Critical Systems (HB)

Life-threatening emergencies stem from a problem to one or more of the three critical systems: the circulatory system, the respiratory system, and the nervous system.

When the circulatory system fails to maintain adequate perfusion pressure, we call the problem “shock.” A failure of the respiratory system to oxygenate the blood is called “respiratory failure.” A failure of the nervous system is “brain failure.” Any one of these problems can cascade to the other systems and cause problems there as well.

For example, consider a patient that injected a recreational toxin–heroin. This toxin will cause impaired brain function and will result in a decreased respiratory drive. The respiratory system will not receive the signal to breathe, and as a result, the blood will not become adequately oxygenated. Tissues will be perfused but will not get the correct nutrients and will start becoming ischemic and eventually die. This ischemia also applies to brain tissue, triggering a feedback loop that, if left unchecked, will cause the patient to die.

Another example is a patient thrown from a horse and lands on a rock on their abdomen’s right side. The impact was sufficient to tear the liver, causing an internal bleed. As the patient is bleeding into their abdominal cavity, the body is trying to compensate by pulling fluid from everywhere it can. The heart beats faster in an attempt to maintain pressure while the volume is decreasing. Since blood moves through the system more quickly, the lungs start working faster, trying to keep up with the oxygenation demands. Eventually, enough fluid has been lost, and the patient cannot maintain pressure, and tissues become ischemic, including brain tissues. Brain failure occurs shortly after.

Early recognition of a critical system problem along with appropriate treatment can prevent this cascade. Your goal is to assess a patient and determine if they have a problem with a critical system, what stage it is at, and how to anticipate problems that arise from the inability to fix it.