Biomedical Engineering Reference
In-Depth Information
system failures can be managed by outpatient use of these devices: many pa-
tients thus gain years of useful life. The second advance was the development of
organ transplantation. Beginning with blood components (transfusion is a type
of transplantation) and progressing to kidney, heart, lung, pancreas, and intes-
tine, component replacement is increasingly frequent and relatively safe. Both
advances—mechanical support and tissue transplantation—compromise immune
system function, but this compromise is usually a good trade for survival.
It is hardly surprising that organ dysfunction and failures accumulate. Like
an aging automobile with worn bearings, cracked hoses, and leaky engine
valves, many humans eventually acquire an illness to which they cannot suc-
cessfully respond even with medical care—a bleed into the brain, a metastatic
cancer, or a high-speed motor vehicle crash. They die with multiple organs fail-
ing to perform their appropriate function. The subject of this chapter, however,
is a syndrome of widespread, progressive, and disproportionate multiple organ
dysfunction (MODS) that rapidly accumulates following a minor or modest in-
sult (2,3). Despite timely and appropriate reversal of the inciting insult—
whether a pneumonia, intraabdominal abscess, pancreatitis, or simply the stress
of an anesthetic and elective surgery—many patients develop the syndrome.
Mortality is proportional to the number and depth of system dysfunction (4),
and the mortality of MODS after, for example, repair of ruptured abdominal
aortic aneurysm, is little changed despite three decades of medical progress
(2,5). Unfortunately, MODS remains the leading cause of death in most inten-
sive care units.
2.
PREVIOUS WORK
2.1. MODS: The Phenotype
Autopsy findings in patients who succumb to MODS are surprisingly bland.
Tissue architecture is preserved, cells do not appear abnormal, and there is no
widespread thrombosis. At least anatomically, the body appears to be largely
intact. (The exception is lymphatic tissues, which are often exhausted through
accelerated programmed cell death [apoptosis] (6).) Nor does organ function
appear to be irretrievably lost: among MODS survivors, many—especially
younger survivors—experience return of multiple organ performance to levels
approaching that which they enjoyed prior to the syndrome (7). These two ob-
servations—anatomic integrity and the potential for near-complete recovery—
led to replacement of the old descriptor ("multiple organ failure") with the cur-
rent and more apt label of "multiple organ dysfunction syndrome." Using the
jargon of information technology, the focus shifted from the hardware to the
software (8).
Bearing in mind that MODS is only three decades old (multiple organ sup-
ports had to be developed and used in enough patients before it could be ob-
