Hyperemesis with Electrolyte Disturbance

Hyperemesis with electrolyte disturbance is severe nausea and vomiting of pregnancy with weight loss above 5 percent, ketosis and abnormal blood electrolytes, most often low potassium, sodium, magnesium or chloride. It results from raised hCG and prolonged vomiting. It matters because hypokalaemia causes arrhythmia and hyponatraemia can cause seizures, and rapid correction of sodium can cause osmotic demyelination.

• Occurs in about 0.3 to 3 percent of pregnancies.
• Risk factors: previous hyperemesis, multiple pregnancy, molar pregnancy, family history.
• Needs admission.

Women vomit repeatedly, cannot keep fluids down, and have weight loss, dry mucous membranes, tachycardia and weakness. Muscle cramps and palpitations reflect low potassium.

• Postural hypotension.
• Ketotic breath.
• Differential diagnosis: gastroenteritis, urinary tract infection, hepatitis, thyrotoxicosis, pancreatitis, diabetic ketoacidosis, molar pregnancy, Addison disease.
• Complications: cardiac arrhythmia, seizures, acute kidney injury, Wernicke encephalopathy, venous thrombosis, malnutrition, depression.

The approach is to measure electrolytes and exclude other causes.

• Sodium, potassium, chloride, urea, creatinine, bicarbonate, magnesium, calcium and glucose.
• Hypokalaemia below 3.5 mmol/L and hyponatraemia below 135 mmol/L confirm disturbance; ECG if potassium is below 3.0 mmol/L (flat T waves, U waves).
• Urinalysis for ketones, nitrites and leucocytes; liver tests; TSH and free T4; ultrasound.
• Weight on admission and daily.

The principle is IV rehydration, careful electrolyte replacement and antiemetics, with thiamine before dextrose.

• Supportive: admit; strict intake and output chart; weigh daily; cardiac monitoring if potassium is below 3.0 mmol/L; correct sodium by no more than 10 mmol/L in 24 hours; small oral intake when tolerated.
• Pharmacological: thiamine 100 mg IV daily for 3 days before any dextrose; sodium chloride 0.9 percent 1 litre IV over 1 to 2 hours, then 1 litre over 4 to 6 hours; add potassium chloride 20 mmol per litre (maximum rate 10 mmol per hour peripherally); magnesium sulphate 2 g IV over 2 hours if magnesium is low; metoclopramide 10 mg IV 8-hourly (maximum 5 days); promethazine 12.5 to 25 mg IV or IM 8-hourly (maximum 100 mg daily); ondansetron 4 mg IV 8-hourly if others fail; hydrocortisone 100 mg IV 12-hourly for refractory cases, then prednisolone 40 mg oral daily tapered over 2 weeks; enoxaparin 40 mg subcutaneous daily for admission above 3 days.
• Procedures: none; nasogastric or parenteral feeding for refractory cases.
• Special groups: women with kidney impairment have potassium replacement slowed with frequent rechecks; women with diabetes monitor glucose 4-hourly.
• Red flags: potassium below 3.0 mmol/L, sodium below 125 mmol/L, confusion, ataxia, visual change, palpitations, no urine.
• Follow-up: recheck electrolytes daily until normal; discharge when tolerating oral intake; review weekly; weight at each visit; psychological support.