Preventing aspiration after a stroke. The ASSIST tool.

In Australia each year around 60,000 people will experience a stroke. Half of them will be over the age of 75. And with out rapidly ageing population it has been forecast that over the next 15 years there will be an 70% increase in the number people who will have a stroke.

An national audit conducted in 2010 found that 47% of stroke admissions included a diagnosed dysphagia. These patients have an increased risk of aspiration, particularly within the first 72 hours.

It is recommended that swallow screening should occur ASAP and within 24hrs of admission before any food or oral medication is administered.
It should only be administered by staff trained in the procedure.
Any patient who fails screening should be referred to a speech pathologist for a more comprehensive assessment.
It is important to remember that as 40% of the population do not have a gag reflex, it is not useful as a screening tool.

Swallowing

Most of us swallow around 2000 times a day in order to empty the saliva from our mouth, and intake nutrition & hydration. In fact this act of swallowing which we all take for granted, is a highly complex sequence involving precise muscle control.
So complex, that over the 2–3 seconds it takes just to pass a food bolus from the back of the mouth to the stomach it requires assistance from the V, VII, IX, X, XI and XII cranial nerves.

The process of swallowing can be divided up into 3 main phases.

  1. The preparatory or oral phase. In which food is chewed, mixed with saliva and packaged up into a bolus.
  2. The Pharyngeal phase. In which the soft palate elevates to occlude the nasopharynx. The tongue pushes the bolus backwards as the pharynx and larynx move upwards to greet it. The epiglottis tips down to seal the airway. Finally, a whole bunch of pharyngeal constrictor muscles generate a peristaltic action to guide the bolus into the oesophagus (gravity pays almost no part in this, which is why you could happily survive hanging upside down in your closet.)
  3. The Oesophageal Phase. The upper oesophageal sphincter relaxes to let the bolus advance, after which peristalsis and relaxation of the lower oesophageal sphincter push it down into the stomach.

If that is all totally confusing, here is a simple video to perhaps help you visualise it.

ASSIST

The ASSIST (Acute Screening of Swallow in Stroke or TIA) tool provides a structured approach to assessing the effectiveness of swallow for a patient that has recently experienced a stroke.

Failure to adequately assess their ability to protect the airway as they swallow may lead to:
Laryngeal Penetration: in which a food/liquid bolus enters into the laryngeal vestibule (i.e. above the vocal cords). From this level, the bolus is still able to be cleared by coughing.
Aspiration: food or liquid enters the airway below the vocal cords. Colonisation of bacteria from the bolus or saliva may lead to Aspiration Pneumonia.
Silent Aspiration: As with aspiration, but occurs without the patient coughing or displaying any outward signs of difficulty.

The ASSIST screen consists of 5 sections. Each section must be passed in order to progress to the next.

If they fail a section (i.e. answer is YES), the assessment stops and they should be placed nil by mouth & referred for speech pathology assessment.

1. Is the patient able to:

  • Maintain alertness for at least 20 minutes?
  • Maintain posture/positioning in upright sitting?
  • Hold head erect?

2. Does the patient have any of these?

  • Suspected brain stem stroke.
    The incidence of dysphagia following a brainstem stroke has been reported to be between 70–80%.
  • Pre-existing swallowing difficulty
  • Facial weakness/droop.
    There is correlation between facial weakness and laryngeal weakness.
  • Slurred/absent speech.
    Dysarthria is significantly related to aspiration and silent aspiration.
  • Coughing on saliva.
    Inability to clear oropharyngeal secretions is a good predictor of aspiration risk.
  • Drooling
  • Hoarse/absent voice.
    Strong association with laryngeal penetration +/- aspiration.
  • Weak/absent cough?
  • Shortness of breath?

3. Test the patient with a sip (10 mL) of water and observe:

  • Any coughing/throat clearing?
  • Change in vocal quality?
  • Drooling.
  • Change in respiration/shortness of breath.

4. Observe the patient drink a cup of water:

  • Any coughing/throat clearing?
  • Change in vocal quality?
  • Drooling?
  • Change in respiration/shortness of breath?

5. Commence premorbid oral diet.

  • Nursing staff to observe patient with first meal. Should use meal similar to what the patient was eating prior to their stroke.

In summary, the ASSIST screen is a useful tool for stroke patients (only). It should be administered by nurses who have received formal training in its use. All findings should be documented in the patient notes.

You can download a pdf copy of the ASSIST tool here.

 


 

References

“Clinical Guidelines — Stroke Foundation – Australia”. 2016. Strokefoundation.Org.Au. https://strokefoundation.org.au/what-we-do/treatment-programs/clinical-guidelines.

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