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A few thoughts on fluids, following an impromptu tutorial at work.
Trigger Warning: "Normal" saline
Every senior doc has words that trigger immediate education, it's just a thing. I think most of mine are fairly benign.
Trigger Warning: "Normal" saline
Every senior doc has words that trigger immediate education, it's just a thing. I think most of mine are fairly benign.
I used to work for an orthopod who had a violent allergy to the use of "weight bearing" as a verb. So at least I have some insight.
Bottom line, there's nothing "normal" about 0.9% NaCl solution, and it's a bit of a crap fluid for most patients. Great for cooking pasta, mind.
The use of the word "Normal" creates an odd framing bias, which leads lots of people to think it's the default. I tend to want to challenge this.
Use the right tool for the right job.
Use the right tool for the right job.
0.9% NaCl was principally adopted as it's easy to make. All you need is table salt, and sterile water. So, from a manufacturer's perspective, great. From a patients, not so much.
It contains 154mm/L of sodium, which is a bit more than normal plasma (135-145mmol/L). So it will push the plasma sodium up a bit. Good if hyponatramic, but remember more hyponatraemia is related to too much water, rather than not enough salt.
So consider why your patient is hyponatraemic, and as it's best corrected slowly, take time to manage the cause, not the numbers.
It has naff all else, so does nothing for other ion levels, except dilute them.
It's also got a pH of about 5, so just on its own, might make the patient acidotic.
It's also got a pH of about 5, so just on its own, might make the patient acidotic.
My real issue is the Cl ions. Normal is about 100-105mmol/L, so the 0.9% stuff has loads extra. That prompts hydrolysis, and additional H ions. This lowers the pH, and produces hyperchloaemic acidosis. It's rarely dangerous, but does tend to muddle the picture.
Whereas Hartmanns, or Compound Sodium Lactate (CSL), has lactate as pH buffer, and 4.5mmol/L of K. It also has a bit of Ca
So it reduces both acidosis, and avoids hypokalaemia.
So it reduces both acidosis, and avoids hypokalaemia.
Lots of people worry about the K ions. But if you give CSL to a patient with plasma K of 6.5, you will get a dilution, and it will fall.
In all but the dialysis dependent or impending renal patient, it's not a big deal.
In all but the dialysis dependent or impending renal patient, it's not a big deal.
So the next time you reach for a bag of "normal" saline, ask yourself, how normal is normal?
And if you're feeling bored, and a bit nerdy, have a look here https://www.nice.org.uk/guidance/cg174/resources/composition-of-commonly-used-crystalloids-table-191662813
