Anesthesia awareness, or unintended intra-operative awareness, occurs when patients’ are assumedly subdued to general anesthesia while undergoing surgery. Instead of being sedated and unconscious, the person is cognizant enough to experience excruciating pain and retain some memories of the awakening.
Paralytics are used to immobilize the patient while they are intubated and linked up to life support systems. Therefore they are incapable of communicating with medical staff.
Anesthesia awareness happens when a patient hasn’t been administered with adequate doses of anesthetics or analgesics. Aside from surgery, patients can experience the anomaly while tranquilized in post-anesthesia care units (PACU) or in the intensive-care unit (ICU).
A patient may experience any level of cognizance. The most traumatic case of anesthesia awareness is full consciousness during surgery with pain and explicit recall of intra-operative events. In less severe circumstances, patients may have only a poor recollection of brief post-operative recall of conversations, events, pain, pressure, or difficulty in breathing. The difficulty in breathing is caused by intubation errors or problems with the ventilator, meaning the patient may have been suffocating.
This rare condition occurs about once in every 10,000 operations, according to Time. Monitoring heart rate and blood pressure can alert anesthesiologists to pain in the majority of cases, but these indirect measures don’t always identify the presence of awareness.
Research published in the Proceedings of the National Academy of Sciences, suggests keeping track of how a patient loses consciousness could alleviate some of these unfortunate events. Tracking brain activity patterns, for instance, may lead to better dosing and control of anesthesia.
The science of electroencephalography (EEG), the recording of electrical activity along the scalp with electrodes, has been used for medical research since the 1930s. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain.
Several operating rooms currently utilize an EEG device, charting signals in order to establish a reading of consciousness levels. This technique is intended to ensure that patients are fully under the influence of anesthesia before proceeding. However, the EEG monitors are not properly calibrated to precisely detect signal variables effecting consciousness.
In an effort to refine the technique of properly identifying a range of awareness with EEGs, researchers applied electrodes to test subjects and charted electrical activity as they applied controlled doses of general anesthesia.
Dr. Emery Brown, a co-author of the study and professor of computational neuroscience at MIT, and colleagues studied 10 adults who, over the course of two hours, were given increased doses of the anesthetic propofol. Quantities were incrementally amplified until the subjects lost consciousness. In an equally gradual manner, anesthesia was waned, and scientists were able to chart signal changes from consciousness to unconsciousness, and again from loss to recovery.
According to the lead author, an instructor of anesthesia at Harvard Medical School, Patrick Purdon:
“We have discovered highly structured EEG patterns that indicate when people are sedated during administration of propofol, when they are unconscious, and when they are able to regain consciousness. These findings provide precise, neurophysiologically principled markers that can be used to monitor the state of a patient’s unconsciousness under (propofol) general anesthesia.”
Information gleaned from the study may assist anesthesiologists in administering the drugs more effectively, lessening the incidences of under and overdosing.
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