Anesthesia

Table of Contents

ASA Classification

ASA 1: Healty, fit patient

ASA 2: Patient with mild systemic disease (i.e. controlled Type 2 diabetes)

ASA 3: Patient with severe systemic disease that limits activity (stable CAD, COPD, DM, obseity)

ASA 4: Patient with incapacitating disease that is constant threat to life (unstable CAD, renal failure)

ASA 5: Not expected to survive without surgery (ruptured AAA, head trauma)

ASA E: For Emergency operations

8 hours: after meal that includes meat, fried, fatty foods
6 hours: light meal (toast, crackers, clear fluid)
4 hours: breast milke or jello
2 hours: clear fluids (water, black coffee, tea, carbonated beverages, juice without pulp)

Drug	Continue/Discontinue	Notes
GE reflux meds	Continue/Start	sodium citrate 30mL PO or ranitidine 150-300mg PO 30min-1hr pre-op
Adrenal Suppression	Start	If on steriods, must give stress dosing of steroids because adrenals suppressed from exogenous steroids.
Risk of DVT	Start	Heparin SC
ASA	Usually Continue
Warfarin	Usually bridge to LMWH
Hypoglycemics	Stop All	due to NPO (if TIIDM may stop, but if Type I DM: definitely stop), can recheck glucose post-op and give insulin.
Antidepressants (incl SSRI, MAOi)	Stop All	Stop the morning of OR

Low Flow Systems:

Usually non-invasive, provide consistent O2 flows 0-8 L/min.
However FiO2 (Fraction of Inspired O2) is inconsistent (based on minute ventilation (tidal volume x RR)).
If patient is tachypneic: FiO2 will be low because they will take in more air, and the steady flow (0-8 L/min) will be diluted.
Nasal Canula (prong)
- Flow rates <5-6 L/min, if go higher will dry out mucosa + uncomfortable blowing air into nose.
- FiO2 estimated by adding 20% + 4% for each liter of O2 delivered (1L/min = 24% FiO2, 6L/min = 44% FiO2), considering patient breathing normally.

Reservoir Systems:

Use small reservoir to accumulate O2 during exhalation, increasing the amount of oxygen available for next breath.
Simple Face Mask (Hudson Face Mask) (Flow: min 6 L/min)
- Covers patient's nose and mouth (normally only nasopharynx is the reservoir for O2, but FM expands this reservoir)
- Flow rates at least >6L/min required, if go lower, CO2 will not be flushed out of mask.
- FiO2 = 55% approx if O2 flow 10L/min
Non-Rebreather Mask (Flow 10-15 L/min)
- A separate bag to collect and concentrate oxygen.
- A series of valves cause expired air to be removed and not mixed with incoming O2.
- O2 flow rates 10-15 L/min required to keep bag inflated.....FiO2 >80%

High Flow Systems

Flows up to 50-60 L/min --> meets or exceeds patient's flow requirement.
Delivers consistent FiO2 regardless of minute ventilation (resp rate etc..)
Venturi Mask
- Delivers specific FiO2 (pick valve) (24%, 28%, 35%, 50%)
- Can humidify air if wanted to.