Anesthesia Machine Evaluation PDF

**Name: Date:** **Hospital: Grade: /100** **Anesthesia Machine Evaluation (29pts)** - Be able to demonstrate the flow of oxygen from the oxygen tank to the patient and out for both the rebreathing and nonrebreathing system 5pts- **Rebreathing** = from the oxygen tank to the flowmet...

**Name: Date:** **Hospital: Grade: /100** **Anesthesia Machine Evaluation (29pts)** - Be able to demonstrate the flow of oxygen from the oxygen tank to the patient and out for both the rebreathing and nonrebreathing system 5pts- **Rebreathing** = from the oxygen tank to the flowmeter, to the vaporizer, through the fresh gas inlet and outlet port, into the reservoir bag, through the inhalation valve, into the patient, through the expiratory valve, into the CO2 absorber canister, and the excess goes through the scavenging system **Non-rebreathing** = From the oxygen tank to the flowmeter, to the vaporizer through the gas inlet and outlet ports, into the reservoir bag, through the tube into the patient, back out of the patient through the overflow valve and to the scavenging system - Be able to give proper names of the breathing systems when appropriate 2pts **Rebreathing circuits** are used on patients more than 7kg Can be used in smaller patients with a pediatric hose Use low flow rates of \~20-40ml/kg/min Changes in anesthetic depth are slower It uses all parts of the anesthesia machine (does not bypass the CO2 absorber canister) **Non-rebreathing circuits** are used on patients less than 7kg Patient receives fresh oxygen each breath Uses high flow rates \~300-500ml/kg/min Changes in anesthetic depth are faster Does not utilize the CO2 absorber canister Advantage is that there is less resistance to breathing and less mechanical dead *space (f you try to breathe through a very narrow tube (i.e. a tube with high resistance) you have to use more effort, so you increase the work of breathing. Under anaesthesia this does not happen due to muscle relaxation, and instead the patient is prevented from ventilating properly (hypoventilation), resulting in increased arterial and end expired carbon dioxide levels. Larger and fitter patients have stronger respiratory muscles and can cope better with\ resistance in the breathing system.)* - Be able to connect rebreathing and nonrebreathing (if for some reason they do not have both you still need to be able to describe) 5pts **REBREATHER Universal F Circuit,** expiratory tube is within the inspiratory tube, which allows expired gases to warm up inspired gases as they pass through **NONREBREATHER Mapleson F systems (Jackson rees and Norman elbow)** have fresh gas inlet by the patient connection, have reservoir bag at the opposite end (at bandfield machine our bag is connected to the machine) **Main difference between Jackson and Norman** is that the norman has the fresh gas inlet inside the patient connection - Be able to describe the parts of the anesthesia machine used in a rebreathing versus a nonrebreathing system 5pts In **rebreathing** all of the parts of the machine are used, whereas in a **nonrebreather** it bypasses the CO2 absorber canister, unidirectional valves and pop off valve, and the O2 flush, at my banfield, they are fancy and they have the bag connected to the machine so the O2 flush valve can still be used. Nonrebreather also relies on the scavenging system only for removal of waste anesthetic gases, at my banfield we use an active scavenging system which utilizes tubing that goes through the ceiling and exits to the environment - Discuss how the size of the reservoir bag is determined (even if they do not change it) and be able to explain 5 pts- The reservoir bag **size** is determined via a calculation. Which is **kg x 10-20mL/kg (Tidal volume) x 6 / 1000** The **reason** we must make sure the bag is the correct size is because if the bag is too small, it may not provide adequate tidal volume for the patient, leading to hypoventilation and inadequate oxygenation. Conversely, if the bag is too large, it may be difficult to observe the patient\'s breathing patterns, and manual ventilation may be less effective, increasing the risk of barotrauma or inadequate ventilation. - Explain the function of the soda lime and the different ways to determine if it is viable 5pts- The **function** of soda lime is to absorb CO2 from the exhaled gases in a **rebreathing system**. This allows the anesthetic gases to be recirculated and reused, reducing waste and preventing CO₂ buildup, which can lead to **respiratory acidosis and hypercapnia** in the patient. **You can determine if it is viable by:** -Checking how many hours of use it has had, change it after 8 hours or after 1 month has passes, at my banfield we do it monthly so only the date is recorded on the canister, whereas at school we mark how many hours we use it on the canister. -Checking the color, according to Dr. Larin, not all granules turn purple, but if they