General Anesthesia Flashcards
(32 cards)
What is general anesthesia?
A pharmacologically induced state of amnesia, unconsciousness, skeletal muscle relaxation, and reduction of autonomic responses
What is altered with medically induced loss of consciousness?
Medically induced loss of consciousness (mLOC) causes a breakdown in the signaling between brain regions (macro scale) and altered signaling between neurons (microscale)
What are the five phases of an anesthesia?
Preoperative: eval, H&P, anxiolysis Induction Maintenance: during procedure Emergence: reverse or let medications wear off Postoperative: PACU
What is the goal preoperatively? What types of meds are used for this?
Anxiolysis; Benzodiazepines
Diazepam
- Use
- Mechanism of action
- Half life
- Sedation, anxiolysis, muscle relaxation, ANTEROgrade amnesia **No analgesic properties
- facilitates the action of GABA at the a subunit –> enhanced opening of Cl- channels causing hyper polarization of the membrane–> resistant to excitation
- 21-37 hrs
* *least potent
Midazolam
- Use
- Mechanism of action
- Half life
- Sedation, anxiolysis, muscle relaxation, ANTEROgrade amnesia **No analgesic properties
- facilitates the action of GABA at the a subunit –> enhanced opening of Cl- channels causing hyper polarization of the membrane–> resistant to excitation
- 1-4 hrs
* *medium potent
Lorazepam
- Use
- Mechanism of action
- Half life
- Sedation, anxiolysis, muscle relaxation, ANTEROgrade amnesia **No analgesic properties
- facilitates the action of GABA at the a subunit –> enhanced opening of Cl- channels causing hyper polarization of the membrane–> resistant to excitation
- 10-20 hrs
* *most potent
Propofol
- Use
- Mechanism of action
- Termination of action
- Induction of anesthesia and general anesthesia
- Presumed interaction with GABA; delays the dissociation of GABA from receptors –> hyperpolarization of cell membranes
- Tissue uptake and redistribution causes termination of action, not metabolism
Propofol
- CV effects
- Pulmonary effects
- CNS effects
- Decreased SBP, MAP, SVR (no change HR)
- RR depression is dose dependent
- Decreased CBF, ICP and CMRO2
Etomidate
- Use
- Mechanism of action
- Induction of anesthesia
- Rapid onset of sleep and awakening from assumed enhanced GABA effects
**Myoclonus and adrenal suppression; increased PONV
Etomidate
- CV effects
- Pulmonary effects
- CNS effects
- If low volume or pain/anxiety causing higher blood pressure or HR, can caused decreased BP and HR, otherwise no change. No change or decreased SVR
- Minimal respiratory depression
- Decreased CBF, ICP, CMRO2
Ketamine
- Use
- Mechanism of action
- Induction of anesthesia, adjunct analgesic
- NMDA, interaction with opiod, monoaminergic, muscarinic receptors and voltage gated Ca++ channels
**Emergence delirium
Ketamine
- CV effects
- Pulmonary effects
- CNS effects
- Increased BP, HR and SVR
- No respiratory depression
- Increased CBF, ICP, CMRO2 **don’t give for neuro surgery
Barbiturates
- Use
- Mechanism of action
- Induction of anesthesia
- Interacts with GABAa receptor
**contraindicated in patients with Acute Intermittent Porphyria
Barbiturates
- CV effects
- Pulmonary effects
- CNS effects
- Decreased BP, Increased HR, Decreased SVR
- Rapid and profound respiratory depression, apnea
- Decreased CBF, ICP, CMRO2
Dexmedetomidine
- Use
- Mechanism of action
- Premedication, MAC, Maintenance of GA
2. Nonselective a2 agonist causing sedation and analgesia
Dexmedetomidine
- CV effects
- Pulmonary effects
- CNS effects
- Decreased HR and SVR (indirectly CO, SBP and contractility as well)
- Similar to natural sleep (decreased minute ventilation but maintains CO2 response)
- Unknown, maybe some neuroprotection
Volatile Anesthetics
- General properties
- Mechanism of action
- Absence of flammability, vapors at room temperature, potent, low solubility in blood with minimal tissue metabolism
- Inhibiting glutamate (excitatory NT) and enhancing GABA (inhibitory NT) produces amnesia, sedation, hypnosis and muscle relaxation
Why are volatile anesthetics fluorinated?
- Reduce or eliminate toxicity
- Reduce or eliminate flammability
- Increased speed of induction and recovery from anesthesia
- What is solubility?
- What molecules cause anesthesia?
- How does solubility effect wake up?
- Solubility is how much of the anesthetic agent soaks into bodily tissues
- Only free, gaseous anesthetic molecules cause anesthesia
- The more soluble an anesthetic, the slower the onset and the slower the wake up
**Smaller coefficients (low solubility) move in and out of tissues faster and make for faster induction and wakeup
- What is Dalton’s law of Partial Pressure?
2. How does this relate to inhaled anesthesia?
- The total pressure in a mixture of gasses is the sum of the partial pressures of each gas
- The partial pressure of anesthesia in the lungs (PAlveoli) equilibrates with the partial pressure in the blood (Parterial) which equilibrates with the partial pressure in the brain (Pb)–> causes anesthetic level
What is MAC? How is this number used?
MAC is the partial pressure (Vol%) of an anesthetic that must be present in the brain to result in general anesthesia (hypnosis)
It is used to compare anesthetics to each other
- What is MAC incision?
- What is MAC awake?
- What is MAC BAR?
- Level of anesthesia at which 50% of the patients will not move to a surgical stimulus = 1MAC
- Proportion of MAC at which patients will wake up and follow commands = .4MAC
- Blunting of autonomic responses: very deep level of anesthesia at which patients show no CV response (BP or HR) in response to stimulation = 1.3MAC
Are MACs additive?
YES