Technical and scientific exhibits at the 1993 American Society of Anesthesiologists’ Annual Meeting in Washington, D.C., October 9-13, had less emphasis on traditional monitoring equipment than in recent years and reflected some moderate development of newer aspects of patient safety.
Beyond the standard, expected displays of multiple possible mix-and-match configurations of what are now traditional electronic monitors for various physiologic and anesthetic parameters, airway equipment, devices, and techniques appeared to be the prominent type of display.
Easy Blind Intubation?
An extremely wide variety of laryngoscope types and styles as well as many different intubation aids were displayed and touted by manufacturers. All were expansions, extensions, or variations of described technology. One of the Scientific Exhibits, however, displayed a capnographically assisted stylette intended to facilitate blind intubation during spontaneous ventilation. Three separate gas sample aspiration channels (inferior, right, and left) are contained in a flexible, controllable stylette. Computer processing of the signal generates three waveforms on a display screen. When the three are concurrent, the tip of the stylette is pointed directly into the stream of exhaled gas and, presumably, towards the lumen of the trachea. When the three waveforms diverge, the tip of the stylette is not aligned with the stream of exhaled gas. The exhibitors claim that hand-eye coordination of manipulation of the stylette based on the display is easily learned and blind intubation of the trachea in patients with extremely difficult airways is greatly facilitated. The electronics are custom designed and could not be added to an existing capnograph. The project is still in development and no commercial product exists.
Various Tubes
Endotracheal tubes especially designed and manufactured to be used during laser laryngeal surgery were featured in seven commercial displays among the Technical Exhibits. Neural monitoring of one type or another was the submit of nine product displays. A product with an ECG electrode as part of an endotracheal tube (allowing another type of lead ‘view’ of the heart) was shown for the first tune.
All of these product displays and their attendant exhibitors mentioned the proposed safety advantages of their products to at least some degree.
A wide variety (at least ten) of ‘information systems” were shown in the technical exhibits. Virtually all of the newer ones involve processing, recording, and display of data that involves manual input into a computer by the anesthesiologist before, during, and after an anesthetic. Refinements of existing brands and one new model of automated anesthesia records were also displayed, without any obvious major technologic breakthroughs in evidence.
IV Safety
One new product was an IV injection site monitor intended to detect subcutaneous extravasation of fluid and medications intended for intravenous infusion but not getting into the vein. This device is essentially a subcutaneous temperature monitor with a passive receiving device outside the body. In development are a display and alarm that would signal an errant IV injection/infusion and, eventually, the company envisions the same technology evolving into a new generation of temperature monitor measuring intrabody values accurately.
At least eight technical exhibits dealt with needle and injection safety. These, appropriately, were as much oriented to anesthesiologist safety (protection from accidental needle punctures) as to that of the patient. Holders, brackets, guides, covers, and ports were all involved in some way in the widely divergent family of devices displayed.
Safety of tourniquets used for vascular occlusion during extremity surgery was the subject of a Scientific Display that demonstrated the use of somatosensory evoked potentials to determine a safe occlusion pressure. Investigators noted that tourniquets are often inflated to extremely high pressures arbitrarily to guarantee no leakage of blood into a wound, but at the risk of ischemic damage, particularly to nerve tissue. Therefore, advocating the common theory that the lowest possible pressure would be the safest, the team used SSEP to verify that tourniquets could be set just a small pressure above occlusion pressure and preserve nerve integrity and minimize risk of complications while still providing a dry operative field.
Another Scientific Exhibit showed the endotracheal tube with the self-inflating bulb added to it that is constructed in such a manner that it demonstrates by its inflation characteristics whether the tube is in the trachea or esophagus. Multiple questions about its use were answered in the display. This device is in development and not now commercially available.
One Exhibit had an excellent display with models, including an artificial lung, illustrating appropriate procedures to follow in the ‘can’t intubate, can’t ventilate’ airway crisis. This work ties in closely with the ASA practice parameter on the difficult airway.
Several Exhibits involved computer-driven educational models and programs. Teaching tools for all levels of practitioners were seen, including interactive tutorial programs. Literature searching programs and data bases for various purposes were also featured.
In all, again this year, there were no profound breakthroughs equivalent to “the next pulse oximeter” displayed at the meeting . There were, however, several innovative and creative products and ideas shown that eventually may have incremental positive effects on anesthesia patient safety.
Dr. Eichhorn, Professor and Chairman of Anesthesiology at the University of Mississippi, is an APSF Director and Editor of the Newsletter.