Stemetil Stiffness

Dr Gavin Ng

Emergency Physician

Editor: Dr Hector Thomson

THE CASE

You receive an ambulance notification on Saturday morning.

“We are coming to you in 10 minutes. We attended a 70-year-old gentleman with positional vertigo symptoms and gave him 12.5mg IM procholorperazine (Stemetil). His initial GCS was 14 – it is now 3. He has also desaturated to 76% on room air.”

Question One: What are your differential diagnoses on receiving this call-out? How would you prepare for the patient’s arrival?

1. Given the history of vertigo and sudden loss of consciousness, it is important to consider an intracranial catastrophe – specifically, cerebellar haemorrhage or posterior circulation ischaemic stroke.

2. A basilar artery occlusion is a crucial diagnosis to consider, as patients may present with coma if ischaemia occurs in the pontine area1.

3. The 3S mnemonic (staff, stuff and space) can be used as an aide memoir in your preparation

   1. Staff – appropriately trained staff to manage the patient’s airway

   2. Stuff – intubation drugs and equipment

   3. Space – Empty out a resuscitation bay

The patient arrives shortly thereafter. There are two striking features on the clinical examination – he has widespread generalised erythema over his entire body, and he is noted to have significant rigidity in his lower limbs bilaterally. His other vital signs are as follows:

HR 100 BP 160/110   RR 24 SpO2 100% 15L non-rebreather   T 35.7   GCS 3

He is noted to have trismus, and bilateral peri-orbital oedema as well. A wheeze is noted on auscultation.

Question Two: How does this change your differential diagnosis?

1. The presence of trismus and bilateral lower limb hypertonia suggests an acute dystonic reaction (possibly secondary to prochlorperazine).

2. The widespread erythema and wheeze suggest possible anaphylaxis. It may also be a feature of anti-cholinergic toxicity.

Question Three: What kind of drug is prochlorperazine?

Prochlorperazine is a first-generation (typical) anti-psychotic agent(2). It mainly blocks on central D2 dopamine receptors, but also blocks histaminergic, cholinergic and noradrenergic receptors.

Question Four: What is the pathophysiology of this reaction?

Acute dystonic reactions are a subset of extra-pyramidal syndromes, and are related to an imbalance between dopamine and muscarinic receptors in the CNS. Whilst the exact mechanism remains unclear, one proposed mechanism is over-stimulation of acetylcholine receptors in the basal ganglia(5).

Commonly used medications in the ED that can precipitate dystonic reactions are metoclopramide, haloperidol and prochlorperazine(3). Important the reaction does not indicate an overdose and can occur within therapeutic doses.

Question Five: What are the clinical features of an acute dystonic reaction?

Whilst there are no pathognomonic features, there are several manifestations of this condition including(4):

1. Oculogyric crisis: spasm of the extra-orbital eye muscles causes upwards and outwards deviation of the eyes.

2. Torticollis: the head is turned to one side.

3. Opisthotonus

4. Macroglossia: the tongue protrudes due to spasm (but generally does not swell)

5. Bucco-lingual crisis: trismus, grimacing and dysarthria may be seen

6. Laryngospasm

7. Truncal and limb spasticity

A good example of this can been viewed on YouTube, here.

Question Six: How would you manage this patient?

Benztropine (a centrally-acting anti-cholinergic medication) is typically used to managed acute dystonic reactions. Response is rapid – most patients feel better by 5 minutes, and are symptom-free by 15 minutes. The dose can be repeated a second time after 10-20 minutes. If there is no improvement, the diagnosis is probably incorrect.

A typical dose may be Benztropine 2mg IV (or IM) as a slow injection, repeat once in 20 minutes.

If symptoms improve but are slow to resolve following benztropine administration, then benzodiazepines may be used as they help relieve muscle spasm and anxiety. They are best used later in the patient’s presentation – early use may cause diagnostic confusion. Possible doses are:

• Midazolam 1-2mg IV or IM

• Diazepam 5 to 10mg IV or oral

If benztropine is not available, then antihistamines with anti-cholinergic activity may be used. Possible regimes include:

• Promethazine 25 to 50mg IV/IM

• Diphenhydramine 50mg IV/IM

In this scenario, the patient was given three doses of 2mg Benztropine IV.

Anaphylaxis was also treated concurrently with the following:

• Adrenaline 500 micrograms IM x3 doses

• Hydrocortisone 250mg IV

• Nebulised salbutamol 5mg x1 dose

Apart from the acute treatment, don’t forget to add on a tryptase (to look for anaphylaxis), and to add on an allergy notification to the patient’s chart! He should not receive prochlorperazine (or other anti-dopaminergic drugs) again.

The patient was admitted to the hospital for observation over 24 hours, and then discharged uneventfully the following day.

Some patients may require Benztropine 1-2mg orally BD for 48-72 hours to prevent relapse.

References

1. Caplan, L.R. (2022). Posterior Circulation Cerebrovascular Syndromes. In J. F. Dashe (Ed.), UpToDate. Retrieved March 5, 2023 from https://www.uptodate.com/contents/posterior-circulation-cerebrovascular-syndromes

2. Din, L., & Preuss, C. V. (2022). Prochlorperazine - StatPearls - NCBI Bookshelf. Retrieved March 4, 2023, from https://www.ncbi.nlm.nih.gov/books/NBK537083/

3. Lavonas, E.J. (2021). First-generation (typical) antipsychotic medication poisoning. In M.Ganetsky (Ed.), UpToDate. Retrieved March 5, 2023 from https://www.uptodate.com/contents/first-generation-typical-antipsychotic-medication-poisoning

4. Campbell D. The management of acute dystonic reactions [Internet]. NPS MedicineWise. 2001 Retrieved march 5, 2023 from https://www.nps.org.au/australian-prescriber/articles/the-management-of-acute-dystonic-reactions

5. Eskow Jaunarajs KL, Bonsi P, Chesselet MF, Standaert DG, Pisani A. Striatal cholinergic dysfunction as a unifying theme in the pathophysiology of dystonia [Internet]. Progress in neurobiology. U.S. National Library of Medicine; 2015. Retried march 5, 2023 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420693/

Gavin Ng

Emergency Physician

Gavin Ng is an Emergency Physician and Co-Director of Emergency Medicine training at The Alfred. Gavin has worked in a variety of clinical settings, ranging from metropolitan EDs to regional areas in Victoria. His clinical interests are Critical Care Medicine and Trauma medicine, and he has previous experience working as a Trauma Fellow at Alfred Health. He is also a current ALS2 (Advanced Life Support Level 2) instructor. He also has a passion for education – he has previously been involved in teaching junior medical staff through the Northern Clinical School.