Tuesday, 24 October 2017

Hyperemesis Gravidarum

We all know that nausea and vomiting in pregnancy is common affecting 50–75% of pregnant women any time from the 4th week of pregnancy, most common in the 9th and 12 week, and we probably misdiagnose some of these people with hyperemesis gravidarum which affects less than 1%. To me, I'm not sure that the precise difference matters, as I think I'd struggle to send home a ketotic pregnant lady with at least some of the hyperemesis protocol...

Hyperemesis Gravidarum
Persistent, intractable nausea and vomiting beginning in the first trimester
Associated with a weight loss of >5% of pre-pregnancy weight
Dehydration, electrolyte imbalance and ketosis


Cause
Likely multifactorial - typically higher levels of human chorionic gonadotrophin
H. pylori may have a part to play
Make sure you exclude other causes - molar pregnancy is the most serious. These patients are unlikely to improve enough to be able to go home.

Treatment
Antiemetics:
Ginger - evidence base says ginger tablets improve symptoms in four days

Other:
Small meals (6 times a day). Eat as soon as you feel hungry. Avoid likely triggers - like fatty food.
Fluids- cold, clear, and carbonated like ginger ales and lemonades as well as smoothies or slushies.

Thiamine - thiamine requirements increase in pregnancy, so give if "prolonged" vomiting. Some say if no meal in a weak, others say vomiting for more than three weeks.
Oral thiamine 100mg / day, or IV thiamine (pabrinex is OK, but does have other B vitamins). Toxbase suggests overdose of thiamine is low risk.

Antiacids- treat non ulcer dyspepsia if there are signs of it. PPIs are thought to be safe. There is some evidence that H. pylori increases vomiting, so if the patient has prolonged vomiting, consider

Corticosteroids - can be used as a third line. I'd like O&G do that bit.

Patient Advice 
No proven effects on the fetus, except fetal growth restriction, pre-term delivery. The pregnancy may be complicated by triploidy, trisomy 21 and hydrops fetalis. It may be due to a molar pregnancy.
Mum can get problems from electrolyte derangement - wernickes, central pontine myelinolysis due to hyponatraemia, ATN, splenic avulsion and increased VTE risk. Peripheral neuropathies are rare. One case report of epistaxis due to vitamin K deficiency!

Results
Ketones in the urine
Hypochloremic alkalosis
Slightly elevated liver enzymes - amniotransferases elevations are 2-3 times normal, but can be 15-20 times normal. They should resolve
Electrolyte abnormalities, typically hypokalaemia
Transient hyperthyroidism


1st Line - Cyclizine
Antihistamines (Cyclizine) and phenothiazines should be prescribed.

2nd Line - Metoclopramide
Safe and effective but there is a risk of extrapyramidal side effects.

3rd Line - Ondansetron
Some mostly unproven link with ondansetron and septal defects.

Fluids
RCOG says no evidence any fluid is better than another.
Nausea apparently resolves faster with dextrose containing fluid, but you need to check the sodium and consider thiamime replacement first - with the dogma that otherwise you can precipitate Wernickes.


References and Links
http://bestbets.org/bets/bet.php?id=2923
http://pmj.bmj.com/content/postgradmedj/72/853/688.full.pdf
https://www.rcog.org.uk/globalassets/documents/guidelines/green-top-guidelines/gtg69-hyperemesis.pdf
https://wikem.org/wiki/Hyperemesis_gravidarum
http://pmj.bmj.com/content/78/916/76
http://bestpractice.bmj.com/best-practice/evidence/intervention/1405/0/sr-1405-i8.html

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