Hypertonicity: Clinical entities, manifestations and treatment

Abstract

Hypertonicity causes severe clinical manifestations and is associated with mortality and severe short-term and long-term neurological sequelae. The main clinical syndromes of hypertonicity are hypernatremia and hyperglycemia. Hypernatremia results from relative excess of body sodium over body water. Loss of water in excess of intake, gain of sodium salts in excess of losses or a combination of the two are the main mechanisms of hypernatremia. Hypernatremia can be hypervolemic, euvolemic or hypovolemic. The management of hypernatremia addresses both a quantitative replacement of water and, if present, sodium deficit, and correction of the underlying pathophysiologic process that led to hypernatremia. Hypertonicity in hyperglycemia has two components, solute gain secondary to glucose accumulation in the extracellular compartment and water loss through hyperglycemic osmotic diuresis in excess of the losses of sodium and potassium. Differentiating between these two components of hypertonicity has major therapeutic implications because the first component will be reversed simply by normalization of serum glucose concentration while the second component will require hypotonic fluid replacement. An estimate of the magnitude of the relative water deficit secondary to osmotic diuresis is obtained by the corrected sodium concentration, which represents a calculated value of the serum sodium concentration that would result from reduction of the serum glucose concentration to a normal level.

Fluid balance concepts in medicine: Principles and practice

“…Abnormal values of the measured [Na] S , or serum osmolality, or of serum tonicity calculated as the sum of the osmotic equivalents of [Na] S plus serum glucose concentration[ 34 ], indicate that there is a discrepancy between TBW and effective body solute; however, they provide no information about excesses or deficits of any of the particular determinants of tonicity. In fact, TBW may be low, normal, or excessive in patients with either hypertonicity[ 34 - 37 ] or hypotonicity[ 38 - 43 ]. Figure 1 shows changes in extracellular and intracellular volumes in euvolemic, hypovolemic and hypervolemic hyponatremia.…”

“…Hyperglycemic crises are associated with hypertonicity and severe deficits of body water, sodium, potassium, and other electrolytes[ 79 ]. The principles and quantitative aspects of treatment of these crises are detailed in several reports[ 37 , 79 - 81 ]. Herein we will present the principles of management of true (hypotonic) hyponatremia[ 43 ] and hypernatremia[ 37 ].…”

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“…There are different patterns of dehydration, depending on the causes of volume loss [3]. "Dry dehydration" is secondary to a negative water balance, while "wet dehydration" results from water redistribution [3,6,7]. The hypernatremic-hyperosmotic variant of dehydration is prevalent in the older subjects, those who cannot experience thirst or respond to thirst due to impaired mental status, but hypernatremic-hyperosmotic dehydration also occurs in enteral fed patients who are not provided sufficient fluids, in patients needing parenteral hydration but not adequately supplied, sometimes in patients with uncontrolled diabetes mellitus or diabetics receiving SGLT2 medication, as well as in patients with uncontrolled diabetes insipidus [6].…”

“…"Dry dehydration" is secondary to a negative water balance, while "wet dehydration" results from water redistribution [3,6,7]. The hypernatremic-hyperosmotic variant of dehydration is prevalent in the older subjects, those who cannot experience thirst or respond to thirst due to impaired mental status, but hypernatremic-hyperosmotic dehydration also occurs in enteral fed patients who are not provided sufficient fluids, in patients needing parenteral hydration but not adequately supplied, sometimes in patients with uncontrolled diabetes mellitus or diabetics receiving SGLT2 medication, as well as in patients with uncontrolled diabetes insipidus [6]. The prevalence of hypernatremia among older subjects varies: 3.7% in older patients living in the community [4], 2% among older patients admitted to hospital [8] and 15% of older patients admitted to hospital developed hypernatremia during hospitalization [9].…”

“…Clinical signs of dehydration include a dry mouth, inelastic skin, sunken eyes, though these features are not specific but in the extreme phase. Few symptoms may be present until sodium level exceeds 160 mmol/L [2,6,11]. Among laboratory features, hemoconcentration translates into hypernatremia, hyperosmolality, increased hematocrit and increased serum albumin; hypovolemia-induced impairment of renal function may produce a urea: creatinine ratio > 40.…”