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10 Secrets Of Veterinary Anesthesia Machines

Increase patients’ safety while they’re under anesthesia, and boost your machine’s efficiency.

Figure 1: Soda lime typically needs to be changed every 12 hours’ worth of anesthesia, unless your brand specifically states otherwise. Photos courtesy Phil Zeltzman, DVM
Fig. 1

Research your soda lime

Soda lime typically needs to be changed every 12 hours’ worth of anesthesia, unless your brand specifically states otherwise.

In theory, soda lime should be changed when two-thirds of the canister has changed color. It contains a dye (ethyl violet) that turns purple when the granules reach their CO2 absorbing capacity.

But don’t go by the change of color alone. It can be very misleading. For the safety of your patients, research the exact requirement of the brand of soda lime you use.

There are low-flow and highflow types. Their change in color is not at all universal (Figure 1).

Also, most of the concentrated exhaust goes up through the middle of the canister. Therefore, the center of the granules may be changing colors while the outside remains white.

Bottom line: keep track of time to assess the safety of your soda lime. There are many options. Use a sticker with boxes. Each box crossed-off represents 15 minutes.

At the end of each procedure, the technician must remember to cross off the required number of boxes. When all boxes are full, based on your particular soda lime, change it.

(Note that the correct spelling is soda lime, and not soda Lyme or a variety of other creative versions.)

Effective leak testing

Leaks are not uncommon, including from the soda lime canister and anesthesia hoses.

You can use soapy water to check for gas leaks at any of the multiple connections in your anesthesia system, but it can be hard to see bubbles on top of a soapy solution. In addition, soap leaves a residue that must be rinsed.

An even better solution is to use Snoop Liquid Leak Detector to pinpoint leaks.

Figure 2: Testing for leaks.

Fig. 2

Effective leak testing, part II

Do you test your machine for leaks at the beginning of your day, or, even better, before each procedure?

Most technicians do the following quick leak test:

  • Close the pop off valve;

  • Place a thumb over the end of the anesthesia hose;

  • Push the oxygen flush valve to fill the reservoir bag to a pressure of 20 centimeters H2O; and

  • Wait a few seconds to see if the needle of the pressure gauge drops.

But there is an even better way:

  • Close the pop-off valve;

  • Place a second bag at the end of the anesthesia hose; and

  • Push the oxygen flush valve to fill both bags to centimeters H2O.

This method will test two bags at once (Figure 2). In addition, using a higher pressure may reveal smaller leaks missed with the usual technique.

Either way, please test your anesthesia machine. At worst, it can avoid intraop problems; at best, you can save a life.

Hoard spare parts

Sometimes, it’s good to be a hoarder. It can help you replace damaged parts of a machine until repairs can be done professionally. Store spare parts such as tubing end pieces, random parts of an old machine, connectors and replacement bags and hoses. These small parts also can come in handy when you work with wildlife or exotics species.

Fire (your) hose

Hoses and tubing are warm and moist, making them perfect breeding grounds for bacteria. In fact, you may see discoloration or mildew through clear hoses, but you have no idea what’s growing inside a dark hose. Conclusion: Change hoses regularly.

Use the right spout

Isoflurane and sevoflurane bottles have specific pour spouts, as do vaporizers. Your maintenance specialist should be able to tell you what you need. You should care so you don’t overfill your vaporizer and so you don’t spill gas … and inhale it.

Refill a vaporizer when there are as few people as possible in the area, like early morning or in the evening.

Pop off

One of the worst things anyone can do is leave the pop-off valve closed with a patient under anesthesia. Avoid serious trouble by installing a “quickrelease pop-off valve” or “pop-off occlusion valve” (Figure 3). Once you do that, you will never have to struggle to close and open the pop-off valve multiple times to “breathe” for a patient. Instead, you will simply hold a button down while you give a breath.

Installation is easy enough that you can do it yourself, or ask your anesthesia technician to do it. If it’s truly impossible to install the safety valve, place a skinny strip of colored tape at the bottom of the pop-off valve knob so you can know at a glance that it is open.

Fig. 3

Cuffer puffer

Murphy’s Law says that you will not find a “dry syringe” aka “air syringe” aka “cuffer puffer” when you need it the most. Always have one on your machine. If you’re lucky, it has a convenient place for it. If not, tape a plastic syringe case to your machine. Mark your dry syringes with bright tape so nobody gets rid of them.

Machine inspections

AAHA requires yearly inspections of anesthesia machines. Even if your hospital is not AAHA certified, tune your machines yearly. Find an anesthesia machine maintenance specialist who can do a thorough yearly inspection. In addition, make sure he can help you quickly in case of technical difficulties.

Oxygen “flush” valve

When a patient “wakes up” in the middle of an anesthesia episode, people often push the oxygen valve to quickly inflate the breathing bag in order to give a few breaths. Sadly, this is completely counterproductive. Why? The flush valve sends oxygen to the bag but bypasses the vaporizer. So what reaches the patient is pure oxygen at a flow rate of 35 to 75 liters per minute (instead of say, 1 liter per minute).

The only two times you should use the oxygen flush valve are when you are leak testing your machine, as explained above, or when you want to wake your patient up. But definitely not when you are trying to get a patient under deeper anesthesia.

By: Dr. Phil Zeltzman is a board-certified veterinary surgeon and author. His traveling practice takes him all over Eastern Pennsylvania and Western New Jersey.

Kelly Serfas, a certified veterinary technician in Bethlehem, Pa., contributed to this article.

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