M a n a g e m e n t o f P re g n a n t Patients Undergoing G e n e r a l Su r g i c a l Pro c e d u re s Melissa K. Stewart,
MD,
Kyla P. Terhune,
MD*
KEYWORDS Pregnancy Nonobstetric surgery Perioperative care KEY POINTS Physiologic changes during pregnancy span almost every organ system, influencing even laboratory values of pregnant patients, and must be understood in order to optimize perioperative and operative care. Diagnostic modalities are necessary but can have effects on fetuses and should be understood in order to minimize radiation exposure during pregnancy. Most preoperative considerations for pregnant patients are similar to those for nonpregnant patients; however, a basic knowledge of medications and anesthetic considerations is important in order to provide safe care. Surgical patients are surgical patients, whether pregnant or not. Surgical issues must be addressed, and delay of operative care can lead to worsened outcomes, despite gestational status and stage.
INTRODUCTION
Of women of reproductive age, 102.1 per 1000 women are pregnant in the United States at any given time.1 Of those who are pregnant, approximately 0.2% to 0.75% require nonobstetric surgical intervention during pregnancy.2,3 As in the general surgery population, the most common presenting conditions requiring nonobstetric operations during pregnancy are appendicitis and cholecystitis.4 In general, the approach is the same: to address the surgical issue. However, there are a multitude of additional considerations for pregnant patients, one of which is recognizing the importance of multidisciplinary care. As stated in an American Congress of Obstetrics and Gynecology opinion in 2011, the management of a pregnant patient should be multifaceted, involving the coordination of the obstetrician, surgeon, anesthesiologist, and neonatologist, because concerns regarding both the fetus and the mother may require management modification.5
Disclosures: The authors have no financial disclosures. Department of Surgery, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN 37232, USA * Corresponding author. D-4309 MCN, 1161 21st Avenue South, Nashville, TN 37232. E-mail address: [email protected] Surg Clin N Am - (2014) -–http://dx.doi.org/10.1016/j.suc.2014.10.007 0039-6109/14/$ – see front matter Published by Elsevier Inc.
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PHYSIOLOGIC CHANGES IN PREGNANCY
Physiologic changes during pregnancy are numerous and span most organ systems (Fig. 1). By recognizing and understanding these changes, surgeons may optimize
Fig. 1. Physiologic changes during pregnancy by system. BUN, blood urea nitrogen; FRC, functional residual capacity; GFR, glomerular filtration rate; IVC, inferior vena cava; RV, residual volume; TLC, total lung capacity.
Management of Pregnant Patients
perioperative and intraoperative management. Each affected organ system is discussed separately later. Cardiovascular System
With expansion of the gravid uterus and subsequent increased intra-abdominal pressure, the diaphragm is upwardly displaced and rib shape is changed. This change leads to longitudinal rotation and lateral displacement of the heart, which can result in false radiographic findings that suggest cardiomegaly. The heart develops eccentric hypertrophy secondary to increased blood volume. This increased blood volume increases the cardiac output by increasing stroke volume. When combined with concomitant increased heart rate, cardiac output can increase by 30% to 50% in pregnant patients, peaking at 25 to 30 weeks’ gestation. Despite this increase in cardiac output, maternal blood pressure is decreased secondary to decreased systemic vascular resistance. In addition, all of these balanced dynamics can be markedly affected by positional changes, most of which can be accounted for by inferior vena cava compression by the gravid uterus.6,7 Respiratory Changes
As in most systems, the respiratory effects are a combination of hormonal and mechanical changes. Increased estrogen causes the mucosa of the nasopharynx to become edematous and hyperemic, leading to both hypersecretion and an increased likelihood of spontaneous or induced epistaxis. Relaxation of the cartilaginous attachments between the ribs and sternum, as well as mechanical pressure from the gravid uterus, leads to structural changes of the thoracic cavity, including an increase in subcostal angle, increased chest diameter, and rise in the diaphragm. These changes result in decreased total lung capacity, decreased functional residual capacity, and decreased residual volume. In addition, secondary to progesterone, an increased respiratory rate occurs. Combined with decreased capacities and volumes, this results in increased alveolar ventilation and a chronic respiratory alkalosis.6,7 Hematologic Changes
Changes in maternal blood volume begin to occur as early as the first month of pregnancy. Throughout the pregnancy, blood volume increases progressively, expanding by 40% to 50%, until about 30 to 34 weeks’ gestation. Erythrocyte mass also increases by approximately 30%. The differential increase in blood volume versus erythrocyte mass leads to an overall net decrease in hematocrit; a condition that is called physiologic anemia of pregnancy. The white blood cell count also progressively increases. The cause of this leukocytosis is unclear but may be related to increased cortisol and estrogen levels. Moreover, because of relative venous stasis secondary to compression of the inferior vena cava and concomitant hypercoagulability secondary to an increase in procoagulants, a state thought to be protective against peripartum hemorrhage, pregnancy results in a 5-fold to 6-fold increased risk of thromboembolic events.6,7 Gastrointestinal Changes
Secondary to relaxant effects of estrogen and progesterone on smooth muscle, the tone and the motility of the esophagus and stomach are decreased. This change, in conjunction with mechanical gastric compression from an enlarged uterus, leads to a marked increase in gastroesophageal reflux during pregnancy. Approximately 30% to 50% of pregnant women report having dyspepsia and reflux. In addition, 30% to 40% complain of changes in bowel habits, ranging from constipation to
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diarrhea. Similar to the alimentary tract, the gallbladder is affected by hormoneinduced changes. Such changes lead to decreased ejection fraction and increased biliary cholesterol saturation, making biliary sludge and stones more likely.6,7 Renal/Urinary Changes
The kidney and renal collection system increase in size during pregnancy with dilatation of the renal pelvis, calyces, and ureters. Renal plasma flow and, subsequently, glomerular filtration rate are markedly increased during pregnancy; nearly 50% within the first trimester alone. This hyperfiltration leads to a physiologic decrease in serum creatinine level, blood urea nitrogen level, and uric acid concentration. Other anatomic changes include increase in the bladder trigone and potentially increased vascular tortuosity resulting in increased microhematuria. Also of note, secondary to outward pressure by the expanding uterus, bladder capacitance decreases over time, resulting in urinary frequency, urgency, and incontinence.6,7 PREOPERATIVE EVALUATION
A principle that underpins the work-up of a patient was aptly stated by Sir Zachary Cope: “Earlier diagnosis means better prognosis.”8 This mantra holds true especially in pregnancy, in relation to both the prognosis of the mother and fetus. For example, 36% of women with perforated appendicitis, which can often be attributed to delayed diagnosis, experience fetal loss, compared with 1.5% to 9% in those with nonperforated appendicitis.9 Although the evaluation of pregnant patients carries a unique set of dilemmas, the work-up should be initiated in the same manner as that of nonpregnant patients, beginning with a detailed history and physical examination. In the physical examination, the clinician must consider that the organ in question, such as the appendix, may be significantly displaced secondary to the gravid uterus. Subsequently, the clinician must carefully consider the use of adjunctive diagnostic modalities, because effects on both the patient and fetus must be considered. Evaluation by both laboratory and radiographic techniques, with accompanying description of the modality and specific risks/benefits, are described later. Biochemical Evaluation
Based on the anatomic and physiologic changes described earlier, altered laboratory values may be seen in pregnant patients compared with normal values.10 A summarization of these changes is shown in Table 1.11 Imaging Techniques Computed tomography
