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84 Cards in this Set
- Front
- Back
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Patient response to inhalational ether anesthesia |
1. pupil size 2. respiratory patterns 3. patient movement 4. muscle tone |
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Stages of Anesthesia |
1. Stage 1 2. Stage 2 -Excitement stage 3. Stage 3 -Surgical Stage (4 planes) 4. Stage 4 - Medullary paralysis |
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Stage 1 |
Stage of anesthesia that involves mental depression, tolerance to painful stimulation, intact airway reflexes and amnesia increases with depth |
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Stage 2 |
* non-purposeful movement * irregular breathing, HR * dilated, divergent pupils * heightened airway reflexes *common in mask inductions *theory of disinhibition |
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Stage 3 |
* Begins with return of rhythmic breathing * Increasing depression of: - Sensory - Motor - Reflex (autonomic) - Mental |
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Stage 3, Plane 1 |
* Pharyngeal reflexes depressed * Laryngeal reflexes intact *Corneal/eyelash reflex depressed |
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Stage 3, Plane 2 |
-Laryngeal reflexes now depressed - Increased chance for aspiration
*Good for intubation |
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Stage 3, Plane 3 |
- Remaining airway reflexes depressed - Plane of "surgical anesthesia" *Target before first surgical incision is made |
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Stage 3, Plane 4 |
*Rocking boat respirations *Patient would need assistance with respirations |
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Stage 4 |
Apnea, no reflexes, fixed dilated pupils |
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Pharmacokinetics |
1. what the body does to the drug 2. the study of drug disposition |
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pharmacokinetics describes... |
1. absorption 2. distribution 3. metabolism 4. excretion |
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Absorption |
Movement of drugs across biological membranes, may be passive (no energy required) or active (against gradient) *depends on route of administration *IV, oral, IM * Oral, nasal, rectal, transdermal |
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Uncharged drugs are ____ soluble. |
lipid |
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ionized drugs are ___soluble. |
water |
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it is easier to move these drugs across membranes |
uncharged |
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degree of ionization |
*describes amount of drug present in each form (ionized vs. nonionized) *depends on whether drug is acid or base * depends on the solution the drug is immersed in |
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water is |
polar and ionized
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pKa |
An acid dissociation constant that is specific for each drug. pH at which the drug exists 50% in ionized form and 50% in non-ionized form |
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acid drug in acid solution has more drug in the ____ form |
non-ionized form |
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base drug in acid solution has more drug in the __ form |
ionized form |
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distribution |
movement of drug to site of action
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Distribution affected by these 3 things |
-local/organ blood flow -first-pass hepatic extraction - degree of protein binding |
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Metabolism |
Drug half-life Conversion of drug for excretion The rate of metabolism determines the intensity and duration of a drug's pharmacological effect. |
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Excretion |
-Renal -ionized fraction =excreted -nonionized fraction= reabsorbed |
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Pharmacodynamics |
what the drug does to the body |
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drug binds to this on a cell to produce an effect |
receptor |
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Labels of axes on curve that describes relationship between drug and pharmacologic effect |
X-axis = drug dose Y-axis = intensity of drug effect |
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How does the slope change on dose/response curve if using a drug of higher potency? |
slope becomes steeper |
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Type of drug half-life that measures effect of drug |
functional (effective) |
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Type of drug half-life that measures concentration of drug itself |
metabolic (biological) |
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first order kinetics |
certain fraction of drug reduces over time, dependent on drug concentration in the body |
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zero order kinetics |
Concentration of drug in the body does not impact the rate of metabolism. Certain amount of drug is metabolized per specific unit of time. Ex. ethyl alcohol, dilantin |
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Theory of disinhibition
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The CNS inhibitory system is anesthetized first so excitatory system dominates for some time during stage 2 of anesthesia until it too is inhibited.
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Rocking boat
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Intercostal muscles and diaphragm and thorax muscles start to work independently
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PRMM
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Ether anesthesia monitored these: pupils, respiratory, muscle tone and movement
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4 pharmokinetics
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ADME
Absorption distribution metabolism excretion |
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Fresh gas flow
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Amount or fraction delivered, what we set (Fd)
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Alveolar fraction FA
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Concentration building up in the lungs
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Inspired fraction Fi
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How much is actually going to the pt, sampling port tells us this number
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Arterial fraction Fa
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Arterial blood supply
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Dalton's law of partial pressures
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The concentration of a gas is directly proportional to its partial pressure
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Brain partial pressure/concentration is directly proportional to
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Alveolar concentration/partial pressure at equilibrium. Brain to brain at any time though.
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Factors affecting the rise of alveolar tension curves
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1. Uptake of anesthetic agent
2. ventilation changes 3. Concentration/second gas effects |
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Uptake of anesthetic agents
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A. Solubility of the agent
B. Alveolar blood flow (=perfusion=CO) C. Arterial-to-venous partial pressure differences |
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Ostwald solubility coeff
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B:g partition coefficient at 37 Celsius
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Ostwald solubility coeff
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B:g partition coefficient at 37 Celsius
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Blood gas partition coefficient
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Solubility coefficient
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Solubility coefficient
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The ratio of concentrations of the agent between the blood and alveolar gas space at equilibrium
Reflects the capacity of each phase to accept an anesthetic agent |
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Equilibrium between 2 phases means
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Partial pressures of the agent are the same in both phases so theres no net movement.
