ANEclear Frequently Asked Questions and Answers

Patient Physiology

Q: Does rebreathing increase the risk of desaturation?
When the rebreathing loop is fully extended tidal volumes should be above 500 ml to prevent desaturation. Because significant mixing occurs along the edges of the corrugated rebreathing loop, sufficient fresh oxygen mixes with the expired (rebreathed) tidal volume to provide adequate oxygenation.

Q: Does this device increase the work of breathing in a spontaneous breathing patient?
Since the device adds 1.8 cm H20 at 30 L/min of airway resistance to the breathing circuit, it does increase the work of breathing in the spontaneously-breathing patient. The added work of breathing is comparable to adding an additional large-diameter bacterial filter to the breathing circuit. ANEclear is typically a very small percentage of the total circuit resistance. The work of breathing can be reduced in the spontaneously breathing patient by the use of pressure support or synchronous intermittent mandatory ventilation.

Q: Will the blood pH of the patient decrease with increased carbon dioxide concentration?
Yes. pH is simply a measure of the hydrogen ion concentration. This hydrogen ion concentration is a measure of acidity. An increased hydrogen ion concentration and therefore lower pH means greater acidity. Increased CO₂ increases the hydrogen ion concentration in the blood and therefore the acidity.

Q: Is there a risk of clinically significant respiratory acidosis?
Rebreathing in the absence of an adequate increase in minute ventilation can cause the arterial CO2 concentration to rise. The rise in PaCO₂ would cause the pH to fall, resulting in respiratory acidosis. As long as there is an adequate increase in minute ventilation, there is not a risk of clinically significant respiratory acidosis.

Q: Does ANEclear work with a hypothermic patient?
Hypothermia can be defined for any patient in which the core body temperature drops below 36C. Beyond that, hypothermia is defined into three broad classes. Mild hypothermia would be a core body temperature between 35.5-35.9C. Moderate hypothermia would be a core body temperature between 35-35.4C. Severe hypothermia would be a core body temperature <35C. So, in answer to the question, for patients who are hypothermic (<36C), ANEclear has been shown to speed emergence. It should be noted that decreases in core body temperature do increase the time it takes for patients to emerge from anesthesia. Studies have not been done to evaluate the impact ANEclear has on decreasing emergence time with respect to hypothermic patients.

Q: Do you have a computer simulation of ANEclear?
Yes. We have modeled the performance of ANEclear based on our clinical trial data. For more information on the model, please contact Anecare.

Clinical Practice

Q: Can I activate and deactivate the device?
Yes. The device can be activated and deactivated. However, for safety reasons deactivation does not result in a 100% deactivated state.

Q: When should I put the device in line?
ANEclear may be placed in the breathing circuit at any time prior to emergence. ANEclear has an activation switch that engages the rebreathing loop and the agent absorber.

Q: When should I extend the rebreathing loop?
You can extend the rebreathing loop anytime prior to emergence. However, we recommend extending the loop prior to placing ANEclear in the breathing circuit to minimize the risk of inadvertently dislodging the endotracheal tube. ANEclear is changed from bypass mode to active mode by a flip of the switch.

Q: To what length should I extend the rebreathing loop?
If the patient can safely tolerate hyperventilation—with tidal volumes in excess of 500 mls—extend the loop completely. If the patient’s end tidal CO₂ rises above 55 mm Hg, increase ventilation, if possible. If increased ventilation is contra-indicated, compress the rebreathing loop.

Q: When do I activate the device?
Activate the device immediately preceding emergence.

Q: Which is more important, hyperventilation or hypercapnia?
Clinical studies have shown that hyperventilation or hypercapnia alone fails to speed emergence and that optimal performance is achieved when both are used together.

