Hyperemesis Gravidarum

Nausea and Vomiting of Pregnancy

Nausea and vomiting of pregnancy exists in a spectrum, from what could be considered "normal" morning sickness to the severe hyperemesis gravidarum (HG) which can have significant impact on the health of the mother and fetus. HG is a complication of pregnancy characterised by intractable nausea, dehydration, electrolyte imbalance and significant weight loss. Nausea and vomiting of pregnancy will affect up to 70% of pregnant women whereas true HG is estimated to affect 0.5–2.0% of pregnancies. The underlying pathophysiology is not altogether clear but thought to be linked to a sensitivity to bHCG or oestrogens.

ED presentations

Presentations to ED with nausea and vomiting in pregnancy are common. The role of the Emergency Department clinician is to alleviate what can be extremely distressing symptoms; this can often be done with reassurance, IV fluids and anti-emetics. In the rare event of HG or suspected HG then admission may be required and supportive treatment with IV fluids, anti-emetics and vitamins to avoid levels of dehydration or malnutrition which might adversely affect the mother and baby.

Diagnosis of HG

In HG, intractable nausea will be accompanied by the triad of:

• Dehydration
• Electrolyte imbalance
• Weight loss of 5% of pre-pregnancy weight

The diagnosis of HG requires the exclusion of other serious causes of vomiting. Conditions such as appendicitis are know to present atypically in this population, and clinicians should perform a thorough abdominal examination and consider alternative diagnoses before attributing the symptoms to HG. If concerned or uncertain, involve a senior clinician.

Potential complications of HG

• Electrolyte abnormalities
• Metabolic alkalosis
• Mallory Weiss tear
• Reflex oesaphagitis
• Psychological effects, including depression
• Wernickes encepaphalopathy and Central pontine myelinolysis (rare but documented)
• Oesophageal rupture (rare)

Investigations

For simple and self-limiting nausea and vomiting very few investigations may be required other than urinalysis, and blood tests for renal function and electrolytes.

Investigations for HG include:

• Renal function and electrolytes (note that in pregnancy an increase in eGFR of up to 50% means that a "normal" urea and creatinine level may represent relative renal impairment.
• Urinalysis for ketonuria
• Urine culture if UTI suspected
• TFT - 60 % of women with HG will have biochemical thyrotoxicosis liver function tests
• LFT
• Pelvic ultrasound scan to confirm viable intrauterine pregnancy and to exclude trophoblastic pregnancy which can present with HG
• Consider Lipase to exclude pancreatitis
• Blood glucose level

Acute Management of HG

Dietary modification based on the woman’s own preferences is the first-line treatment which most patients will have tried prior to presentation to ED. When patients present to the ED then generally antiemetics and IV rehydration are used and for the most part this can be done within the ED or a short stay unit. Admission to hospital may be required in cases where the woman is unable to tolerate oral intake despite IV antiemetics, or in cases of true HG.

Rehydration

• IV normal saline +/- potassium as required
• Once vomiting is controlled, start a trial of oral fluids - small sips of fluid, often.

Antiemetics

• Metoclopramide 10mg IV 8 hourly (category A)

OR

• Ondansetron 4-8mg tds (category B1)

OR

• Prochlorperazine 12.5mg intramuscular injection, or slow IV injection.

Vitamins and Minerals

• IV thiamine 100mg daily should be given to all women requiring admission for prolonged vomiting, especially before parenteral dextrose
• Correct hypokalaemia, hypomagnesemia hypocalcaemia

Resources

It is important to reassure the woman that hyperemesis gravidarum is a significant illness and not "just morning sickness" and that a presenation to ED was entirely appropriate. Encourage the woman to represent to ED early for IV fluids before symptoms and dehydration become severe. Reassurance that the illness will be self limiting and that 90% of these symptoms will be resolved by week 16 may help.

• This Australian Family Physician paper covers this subject matter in more detail.
• ECI Patient Factsheet - Nausea and Vomiting in Pregnancy