What the Anesthesiologist Should Know before the Operative Procedure

Providing anesthesia for non-obstetric surgery during pregnancy can be anxiety-provoking for all involved. Roughly 2% of women will have surgery during pregnancy, involving about 80,000 anesthetics in the United States. Although statistics are hard to come by, this number is probably increasing with laparoscopic procedures accounting for much of the increase. Most surgeries are performed to treat conditions common to the childbearing age group: trauma, ovarian cysts, appendicitis, cholelithiasis, breast masses and cervical incompetence. However, major procedures such as craniotomy, cardiopulmonary bypass, and liver transplantation may also be necessary in the pregnant patient, and generally result in good outcomes for mother and fetus. The urgency of the surgery must be balanced against the risk of fetal loss. If possible, surgery should be done in the second trimester beyond the main period of miscarriage, organogenesis, and teratogenicity, but before the risk of preterm labor increases.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Emergency surgery should not be delayed because of the pregnancy. For example, the usual guidelines for treating trauma, an open fracture, or appendicitis should be followed. A pregnant woman should never be denied indicated surgery. However if the surgery is less urgent or elective, there are more optimal times during pregnancy to perform surgery and provide anesthesia. During the first trimester, risk of spontaneous abortion and concerns about teratogenicity are highest. Although no anesthetic agents are teratogens, one should avoid exposure of the developing fetus to perioperative risks such as ionizing radiation, maternal hypoxia or hypercapnia, maternal stress and anxiety, metabolic disturbances such as severe hypoglycemia, and extremes of temperature. During the third trimester, preterm labor is more likely to occur. Prevention and treatment of preterm labor is the most difficult problem to overcome perioperatively, and preterm labor is the most common cause of fetal loss. Second trimester may be the optimal time for non-obstetric surgery.

Emergent – Any emergent surgery should be performed immediately to save the mother from morbidity or even mortality.
Urgent – Surgery should proceed once obstetric consultation has been obtained and resources for fetal monitoring have been arranged if deemed necessary.
Elective – Surgery should be postponed until after delivery, or at least until second trimester.
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2. Preoperative evaluation

Most obstetric patients are young, healthy and have few if any co-morbidities. Preoperative obstetric evaluation should include a pregnancy test in women of child-bearing age if the patient requests it or if her last menstrual period was more than 3-4 weeks previously. If the patient refuses pregnancy testing, it is her right to do so, but that should be documented in the chart. An established pregnancy should be evaluated by ultrasound for gestational age and viability of the fetus. If the fetus is pre-viable (<24 weeks gestation), continuous fetal monitoring is rarely indicated. Fetal heart tones can be checked pre- and postoperatively. If there is an intra-uterine fetal demise on ultrasound, that should be documented pre-operatively by the obstetric team. All pregnant patients are treated as though they have a full stomach and are at risk for aspiration. Premedication with some combination of an H2 receptor blocking agent, metoclopramide, and clear antacid should be considered. The obstetrician may also recommend tocolysis if she is at high risk of preterm labor. Tocolytic agents may include indomethacin, magnesium sulfate or calcium channel blocking agents. Evaluations related to trauma or to the surgical condition should not be denied or avoided simply because the patient is pregnant. Shielding can be provided for x-rays or CT scans. If appropriate, MRI and ultrasound are imaging techniques without risk of radiation exposure to mother or fetus.

Medically unstable conditions warranting further evaluation include: In this patient population, medically unstable conditions usually relate to the surgical condition. After basic resuscitation and stabilization, surgical issues should be dealt with in the operating room.
Delaying surgery is rarely indicated. It may require a short delay to obtain evaluation from the obstetrician, to arrange for fetal monitoring if the obstetric team feels that modality is indicated, and to begin tocolysis if the obstetric team has prescribed agents to stop or prevent preterm labor.

