There's nothing inherently therapeutic - or exciting, for that matter - about patient monitoring. Today's smaller, more reliable and more affordable monitors simply provide information that confirms or alters your course of care. Their greatest utility is providing an early warning of potential adverse events. Here's an update.

Must-see IV
The American Association of Anesthesiologists' "Standards for Basic Anesthetic Monitoring" determined that most anesthetic-associated major morbidities or deaths were preventable. Better intra-operative monitoring, it said, provide clinicians with early warnings and encourage precautions that might prevent adverse events. Based on this standard, the safe administration of sedative and anesthetic medications requires the continual evaluation of a patient's oxygenation, ventilation, circulation and temperature. The ASA defines continual as "repeatedly, regularly and frequently in steady, rapid succession." Conformity with the standard requires the following:

• continuous electrocardiogram monitoring;
• a determination and evaluation of heart rate and blood pressure at least every 5 minutes;
• an evaluation of at least one of these: pulse palpation, auscultation of heart sounds, intra-arterial pressure tracing, ultrasound peripheral pulse, pulse plethysmography or oximetry;
• a quantitative measure of oxygenation, such as pulse oximetry (monitors must provide a variable pitch tone and low-threshold alarm to alert anesthetists to changes in the patient's condition)
• a measurement of CO2 in the expired gases, which confirms correct insertion of the endotracheal tube or laryngeal mask airway. Capnography, which monitors continually exhaled CO2 throughout the procedure when the patient is intubated endotracheally or has a laryngeal mask, is a good adjunct to the clinical exam to monitor ventilation during regional or monitored anesthesia care;
• monitoring of oxygen concentration in the inspired gases whenever a general anesthetic is administered using an anesthesia machine. The oxygen analyzer must have a low inspired oxygen concentration alarm;
• the breathing circuit must contain a monitor capable of producing an audible alarm if a leak or disconnect occurs whenever ventilation is supported mechanically; and
• temperature monitoring whenever the intended procedure places the patient at risk for clinically significant changes in body temperature.

The ASA says that when circumstances make the use of basic monitoring impractical or when specific monitors fail to detect untoward clinical events in specific circumstances, the anesthetist may forgo the use of the required monitor. Whenever an anesthetist elects to waive the use of a standard monitor, a notation in the anesthesia record should state the reason for the exception to the standard.

New and improved
Although many anesthetists still regard EKG and blood pressure monitoring as their primary physiologic monitors, pulse oximetry and capnography are proving to be the most useful monitors for providing an early warning of potentially preventable untoward events. Peter Safar, MD, a pioneer in cardio-pulmonary resuscitation and intensive care, once commented that the reason he chose the EKG as his primary physiologic monitor in the early 1960s was because it was the only instrument practical for use at the bedside in a pre-transistor technological world. He went on to explain that had pulse oximetry been available in 1960, he would have chosen it over EKG monitoring because of the utility of measuring oxygen saturation and pulse rate.

His message serves as a reminder that newer monitoring modalities represent more than an additional parameter to conventional monitors. Clinicians should consider that the latest options might be more useful as physiologic monitors than older ones and that that newer technologies might eventually replace standard monitors in use today. When first developed, devices used to objectively measure pulse, blood pressure, and temperature and to ascultate the heart were castigated by some. Where would we be today without those most basic of devices?

The most significant of new modalities - and a change from the original 1986 monitoring standard - is the required use of end-tidal CO2 monitoring and capnography (the measurement of carbon dioxide concentrations in respiratory gases) to detect the misplacement of tracheal tubes and laryngeal mask airways as well as the detection of airway obstruction, hypoventilation and hyperventilation.

Capnography, when used during intravenous sedation, gives an objective measure of ventilation that can serve as an early indicator of airway obstruction or apnea in spontaneously breathing patients with greater precision than observation. We put a great emphasis on the clinical exam to measure physiologic functions in the OR and recovery area, but visual clues can sometimes mislead.

The patient with an airway obstruction may still show movement of the chest wall, without moving air. Conversely, the heavily sedated patient may show no signs of respiring while quietly breathing. Even pulse oximeter monitors provide a potentially late alarm when breathing patterns go awry by sounding only when oxygen levels drop.

Capnography brings an element of safety to sedation that anesthesia providers don't yet fully appreciate. It provides real-time, useful data. These monitors relay breath-to-breath oxygenation levels, let clinicians watch the patient's ventilation directly and can immediately see obstructions in the patient's breathing pattern so that they may intervene before the patient becomes hypoxic. This monitoring ability is especially important during procedures where draping and positioning limits the anesthetist's visual access to the patient for observing clinical signs of airway patency and ventilation such as nasal flaring, use of accessory muscles of respiration and chest wall excursions.

The monitors are well used, but they're not yet a standardized level of care. Improvements in technology and decreasing cost of these devices - as low as $1,000 for some models - make them practical for use on all anesthetized patients.

Whenever possible, outfit your ORs with standardized monitors. Staff working with identical devices will quickly learn the features, know which button does what and zip through the user menus with ease. Like aviation safety models, breed familiarization through standardization. User-friendly displays are also essential. Look for screens with large, easy-to-read numbers, simple-to-understand touchscreen controls and easy-to-toggle-between menus.

Avoiding the serious
The incorporation of advances in monitoring technology into clinical practice, though still resisted by some clinicians, continues to improve an anesthetist's ability to recognize early changes in a patient's clinical condition. This early detection lets anesthesia providers catch minor issues before they escalate to a much more serious and sometime irreversible concern.