Sunday, March 21, 2021

Appendectomy in the Pregnant Patient Case File

Posted By: Medical Group - 3/21/2021 Post Author : Medical Group Post Date : Sunday, March 21, 2021 Post Time : 3/21/2021
Appendectomy in the Pregnant Patient Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 33
A 26 year-old Gravida (G) 1 Para (P) 0 woman presents to the emergency room 26 weeks pregnant and with abdominal pain. She has received excellent prenatal care. The abdominal pain started the afternoon prior to presentation. It is diffuse in nature in the right lower quadrant, but poorly localized. She has had some loss of appetite but no nausea and vomiting since the onset of pain. Nevertheless, she ate parts of a cheeseburger and fries approximately 4 hours prior to the ER visit. The patient is otherwise healthy, and takes no medications except for a multivitamin. She is 5 ft 8 in tall and weighs 165 pounds. Vital signs are normal, as are her laboratory values, with the exception of a WBC count of 9500/mm3. On computerized tomography, the patient is found to have acute appendicitis and is scheduled for an urgent laparoscopic appendectomy.

➤ What are the anesthetic considerations in a pregnant patient?

➤ What is the most important goal when anesthetizing a pregnant patient undergoing nonobstetric surgery?


ANSWERS TO CASE 33:
Appendectomy in the Pregnant Patient

Summary: This is a healthy woman at 26-weeks gestation, in the mid trimester of pregnancy, who presents for an urgent laparoscopic appendectomy. She may need open appendectomy if the appendix cannot be removed via laparoscopy.

Anesthetic concerns in pregnancy: Physiologic changes such as airway edema and decreased gastric emptying affect intubation and increase the risk of pulmonary aspiration. The placenta acts as a sieve and all drugs delivered to the patient have potential to have effect in the baby. Choice of drugs is limited in pregnancy.

Most important goals: When anesthetizing a pregnant patient for nonobstetrical surgery, the most important goals are to be vigilant and meticulous in the care of the mother, minimizing any changes in hemodynamic and acid-base parameters.


ANALYSIS

Objectives
1. Understand the nuances of nonpregnant surgery in the pregnant patient.
2. Elucidate anesthetic concerns with pregnancy in nonobstetrical surgery.
3. Review placental physiology and the concept of the uteroplacental barrier.


Considerations
This 26-year-old woman who is pregnant in the mid trimester requires general anesthesia for a laparoscopic appendectomy. She is brought to the operating room, and her uterus is displaced by placing a pillow under her lower left back to avoid potential aorto-caval compression, which would decrease venous blood flow back to the heart. Routine ASA monitors are placed, and preoxygenation is begun with 100% oxygen. A rapid sequence induction with endotracheal intubation is performed, since in both emergency cases and in pregnancy, there is an increased risk of pulmonary aspiration of gastric contents. Positive pressure ventilation is instituted following intubation to keep the PaCO2 between 28 and 30 mm of Hg, which is the normal level in pregnancy. Normocarbia ensures a normal acid-base status in the mother, since maternal acidemia may lead to fetal acidemia, and maternal alkalosis may reduce uterine blood flow.

Maintenance of anesthesia is performed with a balanced combined technique consisting of appropriate doses of narcotic, inhalational agents, and muscle relaxants. Inhalation agents are useful, because they relax smooth muscle, contrary to any contractions which might occur. Nitrous oxide is commonly avoided in laparoscopic surgeries because of bowel distention. Continuous fetal heart rate monitoring while useful, may be difficult in this patient requiring an intra-abdominal procedure, and is typically not performed in this setting.

On completion of the operation, it is anticipated that the patient will be extubated just as anyone else who has undergone this procedure. An obstetrician will examine the patient in the PACU to ascertain the state of maternal and fetal well-being, and monitor for preterm labor.


APPROACH TO
Appendectomy in the Pregnant Patient

PHYSIOLOGICAL CHANGES
Appendicitis is difficult to diagnose in a pregnant patient. The signs and symptoms of appendicitis may well mimic pregnancy (nausea, vomiting, constipation, abdominal pain). Moreover, the reluctance to subject a pregnant patient to radiographic exposure may further delay diagnosis. By the same token, a delayed diagnosis also leads to complications as pregnancy renders the formation of an appendiceal abscess more likely. Also, the possibility of rupture is both more plausible and more problematic. The point to remember is that ultrasonographic imaging is safe and useful in pregnancy.

The decision to proceed with laparoscopic versus open surgery is the next challenge. As in the nonpregnant patient, laparoscopic surgery is associated with improved postoperative pain control, earlier mobility, and recovery of gastrointestinal motility. The use of laparoscopy has also become very popular for appendectomies, as laparoscopy allows for an improved visualization of several intra-abdominal structures.

