Posm and MS change

 Q: Severe neurologic deterioration in Diabetic Ketoacidosis (DKA) starts to occur once effective plasma osmolality (Posm) starts rising above 280 mosmol/kg?

A) True

B) False

Answer: B

The mental Status change is mostly due to higher effective plasma osmolality (Posm). Hyperosmolality is more common in HHS where an effective plasma osmolality (Posm) rises above 320-330 mosmol/kg. Point to be noted: One of the clinical presentations of HHS is stroke-like symptoms with hemiparesis and/or hemianopsia. It may also present with seizures. 

Although mental status change may occur in DKA due to severe degree of acidosis, frank coma is unlikely. 

Clinical significance: If a patient in DKA presents with frank stupor or coma, and an effective Posm is lower than 320 mosmol/kg, it should ignite a clinicians to look for other causes of encephalopathy.

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References:

1. Daugirdas JT, Kronfol NO, Tzamaloukas AH, Ing TS. Hyperosmolar coma: cellular dehydration and the serum sodium concentration. Ann Intern Med 1989; 110:855. 

2. Lavin PJ. Hyperglycemic hemianopia: a reversible complication of non-ketotic hyperglycemia. Neurology 2005; 65:616. 

3. Harden CL, Rosenbaum DH, Daras M. Hyperglycemia presenting with occipital seizures. Epilepsia 1991; 32:215. 

4. Nyenwe EA, Razavi LN, Kitabchi AE, et al. Acidosis: the prime determinant of depressed sensorium in diabetic ketoacidosis. Diabetes Care 2010; 33:1837.