Anesthetic Equipment Ch.4 Objectives. Flashcards
Identify equipment that is used for anesthetic induction.
Anesthetic masks are cone-shaped devices used to administer oxygen and anesthetic gases to non-intubated patients via the nose and mouth.anesthesia machine, face mask, oxygen delivery system, intravenous drug syringes, monitoring devices like pulse oximeter and electrocardiogram (ECG), laryngoscope (for intubation), endotracheal tubes, airway management tools like a laryngeal mask airway (LMA), suction apparatus, and various anesthetic drugs.
Identify equipment that is used for anesthetic maintenance.
Closed rebreathing systems are normally used only during anesthetic maintenance. When these systems are used, the oxygen flow must equal only the oxygen requirements of the animal.
Identify equipment that is used for endotracheal intubation.
A laryngoscope is a device used to increase visibility of the larynx while placing an ET tube. Adequate sized endotracheal tubes.
Choose and prepare an appropriate endotracheal tube for a dog, cat, horse, or cow.
The ET tube should be no longer than the distance between the most rostral aspect of the mouth and the thoracic inlet. If longer, there is a risk that only one lung will be supplied with oxygen and anesthetic gas, or that mechanical dead space will be increased, leading to hypoxemia.
List the reasons for and advantages of endotracheal intubation.
ET tubes are commonly used for patients undergoing general anesthesia because they maintain an open airway; decrease anatomic dead space; allow precise administration of inhalant anesthetics and oxygen; prevent pulmonary aspiration of stomach contents, blood, and other material; enable rapid response to respiratory emergencies; and allow the anesthetist accurately to monitor and control patient respiration.
Describe the four basic anesthetic machine systems, and identify the parts of each system.
1). Compressed gas supply: supplies carrier gases (oxygen and sometimes nitrous oxide)
* Compressed gas cylinders
* Tank pressure gauge
* Pressure-reducing valve
* Line-pressure gauge
* Flowmeter(s)
* Oxygen flush valve
2). Anesthetic vaporizer: vaporizes liquid inhalant anesthetic and mixes it with the carrier gases.
* Vaporizer inlet port
* Vaporizer outlet port and common gas outlet
3). Breathing circuit—rebreathing (R) or non-rebreathing (N-R): conveys the carrier gases and inhalant anesthetic to the patient and removes exhaled carbon dioxide.
* Fresh gas inlet (R and N-R)
* Unidirectional valves (R only)
* Pop-off valve (R) or Overflow valve (N-R)
* Reservoir bag (R and N-R)
* Carbon dioxide absorber canister (R only)
* Pressure manometer (R and N-R with a universal control arm)
* Air intake valve (R only)
* Breathing tubes and Y-piece (R) or Corrugated tube (N-R)
4). Scavenging system: disposes of excess and waste anesthetic gases
* Waste gas port
* Transfer tubing
* Interface
* Gas evacuation system
Trace the flow of oxygen through an anesthetic machine and patient breathing circuit for rebreathing and non-rebreathing systems.
In an anesthetic machine, oxygen flows from the gas cylinder through pressure regulators, then through flowmeters where the flow is adjusted, mixes with anesthetic gas in the vaporizer, and is delivered to the patient via either a rebreathing circuit (where some exhaled gas is recycled) or a non-rebreathing circuit (where all exhaled gas is expelled) depending on the system used; in a rebreathing circuit, the exhaled gas passes through a CO2 absorber before being partially recirculated to the patient, while in a non-rebreathing circuit, the exhaled gas is directly expelled without CO2 absorption.
Describe the basic operation of an anesthetic machine.
At the beginning of each day, before using an anesthetic machine, the anesthetist must assemble the machine or machines to be used, check the oxygen and liquid anesthetic levels, check the low pressure system for leaks, and set the pop-off or overflow valve. Before each case the anesthetist must also choose between a small animal and a large animal machine, determine what type of breathing circuit to use (rebreathing or non-rebreathing), and choose carrier gas flow rates.
Describe the function and use of each component of an anesthetic machine, anesthetic masks, and anesthetic chambers.
