The card for the worst night.
When you can't get the words out, this can. It states your history plainly, names the one sign that raises suspicion of CHS without pretending it confirms anything, and asks the clinician to keep looking. Print it and you get the short version, sized for a wallet. Everything that wouldn't fit on two sides of card stock, the full differential, the medication evidence, and links to real hospital pathways, lives on this page and behind the QR code on the back.
One dataset found patients averaged 17.9 emergency visits and $76,920.92 in combined emergency and imaging costs before they were diagnosed (Zimmer et al. 2019). This card exists to bring that number down, not to replace the workup that gets someone there faster.
This page was revised on 31 July 2026. The version before it reported the wrong figure for a key trial and carried no differential list for the clinician to check against. Every card below now carries a small version stamp, v2026.07.31, on both faces. If the card in your wallet is missing one, or shows an earlier date, it's out of date. Print a new one and throw the old one away.
Hyperemesis Syndrome
I'm a long term, heavy cannabis user with cyclic vomiting. Hot water usually helps, which raises the chance of CHS but doesn't confirm it.
- Ondansetron is usual care, helps about a third. Its authors found a failed dose should not be repeated or increased.
- GRACE-4 (2024): haloperidol or droperidol added to usual care, low certainty evidence. Check potassium and ECG first; correct K+ under 3 mEq/L.
- Opioids are advised against, per Hopkins and the AGA.
- Diagnosis of exclusion. Please continue to rule out other causes, for example bowel obstruction, pancreatitis, DKA and pregnancy. Full differential at the QR.
Why it's written this way
A card that named a specific drug could make a busy team anchor on CHS and miss something else, especially before anyone has checked a potassium or run an ECG. This one does the opposite. It cites the trials, notes what's uncertain, including the fact that hot water relief raises the chance of CHS without confirming it, and defers every choice to the clinician in front of you. It helps a doctor do the job. It doesn't try to do it for them.
On a phone? Screenshot both cards above and keep them somewhere fast to find. Either way, the QR on the back opens the full evidence, the complete differential, and the hospital pathways this card is built from, so a curious clinician can check everything for themselves.
The trial, read exactly as published
HaVOC compared haloperidol against ondansetron in adults with CHS, in a crossover design. In the first treatment period, 4 of 13 patients (31%) on haloperidol needed rescue antiemetics, compared with 10 of 17 (59%) on ondansetron. Ruberto AJ et al., Ann Emerg Med 2021;77(6):613 to 619.
The difference was -28 percentage points, with a 95% confidence interval that ran from -61% to 13%. That interval crosses zero, which means the trial cannot rule out no difference at all. A card that reported this result without the interval would be overselling it, and a doctor reading it would know. Read how this number was checked.
Please continue to exclude
CHS is a diagnosis of exclusion. There's no confirmatory test and no validated criteria, and the proposed criteria have not been externally validated at the bedside (Rotella et al. 2022). Here's what the literature says to keep checking for, and the tell for each one.
- Bowel obstruction and superior mesenteric artery syndrome (SMAS)Bilious emesis, a sudden change in a pattern that had settled into a rhythm, and rapid weight loss. CHS driven weight loss can cause SMAS on its own, not just sit next to it. Nine adolescents with both conditions together are published from Children's Hospital Colorado (Shanker et al. 2024), and a single case report shows how easily the acute presentation gets folded into the chronic one (Berken et al. 2022).
- Acute pancreatitisCheck lipase.
- Diabetic ketoacidosisCheck for it directly, especially in a first presentation.
- Adrenal insufficiency and pheochromocytomaOne published case sat behind a presumed cannabinoid hyperemesis diagnosis before an 8 cm adrenal tumor was found (Arendash et al. 2024).
- PregnancyRule it out before anything else changes.
- Raised intracranial pressureVomiting without nausea, a headache that's worse in the morning, or any new visual change.
- Acute intermittent porphyriaConsider it in an unexplained cyclic pattern with abdominal pain.