Computed tomography (CT) uses ionizing radiation: high-energy photons capable of damaging DNA and generating caustic free radicals (summarized in Table 2).12 Given this, fetal exposure carries potential risks of gene mutations, which could lead to teratogenesis or malignancy. Although causality has been established in the literature, the risk remains small. Most usual diagnostic examinations used in the work-up of general surgical patients (ie, CT abdomen, CT pelvis, and CT pyelogram) are all below the proposed maximum radiation level.13 As stated by the American College of Radiology, “No single diagnostic procedure results in a radiation dose that threatens the well-being of the developing embryo and fetus.”12 Note that the effect is cumulative, and the recommended level of exposure to the fetus should not exceed 5 rad.14
Management of Pregnant Patients
Table 1 Summary of expected laboratory values during pregnancy across trimesters Nonpregnant
First Trimester
Second Trimester
Third Trimester
Hemoglobin (g/dL)
12.0–15.8
11.6–13.9
9.7–14.8
9.5–15.0
Hematocrit (%)
35.4–44.4
31.0–41.0
30.0–39.0
28.0–40.0
Platelet (109/L)
165–415
174–391
155–409
146–429
White blood cell count (103/mm3)
3.5–9.1
5.7–13.6
5.6–14.8
5.9–16.9
Prothrombin time (s)
12.7–15.4
9.7–13.5
9.5–13.4
9.6–12.9
International Normalized Ratio
0.9–1.04
0.85–1.08
0.83–1.02
0,80–1.09
Partial thromboplastin time (s)
26.3–39.4
23–38.9
22.9–38.1
22.6–35.0
Complete Blood Count
Coagulation Profile
Complete Metabolic Panel Sodium (mEq/L)
136–146
133–148
129–148
130–148
Potassium (mEq/L)
3.5–5.0
3.6–5.0
3.3–5.0
3.3–5.1
Chloride (mEq/L)
102–109
101–105
97–109
97–109
Bicarbonate (mmol/L)
22–30
20–24
20–24
20–24
Urea nitrogen (mg/dL)
7–20
7–12
3–13
3–11
Creatinine (mg/dL)
0.5–0.9
0.4–0.7
0.4–0.8
0.4–0.9
Alanine transaminase (U/L)
7–41
3–30
2–33
2–25
Aspartate transaminase (U/L)
12–38
2023
3–33
4–32
Bilirubin, total (mg/dL)
0.3–4.8
0–4.9
0–9.1
0–11.3
Bilirubin, unconjugated (mg/dL)
0.2–0.9
0.1–0.5
0.1–0.4
0.1–0.5
Bilirubin, conjugated (mg/dL)
0.1–0.4
0–0.1
0–9.1
0–0.1
Alkaline phosphatase (U/L)
33–96
17–88
25–126
38–229
Amylase (U/L)
20–96
24–83
16–73
15–81
Lipase (U/L)
3–43
21–76
26–100
41–112
Magnesium (mg/dL)
1.5–2.3
1.6–2.2
1.5–2.2
1.1–2.2
Phosphate (mg/dL)
2.4–4.3
3.1–4.6
2.5–4.6
2.8–4.6
Data from Cunningham F. Normal reference ranges for laboratory values in pregnancy. In: Post TW, editor. UpToDate; 2014. [cited August 1, 2014].
Ultrasonography
Sound waves, not ionizing radiation, are used in ultrasonography. These waves are generally thought to be safe to the fetus. Although no documentation of adverse fetal effects from diagnostic ultrasonography procedures exists, the US Food and Drug Administration recommends limiting ultrasonography energy exposure to
Table 2 Summary of imaging modalities Modality
Risk
Potential Effects
Limit
Radiograph, fluoroscopy, CT
Ionizing radiation
Gene mutation
Teratogenesis, malignancy
5 rad
Ultrasonography
Sound waves
—
—
94 mW/cm2
MRI
Magnetic energy
Acoustic noise, heat
—
—
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94 mW/cm2.15 Because of the improved safety profile of ultrasonography, it has gained popularity and largely replaced radiographic diagnostic modalities using ionizing radiation.16 However, it is limited by body habitus and can be highly operator dependent. Hence, reliability and precision may be decreased. For example, in multiple studies analyzing identification of acute appendicitis during pregnancy with the use of ultrasonography, sensitivities ranged from 50% to 100% and specificity from 96% to 100%.17–19 These values are markedly less than the nearly 98% sensitivity, specificity, and diagnostic accuracy of CT and MRI.20,21 MRI
Like ultrasonography, MRI provides a nonionizing radiation imaging alternative. MRI uses magnetic energy to alter the state of hydrogen protons.16 Although it is postulated that the acoustic noise and heat produced may be detrimental to a developing fetus, no specific adverse fetal effects of MRI have been reported.22,23 Although fetal effects have yet to be elucidated, intravenous gadolinium agents, which are used to increase definition in certain MRI studies, can cross the placenta.24 Because of this and the potential risk of nephrogenic systemic fibrosis, its use is not recommended in pregnant patients.25 Cholangiography: intraoperative and endoscopic retrograde cholangiopancreatography
The potential ill effects of cholangiography are secondary to radiation exposure. Typical intraoperative cholangiography exposure is estimated to be between 0.2 and 0.5 rad/s.26 It is recommended that the fetus be shielded by placing a protective barrier between the patient and the radiation source. In fluoroscopy, this radiation source is generally beneath the operating table, necessitating the placement of lead directly on the table and the patient on the lead. This placement is not instinctive because the tendency is to cover the patient with lead, which would provide no protection. Other methods of protection should also be used. Rather than using so-called live fluoroscopy, clinicians could inject the contrast agent and obtain a single completion cholangiogram, thus minimizing radiation exposure. Endoscopic retrograde cholangiopancreatography (ERCP) radiation exposure can be significantly higher than that of intraoperative cholangiography, averaging between 2 and 12 rad/s.27 Moreover, ERCP carries the additional risks of bleeding and pancreatitis. In summary, the same potential diagnostic studies are available to pregnant patients and should be used when necessary. When deciding on a modality, clinicians must consider the risks and benefits. The risk of a missed or incorrect diagnosis almost always outweighs the risk of any of the aforementioned studies. It is of utmost importance that physicians communicate said risks to their patients, allowing an active, informed conversation and joint decision making. PATIENT SELECTION/PREOPERATIVE PREPARATION
If a condition requiring surgical intervention is diagnosed, such as appendicitis or cholecystitis, an urgent operation should be performed regardless of the trimester. In contrast, if a condition is deemed elective, it should be scheduled for after delivery, when the impact to the fetus is no longer a concern. This timing confers the added advantage of maternal physiology returning to normalcy. If a condition is deemed necessary but semielective, the second trimester is considered the safest time.5 This recommendation stems from a multitude of available data. During the second trimester, after organ system differentiation has occurred, the risk for anestheticinduced malformation or spontaneous abortion declines significantly.28 Although the
Management of Pregnant Patients
differential between first and second trimesters is genetically based, the preference for second versus third trimester is mechanically based. In the second trimester, the uterus size does not greatly crowd the abdominal operative domain. Moreover, the risk of preterm labor is lower during the second trimester.4 Specific preoperative considerations include the following. Fasting Guidelines/Aspiration Precautions
Based on guidelines presented by the American Society of Anesthesiologist Task Force on Obstetric Anesthesia in 2007, the fasting guidelines for pregnant patients mimic the guidelines set forth for standard adults. Recommendations suggest abstaining from solids for at least 6 hours before surgery and from clear liquids for at least 2 hours before surgery.29 Although it is known that the incidence of gastroesophageal reflux is increased in pregnancy, no specific intervention has been shown to improve clinical outcomes with regard to aspiration prevention. However, most providers practice rapid sequence intubation to minimize the risk of aspiration.30 Thromboprophylaxis
As described earlier, the risk of thromboembolic events is markedly increased during pregnancy. The American College of Chest Physicians recommends mechanical and/ or pharmacologic thromboprophylaxis for all pregnant patients undergoing an operation. Low-molecular-weight heparin is the recommended modality and is a safe drug choice during pregnancy. Early mobilization should be encouraged, and prophylaxis should be continued until the patient is mobilized postoperatively.31 Antibiotic Prophylaxis
The need for antibiotic prophylaxis during pregnancy depends on the specific operative procedure and is similar to the guidelines set forth for standard surgical patients. In generic terms, penicillins, cephalosporins, azithromycin, clindamycin, and erythromycin have good safety profiles. However, there are some classes of antibiotics to avoid. Aminoglycosides carry a risk of fetal and maternal ototoxicity and nephrotoxicity. Tetracyclines have been associated with suppression of bone growth and staining of developing teeth in fetuses. Fluoroquinolones are known to have toxic effects on developing cartilage. Given the possible toxicities described earlier, before antibiotic prescription, the specific safety profile must be explored and understood, and pharmacologic consultation obtained if needed.28 Preterm Labor Prophylaxis: Glucocorticoids and Tocolytics