3. What are the implications of co-existing disease on perioperative care?

Perioperative evaluation – Obstetric evaluation should include gestational age, viability and growth of the fetus, and recommendations for intermittent or continuous fetal monitoring. Evaluation will include ultrasound evaluation in addition to history and physical examination.
Perioperative risk reduction strategies – Anesthesiologists should be aware of the physiologic changes of pregnancy and how they may impact anesthetic management. Fetal concerns include teratogenesis, preterm delivery, spontaneous abortion, low birth weight, intrauterine growth retardation (IUGR), as well as behavioral effects due to exposure to anesthetic agents. Use of fetal monitoring should be discussed with the obstetrician, and equipment and personnel from the labor and delivery suite should be made available in the preoperative area, operating room, and PACU as needed. If delivery is a potential option during the surgical case, cesarean section instruments and a warmer for the newborn should be brought to the main operating room.

b. Cardiovascular system

Acute/unstable conditions: Cardiovascular changes of pregnancy include increases in plasma volume and cardiac output, and a decrease in peripheral vascular resistance. Because the increase in plasma volume is greater than that of red cell volume, a physiologic anemia of pregnancy develops. The maximum decrease in hemoglobin occurs at about 28 weeks of gestation, and normal hemoglobin at term would be 9.5-15 g/dL or hematocrit 28-40% at sea level. The increase in cardiac output is also maximal at about 28 weeks gestation. It plateaus during the third trimester, then increases abruptly immediately postpartum when aortocaval compression is released and blood is auto-transfused from the uterus and placenta. After 20-24 weeks gestation, women are at risk for aortocaval compression when lying in the supine position. Only about 10% will be symptomatic with the “supine hypotensive syndrome” of dizziness, nausea, and dysphoria, but all women will have occult hemodynamic changes that can affect uterine perfusion. The uterus should be displaced to the left or right at all times including in the preoperative area and the post-anesthesia care unit. Pregnancy is a hyper-coagulable state, and embolism is a significant cause of maternal death in the United States. Measures should be taken to prevent perioperative venous thrombosis and pulmonary embolism.
Baseline coronary artery disease or cardiac dysfunction – Goals of management: Cardiac disease during pregnancy is rare. See chapter on Cardiac Disease during Pregnancy.

c. Pulmonary

COPD: COPD is rare in the pregnant population.
Reactive airway disease (Asthma): Asthmatic patients should be maintained on their usual medical regimen in the perioperative period. Any of the commonly used asthma medications are permissible during pregnancy. The adverse consequences to mother and fetus of hypoxia during an asthma attack far outweigh theoretical concerns about medications. Remember that beta agonists such as terbutaline are uterine relaxants and used to treat preterm labor.
Physiologic changes of pregnancy related to the respiratory system include an increase in minute ventilation and alveolar ventilation that lead to a fall in pCO2 and an increase in pO2. When interpreting blood gases in the pregnant patient, her pO2 may be over 100 torr breathing room air, and her pCO2 will be about 10 torr lower than nonpregnant. To compensate for the respiratory alkalosis, a mild metabolic acidosis develops. Keep these changes in mind when interpreting arterial blood gases and setting ventilation modes in the operating room and intensive care unit. Pregnant women have less respiratory reserve because their functional residual capacity (FRC) is decreased by about 20% while their oxygen consumption increases by about 20% – a supply-demand imbalance. Pregnant women will desaturate faster during periods of apnea such as rapid sequence induction and intubation. The risk of failed intubation is about 1 in 250 during pregnancy, 10 times higher than non-pregnant patients in the operating room. Their mucosa is friable and bleeds easily when endotracheal tubes or gastric tubes are placed in the nose. Breast enlargement, laryngeal edema and weight gain during pregnancy can also adversely impact airway management.

d. Renal-GI:

Renal blood flow and glomerular filtration rate normally double during pregnancy, thus creatinine levels are roughly half of nonpregnant levels.

