MAC explanation

They'll teach it to you in CRNA school. MAC is more of a guideline since other supplements to anesthesia can increase or decrease your MAC value of inhaled anesthetics.

Can anyone give an example or explain in a way that I can understand the concept and uses of MAC? Keep in mind, I am not in school yet (hopefully soon). I have the definition of Minimum alveolar concentration at 1 atm to prevent stimulus in 50% of the population but how does this translate to every day use of inhalants? Maybe you know of a website or a way that you learned it to understand the whole concept. Thanks in advance.

You are right in the definitiion of MAC. 1 mac is that concentration at which 50% of patients will not move to surgical stimuli, but 1.3 MAC is the MAC 95 in which 95% of patients will not move to surgical stimulation. So basically that's just a little bit above MAC. Also remember on most patients we are using benzos, things like propofol, fentanyl, etc which will lower the MAC value of your inhalation agent. For instance if the MAC of desflurane is 6.6% but you have given fentanyl, propofol and preop versed...you may run the patient at a ET concentration of desflurane at 5% and be perfectly fine. There are many factors that change MAC and increase it or decrease it. You will learn all about it in school as the other poster mentioned, but i hope this helps you just a little bit. Good luck

The nuts and bolts of MAC is that it is a "dose" of inhaled anesthesia. the dose goes down with increased age, other drugs you are using during the anesthetic etc.

The best thing about MAC is that it was easy to measure when the gasses were being studied. Because it is a 50/50 or yes/no answer, the person who was doing the experiment did not have to use a large number of subjects. The patient either moved or he didn't. It was an easy number to establish and then it could be used to compare one drug with another.

MAC level is the concentration of anesthetic present in the alveoli to produce lack of movement to surgical stimuli. The mechanics of MAC is the actual percentage of atmospheric pressure the anesthetic gas is exerting on the alveoli. At sea level 1 atmosphere is equal to 760 millimeters of mercury- If you anesthetise an individual at a MAC of 1, this means the minimum alveoli concentration to produce the anesthesia is 1 percent of the atmospheric pressure (760mmHg). The anesthesia is exerting 7.6 millimeters of murcury of pressure in the lung.

mac is all of these things above, but the simplest way of thinking about it is as a standardized measurement of anesthetic gas level, whether you are using sevo, des, iso, etc, or n2o (these agents all have differnet conc at 1 mac) you can express your anesthetic conc as the MAC value.