Lessons 1 & 2 Flashcards
True/False
Antecubital Veins are NOT usable for perioperative IV during prone spine surgery
True
Biggest “con” for antecubital IV
They can “infiltrate” like any other IV, but (unlike other IVs) the infiltration may be hard to detect (even more so on very muscular or obese patients)
What size IV for massive transfusion?
Two 16G IVs
If you want to look up the “Poiseuille relationship” go crazy
True/False
You CANNOT induce with a 22G IV
False
22G is fine to induce, but you will need a bigger IV after
4 Goals/A’s of General Anesthesia
- Amnesia (w/ LOC)
- Analgesia
- Akinesia (skeletal muscle relaxation)
- Autonomic and sensory reflex blockade
Define General Anesthesia
A state of reversible coma intentionally induced by drugs in which the patient is not arousable even with painful stimuli
Define Balanced Anesthesia
General anesthesia with several agents
(can be a mixture of inhalational and IV medications)
Define Regional Anesthesia
Use of local anesthetics (sometimes with other additives) applied to an anatomically-familiar nerve root(s) or peripheral nerve, to numb a particular region of the body
Define Combined Technique
Regional Anesthesia + General Anesthesia
What is Monitored Anesthetic Care?
Sedation provided by an Anesthesiologist or CRNA
ASA I
No medical problems
ASA II
One or more systemic diseases under good control
ASA III
One or more systemic diseases which are not in perfect control or limit function to some extent
ASA IV
A systemic condition which is a constant threat to life
ASA V
Expected to die within a day, surgery is a desperation measure
ASA VI
Dead patient (organ harvesting)
ASA E
E = emergency
(can be added to any ASA status)
Types of IV Anesthetics
- Sedative-hypnotics (barbiturates, etomidate, propofol, benzodiazepines)
- Opioids
- Dissociative anesthetics (ketamine)
Thiopental
Barbiturate
Crosses BBB rapidly
Short acting even though elimination half life is several hours
Difference between barbiturate and benzodiazepine in terms of mechanism of action?
Barb = prolonged Cl channel opening (potentiates GABA)
BZ = increased frequency of Cl channel opening (potentiates GABA)
What is Etomidate?
Carboxylated imidazole (simply put = GABA potentiator)
Pro: Minimal CV effects
Con: Potential adrenocortical suppression
Onset of action for Etomidate
Onset: 30-60 seconds
Peak effect: 1 min
Duration: 3-5 min
Metabolized by hepatic and plasma esterases to inactive product
Why is propofol a popular induction agent?
Compared to thiopental, propofol has:
- Antiemetic and antiepileptic activity
- Associated w/ faster and more complete awakening
- Easier to store in anesthesia carts
- Cheap
- Treats alcohol detox
- Does not “mask pain”
When is propofol contraindicated?
History of:
- Propofol infusion syndrome (PRIS)
- Pancreatitis from hypertriglyceridemia
- HFrEF (or concern for “soft pressures”)
Propofol’s mechanism of action
- Decreases dissociation of GABA from the receptor (increasing duration)
- At supraclinical concentrations, it may directly activate the receptor’s chloride channel
- Very similar to Etomidate in terms of MOA*
Most popular benzodiazepine in anesthesia
Midazolam (primarily used as an anxiolytic or for amnestic effect)
Short half-life, water soluble (not painful on injection), coverts to highly lipid soluble form in blood pH
Prototype Opioid Agent
Morphine
Synthetic agents = fentanyl, sufentanil, remifentanil
Fentanyl vs Morphine
Fentanyl is:
- 100x more potent
- More liphophilic (crosses BBB faster)
- Unlikely to cause hypotension, even with rapid administration of a relatively large dose*
*Morphine can cause hypotension via the release of histamine (especially with rapid administration)
Side effect unique to fentanyl
Chest wall rigidity (especially when given as a rapid bolus)
How if Fentanyl excreted?
Oxidized by hepatic microsomal cytochrome P450 into norfentanyl, an inactive metabolite that is then renally excreted
What are the volatile liquids?
Halothane
Isoflurane
Desflurane
Sevoflurane
Ideal Anesthetic Gas
Low blood solubility (i.e., faster onset)
Minimal metabolism
Compatible w/ Epi
Not irritating to the airway
No myocardial depression
Blood Solubility
AKA partition coefficient
The distribution ration between 2 phases at equilibrium
Blood is an inactive reservoir (high blood solubility = decreased speed of onset)
Blood Solubility for Inhalational Anesthetics (from fastest time of onset to slowest)
Des (0.42) > N2O (0.47) > Sevo (0.69) > Iso (1.4) > Hal (2.5)
“Do Not Shit In Here”
Define MAC
The steady state concentration of an inhalational agent that maintains immobility in 50% of subjects exposed to a noxious stimulus
True/False
MAC values are additive
True
Ex: 1 MAC of Iso + 0.5 MAC N2O = 1.5 MAC
MAC 0.25
MAC 0.5
MAC 1
MAC 1.5
MAC 2
- 25 = 50% experience anterograde amnesia
- 5 = 50% unconscious
1 = 50% will not move at incision
1.5 = 95% will not move at incision
2 (aka MAC-BAR) = 50% blocked autonomic reflexes at incision
Which Inhalational Agent is used for induction?
Sevo
The other agents cause airway irritation and bronchospasm
Stages of Anesthesia
Stage 1: Analgesia
Stage 2: Excitement (Delirium)
Stage 3: Surgical Anesthesia
Stage 4: Medullary Depression
How does cardiac output affect the speed of induction?
Increased CO = decreased rate of rise of arterial anestheic gas = slower induction
Low CO = faster induction
Rare, inherited, potentially lethal syndrome almost exclusive to anesthesiology
Malignant Hyperthermia
Due to mutations in the ryanodine receptor 1 gene
Hypermetabolic state, Marked CO2 production, Altered skeletal muscle tone, Mixed respiratory & metabolic acidosis