-Anesthetic chambers are clear, aquarium-like boxes used to induce general anesthesia in small patients that are feral, vicious, or intractable or cannot be handled without undue stress.
-Anesthetic masks are cone-shaped devices used to administer oxygen and anesthetic gases to non
-intubated patients via the nose and mouth. Masks may be used for both anesthetic induction and maintenance and are often used exclusively to administer anesthetic gases to very small patients, such as birds, rats, mice, and other laboratory and exotic species, in which intubation is difficult. They may also be used to administer pure oxygen to dyspneic, hypoxic, or other critically ill patients requiring supplemental oxygen.
-The primary function of any anesthetic machine is to deliver precise amounts of oxygen and volatile anesthetic under controlled conditions to patients undergoing general anesthesia.
Explain the use of the oxygen supply of an anesthetic machine, including safety concerns associated with compressed gas cylinders.
The oxygen supply on an anesthetic machine provides a continuous flow of pure oxygen to the patient during anesthesia, acting as the primary gas source to ensure adequate oxygenation throughout the procedure; however, using compressed gas cylinders for oxygen supply presents safety concerns like potential for incorrect cylinder connection, leaks, and improper handling, which could lead to critical situations like hypoxia if not managed carefully.
Explain differences between a rebreathing and a non-rebreathing system with regard to equipment, gas flow, advantages, disadvantages, and indications for use.
A rebreathing system allows a patient to inhale some of their exhaled gases, which are filtered to remove carbon dioxide, while a non-rebreathing system delivers only fresh gas with each breath, requiring significantly higher gas flow rates. Non-Rebreathing Systems (used only for patients 7 kg or under).
Rebreathing systems are more economical with gas usage but may present challenges with ventilation, whereas non-rebreathing systems are ideal for situations where rapid changes in anesthetic depth are needed and high oxygen concentrations are required, like in emergency situations.
Identify the function and use of each component of commonly used rebreathing and non-rebreathing circuits.
In a rebreathing circuit, the key components are unidirectional valves to control gas flow, a CO2 absorbent to remove exhaled carbon dioxide, and a reservoir bag to provide a gas reservoir, allowing for efficient rebreathing of partially used gas while conserving heat and humidity; while a non-rebreathing circuit primarily uses high fresh gas flow to prevent rebreathing and typically lacks a CO2 absorbent, relying on rapid gas exchange to eliminate carbon dioxide, making it suitable for small patients where low gas consumption is desired.
Differentiate between a precision and a nonprecision vaporizer, and recognize the rationale for using each.
-Anesthetic vaporizers are classified as either precision or nonprecision. This differentiation separates those that allow precise control of the amount of anesthetic delivered to the patient (expressed as the percentage of the total gases exiting the vaporizer) from those that allow only an estimation of the amount delivered.
-Although nonprecision vaporizers can be used to deliver isoflurane or sevoflurane, as long as specific procedures are carefully followed, this practice is uncommon. In contrast, precision vaporizers (Figure 4-30) are used to deliver all commonly used liquid anesthetics including isoflurane, sevoflurane, and desflurane
Compare and contrast vaporizer-out-of-circuit (VOC) and vaporizer-in-circuit (VIC) vaporizers in terms of setup, use, and agents administered in each of these systems.
A vaporizer-out-of-circuit (VOC) setup positions the vaporizer outside the breathing circuit, meaning the anesthetic agent is vaporized into the fresh gas flow before entering the patient’s circuit, while a vaporizer-in-circuit (VIC) places the vaporizer directly within the breathing circuit, allowing the patient to inhale the vaporized anesthetic directly from the circuit itself
Identify factors that affect anesthetic vaporizer output.
Factors that affect anesthetic vaporizer output include: temperature of the anesthetic agent, fresh gas flow rate, barometric pressure, leaks in the system, saturated vapor pressure of the anesthetic agent, the vaporizer’s internal temperature control mechanism, and the type of anesthetic agent used
Explain the impact of oxygen flow rates on anesthetic concentration within the breathing circuit, changes in anesthetic depth, patient safety, and waste gas production.
