When the vital sign measurement interval to determine outcome after surgery was increased to 10 minutes, specificity and sensitivity of the score improved. (Image source: Thinkstock)

When the vital sign measurement interval to determine outcome after surgery was increased to 10 minutes, specificity and sensitivity of the score improved. (Image source: Thinkstock)

In 1973, Dr. Virginia Apgar, an anesthesiologist, introduced an eponymous five-item score to determine the ability of a neonate to adjust to extrauterine life. The score is based on heart rate, respiratory effort, muscle tone, reflex irritability, and color, important signs for the anesthesiologist. More recently our surgical colleagues have devised a “surgical Apgar score” to identify patients at risk for developing adverse events after surgery. The surgical Apgar score is based on lowest heart rate, lowest mean arterial blood pressure, and estimated blood loss between skin incision and closure. The score was originally developed with the use of hand-charted anesthesia records and five-minute recordings of heart rate and blood pressure. Dr. Joseph A. Hyder, now at the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA and colleagues from the departments of Anesthesiology, Division of Critical Care Medicine, and Surgery, Mayo Clinic, Rochester, MN determined whether the score could more accurately predict the risk of death or major complication(s) within 30 days of surgery as blood pressure and heart rate interval changed. Their findings are published in this month’s edition of Anesthesia & Analgesia in the article “How to Improve the Performance of Intraoperative Risk Models: An Example with Vital Signs Using the Surgical Apgar Score.”

The study data comes from Mayo Clinic, Rochester, MN. Intraoperative data came from their anesthesia information system. The outcome data were taken from a quality improvement database at their institution. The study used 3,000 patients who underwent general or vascular surgery between 2006 and 2010. Of that group, a total of about 65% underwent major surgery, 9% experienced a major complication or death within 30 days of surgery, and 1% died within 30 days of surgery. As the sampling interval for vital signs increased, the surgical score changed and allowed for better discrimination and improved reclassification of risk. Stated another way, if the sampling interval was increased to 10 min, outcome was changed for about 1 in 20 patients. The authors also found that lowest mean arterial pressure did not show a statistically significant influence on outcome.

The inability of lowest mean arterial pressure to determine outcome may be related to the fact that in this study, the arterial blood pressure was drawn from an automated system, whereas in the original study, the blood pressure measurement was taken from hand-written anesthesia records. Would triage of patients be improved if real-time measures were employed? In this study, the specificity of the score increased without a change in sensitivity.

Areas of future study include determining if the findings are reproducible at other institutions, and are generalizable for patients undergoing other procedures or at the extremes of age.