Q: Is it better to increase the tidal volume or respiratory rate?
Hyperventilation results from increases in both tidal volume and respiratory rate. The best combination depends on the patient’s pulmonary physiology and the presence of restrictive lung disease, chronic obstructive pulmonary disease, etc. The only caveat is that the tidal volume must be greater than 500 ml when the rebreathing loop is fully extended. If there is difficulty in achieving hyperventilation, check the inspiratory flow limit and inspiratory pressure limit settings on the ventilator. Tidal volumes significantly greater than 760 mls tend to slow the rate of rise in end tidal CO₂, because part of the exhaled CO₂ moves out of the rebreathing loop and into the breathing circuit. If the end tidal CO₂ does not rise rapidly, consider reducing the tidal volume and increasing the respiratory rate.

Q: Does ANEclear work if I use low-flow anesthesia?
Yes. The fresh gas flow rate during the case has no bearing on emergence. Emergence is separate from anesthesia maintenance. Emergence is a time that low-flow of fresh gases are not used and may actually be counterproductive to the goal of expeditious emergence from anesthesia. It should also be noted that when nitrous oxide is used, the fresh gas flow should be increased during emergence to enhance the washout of nitrous oxide.

Q: Does ANEclear require the use of a monitoring device of any kind?
A capnometer is required and an anesthesia gas analyzer is recommended. The sampling port of the capnometer should always be connected between the patient and ANEclear.

Q: If I use nitrous oxide during a case in which I am intending to use ANEclear, when should I shut off the nitrous oxide and why?
Rebreathing slows the rate at which nitrous oxide is eliminated. It is better to turn off the nitrous oxide several minutes before the case ends so it can be eliminated before ANEclear is activated and rebreathing begins. If the patient was on nitrous oxide and needs to be kept at a deep level of anesthesia right up until the end of the case, use increased levels of volatile agent instead of nitrous oxide.

Q: Can I use the device with just the rebreathing loop and not the absorber?
No. Use in this manner would allow elevated CO₂ levels due to rebreathing, but would also lead to rebreathed anesthetic gases, thereby delaying emergence.

Q: What minute volume value should I use?
We recommend at least doubling the maintenance minute volume. For more details, see Hyperventilation Strategies For Optimized ANEclear Performance.

Q: What happens if the tidal volume drops below 500 ml?
It is possible that if the tidal volume drops below 500 ml that an individual may possibly be rebreathing too much and may start to have lower oxygen levels because of lower oxygen supply. CO₂ may begin to increase too much and the oxygen level may begin to decrease. Excessive hypercapnia and/or hypoxia may result. If a patient persists with tidal volumes less than 500 ml, it may be possible to continue the use of ANEclear. However, the clinician should be attentive to the fraction of inspired oxygen. This value should not be allowed to drop below 35%.

Q: Can I use ANEclear with a spontaneously breathing patient?
ANEclear provides a safer and faster emergence from inhaled anesthetics in spontaneously breathing patients. With such patients, an activated ANEclear uses rebreathing of CO2 to raise the patient’s PaCO2. This respiratory stimulant increases the patient’s spontaneous tidal volume and respiratory rate, which speeds the rate of removal of the inhaled anesthetic from the lungs. The respiratory stimulant also helps the patient breathe through the LMA, endotracheal tube, or face mask, the airway filter, ANEclear and the anesthesia circuit. When ANEclear is used in spontaneously breathing patients, respiratory monitoring is needed to ensure that the patient breathes with a tidal volume of at least 500 ml. This provides adequate oxygenation during rebreathing. If the fraction of inspired oxygen drops below 35% or the oxygen saturation drops below 90%, the ANEclear should be deactivated.

Q: How do I use ANEclear with a spontaneously breathing patient?
Extend the rebreathing loop and activate ANEclear. The increased CO₂ will increase the respiratory drive and will increase minute ventilation. If necessary, you can increase minute ventilation by hand bagging or using a ventilator in a patient triggered ventilation mode.

