IV sedation techniques Flashcards
What would be the features of the ideal IV sedation agent?
Anxiolysis (main aim of sedation)
Sedation
Easy to administer
Non-irritant
Quick Onset
Quick recovery
No adverse side efffects
Amnesia
Low cost
How do Benzodiazepines act?
Acts on receptors in the CNS:
Enhance effect of GABA (inhibitory neurotransmitter) in cerebral cortex and motor circuits- prolongs time for receptor repolarisation
Mimics effect of glycine (inhibitory) on receptors in brainstem and spinal cord
What component of benzos allow attachment to receptors?
Benzine ring
What are the respiratory effects of benzodiazepines
Respiratory depression via:
CNS depression and muscle relaxation
Decrease in cerebral response to increased CO2 (drives breathing)
Synergistic relationship with other CNS depressants
When is the respiratory depression effects of Benzos increased?
If patient’s respiratory system already compromised
What are the cardiovascular effects of benzos?
Decreased BP- muscle relaxation decreases vascular resistance
Increased HR- baroreceptor reflex compensates for BP fall
Which drugs to benzos interact with
Other CNS depressants
Erythromycin
Antihistamines
How are issues with tolerance and dependence in patients taking benzos combatted?
Only given in 2 week prescriptions
-> One off sedation appointments will not cause this (but may be seen in patients who already abuse benzos)
What is the issues with patients disclosing sexual fantasies while sedated, how is the practitioner protected?
Higher dose increase chance
-> Sedationist must never be alone with patient
What are the advantageous properties of midazolam?
Water soluble (at pH <4)
Lipid soluble at physiological pH- allows crossing of BBB
Painless injection
Rapid onset (2-3 times more potent that diazepam)
Elimination half life of 90-150mins (quicker recovery than diazepam)
Metabolised in liver
Additional extra-hepatic metabolism in bowel (better for those with liver disease)
More reliable
What caused pain on injection when using diazepam preparations in past?
propylene glycol (this is because diazepam is water insoluble and requires another liquid)
What pH is Midazolam
3.5
What quantity do midazolam preparations come in?
5mg/5ml
Who are the members of the sedation team?
Operator/Sedationist
Second trained person- nurse
Runner
What are the requirements of the sedation team?
All must have appropriate sedation training
Must be able to manage sedation related complication and emergencies
Annual ILS training and sedation scenario training
What type of cannula is used in sedation?
In-dwelling
-> Butterfly is not recommended (easily dislodged, issues with clotting and obstruction)
What are the advantages of the in-dwelling cannula
More secure
Made of teflon (preferred to metal)
Rarely blocks
What sites can be used for cannulation?
Dorsum of hand
Antecubital Fossa
What are the advantages of using the dorsal of the hand for cannulation?
Easily accessible- patient likely to be clothed
Superficial and Visible
What are the disadvantages of using the dorsum of the hand?
Poorly tethered- vessels move around
Affected by peripheral vasoconstriction- may need to warm hand up
When is the antecubital fossa used?
As a second choice to dorsum of the hand if you cannot find a vein there (bigger vessels)
-> Less stable, be careful to stay lateral to brachial artery and median nerve
What can be used as a topical anaesthetic prior to cannulation?
Ametop gel or EMLA
-> used less now as patient would need to apply before appointment
What monitoring equipment is used by staff in sedation?
Pulse oximeter
Non-invasive blood pressure device- measures every 5-10 mins
-> acts as early warning system to allow intervention before an emergency can develop and minimise risk
What is used to reverse patient in an emergency situation?
Stop if values get worrying
Administer flumazenil (antagonist for benzos) and provide means of ventilation
How is midazolam administered
0.5-1mg bolus- then 1 mg ever 60 seconds until suitably sedated (max of 7.5mg)
What are the signs of the end point for sedation
Slurring and slowing of speech
Relaxation
Delayed response
Willingness to accept treatment
Verrill’s sign- ptosis
Eve’s sign- loss of motor coordination
-> Patient should NOT lose verbal communication
How can Eve’s sign be checked
Ask patient if they can place finger on nose with eyes closed
What factors can affect dose of midazolam required to achieve sedation (therapeutic dose)
Sleep
Alcohol
Stress
Other drugs
age
How long should sedation last
30-45mins
What do you do if you notice patient oxygen saturation is dropping?
Ask them to take deep breaths and see if it improves
What happens in the recovery phase of sedation?
Escort can be with patient (can act as second person)
Patient can leave 60 mins after first increment- so long as they can walk unaided
Cannula must be removed before leaving (infection risk)
Escort is given post-op instructions
What are the steps in dealing with respiratory depression
1.Talk, shake, hurt
2. Place in head tilt, chin lift, jaw thrust position
3. Administer oxygen via nasal cannulae (2L/min)
4. If this fails administer oxygen via Hudson mask (5L/min)
5. Administer Flumazenil
6. Use BVM and check airways
What quantity does the preparation of flumazenil come in?
500 micrograms in 5ml
How is flumazenil administered? What are the issues with it?
200mcg then 100mcg every 60 seconds until response
-> has shorter half-life than midazolam so patient could re-sedate (keep for longer)
