The Japanese journal of physiology
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Serial measurements of extracellular fluid (ECF), and plasma volumes were evaluated in dogs before and during general anaesthesia with sodium pentobarbitone and under controlled conditions of arterial pH, pO2, pCO2, and blood pressure. Sodium pentobarbitone anaesthesia caused an early, significant rise in ECF volume with a fall in haematocrit, plasma protein, and plasma potassium concentrations. Plasma osmolality and sodium concentrations were unchanged. ⋯ It is unlikely that intracellular sodium stores contribute to a significant extent in these changes. During prolonged anaesthesia plasma volume progressively increased while total ECF volume returned towards control values. This work clarifies previous observations and suggests that major fluid movements occur during sodium pentobarbitone anaesthesia primarily associated with altered cell membrane properties and generalised haemodynamic changes.