A higher oxygen flow rate generally dilutes the anesthetic concentration, leading to a lighter anesthetic depth, while a lower flow rate can concentrate the anesthetic, potentially causing deeper anesthesia, but also increasing the risk of rebreathing and waste gas generation if not managed carefully
List oxygen flow rates for each common domestic species, breathing system, and period of an anesthetic event.
-Oxygen Flow Rates for Small Animals, Foals, Calves, and Small Ruminants (<150 kg [350 lb])
Chamber and Mask Inductions
Chamber induction: 5 L/min
Mask induction:
* 1 to 3 L/min for patients ≤10 kg
* 3 to 5 L/min for patients >10 kg
-Rebreathing Systems (Note: Only rebreathing systems are used for large animal patients.)
Semiclosed system after induction, during a change in anesthetic depth, or during recovery:
* Approximately 8 to 10 L/min. (This guideline represents approximately 20 mL/kg/min with a maximum of 10 L/min.)
Semiclosed system during maintenance:
* Approximately 3 to 5 L/min. (This guideline represents approximately 10 mL/kg/min with a maximum of 5 L/min.)
Closed system during maintenance:
* Approximately 1 to 2.5 L/min. (This guideline represents approximately 3 to 5 mL/kg/min.)
Explain the advantages and disadvantages of closed and semiclosed rebreathing systems.
A closed rebreathing system offers the advantage of significantly reduced anesthetic gas consumption due to complete rebreathing after CO2 absorption, while a semi-closed system allows for partial rebreathing with a lower fresh gas flow, making it slightly less efficient but often more manageable in practice; however, both rebreathing systems can present challenges with potential for increased airway resistance and difficulty precisely controlling anesthetic depth due to the rebreathing mechanism
Explain the procedure that should be followed to prepare an anesthetic machine for use.
Equipment should be inspected and prepped to ensure everything is working properly.
1. Assemble all needed supplies.
2. If using an active scavenging system, turn on the scavenging system exhaust fan.
3. Identify and weigh the patient.
4. Choose appropriately sized endotracheal tubes based on patient signalment and body weight.
5. Check the endotracheal tubes for integrity, and inflate the endotracheal tube cuffs to check for leaks.
6. If a laryngoscope is used, choose an appropriately sized blade and check the light.
7. Choose an appropriate machine (large animal [LA] versus small animal [SA]) based on patient body weight.
8. Choose an appropriate breathing circuit based on patient body weight.
9. If using a rebreathing system, choose appropriate corrugated breathing tubes (LA, SA, or pediatric) and a reservoir bag based on patient body weight (see Box 4-3).
10. Assemble the machine(s):
a. Connect the vaporizer inlet port hose.
b. Connect the fresh gas inlet hose of the breathing circuit to the vaporizer outlet port or common gas outlet if present.
c. If using a rebreathing system, attach an appropriately sized reservoir bag and breathing tubes.
d. Connect the scavenging system hoses.
11. Check that all compressed gas cylinders are correctly mounted in the yokes (E tanks) or connected to the pressure regulator (H tanks).
12. Turn on oxygen supply, check the primary and secondary oxygen supply pressure, and replace empty tanks as necessary.
13. Check the flowmeter controls to ensure proper function.
14. Check the amount of anesthetic in the vaporizer, and replenish as necessary. Ensure that the vaporizer and flowmeter are off before filling the vaporizer.
15. Rotate the vaporizer dial to ensure smooth function. Turn to “off.”
16. Check the carbon dioxide absorbent, and change if necessary.
17. Check the low-pressure system for leaks.
18. Set the pop-off or overflow valve
Describe the proper maintenance procedures for anesthetic machines and associated equipment.
As with any piece of equipment, the anesthetic machine requires periodic maintenance to ensure proper performance. In addition to routine maintenance procedures performed by hospital staff, a qualified repair professional should be contracted to examine and test all parts of each anesthetic machine on an annual basis. Removing and replacing E Tanks and parts. Vaporizers and flowmeters must be serviced and maintained. Pop-Off valves, breathing tubes and Y-Pieces as well.