Preterm labor risk in the perioperative period is notably increased. If preterm birth is anticipated or deemed a high risk, and the fetus is deemed potentially viable, prophylaxis with glucocorticoids should be considered. If preterm labor occurs, administration of glucocorticoids 24 to 48 hours before surgery markedly reduces perinatal morbidity and mortality. However, antenatal glucocorticoids may impair the maternal immune response to the underlying disorder. Consultation should be obtained from an obstetrics service to help project the risk of preterm birth. Prophylactic use of tocolytic agents has not proved to be beneficial.32–36 From a physical standpoint, minimizing uterine manipulation may reduce the risk of uterine contraction and subsequent preterm labor.37,38 ANESTHESIA
Plausible risks of anesthesia to fetuses include direct teratogenic effects of medications and anesthetic agents, decreased uteroplacental blood flow secondary to
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changing maternal physiology, and preterm labor. Although this list is not complete, basic anesthetic considerations are discussed later. Positioning
Secondary to possible hemodynamic consequences of vena cava compression from an enlarged uterus, it is recommended that pregnant patients be positioned with a 15% left lateral tilt when possible.28,39,40 Fetal Heart Rate Monitoring
Coordinating obstetricians and neonatologists can be helpful in determining the need and technique for fetal monitoring. The American College of Obstetricians and Gynecologists has stated that the decision to use intermittent or continuous intraoperative fetal monitoring should be based on the type of surgery, available resources, and gestational age. During the first and early second trimester, fetal heart tones are typically monitored before and after anesthesia exposure and operative intervention, but not during the case. During the late second and third trimester, secondary to the viability of the fetus, continuous intraoperative fetal monitoring via transabdominal ultrasonography is generally used. If the surgical field involves the abdomen, transvaginal ultrasonography can be used.16 Despite this recommendation, multiple studies have shown that it is likely unnecessary to use continuous monitoring, because the risk of ill effect and/or the need for intervention is minimal.28,41 Type of Anesthetic
Decisions regarding the type of anesthetic to be used should involve consideration of the planned intervention, the projected risk of maternal physiologic changes, and the predicted teratogenesis. Despite this recommendation, no studies exist that show a significant difference in outcomes. Choices and considerations based on our physiologic understanding of the effects are listed here: Monitored anesthesia care
Monitored anesthesia care (MAC) involves intermittent administration of analgesics and anxiolytics, combined with continuous monitoring of the patient. Much of the concern surrounding the use of MAC during pregnancy is derived from the possibility of induced hypoventilation with subsequent acidosis and decreased placental circulation. The risk of aspiration secondary to positioning and induced smooth muscle relaxation may also be increased.42 However, because most operations completed during pregnancy are intra-abdominal, the use of MAC is generally not an option. Regional anesthesia
Regional anesthesia via peripheral nerve and neuroaxial blocks is considered safe during pregnancy. Such blocks are particularly useful and encouraged during extremity operations. Moreover, neuroaxial blocks may be used for surgery of the lower abdomen, pelvis, and lower extremities. If neuroaxial blocks are used, the provider must be cautious of the potential for induced maternal hypotension from a sympathetic block. Systemic hypotension can lead to reduction in placental perfusion and subsequent fetal compromise.42 General anesthesia
As noted earlier, most operations performed during pregnancy involve laparoscopy or laparotomy, thus requiring general anesthesia. Anesthesia induction involves preoxygenation, medication administration (anesthesia/analgesia/paralytic), and intubation. Preoxygenation is vital in pregnant patients, because hypoxia can lead to
Management of Pregnant Patients
compromised placental blood flow. Per the physiologic discussion earlier, pregnant patients have less reserve and can desaturate in less time than nonpregnant women.43 Once preoxygenation is complete, propofol is generally used as the induction agent of choice, although no induction agent has been shown to be teratogenic. Hemodynamic effects of induction must be anticipated and mitigated in order to maintain placental blood flow.28 For muscle relaxation, nondepolarizing neuromuscular blocking agents are thought to be safe, because they do not cross the placenta. Succinylcholine is the medication most often used, because it facilitates rapid sequence intubation (RSI).28 Despite these general practices, no data have shown differences in outcomes secondary to RSI.44 Hemodynamic and Fluid Management
In pregnant and nonpregnant patients alike, the goal is to maintain perfusion and oxygenation of vital organs. During pregnancy, vital organs also include the uterus and placenta. Much of the effect of medications on the fetus is not a direct effect but is secondary to an effect on maternal physiology and subsequent uterine perfusion.45,46 The effect is further compounded because uterine circulation is not autoregulated in the same manner as circulation to other vital organs. Thus, vasopressors may have little or no direct effect on uterine circulation. Physical maneuvers, such as fluid bolus, Trendelenburg position, compression stockings, and leg elevation, may have larger impacts on increasing uterine blood flow.28 Mechanical Ventilation
Both hyperventilation and hypoventilation can have detrimental effects, so clinicians must be vigilant with pregnant women under general anesthesia. As discussed earlier, pregnancy is associated with a chronic respiratory alkalosis secondary to increased alveolar ventilation. Higher levels of carbon dioxide in hypoventilation may lead to an increased gradient across the placenta and cause acidosis and myocardial depression of the fetus. In contrast, hyperventilation may lead to severe alkalosis and compromise of fetal blood flow and oxygenation.47–50 Thus, mechanical ventilation during anesthesia should maintain the normal physiologic respiratory alkalosis when breathing spontaneously rather than attempt to correct it to usual normal parameters. SURGICAL APPROACH
Once a diagnosis is confirmed and the decision to operate is made, the surgical approach is based on the disorder, surgical skill, and the availability of equipment and staff. When plausible, the benefits of laparoscopy in pregnancy seem to mimic the benefits seen in nonpregnant patients, including decreased postoperative pain and narcotic use, decreased rate of postoperative ileus, decreased length of hospital stay, and quicker return to work.51–55 Laparoscopy Initial port placement
Given the concern for possible uterine or fetal injury, laparoscopic abdominal access in pregnant patients has been debated in the literature. Because the intra-abdominal domain is significantly altered during the second and third trimesters, access via a subcostal approach has been advocated. If the site of initial access is adjusted based on consideration of fundal height, the Hasson technique, Veress needle, and optical trocar all seem to provide safe entry options.37,41,56–58 Surgeons should assess their
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own comfort levels with these approaches and proceed with the safest means possible. Carbon dioxide insufflation
The concern regarding carbon dioxide insufflation in pregnant patients stems from the potential for respiratory compromise secondary to diaphragm displacement and the possibility of peritoneal absorption of carbon dioxide. A pressure of 15 mm Hg is typically used in nonpregnant patients and has been routinely used without increasing adverse maternal/fetal outcomes.3,41,56 With regard to carbon dioxide exchange and possible fetal acidosis, no data exist showing detrimental effects to the fetus.4 As noted earlier, clinicians should consider monitoring in the situation of a viable fetus, and this may provide some guidance with regard to intraoperative effects. Open Approach
