What is it ?
The American College of Emergency Physicians (ACEP) defines procedural
sedation as "a technique of administering sedatives or dissociative agents
with or without analgesics to induce a state that allows the patient to
tolerate unpleasant procedures while maintaining cardiorespiratory
function. Procedural sedation and analgesia (PSA) is intended to result in a
depressed level of consciousness that allows the patient to maintain
oxygenation and airway control independently.
Response to verbal stimulation is normal.
Cognitive function and coordination may be impaired.
Ventilatory and cardiovascular functions are unaffected.
Moderate (formerly conscious) sedation
Depression of consciousness is drug-induced.
Patient responds purposefully to verbal commands.
Airway is patent, and spontaneous ventilation is adequate.
Cardiovascular function is usually unaffected.
Depression of consciousness is drug-induced.
Patient is not easily aroused but responds purposefully following repeated
or painful stimulation.
Independent maintenance of ventilatory function may be impaired.
Patient may require assistance in maintaining a patent airway.
Spontaneous ventilation may be inadequate.
Cardiovascular function is usually maintained.
Loss of consciousness is drug-induced, where the patient is not able to be
aroused, even by painful stimulation.
Patient's ability to maintain ventilatory function independently is impaired.
Patient requires assistance to maintain patent airway, and positive pressure
ventilation may be required because of depressed spontaneous ventilation
or drug-induced depression of neuromuscular function.
Cardiovascular function may be impaired.
A light anaesthetic ?
Guedel in 1937, first widely accepted guide to depth of anaesthesia (I – IV)
Artusio later divided stage 1 into 3 planes, first plane no analgesia no
amnesia, second amnesia no analgesia and 3rd both analgesia and amnesia
Entropy and Bis , (around 60 – 80 )
When is it used?
Painful procedures, esp children
Radiological procedures, eg CT , MRI
Foreign body removal
Suturing , and other procedures
GA in theatre with Image intensifier and anaesthetic support
Just don’t do it
Your own level ability and experience, and that of your assistants
The state of the department, resource hungry procedure
Availability of appropriate area and equipment
Plan for it all to go wrong, don’t just have a plan A
ASA grade (3+), co-morbidities
Obesity or pregnancy
Allergies , previous anaesthetic
Am I happy to RSI this patient?
Short painful procedure (<20 mins )
ASA 1 and 2
How important is it?
Several studies studies , with several different agents , maybe not as
important as we once thought 1,2,3
Carers / parents
Documentation, what was given, how much when and by whom and any
Post sedation observation
Instructions on driving and alcohol
Minimum 3 trained staff
Practitioner administering sedation must be familiar with the agent,
experience and able to monitor and detect problems
Equipment (ACEM minimum)
Adequate room and appropriate lighting
Tiltable table, preferable but not mandatory
Means to inflate the lungs, readily available airway equipment
Ready access to ECG and defib
Means to summon assistance
ET CO2 monitoring
Amnesic, but no analgesia
Fairly rapid and predictable
Slower recovery than propofol
Reversable (big advantage for some operators )
Duration of action 20 – 40 minutes (at low doses)
IV or IN popular, but all routes
What could possibly go wrong ?
Loss of airway reflexes
Depression of respiration
Drug interactions, adverse reactions and anaphylaxis
Variations in expected response to drugs used
Possible deeper sedation than expected
Risks from the procedure
Good idea or not
How is it best achieved?
Nasal prongs, hudson, non-rebreather mask, self inflating bag with reservoir,
CPAP mask ?
Preoxygenation or denitrogenation
Lungs can hold much more oxygen than blood (about 20 times)
Lungs full of air equals about 0.4 l available oxygen (FiO2 0.21 x 2l)
Lungs full of oxygen equal 2 l (FRC x FiO2)
Body oxygen consumption about 250 ml under normal conditions
All the oxygen reserve is provided by preoxygenation
Rate of preoxygenation is a predictor of rate of deoxygenation, as represents
the relationship between alveolar minute volume FRC
Technique big breaths v TV x longer time
Really should measure FeO2 (>90%)
Prolonging DAWD, apnoiec oxygenation
Preoxygenation, position, technique, and method of O2 delivery
Duration of apnoea without desaturation
DAWD = time from onset of apnoea to saturation <90%
DAWD depends on
Initial oxygen reserve
Rate of O2 consumption
Ongoing apnoeic oxygen delivery or not
<1 minute – 8 minutes without apnoeic oxygenation depending on various
Increase rate of consumption, fever, tachycardia
Study Endpoint Tidal Volume
4 (in 30 sec)
8 (in 60 sec)
Gambee DAWD 8.9 (1.0) min 6.8 (1.8) -----
FeO2 % 88 (5) % 80 (5) 87 (3)
Pandit FeO2 % 92 (1) % 83 (2) 91 (4)
Gagnon FeO2 % 89 (3) % 76 (7) -----
Gambee et al Preoxygenation techniques: comparison of three minutes and four breaths. Anesth Analg 1987; 66: 468–70.
Nimmagadda et al. Preoxygenation with tidal volume and deep breathing techniques: the impact of duration of breathing and fresh gas flow. Anesth Analg 2001; 92: 1337–41.
Pandit etal Total oxygen uptake with two maximal breathing techniques and the tidal volume breathing technique: a physiologic study of preoxygenation. Anesthesiology 2003;
Gagnon et al When a leak is unavoidable, preoxygenation is equally ineffective with vital capacity or tidal volume breathing. Can J Anesth 2006; 53: 86–91.
High flow nasal vs high flow mask oxygen delivery: tracheal gas concentrations through a
head extension airway model
2002 Open Forum Abstracts, Am Assoc Resp Care
High flow nasal cannula delivery > non-rebreather mask at equivalent flows
250 ml oxygen leaving lung per minute
10 – 20 ml CO2 entering lung
Results in slightly subatmospheric alveolar pressure
Net gas flow 240 ml / minute
Techniques of O2 delivery
10 Fc catheter into nasopharynx (distance of mouth angle to ear tragus)
Paediatic south facing Rae tube to angle of the mouth
“apneic diffusion oxygenation, diffusion respiration, and mass flow ventilation”
Hypotension under anaesthesia, sedation
? Best agent or way to resolve ?
Elevate legs, fluid bolus,. Metaraminol ?
Sux low dose
Sux full dose
Make sure its clear
What was given, when, how much, problems encountered
How long to stay monitored
How long until fit to discharge
Driving, avoidance of alcohol
1 Treston G. Prolonged pre –procedure fasting time is unnecessary when using titrated intravenous ketamine for paediatric
procedural sedation. Emergency medicine Australasia 2004; 16(2): 145-150
2 Agrawal D, Manzi SF, Gupta R et al. Preprocedural fasting state and adverse events in children undergoing procedural sedation
and analgesia in a paediatric emergency department. Annals of emergency medicine 2003: 42(5) 636-646
3 Roback MG, Bajaj L, Wanthan JE, et al. Preprocedural fasting and adverse events in procedural sedation and analgesia in a
paediatric emergency department are they related? Annals of Emergency Medicine 2004; 44(5): 454 - 459
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