When a portion of the intestines do not have adequate blood flow, what causes sepsis to occur?
Bacterial waste products are toxic, and build up until they're released into the blood en-masse, resulting in a systemic inflammatory reaction and ultimately, severe sepsis.
When tissue does not get an adequate blood supply, the cells cannot receive the products they need to function, nor can they remove their waste products and they begin to die, and the tissue becomes necrotic.
The intestines are particularly hazardous though for a few reasons. Firstly, they can easily become twisted; leading to the formation of a life-threatening surgical emergency known as a volvulus; a twisted portion of bowel.
Not only are the intestines receiving an inadequate blood supply, but the torsion is also causing an obstruction, which causes whatever is in the bowels at the time, to build up. Without the blood supply, the body is unable to mount an immune response, and because of the location of the intestines, it is unable to do anything about the twisted portion of bowel.
Secondly, the intestines are a particularly troublesome location for such an injury to occur, because they're full of bacteria. With the body unable to send immune cells to respond to this threat, the bacteria begin to thrive; particularly as there is an abundance of nutrition for them to take advantage of as the cells begin to break down.
These bacteria are mostly anaerobic, and so don't require oxygen, and their metabolic products are incredibly toxic. When their waste products build up, they begin to cause damage to the surrounding tissues, and start diffusing into the bloodstream, where they quickly reach dangerous levels.
The body is largely overwhelmed by these toxins, and it attempts to control the situation. A massive inflammatory reaction is triggered that is both largely ineffective and counter-productive, and results in the condition known as Sepsis (Systemic Inflammatory Response Syndrome).
The heart rate and respiratory rate increase, and the blood pressure plummets. The body temperature becomes significantly elevated in an attempt to destroy the bacteria. This takes a great deal of energy though, and so as time progresses, the body begins to tire. As the biochemical processes in the body begin to slow down, it causes the body's core-temperature to drop.
Unless antibiotics are administered immediately, the patient placed on a ventilator, and the surgical emergency managed, the patient will quickly descend into multi-organ failure and septic shock, and ultimately, cardiac arrest (death).