F1.ii · Body Fluid Compartments

This VIVA will examine fluid physiology. How is water distributed in the body and how are these compartments measured?

This viva will explore your knowledge of measurement and regulation of body water. Describe the normal water content of a 70 kg adult male and how this water is distributed.

The viva will explore your knowledge of the body’s response to blood loss. Describe the physiological sensing and response following the loss of 1 litre of blood over 10 minutes in an adult male.

This viva is about intravenous fluids and buffers. Using the diagram below explain how fluid is distributed throughout the body of a healthy 70 kg adult male. (Image removed from report.)

This viva is on the physiology and pharmacology as it relates to blood volume and tonicity. Outline the response to loss of 1 L of circulating blood in an adult.

In order to pass this viva, candidates were expected to know the distribution of water in different body compartments, the difference in electrolytes composition in different compartments (E1), definition of osmosis and diffusion, and where osmosis and diffusion occurs in the body (B1f and D1), measurement and calculation of osmolality (E1), and how different intravenous fluids will be distributed in different body compartments (E2a). The common deficiency in the candidates’ answers included the difference in electrolytes composition between interstitial fluid and plasma and the reason behind it (F2a), how osmolality can be measured, the presence of an osmotic process in the medulla of the kidney where re-absorption of water occurs through the collecting tubules in the presence of anti- diuretic hormone (D1), and how the fluids will be distributed in the body when different intravenous fluids are administered. Syllabus : E1 2 References : Chapter 1 of Review of Medical Physiology by Ganong Vander’s Renal Physiology for details on this topic.