Physiologic Failure: Multiple Organ Dysfunction Syndrome Timothy G. Buchman, Ph.D., M.D. Edison Professor of Surgery Professor of Anesthesiology and of Medicine Washington University School of Medicine St. Louis, Missouri 63110
[email protected] Acknowledgement: This work was supported, in part, by award GM48095 from the National Institutes of Health 2 Buchman Humans, like other life forms, can be viewed as thermodynamically open systems that continuously consume energy to maintain stability in the internal milieu in the face of ongoing environmental stress. In contrast to simple unicellular life forms such as bacteria, higher life forms must maintain stability not only in individual cells but also for the organism as a whole. To this end, a collection of physiologic systems evolved to process foodstuffs; to acquire oxygen and dispose of gaseous waste; to eliminate excess fluid and soluble toxins; and to perform other tasks. These systems—labeled respiratory, circulatory, digestive, neurological, and so on—share several features. • Physiological systems are spatially distributed. Food has to get from mouth to anus. Urine is made in the kidneys but has to exit the urethra. Blood may be pumped by the heart but has to reach the great toe. • Physiologic systems are generally spacefilling and structurally fractal. Each cell has demand for nutrients; each cell excretes waste. Information has to travel from the brain throughout the body. While not every physiologic system is self-similar at all levels of granularity, there is typically a nested architecture that facilitates function: microvillus to villus to intestinal mucosa; alveolus to alveolar unit to bronchial segment; capillary to arteriole to artery.