How do volatile agents (and nitrous oxide) change the pattern of spontaneous ventilation?
Increase RR, decrease Vt, decrease Minute ventilation
How does nitrous oxide affect MAP, HR, and CO?
No change or slight increase
How do volatiles affect MAP, HR, and CO?
Decrease MAP (des=iso>sev), increase HR(iso>des>sevo), decrease CO (sevo>des>iso)
What is the redistribution half life of propofol?
3-5 minutes
What are the clinical effects of hypercarbia?
- Stimulation of sympatho-adrenal system (increase HR, CO, pulm pressure, BP, SV)
- peripheral vasodilation, pulmonary vasoconstriction
- hypercarbic narcosis (becomes anesthetic)
- dysrhythmias
How much does a dose of succinylcholine raise the plasma K+ concentration?
Approx. 0.5-1.0 mEq/dL
Which NMB monitoring site is best during intubation?
Orbicularis oculi
Which NMB monitoring site is best during emergence?
Adductor pollicis
Which muscles are most resistant to NMB? Most sensitive?
- vocal cord (most resistant)
- diaphragm
- Orbicularis oculi
- abdominal rectus
- adductor pollicis
- masseter
- pharyngeal
- extraocular (most sensitive)
Which type of NMB drug exhibits post-tetanic potentiation?
Non depolarizing
Why doesn’t sustained ventilation = sufficient reversal?
Upper airway structures are weak, posing risk of upper airway obstruction
What percentage of receptors are blocked with TOF 0-4?
4/4 = 75% 3/4 = 85% 2/4 = 90% 1/4 = 95% 0/4 = 99%
How can you use a post-tetanic count to determine ability to reverse NMB?
If no response to single twitch,
- 50 hz tetany for 5 sec
- wait 3-5 sec
- one twitch/sec
- if >10 twitches present, there are sufficient receptors for reversal
What are some common extubation criteria?
- sustained head lift >5 seconds
- RR 5-30
- tidal volume >5cc/kg
- PaO2 >65 on FiO2 <10L/min
- level of consciousness
- NMB reversed
Contraindications of deep extubation
- difficult mask ventilation
- difficult intubation
- aspiration risk
- airway edema
Criteria for deep extubation
- MAC 1.3
- NMB completely reversed
- SV at reg rate and rhythm
- no airway reflexes (check with cuff deflation AFTER suctioning)
- 100% O2
- lidocaine 0.5mg/kg
- consider fentanyl