Gastric reflux symptoms are common during pregnancy. Even asymptomatic women have reduced gastroesophageal sphincter tone that can lead to reflux and aspiration during heavy sedation or general anesthesia. Pressure from the enlarging uterus distorts pyloric anatomy and may increase intragastric pressure. Gastric motility is normal during pregnancy, but will be greatly reduced after opioids are administered or with painful conditions such as appendicitis or trauma. After the first trimester, consider pregnant women full stomach patients at risk for aspiration.

e. Neurologic:

Pregnancy leads to a decrease in requirements for both general and regional anesthetic agents. The minimum alveolar concentration (MAC) decreases by 25-40% for all volatile agents. What might be sub-anesthetic concentrations in a non-pregnant patient can induce unconsciousness when sedating a pregnant woman. The dose of local anesthetic needed for spinal and epidural anesthesia is also reduced by about 30%. This may be explained by increased sensitivity of the nerve during pregnancy because of hormonal influences such as progesterone.

f. Endocrine:

N/A

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Uteroplacental blood flow to the fetus is dependent on maternal cardiac output and blood pressure since uterine blood flow is not auto-regulated at term. Any maneuver that reduces cardiac output, causes hypotension, increases uterine tone such as contractions, or obstructs flow such as aortocaval compression will reduce blood flow to the fetus. Maternal oxygenation and oxygen content provide delivery of oxygen to the fetus and should be maintained at or above normal. Thus the recommendation to avoid hypoxia and hypotension.

4. What are the patient's medications and how should they be managed in the perioperative period?

Pregnant women rarely take medications other than prenatal vitamins and iron. They can be discontinued while the patient is NPO.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Few if any medications used in the perioperative period are considered teratogenic in humans. Opioids and anesthetic agents are safe. Drugs that should be avoided during pregnancy include angiotensin converting enzyme inhibitors (captopril, lisinopril, enalapril), some antiepileptic drugs (valproic acid, carbamazepine, phenytoin), tetracycline, radioactive iodine, coumarin derivatives, and some chemotherapy agents. Consultation with the obstetric service can help clarify whether medications should be avoided during pregnancy and whether there are safe alternatives.

i. What should be recommended with regard to continuation of medications taken chronically?

If a woman is receiving a medication during pregnancy prescribed by her obstetrician or with their approval (e.g. asthma medications), it should be continued in the perioperative period. Anti-coagulation therapy for thrombophilia or previous thromboembolic events will require consultation between the obstetric, hematology and surgical service in regards to their reversal intraoperatively and continuation postoperatively.

j. How To modify care for patients with known allergies –

Patients with antibiotic allergies may require alterations in the choice of preoperative antibiotics. Antibiotics are safe during pregnancy although tetracycline is avoided because of potential discoloration of the fetus’ adult teeth.

k. Latex allergy – If the patient has a sensitivity to latex (e.g. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

N/A

l. Does the patient have any antibiotic allergies?

The choice of antibiotic and its substitution in the case of allergy is based on the surgery being performed and the preference of the operating surgeon. Pregnancy should not affect those choices.

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia:

Documented – avoid all trigger agents such as succinylcholine and inhalational agents:

Proposed general anesthetic plan: A general anesthetic can be provided using non-triggering intravenous agents and a “clean” machine. Neuraxial anesthetics can be provided using ester local anesthetics such as 2-chloroprocaine for epidural anesthesia or tetracaine for spinal anesthesia.

Insure MH cart available: [- MH protocol]
Family history or risk factors for MH:
Local anesthetics/ muscle relaxants:

5. What laboratory tests should be obtained and has everything been reviewed?

A complete blood count with platelets should be reviewed. Hemoglobin and hematocrit levels will be lower during the second and third trimesters due to plasma volume expansion and the physiologic anemia of pregnancy. About 6-8% of pregnant women have gestational thrombocytopenia, but since these platelets have normal function, and levels rarely fall below 80,000, the clinical implications are minor. A complete blood count will give baseline values for both red cell and platelet count. Other lab values ordered will be individualized depending on the surgery being done.

A few lab values are significantly different during pregnancy. Hemoglobin and hematocrit are normally decreased by 28 weeks gestation. Creatinine values will be about half the non-pregnant value due to a doubling of glomerular filtration rate. Values >1.0 mg/dL are concerning. Arterial blood gases will show a respiratory alkalosis with pCO2 about 10 torr lower than nonpregnant values, and a compensatory metabolic acidosis. Arterial carbon dioxide values that are “normal” or high are definitely abnormal during pregnancy and indicative of respiratory depression or failure.

