UNCONTROLLED WHEN PRINTED
Introduction

Nitrates cause the relaxation of vascular smooth muscle resulting in:

  • Vasodilation
  • Peripheral pooling and reduced venous return
  • Reduced left ventricular and diastolic pressure (preload)
  • Reduced systemic vascular resistance (afterload)
  • Reduced myocardial energy and oxygen requirements
  • Relaxes spasm of coronary arteries

Also known as nitroglycerin

Pharmacology Review

Indications
  • Chest pain/discomfort of presumed cardiac origin not relieved by rest and reassurance with systolic BP > 90 mmHg.
  • Acute Cardiac Pulmonary Oedema with systolic BP >90 mmHg.
  • Autonomic Dysreflexia with systolic BP > 160 mmHg.
Contraindications
  • Hypersensitivity
  • Hypotension < 90 mmHg
  • Recent use of medications used for erectile dysfunction:
    • Sildenafil (Viagra®) or Vardenafil (Levitra®) or Avanafil (Spedra®) use in the previous 24 hours
    • Tadalafil (Cialis®) use in the previous 3 days
Precautions / Notes
  • Nitrates are an early intervention and should not be delayed until on the stretcher or inside the ambulance
  • Administer to the patient in a seated or semi-recumbent position
  • Prime the bottle before using it for the first time by pressing the nozzle 5 times, spraying it into the air
  • Do not shake GTN bottle prior to administration
  • Assess BP before every dose
  • Severe hypotension is an uncommon side effect
COVID-19 / Febrile Respiratory Illness
  • Crews should allow the patient to administer their own GTN spray wherever possible
  • Allow patient to self-administer GTN spray under crew direction; stand clear and wait a minute before approaching the patient
  • If you have to use SJA supplied Glyceryl Trinitrate (GTN Spray), assess whether it can be reused and wipe with Clinell wipe after use. Discard the MDI in the sharps bin if the patient is very unwell or highly symptomatic of infectious respiratory condition.
  • Note: If administering St John supplied medication, crews are NOT to leave the remainder of the medication with the patient. This is a violation of the St John WA poisons licence and the Medicines and Poisons Act 2014.
  • No vehicle should be considered non-operational due to not having GTN available; if GTN is not available step up to the next level of pain relief.  
Management
Cardiac Chest Pain
  • 400 microg (1 spray) sublingually.
  • If pain persists after 5 minutes and BP maintained, consider further sprays of GTN at 5 minute intervals
  • Should the first 3 doses provide some relief but symptoms persist, continue with further doses at 5 minute intervals if no contraindications
Acute Cardiogenic Pulmonary Oedema
  • 400 microg (1 spray) sublingually
  • If BP maintained, consider further sprays of GTN at 5 minute intervals
  • Should the first 3 doses provide some relief but symptoms persist, continue with further doses at 5 minute intervals if no contraindications
Autonomic Dysreflexia
  • 400 microg (1 spray) sublingually.
  • Repeat doses at 5 minute intervals until symptoms resolve or systolic BP < 160mmHg.
Special Considerations
  • Hypotension (rare)
  • Reflex tachycardia, palpitations
  • Flushing
  • Headache
  • Dizziness, fainting

References
References
Presentation
Spray bottle containing 200x atomised sprays
GTN
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Responsible Manager
Head of Clinical Services

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