Cannabinoid Hyperemesis Syndrome (CHS)

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🌿 Cannabinoid Hyperemesis Syndrome (CHS) is a syndrome of recurrent severe nausea, vomiting, and abdominal pain occurring in the setting of regular cannabis use. A classic clue is that patients often report temporary relief with hot showers or baths. The definitive treatment is stopping cannabis.

📖 What is CHS?

CHS is a clinical syndrome seen in people who use cannabis regularly, usually over a prolonged period. It causes repeated episodes of nausea, vomiting, retching, abdominal discomfort, poor oral intake, and dehydration. In the emergency setting it is often missed initially because cannabis is widely known for its antiemetic effects, so patients and clinicians may not immediately suspect it as the cause.

🧠 Why does it happen?

The exact mechanism is not fully understood. Cannabis can have antiemetic effects at low or intermittent exposure, but with repeated exposure it may paradoxically disturb the gut–brain axis, gastric emptying, autonomic signalling, and central emetic control. The hot-bathing behaviour may relate to transient modulation of thermoregulatory or pain pathways, which is why many patients find hot water surprisingly helpful during attacks.

👀 Typical clinical features

• Recurrent cyclic episodes of severe nausea and vomiting
• Regular cannabis use, often at least weekly and commonly daily
• Abdominal pain, often epigastric or diffuse
• Compulsive hot showers or baths that temporarily ease symptoms
• Periods of relative wellness between episodes
• Improvement after cannabis cessation

🪜 Clinical phases

🔎 When should you suspect CHS?

• Recurrent vomiting with no clear cause
• Repeated ED attendances or admissions with similar episodes
• Cannabis use history that may not be volunteered unless asked sensitively
• Symptoms poorly responsive to routine antiemetics
• Hot showers or baths giving symptom relief

⚠️ Important differential diagnoses

CHS is a diagnosis of suspicion, not a diagnosis of laziness. You must still exclude important alternative causes of vomiting and abdominal pain, especially on first presentation or if there are red flags.

• Gastrointestinal: bowel obstruction, cholecystitis, pancreatitis, hepatitis, peptic ulcer disease, gastroenteritis
• Neurological: raised intracranial pressure, intracranial pathology
• Metabolic / endocrine: DKA, adrenal crisis, uraemia, hypercalcaemia
• Functional / motility: cyclical vomiting syndrome, gastroparesis
• Pregnancy-related: hyperemesis gravidarum
• Toxicological / drug-related: alcohol, opioids, other ingestions

🚩 Red flags suggesting an alternative or additional diagnosis

• First presentation with severe abdominal findings
• Peritonism or marked focal tenderness
• GI bleeding
• Fever or sepsis features
• Neurological symptoms or reduced consciousness
• Unintentional weight loss, especially if older
• Abdominal mass or altered bowel habit
• Anaemia or abnormal liver tests

🧪 Investigations

There is no specific laboratory or imaging test that confirms CHS. Investigations are aimed at assessing severity, looking for complications, and excluding other diagnoses.

• Bedside / immediate: observations, capillary glucose, pregnancy test where relevant
• Bloods: U&Es, creatinine, bicarbonate, calcium, magnesium, LFTs, FBC, CRP as appropriate
• Urinalysis and ketones if indicated
• ECG if considering haloperidol or if electrolyte disturbance is possible
• Imaging only if history/examination suggests another pathology

💥 Complications

• Dehydration
• Acute kidney injury
• Electrolyte abnormalities, especially potassium disturbance
• Hypoglycaemia
• Acid–base disturbance
• Weight loss and malnutrition if episodes are prolonged

🏥 Acute management

Initial care is supportive and should follow standard emergency assessment principles. Correct dehydration, identify metabolic complications, and do not anchor too early before excluding important surgical or medical causes.

• IV fluids if dehydrated or unable to tolerate oral intake
• Correct electrolyte abnormalities
• Check glucose and treat hypoglycaemia if present
• Analgesia if needed, though opiates are often not especially helpful
• Usual antiemetics may be tried initially, but CHS is often resistant to standard antiemetic therapy
• Allow hot showering/bathing if safe, as this can relieve symptoms in some patients

💊 Treatments sometimes used when symptoms are refractory

• Haloperidol IM: suggested dose 0.05 mg/kg (max 5 mg)
• Topical capsaicin: 5 g of 0.1% cream applied to the abdomen

⚠️ Before haloperidol, obtain an ECG, check for QTc prolongation, and correct electrolyte abnormalities. Avoid haloperidol if the QTc is prolonged, or in patients with Parkinson’s disease or Lewy body dementia. Monitor for acute dystonia.

🧭 Long-term management

The key point is simple but important: the only definitive way to prevent recurrence is cannabis abstinence. Supportive, non-judgemental communication matters because many patients find the diagnosis hard to accept: cannabis may have helped nausea in the past, attacks can occur after years of use, and the episodes are not always linked to an obvious increase in consumption.

• Explain the likely diagnosis clearly and sympathetically
• Advise complete cessation of cannabis
• Provide written information if possible
• Signpost or refer for substance misuse support where appropriate
• Warn that symptoms usually recur if cannabis use restarts

🤰 Special situations

• Pregnancy: CHS may be mistaken for hyperemesis gravidarum, so careful history-taking is essential.
• Adolescents: CHS can occur in younger people too.

🧠 Clinical pearls

• Hot bathing is a clue, not a diagnostic test.
• Normal scans and routine antiemetic failure should make you think of CHS.
• Do not diagnose CHS without considering dangerous alternatives.
• Patients may under-report cannabis use unless asked in a calm, non-judgemental way.
• The syndrome is defined by recurrent vomiting + cannabis exposure + improvement with cessation.

📌 Summary

Cannabinoid Hyperemesis Syndrome should be suspected in patients with recurrent cyclic vomiting, abdominal pain, regular cannabis use, and relief with hot showers. There is no single confirmatory test; diagnosis rests on history, exclusion of other causes, and subsequent improvement after stopping cannabis. Acute treatment is mainly supportive, while cannabis cessation is the definitive therapy.