Hemoglobin levels: Obtain a baseline level to assess the dilutional effects of plasma volume expansion.
Electrolytes: A baseline creatinine level may be obtained to assess the effect of increased glomerular filtration rate.
Coagulation panel: A baseline platelet count will rule out gestational thrombocytopenia.
Imaging: Ultrasound will determine fetal age and viability.
Other tests: If pregnancy is suspected or uncertain, a urine or blood pregnancy test for human chorionic gonadotropin (hCG) level is appropriate.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

There are no outcome studies showing that general or regional anesthesia is preferred during pregnancy as long as maternal oxygenation and uteroplacental perfusion are maintained. Modify the safest anesthetic that is used for non-pregnant patients for the same or similar procedures. The greatest cause of fetal loss perioperatively is preterm labor and delivery of a pre-viable baby. General anesthetic concerns include exposure of the fetus to teratogenic medications (although no anesthetics have been shown to be teratogenic in humans) and a theoretical risk of anesthetic neurotoxicity to the fetal brain. The advantage of general anesthesia with volatile agents may be uterine relaxation and a lower incidence of preterm labor. Regional anesthesia may not be practical for some procedures such as neurosurgery. When appropriate, it has the advantage of not interfering with fetal heart rate variability on fetal monitoring as much as general anesthesia, and it provides excellent postoperative pain control that may allow early mobilization of these thrombophilic patients. Choice of anesthesia should be guided by maternal indications and the site and nature of the surgery. Uterine displacement should be maintained in the operating room after about 20-24 weeks’ gestation. Standard maternal monitoring should be used. Fetal monitoring has not been shown to change outcome, but may help the anesthesiologist assess adequacy of uteroplacental perfusion. If the surgical site precludes continuous intraoperative fetal monitoring, monitoring should occur preoperatively and postoperatively to document fetal viability. Use sequential compression devices on her legs. If ionizing radiation is needed for diagnostic studies, shield the fetus as much as possible.

a. Regional anesthesia – The advantages of regional

Neuraxial

Benefits: Drug exposure is minimized unless heavy sedation is used, reducing concerns about teratogenicity in the first trimester and reducing anesthetic effects on fetal monitoring later in pregnancy. Regional techniques often provide the best postoperative pain control, allowing for early mobilization to reduce risk of thromboembolism. Airway control is maintained, perhaps lessening risk of aspiration. If the mother is awake, it can be reassuring to her to hear the fetal heart rate on the monitor. The literature has shown a reduced or even absent risk of transient neurologic symptoms (TNS) in pregnancy associated with lidocaine spinal anesthesia, so this technique may be appropriate for short procedures.

Drawbacks: The patient or surgeon may be anxious that she is “awake” during the procedure. The surgical procedure may not be appropriate for neuraxial blocks (e.g. thoracic or neurosurgical procedures).

Issues: Aggressive prevention and treatment of hypotension is crucial. Maintain uterine displacement at all times. Use fluids to maintain normal preload and pressors to maintain normal blood pressure. Ephedrine or phenylephrine should be chosen based on maternal heart rate. Decrease local anesthetic dose in neuraxial blocks by about 30%, or use a catheter technique to titrate the local anesthetic with incremental dosing.
Peripheral Nerve Block

Benefits: Drug exposure is minimized, reducing concerns about teratogenicity in the first trimester and reducing anesthetic effects on fetal monitoring later in pregnancy, unless heavy sedation is used. These techniques often provide the best postoperative pain control, allowing for early mobilization to reduce risk of thromboembolism. Peripheral blocks will not impact ambulation and urination to the same extent as neuraxial techniques. If the mother is awake during her surgery, it can be reassuring to her to hear the fetal heart rate on the monitor. Airway control is maintained, perhaps lessening risk of aspiration.

Drawbacks: The patient or surgeon may be anxious about her being “awake” during the procedure. The surgical procedure may not be appropriate for peripheral nerve blocks.