However, the issues with laparoscopy in the pregnant patient include:
• Carbon dioxide absorption by the fetus by placental transfer leading to fetal acidemia
• Uterine or fetal trauma
• Increased intra-abdominal pressure from the insufflation with CO2, which could impair maternal ventilation as well as increase the possibility of aortocaval compression

If the surgery were to be performed as an “open” (nonlaparoscopic) procedure, then spinal would be the anesthetic of choice, since neuraxial techniques minimize fetal exposure to circulating drugs.

Any abdominal surgery in a pregnant patient risks fetal loss, though the risk is higher in the first trimester than in the second trimester. Unless an emergency threatens life or limb, surgery should be delayed till the second or third trimester of pregnancy.

Amniotic fluid acts can conduct electrical current to the fetus. Bipolar cautery is preferred over monopolar cautery, since the currents are more streamlined, and there is less likelihood of stray currents going through the fetus. Additionally, the grounding pad should be placed in such a way that the uterus is not in the pathway of the current.

Maternal hypotension can jeopardize uteroplacental perfusion. The most common causes of hypotension in the mother include:

• Deep levels of general anesthesia
• Aorto-caval compression by the pregnant uterus
• Sympathetic blockade from a high epidural or spinal block
• Hemorrhage
• Hypovolemia

Additional factors that affect uteroplacental perfusion include uterine vasoconstriction by vasoactive drugs such as phenylephrine and epinephrine. Indirect-acting agents such as ephedrine are preferred in pregnancy to preserve blood supply to the fetus. High levels of anxiety in the mother can also result in a catecholamine surge that may impair placental blood flow. However, benzodiazepines are contraindicated because of their teratogenic effects.

Studies of nonobstetrical surgery in the pregnant patient show an increased risk of abortion and preterm birth, especially in the first week after surgery. Prophylactic tocolysis is controversial. Monitoring the mother for uterine contractions for several days after the surgery is recommended, since in the presence of premature uterine contractions, the prompt institution of tocolysis is appropriate. Fetal monitoring is not usually performed in the operating room during the surgery, since surgery is only performed in situations with significant risk to the mother.


Comprehension Questions

33.1. What are the advantages of regional anesthesia in the gravid patient presenting for nonobstetric surgery?
A. Increased risk of aspiration due to relaxation of the lower esophageal sphincter
B. Increased risk of aspiration due to slower gastric emptying
C. Decreased placental transmission of drugs
D. Decreased risk of miscarriage

33.2. Hypotension in a gravid patient under anesthesia is most commonly the result of which of the following?
A. Aorto-caval compression
B. Hypercarbia
C. Hypervolemia
D. A “light” level of general anesthesia


ANSWERS
33.1. D. Regional techniques provide analgesia without exposing the fetus to a high concentration of drugs. This is possible because during a spinal anesthetic, a small amount of a local anesthetic is injected into the subarachnoid space. In contrast, general anesthesia in the gravid patient is associated with increased incidence of aspiration and difficult airway management as the result of anatomical and hormonal changes during pregnancy.

33.2. A. Hypotension in the supine gravid patient is most commonly a result of aorto-caval compression by the gravid uterus. Other causes include “deep” anesthesia, a sympathetic blockade during regional techniques, hemorrhage and hypovolemia are other causes of hypotension in the pregnant patient.


Clinical Pearls
➤ Fetal monitoring is not typically performed during nonobstetrical operations in pregnant patients during the first or second trimester.
➤ The pregnant uterus causes vena caval compression in the supine position, and can cause significant hypotension in both the mother and the fetus.
➤ The majority of drugs administered to the mother will cross the uteroplacental barrier.
➤ Maternal complications such as hypoxia, acidemia and hypotension are
associated with the most dramatic fetal consequences.

References

Chestnut DH. Obstetric Anesthesia: Principles and Practice. 2nd ed. Nonobstetric surgery during pregnancy. Mosby publishing. 

Guidelines by the American Society for Gastrointestinal Endoscopy: Guidelines for endoscopy in pregnant and lactating women. Gastrointest endosc. 2005;61: 357-362. 

Jackson H, Granger S, Price R, et al. Diagnosis and laparoscopic treatment of surgical diseases during pregnancy: An evidence based review. Surg Endosc. 2008;22:1917- 1927. 

Society of American Gastrointestinal and Endoscopic Surgeons: Guidelines for the diagnosis, treatment, and use of laparoscopy for surgical problems during pregnancy. Surg Endosc. 1998;12:189-190.

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