Nausea, vomiting and hyperemesis gravidarum

Assessment

• Nausea and vomiting of pregnancy affects 70 to 80 percent, peaks at 9 to 10 weeks and settles by 16 to 20. Hyperemesis is the severe end: persistent vomiting, weight loss over 5 percent, dehydration and ketonuria, often needing admission.
• Look for a cause beyond pregnancy when it starts after 10 weeks or has other features: urinary infection, thyroid disease, gastroenteritis, molar or multiple pregnancy (a very high hCG), pancreatitis, cholecystitis.
• Bloods: electrolytes (hypokalaemia, hyponatraemia), urea and creatinine, liver enzymes (mildly raised in hyperemesis), TSH and free T4 (a suppressed TSH with a normal free T4 is the hCG effect, not thyrotoxicosis).

Management ladder

1. 1

   Diet and lifestyle

   Small frequent meals, ginger, avoiding triggers; acupressure for those who find it helps.

2. 2

   First-line medication

   Doxylamine-pyridoxine (delayed release) is the Canadian first line; pyridoxine alone is an alternative.

3. 3

   Second line

   Dimenhydrinate, metoclopramide, prochlorperazine or promethazine; ondansetron where these fail (a small, debated association with oral clefts in the first trimester is discussed).

4. 4

   Hyperemesis

   Admit, intravenous rehydration with potassium replacement, thiamine before any dextrose (Wernicke's encephalopathy), antiemetics parenterally, corticosteroids in refractory cases, thromboprophylaxis.

Ondansetron in PharmSpace