Induction Flashcards
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
