Medicine / Anesthesiology
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Awake during surgery II.

May 24, 2008

Michael Liddy, MD



Since the release of the psychological thriller, "Awake" released last year thrust Anesthesia awareness further into public view, many experts, anesthesia providers, and patients are asking the question, "What can be done to prevent awareness?" In fact this question has prompted heated debate in many academic institutions, anesthesia provider forums, and operating rooms many years prior to the realization by the general public that it is possible for a patient to be awake during surgery, but still unable to let anyone know.

So what can be done to ensure that I won't feel anything during my surgery? First some knowledge of how anesthesia works to enable a smooth, comfortable surgery is needed. There are three parts to getting you off to sleep comfortably. The first is often inducing amnesia, frequently done with a medication called Versed, or Midazolam. This step prevents you from remembering the surgery and in some cases the events in the minutes before hand. The second is to ensure adequate pain control prior to any manipulation of the body. This is frequently done with an opioid medication, or a derivative of morphine. Lastly the anesthetic is administered and may be an inhaled gas or a medication injected intravenously, of which there are many different types of both. The choice depends mostly on the medical condition of the patient and condition at the time of surgery. There is a fourth component of the 'cocktail' that is given to induce guaranteed motionlessness during the surgery to prevent accidental damage in case of some sudden inadvertent movement by the patient. This is called a paralytic agent and induces a temporary paralysis during the procedure. When the paralytic is present with inadequate levels of sedation, and pain medication, awareness can occur, and unfortunately the patient is powerless to show that this is the case due to their paralysis.

One might ask why large doses of the sedatives cannot be given to ensure un-awareness? Well, as everyone knows, medications have side effects. These medications can be harmful both during surgery effecting blood pressure, breathing, and heart rate, and after surgery, causing dizziness, nausea, vomiting, etc. Thus, a delicate balance must be achieved to get the best of all possible worlds, adequate sedation, lack of complications, and a comfortable period following surgery, ie the art of medicine.

Patients are vigorously monitored by the anesthesia provider during surgery. Blood pressure, heart rate, breathing, oxygenation, and EKG electrodes are all standard. But is there a monitor that can measure 'awareness'? It happens that there is such a monitor and its use is gaining in popularity in operating rooms. The BIS monitor, or "Bispectral Index," is thought to be a qualitative measure of awareness. It is similar to the EKG placed on the chest to check the electrical rhythm of the heart. It works in the same fashion and 4 electrodes are taped to the forehead, recording electrical activity of the brain. This electrical activity is measured and converted to a number or measure of consciousness. In general, a level of 60 would indicate when a patient could not experience awareness, and a level of 100 would be someone awake and reading this article. Its proponents claim that the BIS monitor reduces anesthesia awareness, as well as excessive anesthetic use during cases. However, studies are indicating this not to be the case and that traditional methods of measuring awareness, or more correctly, depth of anesthesia, are equally good and possibly less expensive, and at the same time do not significantly alter the amount of anesthetic given. (1) So it is probably a helpful tool in select instances to monitor awareness, but so far it seems that the search will continue for an 'awareness' monitor.

The bottom line is that anesthesia awareness is a rare occurrence, and is also a known complication of anesthesia delivery. A greater understanding by the public is needed and they should understand that awareness is a risk that must be taken when undergoing a surgical procedure, which is similar to the risk of surgery causing bleeding, infection, or other common complications. Anesthesia providers take great care in providing the most comfortable experience possible during what are often very traumatic, painful times of patients' lives.

References:

1. NEJM, Mar 13, 2008 Anesthesia Awareness and the Bispectral Index.
2. Miller's Anesthesia 6th Edition. Ronald D. Miller M.D
3. Awake The movie!.
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