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155 Cards in this Set
- Front
- Back
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List the definition of general anesthesia
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An altered physiological state characterized by REVERSIBLE loss of consciousness, analgesia of entire body, amnesia, and some degree of muscle relaxation
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What are the 2 ways general anesthesia is achieved
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Intravenous agents and inhaled agents
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Why are inhaled gases better than IV in general anesthesia
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We can measure the effectiveness of gases by the exhaled value of the gas as it is thought that these values are similar to the anesthetic concentration in the brain
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What are the three phases of general anesthesia
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Induction, maintenance, and emergence
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List what happens during induction
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In adults, usually IV medications are given then the inhalation agent. In peds usually inhalation agent first, then IVs
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List what happens during the maintenance phase
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Balancing adequate anesthetic depth vs. hemodynamics
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What is emergence
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A process that starts as much as an hour before the end of the case where the patient is brought out of general anesthesia. This is where the "art" of anesthesia comes in
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What are the thre methods of giving inhaled anesthetics
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Mask, LMA, ET tube
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When are masks used for general anesthesia
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Usually short (10-20 min) peds cases
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When are LMAs used for general anesthesia
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Usually with same day surgeries and short cases. It is also used in can't intubate, can't ventilate patients
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When are LMAs contraindicated for general anesthesia
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High resp pressures, long cases, cases with several repos, OB, obese pts, diabetics, and any other pt at risk for aspiration
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What are the benefits if using an ET tube during general anesthesia
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It is the one truly secure airway, it protects against aspiration, it can be used with high pressures, and it can be used for surgeries with odd positions or numerous repositions
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When was nitrous first demonstrated
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1844
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T or False: Nitrous is a potent analgesic
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True
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List the benefits of nitrous
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Increases SVR and supports BP, decreases the need for higher amounts of inhaled anesthetics
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List the negatives of nitrous
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It's a potent trigger for post-op N/V, it expands into spaces faster than air can get out, thus making pneumos worse and causing expansion of the bowels and stomach. Administration over several days may lead to aplastic anemia and death. Also, nonflammable, but will promote combustion.
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Where might you come in contact with enough nitrous to cause the increased risk of abortion or decreased fertility
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In officed based anesthesia where there are no scavengers, dentist's office, and during mask inductions
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What are contraindications for nitrous use
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Inner ear procedures, pneumocephalus, retinal surgery, gastric surgery, and surgeries where the risk for fire is high
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When was diethyl ether first demonstrated
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1846
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What is another name for halothane
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Fluothane
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When was halothane first introduced into clinical practice
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1956
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What is Halothane
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A halogenated alkane derivative
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What does it mean for a chemical to be halogenated
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It means one of the halogens (F, Br, or Cl) are attached to the base molecule
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What does halogenation do to the anesthetic molecule
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It stablilizes it and makes it less flammable and less toxic
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What characteristic of halothane makes it a good candidate for inhalation induction
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It is not very pungent
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What are the negatives of halothane
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It sensitizes the myocardium to catecholamines leading to dysrhythmias and can lead to halothane hepatitis
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What can make the dysrhythmias related to halothane use more pronounced
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Use of exogenous epinepherine. ENT cases, lido/epi use, etc
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When was methoxyflurane first introduced
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1960
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What is another name for methoxyflurane
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Penthrane
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What is methoxyflurane
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A halogenated methylethyl ether
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What is the most potent inhaled anesthetic
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Methoxyflurane
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Why was methoxyflurane discontinued from clinical practice
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It causes fluoride induced nephrotoxicity
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What is another name for Enflurane
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Ethrane
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When was Enflurane introduced
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1973
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What is enflurane
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A Halogenated methylethyl ether
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What is enflurane also implicated in
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Flupride induced nephrotoxicity
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What is another name for Isoflurane
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Forane
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When was isoflurane introduced
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1981
