Lori Weichenthal
Although nausea and vomiting are quite common in pregnancy, affecting 70% to 85% of all pregnant women, hyperemesis gravidarum, the most severe manifestation of this disorder, is far rarer, with an incidence rate of only 0.3% to 2% (1,2). Defined as persistent vomiting accompanied by weight loss exceeding 5% of prepregnancy weight that is often associated with ketonuria, severe dehydration, and electrolyte imbalance, hyperemesis can cause significant maternal morbidity if not treated early and aggressively (3). Although the pathogenesis of hyperemesis remains unknown, many theories relate it to hormonal, neurologic, metabolic, toxic, and psychogenic factors. It is agreed that human chorionic gonadotropin (hCG) serum levels are a likely causative factor, given that they peak in the first trimester when severe nausea and vomiting are typically seen and that hyperemesis is more common in women with multiple fetuses and gestational trophoblastic disease, both of which are characterized by higher serum hCG levels (4,5).
CLINICAL PRESENTATION
Hyperemesis gravidarum is a clinical diagnosis, suggested by the findings of intractable vomiting, weight loss, and ketouria beginning in the first trimester of pregnancy. Abdominal pain and fever are uncommon in hyperemesis and should suggest an alternative diagnosis. The onset of symptoms is typically between 4 and 10 weeks of gestation, and hospitalization rates peak at 9 to 10 weeks (6). Nausea and vomiting that develop beyond 10 weeks of gestation are generally thought to be due to another cause.
Patients with hyperemesis have few distinct physical findings besides those associated with dehydration, such as vital sign abnormalities (tachycardia with or without hypotension), dry oral mucosa, and poor skin turgor. Laboratory abnormalities may or may not be present but can include electrolyte abnormalities such as hypokalemia, metabolic alkalosis, increased blood urea nitrogen; elevated urine-specific gravity and ketonuria; increased hematocrit due to hemoconcentration; mild abnormalities in liver enzyme values; and mild hyperthyroidism.
DIFFERENTIAL DIAGNOSIS
Hyperemesis is generally a diagnosis of exclusion, based on its development in early pregnancy and gradual resolution over time. The differential diagnosis of nausea and vomiting in the pregnant women is extensive and includes disorders related and unrelated to pregnancy (Table 138.1). Some common disorders for the emergency physician to consider include pyelonephritis, appendicitis, cholelithiasis, pancreatitis, gastritis, central nervous system disorders, and toxic and metabolic disturbances. As mentioned, development of nausea and vomiting after 10 weeks gestation should suggest another diagnosis. Other symptoms that should make the EP consider an alternative diagnosis include abdominal pain, fever, headache, diarrhea and/or constipation, abnormal neurologic findings, or hypertension.
TABLE 138.1
Differential Diagnosis of Nausea and Vomiting in Pregnancy
ED EVALUATION
When a pregnant woman presents to the emergency department (ED) with nausea and vomiting, a careful history and physical examination should be obtained to assess the severity of symptoms and physical findings, to determine the need for aggressive resuscitation, and to help exclude alternative causes. Important historical considerations include the time of onset of nausea and vomiting during pregnancy and other related symptoms. It is also important to note any medications or herbal preparations that the patient is using. On physical examination, it is important to assess for signs of dehydration, including vital sign abnormalities, dry oral mucosa, and poor skin turgor. The physician should look for physical examination findings such as fever, abdominal tenderness, costovertebral tenderness, jaundice, goiter, or neurologic deficits that might suggest another diagnosis. A pelvic examination is necessary if the patient has abdominal or pelvic pain, vaginal discharge, or bleeding. A measurement of weight should also be obtained.
Diagnostic tests to consider include serum electrolytes, a urinalysis, a complete blood count, liver function tests, and serum-free T4 concentrations. An elevated hematocrit and blood urea nitrogen may be present owing to hemoconcentration. Hyper- or hyponatremia and hypokalemia may be present when vomiting has been profuse or persistent. Urinalysis is helpful in gauging the degree of dehydration and ketonuria and for looking for signs of urinary tract infection. Pelvic ultrasound examination might be helpful to exclude gestational trophoblastic disease or multiple gestations. Other imaging studies should be ordered as clinically indicated or as directed by laboratory findings.
KEY TESTING
• Urinalysis and serum electrolytes
ED MANAGEMENT
For patients who appear clinically dehydrated or who have ketonuria, intravenous rehydration should be initiated with D5 lactated Ringer’s or D5 normal saline solutions. Typically, an initial bolus of 1 to 2 L is given, and further hydration is determined by the patient’s response. Vital signs, symptoms, and urine output should be monitored. Antiemetics are frequently required and should be administered intravenously. Ondansetron has become the most common antiemetic used for the treatment of hyperemesis in the ED, owing to its efficacy and safety profile in pregnancy (class B) (7). Metoclopramide, which is also considered safe in pregnancy, is also frequently used, as are promethazine and prochlorperazine, whose safety in pregnancy have not been well established (Table 138.2). Many recommend giving thiamine, 100 mg IV, to women who have experienced significant nausea and vomiting, as Wernicke encephalopathy is a rare but serious complication of hyperemesis (8).
TABLE 138.2
Antiemetics Used to Treat Hyperemesis
It has recently been suggested that corticosteroids are of potential benefit in the treatment of hyperemesis gravidarum, but they may be associated with an increased risk of oral clefts if used in the first trimester (9). Thus, corticosteroids should be used only as a last resort and in consultation with an obstetrician (1).
CRITICAL INTERVENTIONS
• IV fluid resuscitation as needed
• Antiemetics
DISPOSITION
Women who have intractable vomiting despite aggressive therapy, have persistent electrolyte abnormalities or ketosis, and who have lost more than 10% of their prepregnancy weight generally require admission for further therapy and observation. Approximately 5% of patients with hyperemesis require hospitalization (10)
In patients without laboratory abnormalities, the goal is to correct the dehydration and to ensure that the patient can tolerate oral intake prior to discharge from the ED. Some patients may require an orally or rectally administered antiemetic for use as an outpatient to control their symptoms, though many women can manage their symptoms through behavioral modifications and dietary changes. Women should be counseled to avoid environmental triggers and to eat small, frequent high-carbohydrate, low-fat meals (11). One randomized controlled study found that ginger extract, 1 g daily, reduced the nausea and vomiting associated with early pregnancy (12). Other adjunctive treatments, including hypnosis, psychotherapy, vitamin B6 (pyridoxine), and acupressure have also shown promise.
Women who are discharged home should be educated on the expected course of their symptoms, should have close follow-up arranged with their healthcare provider, and should be advised to seek medical help sooner if symptoms change or become more severe or if they develop dizziness or inability to take anything by mouth.
Common Pitfalls
• Failure to aggressively rehydrate women with significant dehydration.
• Failure to consider alternative diagnoses in pregnant women with nausea and vomiting.
REFERENCES
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12. Willetts KE, Ekangaki A, Eden JA. Effect of ginger extract on pregnancy-induced nausea: A randomized controlled trial. Aust N Z J Obstet Gynaecol. 2003;43:139–144.