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Dr. Alain F. Kalmar, MD, PhDDep. Of Anaesthesia
University Medical Center GroningenThe Netherlands
Sedation 2012
ASA definition of levels of sedationCopyright® [1999] American Society of Anesthesiologists
What is adequate sedation ?
Benefits of sedation
Facilitates & expedites proceduresReduces discomfort & unpleasant
memoriesAllows for avoidance of invasive airway
interventionCost -effectivePromotes early recovery & discharge Improves overall patient satisfaction
Prior to sedation : Patient history
Patient sensitivity to sedatives/analgesics patient risk of respiratory/cardiopulmonary
complications- Cardiopulmonary disease : decreased drug dosage- Hepatic /renal disease : Altered pharmacokinetics- Medication interactions
Patient allergiesAlcohol / Substance abuse : may
increase/decrease effectsTobacco use : increase airway irritability ;
bronchospasm Prior adverse reactionsdifficulty in managing complications
Prior to sedation : Patient history
Airway assessment - Airway class
- Mouth opening
- Thyromental distance
Lam B et al. Thorax 2005;60:504-510
Patient education helps alleviate concerns associated
with conscious sedation.Prevention of “Awareness experience” Key points : duration of sedation
potential for sedation failure
alternatives to sedationpotential for adverse
eventsMonitoring
Informed Consent
Preprocedural ASA Fasting Guidelines
To Minimize Aspiration Risk
Substance Ingested
Minimum Fasting Period (hours)
Clear Liquids 2
Breast Milk 4
Infant Formula 6
Food 8
Required equipmentOxygenSuctionCrash cart with ACLS drugsDefibrillatorBag/Valve/Mask device ; ventilatorOral & nasal airwaysETT’s sizes 5.0, 6.0, 7.0, 8.0Laryngoscopes with Mac 3, 4 and Miller 2, 3
bladesReversal agents
Optimal Sedation Pt maintains consciousnessIndependent maintenance of airwayRetains protective reflexes (swallow & gag)Responds to verbal & physical commandsIs not anxious & has acceptable pain controlHas minimal change in baseline vital signsRemains relatively cooperativeHas mild amnesiaRecovers to baseline safely & promptly
Farmacology for Conscious Sedation
propofolbarbituratesbenzodiazepines
inhalational an.
opiates
Local an.
Pharmacology For Conscious Sedation
Allows the patient to be calm, comfortable and cooperative.
Mostly, a combination of hypnotics and opiates is used.
Opioids AnalgesiaBenzodiazepines or other sedatives
Sedation, anxiolysis, and amnesia. Sedative drugs do not provide analgesia.
A drug should be allowed to exert its full effect before administering additional doses or another drug.
When combining opioids and sedatives, administer the opioid first to ensure the patient receives analgesia prior to painful stimulation.
Conscious Sedation :Monitoring
Patients must be monitored during moderate sedation. The person monitoring the patient can not have additional assignments.
Heart rate and Oxygenation : continuously by Pulse Oxymetry
Respiratory rate & pulmonary ventilation Clinical endpoints for conscious sedation may include a respiratory rate of 10-12 in an adult and a slurring of speech.
Blood pressure and EKG
Does this provide safe conditions ?
Observational study (University Hospital Groningen 2011).
Sedation for colonoscopy : Business as usualMidazolam / Pethidine230 patients breathing room air.Standard monitoring of ECG, NIBP, SpO2, HR
Additional recorded parameters : PetCO2, PtcCO2, BIS
All data were recorded for subsequent analysis.
Main safety parameters :
Oxygenation (SpO2)
Ventilation (PEtCO2 / PTcCO2 )
Depth of sedation (BIS) – Risk of pulmonary aspiration
Blood Pressure (MAP)
65
70
75
80
85
90
95
100
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
SpO2
Time (min)
SpO2 < 90 : 36% (226 sec)
Does this provide safe conditions ?
SpO2 Median10th / 90th percentile
50
55
60
65
70
75
80
85
90
95
100
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
BIS
Time (min)
BIS < 75 : 29% (224 sec)BIS < 70 : 17% (126 sec)
Does this provide safe conditions ?
