Surgery in space. Phase I: Basic surgical principles in a simulated space environment.
The venturing forth of man into space confronts the surgeon with a new weightless environment with which he will inevitably have to contend. In this study operative procedures were performed on 20 rats in a simulated space environment with use of neutral buoyancy in order to identify those factors that could actually or potentially affect operative technique. There are three general areas of difference from normal conditions in simulated microgravity: physical adaptation to gravity deprivation tissue behavior, including bleeding; and the conduct of surgery. Without gravity, the tactile "feel" of objects is changed ("heavy" and "light" are meaningless terms) and proprioception is confused so that there is past pointing and overreaching of movements. Tissue planes tend to separate, and organs float and bob in the operative field, which makes clamping, cutting, and suturing different. Bleeding is a major consideration; surface tension tends to keep venous blood oozing along surfaces, whereas pulsatile arterial blood forms droplets, streamers, and clouds, depending on the force of the bleeding. These factors and others interfere with surgical technique in a number of ways: dispersion of blood obscures the surgeon's vision, sutures become entangled, organs are not stabilized, and instruments float into the operative field. The limitations of comparing neutral buoyancy to the true zero gravity of space are addressed. There is a definite need for further investigation for development of new surgical techniques in preparation for experimental and clinical surgery in space.