Perioperative intravenous fluid therapy is an area of care that is often left to junior doctors1. Unfortunately, knowledge of basic physiology and the electrolyte content of various crystalloid solutions in this core group of care givers is recognizably weak1. In general, recognition of the hazards of sodium/water overload in surgical and anaesthetist communities has been poor2, 3, with the result that there now exists a routine of excessive crystalloid administration. In colonic surgery, a weight gain of 3–6 kg is typical4, 5. Sodium/water overload is a challenge for which mammals are phylogenetically unprepared; they lack appropriate mechanisms to counter such a situation. Several trials indicate that perioperative sodium/water overload is associated with poor outcome4–6