The primary concerns for obstetric anesthesiologists in managing parturients with a history of substance abuse include understanding and managing the acute intoxication, chronic use and its associated comorbidities, acute withdrawal, and recognizing the impact of substance abuse on obstetric and neonatal outcomes. This chapter will discuss exposure to illicit substances, as well as alcohol, tobacco, and caffeine, as they also affect obstetric outcomes and anesthetic management. Making the diagnosis of substance abuse requires a combination of obtaining a thorough history, communication with obstetric colleagues, laboratory analysis, but frequently it depends simply on good clinical judgment. It is noteworthy that many pregnant women abuse multiple substances and that it is often difficult to ascertain the impact of the individual substances from the impact of other associated comorbidities. There is also a strong association between substance abuse and coexisting psychiatric illness, domestic violence, and poor prenatal care.

It is difficult to establish the exact prevalence of substance abuse during pregnancy due to the primary reliance on self-reporting. However, comprehensive epidemiologic statistics are maintained by several government agencies in the United States to monitor trends in the use of illicit drugs, alcohol, and tobacco. The most valuable of these include the Substance Abuse and Mental Health Service Administration (SAMHSA) (1) which is a part of the US Department of Health and Human Services (HHS) and the National Institute on Drug Abuse (NIDA) (2) which is a division of the National Institute of Health. In 2009, approximately 8.7% of all individuals in the United States greater than age 12 reported using illicit substances in the month prior to the survey (1). Unfortunately, the peak incidence of use by age generally corresponds with childbearing years for women and abuse of many substances is also associated with risky sexual behaviors that may lead to pregnancy. The rate for illicit drug use in the prior month among pregnant women has been reported to be approximately 4.5% in the United States as compared with 10.6% of nonpregnant respondents (3). There is a range of reported rates from different populations around the world but the variance appears to be more attributable to what has been measured rather than different use prevalence. For example, in the United Kingdom, the incidence of known drug abuse amongst 15 and 39 year olds is 11% (4). In Sao Paolo, Brazil, pregnant teenagers reported to have positive drug testing (hair analyses) in the third trimester 6% (used cocaine, 4% used marijuana, 1.7% used cocaine, and 3% used both drugs) is 6% (5). In South Australia, 3% of pregnant women were identified as substance abusers in a 2-year retrospective review at a single institution including 1.1% with opioid dependence (6). The prevalence of substance abuse can also be estimated using psychiatric diagnostic criteria for substance abuse, which is generally defined as “the self-administration of various drugs or substances that deviate from medically or socially accepted use” (7). Using specific DSM IV criteria, 9% of the US population, or 27 million people, met these criteria in the last year with nearly 70% using alcohol alone. It is not clear how many also were pregnant from this methodology (1). Extrapolating from survey data, it can be conservatively estimated that approximately 225,000 infants could be exposed to illicit substances either in utero or in the immediate postpartum period (8).

The rate of illicit substance abuse among surveyed subjects in recent years in the United States has been relatively stable (Fig. 42-1). Individual substances and how they are administered or mixed with other agents fluctuate with social trends and it is important for anesthesiologists in many centers to keep abreast of these developments in evaluating and treating pregnant women who are using illicit drugs. The most widely used illicit substance in the general population of the United States is marijuana (Fig. 42-2). Of course, it is important to note that legal substances (caffeine, alcohol, and tobacco) are the most commonly used by pregnant women.

A greater prevalence of substance abuse has been weakly associated with younger age, ethnic minority status, urban location, unemployment and less education (3). However, these associations may track more closely with individual substances, particularly illicit substances, whereas an underlying rate of use of some form of substance use is found in nearly all demographics. Susceptibility to substance abuse is multifactorial but there is likely a strong genetic component. Substance abuse, including but not limited to alcohol and opioid abuse, is more prevalent in people with some genetic subtypes (9). The work has implications for both the screening and treatment of pregnant patients.

Substance abuse, in general, is associated with increased risk of obstetric and neonatal complications. These include an increase in preterm birth ([RR] 2.5, 95% confidence interval [CI] 1.6 to 3.8), low birth weight (RR 3.6, CI 2.4 to 5.4), intrauterine growth restriction (RR 3.82, CI 2.4 to 6.1), and placental abruption (RR 2.74, CI 1.1 to 7) (10,11). There may be a lower incidence of preeclampsia of which tobacco use may be a cofounder as it has been independently shown to reduce that complication (12). Patients who are abusing substances or are at risk for abusing substances should ideally receive early antenatal assessment and intervention to eliminate or minimize the exposure.

Substance abuse is also associated with an increased incidence of other medical comorbidities. These include psychiatric disorders (AOR 8.8, 95% CI 6.5 to 11.9), viral (AOR 23.5, 95% CI 8.8 to 62.7) and bacterial (AOR 6.1, 95% CI 3.5 to 10.4) infections, skin diseases (AOR 3.9, 95% CI 2 to 7.8), and trauma and poisoning (AOR 4.2, 95% CI 3.1 to 5.6) (13,14) (Table 42-1). There is also an alarmingly high rate of mortality among those with a history of substance abuse (7.9% of a cohort of 524 pregnant, substance-abusing women in Finland died within 9 years compared with 0.2% of controls) (13).

