Inhalation Sedation II Flashcards
What is the spectrum of pt management?
TLC LA Suggestion/ hypnosis IHS Oral sedation IV sedation GA
Advantages IHS?
Non-invasive Rapid onset and recovery Minimal impairment of reflex No fasting required Adult pt don't need escort Some analgesic effect
Disadvantages IHS?
Lack of potency of nitrous oxide Expensive equipment Requires clear nasal airway Intrusion make into operating field Chronic staff exposure Lack operator control
What patients are suitable?
Unpleasant tx Anxious pt Needle phobics Those gag easily - reflex dulled Medically compromised - unsuitable IV
What are general contraindications?
Nasal obstruction - can't breath in nitrous oxide Severe pulmonary conditions Cyanosis due cardaic/ respiratory diseae Inability to communicate/ co-operate Pregnancy Masks interrupt operative work
What drug contraindicates use of IHS?
Methotrexate
Why is methotrexate a contraindication to providing IHS
Nitrous oxide increase risk of methotrexate toxicity - drug interaction
When is methotrexate used?
Autoimmune conditions e.g rheumatoid, psoriasis, neoplastic disease
What medical conditions contraindicate IHS?
Muscle wasting - myasthenia gravis
Claustrophobia
Recent ophthalmic surgery using gas
Any air entrapment in body e.g head injury/ pneumothorax
Why is muscle waisting contraindication IHS?
Drug relax muscle to point respiratory depression
Why are those w/ psychiatric disorders contraindicated to have IHS?
Struggle understand expectations
Hard breath through nose calm and consistently
Ideal properties sedating agent
Alleviate anxiety Degree amnesia and analgesia Maintain protective reflex Prolong operating time Rapdily effective Easily eliminated No side effects Easily administered
What is oxygen?
Clear, colourless and odourless gas
What state is oxygen in when in the cylinder?
Gaseous
What colour is oxygen cylinder?
Black w/ white shoulder
What is nitrous oxide?
Sweet smelling, colourless gas
What colour is nitrous oxide cylinder
Blue
What state is nitrous oxide in in cylinder?
Liquid when under pressure
How know amount of nitrous oxide in cylinder?
Weigh
MAC nitrous oxide?
105% - weak anaesthetic
What are systematic effects nitrous oxide?
Depression CNS
Slight depression CVS at high []
Effects chronic exposure to nitrous oxide?
Increased risk of miscarriage
Decreases fertility
Pernicious anemia due issue via B12 synthesis
What is entonox?
50% oxygen and 50% nitrous oxide
Why doe entonox need to be used at room temp?
Cause uneven distribution of gas within cylinder
What are diff planes of nitrous oxide analgesia?
Plane 1 - moderate sedation
Plane 2 - dissociation sedation and analgesia
Plan 3 - total analgesia
What % for plane 1?
5-25%
What % for plane 2?
20-50%
What % for plan 3?
50%+
What is MAC?
Minimum alveolar concentration - measure anaesthetic potency
What is MAC of nitrous oxide?
105%
When is MAC reduced?
elderly
by other sedative - alcohol, antihistamines, benzodiazepine
What is theory of diffusion hypoxia?
Rapid elimination of nitrous oxide into lungs dilutes oxygen within alveolus lowering alveolar oxygen concentration, reduces ventilatory drive causing hypoxia/ hyperventilation
How to prevent diffusion hypoxia?
Routine administration 100% oxygen for 3-5 mins post -op
How to reduce occupations exposure?
Improve ventilation
Active and passive scavenging
Regular machine chekcs
Safety features of IHS?
Pinned system Colour coded cylinders and tubing Oxygen fail-cut out 30% minimum oxygen Oxygen flush Reservoir bag Scavenging
