Volume depletion in adults

Volume depletion is characterised by a reduction in extracellular fluid volume that occurs when salt and fluid losses exceed intake on a sustained basis.

The most common aetiologies are haemorrhage, vomiting, diarrhoea, diuresis, or third-space sequestration.

A detailed history and physical examination are crucial in determining the aetiology.

Signs and symptoms may include some of the following: postural dizziness, fatigue, confusion, muscle cramps, chest pain, abdominal pain, postural hypotension, or tachycardia.

Clinical symptoms usually do not manifest until large fluid losses have occurred.

Without proper assessment and timely resuscitation, volume depletion can lead to circulatory collapse and shock.

May be accompanied by electrolyte disturbance or acid-base disturbance.

In most situations, isotonic crystalloid is the best initial treatment for volume depletion. Balanced crystalloids may be preferable to normal saline in critically ill patients in intensive care and are recommended in patients with sepsis or septic shock.

Volume depletion is a reduction in extracellular fluid volume that occurs when salt and fluid losses exceed intake on a sustained basis.[1]Mange K, Matsuura D, Cizman B, et al. Language guiding therapy: the case of dehydration versus volume depletion. Ann Intern Med. 1997 Nov 1;127(9):848-53. http://www.ncbi.nlm.nih.gov/pubmed/9382413?tool=bestpractice.com [2]McGee S, Abernethy WB 3rd, Simel DL. The rational clinical examination: is this patient hypovolemic? JAMA. 1999 Mar 17;281(11):1022-9. http://www.ncbi.nlm.nih.gov/pubmed/10086438?tool=bestpractice.com [3]Batlle D, Chen S, Haque S. Physiological principles in the clinical evaluation of electrolyte, water, and acid-base disorders. In: Alpern RJ, Caplan MJ, Moe OW, eds. Seldin and Giebisch's the kidney: physiology and pathophysiology. 5th ed. San Diego, CA: Academic Press; 2012:2477-512. It may result from renal losses (diuresis) or extrarenal losses (from the gastrointestinal tract, respiratory system, skin, fever, sepsis, or third-space sequestration).[4]Di Somma S, Gori, CS, Grandi T, et al. Fluid assessment and management at the emergency department. Fluid overload diagnosis and management. Contrib Nephrol. 2010;164:227-36. http://www.ncbi.nlm.nih.gov/pubmed/20428007?tool=bestpractice.com Without proper assessment and timely resuscitation, volume depletion can lead to circulatory collapse and shock.[5]Rose BD, Post TW. Hypovolemic states. In: Clinical physiology of acid-base and electrolyte disorders. 5th ed. New York, NY: McGraw-Hill; 2001:415-46.

Dehydration and volume depletion are not the same, although they can co-exist in the same patient at the same time. Although often used interchangeably, it is important to distinguish one from the other. Dehydration implies a total body water deficit, alone or in excess of sodium loss, with a subsequent increase in plasma tonicity that usually comes to clinical attention as hypernatraemia. This hypertonicity implies intracellular water contraction whereas volume depletion implies blood volume contraction.[6]Bhave G, Neilson EG. Volume depletion versus dehydration: how understanding the difference can guide therapy. Am J Kidney Dis. 2011 Aug;58(2):302-9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096820 http://www.ncbi.nlm.nih.gov/pubmed/21705120?tool=bestpractice.com Symptoms of pure water loss arise from the effects of increased osmolality and reflect the cellular responses to hypertonicity: confusion, thirst, impaired sensorium, and, in more extreme cases, coma or seizures. By contrast, clinical symptoms of volume depletion are a result of the haemodynamic effects of the reduction in intravascular volume and usually do not involve neurological changes.