Corrected sodium underestimates sodium

Hyperglycemia lowers serum sodium levels; the degree to which has been updated from the previous dogma of:

Conventional Units: For each 100 mg/dL (over 100 mg/dL) the blood glucose rises; the measured serum sodium should have 1.6 mEq/L added to it in order to correct for the effect of the hyperglycemia.

SI Units: For each 5.6 mmol/L (over 5.6 mmol/L) the blood glucose rises; the measured serum sodium should have 1.6 mmol/L added to it in order to correct for the effect of the hyperglycemia.

In an interesting trial where the effects of hyperglycemia on sodium levels were actually measured, Hillier, et al. demonstrate that the correction factor of 1.6 is inaccurate and leads to serious underestimation of serum sodium levels; especially in those patients with blood glucose concentrations of >500 mg/dL. The clinical information from this; study, is that a factor of 2.4 is more appropriate.

We are now utilizing the 2.4 adjustment factor. The formulas for each are below:

Conventional Units:
Glucose = mg/dL Sodium = mEq/L For each 100 mg/dL (greater than 100 mg/dL) the blood glucose rises; the measured serum sodium should have 2.4 mEq/L added to it in order to correct for the effect of the hyperglycemia.

• Corrected Serum Sodium = Measured Serum Sodium + [(Glucose measured - 100)/100]x2.4

SI Units: For each 5.6 mmol/L (greater than 5.6 mmol/L) the blood glucose rises; the measured serum sodium should have 2.4 mmol/L added to it in order to correct for the effect of the hyperglycemia.

• Corrected Serum Sodium = Measured Serum Sodium + [(Glucose measured - 5.6)/5.6]x2.4

Reference:
Hillier TA, et al. Hyponatremia; evaluating the correction factor for hyperglycemia. Am J Med April 1999;106:399-403. Huffman, GB. Adjusting Sodium Levels in Patients with Hyperglycemia. Am Fam Phy. 15 October 1999;60(6):1798.

Electrolytes

Hyponatremia (Corey Slovis)

• Acute (less than 48 hours), Chronic (more than 48hours) emedicine
• Chronic: usually diuretic use with low salt diet in CHF; most are stable and needs no treatment or water restriction for mild cases
• causes of acute severe symptomatic: water intoxication (eg marathoners who drink water but without sodium; ecstacy users who drink a lot of water) and SIADH
• Morbidity/Death if untreated: Brainstem herniation and CPM

When to treat?

1. Coma, Seizure, Focal findings (CSF) on a previously well patient (not poor premorbid)
2. below 120 mEq/L usually 100-110 mEq/L

*seizures may appear at level below 115 mEq/L with 50% mortality (source: Geriatric Emergency Medicine by Meldon)

What to treat? Rate?

• Hypertonic Saline Solution (3%)
• 100mls (2ml/kg) x 10 minutes, if still seizing 100 mls x 50 minutes

Target increase?

• 3-5 mEq/L

Max?

• 0.5 meq/hr or less OR 10-12 meQ/day (24x0.5)

If too rapid a correction?

• Give D5W

CPM (Central Pontine Myelinolysis)

• demyelinating disease of pons and CNS
• flaccid paralysis, dysarthria, hypotension
• alcoholics, malnourished, severely ill
• due to rapid correction of hyponatremia
• may be seen 1-2 days after correction

Nice to know (Sodium levels)

• 0.9% NaCl = Normal Saline Solution: 154 mEq/L of Na and Cl

Hypertonic (due to hypertonicity, may result to phlebitis, tissue necrosis, should be via central venous catheter)

• 3% NaCl: 468 mEq/L
• 5% NaCl: 856 mEq/L

Hypotonic

• 0.45% NaCl (usually with D5): 77 mEq/L of Na and Cl, 50 g/L glucose
• 0.22% NaCl: 39 mEq/L of Na and Cl, and always contains 5% dextrose for osmolality reasons
  

new LBBB and MI

Is new LBBB, treated as MI? (eg for thrombolysis/PCI?)
This data is anectodal. Data from Fibronolytic Therapy Trialists' (FTT) Collaborative Group in Lancet 1988 (?) says that fibrinolysis benefits those with MI, BBB (did not specify if Left or Right, and did not specify if new or old).

In another note, LBBB with MI is now becoming clear. More and more specialists are saying it is possible to diagnose MI in the presence of LBBB

Hyperkalaemia

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1413606/