Hypernatremia and hypertonic syndromes

Hypernatremia in Hyperglycemia: Clinical Features and Relationship to Fractional Changes in Body Water and Monovalent Cations during Its Development

In hyperglycemia, the serum sodium concentration ([Na]S) receives influences from (a) the fluid exit from the intracellular compartment and thirst, which cause [Na]S decreases; (b) osmotic diuresis with sums of the urinary sodium plus potassium concentration lower than the baseline euglycemic [Na]S, which results in a [Na]S increase; and (c), in some cases, gains or losses of fluid, sodium, and potassium through the gastrointestinal tract, the respiratory tract, and the skin. Hyperglycemic patients with hypernatremia have large deficits of body water and usually hypovolemia and develop severe clinical manifestations and significant mortality. To assist with the correction of both the severe dehydration and the hypovolemia, we developed formulas computing the fractional losses of the body water and monovalent cations in hyperglycemia. The formulas estimate varying losses between patients with the same serum glucose concentration ([Glu]S) and [Na]S but with different sums of monovalent cation concentrations in the lost fluids. Among subjects with the same [Glu]S and [Na]S, those with higher monovalent cation concentrations in the fluids lost have higher fractional losses of body water. The sum of the monovalent cation concentrations in the lost fluids should be considered when computing the volume and composition of the fluid replacement for hyperglycemic syndromes.

Case Report : Severe Hypernatremia following treatment for Hyperosmolar Hyperglycaemic State : A pragmatic approach used to manage hypernatremia

The Hyperosmolar Hyperglycaemia State (HHS) is an endocrine emergency with a mortality rate between 10 and 50%. The mainstay for the treatment of this condition is vigorous IV fluid replacement with close monitoring of blood glucose, serum osmolality, and electrolytes. However, after initial resuscitation, patients can develop hypernatremia and raised serum osmolality, which have deleterious consequences. While hypernatremia in HHS can be treated with infusions of 0.45% saline or 5% dextrose, alternate measures such as intravenous (IV) hypotonic fluid infusion [e.g. 0.18% sodium chloride (NaCl) containing 4% dextrose and 0.15% potassium chloride (KCl)], or free water administration through a nasogastric (NG) tube can be used. We report the case of a 70-year-old man, who was initially admitted to a medical high care ward (MHC) with HHS, and was transferred to the ICU 72 hours later with an altered level of consciousness and severe hypernatremia. His treatment consisted in an IV hypotonic 0.18% NaCl infusion containing 4% dextrose and 0.15% KCl. He also received free water through a NG tube at a rate that was calculated to correct natremia at an average rate of 0.55 meq L-1 hr-1 over 72 hours. A multipronged approach was instituted to manage this patient, including, in addition to natremia correction, blood glucose control with insulin, appropriate IV antibiotics to treat infected foot ulcers, adequate analgesic medications, low-molecular-weight- heparin (LMWH) for thromboprophylaxis, proton- pump inhibitors, and continuation of patient’s ongoing antidepressant drugs at the time of his Glasgow Coma Score improvement. This case report demonstrates the feasibility and success of IV hypotonic fluid (0.18% NaCl - 4% dextrose - 0.15% KCl), alongside NG free water for correcting sodium levels with lower fluid volumes than would have been otherwise required if corrected with 0.45% saline. This treatment seems to be a reasonable choice for correcting sodium levels and osmolality in HHS patients who present with hypernatremia after an initial resuscitation, insofar as it avoids fluid overload and provides dextrose as an energy substrate, in addition to potassium ions. However, while correcting natremia with hypotonic fluid, other aspects of management should not be ignored.

Physiologic acid-base and electrolyte changes in acute and chronic renal failure patients

Patients with acute and chronic renal failure are vulnerable to a wide variety of acid-base and electrolyte disturbances. The variety is related not only to predictable disturbances that arise as a consequence of impaired urinary excretion, but also to associated factors, such as intercurrent disease processes, chronic medications, and renal replacement therapy. This article emphasizes the pathogenesis, diagnosis, and treatment of common problems, including metabolic acidosis, hyponatremia, hypernatremia, hyperkalemia, hyperphosphatemia, and hypocalcemia.

Hypernatremia and hypertonic syndromes

Hypernatremia is the most common cause of hypertonicity in small animal medicine. Despite this fact, severe hypernatremia is an uncommon clinical entity in dogs and cats. The causes of hypernatremia are excessive water loss and increased sodium intake. Clinical signs are most often related to CNS dysfunction. Severe hypernatremia should be considered a life-threatening situation and treated as such. Initial fluid therapy should be given with care according to the rate of onset of hypernatremia, as deterioration of the animal's condition is a common sequela. The determination of the cause of hypernatremia and the treatment can be both challenging and rewarding. The other notable hypertonic syndrome in small animal medicine is hyperosmolar nonketotic diabetes mellitus. Judicious management of this disease with fluid therapy and insulin is the standard therapy. An understanding of the pathophysiology is essential to their diagnosis and appropriate medical management.

A unique hypertonic response to hypotonic infusion in the pregnant ewe

OBJECTIVE

The purpose of this study was to compare the responses of the maternal ewe to intravenous volume expansion with either sufficient lactated Ringer's solution to elevate maternal venous pressure or sufficient hypotonic fluid to reduce blood osmolality.

