I have a scene where a humanoid monster tries to swallow another being alive, only for them to die when the smaller being rapidly increases in size through shape-shifting and tears its way out of the larger one like a xenomorph chestburster. My original plan was that this action would end up killing the larger character as part of the finale of an action scene, in keeping with some thematic motifs of gluttony and hubris the larger monstrous humanoid has.

However, it almost seems like even if such an action was lethal, it wouldn't be immediately lethal, and the larger character would still have some time to move and fight back before they died of shock, potentially killing the other character in the process (which is not what I am aiming for). Given this, I am trying to figure out how fast it would take for someone to die from such a traumatic injury, assuming that the monstrous humanoid has an anatomy roughly analogous to any other vertebrate and doesn't have a plot-relevant "instant-kill vein" in its digestive tract, and how I could potentially speed this up if possible to avoid having the larger character kill the smaller one before dying. For example, would bursting out of the throat be more lethal than the stomach, since it could potentially damage the windpipe, jugular, and carotid?