Practical aspects while treating a case of hyponatremia (experience sharing)

pratyush

Recently, I got to manage a case of acute hyponatremia. I want to share some practical aspects of the management.
Case
My granny 68-yr-old, 60 kgs in weight admitted to the TUTH for renal biopsy for nephrotic range proteinuria, had recurrent bouts of vomiting (around 14 episodes in 48 hours). The vomitus was watery around 250 to 300 ml per episode. During this period her intake was mainly ORS, fruit juice and very little amount of solid food. She had a history of inducing vomiting after fatty meals; and I made the mistake of not replacing fluid intravenously misguided by her bp and as we were busy administering Methyl Prednisolone pulse therapy for renal rescue.
The third morning she started developing fine rest tremors, and in the afternoon had an episode of seizure. I with the doctor on duty and the attendant nurses put her in lateral position with oxygen by nasal cannula, sent her blood for glucose and Sod./ Pot. and started her on 5% dextrose.
The report sent a chill down my spine. Na+:106mmol/L and K+ :3.2mmol/L

CORRECTION OF THE HYPONATREMIA
à We know we shouldn’t correct plasma Sodium rapidly for the fear of Central Pontine Mylinosis. According to Davidson, the rate of rise in plasma sodium shouldn’t exceed 0.5mmol/L/hr. (remember)
à Below 120mmol/L hyponatremia is corrected by hypertonic saline, which is available in our market as 3% NaCl (500 ml)
à Now 3% NaCl is 3 gm in 100 ml (remember the chemistry of class 11; weight by volume)
So 500ml of the solution contains 3*5= 15 gm of NaCl.
à Now 1 mole of NaCl is 23+35.5 , around 60 gm NaCl (again class 11 chemistry)
à So the 500 ml 3% NaCl contains, 15/60, i.e. 0.25 moles, i.e.250 millimoles of NaCl.

Now my granny’s 60 kg body contains 60* 0.55 = 33 litres of total body water.( ie. In a woman 55% of body weight is water)

Now we have, 250 / 33, i.e. around 7.5 millimoles/litre of NaCl can be replaced by the 3% NaCl.

Now not to exceed 0.5 mmol/L/hr, I had to replace the fluid in
7.5 / 0.5 i.e. 15 hours.

CALCULATING THE TOTAL BODY SODIUM DEFICIT.

I would want to correct the total body sodium to around 120 mmol/L with hypertonic saline, then probably by isotonic solution or by oral route.
So here 120-106 = 14 mmol/L of NaCl is to be replaced
As the total body water is 33 litres, 14 * 33 is = 462 mmol of Nacl..
As 500 ml of 3% NaCl contained 250 mmol of NaCl, probably 2 bottles of the solutions would suffice.

Understanding Rate of Fluid Infusion

Thanks for reading this far, which I hadn’t expected anyone to do.
It is fine if you don’t remember any thing I’ve mentioned above but do remember the following basics for life.
15 drops are approximately 1ml
So a 500 ml fluid contains 15 * 500 drops.
To administer 500 ml in 12 hours infusion rate should be 15 * 500 / (12 * 60) around 10 drops per minute.
Forget everything. 500ml in 12 hours rate 10 drops per minute. Rest is unitary method.

Result
My granny gained consciousness when we were midway of the second bottle and she was put on oral feed, encouraging salty fluids.

CSF

thanks a lot pratyush for sharing your experience with us, hope to see more experience sharing by you

its very practical and useful

bharat

ThiS Is ReALLy a helpfulpost, nice explaination. wish you could share more of your experience from TUTH. Thanks u very much And New year wish too.