Normal Saline Question

[dmbgg]

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So, our professor had a question on a slide in my disease class that related to these two solutions. She stated that we should assume a patient has lost 1 Liter of blood volume, and we need to restore the volume quickly, what should we administer while waiting for the blood to arrive from the blood bank?

Which would be better: 5% dextrose (glucose) in water (D5W) or 0.9% NaCl in water? Why?

She told us it was Normal Saline (0.9% NaCl in water), but I forget by what mechanism she was mentioning it. Does Normal Saline increase extracellular volume by having a higher osmolarity due to the fact that it's nonpermenant to cells?

I am quite confused, so if someone can help explain the physiology, it would be greatly appreciated.

 

[xiphoid2010]

So, our professor had a question on a slide in my disease class that related to these two solutions. She stated that we should assume a patient has lost 1 Liter of blood volume, and we need to restore the volume quickly, what should we administer while waiting for the blood to arrive from the blood bank?

Which would be better: 5% dextrose (glucose) in water (D5W) or 0.9% NaCl in water? Why?

She told us it was Normal Saline (0.9% NaCl in water), but I forget by what mechanism she was mentioning it. Does Normal Saline increase extracellular volume by having a higher osmolarity due to the fact that it's nonpermenant to cells?

I am quite confused, so if someone can help explain the physiology, it would be greatly appreciated.

What will your body do to the dextrose once infused? Where do you think the water will end up?

LR may actually be the better fluid if you plan on giving a lot of it. Can you think of a reason?

 

[moolman]

What will your body do to the dextrose once infused? Where do you think the water will end up?

LR may actually be the better fluid if you plan on giving a lot of it. Can you think of a reason?

You're such a preceptor.... Haha

I'll go along and wait to post the answer until later then.

I don't think LR and NS make much of a difference, I know they say LR turns into bicarbonate and it's suppose to help but in trauma body can't make the conversion so use whatever you got.

 

[all4rx]

Basically, where is the fluid going to go? With hypovolemic patients, the goal is volume expansion, so use the fluid that puts the most volume into the intravascular space (NS or LR). If it's really just dehydration with primary goal is water replacement, use a hypotonic fluid (1/2NS or D5W).

So in your example, definitely NS will win over D5W. LR is also a good fluid to give as it's more close the physiologic fluid (think about what makes up LR). In my experience with fluid resuscitation at my hospital, LR is the fluid of choice for surgical docs whereas medical docs order NS most often.

 

[moolman]

Think of it this way, body fluid is divided 60% intracellular, 40% extracellular. Of this 40%, 75% is interstitial (bathes the cells), 25% is intravascular (blood).

D5W is metabolized into water and CO2. So you call it free water, meaning it goes everywhere, so if you give 1000ml of D5W, (40%) 400ml goes EC, of that (25%) 100ml goes to blood.

NS all of it goes to EC, so 1000ml, all of it goes EC, (25%) 250ml goes to blood.

Does that make sense?

Like I said ER docs rather use LR than NS because of the theory that LR is converted to bicarbonate and will help with metabolic acidosis but lactate metabolism is impaired during shock, so LR is not a good source of bicarbonate.

1000ml LR would also give you 250ml in the blood hence interchangeable for those purposes.

Something like albumin 5% is 100% to the blood, so if you give 1000ml, the persons blood volume goes up by 1000ml but realize that fluid is coming from the IC, so you're dehydrating the person.

As you can tell, I am studying for the BCPS, never worked a day in a hospital in my life so beware of what I just said.. Haha

 

[xiphoid2010]

Infusing large volume of NS quickly is known to cause hyperchloremic metabolic acidosis. So if it looks like the pt is going to need lots of it quickly, I would feel more comfortable with LR over NS.

The is some debate on the exact mechanism, and I can't recall exactly off the top of my head.

Ps. NS has a pH of 5.5, while LR's is 6.5. (not counting lactate metabolism)

 

[pharm B]

Thanks, guys. 🙂

 

[dmbgg]

Wow. Thanks for the response guys!

Sent from my SAMSUNG-SGH-I717 using SDN Mobile

 

[Trent Steele]

Think of it this way, body fluid is divided 60% intracellular, 40% extracellular. Of this 40%, 75% is interstitial (bathes the cells), 25% is intravascular (blood).

D5W is metabolized into water and CO2. So you call it free water, meaning it goes everywhere, so if you give 1000ml of D5W, (40%) 400ml goes EC, of that (25%) 100ml goes to blood.

NS all of it goes to EC, so 1000ml, all of it goes EC, (25%) 250ml goes to blood.

Does that make sense?

Like I said ER docs rather use LR than NS because of the theory that LR is converted to bicarbonate and will help with metabolic acidosis but lactate metabolism is impaired during shock, so LR is not a good source of bicarbonate.

1000ml LR would also give you 250ml in the blood hence interchangeable for those purposes.

Something like albumin 5% is 100% to the blood, so if you give 1000ml, the persons blood volume goes up by 1000ml but realize that fluid is coming from the IC, so you're dehydrating the person.

As you can tell, I am studying for the BCPS, never worked a day in a hospital in my life so beware of what I just said.. Haha

I was under the assumption that to get BCPS you need to have worked in a hospital for at least 3 years or have completed a one year ASHP accredited residency. Have they changed the requirements now?

 

[l3h]

When you give NaCl to your patient, it combines with water as follows: NaCl + H2O --> HCl + NaOH.
• The strong acid (HCl) and the strong base (NaOH) should cancel each other out, with no effect on pH.
• However, because the normal concentrations of Na and Cl in the serum are 140 and 100, respectively, adding 0.9% saline (154 mEq Na and 154 mEq Cl) causes the chloride to increase a lot more than the sodium.
• This increase in chloride tips the acid-base balance toward HCl, thereby causing the metabolic acidosis.

http://medicine.ucsf.edu/education/resed/Chiefs_cover_sheets/acid_base.pdf

 

[moolman]

No, I did a ASHP accredited residency, it just wasn't in a hospital. Still need to do that or 3 years of clinical work experience.