Monitors of cerebral oxygenation.
None of the monitors of cerebral oxygenation discussed above has proven to be effective enough to have become a standard of care in any given area of medical treatment. As described above, each has specific and well-defined shortcomings that prevent its widespread use. These shortcomings may not be so much a failure of technology as an acknowledgement of the complexity of our goal: a monitor that can divide the entire brain into small, focal, and discrete areas and accurately measure the oxygen tension in each one. Because we are asking for the functional equivalent of 30 or 40 simultaneous PbtO2 probes, it is small wonder that we are not yet satisfied. Of the three monitors discussed here, the greatest potential may lie with the transcranial cerebral oximetry. The cerebral oximeter has the biggest potential for improvement because it holds the most potential for technical advancement. Although, for instance, jugular venous bulb oximetric catheters may become somewhat more accurate, the biggest drawbacks in that monitor's usefulness lie in human anatomy and intracerebral blood mixing, not catheter accuracy. PbtO2 probes, also, have little room for improvement. Although every technology can be refined, the PbtO2 probes are already accurate. The fact that they are an invasive monitor, and a regional one at that, will relegate them to a limited number of cases. Cerebral oximeters hold more potential. Their greatest limitations lie in technical aspects that can be, and hopefully will be, improved upon in terms of computer technology as well as algorithm accuracy. The fact that cerebral oximeters can be used on any patient, at any time, on almost any case, makes it, potentially, truly an ideal monitor for anesthesiologists and intensivists alike. There is no certainty that any of these limitations will be surmounted, at least to the degree necessary to achieve desired accuracy. But there is much to anticipate.
Smythe
Paul R
PR
Department of Anesthesiology, University of Michigan Medical Center, 1500 E. Medical Center Drive, 1H247-UH, Box 0048, Ann Arbor, MI 48109, USA. psmythe@umich.edu
Samra
Satwant K
SK
D018685:Anesthetics, Inhalation / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007601:Jugular Veins; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods; D010092:Oximetry / Q000295:instrumentation / Q000379:methods; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects; D019265:Spectroscopy, Near-Infrared
D018685:Anesthetics, Inhalation; D006454:Hemoglobins; D010100:Oxygen