5 Goals of induction
- ) provide smooth transition from consciousness to unconsciousness
- ) provide hemodynamic stability
3) secure airway as necessary
4) provide optimal intubating conditions if applicable
5) GA: Amnesia, analgesia, muscle relaxant, and hemodynamic stability
Considerations for choice of induction drugs
- Speed of onset
- Duration of effects
- Pain on injection
- Myoclonus
- Cv effects
- CBF effects, Drug specific side effects
7 indications - Contraindications
- Chart on Evers pg.1008
Ketamine
- Speed of onset =fast
- Duration of effect = short
- Pain on injection = no
- Myoclonus = yes
- Cardio vascular side effects: Tachycardia, hypertension, myocardial depression, pulmonary hypertension
- Cerebral Blood Flow = increased
- Specific Drug side effects = Psychedelic in sub-anesthetic doses, bronchodilator, may have Neuro protective properties
- Recommend for = Asthma, Trauma, Cardiac tamponade
- Avoid = Pulmonary hypertension, Psychotomimetic side effects, Tachycardia and/or hypertension, may be hazardous if intracranial compliance is decreased
Etomidate
- Speed of Onset = Fast
- Duration of effect = short
- Pain on injection = yes
- Myoclonus = yes
- Cardiovascular effects = Minimal
- Cerebral blood flow = decreased
- Drug specific side effects = inhibits cortisol biosynthesis
- Recommended for = Hemodynamic compromise of all kinds
- Avoid for = May interfere with cosyntropin stimulation testing
Proposal
- Speed of onset = fast
- Duration of effect = short
- Pain on injection = yes
- Myoclonus = yes
- CV side effects = hypotension, vasodilation
- CBF = decreased
- Drug specific side effects = May reduce incidence of postoperative nausea
- Recommended for = ambulatory surgery, LMA insertion
- Avoid for = Hemodynamic compromise
Fentanyl Analogs
- Speed of onset = fast
- Duration of effects = variable
- Pain on injection = no
- Myoclonus = yes
- CV side effects = bradycardia, vasodilation
- CBF = conflicting data
- Drug specific S/E = rigidity
- Recommended for = preventing responses to laryngoscopy
- Avoid for = hypovolemia
Benzodiazepines
- Speed of onset = fast
- Duration of effects = long
- Pain on injection = no
- Myoclonus = no
- CV s/e = vasodilation
- CBF= decreased
- Drug specific s/e = n/a
- Recommended for = preventing responses to laryngoscopy
- Avoid for = Hypovolemia
5 Components of Basic Induction
- Anxiolytic: midazolam 0.01 - 0.02 mg/kg
- Local anesthetic: lidocaine 1 mg/kg (up to 100mg max)
- Opioid: Fentanyl 1 - 2 mcg/kg
- Hypnotic: Propofol 2 mg/kg
- NMB: Rocuronium 0.6 mg/kg
We give these to relieve anxiety, help transition to unconsciousness, and to facilitate intubation
Stress response to anesthesia and the hormone impact: Anterior pituitary Posterior pituitary Adrenal Cortex Pancreas Thyroid
Anterior Pituitary:
- ACTH = increases
- Growth hormone = Increases
- TSH = May increase or decrease
- FSH & LH = May increase or decrease
Posterior Pituitary:
- AVP (vasopressin) = increases
Adrenal Cortex:
- Cortisol = increases
- Aldosterone = increases
Pancreas
- Insulin = often decreases
- Glucagon = Usually small increases
Thyroid
- Thyroxine, tri-iodothyronine = decreases
Other Induction Applications
High dose opioids - can be used, usually in open heart - opioids provide little amnesia - recommended a small dose of anxiolytic
Inhalation agents - can be used to induce unconsciousness alone - used in pediatric cases
- when given in high concentrations, NMB is not needed to open cords
- w/ or w/o nitrous
- May be used to keep patient spontaneously breathing
- Must use gases that are non-irritating to breathe
IM shots are rarely used but facilitate induction during:
- laryngospasm
- Combativeness
NMB is not necessary but often desired for superior intubating conditions
Drug Interactions:
Most are synergistic = effect is greater than the sum of the two drugs (it is
- except ketamine
Hypnotic drug doses can be reduced when opioid or bentos are added
Opioids and benzos together produce hypoxemia & apnea
- but not by themselves (at low doses)
Opioids w/ volatiles provide better intubating conditions when no NMB
CV effects:
Barbiturates:
Ketamine:
Etomidate:
Propofol:
Fentanyl:
Barbiturates = CV depressants (phenobarbital, pentobarbital)
Ketamine = myocardial depressant, but increases sympathetic tone so limited compensation — you can give to an unstable patient w/o cardiac issues
Etomidate = least amount of CV effects — GO TO in the ER
- but limited d/t adrenal insufficiency & critical illness d/t the suppression of the adrenal response
Propofol = significant sympathetic tone reduction = CV depression - should titration to effect (push until you see desired response then quit), - should have presser ready ( Neo gtt or ephedrine up front)
Fentanyl = reduce sympathetic tone and increase vagal tone
- unlike other opioids that have no CV effect
What are the two most common medications that can cause injection pain?
