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61 Cards in this Set
- Front
- Back
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4 purposes of anesthetic equipment and breathing systems
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1. Delivery of O2
2. Removal of CO2 3. Delivery of an inhalant anesthetic 4. Mechanism for artificial ventilation |
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4 basic components of the machine
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1. Gas Source
2. Regulator 3. Flow meter 4. Vaporizer |
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Describe the overall function of an anesthetic machine
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To deliver precise, but variable concentrations of O2 and anesthetics to the breathing system and patient
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Describe the function of a pressure gauge
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Reports the pressure of a tank, which allows one to asses content of a gas container
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7) Describe the content and pressure in cylinders for O2 and N2O when full and when during in use
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O2: Initial: 2200 PSIG----Pressure drops in proportion to volume
N2O:Initial: 750 PSIG----Pressure only begins to drop after all liquid is vaporized (about 25% of volume) |
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Purpose of a Diameter-indexed Safety System
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prevent inadvertent interchange of gases while allowing for a rapid attachment of hoses to station outlets or large H cylinders
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What is a Pin-index safety system?
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Uses pins to prevent the inadvertent interchange of gases with small E cylinders
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Explain the color coding on anesthetic equipment
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O2: Green
N2O: Blue |
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Describe and locate hanger yokes on anesthetic machines
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Used to attach small cylinders to anesthetic machines
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4 basic parts of a flowmeter for oxygen
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1. Control Knob
2. Glass Tube 3. Float/Indicator 4. Scale |
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Describe the proper way to read “floats” used in flowmeters
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* Ball Float: Middle of the ball
* Bobbin Float: Top of the float |
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Describe the purpose and proper use of a flush valve
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* Flush valves allow for O2 to bypass the vaporizer and go directly to the patient, allowing for the quick administration of O2 without anesthesia.
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When should flush valves not be used?
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They should not be used with a closed or non-rebreathing system due to risk of over pressuring the patients lungs.
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the range of flow of O2 provided by a flush valve
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They deliver O2 at 35-75 L/min.
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Define the term vaporizer
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An instrument that is designed to change a liquid anesthetic to its vapor and adds a controlled amount of the vapor to the flow of gas to the patient.
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Explain why accuracy is needed for delivery of potent, volatile inhalants
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When uncontrolled, the vapor pressure may produce a maximum concentration (ISO: 32%) that is much higher than than MAC (ISO: 1.4%)
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Vapor Pressure
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partial pressure of an anesthetic gas over the liquid in a closed container
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What controlls vapor pressure?
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controlled by temperature
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Heat of Vaporization
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Number of calories to convert 1 gm of liquid to it vapor; the process of vaporization causes cooling of liquid, thus constant heat must be supplied by another material
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Specific heat
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amount of heat needed to change the temperature of 1 gm of a substance 1*C; Metals with high specific heat provide heat at a constant temperature during vaporization
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Thermal Conductivity
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measure of heat transfer; metals with high thermal conductivity maintain constant temperature of vaporization
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3 common metals in vaporizers due to their thermal conductivity and specific heat
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1. copper
2. aluminum 3. brass |
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Explain why temperature and back pressure compensation are important.
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* Temperature: The process of vaporization leads to a reduction in the anesthetic liquid’s temperature, which lowers Vapor pressure. Thus, temperature compensation of 15-35* C is desired to keep the vaporizer output constant
* Back Pressure: Artificial ventilation can causes back pressure to increase, which can lead to surges of output in the vaporizer---Compensation prevents back pressure from affecting vaporizer function |
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2 methods of output regulation for vaporizers
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1. Measured flow
2. Variable bypass |
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Describe the measured flow method of output regulation for vaporizers
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* Used in older vaporizers;
* Has two flow meters one before the vaporizers and one that bypasses the vaporizer (dilutes anesthetic gases); * Flow compensation is manual |
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Describe the variable bypass method of output regulation for vaporizers
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* Used in modern vaporizers
* Drug specific * All gases enter vaporizer, however some bypass the vaporizer chamber * Flow compensation occurs due changes in resistance to gas flow into the vaporization chamber as flow rate changes |
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2 methods of vaporization for vaporizers
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1. Bubble-through
2. Flow over |
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Describe the bubble-through method of vaporization for vaporizers
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* Used in older vaporizers
* Gases (O2) are dispersed through the anesthetic liquid by a bubble foot or dispenser (bubble up through the anesthetic liquid) |
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Efficiency of the bubble-through method of vaporization depends on what 3 things?
