May I ask why across the wrist? The radial artery which runs along the thumb side of the wrist is about 2-3 millimetres under the skin so can be easily severed. When the artery is severed it will lead to significant blood loss very quickly you could lose consciousness within minutes and death can be anywhere between 10-15 minutes but there is a various amount of factors to consider such as your blood pressure, health, age ect