do, that is a sign that they have been exhausted. They can also revert to white after no longer in use. -Lastly, we check if the granules are hard and brittle. - Describe how excess gases are captured 2 pts **Excess Anesthetic Gases (WAGS)** exit via a scavenging system These systems can be active or passive. The one we have at Banfield is active, meaning that they are captured by a tubing that goes through the ceiling and exits to the environment. At school we have a passive system that basically works with gravity, the gases are captured in the tube and flow down to the activated charcoal canister. You know this canister needs to be changed when it has gained 50g over the initial weight. **Closed, Semi --open and open systems (10 pts)-** - What is the determining factor that decides if a breathing system is closed, semi closed or open 5pts The determining factor that decides whether a breathing system is **closed, semi-closed, or open** is the **fresh gas flow rate relative to the patient's oxygen consumption**. **The closed system** matches the patients metabolic oxygen consumption which is around 7ml/kg/min. It is economical, as less oxygen and anesthetic gas is used, but not used in practice as pressure can build up and damage the patients lungs (pop off valve is closed) It is used primarily for large animals. **The semi-closed system** is the partial rebreathing system, the **fresh gas flow** is higher than the patients oxygen consumption, around 20-40ml/kg/min and is used for rebreathing systems. It is economical, provides humidification, and warmth, but breathing resistance builds up, which is not ideal for small patients. **The open system** is the non-rebreathing system, the **fresh gas flow** greatly exceeds the patients oxygen consumption, using around 300-500ml/kg/min. It is used for small patients to prevent resistance to breathing. - Advantages and disadvantages of each 5pts- **The closed system** **Pros-** conserves anesthetic gas and oxygen which is cost effective, it has minimal waste gas which is good for the environment, it preserves heat and humidity which makes it beneficial for long procedures, and has stable anesthetic depth once equilibrium is reached **Cons-** it requires precise control and can easily build up pressure that can damage the patients lungs, it is complex to manage and more adjustments are needed. **The semi closed system** **Pros-** Allows faster anesthetic depth adjustments compared to the closed system, reduces waste gas compared to the open system, preserves some heat and humidity. **Cons-** more gas waste than the closed system, there is more breathing resistance compared to the open system, requires CO2 absorber canister and regular replacement if needed, may cause damage to lungs if pop off valve is left closed **The open system** **Pros-** Minimal breathing resistance which is ideal for small patients under 7kg, faster induction and recovery due to high flow rate, simple set up that does not require CO2 absorbing canister, and has lower risk of rebreathing CO2. **Cons-** High gas flow rate is required which is more expensive, there is increased environmental pollution due to waste gas, there is loss of heat and humidity which puts the small patient at greater risk of hypothermia **Troubleshooting the machine 25pts- 5 each** 1. Bag too full- The bag could be too small for the patient, should recalculate bag size or opt for the higher end of the calculation (20ml/kg/ml rather than 10ml/kg/min). The pop off valve could be closed, check it and open if so. The flow rate could be too high, adjust it so that it is not. There could be an obstruction in the scavenging system, check the system. 2. Bag to flat- Bag might be too big for the patient, should recalculate bag size or opt for the lower end of the calculation (10ml/kg/ml rather than 20ml/kg/min). The flow rate might be too low, adjust flow rate so that it is not. There could be a leak in the machine or the bag, a leak test should always be performed If there is a leak AFTER induction -- check that the patients ET tube is correctly placed, is the correct size, and is inflated properly, also check that everything on the machine is connected properly. 3. Leak in system- A leak test should always be performed prior to using the machine. If there is a leak: Check or change the breathing system Check or change the reservoir bag If all else fails, use soapy water and apply it to the machine, bubbles should form where there is a leak. If there is a leak AFTER induction -- check that the patients ET tube is correctly placed, is the correct size, and is inflated properly, also check that everything on the machine is connected properly. 