Monday, August 9, 2010

CLINICAL CASE 23 , ANSWER and SUMMARY

A 56 y old male comes in with SIADH and a Na of 100, active seizures. You plan to give 3%. How would you give it?

Give 100ml of  3%Nacl bolus and repeat it maximum of 3 times within the first hour  38%

Give 3%Nacl at a faster rate of about 100cc/hr till Na is around 114 and then correct 0.5Meq/L for the remainder of the 24 hours    29%

Give 3%Nacl at around 60cc.hr and correct 0.5meq/L for the 24 hours  28%

Give v2 receptor antagonist   3%

Give 2%Nacl at 200cc/hr for 24 hours  0%


Interesting break down as expected. Majority of you are split between given 3% as  bolus vs. initial accelerating and then slowing down vs. just picking one rate and going with it.  The change in the paradigm of treating ACUTE symptomatic hyponatremia has been in the last few years.  Hypertonic saline is warranted in someone who is seizing and has a Na that is low; since if not corrected, brain herniation can occur.
Choice no 1 was initially described in hyponatremic athletes participating in endurance events such as marathon races. It consists of 100 mL of 3 percent saline given as an intravenous bolus, which should acutely raise the serum sodium concentration by 2 to 3 meq/L, thereby reducing the degree of cerebral edema; if neurologic symptoms persist or worsen, a 100 mL bolus of 3 percent saline can be repeated one or two more times at 10 minute intervals The rationale for this approach is that, in patients with symptomatic hyponatremia, rapid increases in serum sodium of approximately 4 to 6 meq/L can reverse severe symptoms such as seizures. If you use this approach, you might not need to do much for the remaining time over 24 hours and patient can start self correcting. 
Giving a bolus of 3% is not agreed upon by many Nephrologist. Take a look at the recent review that I pubmed below for a nice algorithm.  The usual goals for the overall rate of correction are to raise the serum sodium less than 10 meq/L in the first 24 hours and less than 18 meq/L in the first 48 hours. Choice B which is giving a drip of 3%Nacl initially at a fast rate should also work in such instances and perhaps physicians might feel more comfortable using that approach. The rate of 3% given in the third choice might be too slow for someone who is symptomatic.
So the most accurate answer is Choice A, but as you can see, there is no hard data and people might use diverse options( B>C as the next best answer). Giving a bolus of 3%NACL – where is this data coming from? When looked at Neurosurgical patients with cerebral edema who were normonatremic, a 30cc bolus of 23.4% saline increased the Na by 5mmol/L and there was an excellent and quick reversal of herniation. A 30cc of 23.4% saline is equal to 240cc of 3% saline. Based on these findings and a recent study on exercise induced hyponatremia in marathon runners, the International Exercise Associated Hyponatremia consensus development conference recommends that any athlete with hyponatremia and acute changes that are symptomatic ( seizures, encephalopathy) should be treated with 100ml of 3% NACL to acutely reduce brain edema. Two additional doses can be given over a 10 minute interval if there is no improvement.  Experts think that this approach is reasonable in any case of SEVERE ACUTE SYMPTOMATIC hyponatremia. Get the symptoms better, and then when you get to safe zone, you can correct more slowly or apply brakes with D5W or ddavp if need be.  If the cause was acute, rapid correction is warranted.   Chronic hyponatremia is a different story and asymptomatic acute is also a different story.
Take a look at these excellent references.


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