I'm currently revising for my anaesthetics exams. The things I'm meant to know include:
* The physics and mechanical principles of all the equipment I use, from the ventilator to the pulse oximiter - so that I can identify when and how it might fail and how to respond
* The pharmacokinetics, pharmacodynamics, and mechanism of all the drugs I might use - so I can understand their effects, side-effects, and interactions
* The physiology and function of the human body, including the respiratory, circulatory, neurological, renal, gastrointestinal, musculoskeletal, and immune systems - so I can understand how anaesthesia effects these systems, and how diseases and disorders of the systems will interact with the anaesthetic and how problems can be identified and treated
* The anatomy of the body, with particular focus on the head and neck anatomy to aide in intubation and airway procedures, and neuro-anatomy to aide in regional anaesthetic techniques
* The anatomical, phsiological, and pharmacological consequences of pregnancy, childhood, old-age, and a huge variety of acute and chronic diseases - so I can understand and adapt anaesthetics to these conditions
You're playing a fine balance between keeping the animal under, and killing it. You have to continually observe and balance the degree of anaesthesia which you can test with pain reflexes and core reflexes, and adjust the dosage accordingly. Too much and you depress the core functions to the point breathing stops. Too little and the animal retains consciousness along with pain reflexes. With larger animals you can use similar equipment to what you would use with humans. Small ones require direct physical observation.
There's a simple dosage rule: n ml anaesthetic per gram bodyweight. So you would weigh the mouse, calculate the dose and then inject it. Sounds easy enough.
Not so. It also depends upon the percentage of fat tissue. If the mouse is fat, the fat tissue will absorb the anaesthetic and then slowly release it. This changes the dynamics of how fast the anaesthetic takes effect, and how deep and how long lasting the anaesthesia will be. Skinny mice would go under almost immediately. Fat mice might take 10 minutes. But if you topped up the dose, you would risk the dosage reaching fatal levels a few minutes down the line as the fat tissue released its stored anaesthetic. You would learn to adapt the formula by experience, but this is just one factor to consider.
Now imagine how difficult this is with obese human patients. Or anorexic patients. Or sick patients. Patients on various drugs. Or patients with different metabolic rates. There are dozens of factors, making each case unique. Anaesthesiologists have a huge responsibility, and taking great care and skill to keep their patients alive. We think of this as routine, and it is, but that doesn't make it simple or easy to do. This stuff looks simple on paper. Doing it in practice is far, far more difficult and demanding.
Living creatures are not industrial processes. Each one is unique and will behave differently. So while you can draw some generalisations, you can't safely put a machine in ultimate control, or even in a position to provide unreliable feedback. Even industrial processes aren't usually automated in their entirety and usually have 24/7 oversight; "simple" PID loops can misbehave, and this is far more complex with many more variables. The consequences here are death at one extreme and extreme suffering at the other, and so the stakes are too high to delegate it to a machine. This isn't some theoretical problem--a life is literally on the line and machines can not hold responsibility for a life.
Also note that answering the questions of "is the animal conscious", "is the animal in respiratory distress", "is the animal in pain", "are the core reflexes functioning" or "have the core reflexes stopped functioning" all require complex assessment, which a machine can't do. And if any of those are true or false, the complex dynamics make the decision of giving more or less anaesthetic dose a very complex question to answer. If anything goes wrong, it requires intelligent and informed decisions to be made. In some circumstances that includes killing with an overdose for ethical and legal reasons. It would be unethical and cruel to let a machine make decisions of such consequence.
Having another life in your hands is a huge burden. It's both humbling and scary to be given such power and responsibility over another living being, and having done it I'd have to say I find the notion of giving a machine control or even moderate influence over the process grossly irresponsible. Automating every last aspect of our existence is a horrifying concept. Some things need humans in absolute control, and this is one of them. And I say this as someone who eventually became an software engineer for embedded medical diagnostic devices. Think about the ethics of what you are suggesting.
Second, I understand there are very fine details at play. However I disagree with the point that complex assessment is out of a computer's reach, on the contrary, they are especially good at it. I would trust a machine to consider a patients full medical history in accordance with their momentary markers more thoroughly and faster than a human ever could. Not to mention the human factor of being less educated, tired, in a bad mood or simply not available.
Admittedly I know nothing about the protocols in anesthetics, and indeed, it is my preconception there is little more to it than a tight control loop with not much room for wiggle. What do anesthesiologist base their decisions if not data? Perhaps some of the data is not obvious to a machine and we need humans sensors for input, but the thought of people playing god with ad hoc ideas makes me more uneasy than a computer involved. Granted I live in a second world country and capable doctors are few and far between and it must count for some of my bias.