If an open approach is chosen, the type of incision depends on the surgical procedure and gestational age. A vertical incision is used for ease of incisional extension if needed to facilitate exposure. POSTOPERATIVE PAIN MANAGEMENT
Pain control in the postoperative period is also important. Nonsteroidal antiinflammatory drugs should not be used in pregnancy because of the risk for premature closure of the ductus arteriosis.28,59 Therefore, opioids, intravenous and oral, are the pain medications of choice. If intravenous opioids must be used, a patient-controlled analgesia pump may be the best initial option, given its low associated risk of maternal respiratory depression. As in all patients, intravenous pain medications should be converted to oral forms as soon as possible. It is recommended that patients be weaned off all narcotics as soon as possible to avoid fetal dependence. Babies born with opioid dependency can manifest decreased birth weight, respiratory depression, and extreme drowsiness, which can lead to feeding problems.28 However, this consideration should not deter the surgeon from providing adequate perioperative pain control for pregnant women. OUTCOMES/SUMMARY
The goals of treating pregnant patients in the perioperative setting are the same as with any patient: to provide safe preoperative, operative, and postoperative care. This task is complicated by the need to consider the well-being of both of the mother and the fetus. Moreover, the primary patient, the mother, has altered physiology. Surgeons must be aware of the physiologic and anatomic changes of pregnancy and recognize the surgical and anesthetic modifications necessary for safe care. Providers can be encouraged that surgical outcomes in pregnant patients have been shown to be similar to those of nonpregnant patients. A review article published in 2005 based on studies from 1966 to 2001 (the largest available) reveals that the overall rate of miscarriage in pregnant women exposed to surgical intervention in the first trimester is 10.5%, which is similar to the rate of miscarriage in the general obstetric population. Moreover, the overall rate of birth defects (approximately 2%) was not significantly increased compared with the general obstetric population. The aforementioned study also quantified the risk of delivery related to surgery (3.5%) and the risk of fetal loss (0.8%–2.5%).60 It is also important to note, as validated in a study of 720,000 patients, that specific types of anesthesia or surgical procedures were not associated with different outcomes. The rates of stillbirths and congenital malformations were similar
Management of Pregnant Patients
in pregnant women who underwent operations during pregnancy compared with pregnant women who did not. The only significant differences were increased rates of low birth weight infants and early neonatal death, with relative risks of 2.0 and 2.1 respectively. Even in these situations, it is difficult to determine whether these findings were secondary to the procedures or to the disorders.2 In conclusion, surgical diseases arise in pregnant and nonpregnant patients alike. Delayed diagnosis and management, secondary to avoidance of fetal risk of diagnostic or therapeutic interventions, pose a greater risk to the mother and fetus than radiation, anesthesia, or operative intervention. REFERENCES
1. Curtin SC, Abma JC, Ventura SJ, et al. Pregnancy rates for U.S. women continue to drop. NCHS Data Brief 2013;(136):1–8. 2. Mazze RI, Kallen B. Reproductive outcome after anesthesia and operation during pregnancy: a registry study of 5405 cases. Am J Obstet Gynecol 1989;161(5): 1178–85. 3. Soper NJ. SAGES’ guidelines for diagnosis, treatment, and use of laparoscopy for surgical problems during pregnancy. Surg Endosc 2011;25(11):3477–8. 4. Fatum M, Rojansky N. Laparoscopic surgery during pregnancy. Obstet Gynecol Surv 2001;56(1):50–9. 5. ACOG Committee on Obstetric Practice. ACOG committee opinion no. 474: Nonobstetric surgery during pregnancy. Obstet Gynecol 2011;117(2 Pt 1):420–1. 6. Chesnutt AN. Physiology of normal pregnancy. Crit Care Clin 2004;20(4):609–15. 7. Gabbe SG, Niebyl JR, Galan HL, et al. Obstetrics: normal and problem pregnancies. Elsevier Health Sciences; 2012. 8. Cope Z, Silen W. Cope’s early diagnosis of the acute abdomen. Oxford University Press; 1983. 9. Hee P, Viktrup L. The diagnosis of appendicitis during pregnancy and maternal and fetal outcome after appendectomy. Int J Gynaecol Obstet 1999;65(2):129–35. 10. Larsson A, Palm M, Hansson LO, et al. Reference values for clinical chemistry tests during normal pregnancy. BJOG 2008;115(7):874–81. 11. Cunningham F. Normal reference ranges for laboratory values in pregnancy. In: Post TW, editor. UpToDate; 2014 [cited August 1, 2014]. 12. Hall EJ. Scientific view of low-level radiation risks. Radiographics 1991;11(3): 509–18. 13. Toppenberg KS, Hill DA, Miller DP. Safety of radiographic imaging during pregnancy. Am Fam Physician 1999;59(7):1813–8, 1820. 14. Karam PA. Determining and reporting fetal radiation exposure from diagnostic radiation. Health Phys 2000;79(5 Suppl):S85–90. 15. Barnett SB. Routine ultrasound scanning in first trimester: what are the risks? Semin Ultrasound CT MR 2002;23(5):387–91. 16. ACOG Committee on Obstetric Practice. ACOG committee opinion. Number 299, September 2004 (replaces no. 158, September 1995). Guidelines for diagnostic imaging during pregnancy. Obstet Gynecol 2004;104(3):647–51. 17. Lim HK, Bae SH, Seo GS. Diagnosis of acute appendicitis in pregnant women: value of sonography. AJR Am J Roentgenol 1992;159(3):539–42. 18. Israel GM, Malguria N, McCarthy S, et al. MRI vs. ultrasound for suspected appendicitis during pregnancy. J Magn Reson Imaging 2008;28(2):428–33. 19. Khandelwal A, Fasih N, Kielar A. Imaging of acute abdomen in pregnancy. Radiol Clin North Am 2013;51(6):1005–22.
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20. Ames Castro M, Shipp TD, Castro EE, et al. The use of helical computed tomography in pregnancy for the diagnosis of acute appendicitis. Am J Obstet Gynecol 2001;184(5):954–7. 21. Rao PM, Rhea JT, Novelline RA, et al. Effect of computed tomography of the appendix on treatment of patients and use of hospital resources. N Engl J Med 1998;338(3):141–6. 22. Patel SJ, Reede DL, Katz DS, et al. Imaging the pregnant patient for nonobstetric conditions: algorithms and radiation dose considerations. Radiographics 2007; 27(6):1705–22. 23. De Wilde JP, Rivers AW, Price DL. A review of the current use of magnetic resonance imaging in pregnancy and safety implications for the fetus. Prog Biophys Mol Biol 2005;87(2–3):335–53. 24. Birchard KR, Brown MA, Hyslop WB, et al. MRI of acute abdominal and pelvic pain in pregnant patients. AJR Am J Roentgenol 2005;184(2):452–8. 25. Media, ACoRCoDaC. ACR manual on contrast media. Reston (VA): American College of Radiology; 2013. 26. Karthikesalingam A, Markar SR, Weerakkody R, et al. Radiation exposure during laparoscopic cholecystectomy with routine intraoperative cholangiography. Surg Endosc 2009;23(8):1845–8. 27. Jorgensen JE, Rubenstein JH, Goodsitt MM, et al. Radiation doses to ERCP patients are significantly lower with experienced endoscopists. Gastrointest Endosc 2010;72(1):58–65. 28. Sabiston DC, Townsend CM, Beauchamp RD, et al. Sabiston textbook of surgery: the biological basis of modern surgical practice. Elsevier Saunders; 2012. 29. American Society of Anesthesiologists Task Force on Obstetric Anesthesia. Practice guidelines for obstetric anesthesia: an updated report by the American Society of Anesthesiologists Task Force on Obstetric Anesthesia. Anesthesiology 2007;106(4):843–63. 30. Paranjothy S, Griffiths JD, Broughton HK, et al. Interventions at caesarean section for reducing the risk of aspiration pneumonitis. Cochrane Database Syst Rev 2010;(1):CD004943. 31. Guyatt GH, Akl EA, Crowther M, et al. Executive summary: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012;141(2 Suppl):7s–47s. 32. Roberts D, Dalziel S. Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. Cochrane Database Syst Rev 2006;(3):CD004454. 33. Katz VL, Farmer RM. Controversies in tocolytic therapy. Clin Obstet Gynecol 1999;42(4):802–19. 34. Berkman ND, Thorp JM Jr, Lohr KN, et al. Tocolytic treatment for the management of preterm labor: a review of the evidence. Am J Obstet Gynecol 2003;188(6): 1648–59. 35. Tan TC, Devendra K, Tan LK, et al. Tocolytic treatment for the management of preterm labour: a systematic review. Singapore Med J 2006;47(5):361–6. 36. Romero R, Sibai BM, Sanchez-Ramos L, et al. An oxytocin receptor antagonist (atosiban) in the treatment of preterm labor: a randomized, double-blind, placebo-controlled trial with tocolytic rescue. Am J Obstet Gynecol 2000;182(5): 1173–83. 37. Soriano D, Yefet Y, Seidman DS, et al. Laparoscopy versus laparotomy in the management of adnexal masses during pregnancy. Fertil Steril 1999;71(5): 955–60.