Issues: Maintain uterine displacement at all times.

b. General Anesthesia

Benefits: The surgical procedure may require general anesthesia (e.g. neurosurgical or thoracic procedures). There is a small study showing that patients who received general anesthesia with volatile agents for abdominal surgery during pregnancy had a lower risk of preterm labor than those patients receiving regional anesthetics, although the rates in both anesthetic groups were still higher than the non-surgical group. The patient may prefer to be completely asleep during her procedure.
Drawbacks: Organogenesis occurs during first trimester, and that is when we are most concerned about exposure to potential teratogens. No anesthetics have been shown to be teratogenic, but the patient may be concerned and wish to avoid as much exposure as possible. While the implications are uncertain, fetal or newborn exposure to anesthetic agents (both NMDA blockers and GABA agonists) in animal studies results in widespread apoptotic neurodegeneration and persistent memory and learning impairments. The relevance to human exposure is unclear, but the equivalent period in humans is from the third trimester of pregnancy to about 3 years of age.
Other issues: If fetal monitoring is being used, loss of beat-to-beat variability is normal during general anesthesia or sedation. Nitrous oxide may be used at the anesthesiologist’s discretion. Maintain blood pressure at near-baseline levels to prevent decreases in uterine perfusion. End-tidal CO2 should reflect an arterial CO2 that is normal for pregnancy – roughly 10 torr lower than non-pregnant patients. Hyperventilation should be avoided to prevent decreases in cardiac output and alkalosis that could shift the oxy-hemoglobin dissociation curve to the left, decreasing the release of oxygen at the placenta.
Airway concerns: Functional residual capacity is decreased during pregnancy, so full preoxygenation and denitrogenation should be used to prolong time to desaturation during laryngoscopy and intubation. Full stomach precautions and rapid sequence induction with cricoid pressure should reduce aspiration risk from a full stomach. Smaller endotracheal tubes should be available in case the airway is edematous. The risk of failed intubation is much higher in pregnancy, so have tools available for an unanticipated difficulty airway.

c. Monitored Anesthesia Care

Benefits: Requirements for most anesthetics are reduced in pregnancy.
Drawbacks: Sedatives will reduce fetal heart rate variability if monitoring is being used. Avoid deep sedation because of full stomach concerns and risk of aspiration.
Other Issues: Any sedative preferred by the anesthesiologist can be used: midazolam, propofol, ketamine, dexmedetomidine, or opioids.

6. What is the author's preferred method of anesthesia technique and why?

The safest anesthetic that you would use for a non-pregnant patient having the same or similar procedure should be chosen, with modifications for the physiologic changes of pregnancy such as full stomach precautions and uterine displacement. The goals are maintaining maternal oxygenation and avoiding hypotension or decreases in cardiac output that would compromise uteroplacental perfusion. No outcome data has shown regional or general anesthesia to be preferable. If the procedure could be done using either a regional or general anesthetic, I prefer to discuss those options with the patient and let her choose the technique she is most comfortable with, based on questions about exposure to medications, being awake during the procedure, postoperative pain management, ability to observe the fetal monitor, or other concerns. She can be reassured that both techniques are routinely used for cesarean delivery and are safe for the fetus.

What prophylactic antibiotics should be administered? The antibiotic will be chosen based on the type of surgery being performed, but all antibiotics are acceptable during pregnancy.
What do I need to know about the surgical technique to optimize my anesthetic care? Pelvic and intra-abdominal procedures will preclude the use of intraoperative fetal monitoring. Uterine displacement should be maintained at all times in pregnancies in the second and third trimester. For laparoscopic techniques, open trocar placement may be preferred to avoid injury to the uterus, and the lowest possible insufflation pressure should be used.
What can I do intraoperatively to assist the surgeon and optimize patient care? This will depend on the specific surgical procedure.
What are the most common intraoperative complications and how can they be avoided/treated? Prioritize them by urgency. The surgeon should be notified if there are decelerations on the fetal heart rate monitor, and the obstetric team should be consulted. Maneuvers other than delivery that may improve uteroplacental perfusion and fetal oxygenation should be initiated. They may include increasing maternal FIO2, increasing maternal blood pressure, increasing left uterine displacement or trying displacement to the right, moving retractors away from the uterus, having the surgeons temporarily stop intra-abdominal manipulations, and administering a tocolytic such as nitroglycerin 100 mcg or terbutaline 0.25 mg IV if uterine contractions or irritability are causing variable decelerations.

