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