Management of Pregnant Patients
38. Curet MJ. Special problems in laparoscopic surgery. Previous abdominal surgery, obesity, and pregnancy. Surg Clin North Am 2000;80(4):1093–110. 39. Clark SL, Cotton DB, Pivarnik JM, et al. Position change and central hemodynamic profile during normal third-trimester pregnancy and post partum. Am J Obstet Gynecol 1991;164(3):883–7. 40. Elkayam U, Gleicher N. Cardiac problems in pregnancy: diagnosis and management of maternal and fetal heart disease. Wiley; 1998. 41. Rollins MD, Chan KJ, Price RR. Laparoscopy for appendicitis and cholelithiasis during pregnancy: a new standard of care. Surg Endosc 2004;18(2):237–41. 42. Reitman E, Flood P. Anaesthetic considerations for non-obstetric surgery during pregnancy. Br J Anaesth 2011;107(Suppl 1):i72–8. 43. Baraka AS, Hanna MT, Jabbour SI, et al. Preoxygenation of pregnant and nonpregnant women in the head-up versus supine position. Anesth Analg 1992;75(5):757–9. 44. Neilipovitz DT, Crosby ET. No evidence for decreased incidence of aspiration after rapid sequence induction. Can J Anaesth 2007;54(9):748–64. 45. Alon E, Ball RH, Gillie MH, et al. Effects of propofol and thiopental on maternal and fetal cardiovascular and acid-base variables in the pregnant ewe. Anesthesiology 1993;78(3):562–76. 46. Okutomi T, Whittington RA, Stein DJ, et al. Comparison of the effects of sevoflurane and isoflurane anesthesia on the maternal-fetal unit in sheep. J Anesth 2009; 23(3):392–8. 47. Haruta M, Funato T, Naka Y, et al. Effects of maternal hyperventilation and oxygen inhalation during labor on fetal blood-gas status. Nihon Sanka Fujinka Gakkai Zasshi 1988;40(9):1377–84 [in Japanese]. 48. Muller G, Huber JC, Salzer H, et al. Maternal hyperventilation as a possible cause of fetal tachycardia sub partu. A clinical and experimental study. Gynecol Obstet Invest 1984;17(5):270–5. 49. Hohimer AR, Bissonnette JM, Metcalfe J, et al. Effect of exercise on uterine blood flow in the pregnant Pygmy goat. Am J Physiol 1984;246(2 Pt 2):H207–12. 50. Levinson G, Shnider SM, DeLorimier AA, et al. Effects of maternal hyperventilation on uterine blood flow and fetal oxygenation and acid-base status. Anesthesiology 1974;40(4):340–7. 51. Reedy MB, Galan HL, Richards WE, et al. Laparoscopy during pregnancy. A survey of laparoendoscopic surgeons. J Reprod Med 1997;42(1):33–8. 52. Al-Fozan H, Tulandi T. Safety and risks of laparoscopy in pregnancy. Curr Opin Obstet Gynecol 2002;14(4):375–9. 53. Shay DC, Bhavani-Shankar K, Datta S. Laparoscopic surgery during pregnancy. Anesthesiol Clin North America 2001;19(1):57–67. 54. Oelsner G, Stockheim D, Soriano D, et al. Pregnancy outcome after laparoscopy or laparotomy in pregnancy. J Am Assoc Gynecol Laparosc 2003; 10(2):200–4. 55. Andreoli M, Servakov M, Meyers P, et al. Laparoscopic surgery during pregnancy. J Am Assoc Gynecol Laparosc 1999;6(2):229–33. 56. Affleck DG, Handrahan DL, Egger MJ, et al. The laparoscopic management of appendicitis and cholelithiasis during pregnancy. Am J Surg 1999;178(6): 523–9. 57. Geisler JP, Rose SL, Mernitz CS, et al. Non-gynecologic laparoscopy in second and third trimester pregnancy: obstetric implications. JSLS 1998;2(3):235–8. 58. Lemaire BM, van Erp WF. Laparoscopic surgery during pregnancy. Surg Endosc 1997;11(1):15–8.
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59. Schecter WP, Farmer D, Horn JK, et al. Special considerations in perioperative pain management: audiovisual distraction, geriatrics, pediatrics, and pregnancy. J Am Coll Surg 2005;201(4):612–8. 60. Cohen-Kerem R, Railton C, Oren D, et al. Pregnancy outcome following nonobstetric surgical intervention. Am J Surg 2005;190(3):467–73.
MD,
Kyla P. Terhune,
MD*
KEYWORDS Pregnancy Nonobstetric surgery Perioperative care KEY POINTS Physiologic changes during pregnancy span almost every organ system, influencing even laboratory values of pregnant patients, and must be understood in order to optimize perioperative and operative care. Diagnostic modalities are necessary but can have effects on fetuses and should be understood in order to minimize radiation exposure during pregnancy. Most preoperative considerations for pregnant patients are similar to those for nonpregnant patients; however, a basic knowledge of medications and anesthetic considerations is important in order to provide safe care. Surgical patients are surgical patients, whether pregnant or not. Surgical issues must be addressed, and delay of operative care can lead to worsened outcomes, despite gestational status and stage.
INTRODUCTION
Of women of reproductive age, 102.1 per 1000 women are pregnant in the United States at any given time.1 Of those who are pregnant, approximately 0.2% to 0.75% require nonobstetric surgical intervention during pregnancy.2,3 As in the general surgery population, the most common presenting conditions requiring nonobstetric operations during pregnancy are appendicitis and cholecystitis.4 In general, the approach is the same: to address the surgical issue. However, there are a multitude of additional considerations for pregnant patients, one of which is recognizing the importance of multidisciplinary care. As stated in an American Congress of Obstetrics and Gynecology opinion in 2011, the management of a pregnant patient should be multifaceted, involving the coordination of the obstetrician, surgeon, anesthesiologist, and neonatologist, because concerns regarding both the fetus and the mother may require management modification.5
Disclosures: The authors have no financial disclosures. Department of Surgery, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN 37232, USA * Corresponding author. D-4309 MCN, 1161 21st Avenue South, Nashville, TN 37232. E-mail address: [email protected] Surg Clin N Am - (2014) -–http://dx.doi.org/10.1016/j.suc.2014.10.007 0039-6109/14/$ – see front matter Published by Elsevier Inc.
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PHYSIOLOGIC CHANGES IN PREGNANCY
Physiologic changes during pregnancy are numerous and span most organ systems (Fig. 1). By recognizing and understanding these changes, surgeons may optimize
Fig. 1. Physiologic changes during pregnancy by system. BUN, blood urea nitrogen; FRC, functional residual capacity; GFR, glomerular filtration rate; IVC, inferior vena cava; RV, residual volume; TLC, total lung capacity.
