Good question and i hope i can clear this up for everybody
While yes, nicotine does constrict blood vessels, which is why it is good for treating bruises, when applied externally to prevent them from becoming more swollen and painful, by itself it is not enough to result in the loss of the guy's leg.
For the amputation to happen, there has to be gangrene (tissue necrosis), which is when dead tissue turns black and begins to poison the neghboring cells and tissues, which will then die and continue the process.
In minor cases, excision, and in more advanced cases amputation, are the only ways to stop the spread of gangrene once it has set in.
The most common cause is unmanaged diabetes, which is the number one reason for foot and leg amputations in the US. When untreated, high blood sugar thickens the blood, leading to poor circulation, but also breaks apart and weakens blood vessels, causing them to collapse, making the patient's legs brown below the knee and deep purple at the feet.
Overconsumption of alcohol over long periods (aka alcohlism) can have a similar effect in some people, or multiply the effect for diabetics.
Another common cause of gangrene is frostbite, since it too creates an impermeable mass of dead tissue which white blood cells cannot enter. Untreated snakebite causes the same thing, as do bites of some spiders.
Smoking does contribute to amputations and prolongs the healing process after surgery, but blaming nicotine-related loss of circulation for that leaves out other factors, such as carbon monoxide, which also starves tissues of oxygen, since it takes the place of oxygen in the blood, because blood cells can't tell the two apart.
Perhaps the guy had other pre-existing conditions, such as diabetes, or had a bad fracture that wouldn't heal, and got worse. A neglected blood clot could also have done that. If he were a woman, combining cigarettes with The Pill or other hormonal birth control would've likely caused that clot.
Or he may have in addition to all other factors had astronomically high cholesterol, although, that would be unlikely to settle in the leg, and more likely cause buildup in the head, neck and heart areas.
Bandaging the leg too hard or not moving enough would be a more realistic cause anyway.
Bottom line would be that while nicotine does stress the vascular system, raising blood pressure (by constricting blood vessels) and speeding up the heart, if the vascular system itself is healthy it is able to withstand the daily abuse just fine. But if blood vessels are hardened, capilaries especially, you will have a pretty high risk of stroke, regardless of the fact that other cigarette-related toxins are no longer there.
If you are still worried about poor circulation, just execise a bit more and take a break to stretch and move every 45 minutes of office work. Simply walking around is all it takes to compensate for the effects of nicotine, since our muscles are our 2nd heart
-[Arsenic]
