The Corrected Serum Sodium Concentration in Hyperglycemic Crises: Computation and Clinical Applications

Abstract

In hyperglycemia, hypertonicity results from solute (glucose) gain and loss of water in excess of sodium plus potassium through osmotic diuresis. Patients with stage 5 chronic kidney disease (CKD) and hyperglycemia have minimal or no osmotic diuresis; patients with preserved renal function and diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS) have often large osmotic diuresis. Hypertonicity from glucose gain is reversed with normalization of serum glucose ([Glu]); hypertonicity due to osmotic diuresis requires infusion of hypotonic solutions. Prediction of the serum sodium after [Glu] normalization (the corrected [Na]) estimates the part of hypertonicity caused by osmotic diuresis. Theoretical methods calculating the corrected [Na] and clinical reports allowing its calculation were reviewed. Corrected [Na] was computed separately in reports of DKA, HHS and hyperglycemia in CKD stage 5. The theoretical prediction of [Na] increase by 1.6 mmol/L per 5.6 mmol/L decrease in [Glu] in most clinical settings, except in extreme hyperglycemia or profound hypervolemia, was supported by studies of hyperglycemia in CKD stage 5 treated only with insulin. Mean corrected [Na] was 139.0 mmol/L in 772 hyperglycemic episodes in CKD stage 5 patients. In patients with preserved renal function, mean corrected [Na] was within the eunatremic range (141.1 mmol/L) in 7,812 DKA cases, and in the range of severe hypernatremia (160.8 mmol/L) in 755 cases of HHS. However, in DKA corrected [Na] was in the hypernatremic range in several reports and rose during treatment with adverse neurological consequences in other reports. The corrected [Na], computed as [Na] increase by 1.6 mmol/L per 5.6 mmol/L decrease in [Glu], provides a reasonable estimate of the degree of hypertonicity due to losses of hypotonic fluids through osmotic diuresis at presentation of DKH or HHS and should guide the tonicity of replacement solutions. However, the corrected [Na] may change during treatment because of ongoing fluid losses and should be monitored during treatment.

Case Series: Management of Hypernatremia in DKA in a Tertiary Healthcare Setting in a Developing Country

“… 8 Corrected serum sodium provides a useful tool for monitoring and management during acute hyperglycemic crises by assessing the magnitude of the deficit of sodium and water and thus provides an initial estimate of the tonicity of the replacement fluids during the course of therapy. 9 The corrected sodium for case 2 was 128 mmol/L and with this hypertonic saline should not have been given and hence reduced chances of developing hypernatremia.…”

Edelman Revisited: Concepts, Achievements, and Challenges

“…The Edelman study has a few limitations. [Na] SW was not corrected for the degree of glycemia ( 17 ). In addition, formula 1, which describes a steady state, provides no information about the time to equilibrium during dynamic periods and does not include factors other than TBNa, TBK, or TBW measured in the steady state that could affect rapidly changing [Na] SW during development or treatment of dysnatremias.…”

Dysnatremias in Chronic Kidney Disease: Pathophysiology, Manifestations, and Treatment

“…Not accounting for the degree of hyperglycemia in studies of dysnatremias, i.e., using the measured [Na], provides false information about the relationship among body sodium, potassium, and water. The corrected [Na], i.e., a predicted [Na] value after the correction of hyperglycemia, provides an appropriate estimate of this relationship ( 56 ). Katz ( 57 ) calculated theoretically a decrease in [Na] equal to 1.6 mmol/L for each 5.6 mmol/L rise in serum glucose concentration.…”

“…Subsequently, the proposed range of coefficients for the calculation of the corrected [Na] was from 1.35 to 4.00 mmol/L reduction in [Na] for every 5.6 mmol/L rise in serum glucose ( 58 ). A review of this topic concluded that Katz's coefficient should be used for calculating the corrected [Na], with exceptions that make monitoring of [Na] and serum glucose during the treatment of hyperglycemia mandatory ( 56 ). The general form of the Al-Kudsi formula ( 59 ), which uses the Katz's coefficient to calculate the corrected [Na], is as follows where both sodium and glucose concentrations are in mmol/L ( 56 ): Several studies on dysnatremias calculated the corrected [Na] using the Al-Kudsi formula ( 30 , 34 , 36 , 41 – 43 , 46 , 47 , 49 ), and one study excluded from statistical analysis serum glucose levels >7.5 mmol/L ( 51 ).…”

“…A review of this topic concluded that Katz's coefficient should be used for calculating the corrected [Na], with exceptions that make monitoring of [Na] and serum glucose during the treatment of hyperglycemia mandatory ( 56 ). The general form of the Al-Kudsi formula ( 59 ), which uses the Katz's coefficient to calculate the corrected [Na], is as follows where both sodium and glucose concentrations are in mmol/L ( 56 ): Several studies on dysnatremias calculated the corrected [Na] using the Al-Kudsi formula ( 30 , 34 , 36 , 41 – 43 , 46 , 47 , 49 ), and one study excluded from statistical analysis serum glucose levels >7.5 mmol/L ( 51 ). This last study was also the only one to address spurious hyponatremia by excluding [Na] values in patients with significant hyperlipidemia.…”