17
SEP
2017

Interventional Radiology and the Pregnant Patient

By Lourdes Alanis, MD, MPH

 

 

Introduction

Interventional radiology (IR) procedures can be safely performed in pregnant patients with knowledge regarding both their general and specific medical needs. Pregnant patients undergoing IR procedures require a different set of management skills which include competent procedural technique and efficient medical management of the patient and fetus. When treating these patients, Interventional radiologists should consider if the procedure is truly medically necessary and how to best minimize fetal radiation dose while providing care. 1,2

Ionizing Radiation Exposure

The goal of any IR procedure is to minimize fetal exposure to ionizing radiation given its detrimental effects on the developing fetus.1 Ionizing radiation exposure can result in adverse effects such as organ malformation and fetal death during gestational weeks 2 through 8.1,3 According to the National Council on Radiation Protection and Measurement (NCRP) the risk of deleterious effects is negligible with exposure to 50 mGy or less of ionizing radiation; however, this risk increases significantly with doses above 150 mGy.2,3 Most fluoroscopically­guided IR procedures fall within the range of threshold doses (10­200 mGy) which can result in adverse effects, especially during the first trimester of pregnancy.1,2 Therefore, it is imperative to practice the ALARA principle (As Low As Reasonably Achievable) when performing ionizing radiation imaging modalities in pregnant patients.3 Strategies to minimize fetal radiation dose should be implemented into daily practice (Table 1). In addition, ultrasound (US)­guided or magnetic resonance­guided (without gadolinium­based contrast) procedures should be considered prior to procedures requiring ionizing radiation exposure. Inadvertent exposure should be discussed with the patient, referring physician, and medical physicist to provide appropriate maternal counseling. If fluoroscopic guidance is deemed the procedure of choice, measures of radiation exposure (i.e. fluoroscopy time) should be recorded in the patient’s medical record and the procedure report.4

Managing the Pregnant Patient

The decision to proceed with a procedure should be based on the medical indication and degree of necessity based on the patient’s medical condition. It is important to plan and discuss any procedures with the referring obstetrician to ensure appropriate obstetrical care before, during, and after the procedure.1 Medical­decision making should be a team effort and the consent process should include the patient and/or family, the referring obstetrician, and other treating physicians. When consenting patients, interventional radiologists should discuss the benefits, risks, alternative procedures, use of sedatives and analgesics, and the potential effects of radiation exposure.2

Patient positioning is important in patients beyond 20 weeks of pregnancy. A left lateral decubitus position is preferred to minimize compression of the inferior vena cava (IVC) by the gravid uterus.2 Additional challenges include: increased ventilation requirements due to decreased diaphragmatic excursion from the gravid uterus; increase in overall blood volume resulting in decreased concentration of water­soluble medications and delay in medication effects; increased glomerular filtration rate results in increased rate of drug clearance; and decreased rate of food absorption and function of the lower esophageal sphincter increases the risk of aspiration.2

Physiologic  changes  in pregnancy can make sedation challenging. Interventional radiologists should consult with an anesthesiologist to discuss the level of sedation as well as the amount and duration to minimize any complications such as hypoxia and hypotension.2 The majority of medications used for IR procedures are FDA categories B and C.2 Special consideration of medications used in pregnant patients should include whether their benefit outweighs their risk. Some of these medications include the following: contrast agents (e.g., iodinated contrast and gadolinium), topical anesthetics, NSAIDs, reversal agents, steroids, analgesics and sedation, prophylactic antibiotics, and antiemetics (Table 2).2

Indications and Procedures

IR may be consulted for the following indications and procedures should be classified as emergent, urgent, or elective. Emergent IR procedures include hemorrhagic emergencies that require transarterial embolization such as trauma, ectopic pregnancy, and placental implantation abnormalities.1,4 Emergent/Urgent IR procedures include renal hemorrhage and artery aneurysms such as splenic artery and gastroduodenal artery.3 Urgent/Elective IR procedures may include symptomatic ovarian cyst. Elective IR procedures include venous ablations, uterine fibroid embolization, and occlusion of arteriovenous (AV) fistula or malformations.1,4 If possible, elective procedures should be postponed until

6 weeks postpartum.2 Procedures such as percutaneous nephrostomy, percutaneous drainage, or percutaneous cholecystostomy can be accomplished with US guidance or with minimal amount of fluoroscopy for catheter placement confirmation.

Trauma: Management of the pregnant acute trauma patient requires reestablishment and maintenance of maternal hemodynamic stability.2 Diagnosis and endovascular techniques for management of arterial injuries of the extremities and organs are similar to those in nonpregnant patients.2 Collaboration between interventional radiologists, trauma surgeons, and obstetricians is critical in managing these patients.