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What is isoflurane
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It is a halogenated methylethyl ether, also it is an isomer of enflurane
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What does isomerization of an anesthetic agent do
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It can keep all of the benefits of an anesthetic while getting rid of the negative effects
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What makes isoflurane a popular anesthetic
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It's cheap and has relatively benign hemodynamic effects
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What makes isoflurane less popular than other agents
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It is highly soluble in the blood
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What is another name for desflurane
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Suprane
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When was desflurane first introduced
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1992
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What is desflurane
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It is a fluorinated methylethyl ether. (the only inhaled anesthetic completley fluorinated)
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What makes desflurane popular
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It is the least soluble anesthetic
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What makes desflurane less popular than the other anesthetics
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Very expensive, most pungent agent, concentrations >6% can cause airway irritation, it reacts with dessicated CO2 absorbants to form CO
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Where is desflurane contraindicated
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Asthmatics, COPDers, inhalation induction
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What is another name for Sevoflurane
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Ultane
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When was sevoflurane introduced
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1993
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What is sevoflurane
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It is a fluorinated methyl isopropyl ether
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What is the benefit of using sevoflurane
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It's non pungency and low solubility make it ideal for inhalation induction using the overpressure technique. It's relatively cheap
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What is the overpressure technique
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Giving higher doses thatn the maintenance MAC value to speed induction
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What is the negative of sevoflurane use
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It reacts with dessicated CO2 to form compound A, higher FGF reduce the formation
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What is the target of injury for compound A
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The corticomedullary junction of the kidney
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T or F: There have been several documented cases of compound A formation from sevoflurane use injuring human kidneys
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False, it has been shown in rats, but no documented human cases as of yet
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What is the Meyer-Overton (critical volume) hypothesis
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Anesthestic dissolves in the lipid bylayer of neruonal membranes, therby disrupting neuronal transmission
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What is the Meyer-Overton rule and what is it's fatal flaw
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Anesthetic potency correlates directly with lipid solubility. There are several durgs that are very lipid soluble that cause no anesthetic effect
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It is generally accepted that the mechanism of action of inhaled anesthetics is a combo of what three thoughts
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The Meyer-Overton rule, modulation of excitatory NT/receptor activity, moodulation of inhibitory NT/receptor activity
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What is MAC a measure of
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It is a measure of anesthetic potency
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Is MAC inversely or directly proportional to potency
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Inversely
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Do we use the MAC values that are dialed in the vaporizer or the MAC value read on the exhaled gas analyzer to calculate our maintenance drug level
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Exhaled gas analyzer
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What does it mean when it is said that MAC values are additive
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It means that if you have 0.5 MAC of one substance and 0.5 MAC of another substance you hacve a total of one MAC of working anesthetic
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In the abscence of any other drugs that enhance MAC, what MAC value do we typically use (prevents movement in 95% of people)
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1.3 MAC
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T or F: MAC is dependent on weight and/or BMI
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False, it is independent of weight
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Deefine partial pressure
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The partial contribution that a gas makes to the total pressure exerted by a mixture of gases
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What is the principle objective of inhalation anesthesia
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To achieve a constant partial pressure of the anesthetic in the brain
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List the PP equation that illustrates the equillibrium of PP
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Pi<-->PA<-->Pa<-->PBR
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Why are the alveoli considered to be the window to the brain
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Because the alveolar PP are assumed to mirror those of the anesthetic PP in the brain
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How long does it take for the PBR to mirror PA
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8 minutes
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What determines alveolar PP
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Input of the anesthetic agent into the alveoli minus the uptake by the arterial blood
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Body tissues take up anesthetic gas from the blod based on what
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The solubilty of the gas in the tissue and the total tissue blod flow (which is the most important factor)
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Name the four body reservoirs and which one we want the anesthetic to go to
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Vessel rich group (VRG), muscle group, fat group, vessel poor group (VPG). We're shooting for the VRG
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What makes up the Vessel rich group
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Heart, liver, brain, and kidneys
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What percentage of CO goes to the VRG
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75%
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What would a high CO indicate about the initial uptake of anesthetic into the VRG