Management of Pregnant Patients
perioperative and intraoperative management. Each affected organ system is discussed separately later. Cardiovascular System
With expansion of the gravid uterus and subsequent increased intra-abdominal pressure, the diaphragm is upwardly displaced and rib shape is changed. This change leads to longitudinal rotation and lateral displacement of the heart, which can result in false radiographic findings that suggest cardiomegaly. The heart develops eccentric hypertrophy secondary to increased blood volume. This increased blood volume increases the cardiac output by increasing stroke volume. When combined with concomitant increased heart rate, cardiac output can increase by 30% to 50% in pregnant patients, peaking at 25 to 30 weeks’ gestation. Despite this increase in cardiac output, maternal blood pressure is decreased secondary to decreased systemic vascular resistance. In addition, all of these balanced dynamics can be markedly affected by positional changes, most of which can be accounted for by inferior vena cava compression by the gravid uterus.6,7 Respiratory Changes
As in most systems, the respiratory effects are a combination of hormonal and mechanical changes. Increased estrogen causes the mucosa of the nasopharynx to become edematous and hyperemic, leading to both hypersecretion and an increased likelihood of spontaneous or induced epistaxis. Relaxation of the cartilaginous attachments between the ribs and sternum, as well as mechanical pressure from the gravid uterus, leads to structural changes of the thoracic cavity, including an increase in subcostal angle, increased chest diameter, and rise in the diaphragm. These changes result in decreased total lung capacity, decreased functional residual capacity, and decreased residual volume. In addition, secondary to progesterone, an increased respiratory rate occurs. Combined with decreased capacities and volumes, this results in increased alveolar ventilation and a chronic respiratory alkalosis.6,7 Hematologic Changes
Changes in maternal blood volume begin to occur as early as the first month of pregnancy. Throughout the pregnancy, blood volume increases progressively, expanding by 40% to 50%, until about 30 to 34 weeks’ gestation. Erythrocyte mass also increases by approximately 30%. The differential increase in blood volume versus erythrocyte mass leads to an overall net decrease in hematocrit; a condition that is called physiologic anemia of pregnancy. The white blood cell count also progressively increases. The cause of this leukocytosis is unclear but may be related to increased cortisol and estrogen levels. Moreover, because of relative venous stasis secondary to compression of the inferior vena cava and concomitant hypercoagulability secondary to an increase in procoagulants, a state thought to be protective against peripartum hemorrhage, pregnancy results in a 5-fold to 6-fold increased risk of thromboembolic events.6,7 Gastrointestinal Changes
Secondary to relaxant effects of estrogen and progesterone on smooth muscle, the tone and the motility of the esophagus and stomach are decreased. This change, in conjunction with mechanical gastric compression from an enlarged uterus, leads to a marked increase in gastroesophageal reflux during pregnancy. Approximately 30% to 50% of pregnant women report having dyspepsia and reflux. In addition, 30% to 40% complain of changes in bowel habits, ranging from constipation to
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diarrhea. Similar to the alimentary tract, the gallbladder is affected by hormoneinduced changes. Such changes lead to decreased ejection fraction and increased biliary cholesterol saturation, making biliary sludge and stones more likely.6,7 Renal/Urinary Changes
The kidney and renal collection system increase in size during pregnancy with dilatation of the renal pelvis, calyces, and ureters. Renal plasma flow and, subsequently, glomerular filtration rate are markedly increased during pregnancy; nearly 50% within the first trimester alone. This hyperfiltration leads to a physiologic decrease in serum creatinine level, blood urea nitrogen level, and uric acid concentration. Other anatomic changes include increase in the bladder trigone and potentially increased vascular tortuosity resulting in increased microhematuria. Also of note, secondary to outward pressure by the expanding uterus, bladder capacitance decreases over time, resulting in urinary frequency, urgency, and incontinence.6,7 PREOPERATIVE EVALUATION
A principle that underpins the work-up of a patient was aptly stated by Sir Zachary Cope: “Earlier diagnosis means better prognosis.”8 This mantra holds true especially in pregnancy, in relation to both the prognosis of the mother and fetus. For example, 36% of women with perforated appendicitis, which can often be attributed to delayed diagnosis, experience fetal loss, compared with 1.5% to 9% in those with nonperforated appendicitis.9 Although the evaluation of pregnant patients carries a unique set of dilemmas, the work-up should be initiated in the same manner as that of nonpregnant patients, beginning with a detailed history and physical examination. In the physical examination, the clinician must consider that the organ in question, such as the appendix, may be significantly displaced secondary to the gravid uterus. Subsequently, the clinician must carefully consider the use of adjunctive diagnostic modalities, because effects on both the patient and fetus must be considered. Evaluation by both laboratory and radiographic techniques, with accompanying description of the modality and specific risks/benefits, are described later. Biochemical Evaluation
Based on the anatomic and physiologic changes described earlier, altered laboratory values may be seen in pregnant patients compared with normal values.10 A summarization of these changes is shown in Table 1.11 Imaging Techniques Computed tomography
Computed tomography (CT) uses ionizing radiation: high-energy photons capable of damaging DNA and generating caustic free radicals (summarized in Table 2).12 Given this, fetal exposure carries potential risks of gene mutations, which could lead to teratogenesis or malignancy. Although causality has been established in the literature, the risk remains small. Most usual diagnostic examinations used in the work-up of general surgical patients (ie, CT abdomen, CT pelvis, and CT pyelogram) are all below the proposed maximum radiation level.13 As stated by the American College of Radiology, “No single diagnostic procedure results in a radiation dose that threatens the well-being of the developing embryo and fetus.”12 Note that the effect is cumulative, and the recommended level of exposure to the fetus should not exceed 5 rad.14
Management of Pregnant Patients
Table 1 Summary of expected laboratory values during pregnancy across trimesters Nonpregnant
First Trimester
Second Trimester
Third Trimester
Hemoglobin (g/dL)
12.0–15.8
11.6–13.9
9.7–14.8
9.5–15.0
Hematocrit (%)
35.4–44.4
31.0–41.0
30.0–39.0
28.0–40.0
Platelet (109/L)
165–415
174–391
155–409
146–429
White blood cell count (103/mm3)
3.5–9.1
5.7–13.6
5.6–14.8
5.9–16.9
Prothrombin time (s)
12.7–15.4
9.7–13.5
9.5–13.4
9.6–12.9
International Normalized Ratio
0.9–1.04
0.85–1.08
0.83–1.02
0,80–1.09
Partial thromboplastin time (s)
26.3–39.4
23–38.9
22.9–38.1
22.6–35.0
Complete Blood Count
Coagulation Profile
Complete Metabolic Panel Sodium (mEq/L)
136–146
133–148
129–148
130–148
Potassium (mEq/L)
3.5–5.0
3.6–5.0
3.3–5.0
3.3–5.1
Chloride (mEq/L)
102–109
101–105
97–109
97–109
Bicarbonate (mmol/L)
22–30
20–24
20–24
20–24
Urea nitrogen (mg/dL)
7–20
7–12
3–13
3–11
Creatinine (mg/dL)
0.5–0.9
0.4–0.7
0.4–0.8
0.4–0.9
Alanine transaminase (U/L)
7–41
3–30
2–33
2–25
Aspartate transaminase (U/L)
12–38
2023
3–33
4–32
Bilirubin, total (mg/dL)
0.3–4.8
0–4.9
0–9.1
0–11.3
Bilirubin, unconjugated (mg/dL)
0.2–0.9
0.1–0.5
0.1–0.4
0.1–0.5
Bilirubin, conjugated (mg/dL)
0.1–0.4
0–0.1
0–9.1
0–0.1
Alkaline phosphatase (U/L)
33–96
17–88
25–126
38–229
Amylase (U/L)
20–96
24–83
16–73
15–81
Lipase (U/L)
3–43
21–76
26–100
41–112
Magnesium (mg/dL)
1.5–2.3
1.6–2.2
1.5–2.2
1.1–2.2
Phosphate (mg/dL)
2.4–4.3
3.1–4.6
2.5–4.6
2.8–4.6
Data from Cunningham F. Normal reference ranges for laboratory values in pregnancy. In: Post TW, editor. UpToDate; 2014. [cited August 1, 2014].
