The history of anesthesia is a clear lesson in the usefulness of empiricism within the practical and real world of day to day medical practice. These gases and fluids work; and until recently, how they worked was pretty much a mysterious process. What mattered were the obvious effects and end points that these substances produced in living bodies that allowed for huge advances in diagnostic capability, surgery, and treatments.
The general goals of attaining sought after levels of sedation, unconsciousness, immobility, amnesia, and analgesia were the driving forces for choosing and accepting what agents to use. Chasing down the actual mechanisms that produced these sought after for effects lagged far behind the application of these agents in practice.
Anesthetics are potent nervous system suppressors that essentially produce a type of coma more than a deep sleep. There is a general disruption of the normal sequence of nervous activity that disconnects its ability to sense, process, and relate to the surrounding environment. It was assumed that because anesthetic agents are composed of a motley crew of differing chemistries, they all acted in some general nonspecific manner on the nervous system blanketing everything in slumber.
Fascinating research using magnetic resonance imaging and positron- emission tomography techniques are now shedding light on the actual mechanism of action of these agents and are revealing unexpected findings. It appears that instead of the assumed blanketing effect, these anesthetic agents actually have very specific actions at pinpoint regions and, most importantly, specific receptors within the nervous system.
The actual cellular components of the nervous system, especially the neuronal connections and areas around these connections have receptors that are involved in the transmission of action potentials sending stimuli and electrical activity to and fro between nerve cells. These dynamic interactions translate eventually to the macroscopic functions that become cognition, sensory perception, and emergent qualities that together seem to become what we understand as consciousness.
In addition, there was found to be a plethora of differing receptor types depending upon the region of the nervous system in question. This helped explain the discovery that though anesthetics have very similar activity no matter what their make up, some agents seem to produce highlighted actions on say amnesia over immobilization for instance.
These findings open the doors to a panorama of possibilities among which are the potential to develop safer and more specific compounds* as well as shed new light on how the brain in general functions. The ability to develop anesthetic compounds with specific action on pinpoint regions of the nervous system will allow anesthesiologists to separate and concentrate on analgesia or amnesia without producing the other depressive effects of todays' agents that increases the risk to the patient.
Learning about these receptor actions also reinforces other research findings implying that the brain and its associated systems are composed of centers and areas that together function to produce the qualities we interpret as consciousness. This research adds to what general neuroscience research is discovering. The “who” we are- that “I” within us – seems to originate within organic functional interactions and not from an associated extracorporeal phenomena or “soul” in the dualistic sense.
These areas of study are providing mountains of information that will keep scientists, philosophers, or anyone else interested occupied with wrestling over the profound implications for years to come.
*Even though anesthetic protocol is considerably safe, it has reached a plateau with a mortality rate of around .008% and could be improved
Ref: www.sciam.com Lifting the fog around anesthesia. Orser,BA