In combination, low blood pressure, low inhalation agent concentration and increased depth of anesthesia are associated with worse outcome
Higher concentrations of an anesthetic are associated with deeper levels of hypnosis. There is some evidence to show that longer periods of deep hypnosis are associated with poor outcome. What about outcome after the use of a lower concentration of an anesthetic producing deeper levels of hypnosis in the face of lower blood pressure? In the article “Hospital Stay and Mortality Are Increased in Patients Having a ‘Triple Low’ of Low Blood Pressure, Low Bispectral Index, and Low Minimum Alveolar Concentration of Volatile Anesthesia” published this month in Anesthesiology, Dr. Daniel I Sessler, (Michael Cudahy Professor and Chair, Department of Outcomes Research, Cleveland Clinic, Cleveland, Ohio) and coauthors used their institution’s hospital documentation system to evaluate the association between low mean arterial pressure (< 75 mm Hg), low bispectral index (< 45) and low anesthetic concentration (MAC < 0.8) with length of hospital stay and 30-day mortality.
Almost 25,000 patients who underwent noncardiac surgery between January 6, 2005, and December 31, 2009, at the Cleveland Clinic were studied. Bispectral index monitoring was used for all patients, all patients had single volatile agent, and all were at least 16 years old. Those with triple low values stayed longer in the hospital. Thirty-day mortality was also four times higher for those patients with low values for all three variables. In particular, the fraction of patients whose hospital stay was longer than national averages for a particular procedure was seen after cumulative triple low value duration was greater than 30 min. Also, mortality increased when cumulative triple low value duration was 31–45 min and when it was greater than 1 h. The effect on mortality after triple low values was much more apparent than after length of hospital stay.
The study did not include patients who received an intravenous as opposed to an inhalation anesthetic. In addition, the study was retrospective and did not show a cause and effect relationship. Indeed, intraoperative care should not necessarily be changed based on the study’s findings. Surprisingly, the limits they used were within the range many of us would tolerate as part of a routine anesthetic.
In the accompanying editorial “‘Triple Low’: Murderer, Mediator, or Mirror” by Drs. Sachin Kheterpal (Center for Perioperative Outcomes Research, and Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan) and Michael Avidan (Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri), the authors note that
“…this impressive study demonstrates that the era of anesthesiology insularism is coming to a close. What we observe, and possibly what we do, during our brief intraoperative relationship with the patient probably is relevant to long-term patient outcomes. Future research efforts must be dedicated to reproducing or refuting the current findings and exploring how perioperative management could contribute to improved patient trajectories. In doing so, the field of anesthesiology will demonstrate its value to patients long after they have left the operating room.”