VETgirl Veterinary Ce: Veterinary Anesthesia Review: Part 2

Summary

In this video, Dr. Justine Lee and certified veterinary technician Rachel Bassett discuss the different types of breathing systems used in veterinary anesthesia: rebreathing and non-rebreathing systems. They explain the mechanics behind systems like the Y-piece and F-circuit, as well as the non-rebreathing Ares T-piece and Bain systems. Emphasis is placed on performing leak tests, maintaining proper oxygen flow rates, and ensuring correct reservoir bag sizing. The video offers valuable insights into the setup, pressure checking, and troubleshooting of these systems for efficient and safe anesthesia management.

Takeaways

• 😀 Rebreathing systems allow patients to inhale fresh gas (oxygen and anesthetic) and exhale waste gases (CO2), which are partially reabsorbed and recirculated back into the system.
• 😀 Non-rebreathing systems are used for small patients (under 7-8 kg), where exhaled gases are flushed out to the scavenge system due to the patient's inability to pass exhaled gases through unidirectional valves.
• 😀 Rebreathing systems have two primary types: the Y-piece and the F-circuit, with the F-circuit designed to help retain moisture and heat by utilizing exhaled gas to warm the fresh gas flow.
• 😀 To perform a leak test on a rebreathing system, close the Popoff valve, apply pressure using the oxygen flush valve, and check the manometer to ensure the system holds pressure without leaks.
• 😀 The F-circuit consists of a smaller inspiratory tube inside a larger corrugated tube, which helps maintain heat and moisture for the patient during anesthesia.
• 😀 Non-rebreathing systems, such as the Ares T-piece, rely on a high flow rate of oxygen to continuously flush exhaled gases to the scavenge system, without requiring unidirectional valves or CO2 absorbers.
• 😀 Non-rebreathing systems like the Ares T-piece use a sliding Popoff valve to manually give breaths and release pressure to the scavenge system, and they don't have a manometer for direct pressure monitoring.
• 😀 The Vane Baim non-rebreather system offers advanced features, including a manometer, allowing for easier pressure monitoring during use, and functions similarly to the Ares T-piece.
• 😀 Oxygen flow rates for rebreathing systems are typically 20-30 mL/kg/min, while non-rebreathing systems require a higher oxygen flow rate of 200-300 mL/kg/min to effectively flush exhaled gases.
• 😀 When selecting the appropriate reservoir bag size, multiply the patient's tidal volume (10-20 mL/kg) by 6 and round up to ensure proper ventilation support during anesthesia.

Q & A

What is the main difference between rebreathing and non-rebreathing systems in anesthesia?

Rebreathing systems allow exhaled gases to be processed and recirculated, while non-rebreathing systems use a high oxygen flow rate to flush exhaled gases directly into the scavenging system, typically for smaller patients who cannot handle the valves of a rebreathing system.

How does a rebreathing system work?

In a rebreathing system, the patient inhales fresh gas (oxygen and inhalants) and exhales waste gases (including CO2), which are then processed in a CO2 absorber and recycled back into the system. The majority of the waste gases exit through a scavenging system.

What is the role of the Popoff valve in a rebreathing system?

The Popoff valve (also known as the APL valve) is used to release pressure from the system. It helps expel waste anesthetic gases from the patient and can also be closed to manually provide a breath to the patient if needed.

What is the purpose of a pressure manometer in a rebreathing system?

A pressure manometer is used to measure the inspired pressure being delivered to the patient, helping to ensure that the system is functioning properly and that the patient is receiving the correct amount of airflow.

How do you perform a leak test on a rebreathing system?

To perform a leak test, cover the end of the tubing connected to the patient, close the Popoff valve, and use the oxygen flush valve to build pressure. Check the manometer for a steady reading (around 30 cm H2O) for a few seconds to ensure no leaks. If no leaks are detected, open the Popoff valve.

What is the function of the F-circuit in a rebreathing system?

The F-circuit uses two tubes—one inside the other. Fresh gas flows through the inner tube, while exhaled gases flow through the outer tube and return for recycling. This setup helps warm the incoming fresh gas, improving patient comfort.

Why is a non-rebreathing system used for smaller patients?

Non-rebreathing systems are used for smaller patients (less than 7-8 kg) because they cannot properly manage the unidirectional valves in a rebreathing system. The non-rebreathing system uses a high flow of oxygen to flush exhaled gases directly into the scavenging system.

What is the role of the slider valve in the Ares T-Piece non-rebreathing system?

The slider valve on the Ares T-Piece controls the Popoff valve. It allows you to close the valve to manually deliver a breath to the patient from the reservoir bag, and then open it to release waste anesthetic gases into the scavenging system.

How do you check for leaks in a non-rebreathing system like the Ares T-Piece?

To check for leaks in a non-rebreathing system, cover the end of the breathing system, close the Popoff valve, and use the oxygen flow meter to fill the reservoir bag. Look for any changes in the bag size or use soapy water to identify bubbles that indicate leaks.

What is the recommended oxygen flow rate for rebreathing and non-rebreathing systems?

For rebreathing systems, the oxygen flow rate should be 20-30 mL per kg per minute, with a minimum of 500 mL/min. For non-rebreathing systems, the flow rate should be 200-300 mL per kg per minute, also with a minimum of 500 mL/min.

How do you calculate the appropriate size of a reservoir bag for a patient?

The size of the reservoir bag should be calculated by multiplying the patient's tidal volume (10-20 mL per kg) by 6. Always round up to the nearest bag size. For example, if the tidal volume is 15 mL per kg for a 5 kg patient, the bag size would be 450-600 mL, so a 1-liter bag would be appropriate.