Q: Will ANEclear work with a Laryngeal Mask Airway (LMA)?
Yes, ANEclear will help speed emergence while breathing with a LMA. Most patients breathe spontaneously while using the LMA. While using ANEclear with a spontaneously breathing patient, the clinician should be attentive to the fraction of inspired oxygen. This value should not be allowed to drop below 35%. With the rebreathing of CO2 and the elimination of anesthetic agent, the patient should increase their own minute ventilation. The amount of increase in minute ventilation is unknown given patient variability and the amount, as well as the type, of medications used. It should be recognized that LMA’s are less stimulating than an endotracheal tube and elimination of anesthetic is dependent on how much the patient breathes on their own. Therefore, time until emergence may be a bit longer.

Q: How do I optimize ANEclear performance with the LMA?
Given that most patients breathe spontaneously when a LMA is used, emergence optimization with a ANEclear means that minute ventilation should be optimized or increased. In a spontaneously breathing patient, the best way to accomplish this is with pressure support ventilation.

Q: What is the correct procedure if a patient begins to fight the ventilator at emergence?
Fighting the ventilator is a common occurrence when patients come out of anesthesia. As patients emerge from anesthesia and start to breathe on their own, the endotracheal tube and the ventilator’s controlled breaths irritate the patient. Fighting the ventilator is non-productive and may have safety implications because it limits tidal volumes and also increases airway pressures. This may be detrimental to the lungs. When this occurs, the clinician should respond as they normally would at the end of the case. Most likely this would entail turning off the ventilator. ANEclear may remain active. However, the clinician should be encouraged to place the patient on synchronous intermittent mandatory ventilation (SIMV) or pressure support (PS), if available. This will allow the machine to help augment spontaneous breaths with greater tidal volumes or possibly even “kick-in” breaths if the patient is not making an effort to breathe after the ventilator is taken out of control mode. If neither of these modes is available, the patient may remain off the ventilator with ANEclear activated so long as the fraction of inspired oxygen remains above 35% and oxygen saturations remain above 90%.

Q: When I use ANEclear to speed emergence are my patients more likely to become re-anesthetized due to leaching of anesthetics from the muscle and fat?
No. Upon cessation of anesthesia, anesthetic in muscle and fat depots returns to the lungs in the venous blood. If cleared at the lungs, the anesthetic will not recirculate to the brain. Considering isoflurane (the most soluble agent) as the worst case, anesthetic will not recirculate to the brain as long as ventilation is greater than 1.7 L/min. Lower rates of ventilation will be adequate for shorter cases and for cases where sevoflurane or desflurane are used.

Q: How is emergence from ANEclear affected by injection of fentanyl and sufentanil prior to emergence from anesthesia?
Injection of opioids, such as fentanyl and sufentanil, lower the amount of vapor needed to maintain anesthesia (MAC reduction). Opioids also lower the threshold concentrations at which patients emerge from inhaled anesthetic and can therefore delay emergence. Note that use of ANEclear can not compensate for delayed awakening caused by injection of opioids given during the period immediately prior to intended emergence.

Q: Are there intravenous anti-nausea medications (antiemetics) that can slow emergence from anesthesia?
Yes. There are certain antiemetics that can slow emergence from anesthesia due to their concomitant sedating effects. These drugs include droperidol, prochlorperazine and scopolamine. Antiemetics such as commonly used dolasetron, ondansetron and dexamthasone do not generally cause sedation.

Q: When using ANEclear, when should I extubate the patient?
Continue to use your best clinical judgment.

Q: What clinical benefits have other physicians seen when using ANEclear?
Clinicians have experienced the benefit of keeping their patients deep under anesthesia until the very end of the case without losing the benefit of an increased drive to breathe and rapid emergence. They have noted the shortened (or lack of) stage II during emergence. Many clinicians have stated that their patients seem very alert after their anesthetic when ANEclear is used. This alertness has been especially apparent after the use of isoflurane. Clinicians have also recognized that on longer cases, costs can be lowered by using isoflurane with ANEclear.

Regulatory

Q: Is ANEclear cleared by the FDA?
Yes, we have received FDA clearance to market the device in the United States.

Q: What FDA class is this device?
Class II with clinical data required.

Q: Is ANEclear CE marked?
Yes.