Cardiac complications: Pregnant patients are at high risk for thromboembolic complications, and prophylaxis should include compression stockings at a minimum, with consideration of pharmacologic prophylaxis if the patient cannot be mobilized soon after surgery.
Pulmonary: The pregnant patient may be more at risk for pulmonary edema because of low oncotic pressure in later gestation. If an infectious process is present (e.g. ruptured appendix), endothelial leak coupled with lower oncotic pressure may increase that risk even further.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

Pregnant patients are assumed to have a full stomach and should be extubated only when strong and awake enough to protect their airway.

c. Postoperative management

What analgesic modalities can I implement? Continuous peripheral or neuraxial blocks with infusions are optimal if appropriate. All opioids may be used in pregnancy. Non-steroidal anti-inflammatory medications are usually avoided after 32 weeks gestation because prostaglandin inhibition could cause the fetal ductus arteriosus to close, leading to intrauterine fetal death. NSAID use in early pregnancy is probably acceptable, but acetaminophen or opioids are usually preferred.
What level bed acuity is appropriate? (Example: floor, telemetry, step-down, or ICU and justification): Beyond 24 weeks gestation, there should be obstetric nursing either physically present or by telemetry to monitor for uterine contractions and fetal heart rate abnormalities. For low acuity procedures, recovery can occur on labor and delivery. For higher acuity procedures, a labor and delivery nurse may be brought to the intensive care or step-down unit.
What are common postoperative complications, and ways to prevent and treat them? Preterm labor and delivery is most common after pelvic or intra-abdominal procedures and is associated with infectious processes as well. Monitoring for uterine contractions for at least 24 hours is appropriate, and the obstetric service may recommend prophylactic or therapeutic tocolysis with indomethacin, magnesium sulfate infusion, or calcium channel blocking agents. Thromboembolism prophylaxis should continue at least until the patient is mobilized.

What's the Evidence?

Reitman, E, Flood, P. “Anaesthetic considerations for nonobstetric surgery”. Br J Anaesth. vol. 107. 2011. pp. i72-i78.

Brown, HL. “Trauma in pregnancy”. Obstet Gynecol. vol. 114. 2009. pp. 147-160.

Baysinger, CL. “Imaging during pregnancy”. Anesth Analg. vol. 110. 2010. pp. 863-7.

“ASA / ACOG Joint Statement on Nonobstetric Surgery during Pregnancy.”. and Obstet Gynecol. vol. 117. 2011. pp. 420-2.

Buhimschi, CS, Weiner, CP. “Medications in pregnancy and lactation (part 1 and 2)”. Obstet Gynecol. vol. 113. 2009. pp. 166-88.

Abbassi-Ghanavati, M, Greer, LG, Cunningham, FG. “Pregnancy and laboratory studies”. Obstet Gynecol. vol. 114. 2009. pp. 1326-31.

Chohan, L, Kilpatrick, C. “Laparoscopy in pregnancy; a literature review”. Clin Obstet Gynecol. vol. 52. 2009. pp. 557-69.

Hong, JY. “Adnexal mass surgery and anesthesia during pregnancy: a 10-year retrospective review”. Int J Obstet Anesth. vol. 15. 2006. pp. 212-6.

Jevtovic-Todorovic, V, Absalom, AR, Blomgren, K. “Anaesthetic neurotoxicity and neuroplasticity: an expert group report and statement based on the BJA Salzburg Seminar”. Br J Anaesth. vol. 111. 2013. pp. 143-51.

John, AS, Gurley, F, Schaff, HV. “Cardiopulmonary bypass during pregnancy”. Ann Thoracic Surg. vol. 91. 2011. pp. 1191-7.

Wang, LP, Paech, MJ. “Neuroanesthesia for the pregnant woman”. Anesth Analg. vol. 107. 2008. pp. 193-200.

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