Patients who are acutely intoxicated may be uncooperative at admission and this has several practical and ethical implications. Important information exchange and establishing trust between patient and health care providers can be compromised, and the validity of obtaining informed consent may be questioned (15). For anesthesiologists, cooperation, including maintaining relative immobility during neuraxial procedures, is a serious limitation in performing these techniques safely and efficiently.

Some commonly abused substances may create symptoms that mimic other medical conditions or complications of pregnancy. The use of stimulants, including cocaine and amphetamines, has been associated with hypertension and proteinuria which may mimic preeclampsia. Seizure activity and mental status changes are associated with the acute intoxication or withdrawal from many substances which may be confused with eclampsia.

Parturients with a history of substance abuse utilize parenteral labor analgesia at a greater rate than nonsubstance-using controls (11), require more frequent analgesic interventions during cesarean delivery with regional anesthesia (6), and
have a higher incidence of inadequate postcesarean analgesia (6). This observed difference is likely multifactorial including both physical and psychological etiologies. Nonpregnant patients with current opioid and cocaine abuse have been reported to have lower pain thresholds compared with historical controls in ice water immersion, which is a commonly used test to delineate population difference in pain experience (16). Because of this difference as well as the complexities in coordinating care, and greater degree of obstetric and neonatal comorbidity, parturients with a history of substance abuse can be expected to consume a disproportional amount of medical resources when admitted for delivery (17).

Confirming a history of substance abuse in a pregnant patient is typically made by a combination of clinical intuition, interview methodology, and laboratory analysis. Depending on the specific substance used, it is not uncommon to deny use when directly questioned; for example, 66% of parturients with subsequent urinalyses positive for cocaine denied using it at admission (18) and almost 60% denied use in a study examining a broader toxicologic screening (19).

In the absence of universal laboratory screening in admitted parturients, it is important to identify historical elements
and behaviors associated with general substance abuse. These include a history of physical or sexual abuse, tobacco use, and lack of prenatal care (20). General clinical signs such as altered mental status, uncooperativeness or combativeness, as well as signs associated with specific substances such as miosis with opioid use or hypertension with stimulants may be the first hints leading to a diagnosis of substance abuse.

There are a variety of published screening methods for detecting substance abuse (21). Short, direct questioning of patients using these instruments can be effective and efficient. The T-ACE (Tolerance, Annoyance, Cut Down, and Eye Opener) (22) and TWEAK (Tolerance, Worried, Eye-openers, Amnesia, and K [C] Cut Down) (23) instruments have been designed to identify alcohol abuse. The 4 P’s (24) and 4 P’s Plus (25) are appropriate questionnaires to use in screening for a wider number of substances and can detect lower levels of use in pregnant women with moderate to excellent sensitivity (81% to 95%) for detection of alcohol or illicit substance use in pregnancy (26). Longer, written questionnaires such as the Substance Abuse Subtle Screening Inventory (SASSI) have been shown to be very sensitive and specific as screening methods but are time consuming and require patient cooperation (27). They may be more valuable in an outpatient setting and have been shown to be particularly valuable in detecting chronic alcohol abuse. It should be noted that the short, direct screening tools, when used alone with their limited sensitivity and specificity, will ultimately fail in detecting a large number of patients who are currently using illicit substances. Ultimately, they need to be paired with physician judgment and laboratory analysis to detect substance use more effectively. How widely laboratory screening is used is institutionally variable and represents independent clinical practices and resource utilization decisions more than established standards.

Substance abuse can be diagnosed by analyzing urine, saliva, sweat, hair, meconium, and other biologic samples, although for the obstetric anesthesiologist, urinalysis is currently the most practical method for making a time-sensitive decision, in an acute care environment (28). The process of screening analysis may involve enzyme, fluorescence polarization, or radioimmunoassay techniques. These techniques are rapid, less expensive than alternatives, and considered to have sufficient sensitivity for clinically relevant substance abuse. Liquid or gas chromatography or mass spectrometry are rarely used for screening but may be used by laboratories to confirm positive results obtained from the screening technique. Individual cutoff values and confirmatory values have been adopted by the Federal Government for workplace screening to minimize false positives (29) (Table 42-2). Urinalysis drug screening batteries vary but a typical panel may include amphetamines, cocaine metabolites, marijuana metabolites, methadone, PCP, propoxyphene, opiates, benzodiazepines, fentanyl, meperidine, and tramadol. It is of clinical importance to recognize the windows of detection for individual substances (29) (Table 42-3).

The cost of urinalysis is nominal; however, it is not common to routinely screen all obstetric patients. The cost effectiveness of screening all obstetric patients, however, could be justified depending on the prevalence of substance abuse in any given patient population. Alternatives to testing urine include testing samples of hair, saliva, sweat, meconium, and the placenta. Most of these alternatives are currently not practical to use in acute decision making in obstetric patients.