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Pearse and Ackland rehearse the evidence that clinical estimation of fluid overload or depletion are unreliable, and recommend repeated measurements of cardiac output after boluses of colloid solution - a strategy that may work well on an ITU but is of no help at all to the reader working on the general surgical ward. The space would have been better used in explaining how the monitoring that they do recommend - 'clinical examination, fluid balance charts, regular weighing, and biochemical analyses' - should be used to make decisions in settings without access to cardiac output monitoring.