- GastroparesisOne published case ran this mistake the other way for two years, treating diabetic gastroparesis as CHS until cessation and a repeat workup sorted it out (Nana Sede Mbakop et al. 2023). Anchoring isn't a one way risk.
- Cyclic vomiting syndrome itselfThe two overlap heavily, and CHS criteria have never been validated against it.
- MalignancyEspecially when weight loss or anaemia doesn't fit the pattern.
Retching itself can injure. Watch for an oesophageal tear, and for spontaneous pneumomediastinum, which has been reported with no chest pain at all (Patel and Lippert, 2025).
No one has published a case series of patients harmed by a missed diagnosis here. This list is a differential to check against, not a record of documented failures, and it should be read that way. Equally, no one has measured how often a CHS diagnosis gets revised later, or whether the exclusion workup happens at all. Both absences are findings, not reassurance.
The medicines, as evidence, not orders
Ondansetron is usual care in every guideline this card cites, and it helps roughly a third of patients. HaVOC's own authors concluded that standard dose ondansetron "should no longer be used as the first line agent to abort emesis" in CHS, because repeating a dose that already failed rarely helps.
GRACE-4, the emergency medicine guideline built for this exact presentation, conditionally recommends haloperidol or droperidol added to usual care, on very low certainty evidence. The Johns Hopkins All Children's pathway asks for a basic metabolic panel and an ECG before IV haloperidol, and for potassium under 3 mEq/L to be corrected first, because prolonged vomiting depletes potassium, low potassium prolongs the QT interval, and both drugs prolong it further. Two independent published CHS sources show how far this can run: QTc readings from 477 to 566 ms alongside potassium of 2.7 and 3.3 (Kwag et al. 2022), and a QTc of 528 ms alongside potassium of 3.0 (Merino et al. 2025). Children's Minnesota's action points: a QTc above 460 ms in males or 480 ms in females calls for a repeat ECG within two weeks, and above 500 ms calls for a cardiology consult.
Droperidol's 2001 black box warning rests on adverse event reports concentrated at doses well above what emergency departments use for CHS. Only nine torsades cases have been attributed to droperidol across three decades, at any dose. Children's Minnesota still recommends an ECG before a repeat dose.
Topical capsaicin is conditionally recommended, on the strength of one underpowered 30 patient pilot trial (Dean et al. 2020). The Hopkins pathway states plainly that it hasn't been shown to reduce abdominal pain, and describes it as a vasodilator, not a painkiller. Combining it with hot water raises the risk of a burn.
Fluids: D5 normal saline with 20 mEq of potassium chloride per liter, at 1 to 1.5 times maintenance (Hopkins, Children's Minnesota).
Opioids are advised against, by both the Hopkins pathway and the AGA's 2024 update.
Longer term, the AGA's 2024 update names amitriptyline, at a minimal effective dose of 75 to 100 mg at bedtime, alongside cessation counselling. That recommendation is largely borrowed from cyclic vomiting syndrome, and hasn't been proven in CHS specifically.
Four pathways from hospitals that already treat this
A link to a peer institution's own published pathway is worth more than anything a patient can say. Here they are, exactly as the clinicians who wrote them use them.
- Johns Hopkins All Children's Hospital, CHS Clinical Pathway (2025-08-18)hopkinsmedicine.org/-/media/files/allchildrens/clinical-pathways/chs_pathway-2025-08-18.pdf
- Children's Minnesota, Cannabinoid Hyperemesis Syndrome Clinical Pathwaychildrensmn.org/references/CDS/cannabinoid-hyperemesis-syndrome-clinical-pathway.pdf
- Children's Mercy Kansas City, clinical pathwayscholarlyexchange.childrensmercy.org/clinical_pathways/57
- SAEM GRACE-4 summarysaem.org/publications/grace/grace-4
Full citations for every number on this page are on the evidence page, and the way they were checked is written up on how this was made.