4. Patient waking up- Assess the patient and the vital signs Deduce if the anesthetic gas is too low and if the procedure is painful Determine if the ET tube is placed correctly or if there is a leak in the machine 5. Calculation of tidal volume and minute volume -- The **tidal volume** is the volume of air the patient inspired in one breath, typically **10-20ml/kg** The **minute volume** is the volume of air that the patient inspires in one minute, calculated as **tidal volume x respiratory rate / 1000** **Vaporizer (6pts)** - Gas used 1pts Sevoflurane is used, its preferred over iso because it has a lower blood gas partition coefficient which means that it has a faster onset and recovery time. - Precision or nonprecision and why 1 pts We use a precision vaporizer because we are able to set a specific percentage of anesthetic gas that is delivered to the patient - Describe MAC-define and why is it useful to know 4 pts **It is** the minimum alveolar concentration, which measures the potency of the inhalant anesthetic. It is basically the concentration of anesthetic gas in the alveoli that prevents movement in 50% of patients in response to standard surgical stimulus, such as an incision. Lower MAC means more potent anesthetics and lower concentrations of the drug are required to achieve the desired effect. Higher MAC means less potent anesthetic, and higher concentrations of the drug are required to achieve the same effect. It is **useful to know** because knowing the MAC helps determine the proper anesthetic concentration needed to ensure the patient is adequately anesthetized throughout the procedure. Understanding MAC helps us avoid over or underdosing, which prevents complications such as **hypotension, hypoventilation, or anesthesia awareness**. **The MAC for SEVO** for dogs = 2.36% and for cats = 2.62% **Monitoring equipment (20pts)** **Describe what the equipment monitors and how that information helps you determine the depth of anesthesia;** Be able to recite normal values for the following**:** 4pts ec 1. SpO~2~ Monitors the percentage of oxygen concentration in the hemoglobin, monitored by a pulse oximeter The value tells us how well the patient is oxygenating Normal value is \>95% Values below 95 indicate patient is hypoxemic and might need to be manually ventilated. 2. Temperature- Monitored with a thermometer, either handheld or attached to the multimodal monitoring machine Normal temperature is between 99.5F-102.5F Hypothermia is **commonly seen due to:** Anesthesia lowering metabolic rate, cold oxygen especially with higher flow rates, in cold environment through conduction, or through open body cavities or shaved fur areas due to convection, as well as vasodilation caused by drugs used. Hypothermia is dangerous because it **causes:** Cardiovascular issues, as body temp drops, heart rate slows down which can reduce blood circulation and oxygen delivery issues. Increases the risk of arrhythmias, as it can disrupt the normal electrical conduction of the heart. It leads to slower anesthetic recovery, since drugs will be metabolized and eliminated more slowly at lower temperatures, prolonging recovery time. It also impairs the function of platelets and clotting factors. It can also reduce organ function, as the kidney, liver and brain rely on normal body temperatures for optimal function. 3. Blood pressure- Can be measured directly or indirectly. **Direct** is through an arterial catheter **Indirect** is through a doppler or oscillometric device **Normal values:** **Systolic:** 90-140 mmHg DOG 120-170 mmHg CAT **Diastolic:** 50-90 mmHg DOG 70-120 mmHg CAT **MAP:** 90-120mmHg It is the best indicator of tissue perfusion It is the average pressure in a patient\'s arteries during one cardiac cycle (both systole and diastole). It provides an overall picture of the perfusion pressure (blood flow) that is being delivered to vital organs and tissues. 4. End Tidal CO~2~- The amount of carbon dioxide released at the end of exhalation It indicates how well a patient is ventilating Normal **value** is 35-45 mmHg It is measured by a capnograph **Hypercapnia** means hypoventilation **Hypocapnia** mean hyperventilation 5. ECG- The ECG is measured by a standalone ECG machine or a multimodal monitoring machine. It tracks the electrical activity of the heart through electrodes that we place on the patients skin. It provides information about the hearts rhythm and rate. It can show us the heart rate, **low heart rate or** **bradycardia** can be an indicator that the anesthesia is at a deeper level, if it drops too low it can be harmful and we need to adjust the anesthetic level or intervene with drugs like atropine to increase the heart rate. It can show us **arrhythmias** an increase in arrhythmias can indicate excessive depth of anesthesia, meaning that we need to lighten the anesthesia or correct the underlying cause of the arrhythmia. If the heart rate **increases** it can be due to surgical stimuli, indicating that the patient is too light, which means we need to adjust by increasing the anesthetic depth. **Be able to discuss preanesthetic drugs used in your clinical rotation (10pts)-** - Indications - Additional side effects - Contraindications