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It would be high/quicker
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What comprises the muscle group
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Muscle and skin
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How much CO goes to the muscle group
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20%
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The muscle group still has a relatively high blood flow. Why isn't there a high uptake in these tissues
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Anesthetics are less soluble in these tissues
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What can the fat group function as
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Large reservoirs for anesthetics
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What limits the impact on uptake in the fat group
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Minimal perfusion
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WHat makes up the vessel poor group and why do they have an insignificant uptake
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Bone, Ligament, teeth. Uptake is limited due to little or no blood flow
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In watching end tidal gases initially the level will be close to diald in %, after 8 minutes it will be close, then start to drop. Explain the drop in exhaked gas level
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After awhile, the fat and muscle groups start to take up the anesthetic
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What does solubility govern
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The rate of increase and decrease in alveolar concentration during induction and recovery from inhalation anesthetics
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The solubility of inhaled anesthetics is denoted by what
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Blood:gas partition coefficients
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What is a partition coefficient
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A distribution ratio describing how the anesthetic gas distibutes itself between the gas phase in the alveoli and the dissolved phase in the blood, when the two are at equilibrium
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What does it mean when an anesthetic has a blood:gas coefficient of 0.5
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It means that at equilibrium there is 0.5 molecules of the anesthetic in the blood for every 1 molecule in the alveoli
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What is the B:G partition coefficient for Nitrous oxide
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0.47
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What is the B:G partition coefficient for Halothane
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2.4
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What is the B:G partition coefficient for isoflurane
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1.4
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What is the B:G partition coefficient for desflurane
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0.42
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What is the B:G partition coefficient for sevoflurane
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0.65
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What does it mean for an anesthetic to have a higher curve on the FA/FI chart
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It means the anesthetic has a lower solubility/quicker onset of action
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Why does Nitrous oxide have such a high curve on the FA/FI chart
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Because of the high concentrations used (i.e. 50-60%)
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T or F: ALL anesthetics provide amnesia even at low MAC levels such as 0.5
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True
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T or F: All anesthetics have analgesic effects even at MAC levels as low as 0.2-0.3
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False, studies have been done on healthy volunteers showing no alteration of pain perception at levels around 0.2-0.3 MAC
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Are inhaled anesthetics potent cerebral vasodilators or vasoconstrictors
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Vasodilators
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Inhaled anesthetics are potent cerebral vasodilators. How might this cause a problem and what can be done to counteract it
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This could lead to an increase in ICP. Hyperventilation can decrease the ICP
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In a patient with an already high ICP, and in need of anesthetic using Halothane, in what order must steps be taken to avoid further increasing ICP
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Hyperventilation must be started prior to starting halothane
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Do Inhaled anesthetics reduce or increase cerebral metabolic oxygen demand
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Reduce...You can't reduce oxygen supply without reducing oxygen demand
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What do inhaled anesthetics except for N2O do to MAP and how does exert this effect
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They cause dose dependant drops in MAP, secondary to peripheral vasodilation
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What does N2O do to MAP
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It causes little to no change in MAP and actually increases SVR
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Which patients show the most drastic changes in MAP when given inhaled anesthetics
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Those with chronic HTN
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What do Inhaled anesthetics do to Myocardial contractility
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All depress contractility to some degree
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Which inhaled anesthetics show the greates myocardial depression
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Halothane and Enflurane
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What type of patients should halothane and enflurane be avoided
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CHF, Cardiomyopathy, valvular diseases, prior MI
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What do inhaled anesthetics do to the respiratory system in a spontaneously breathing pt
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Decrease minute ventilation by decreasing tidal volume (RR increases, but not enough to compensate), and blunt the response hypoxia and hypercarbia. They are also excellent bronchodilators
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What is the usual cause of intraoperative bronchospasms and what is the first action that should be taken
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Too light of depth of anesthesia, increase the inhaled anesthetic concentration
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What do inhaled anesthetics do to the neuromuscular system
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By themselves little muscle relaxation, but they are significant potentiators of IV neuromuscular blocking agents
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WHat is malignant hyperthermia
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A hypermetabolic disorder of skeletal muscle characterized by the uncontrolled release of calcium from the sarcoplasmic reticulum resulting in intracellular hypercalcemia
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What drugs can cause MH
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Halogenated inhaled anesthetics and succinylcholine
