Clinical Case 120: Vomiting VBG

Gday – I am off on leave this month – so here is a quick case from the files.

It’s an unusual VBG.  I will tell you a few features on the history and you need to work out the diagnosis and tell me how you are going to manage this!

The patient is a 25 year old chap who presents with 2 main symptoms: intractable vomiting and the near obsessive need to shower – long hot showers.  He has presented today because the ondansetron wafers that his GP prescribed have not been helping with the vomiting and his hot-water system is not able to keep up his need for hot showers!

He certainly looks dry and miserable.  His palms and soles are macerated from all the hot water.  He gets an IV sited and a quick blood gas is drawn….

So here are the questions:

(1) What is the diagnosis?

(2) Which meds will you try to truncate the vomiting?

(3)  What fluid will you choose to correct his metabolic derangement ??


thanks to @davebergie for the gas image



  1. The hot showers are a dead giveaway for cannabinoid hyperemesis.

    I know that hypochloraemic alkalosis is the classic use of saline, but I’d be tempted to use Hartmann’s anyhow, on the basis that you don’t want to bring up the Na too quickly.

  2. Great case Casey!

    1. Cannabinoid hyperemesis from chronic THC. Gas shows a metabolic alkalosis which fits the clinical history, with a very deranged metabolic profile. There is no respiratory compensation, but this patient could be hyperventilating for other reasons.

    2. I think I’d prefer to get on top of the potassium first, but in the interim IV ondansetron and metoclopramide is probably a good place to start, followed by droperidol as a second line.

    3. 100ml NaCl with 10mmol KCl, probably run at 200ml/hr via CVC. Also needs cardiac monitoring and hourly gases for the first few hours until the numbers improve.

    ^As an aside, what are thoughts on having to use a CVC for KCl at this rate? If I place one good cannula in the ACF and another in the GSV and run 10mmol of KCl an hour at both sites, what is the difference between this and a CVC?

    • Good call Jake. Certainly there is some hyperventilation secondary to the scenario and insightlessness!
      So I would use droperidol at a generous “antiemetic” dose to help stop vomiting and to calm the anxiety a bit. May aid the respiratory compensation?
      The low K may improve with correction of the alkalosis, so using an unbalanced saline with some K will bring it up by replacement and shifting it out the cells?
      If the ECG is OK and your ED nurses are happy I think peripheral K infusion is ok. It always seems like overkill to place a cvc purely for low K… If we can stop the vomiting and get some oral replacement happening this will be the longer term fix

      My orders for vomiting:
      Already had ondansetron
      Add droperidol 1 mg
      Then promethazine 25 -30 mg
      And dexamethasone 4 -8 mg

      Metoclopramide is a weak, short acting drug. No place here I say.

  3. a) cannabis hyperemesis syndrome – resulting in metabolic alkalosis secondary to vomiting with depletion of HCl, K, Na, Ca and impaired renal excretion of HCO3
    b) further ondansetron, benzos, perhaps steroids/anti-psychotics
    c) IV N/saline + 40mmol K initially (with some MgSO4 in a sideline) then repeat VBG to assess response and modify (i.e. change to CSL when Cl is at a reasonable level)
    d) spend some quality time educating this chap that smoking MJ is not making life any better… especially if he has to pay the electricity and water bill…

  4. Very interesting case – I haven’t heard about this syndrome before, so I learned something new today – cannabinoid hyperemesis syndrom, which occur after years of cannabis consume.
    Antiemetics – I would probably use dimenhydrinat, this has also has a sedative effect. Also some anxiolyticum like lorazepam – he is probably very agitated. Metoclopramid in young patients – I don’t like it too much. Ondasetron didn’t work and is mostly for chemotherapy stuff. Maybe Dexa ?
    After treating the acute situation, i would definitely involve a psychiatrist.
    So, as for the metabolic situation :
    – the patient needs to be admitted in a monitored bed. 12 Canal ECG asap => if tachycardia, U waves => CVC and start Kalium infusion : Start at 15 mmol/L. Maybe also Magnesium supplementation. Correction of Alkalemia will also help with rising the Potassium value. As fluid therapy – I would use 0,9% NaCl 2-3 Liters with Sodium monitoring. Afterwards Ringer. He has a chronic hyponatremia, we don’t know his Alkoholconsum status, but if he drinks also alcohol, could be at a higher risk for ODM. I would aim for a Sodium of 128 after the first 24h.
    How would you explain a S”v”O2 of 86% ? Hot showers => vasodilatation, somehow like a distributive situation with lower O2 Extraction?

    Very interesting. Greetings from Hamburg, Germany !

  5. Adam Michael says

    G’day Casey!

    I think we all agree on the Dx

    I’d be tempted to use droperidol as well, as long as the QTc is OK with that degree of hypokalaemia. Ondansetron is always worth trying too. Otherwise midazolam is a passable antiemetic along with its other benefits here.

    For Fluids, presuming he is not shocked, I’d go saline 1L with 20mmol KCl given peripherally over the 1st hour then reassess incl repeat VBG at this point. I’d try hard to avoid a central line. These patients present repeatedly and if they get repeated central lines you’ll be asking for central venous stenosis or other complications…not to mention that they’ll keep running to the shower with their central line in and get it wet!

    • Good points about the often unthought of complications of CVCs
      Do you think QTc is an issue in the light of the DORM2 trial?
      Sure hypo kalmia is an issue – but is droperidol more likely than any other agent to cause to torsades?

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