Week 8- General Anesthesia Flashcards
Anesthesia, by the definition, is a change in the responses of an ____ _____ to ____ _______. Making a definitive link between anesthetic effects observed in vitro and the anesthetic state observed and defined in vivo is difficult.
intact animal
external stimuli
T/F: There are multiple molecular mechanism that can produce clinical anesthesia.
True!
No structure-activity relationships are apparent among anesthetics. A wide variety of structurally unrelated compounds, ranging from steroids to elemental xenon, are capable of producing clinical anesthesia.
Anesthetics work at very high concentrations in comparison to drugs, neurotransmitter and hormones; this implies that the have a very _____ ______ to the receptor and do not stay bound for long.
low affinity
this makes it much more difficult to observe and characterize than high affinity bonding. They stay bound to the receptor for very short periods of time.
broadly defined as a drug-induced reversible depression of the CNS resulting in the loss of response to and perception of all external stimuli.
General Anesthesia
Anesthesia is a collection of “component” changes in behavior or perception.
The components of an anesthetic state: (5)
A. unconsciousness
B. amnesia
C. analgesia
D. immobility
E. attenuation of autonomic responses to noxious stimuli
One of the reasons why defining anesthesia is difficult?
our understanding of the mechanism of consciousness is amorphous
T/F: MAC is additive.
True
** example running nitrous with sevo
In order to study the pharmacology of anesthetic action, qualitative measures of anesthetic potency must be measure (T/F)
False!! quantitative
why is there some difficulty in defining anesthesia?
MOA is not fully understood at this time
General anesthesia is a collection of “component” changes in _______ & ___________
behavior & perception
___________measures of anesthetic potency must be measured
Quantitative
what is MAC (minimum alveolar concentration)
partial pressure of gas at which 50% of humans do not respond to surgical stimulation
MAC = _____: Represents the average response of ___________, not the response of a single subject
Dose;
the whole population
________ concentration of gas provides an index of the “free” concentration of drug required to produce anesthesia
end-tidal
how does end-tidal concentration provide an index of the “free” concentration of drug required to produce anesthesia
the end-tidal gas concentration is in equilibrium with the free plasma concentration and BIS monitoring
MAC only refers to the___________ of agent. NOT the _________ of other adjuncts that we have given
concentration
amount
_________ has also become a standard of care in general anesthesia
BIS monitoring
There is a linear relationship between the oil/gas partition coefficient and anesthetic potency (MAC)- theories regarding protein binding also satisfy the
Meyer-Overton Rule
Unitary theory of anesthesia:
Since a wide variety of structurally unrelated compounds obey the Meyer-Overton Rule, it has been reasoned that all anesthetics are likely to act at the same molecular site.
Genetic data plainly demonstrates that the this unitary theory of anesthesia is not correct; no single mechanism is responsible for the effects of all general anesthetics
More than 100yrs ago Meyer and Overton observed that the potency of gases as anesthetics was strongly correlated with their solubility in olive oil- this idea led to:
The unitary theory of anesthesia
Anesthetic agents must disrupt the function of neurons mediating ________, __________, & __________
behavior, consciousness & memory
Anesthesia alters neuronal communication by:
- altering neuronal excitability- create a more negative rmp (resting membrane potential) = hyperpolarize the neuron which decreases the action potential.
- synaptic transmission- widely considered to be the most likely subcellular site of general anesthetic action
**evidence suggest that some voltage gated calcium channels are sensitive to anesthetics and some sodium channels subtypes are inhibited by volatile anesthetics. This effect may be responsible for a reduction in neurotransmitter release at some synapses.
widely considered to be the most likely subcellular site of general anesthetic action
synaptic transmission
T/F: Many anesthetics potentiate GABA in CNS
True.
GABA receptors are probable targets of anesthetics along with what other sites?
- Glycine
- Neuronal nicotinic receptors
- 5-HT3 receptors.
Relevant targets for Amidate & Propofol
GABA activated ION Channels
Where in the CNS do Anesthetics work?