Propofol & Etomidate
- IV size and slow flowing Mainline will enhance the pain
- Lidocaine is to decrease stress response but off label use is to decrease the pain from injection
- Usually give lidocaine before they are on monitors, 3 - 5 minutes onset
What 3 Drugs are more likely to cause Myoclonus
Etomidate 87%
Thiopental 17%
Propofol 6%
Why is myoclonus and rigidity a concern when giving opioids
If given with an inadequate muscle relaxant can cause muscle rigidity and closure of the masseter muscle and vocal cord closure
What is the purpose of Rapid Sequence Induction?
What patients do you use this on & why?
Get protected airway as fast as possible to prevent aspiration
- secure airway —> cuffed ETT
Used in patients to prevent regurgitation and pulmonary aspiration in the high risk patients
- Trauma
- Morbid obese
- GERD
- Pregnancy
- Diabetic
- Small bowel obstruction
- Presence of NG tube
What is the Sellick Maneuver?
BURP method
- Backwards, upwards, right (slightly), pressure
- Cricoid pressure against cervical vertebra to occlude upper esophagus
- Awake = 10 N or 1 kg of pressure
- Unconscious = 30 N or 3 kg
What is a downside of Cricoid pressure ?
Most practitioners do not know how to apply it
- Causes complete occlusion of airway
- Can cause vomiting upon release
Classic RSI
- Ensure pre-oxygenation (3-5 min)
- Final verification of functioning scopes, ETTs, Suction on high
- Best positioning (sniff)
- Pre-calculated doses:
- Hypnotic IV push immediately followed by m. Relaxant @ full dose (usually succ) IV push - Apply cricoid pressure @ the time of push
- DO NOT ventilate to test airway
- After fasciculation (45-60 sec) or TOF w/ significant attenuation
- Inflate cuff 1st then pull styles
- Ensure ETCO2
- Do not allow assistant to release cricoid pressure until ETT confirmed
What is the difference between Classic RSI and Modified RSI
Any deviation from the Classic version is considered modified:
- adding an opioid
- adding an anxiolytic
- adding lidocaine
- lightly mask ventilating
- not using cricoid pressure
- Defasciculating dose of muscle relaxant
What are compromises of doing and RSI compared to a basic induction sequence?
Cannot guarantee:
- unconsciousness - just go by the time of the rapid push
- an ideal intubating condition (IC)
- Maskability - not testing ventilation of the unconscious patient. Before giving a NMB & intubating
- Incorrect cricoid may worsen ICs
- Individualized drug dosing is not completed
What are 6 controversies to RSI
- Induction drug choice & timing
- Use of narcotic
- M. Relaxant choice, optimal dose, & priming and timing
- Ventilation
- Cricoid pressure
- Patient positioning
RSI Induction Drug Choice
- Hypnotic is not always needed = BP can’t always tolerate one
- Must consider patient’s clinical condition
- Hemodynamically unstable or not
- Propofol = best possible ICs
- not ideal for: hypotension patients d/t decrease in MAP
- Ketamine
- has undesirable side effects
- When given with midazolam it is the most hemodynamically stable
- Etomidate is the most popular in ER
- DO NOT give in septic pt.s
- More diaphragmatic movement than Propofol & Roc - the drive to breathe is not completely wiped out
- Used widely in frail cardiac pt.s who can not tolerate Propofol
- Have to wait for apnea as well as unconsciousness since they do not happen at the same time and can cause a cough & laryngospasm
Induction Drug dose and Timing
What do you risk in a classic RSI?
What do you risk in a modified RSI?
Classic = predetermined dose of hypnotic then immediate NMB
- Risk of being paralyzed before unconsciousness so your patient is AWARE
- We continue to do this for a shorter time to intubation to prevent aspiration
Modified = more likely to ensure unconsciousness
… but prolonged intervals leaves a risk d/t unprotected airway
