How to Buy a Monitor

If you are in the market for a new monitor or will be soon, get ready to be bewildered. There is a plethora of models available from a panoply of vendors, all with different configurations, features and prices. To make choosing the right one for your facility somewhat less challenging, we asked experts to break monitors down to their most basic elements and provide some advice and understanding. Here's what they said about:

Pulse Oximetry
This monitoring function, which measures changes in arterial hemoglobin oxygen saturation by shining an infrared light through vascularized tissue, has been called the most effective monitor of the respiratory and hemodynamic functions. It is one monitoring function that is absolutely necessary to do on every patient, both in the OR and the PACU.

Although every monitor contains pulse oximetry of some sort, there are at least two factors managers should take into account when evaluating this particular aspect of the monitor.

The first is whether or not to purchase a monitor with the ability to filter out signal contamination.

Pulse oximeters are particularly prone to "noise." Movement on the patient's part, a problem in pediatric cases, can produce false positives. Accuracy can also decrease with low blood flow to the sensor site, as in patients with severe peripheral vascular disease, says Alan Kwon, MD, Medical Director for the Kennedy Surgical Center in Sewell, N.J. Furthermore, the pulse oximeter cable that carries the light signal can act like an antenna and pick up stray electrical signals such as those produced by electrical cautery.

Today, you can buy pulse oximeters with adaptive filters similar to the ones routinely used in the telecommunications industry. Masimo Corporation and Mallinckrodt, Inc. both make software for this purpose.

Experts disagree about whether you really need this technology, particularly if it costs extra.

A paper to be presented at the American Society of Anesthesiology indicates that false alarms from signal noise may render monitors dysfunctional for more than five minutes during every case, requiring the attention of the anesthesia professional and interrupting efficiency. Russell Brockwell, MD, an anesthesiologist and assistant professor at the University of Alabama at Birmingham, believes the technology is especially worthwhile if you handle a lot of pediatric cases, as kids are prone to move during surgery.

Others are more skeptical. Although Adam Dorin, MD, Medical Director and the Chief of Anesthesia for the Surgery Center of Chevy Chase in Maryland, thinks such technology is "clearly valuable," he believes all of the pulse oximeters available on the market today are adequate. Advanced monitors "may be nice, but they aren't necessary," he says. Both Dr. Kwon and Paul Gubbinni, MD, the Chief of Anesthesia for Morton Plant North Bay Hospital and for the Trinity Outpatient Center, both in Florida, agree. Dr. Gubbinni says he prefers "monitors that are solid, safe, and as inexpensive as possible."

Another decision is whether to invest in one of the new hand-held pulse oximetry devices on the market. These may be appropriate for small procedure rooms or for emergency use, reports Dr. Dorin, who says "I highly recommend them," and adds that at about $600, they're cheap. Dr. Kwon disagrees, stating that most hand-held units are generally not necessary. "I'd rather put my money towards a smaller monitor that could accomplish several functions," he says.

Electrocardiogram
Electrocardiograms, visual records of the mechanical activity of the heart as it contracts, may be the next item to consider.

One question to ask is how many leads you need. The more patient leads an electrocardiogram has, the more exact the image it will record.

Our experts recommend the following plan. If you will only have one monitor in your center, consider buying the full-blown 12-lead model. Dr. Dorin says you will want to use this on older patients, patients with a long history of smoking, patients who have experienced prior cardiac problems and certainly patients who experience cardiac events in the OR.

For your other monitors, three- to five-lead models will likely work fine, says Nancy Burden, RN, director of Trinity and Bardmoor Outpatient Centers in Florida. Dr. Kwon recommends opting for the five-lead version, explaining that lead II and V-5 are responsible for detecting greater than 80 percent of ischemic events. If you don't have V-5 leads, you should at least have the ability to monitor modified "V" leads, he suggests.

Another question to consider may be whether to choose an EKG with the ability to analyze arrythmia, a feature called ST segment analysis. Dr. Dorin favors this feature, saying that although it can cost thousands more, it is helpful in picking up arrythmia, a sign of heart block and other problems. Dr. Kwon feels that he would spend the money only if the patient population tended to be older and the center performed lots of intra-abdominal procedures under general anesthesia.

Capnography
Capnography, the measurement of CO2 concentrations in respiratory gases, is one of the most useful monitoring functions in general anesthesia. Monitoring of end-tidal CO2 helps the anesthesia professional be sure that the patient's respiratory system is working smoothly; high levels of CO2 may indicate an opioid induced depression of the respiratory system, says Barry Friedberg, MD, a clinical instructor of anesthesia at the University of Southern California. Additionally, high CO2 levels are one of the earliest indicators of malignant hyperthermia; as the metabolism speeds up, CO2 levels increase. Low levels, on the other hand, provide an alert to potentially life threatening situations such as a missed intubation or disconnection of the breathing circuit, says Dr. Kwon. They also signal the anesthesiologist to watch out for arrhythmia and asphyxia, Dr. Dorin adds.

