There are many factors present during long operations which might influence the serum sodium concentration. It is the purpose of this study to elucidate some of these and to determine whether the serum sodium concentration changes perceptibly during operations of several hours' duration. Significant gain or loss of water or of sodium during an operation should bring about such changes.
Although air conditioning has greatly diminished the loss of water through sweating, patients still lose body water by this means if the operation lasts for more than several hours. The sodium concentration in sweat is hypotonic; stress and trauma tend further to diminish its concentration. Therefore, water lost by sweating or ventilation would tend to increase the sodium concentration in the extracellular fluid. Ventilatory loss of water becomes more important in the presence of fever, dyspnea, diseases of the central nervous system, and tracheostomy.
The continual packing and manipulation of