What are the risks of smoking meths before surgery?

That is a very complicated question to answer, but in short consider this; there are thousands if not millions of drugs working together in your body to create you. The drugs we use in modern medicine have at least some history of being relatively safe to the human body. The problem is that in surgery they will often give you anesthetics, pain killers, antibiotics, or any other number of drugs deemed necessary for this particular surgery. Also factor in that there could be complications while under the knife which could merit other drugs to try and assist your body's capabilities to handle the surgery. What I'm getting at is that all of these drugs interact with each other, and to try and answer your question without addressing many of these potential combinations would lead to an inaccurate answer.

But if you want a guess; Meth gets your heart going, so I would be worried about it causing heart, liver, or kidney damage/failure. If you asked "Should I smoke meths before surgery?" my answer would probably be no.

Other than that I would just say "Talk to your doctor about smoking meth before surgery, meth has been proven to cause side effects including but not limited to anorexia, hyperactivity, getting high as hell, dilated pupils, flushing, restlessness, dry mouth, headache, tachycardia, bradycardia, tachypnea, hypertension, hypotension, hyperthermia, diaphoresis, diarrhea, constipation, blurred vision, dizziness, twitching, insomnia, numbness,palpitations, arrhythmias, tremors, dry and/or itchy skin, acne, pallor, and with chronic and/or high doses, convulsions, heart attack, stroke, and death. Ask your doctor if smoking meth is right for you."