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1. Bubble size
2. Depth 3. Rate of gas Flow |
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Describe the flow over method of vaporization for vaporizers
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* Used in modern vaporizers
* Gas flow over the surface of anesthetic liquid * Can increase the surface area by using wicks |
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What are NOT differentials for hypoxemia?
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* Anemia
* Left to right shunt * Immune-mediated hemolytic anemia |
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What is a NEGATIVE consequence of intermittent positive pressure ventilation (IPPV)?
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Impaired cardiac function
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What is an effect of hypoventilation?
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Arrhythmia formation
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What are 2 logical causes of hypoxemia?
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* V/Q >1
* V/Q <1 |
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Cyanosis is NOT a reliable sign of hypoxemia
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Cyanosis is NOT a reliable sign of hypoxemia
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What can occur in a patient that is hypoventilating (i.e. has CO2 retention)?
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CO2 narcosis
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What is the first thing you should do if the patient's oxygen saturation as measured by pulse oximetry starts to drop?
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Check the placement of the sensor
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What is NOT a clinical sign of hypoventilation on 100% oxygen?
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Bradycardia
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What would be INAPPROPRIATE ventilation?
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Mechanical ventilation with an inspiratory time of 4 seconds
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Why is increasing respiratory rate possibly harmful to an anesthetized patient?
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It can cause decreased venous return
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Which value does NOT correspond with its correct description?
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Metabolic acidosis: BE > -4 mEq/L
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What 2 types of oxygen contribute to oxygen content?
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Bound & dissolved
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Pale mucous membranes is NOT a sign of hypoventilation
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Pale mucous membranes is NOT a sign of hypoventilation
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What is a POSITIVE effect of an elevated PaCO2?
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Shifting the oxyhemoglobin dissociation curve to the right
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When do patients buck the ventilator?
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* When anesthesia is too light
* When they become hypercarbic * When they become hypoxemic |
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What drug is contraindicated in stallions but not mares?
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Acepromazine
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A patient with life threatening uncompensated systemic disease is which ASA classification?
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Category IV
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Based on the ASA patient classification scheme, a dog with a skin tumor who is otherwise healthy would be classified as:
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Category II
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Your job as an anesthetist is to “not kill anything”. Your yardstick for success will change as your knowledge base and skill improve.
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Your job as an anesthetist is to “not kill anything”. Your yardstick for success will change as your knowledge base and skill improve.
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An animal having a routine spay is a category
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I
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When is the MOST appropriate time to administer analgesia in relation to surgical procedures?
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Before surgery
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A hyper excitable state of the spinal cord that results in the volley of afferent impulses in the spinal cord activated by nociception is referred to as:
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Windup
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Behavior, physiologic response, expectations, response to therapy, and pain score are used to determine if a patient requires analgesic therapy.
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Behavior, physiologic response, expectations, response to therapy, and pain score are used to determine if a patient requires analgesic therapy.
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Precision vaporizers
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vaporizer-out-of-the-system
* Patient does no breathing through the vaporization chamber * High resistance; able to be used for all inhalant anesthetics; safer * Need precision and high efficiency vaporizers |
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Non-precision vaporizers
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* Patient breathes through the vaporization chamber
* Require a low resistance vaporizer; used with ether and methoxyflurane * Increase patient ventilation increase inspired anesthetic % |
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“heat sink”
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vaporizer with lots of heavy metal that is thermo-stable
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Differentiate between agent-specific and multipurpose vaporizers
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* Agent-specific: made specifically for a single anesthetic agent; color-coded (safer machines)
Multipurpose vaporizers: Used in research setting mostly, accurate vaporizers, but require attention to flow rates |
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Breathing system
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serves to deliver O2, remove CO2, deliver anesthetic, and act as mechanism for artificial ventilation
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Rebreathing system
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breathing system in which all or part of exhaled gases are retained within the system to be re-inhaled by the patient
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Non-rebreathing system
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breathing system in which no part of the exhaled gases are retained in system
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Closed, low-flow, and semiclosed systems are types of rebreathing systems which differ on FGF rate
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Closed, low-flow, and semiclosed systems are types of rebreathing systems which differ on FGF rate
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