- Suppress circuits in the spinal cord & brainstem
- Induce immobility & disrupt autonomic homeostasis
It is clear that all anesthetic effects cannot be localized to a specific anatomic site in the CNS. (T/F)
True
T/F: Neurobiologic underpinnings of arousal and awareness are distributed across the brainstem, subcortical, and cortical structures. There is a single anatomic site responsible for anesthetic-induced unconsciousness.
False!
** There is no single anatomic site responsible for anesthetic-induced unconsciousness.
Genetic data plainly demonstrates that the unitary theory of anesthesia is not correct because:
No single mechanism is responsible for the effects of all general anesthetics .
Nor does a single mechanism account for all effects of a single anesthetic.
Anesthetics have powerful and widespread effects on
synaptic transmission
Volatile anesthetics directly reduce excitatory synaptic transmission of______ neurons
spinal
Propofol depresses activity in______ horn neurons via GABAergic mechanism
ventral
_______ suppresses interneurons of central pattern generators involved in coordinated movements
Isoflurane
Anesthetics can alter descending, afferent, efferent & modulating limbs of ______ ______ for reacting to noxious stimulation
reflex arcs
It is clear that all anesthetic actions cannot be localized to a specific site in the CNS- much evidence allows that different components of the anesthetic state are mediated by actions at ______ anatomic sites!
disparate
Anesthetics exert profound effects on cardiopulmonary & thermoregulatory homeostatic circuitry without autonomic centers in the______ & _______
brainstem
hypothalamus
Inspiratory neurons in the________ drive phrenic motor neurons to activate diaphragmatic contraction
medulla
______ suppresses the spontaneous activity of the inspiratory neurons to activate the diaphragm
Halothane
Anesthetics also have an effect on the cardiovascular reflexes mediated by nuclei in the______
brainstem
the __________ is a plausible target for suppression of memory formation
hippocampus
causes amnesia
Is a diffuse collection of brainstem neurons that mediate arousal
RETICULAR ACTIVATING SYSTEM (RAS)
Is the major site for generating awareness of the external environment; primary sensory areas
cerebral cortex
**Disruption feedback by anesthetics may contribute to impaired consciousness
T or F: extubtion of trachea is a benign procedure
F - NOT benign
Extubating Criteria: (8)
- secretions cleared
- 5-sec head lift/sustained hand grasp
- adequate pain control
- minimal expiratory concentration of IA
- Vc > or = 10 ml/kg
- Negative inspiratory pressure >20 cmH20
- Vt > 6 cc/kg
- sustained tetany
PACU report should include (7)
- List ABX given
- Amount of narcotic
- Make sure RN comfy with pt
- Pt allergies
- Any med rxns (reactions)
- Report before you leave
- Airway difficulties (intubation/extubation)
most stimulating part of D&C
dilation
during D&C, when can you usually turn off N2O
when they begin suction
Suction D&C for a woman that had a missed AB at 10weeks but has reflux; and a BMI of 48 – what position
Lithotomy position in steep Trendelenburg
LMA should not be used if?
- Prone surgery
- Muscle relaxants used
- Sx over 2 hours
- Insufflated belly (ex. Lapararoscopic)
- BMI > 50
Designed a classification system used to define relative risk prior to conscious sedation and surgical anesthesia
American Society of Anesthesiologists (ASA)
Class I ASA
Class 1: Normal healthy patient
Class II ASA
Patient with mild systemic disease (no functional limitations)
Class III ASA
Class 3: Patient with severe systemic disease (some functional limitations)
Class IV ASA
Class 4: Patient with severe systemic disease that is a constant threat to life (functionally incapacitated)
Class V ASA
Class 5: Moribund patient who is not expected to survive without the operation
Class VI ASA
Class 6: Brain-dead patient whose organs are being removed for donor purpose.
E - ASA
If the procedure is an emergency the physical status is followed by an “E”
SAB
Subarachnoid block (this is a spinal)
PAW
PAW- peak airway pressure
IntrathecaL
inside the dura
Epidural
outside of the dura, In the epidural space (which is a potential space)
GSW
gun shot wound
BBSE
Bilateral breath sounds equal (a fast way to chart lung sounds that are clear
One of the reasons why defining anesthesia is difficult?
our understanding of the mechanism of consciousness is amorphous
