnancy test on the day of surgery is not sufficient to exclude early pregnancy and consequently has established a protocol14,27 to “guarantee” that a patient is not pregnant. This mandates 1) abstinence from intercourse or employing appropriate contraception (miniscule likelihood of failure acknowledged) beginning with the first day of the menstrual period before the scheduled surgery; 2) scheduling procedures before the 10th day of a menstrual cycle because, unless a menstrual cycle is extremely short, it is highly improbable to have ovulated and conceived before the 10th day. This protocol demands that surgeons inform the patients as to their responsibility and obtain a signed declaration of compliance.
Malpractice Concerns and Facts – The Anesthesia Closed Claims Project33
The Anesthesia Closed Claims Project identified only 11 of approximately 11,000 (<0.1 percent) cases involving an undiagnosed pregnancy. There were four cases of females of childbearing age in which a pregnancy test was ordered, but the anesthesiologist didnotevaluate the result, providing a background for the report of the 2016 ASA Committee on Quality Management and Departmental Administration that “other than for surgical indications, routine pregnancy testing may pose greater medico-legal risk to anesthesiologists due to failure to check the result or failure to document informed consent of [the minimal] risk of miscarriage prior to elective surgery.”13 Legal and ethically, one should document that a pregnancy test was offered and that the patient provided informed consent – or informed refusal.
The ethical implications of routine (‘screening,’ non-consented) preoperative pregnancy testing often are obscured by scientific and legal misinformation that creates unfounded uncertainty.
Revealing a positive test result my have negative consequences (life-altering and even life-threatening physical violence) for vulnerable patients, especially adolescents, in social environments where a pregnancy is not accepted.1,2,13 The ethical principle of social justice raises the issue of systematic over-testing that increases the costs of health care to all.1,2,34,35
Exempting uterine procedures, surgeries impeding the uterine circulation or significant radiation exposure, pregnancy testing should be offered – not mandated – to women of childbearing age. This ethical approach, supported by the scientific literature and legal experience, focuses on obtaining informed consent for pregnancy testing.
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