Volume 6, No. 4 • Winter 1991

ASA Exhibits Feature Safety Technology, Ideas

John H. Eichhorn, M.D.

Technology and concepts intended to promote anesthesia patient safety were widely shown in the technical and scientific exhibits at the October, 1991, Annual Meeting of the American Society of Anesthesiologists.

For the fourth straight year, there were no fundamental technologic breakthroughs shown. Several variations on existing themes and modified/improved technical aspects of various pieces of equipment were exhibited. Permutations and combinations of a diverse array of monitors were prominently featured. Essentially any conceivable configuration that could be desired by an anesthesia provider could be found. Also, ECG ST segment analysis with related analysis and interpretation algorithms seemed to be widely available in routine OR ECG monitors.

One new feature in a monitor is contained in a new spirometer that, in addition to the usual features (including capnography and agent analysis), displays a continuous flow-volume or pressure-volume loop on the screen. It is advertised as an aid in the care of patients with abnormal ventilation patterns.

A new noninvasive real-time waveform blood pressure monitor was shown. It uses continuous radial artery oscillotonometry with a sensor over the wrist that generate an electrical signal proportional to blood pressure. The sensor is held against the artery by a pneumatic bladder that inflates and deflates automatically to achieve the optimum arterial signal.

Intra-arterial blood gas measurements continue to be featured with each new variation in the sensor technology toured as finally solving the problem of dampened signals from arterial wall distortion and clot, thrombin, and protein deposition on the sensor.

Airways Big

Management of the difficult airway was a popular topic in the exhibits. Two new products are intended to facilitate difficult intubations. One plastic intubation “guide” for blind orotracheal intubation slides through the mouth down to the superior aspect of the Larynx. Its shape is specific to &de the special introducer stylet that comes with the kit directly into the trachea so that the endotracheal tube can then be pushed off the introducer into the trachea. The introducer stylet has distal aspiration holes and a proximal syringe, the combination of which is reportedly intended to facilitate identification of correct tracheal placement or accidental incorrect esophageal placement.

The other device intended for difficult airways is designed for blind oro or nasotracheal intubation, although it can also be fitted with a laryngeal mirror to facilitate direct visualization of the larynx. This mechanical stylet has a port for the connection of an ear-piece stethoscope to amplify breath sounds from the advancing stylet tip and make location of the trachea easier. The stylet is connected to a handle with an adjusting lever that flexes and extends the tip of the stylet so, guided by the loudness of the breath sounds, it can be blindly directed into the trachea. In essence, this device is intended to accomplish the same goal as a fiberoptic intubating laryngoscope bid without the fiberoptics (and, thus, at a small fraction of the cost).

“Safe ‘Scope”

Another interesting laryngoscopy product is intended for use with conventional laryngoscope blades. Functioning in much the same manner as a condom, plastic disposable laryngoscope blade sheaths or sleeves cover the blade during use so that cross contamination of oral secretions between patients can be avoided while simultaneously reducing the need for cumbersome blade cleaning and sterilization after each use. The manufacturer states that the fight from the end of the blade is only slightly diminished and this does not impair intubation. The concept of “safe ‘scope” may be aesthetically attractive to patients, but it remains to be seen whether anesthesia providers purchase these protective sleeves for laryngoscope blades.

Pulse oximeters, of course, were shown in many types, styles, shapes, sizes, and colors. A new oximeter was presented as being capable of noninvasive brain oximetry. It is intended to measure intracerebral oxygenation and the product literature correctly states that the large majority of blood in the brain is venous so a saturation reading of 73 percent is normal. While noting that, “ideally, the monitoring system should measure the organ directly” (the sensor placed directly on the brain during craniotomy), it is intended also for external placement and use in a wide variety of settings in which patients may be at risk for cerebral hypoxemia. Again, the potential value of this monitor will be seen as it is tested more extensively in actual clinical situations.

The scientific exhibits contained several additional presentations with safety implications. The phenomenon of latex-allergic patients was noted. Apparently, certain patients with chronic exposure to latex catheters and gloves (e.g. cases of neurologic dysfuction) develop potent antibody responses and may exhibit anaphylaxis in the OR when exposed to latex goods. Strategies to avoid and treat this syndrome were suggested. Safe sedation of children for MRI scanning was featured in an exhibit. Another exhibit involved a questionnaire about anesthesia machine infection control policies (cleaning of machines between patients) and beliefs (whether machines can be the source of nosocomial infections). The response to this questionnaire undoubtedly will form the basis for a subsequent presentation on this topic. Finally, the Federal Food and Drug Administration had an exhibit on the details of the Safe Medical Devices Act of 1990 and the device user facility reporting requirements which mandate filing a report if a medical device is involved in causing a death or serious illness/ injury (see APSF Newsletter, Summer, 199 1).

In all, the ASA exhibits at this annual meeting reflected some maturation of the patient safety “movement” in anesthesiology. Emphasis appeared to be on specific applications and “fine-tuning” rather than block buster-type dramatic advances, which may again be on the drawing boards for subsequent years’ exhibits.

Dr. Eichhom, Professor and Chairman of Anesthesiology at the University of Mississippi, is Editor of the APSF Newsletter.