F1.i · Osmosis & Colloid Osmotic Pressure

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

This viva will explore your understanding of urea and renal tubular function. Why do we produce urea and how effective is it as an osmole?

This viva will explore your knowledge of renal physiology and pharmacology. Describe the factors that determine the rate of movement of a solute across a semi-permeable membrane.

This viva will explore your knowledge of renal physiology and pharmacology. Describe the factors that determine the rate of movement of a solute across a semi-permeable membrane.

This Viva tested knowledge on intravenous fluids. It explored understanding about colligative properties, anion gap and moved on to the pharmacology of frusemide.

This Viva will explore your knowledge of fluids and colligative properties. What is in a bag of 0.9% Saline? Subsequent questions explored knowledge of osmolality, osmolarity, mannitol, colligative properties of fluids, anion gap, classification of diuretics and mechanism of actions.

This Viva will examine your knowledge of the pharmacology of common resuscitation fluids. Q 1. What is the composition of Hartmann’s Solution? As this viva developed it sought an understanding of “balanced solutions”, difference, adverse effects of intravenous solutions and difference between crystalloids and colloids and distribution of common intravenous solutions within the body. Candidates mostly had difficulty defining and differentiating a colloid from a crystalloid. A colloid is defined as a substance dispersed evenly throughout another substance. The hydrocolloids consist of colloid particles dispersed in water and as such the solid particles may be unable to pass through a semi-permeable membrane, thus exerting a colloid osmotic force and preferentially expanding the intravascular volume.

This Viva will examine knowledge of intravenous fluids, colligative properties What is in a bag of Normal Saline? Areas of knowledge that candidates were tested on included concepts of osmolality, osmolarity, anion gap, mannitol, and colligative properties of fluid. In addition this viva tested knowledge of the pituatary gland, specifically anatomy, hormones secreted and in particular, Anti Diuretic Hormone.

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.