Abnormal placentation (i.e. placenta previa, accreta, increta, and percreta) can result in life threatening peripartum hemorrhage.2­4 The use of bilateral internal iliac artery balloons or bilateral femoral vascular sheaths for arterial embolization may be used. However, their use is controversial in the management of placenta accreta as there is a mixed review with some studies reporting reduced blood loss, others showing no benefit or higher complication rate.3 Persistent hemorrhage after delivery secondary to uterine atony, uterine arterial injury, or AV fistula may be treated with uterine artery embolization using temporary agents (e.g. Gelfoam).2,4

Ectopic pregnancy: An alternative to surgical and medical therapies is the direct injection of a chemical (e.g., methotrexate, potassium chloride, or hyperosmolar glucose) into the ectopic implant via ultrasound guidance.3,4 This technique decreases the risk for systemic toxicity from methotrexate administration and helps preserve intrauterine pregnancy in heterotopic pregnancies.3

Biliary obstructive disease: Increased estrogen and progesterone levels during pregnancy contribute to gallstone formation. If conservative treatment fails, more invasive treatments such as US­guided percutaneous cholecystostomy may be required.3

Obstructive uropathy: Nephrolithiasis and/or hydronephrosis may be common in pregnancy.4 If conservative treatment with hydration and analgesia fails, placement of percutaneous nephrostomy tubes under US guidance or minimal fluoroscopy to ensure catheter placement may be performed.2,3

Venous Thromboembolic Disease: Incidence of venous thromboembolism (deep venous thrombosis [DVT] and pulmonary embolism [PE]) is four to five times greater in pregnancy secondary to the hypercoagulable state of pregnancy.2 Treatment may consist of a suprarenal IVC placement according to the Society of Interventional Radiology (SIR).2

Symptomatic ovarian cyst: Large ovarian cysts can cause pelvic pressure or pain and exclusion of ovarian torsion should be performed via ultrasound prior to any intervention. Simple cysts may be aspirated via transvaginal or transabdominal US guidance.4

Abdominopelvic abscess: After a cesarean delivery, postoperative fluid collections may occur in the abdomen, pelvis, retroperitoneum, or abdominal wall.4 US or CT image guided drainage may be performed.

Conclusion

Prior to any IR procedure the following should be discussed and addressed: fetal monitoring before, during, and after the procedure (anesthesiology, equipment, and nursing staff); recovery location (immediate post procedure and long­term recovery); and available resources in the event of an emergency delivery outside the labor and delivery floor (equipment, obstetricians, neonatologists, nursing staff, etc.).3 The safe and efficient management of pregnant patients requires knowledge about fetal radiation dose exposure and the risks versus benefits of various medications used during IR procedures as well as a multidisciplinary team consisting of interventional radiologists, obstetricians, anesthesiologists, nursing, and ancillary staff.

 

 

Table 1. Strategies to minimize fetal radiation dose. (1,2,4)

Techniques
Fluoroscopy time
  • Absorbed radiation dose is directly related to exposure time
  • Tread lightly on fluoroscopy pedal
  • Monitor dose rate and cumulative absorbed dose
Fluoroscopy frame rate
  • Maintain frame rate at the lowest level possible to adequately visualize anatomy and instruments
Last image hold
  • Minimize radiographic exposure during procedures by using a recorded image
Digital subtraction angiography (DSA) frame rate
  • Tailor DSA frame rate and total number of frames to the anatomic area and blood flow rate being imaged
  • Perform with as few images as necessary to minimize DSA exposure
Beam geometry
  • Image from a posterior­anterior position (x­ray beam enters the back of the patient and exits the front) to lower absorbed dose and thus, lower Compton scatter (primary source of fetal radiation dose)
Table position
  • Adjust table as high as possible from the x­ray tube and position the image receptor close to the patient
Field collimation
  • Collimate as tightly as possible to minimize the volume of tissue exposed to ionizing radiation
Magnification mode
  • Use during procedures that will require longer fluoroscopy time without its use or when needing to deploy a microcoil

 

Table 2. Special consideration and FDA pregnancy categories of medications.2

Medication Special consideration Pregnancy category
Contrast Agents
Iodinated contrast Avoid in first trimester if possible and use only whennecessary with informed consent B
Gadolinium Avoid per ACR C
Topical Anesthesia
Lidocaine, benzocaine, procaine,tetracaine Cocaine  contraindicated B
Reversal Agents
Naloxone Contraindicated in patients with narcoticdependence B
Flumazenil C
Steroids
Hydrocortisone, prednisone,methylprednisolone Prednisone and methylprednisolone higher resistance to crossing placental barrier C (2nd and 3rd trimester)D (1st trimester)
Other
Diphenhydramine(Benadryl) Uterine contractions with overdose B
Acetaminophen(Tylenol) C
NSAIDs (ibuprofen,naproxen) Premature closure of ductus arteriosus C
Analgesics and Sedation
Fentanyl C
Meperidine Preferred over Fentanyl B
Morphine Readily crosses to fetal brain C
Hydromorphone C
Propofol First­line for deeper sedation B
Benzodiazepine (Midazolam, Diazepam, Lorazepam,Alprazolam) Diazepam  contraindicated D
Prophylactic Antibiotics
Penicillin­based(cefazolin, ampicillin, Increased blood clearance later in pregnancy B

 

References

  1. Marx Interventional radiology: management of the pregnant patient. Techniques in vascular and interventional radiology. 2010;13(3):154­157.
  2. Moon EK, Wang W, Newman JS, Bayona­Molano Mdel Challenges in interventional radiology: the pregnant patient. Seminars in interventional radiology. 2013;30(4):394­402.
  3. Peralta F, Wong CA. Interventional radiology in the pregnant patient for obstetric and nonobstetric indications: organizational, anesthetic, and procedural Current opinion in anaesthesiology. 2013;26(4):450­455.
  4. Thabet A, Kalva SP, Liu B, Mueller PR, Lee Interventional radiology in pregnancy complications: indications, technique, and methods for minimizing radiation exposure. Radiographics : a review publication of the Radiological Society of North America, Inc. 2012;32(1):255­274.
  5. Health and Human Services USDo. FDA Pregnancy Categories. 2017; https://chemm.nlm.nih.gov/pregnancycategories.htm. Accessed  June  18,

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