Hyponatremia: evaluating the correction factor for hyperglycemia.
OBJECTIVE
There are no controlled experimental data that assess the accuracy of the commonly used correction factor of a 1.6 meq/L decrease in serum sodium concentration for every 100 mg/dL increase in plasma glucose concentration. The purpose of this study was to evaluate experimentally the hyponatremic response to acute hyperglycemia.


METHODS
Somatostatin was infused to block endogenous insulin secretion in 6 healthy subjects. Plasma glucose concentrations were increased to >600 mg/dL within 1 hour by infusing 20% dextrose. The glucose infusion was then stopped and insulin given until the plasma glucose concentration decreased to 140 mg/dL. Plasma glucose and serum sodium concentrations were measured every 10 minutes.


RESULTS
Overall, the mean decrease in serum sodium concentration averaged 2.4 meq/L for every 100 mg/dL increase in glucose concentration. This value is significantly greater than the commonly used correction factor of 1.6 (P = 0.02). Moreover, the association between sodium and glucose concentrations was nonlinear. This was most apparent for glucose concentrations >400 mg/dL. Up to 400 mg/dL, the standard correction of 1.6 worked well, but if the glucose concentration was >400 mg/dL, a correction factor of 4.0 was better.


CONCLUSIONS
These data indicate that the physiologic decrease in sodium concentration is considerably greater than the standard correction factor of 1.6 (meq/L Na per 100 mg/dL glucose), especially when the glucose concentration is >400 mg/dL. Additionally, a correction factor of a 2.4 meq/L decrease in sodium concentration per 100 mg/dL increase in glucose concentration is a better overall estimate of this association than the usual correction factor of 1.6.
Hillier
T A
TA
Department of Internal Medicine, General Clinical Research Center, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
Abbott
R D
RD
Barrett
E J
EJ
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage* / Q000097:blood; D007328:Insulin / Q000008:administration & dosage* / Q000097:blood; D008297:Male; D015233:Models, Statistical; D012016:Reference Values; D012964:Sodium / Q000097:blood*; D013997:Time Factors
D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D012964:Sodium; D005947:Glucose