what are features of an ideal IV sedation agent
- anxiolytics
- sedation
- ease of administration
- non-irritant
- quick onset
- quick recovery
- no side effects
- amnesia
- low cost
what is the action of benzodiazepines
- acts on receptors in the CNS to enhance the effect of GABA = prolongs time for receptor repolarisation
- mimics effect of glycine (similar to GABA but on brainstem and spinal cord) on receptors = inhibitory neurotransmitter
- all BZD’s have benzene ring allowing attachment to receptors
what is GABA
- inhibitory CNS neurotransmitter in cerebral cortex and motor circuits
what are the respiratory effects of IV sedation
- CNS depression nd muscle relaxation
- decrease cerebral response to increased CO2
- synergistic relationship with other CNS depressants
- increased respiratory depression in already compromised pts
cardiovascular effects of IV sedation
- decrease BP by muscle relaxation decreased vascular resistance
- increased HR due to barareceptor reflex compensation for BP fall
what are side effects of IV sedation
- drug interactions = any other CNS depressant, erythromycin, antihistamines
- tolerance
- dependanc
what were the preparations of diazepam used
- had to be prepared as insoluble in water
- organic solvents (valium) = propylene glycol
- emulsified in soya bean oil (diazemulus)
- pain on injection
what is the half-life of diazepam
- 43 +/- 13 hours
- redistribution 1/2 life = 40 mins
- risk of rebound sedation
what dose of diazepam given
- 0.1-0.2mg/kg
why is diazepam now superseded by midazolam
- long recovery period
- unpredictable
at what pH is midazolam water soluble
- <4
- lipid soluble at physiologic pH allowing crossing of the blood brain barrier
why is midazolam painless on injection
- because it is water soluble
what dose of midazolam given
- 5mg/ml
difference between midazolam and diazepam
- more rapid onset and 2-3x more potent
- elimination 1/2 life 90-150 mins
- cheaper, safer and more reliable
where is midazolam metabolised
- in liver
- but also some exrta-heptaic metabolism in the bowel, so less affected by liver disease
why is a butterfly cannula not recommened
- cheap and easy to use but made of metal so can clot easily
- good for taking bloods
what type of cannula should be used instead
- one made of teflon
- more secure and rarely blocks
- has different colours for different sizes
cannulation sites
- dorsum of the hand = accessible, superficial and visible, poorly tethered and tend to move about while trying to cannulate them, affected by peripheral vasoconstriction
- antecubital fossa = need to be aware of brachial artery and median nerve, less stable, second choice
what topical aneasthesia is used
- for skin
- Ametop gel
- not sued very often
procedure for sedation
- pre-op pulse and blood pressure measurement taken
- high volume aspiration required
- need to monitor continually throughout = pulse oximeter, NIBP measurements every 5-10 mins, allows intervention before emergency, minimises risk
- 2mg bolus of drug given initially and monitor response then I’ve 1mg increments every 60 seconds until adequate sedation is achieved
- get approx 30-45 mins of sedation
- shouldn’t lose verbal communication throughout
- pt must stay for 60 mins after last increment given
what is the end point of administering drug
- slurred speech
- relaxed
- delayed response to commands
- willingness to accept treatment
- Verill’s sign = ptosis (drooping of eyelid)
- Eve’s sign = loss of motor coordination
what to do if respiratory depression emergency
- shake pt, head tilt jaw thrust to get more air in
- give 2l O2/min via nasal cannula
- if no improvement move to 5l/min with Hudson mask
- if still nothing reverse with flumazenil
features of flumazenil
- 500mcg in 5ml
- dose = 200mcg then 100mcg increments every 60 seconds until see a response
- shorter 1/2 life than midazolam so risk of rebound sedation
- brand name is Annexate