BIS
0
20
40
60
80
100
120
140
160
180
200
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
MAP
Time (min)
MAP < 70 : 36% (564 sec)
Mean Arterial Pressure
Does this provide safe conditions ?
0
1
2
3
4
5
6
7
8
9
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TcCO2
Time (min)
Does this provide safe conditions ?
Incidence SpO2 < 90 : 36%
PTcCO
2
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
EtCO2
Time (min)
Does this provide safe conditions ?PEtCO
2
Does this provide safe conditions ?
Hardly !What goes wrong ?
Insufficient attention of the sedation caregiver ?
Insufficient knowledge on pharmacology of Midazolam / Pethidine ?“If a combination of opioids and sedatives is used, the opioid should be given first and allowed time to become maximally effective before any sedative is added.”
U.K. ACADEMY OF MEDICAL ROYAL COLLEGES
Insufficient awareness of the depth of anesthesia ?
Conclusion :
Conscious sedation should be performed by a skilled personnel with adequate knowledge of anesthesia, pharmacology and basic and advanced life support. Anesthesiologists or Trained sedation practitioners
Individual who monitors the sedated patient should do this as his/her sole task and not have other concurrent responsibilities.
Choice of medication (Pethidine /Midazolam) ?
Conscious Sedation 2012 ?
Preference to short-acting drugsA quick therapeutic response on a rapid change of peri-operative situation without “hang-over” effects.
Take into account population variabilityTarget controlled infusion (TCI) instead of mg/kg/hr
Attempt to individualize dose-response relation.Careful titration with knowledge of pharmacology
Suitable Opiates ?Time to Peak-effect
Minutes since bolus injection
0 2 4 6 8 10
Per
cent
of
peak
eff
ect s
ite
opio
id c
once
ntra
tion
0
20
40
60
80
100
fentanyl
sufentanil
alfentanil
remifentanil
Context sensitive Half-TimeTime for the effect site concentration of a drug
to fall 50% after a variable length infusion
Egan et al. Anesthesiology 1993, 79(5) : 881-892.
End of procedure
* Discontinuation of alfentanil infusion/no more fentanyl boluses
Remifentanil
Time
AnalgesicEffect
*
End of Procedure
Fentanyl
Alfentanil
Hypnotic-based procedure ?opiate-based procedure ?
Propofol-Remifentanil interaction
0
1
2
3
4
5
6
7
8
9
10
0 2 4 6 8 10 12 14 16
Blood propofol (µg/ml)
Pla
sm
a r
em
ife
nta
nil
(ng
/ml) Adequate anesthesia
Awakening
0
1
2
3
4
5
6
7
8
9
10
0 2 4 6 8 10 12 14 16
Blood propofol (µg/ml)
Pla
sm
a r
em
ife
nta
nil
(ng
/ml) Adequate anesthesia
Awakening
Sedation for lung-reduction valve placement
Patient characteristics :ASA 4High-grade emphysema patientsOften important comorbidity
Requirements :Preserved hemodynamicsPreserved ventilation with spontaneous
ventilationAllowing bronchoscopy and intrabronchial valve
placementFull-coöperative patient for diagnostic and
therapeutic reasons.
Sedation for lung-reduction valve placement
Preferred technique :Conscious sedation with Propofol/Remifentanil
TCI-guided.Take into account pharmacology of agents
1. Start Remifentanil CeT 1 ng/ml
2. Wait 60 seconds until clear subjective effects3. Start Propofol CeT 1 ug/ml
4. Wait for sedative effect to occur5. Carefully titrate drugs depending on patients
reports (anxiety /pain)Keep talking with patient (Population variability)
Sedation for lung-reduction valve placement
Advantages :Fully-coöperative patient, good tollerance for the
procedureOptimal conditions for the procedurePreserved hemodynamicsFast recovery (extremely important for these
high-risk patients)High patient satisfaction (complete amnesia of
the procedure)Fast patient turn-over
Conclusion 2012
TCI Remifentanil / Propofol- Very advantageous farmacokinetics.- Good safety profile
Future …Dexmedetomidine ?Patient controlled sedation ?
Similar to principles of PCA, based on patient feedback
Target Controlled Sedation ?(i.e. BIS guided propofol administration)
Questions ?
