Inside the Anesthesia Machine Selection Process

Providers should demand that these critical pieces of equipment deliver inhalational agents safely, precisely and economically.

Today’s anesthesia machines are a whir of respiration readings, gas flow displays and inspired oxygen feedback, but the high-tech bells and electronic whistles are more function than form. The latest workstations can help anesthesia providers administer exact amounts of inhalational agents based on an individual patient’s needs. That light touch means patients aren’t sedated as deeply as they were in the past, so they emerge faster and are street-ready sooner. If you rely on your providers to streamline cases safely and economically, they’ll need to be sitting next to an anesthesia machine with these key features.

1. Increased safety

Newer anesthesia machines run through a series of automated checks in less than five minutes to ensure the internal circuitry is functioning properly, there aren’t leaks within the system and the ventilator functions optimally. Performing the checks manually on older machines was time-consuming. Providers would be tempted to skip the detailed check and simply pressurize the circuit to ensure there wasn’t a major leak in the breathing bag. Now, providers can prepare their workspace for the next case while the machine performs the entire automated safety check.

Fire is an ever-present operating room danger due to prevalence of fuel, oxygen and an ignition source in close proximity. Some machines let providers toggle between direct flow and total flow of oxygen, plus other carrier gases, which is especially helpful when a specific fraction of inspired oxygen (FiO2) is required. For example, when the risk of a surgical fire is heightened, FiO2 is usually limited to no more than 30%. With older machines, unless one did the math, achieving 30% often took several minutes of juggling the oxygen/air ratios until the correct value appeared. By switching to total-flow control, the provider can simply dial in an FiO2 of 30%, or whatever total flow is desired, and the concentration delivered by the machine changes with the patient’s next breath.

Fire risk is even higher during monitored anesthesia care for surgery above the xyphoid. Surgical drapes easily funnel oxygen from open sources such as nasal prongs or masks toward the bovie. In this scenario, fire could occur on the patient. In the past, pausing the flow of oxygen, and risking hypoxemia, was the only certain fire prevention option. Now, an auxiliary oxygen/air side port flow meter can minimize patient risk by delivering blended supplemental gas with a lower FiO2.

Natural disasters are becoming more commonplace. Having a machine that can continue to deliver a basic oxygen/nitrous/gas anesthetic in the absence of power makes sense.

2. Added precision

Anesthetic gas vaporizers are much more accurate, which makes it easier to fine-tune the amount of anesthetic that’s delivered. Gas analyzers also allow for the precise tracking of inspired and end-tidal concentrations of inhalational agents. Being able to accurately track the amount of anesthetic that’s delivered allows for a smoother anesthetic experience. This is especially helpful at the beginning of cases, when you’re trying to reach an adequate depth of anesthesia, and at the end of cases, when you’re lightening the anesthetic so patients emerge as surgeons place the last stitch.

Sophisticated ventilator modes function with nearly the same precision as ICU ventilators. This allows the provider to tailor the optimal ventilator mode for a particular patient’s surgery and medical condition. Older machines were limited to a simple choice of either volume control or pressure control mode. For patients undergoing laparoscopic cases with high intra-abdominal pressures, or patients who have poor lung compliance, this could raise the risk of both barotrauma and inadequate ventilation. Newer machines allow hybrid modes to ensure both optimal inspiratory pressures and adequate tidal volume. It’s extremely valuable to have the capability to dial in exact tidal volumes and pressures, and to have those settings repeat reliably.

In addition, integrated monitors that measure complex respiratory waveforms let providers notice if the patient starts to have an airway obstruction or suffers a bronchospasm. That level of performance isn’t necessarily needed for the average healthy patient, but might prove invaluable when caring for the increasing number of complex patients undergoing surgery in the outpatient setting.

3. Age-specific anesthesia

The anesthesia provider’s goal is to avoid anesthetizing patients too deeply, which can slow recoveries, or too lightly, which creates the potential for awareness. This can be challenging. The very young and the very old require varying amounts of anesthetic agents, and those amounts change depending on the agent being used. To assist in this effort, many of the modern machines display a calculated minimum alveolar concentration (MAC) of anesthetic agent based on the patient’s age. This provides real-time tracking of one important indicator of anesthetic depth to ensure it’s in the target MAC for individual patients.

4. Economy of use

The newer anesthesia machines have fewer connections and minimal leaks. This also allows for precise control over flow and anesthetic concentration to secure low-flow anesthesia (or even closed-circuit anesthesia) with overall decreased agent use. Rather than running 5-liter flows with 6% desflurane or 2% sevoflurane, you can dial the flow of gases way down to the exact amount of oxygen and inhalational agent needed.

Inhalation agents are pricey. The savings add up quickly if you can go through a day using half a bottle instead of a bottle and a half.

Some of the latest machines display calculated usages of anesthetic gases. As providers adjust gas flows, the machines display the per-hour usage of desflurane or sevoflurane in milliliters. That real-time feedback helps providers deliver the most efficient amount of anesthetic and prevent waste. Low-flow anesthesia also reduces OR contamination and limits the amount of agent vented into the environment. Inhalational agents are potent greenhouse gases, so waste has a significant environmental impact. Sevoflurane remains in the atmosphere for close to 40 years and nitrous oxide floats in the atmosphere for a century.

5. Provider safety

During induction, when it’s time to intubate the patient, providers remove the anesthesia mask. If the gas flow is left on high, the inhalational agent continues to flow into the room, where everyone is breathing it in — even if the vaporizer has been turned off. If the vaporizer has been turned off, the potential for the provider being distracted and forgetting to turn it back on is real. Health concerns over provider exposure to anesthetic waste gas is a significant issue. In the short term, exposure can cause difficulties in judgment, loss of coordination, impaired manual dexterity, drowsiness, headache, irritability, fatigue and nausea. There is evidence that long-term exposure can also cause health issues. Some of the newer machines let you instantaneously and briefly pause all flows. This allows intubation, positioning and suctioning of the airway to occur without OR contamination. To safeguard the patient, the machines turn the flow back on if the provider doesn’t do so within one minute.

6. User-friendly features

Natural disasters are becoming more commonplace. Having a machine that can continue to deliver a basic oxygen/nitrous/gas anesthetic in the absence of power is critical.

Anesthesia machines that interface with electronic medical records are great during critical cases when providers might not have the time to immediately document vital signs. The latest machines are also designed with flat surfaces, flat buttons instead of knobs and dials, and contained cords to make wiping down and cleaning the unit between cases a breeze.

New machines also assist the patient’s spontaneous ventilation. Machines help the patient safely breathe spontaneously through an LMA or endotracheal tube during a time when they would hypoventilate if they were allowed to breathe on their own. This feature can be very helpful at the beginning or end of a case, when the provider is preparing medications, positioning the patient and adjusting monitors. It lets providers prepare their workstations, helps avoid delays and allows for smoother transitions between cases. OSM