Focusing on supply costs and provider rates can trim the fat off your anesthesia budget, but don't ignore the potential savings in limiting the flow of desflurane, sevoflurane and isoflurane — 3 commonly used and costly volatile gases. Consider these gas-saving strategies to improve your bottom line and increase surgical efficiencies without compromising patient outcomes, safety and satisfaction.

1. Choose a cheaper or more efficient agent.
The "pharmacoeconomics" of costly volatile inhalational agents is a frequent topic of discussion among healthcare providers looking for ways to reduce the cost of surgery. In answering this question, you must consider both the direct costs (price of the liquid per milliliter) and the indirect costs (the properties of the drug, including speed of induction and emergence, which may affect patient discharge times) associated with these agents.

But don't go on price alone (see "Comparing the 3 Volatile Inhalational Agents"). Determining the cost of one volatile anesthetic agent over another requires you to weigh the following factors:

• Cost per milliliter. Desflurane, sevoflurane and isoflurane vary widely in price. My calculations for the cost of these drugs last month (based on the Federal 340B drug pricing program) had isoflurane as the cheapest at about $12 per 250ml bottle, compared to sevoflurane at $67 per 250ml bottle and desflurane, the priciest, at $148 per 240ml bottle.
• Drug solubility. Affects the speed of induction and emergence. The lower the solubility of the gas in the blood, the faster the induction, emergence and possible discharge for the patient. Desflurane is least soluble (0.44), followed by sevoflurane (0.69) and the most soluble, isoflurane (1.4). This means that desflurane provides the quickest and isoflurane the slowest induction and emergence.
• Potency. Potency is measured by Minimal Alveolar Concentration (MAC) and is measured as a percentage. Desflurane has the highest potency at a MAC of 6%, followed by sevoflurane (1.85%) and isoflurane (1.15%).
• Pungency. This describes the degree of airway irritation each drug produces in the patient. While not related to cost, this may be an important consideration in your choice of volatile anesthetic in certain cases. Sevoflurane is by far the easiest to inhale, making it the drug of choice for inhalation inductions, particularly in children. Although some studies refute the claim that desflurane irritates the airway, most anesthesia providers believe that sevoflurane is less pungent and prefer it for inhalation induction.

Comparing price alone, isoflurane emerges as the real bargain of the bunch. At less than $12 a bottle, it's an excellent drug with no real significant outcome differences. However, isoflurane is the most soluble of the 3 gases and therefore is theoretically slower in and out of the patient. A skilled, attentive and experienced anesthesia provider may be able to overcome these challenges by harnessing some of the other strategies I'm about to discuss to limit the drug's impact on induction, emergence times and discharge eligibility times.

2. Minimize the fresh gas flow.
Your anesthesia providers can reduce the amount of volatile gases used in a case by minimizing the fresh gas flow (FGF), the rate of liters of oxygen or air being delivered per minute via the anesthesia machine. The minimum flow permissible when using sevoflurane is 2 liters per minute. However, it's safe to use 1 liter of FGF or less for desflurane and isoflurane. Lower FGF significantly decreases the volume of liquid used per minute, which can significantly improve the economic profile of the more costly agent, desflurane, as well as the already cheaper isoflurane. "Cost for 1 Hour of Inhalation-al Anesthesia" compares the direct cost of the 3 inhalational agents for 1 hour of anesthesia at different flow rates.

The problem with this strategy is that many anesthesia providers aren't comfortable with delivering only 1 liter of FGF, preferring to use higher gas flows, which unfortunately are wasteful during the maintenance phase of anesthesia. One argument against minimizing FGF is that it results in faster depletion of soda lime granules used to remove carbon dioxide from the breathing circuit. While this is true, these granules are relatively inexpensive, and many facilities change them weekly regardless of signs of depletion.

3. Supplement with other agents.
Adding an intravenous agent, such as propofol, or nitrous oxide during inhalational anesthesia can help reduce the amount of volatile agent you'll have to use. Nitrous oxide is a very affordable gas that can be an excellent choice for selected patients and selected surgeries. However, some anesthesia providers use it sparingly, since it can increase the incidence of PONV and as a result can prolong patient time to discharge.

4. Use a BIS monitor.
There is some evidence that titrating the anesthetic agent to the bispectral index (BIS) of 60, which you can determine with a special brainwave activity monitor, can significantly reduce the amount of inhalational agent used for a case (at least 1 study has shown a reduction of up to 38%). However, if your facility doesn't already have a BIS monitor, this is an upfront cost you'll have to consider (these monitors can run more than $1,000), as well as the per-case cost of BIS monitoring strips.

Proactive approach
Make sure your anesthesia providers are taking proactive steps to reduce these costs, whether it's by switching to a lower-cost agent, titrating doses with the help of brainwave monitoring or reducing their fresh gas flows — or, ideally, a combination of these strategies. A motivated anesthesia provider should be able to lower costs without compromising patient safety.