Clinical meaning
Hyperemesis gravidarum results from exaggerated physiological responses to pregnancy hormones, primarily hCG, which peaks at 8-12 weeks gestation. Elevated hCG stimulates the chemoreceptor trigger zone (CTZ) in the area postrema and increases thyroid hormone levels (hCG shares structural homology with TSH). Persistent vomiting depletes intravascular volume, causes electrolyte derangements (hypokalemia, hypochloremic metabolic alkalosis, hyponatremia), and shifts metabolism to fat catabolism with resultant ketonemia. Severe, prolonged cases can lead to Wernicke encephalopathy from thiamine (vitamin B1) depletion, hepatic dysfunction, and renal impairment. The nurse must manage fluid and electrolyte replacement, administer antiemetics, monitor nutritional status, and coordinate multidisciplinary care.
Exam relevance
Risk factors: - Elevated hCG levels (molar pregnancy, multiple gestation) - Primiparous women - History of hyperemesis in prior pregnancy (15-20% recurrence) - History of motion sickness, migraines, or GI disorders - Hyperthyroidism (hCG-mediated) - Helicobacter pylori infection - Female fetus (associated with higher hCG levels) - Psychological stress and eating disorders