Science / Medicine : Constant Monitoring Required During Surgery

The Standards for Basic Intraoperative Monitoring, recommended by the influential American Society of Anesthesiologists, state that an anesthesiologist, who is an M.D., or a nurse anesthetist, who has special training in anesthesia delivery, will be present during the conduct of all anesthesias.

This person is to evaluate the patient’s oxygenation, ventilation, circulation and temperature either at frequent and regular intervals or else continuously.

In some instances, the standards either encourage or require specific pieces of monitoring equipment. For example, all patients are required to have an electrocardiogram displayed throughout anesthesia--to ensure adequate circulation is taking place.

Every patient must also have arterial blood pressure and heart rate determinations every five minutes. Most electrocardiograms display a patient’s heart rate, but it can also be measured by listening with a stethoscope.


In no case are specific vital sign parameters or physiologic limits set. Since most of these parameters vary from person to person and can be affected markedly by diseases and age, detailing of specific limits would have resulted in a textbook of anesthesia rather than the one-page document that the standards form.

The accidental insertion of the endotracheal tube into the esophagus (which leads to the stomach) rather than the trachea (which leads to the lungs) is probably the best example of the need for monitoring standards. Such a mistake would deprive the patient of oxygen.

The standards require that when an endotracheal tube is inserted, its correct position in the trachea and the adequacy of ventilation must be verified at the minimum by clinical signs, such as observing chest movement and listening to breath sounds in the lungs.

In addition, the standards suggest the use of a machine to analyze carbon dioxide in the exhaled breath in order to provide a quantitative, reliable indicator of proper tube placement.

In the future, this specific piece of equipment may be mandated, as the standards undergo further revision, Dr. John H. Eichhorn of Beth Israel Hospital and Harvard Medical School noted.

“This is the transition period,” said Dr. James Philip of the Brigham and Women’s Hospital in Boston and Harvard Medical School. “Very soon, all anesthesiologists will be monitoring carbon dioxide, and our patients will all benefit from it.”