You can absolutely find out if someone is high at that moment by doing a blood test
Good luck with that, especially without anything being taped.
Would you fire a doctor that 'appeared' drunk to someone but passed a breathalyzer?
What is passing a breathalyzer? If it read 0.00 then no, I would not fire. If anything other than 0.00 time to pack up. That mistake can cost millions of dollars. Someone wanting to drink or get high is not worth millions to an employer or insurance company. Pay out of your own damn pocket if you want to be so negligent.
You don't do tests that show if doctors have consumed alcohol in the past 30 days or longer
no shit. Alcohol metabolizes differently and has different effects. It's also not illegal. Juries rule against alcoholic doctors quite often. They do so against pot smoking doctors as well, as they should for both.
you can get an accurate reading of how much THC is in the blood at that very second.
At the very second the test is taken, not days before. Everyone metabolizes differently. There is a lower burden to prove in civil than criminal. Clear evidence of an injury possibly caused by negligence plus a physician that had a reasonable likelihood to have been under the influence at the time of the botched procedure easily meets that burden.
Urine tests, and worse, hair tests, are way too broad and prove nothing.
They prove that a medical professional was a user of illegal drugs during the time period when he may have been committing malpractice.
Don't fucking do drugs if you're a medical care provider. It's not hard not to smoke, shoot, or snort things, especially when they are illegal. There is NO excuse to use illegal drugs as a medical care provider while lives are in your hands. If you want to consume them then don't practice. Medical care professionals are held to a higher standard, and they should be.
A client suing a physician that tests positive for any drug use anywhere around the time of the botched procedure will receive settlement money or win a judgement 999 times out of 1,000.