Life-sustaining medical treatment encompasses all interventions that may prolong the life of patients. Although LSMT includes the dramatic measures of contemporary practice such as organ transplantation, respirators, kidney (dialysis) machines, and vasoactive drugs, it also includes less technically demanding measures such as antibiotics, insulin, chemotherapy, and nutrition and hydration provided intravenously or by tube.
[Guidelines on Forgoing Life-Sustaining Medical Treatment, pdf]
This description of what falls under LSMT is confused, for it does not make distinctions among interventions that have important fundamental differences.
First, a little background. The human body needs a constant supply of a few things from the external world in order to sustain life: air, water, and food. The body must receive these from outside itself, as it does not have its own internal supply of these things. These are necessary for life. Helping to provide or ensure access to air, food, and water, does not come under the purview of what it means to practice medicine. This is simply required of any moral person as among those things owed to other persons without qualification. In the judgment of a reasonable person, deliberately shutting off the supply of any of these necessary things to the point of causing death, would be murder. The difference is that shutting off air would bring about death the fastest, then water, then food. But, whether fast or slow, shutting off access to any of these three would, without exception, bring about death sooner or later. Killing someone slowly as compared to killing someone quickly does not make an act less murderous. (The Nazis used starvation bunkers in their concentration camps as a particularly cruel way to kill those whose deaths they intended to be a punishment and a warning to others. They would lock up the condemned without food or water and retrieve the bodies days later.)
In addition to a constant supply of air, water, and food, the human body, in order to sustain life, must also carry on in a coordinated fashion a large array of internally regulated physiological processes. A few of these include heartbeat and circulation, breathing, digestion, cleansing the blood of chemical waste products, regulating blood pressure, recognizing and destroying pathogens (potentially disease-causing agents such as viruses and bacteria), controlling the uptake of glucose from the blood, and many others. Any of these complex, internally controlled physiological processes can stop working properly for a variety of reasons. The practice of medicine aims to support or cure injured, diseased, or weakened physiological processes, returning them, if possible, to a healthy state.
Also, in order that bodily life might endure in a healthy state, the body needs to be sufficiently free of aberrations--abnormalities that might impair or destroy necessary bodily functions. For example, cancer.
Now, turn again to the paragraph above about life-sustaining medical treatment. As I see it, there are three categories of "intervention" in this statement. They are:
1. Assisting in delivering the exterior things all human bodies must continuously bring in to sustain life (air, food, and water). Thus, ventilators, feeding tubes, and intravenously supplied nutrition.
2. Assisting the body to restore to a state of healthy operation any physiological functions that have been compromised or damaged. Normally, these functions do not need outside help. This might be done pharmacologically, nutritionally, mechanically, electromagnetically, or surgically (or in combination). Thus, antibiotics, insulin, vasoactive drugs, organ transplantation, and dialysis.
3. Destroying, removing, or otherwise neutralizing aberrations (such as tumors) that threaten to seriously impair or ruin necessary functions. Thus, chemotherapy (also surgery and radiation).
We must do what we can to provide category one assistance as long as the body can still actually make use of air, food, and water, and in the case of food and water, as long as the body is not in a state of near death from causes other than a lack of food and water.
For categories two and three, we must use all ordinary means at our disposal in the service of life, taking into account the likely benefits vs. burdens. And in considering this, restoring the body to a condition in which it is not dying (that is, from something other than normal aging) is always a benefit compared to death. If a person is truly dying and death is near ("at death's door"), and death cannot be prevented but only minimally delayed, there is no absolute obligation to try to put off an inevitable death for as long as possible. However, it must be kept in mind that allowing (i.e. not aggressively trying to prevent) a near and certain death to unfold--as in "letting nature take its course"--is not in the same moral category as killing someone by commission or omission. A deliberately chosen action or inaction which is chosen because it will bring about death, is immoral killing.
There is a problem here, as I see it, with the use of the term "life-sustaining medical treatment." The term itself seems to imply that anything that is "life-sustaining" should by that fact also be considered "extraordinary" (as a Catholic analysis would use the term) in potentially fatal situations. It seems like the mere acknowledgment of an intervention as LSMT gives permission to consider it optional (i.e. non-obligatory) when death enters the picture as a possibility.
What this seems to me to allow is a severe downgrading of what used to be a presumption in favor of life as medical professionals discharge their obligations to society. Formerly, so long as there was a reasonable chance of saving a patient's life, physicians accepted an obligation to try their best to save life. Now, under the more recent approach, if death is merely a possibility (but not a certainty), physicians no longer have an obligation to try to save life. The mere labeling of a medical intervention as LSMT seems to contain tacit permission to choose to forgo it when death is possible. It's a thought process almost like this: this treatment has the possibility of prolonging life; this case has a chance of being fatal; this treatment is therefore optional and may be omitted even if for the purpose of making death certain. It is a horrendous perversion of the most fundamental values that until recently have underpinned the medical profession throughout Western civilization.
If this sort of muddled thinking becomes more and more common in the realm of medical ethics, it won't be long before the only treatments that will be considered obligatory for medical professionals to undertake will be some treatments that have a high potential to heal non-fatal conditions.