Another question is whether you need a mass spectrometer, which can specifically identify and monitor anesthesia gas concentrations. Dr. Dorin feels these are a luxury for most outpatient surgery facilities. "Mass spectrometers are more suited for use in an academic environment in which anesthetic technique is being taught, not for practical, clinical use in an outpatient surgery setting," he says. "Even the simplest end tidal CO2 machines now integrate additional hardware with the ability to detect different respiratory agents and anesthetic gases, even if they can not automatically name the agents." Most of these devices permit the user to key in the agent's name, if desired, he says.

If you are not sure whether you need this feature or not, Dr. Kwon suggests purchasing a quality base monitor that can be adapted for more complex tasks such as anesthetic gas analysis with the addition of modules to the platform.

Temperature Monitoring
The main function of temperature monitoring is to guard against hypothermia, a real threat for anyone undergoing general anesthesia. Hypothermia causes shivering, leading to dramatically increased oxygen consumption and possible cardiac ischemia.

If your facility only does procedures that last less than 20 minutes and are done under local or regional anesthesia, it's probably not necessary to measure temperature unless you expect some radical change for some reason, says Dr. Kwon. However, if you do general anesthesia, you must monitor temperature, he says.

Experts disagree about the best way to monitor temperature.

Connie Hale, MD, an anesthesiologist at the Mease Countryside Surgery Center in Florida, recommends considering esophageal temperature monitoring rather than conventional skin monitoring; the former is more accurate since it is closer to core temperature. Dr. Dorin agrees that your monitor should have a port for esophageal monitoring and says most do. However, he rarely uses his, explaining that he feels it's necessary only in the event of a complication. Dr. Friedberg agrees. He asks, "why put your patients through an uncomfortable process unless it is absolutely necessary for their safety and the efficiency of the procedure?"

The display
Although the screen may seem like one of the more prosaic features of a monitor, in fact it's quite important, says Ms. Burden. Make sure the display allows your anesthesia team to read the monitors quickly and easily.

Ms. Burden happens to like customizable screens, which allow your anesthesia staff to make the numbers larger or smaller.

Nathan Schwartz, MD, chief of the anesthesia and pain management departments at Coordinated Health Systems in Lehigh Valley, Pa., likes multi-colored screens. He says the more colors the screen has, the easier it is to differentiate the information.

Additionally, keep in mind that some screens are more capable of reducing glare than other screens. If you have difficulty viewing the display when it is at a 90-degree angle, Dr. Schwartz advises, you should consider alternative monitors; the most efficient monitor is useless if you can not easily read its data.

Computer compatibility
Many monitors now feature a port so that you can offload data from the case to a medical records system. Whether you will need it is another controversial issue, with most of our experts expressing skepticism.

Dr. Dorin fears that a heavier reliance on computer-based records will necessitate anesthesiologists defending and explaining their actions almost on a routine basis. He states that monitoring is still very prone to inaccurate and misleading readings. For instance, if a pulse oximeter has to be placed on the same arm as a blood pressure cuff because surgery is being performed on the other arm, a false pulse oximeter reading will occur every five minutes when the cuff activates.

Dr. Kwon also feels skeptical about the value of such ports, pointing out that they are expensive and not more accurate than pen and paper.

Portability
Under some circumstances, portability can be a real asset, says Dr. Kwon. A high-volume eye surgery center in which he worked hooked inexpensive portable monitors to the IV poles on the stretchers, and kept the monitors with the patient from pre-op through PACU.

In most outpatient surgery facilities, though, Dr. Dorin feels portability is a low priority. Unlike inpatient surgery settings, patients typically move only very short distances. "We're talking about a matter of feet," he says. He believes that the time it takes to disconnect and reconnect a patient from the OR monitor to the PACU monitor is minimal.

Dr. Schwartz suggests that instead of purchasing monitors that are portable, managers should just buy monitors that are compatible with one another. This way, even if you do disconnect your patients for transfer from the OR to PACU, you can still leave the monitor cables attached to the patient leads. Then it is a very simple matter to reconnect the patient to a monitor.

Integrated or not?
Another consideration may be whether to buy an integrated or non-integrated monitor.

Most of our experts recommend the former course. Dr. Brockwell and Dr. Friedberg point out that integrated monitors require less space, have only one warranty, service agreement and sales rep, provide all the data on one screen, and only sound one alarm at a time. Although it's true that integrated monitors increase your dependence on just one device, most companies will provide replacement monitors within 24 hours.

Two more tips:
- In some cases, refurbished monitors may be a sound option. Dr. Friedberg recommends insisting on a warranty of at least six months, and recommends testing the model you are considering prior to making the purchase.
- Where practical, always choose monitors that can be upgraded, say both Dr. Kwon and Dr. Dorin. This way, if you add a new procedure that requires a different monitoring technique, you won't have to buy a new monitor.

Click here for A Brief Guide to Monitors