STUDY DESIGN

Chronically catheterized pregnant sheep were intravenously infused over 4 hours with either commercial lactated Ringer's solution (5.55 +/- 0.50 L/hr, 255 mOsm/kg, mildly hypotonic) or diluted Ringer's solution (2.04 +/- 0.27 L/hr, 150 mOsm/kg, markedly hypotonic). Data were statistically analyzed with two- and three-factor analyses of variance and bivariate regression analysis.

RESULTS

During the mildly hypotonic infusion (n = 8) the maternal blood osmolality changes were -5.1 +/- 1.2, +2.7 +/- 1.0 and +6.8 +/- 1.1 mOsm/kg at 1 and 4 hours of infusion and 1 hour after the infusion. In four of the eight animals in this group profuse diarrhea developed. During the markedly hypotonic infusion (n = 11) the maternal blood osmolality changes were -9.9 +/- 1.1, -15.9 +/- 2.5, and -10.4 +/- 2.2 mOsm/kg at 1 and 4 hours of infusion and 1 hour after the infusion. Although urine osmolalities were significantly less than the osmolality of the infusate in both groups, only during the mildly hypotonic infusion was there a net loss of free water by the kidneys. The renal free water loss, the venous pressure increase, and the blood osmolality decrease were not significantly different whether diarrhea did or did not develop.

CONCLUSION

The infusion of large volumes of mildly hypotonic Ringer's solution to the pregnant ewe produces a paradoxic increase in maternal plasma osmolality as a result of the excretion of large volumes of free water by the kidneys, and if the venous pressure is increased more than about 6 mm Hg with this infusion, diarrhea develops in the animals.

Disorders of water balance--hyponatraemia and hypernatraemia

Plasma sodium concentration depends on water balance, and is normally maintained in a narrow range by an integrated system involving the precise regulation of water intake via thirst mechanism and control of water output via vasopressin secretion. Anything that interferes with the full expression of either osmoregulatory function exposes the patient to the hazards of abnormal decreases or increases in plasma sodium level. Hyponatraemia is almost always due to a defect in water excretion. Increased intake may contribute to the problem but is rarely, if ever, a sufficient cause. Hypernatraemia is almost always due to deficient water intake; excessive water losses may contribute to the problem, but they are never a sufficient cause. The most dangerous and usually the most blatant clinical effects of the disturbed water balance are those involving the central nervous system. Complex adaptive mechanisms have been developed to mitigate the impact of both hypo- and hypernatraemia on brain cells. However, the same protective changes render the brain more susceptible to severe neuropathology that may arise from inappropriate treatment of these disorders.

Hypernatremia

Hypernatremia results when the water content of body fluids is deficient compared with sodium content. Hypernatremia can be the result of pure sodium excess but is usually associated with dehydration, secondary to excess losses of water or hypotonic fluids. Hypernatremic dehydration is less common than hyponatremic or isonatremic dehydration, but is associated with the highest morbidity and mortality rate, primarily related to CNS dysfunction. Except when hypernatremia has developed rapidly, the serum sodium concentration should be corrected slowly with frequent monitoring of serum electrolytes. Even then CNS damage can result, either as a consequence of the hypernatremia itself or of rapid lowering of the serum sodium concentration.

Fluid and electrolyte balance in critical patients

Recognition and appropriate management of fluid and electrolyte disorders in critical patients is extremely important. In many cases, these secondary problems are more complicated and more serious than the initiating disease process. A severely ill diabetic patient, for example, is more likely to die from dehydration, hyperosmolality, metabolic acidosis, hypokalemia or hypophosphatemia than from hyperglycemia or lack of insulin therapy. Proper fluid therapy and treatment of electrolyte abnormalities make a major difference in the survival rate of critically ill animals.

Fluid management of shock in critically-ill patients

This article summarizes the theoretical basis and practical applications of the fluid management of shock in critically-ill patients. It also draws attention to the differences in the aetiology and management of fluid disturbances in adult and paediatric practice. Some evidence suggests that colloidal solutions alone may be superior to crystalloid solutions alone in the resuscitation of patients with shock, but in most situations a combination of both types of fluid is more logical.

Hypernatremia

Hypernatremia is a potentially life-threatening electrolyte abnormality. This problem develops most often because of loss of water from the animal, but in rare cases hypernatremia results from gain of sodium chloride. Important conditions predisposing to hypernatremia include diarrhea, vomiting, heat stroke, fever, limited access to water, excessive diuretic use, renal diseases, and pituitary diabetes insipidus. This condition rarely develops if animals have adequate access to water. Clinical signs relate to central nervous system derangements and can progress to seizures and coma. Diagnosis is based on the serum sodium concentration; treatment should be instituted if it is greater than 170 mEq per L. Treatment is based on knowledge of the volume status of the patient and the probable cause for the hypernatremia. In general, 5 per cent dextrose in water or other hypotonic fluids are given slowly intravenously. The rate of administration should be adjusted so the water deficit is replaced over 48 to 72 h. Too rapid correction of hypernatremia can lead to cerebral edema and worsening of the animal. In cases of salt intoxication, diuretics must be given in addition to slow water replacement to avoid the development of pulmonary edema.

Gross hypernatraemia associated with the use of antiseptic surgical packs

A severely ill patient with gas gangrene developed hypernatraemia associated with the use of wound packs soaked in a hypertonic solution called Eusol substitute, a commonly used stable alternative to true Eusol.