Ultrasonography
Sound waves, not ionizing radiation, are used in ultrasonography. These waves are generally thought to be safe to the fetus. Although no documentation of adverse fetal effects from diagnostic ultrasonography procedures exists, the US Food and Drug Administration recommends limiting ultrasonography energy exposure to
Table 2 Summary of imaging modalities Modality
Risk
Potential Effects
Limit
Radiograph, fluoroscopy, CT
Ionizing radiation
Gene mutation
Teratogenesis, malignancy
5 rad
Ultrasonography
Sound waves
—
—
94 mW/cm2
MRI
Magnetic energy
Acoustic noise, heat
—
—
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94 mW/cm2.15 Because of the improved safety profile of ultrasonography, it has gained popularity and largely replaced radiographic diagnostic modalities using ionizing radiation.16 However, it is limited by body habitus and can be highly operator dependent. Hence, reliability and precision may be decreased. For example, in multiple studies analyzing identification of acute appendicitis during pregnancy with the use of ultrasonography, sensitivities ranged from 50% to 100% and specificity from 96% to 100%.17–19 These values are markedly less than the nearly 98% sensitivity, specificity, and diagnostic accuracy of CT and MRI.20,21 MRI
Like ultrasonography, MRI provides a nonionizing radiation imaging alternative. MRI uses magnetic energy to alter the state of hydrogen protons.16 Although it is postulated that the acoustic noise and heat produced may be detrimental to a developing fetus, no specific adverse fetal effects of MRI have been reported.22,23 Although fetal effects have yet to be elucidated, intravenous gadolinium agents, which are used to increase definition in certain MRI studies, can cross the placenta.24 Because of this and the potential risk of nephrogenic systemic fibrosis, its use is not recommended in pregnant patients.25 Cholangiography: intraoperative and endoscopic retrograde cholangiopancreatography
The potential ill effects of cholangiography are secondary to radiation exposure. Typical intraoperative cholangiography exposure is estimated to be between 0.2 and 0.5 rad/s.26 It is recommended that the fetus be shielded by placing a protective barrier between the patient and the radiation source. In fluoroscopy, this radiation source is generally beneath the operating table, necessitating the placement of lead directly on the table and the patient on the lead. This placement is not instinctive because the tendency is to cover the patient with lead, which would provide no protection. Other methods of protection should also be used. Rather than using so-called live fluoroscopy, clinicians could inject the contrast agent and obtain a single completion cholangiogram, thus minimizing radiation exposure. Endoscopic retrograde cholangiopancreatography (ERCP) radiation exposure can be significantly higher than that of intraoperative cholangiography, averaging between 2 and 12 rad/s.27 Moreover, ERCP carries the additional risks of bleeding and pancreatitis. In summary, the same potential diagnostic studies are available to pregnant patients and should be used when necessary. When deciding on a modality, clinicians must consider the risks and benefits. The risk of a missed or incorrect diagnosis almost always outweighs the risk of any of the aforementioned studies. It is of utmost importance that physicians communicate said risks to their patients, allowing an active, informed conversation and joint decision making. PATIENT SELECTION/PREOPERATIVE PREPARATION
If a condition requiring surgical intervention is diagnosed, such as appendicitis or cholecystitis, an urgent operation should be performed regardless of the trimester. In contrast, if a condition is deemed elective, it should be scheduled for after delivery, when the impact to the fetus is no longer a concern. This timing confers the added advantage of maternal physiology returning to normalcy. If a condition is deemed necessary but semielective, the second trimester is considered the safest time.5 This recommendation stems from a multitude of available data. During the second trimester, after organ system differentiation has occurred, the risk for anestheticinduced malformation or spontaneous abortion declines significantly.28 Although the
Management of Pregnant Patients
differential between first and second trimesters is genetically based, the preference for second versus third trimester is mechanically based. In the second trimester, the uterus size does not greatly crowd the abdominal operative domain. Moreover, the risk of preterm labor is lower during the second trimester.4 Specific preoperative considerations include the following. Fasting Guidelines/Aspiration Precautions
Based on guidelines presented by the American Society of Anesthesiologist Task Force on Obstetric Anesthesia in 2007, the fasting guidelines for pregnant patients mimic the guidelines set forth for standard adults. Recommendations suggest abstaining from solids for at least 6 hours before surgery and from clear liquids for at least 2 hours before surgery.29 Although it is known that the incidence of gastroesophageal reflux is increased in pregnancy, no specific intervention has been shown to improve clinical outcomes with regard to aspiration prevention. However, most providers practice rapid sequence intubation to minimize the risk of aspiration.30 Thromboprophylaxis
As described earlier, the risk of thromboembolic events is markedly increased during pregnancy. The American College of Chest Physicians recommends mechanical and/ or pharmacologic thromboprophylaxis for all pregnant patients undergoing an operation. Low-molecular-weight heparin is the recommended modality and is a safe drug choice during pregnancy. Early mobilization should be encouraged, and prophylaxis should be continued until the patient is mobilized postoperatively.31 Antibiotic Prophylaxis
The need for antibiotic prophylaxis during pregnancy depends on the specific operative procedure and is similar to the guidelines set forth for standard surgical patients. In generic terms, penicillins, cephalosporins, azithromycin, clindamycin, and erythromycin have good safety profiles. However, there are some classes of antibiotics to avoid. Aminoglycosides carry a risk of fetal and maternal ototoxicity and nephrotoxicity. Tetracyclines have been associated with suppression of bone growth and staining of developing teeth in fetuses. Fluoroquinolones are known to have toxic effects on developing cartilage. Given the possible toxicities described earlier, before antibiotic prescription, the specific safety profile must be explored and understood, and pharmacologic consultation obtained if needed.28 Preterm Labor Prophylaxis: Glucocorticoids and Tocolytics
Preterm labor risk in the perioperative period is notably increased. If preterm birth is anticipated or deemed a high risk, and the fetus is deemed potentially viable, prophylaxis with glucocorticoids should be considered. If preterm labor occurs, administration of glucocorticoids 24 to 48 hours before surgery markedly reduces perinatal morbidity and mortality. However, antenatal glucocorticoids may impair the maternal immune response to the underlying disorder. Consultation should be obtained from an obstetrics service to help project the risk of preterm birth. Prophylactic use of tocolytic agents has not proved to be beneficial.32–36 From a physical standpoint, minimizing uterine manipulation may reduce the risk of uterine contraction and subsequent preterm labor.37,38 ANESTHESIA
Plausible risks of anesthesia to fetuses include direct teratogenic effects of medications and anesthetic agents, decreased uteroplacental blood flow secondary to
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changing maternal physiology, and preterm labor. Although this list is not complete, basic anesthetic considerations are discussed later. Positioning
Secondary to possible hemodynamic consequences of vena cava compression from an enlarged uterus, it is recommended that pregnant patients be positioned with a 15% left lateral tilt when possible.28,39,40 Fetal Heart Rate Monitoring
Coordinating obstetricians and neonatologists can be helpful in determining the need and technique for fetal monitoring. The American College of Obstetricians and Gynecologists has stated that the decision to use intermittent or continuous intraoperative fetal monitoring should be based on the type of surgery, available resources, and gestational age. During the first and early second trimester, fetal heart tones are typically monitored before and after anesthesia exposure and operative intervention, but not during the case. During the late second and third trimester, secondary to the viability of the fetus, continuous intraoperative fetal monitoring via transabdominal ultrasonography is generally used. If the surgical field involves the abdomen, transvaginal ultrasonography can be used.16 Despite this recommendation, multiple studies have shown that it is likely unnecessary to use continuous monitoring, because the risk of ill effect and/or the need for intervention is minimal.28,41 Type of Anesthetic