When you will get the maximum clinical effect from an agent. |
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B:G solubilities
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Metho 12
Halothane 2.5 Isoflurane 1.4 Sevo 0.69 Nitrous 0.47 Des 0.42 Xenon 0.12 |
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Calculate concentration of agent
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B= CX/(X+1)
A+B=C or C-B=A |
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Concentration formula
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B:G solubility coeff X alveolar/gas concentration = blood concentration
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Blood gas solubility tells you
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Speed of induction
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High solubility speed of induction
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Slow
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What does oil gas solubility tell you?
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Greater affinity = greater potency
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O/G solubilities of agents
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Measures agents affinity for lipid membrane.
Metho. 970 Halothane 224 ISO. 98 Sevo. 55 Desflurane. 19 Nitrous. 1.4 |
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O:G solubility is inversely proportional to dosage for the agent
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^ O:G = decreased dose needed for effect
More lipid soluble means more potent and higher solubility number |
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Mac50
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Minimum alveolar concentration at 1 atm pressure that prevents skeletal muscle movement in 50% of patients in response to a painful stimulus
* listed with at least 100% O2 or 70% nitrous |
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Mac awake
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No agent used
0.3 - 0.5 x MAC50 |
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Mac 99
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1.3xMAC
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MacBAR
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1.7-2.0 x MAC50
Blocks autonomic reflexes SE= decreased HR, BP, RR |
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MAC is inversely proportional to
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Oil gas solubility
So higher solubility means less MAC needed to get effect |
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Factors that increase MAC (HHCCP)
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Hyperthermia
Excess pheomelanin production/red hair Induced catecholamine levels Cylcosporine -depressant Hypernatremia |
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Decrease MAC
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Hypothermia
Increased age Pre-op meds Depressed catecholamine levels Alpha -2 agonists Acute ETOH ingestion Pregnancy and <72 hrs postpartum Lithium Lidocaine Opioids (neuraxial) Ketanserin- can depress CNS by blocking alpha 1 receptors, serotonin and histamine PaO2 < 38 mmHG BP < 40 mmHG CPB Hyponatremia |
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No effect on MAC
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Agent metabolism
Chronic ETOH abuse Length of anesthesia PaCO2 15-95 mmHG PaO2 > 38 mmHG BP > 40 mmHG Hyper/hypokalemia Thyroid dysfunction |
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3. Concentration/second gas effects
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Over pressuring. The higher the Pi the more rapidly the PA approaches Pi
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Alveolar blood flow is equal to
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CO in absence of shunting
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Increased CO will do what to induction time
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Slow it down
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Changes in CO have more effect on
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High solubility agents because they tend to go into the blood whilst the low solubility will stay in alveoli more
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Increased CO + low solubility
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Fast induction
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Right to left shunt
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Arterial and venous blood mixes. Low solubility gases take longer for induction to happen because too much diluting of blood and harder to build up Pa
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Arterial-to-venous partial pressure
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Difference between amount of agent in arterial and venous blood
Affected by: -tissue/blood partition coefficient - blood flow to the tissue - blood/tissue agent concentration gradient |
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Tissue groups
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1. vessel rich group - brain heart liver kidneys exocrine glands. 10% body wt but gets 75% of CO
2. Muscle group- 50% body wt, 20% CO 3. Adipose group- 20% body wt, 6% CO, high affinity for gases and harder to induce x20 4. vessel poor group -bone, ligaments, hair, teeth, cartilage. Minimal effect on uptake of anesthetic * adipose and muscle groups take longer to wear off |
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Uptake= solubility x CO x Pa-v
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If solubility is 0 then no uptake. Zero means nothing going to target tissue
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Ventilation changes
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Increasing ventilation speeds up induction. Less of an effect when using the low solubility agents since they like to stay in alveoli
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Second gas effect
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Seen with nitrous. rapid diffusion of nitrous oxide. Affects mainly high solubility agents. Combination of concentrating and augmenting tracheal inflow effects. Rapid diffusion of nitrous out of lungs causes gas to be actively drawn into the lungs (augmented inflow). Second gas is the anesthetizing gas
* faster induction |
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Also affecting uptake:
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ventilation perfusion mismatches
-affects the arterial fraction (concentration) - constriction - impedence between alveolar space and blood -pneumothorax, bronchial intubation -collapsed alveoli -longer time to clinical anesthesia/barrier -COPD, emphysema |
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Elimination of inhaled anesthetics
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-biotransformation
- transcutaneous - exhalation - main why |
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diffusion hypoxia
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fink phenomenon
- elimination of nitrous wen pt is breathing room air Causes hypoxia and hypocarbia Dilution of alveolar oxygen/CO2 levels. Need to give 100% but make sure u balance it so u dont eliminate all CO2 reserves. |
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Hypoxia
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Prepulmonary- anoxic/hypoxic
Pulmonary- Post- Stagnant- no blood flow ...CO Anemic- Hgb issues, decreased O2 Histotoxic- tissues damage /CO poisoning |
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Stages of hypoxia
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Pre-crisis stage PO2 60-55 saO2 80%
Crisis stage - po2 40-45 saO2 70% air hunger Terminal stage- po2 <25% |
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Oxygen atelectasis
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Due to inspiration of high concentrations of oxygen
Displaces nitrogen from the alveoli Alveoli collapse when oxygen is absorbed out (no nitrogen left to keep alveoli patent)! Give RA to replace N Long cases add RA to mixture |
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retrolental fibroplasia or retinopathy of prematurity
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With premies who dont have fully vascularized retinas. Increased O2 causes abnormal vascularization and fibrous tissue formation
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