Imagine stepping into an operating room. You see a patient draped for the operation, the surgical team, the anesthesiologist, an anesthesia machine, a ventilator, one or more infusion pumps, bags with intravenous fluids, and a monitor with a screen full of curves and numbers. But the picture is not static. The people move, the bellows of the ventilator go up and down, the drip chambers of the infusion sets show drops of fluids, and on the monitor the ECG, blood pressure, SpO2, and capnographic patterns run across the screen. You behold this scene that presents an enormous amount of continuously changing data. You also hear the surgeon asking for an instrument, the scrub nurse saying something to the circula-tor, the anesthesiologist conveying to the surgeon information from the patient’s medical record, the ventilator puffing, and a monitor beeping. Depending on your experience, you will know how to interpret what your senses absorb. You can imagine the scene with calm professionals at work at a routine task or one with frantic activity during an emergency punctuated by the urgently sounding alarms.
In this scene, you are the monitor. You absorb an abundance of signals that present data, which in your mind turn into information. You turn this information into knowledge, depending on what you know about the patient, the operation, and the clinical team. This knowledge depends on information about the patient’s history and, ideally, acquaintance with the patient himself. If you were to record all the facts that you can comprehend, you would wind up with a very, very long list. On paper, it would take hours to synthesize, from such a comprehensive list of facts and ever changing trends, the current status of the patient. Such knowledge would enable you to make certain statements about this moment in time and projections into the immediate future.
When you think about monitoring, please remember that the physical diagno-sis – still part of monitoring in anesthesia – and the elaborate electronic monitors present only a minute fraction of the data that you, the clinical monitor, require and absorb in order to understand what is going on with your patient. The elec-tronic monitors supplement in a modest way what the clinician perceives.
Let us now look at the small fraction of information generated by physical examination and by electronic and mechanical monitors.
Assume that the patient undergoes an operation under epidural anesthesia and light sedation. In addition to all the data described above, you will observe that the patient is breathing spontaneously. That means he has a heart beat and a blood pressure sufficient to perfuse his respiratory center. If the patient responds appropriately to a question, we know his brain is adequately oxygenated. Now, that is a lot of information picked up without instruments!
Now assume the patient to be under general anesthesia and paralyzed, and that a ventilator mechanically breathes for him. Without getting a little closer, you cannot know if the patient has a heart beat, a blood pressure, a perfused brain, or enough oxygen to keep the brain out of trouble. Enter focused monitoring . . .
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