Decisions regarding the type of anesthetic to be used should involve consideration of the planned intervention, the projected risk of maternal physiologic changes, and the predicted teratogenesis. Despite this recommendation, no studies exist that show a significant difference in outcomes. Choices and considerations based on our physiologic understanding of the effects are listed here: Monitored anesthesia care
Monitored anesthesia care (MAC) involves intermittent administration of analgesics and anxiolytics, combined with continuous monitoring of the patient. Much of the concern surrounding the use of MAC during pregnancy is derived from the possibility of induced hypoventilation with subsequent acidosis and decreased placental circulation. The risk of aspiration secondary to positioning and induced smooth muscle relaxation may also be increased.42 However, because most operations completed during pregnancy are intra-abdominal, the use of MAC is generally not an option. Regional anesthesia
Regional anesthesia via peripheral nerve and neuroaxial blocks is considered safe during pregnancy. Such blocks are particularly useful and encouraged during extremity operations. Moreover, neuroaxial blocks may be used for surgery of the lower abdomen, pelvis, and lower extremities. If neuroaxial blocks are used, the provider must be cautious of the potential for induced maternal hypotension from a sympathetic block. Systemic hypotension can lead to reduction in placental perfusion and subsequent fetal compromise.42 General anesthesia
As noted earlier, most operations performed during pregnancy involve laparoscopy or laparotomy, thus requiring general anesthesia. Anesthesia induction involves preoxygenation, medication administration (anesthesia/analgesia/paralytic), and intubation. Preoxygenation is vital in pregnant patients, because hypoxia can lead to
Management of Pregnant Patients
compromised placental blood flow. Per the physiologic discussion earlier, pregnant patients have less reserve and can desaturate in less time than nonpregnant women.43 Once preoxygenation is complete, propofol is generally used as the induction agent of choice, although no induction agent has been shown to be teratogenic. Hemodynamic effects of induction must be anticipated and mitigated in order to maintain placental blood flow.28 For muscle relaxation, nondepolarizing neuromuscular blocking agents are thought to be safe, because they do not cross the placenta. Succinylcholine is the medication most often used, because it facilitates rapid sequence intubation (RSI).28 Despite these general practices, no data have shown differences in outcomes secondary to RSI.44 Hemodynamic and Fluid Management
In pregnant and nonpregnant patients alike, the goal is to maintain perfusion and oxygenation of vital organs. During pregnancy, vital organs also include the uterus and placenta. Much of the effect of medications on the fetus is not a direct effect but is secondary to an effect on maternal physiology and subsequent uterine perfusion.45,46 The effect is further compounded because uterine circulation is not autoregulated in the same manner as circulation to other vital organs. Thus, vasopressors may have little or no direct effect on uterine circulation. Physical maneuvers, such as fluid bolus, Trendelenburg position, compression stockings, and leg elevation, may have larger impacts on increasing uterine blood flow.28 Mechanical Ventilation
Both hyperventilation and hypoventilation can have detrimental effects, so clinicians must be vigilant with pregnant women under general anesthesia. As discussed earlier, pregnancy is associated with a chronic respiratory alkalosis secondary to increased alveolar ventilation. Higher levels of carbon dioxide in hypoventilation may lead to an increased gradient across the placenta and cause acidosis and myocardial depression of the fetus. In contrast, hyperventilation may lead to severe alkalosis and compromise of fetal blood flow and oxygenation.47–50 Thus, mechanical ventilation during anesthesia should maintain the normal physiologic respiratory alkalosis when breathing spontaneously rather than attempt to correct it to usual normal parameters. SURGICAL APPROACH
Once a diagnosis is confirmed and the decision to operate is made, the surgical approach is based on the disorder, surgical skill, and the availability of equipment and staff. When plausible, the benefits of laparoscopy in pregnancy seem to mimic the benefits seen in nonpregnant patients, including decreased postoperative pain and narcotic use, decreased rate of postoperative ileus, decreased length of hospital stay, and quicker return to work.51–55 Laparoscopy Initial port placement
Given the concern for possible uterine or fetal injury, laparoscopic abdominal access in pregnant patients has been debated in the literature. Because the intra-abdominal domain is significantly altered during the second and third trimesters, access via a subcostal approach has been advocated. If the site of initial access is adjusted based on consideration of fundal height, the Hasson technique, Veress needle, and optical trocar all seem to provide safe entry options.37,41,56–58 Surgeons should assess their
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own comfort levels with these approaches and proceed with the safest means possible. Carbon dioxide insufflation
The concern regarding carbon dioxide insufflation in pregnant patients stems from the potential for respiratory compromise secondary to diaphragm displacement and the possibility of peritoneal absorption of carbon dioxide. A pressure of 15 mm Hg is typically used in nonpregnant patients and has been routinely used without increasing adverse maternal/fetal outcomes.3,41,56 With regard to carbon dioxide exchange and possible fetal acidosis, no data exist showing detrimental effects to the fetus.4 As noted earlier, clinicians should consider monitoring in the situation of a viable fetus, and this may provide some guidance with regard to intraoperative effects. Open Approach
If an open approach is chosen, the type of incision depends on the surgical procedure and gestational age. A vertical incision is used for ease of incisional extension if needed to facilitate exposure. POSTOPERATIVE PAIN MANAGEMENT
Pain control in the postoperative period is also important. Nonsteroidal antiinflammatory drugs should not be used in pregnancy because of the risk for premature closure of the ductus arteriosis.28,59 Therefore, opioids, intravenous and oral, are the pain medications of choice. If intravenous opioids must be used, a patient-controlled analgesia pump may be the best initial option, given its low associated risk of maternal respiratory depression. As in all patients, intravenous pain medications should be converted to oral forms as soon as possible. It is recommended that patients be weaned off all narcotics as soon as possible to avoid fetal dependence. Babies born with opioid dependency can manifest decreased birth weight, respiratory depression, and extreme drowsiness, which can lead to feeding problems.28 However, this consideration should not deter the surgeon from providing adequate perioperative pain control for pregnant women. OUTCOMES/SUMMARY
The goals of treating pregnant patients in the perioperative setting are the same as with any patient: to provide safe preoperative, operative, and postoperative care. This task is complicated by the need to consider the well-being of both of the mother and the fetus. Moreover, the primary patient, the mother, has altered physiology. Surgeons must be aware of the physiologic and anatomic changes of pregnancy and recognize the surgical and anesthetic modifications necessary for safe care. Providers can be encouraged that surgical outcomes in pregnant patients have been shown to be similar to those of nonpregnant patients. A review article published in 2005 based on studies from 1966 to 2001 (the largest available) reveals that the overall rate of miscarriage in pregnant women exposed to surgical intervention in the first trimester is 10.5%, which is similar to the rate of miscarriage in the general obstetric population. Moreover, the overall rate of birth defects (approximately 2%) was not significantly increased compared with the general obstetric population. The aforementioned study also quantified the risk of delivery related to surgery (3.5%) and the risk of fetal loss (0.8%–2.5%).60 It is also important to note, as validated in a study of 720,000 patients, that specific types of anesthesia or surgical procedures were not associated with different outcomes. The rates of stillbirths and congenital malformations were similar
Management of Pregnant Patients
in pregnant women who underwent operations during pregnancy compared with pregnant women who did not. The only significant differences were increased rates of low birth weight infants and early neonatal death, with relative risks of 2.0 and 2.1 respectively. Even in these situations, it is difficult to determine whether these findings were secondary to the procedures or to the disorders.2 In conclusion, surgical diseases arise in pregnant and nonpregnant patients alike. Delayed diagnosis and management, secondary to avoidance of fetal risk of diagnostic or therapeutic interventions, pose a greater risk to the mother and fetus than radiation, anesthesia, or operative intervention. REFERENCES
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