Samus cannot die during the fade-in or fade-out from a pause. Because of this, several mechanics are possible if you pause just before she reaches 0hp, whether by taking a hit from an enemy, or some other source of damage like heat.
If you pause frame-perfectly when the fade-in finishes, you can survive an indefinite number of pauses at 0hp. There are restrictions however; Samus cannot pause during certain game events, such as elevator rides, Power Bomb explosions, and Mother Brain's Rainbow Beam. However, during the time Samus is at 0hp, In Game Time will not count up. This was heavily utilized in this TAS, saving about 20 seconds of In Game Time. Theoretically a No Major Glitches TAS could even be made with this exploit that would have an incredibly low In Game Time.
If you have your Reserve Tanks set to manual, you can pause just before you reach 0hp, allowing you to fill just enough from the reserves to survive.
This method is common in categories that require Draygon to carry Samus to the top-right corner of the room, such as 14% xIce. If you pause every time Draygon is about to hit Samus with her tail, you can manually pull a very small amount of health out of your reserves, allowing you to survive much more damage with two e-tanks and a reserve tank than you would with three e-tanks.
If you can get a health drop before the fade-in finishes you can survive. This is fairly common in RBO runs, while waiting for Ridley's drops after having an automatic Reserve Tank activation during his death animation.