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How many ppl are susceptible to MH in the US and where are the hotbeds
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<200,000. WI, NE, MI, WV
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What is your first symptom you should recognize as a possibility of MH
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Doubling or tripling of end tidal CO2 in a very short period of time
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What are the sequelae of MH
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Profound respiratory and metabolic acidosis, hyperkalemia, myoglobinuria-leading to rhabdo, tubular necrosis and renal failure, and hyperthermia
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What is the sympathatic nervous system's response in MH
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Tachycardia, Tachypnea, ventricular dyrhythmias, hyperthermia, and masseter muscle rigidity
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How late can symptoms of MH appear
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24-36 hrs postop
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WHat is the MAC of Halothane at 100% O2
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0.75
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What is the MAC of Halothane with 70% N2O
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0.29
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What is the MAC of methoxyflurane with 100% O2
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0.16
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MAC of methoxyflurane with 70% N2O
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0.07
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MAC of Enflurane with 100% O2
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1.7
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MAC of Enflurane with 70% N2O
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0.57
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MAC of Isoflurane with 100% O2
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1.2
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MAC of Isoflurane with 70% N2O
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0.5
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MAC of desflurane with 100% O2
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6
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MAC of desflurane with 70% N2O
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2.8
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MAC of sevoflurane with 100% O2
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2
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MAC of sevoflurane with 70% N20
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0.66
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What does temp do to MAC
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Decrease both high and low temps
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What does age do to MAC
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Higher when young, but drops 6% with every decade of life
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What does alcohol do to MAC
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Acute drunk lowers MAC, chronic drunk increases it
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What does anemia do to MAC HTC<10%
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Lowers it
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What does a low PaO2 do yo MAC <40 mmHg
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Lowers it
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What does high PaCO2 do to MAC >95mmHg
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Lowers it
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What do the thyroid diseases do to MAC
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Niether do anything
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What does a MAP <40mmHg do to MAC
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Lowers it
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What do electrolyte imbalances do to MAC
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Hypercalcemia lowers it, hypernatremia increases it, hyponatremia lowers it
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What does pregnancy do to MAC
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Lowers it, normal 72 hrs postpartum
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All drugs listed lower MAC except for three. What are they
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Cocaine, ephedrine, Sympathomimetics amphetamine raise them when used acutely
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List the acute treatment for MH
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1)Get help and dantrolene, shut off anesthetic,hyperventilate with 100% O2, stop procedure ASAP. 2) Give 2.5 mg/kg rapidly until s/s reversed. 3)Give bicarb to reverse met acidosis. 4) Cool pt. foley and rectal tube for cold flushes and ice and lavages to open areas 5) Treat hyperK and react to dysrhythmias 6)Follow up with labs, monitoring.
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List the post acute treatment for MH
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ICU for at least 24 hrs, dantrolene for at least 24 hrs to avoid rebound symptoms, monitor and labs, watch urine myoblobin, talk to family about their risks of MH
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What do all inhaled anesthetics do to hepatic blood flow
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Decrease it
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What do all inhaled anesthetics do to renal blood flow, GFR, and urinary output
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Increase it
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What do all inhaled anesthetics do to neuromuscular nondepolarizing blockades
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Increase the duration of them
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All inhaled anesthetics but what decrease the incidence of seizures
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Enflurane
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All inhaled anesthetics but what decrease cerebral metabollic rate
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Nitrous
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What do all inhaled anesthetics do to cerebral blood flow and ICP
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Increase it
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What do all inhaled anesthetics do to respiratory rate
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Increase it
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What do all inhaled anesthetics do to tidal volume
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Decrease it
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What do all inhaled anesthetics do to PaCO2 levels
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Increase them (except nitrous while at rest has no change)
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What effect does nitrous have on the cardiovascular system
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None
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What do all inhaled anesthetics do to BP
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Decrease it
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What do all inhaled anesthetics do to heart rate
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Increase it- Sevo n/c
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What do all inhaled anesthetics do to SVR
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Decrease it- halo and methoxy n/c
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What do all inhaled anesthetics do to CO
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Decrease it- Iso n/c
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