Figure This One Out

[Med5517]

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Who can figure this one out?

Find the Vancomycin Peak and Trough @ 3rd dose?

Patient Weight: 6.9kg
Patient Age: 11 Months
Patient Sex: Male

0545 Labs: Cr: 0.5, BUN 20

1100 Dose: Vancomycin dose of 700mg/90 min., yes 700mg

1800 Labs: Cr: 0.6, BUN 20

2000 Dose: Vancomycin Dose of 700mg/ 90min

2000 Labs: Cr: 0.7, BUN 21

0200 Dose: Vancomycin Dose: 700mg/90min

0430 Labs: Cr: 1.0, BUN 26

Who can figure this one out??😕

 

[PharmDstudent]

Who can figure this one out?

Find the Vancomycin Peak and Trough @ 3rd dose?

Patient Weight: 6.9kg
Patient Age: 11 Months
Patient Sex: Male

0545 Labs: Cr: 0.5, BUN 20

1100 Dose: Vancomycin dose of 700mg/90 min., yes 700mg

1800 Labs: Cr: 0.6, BUN 20

2000 Dose: Vancomycin Dose of 700mg/ 90min

2000 Labs: Cr: 0.7, BUN 21

0200 Dose: Vancomycin Dose: 700mg/90min

0430 Labs: Cr: 1.0, BUN 26

Who can figure this one out??😕

This needs to be moved to the pharmacy forum, not pre-pharmacy.

 

[k0ni]

This needs to be moved to the pharmacy forum, not pre-pharmacy.

Agreed. 😕

 

[bananaface]

done.

 

[PharmDstudent]

done.

I still can't answer the question...😳

 

[Med5517]

Was the Trough close to 149.00 and how about the peak?

 

[sdn1977]

When I get home from work I'll mess around with your numbers, but I don't think you'll get anything close to meaningful. I hope this was not a real patient! Is it some random textbook question?

 

[Epic]

Let me start off by saying Pharmacokinetic is not an accurate science.

The data you have provided is not sufficient to calcuate accurate levels. But using population data, the trough will be around 40ug/ml and the peak will be around 140ug/ml.

Very toxic levels. Check the baby's hearing also.

 

[Med5517]

This was an actual patient. The Trough was 149.31. Can anybody figure out the Peak?

 

[Epic]

Peak would have been about 100ug per ml higher than the trough because Vd in this pt is about 7 liters and 700mg will add about 100ug per ml...

So, about 250ug per ml.

 

[KARM12]

We already know the peak is ridiculously high based on the trough. Does it make a difference to even calculate it?

 

[Med5517]

Current research on Acute Vancomycin Toxicity is limited at best. This gives us a rare oppurtunity to investigate the limits of our science! Why indeed! This information can never be used as difinitive data but as in case reports, it does give us some insight into information we normally would not have access to.

I got a peak of 386ug/ml with a Vd of 6.5.

Where did I go wrong? Or did I?

By the way the patient had Tonic-Clonic seizures for 3 min. after the first dose with a glucose level of 18. 5 hours after the dose.

The childs Creatnine Tripled in 24 Hours.

The peak is the maximum level that we measure for serum toxicity, therefore, we can equate any subsequent abnormalities with a particular peak level.

 

[KARM12]

The real question is why was a baby given so much Vanco over such a short period of time?

 

[Epic]

Current research on Acute Vancomycin Toxicity is limited at best. This gives us a rare oppurtunity to investigate the limits of our science! Why indeed! This information can never be used as difinitive data but as in case reports, it does give us some insight into information we normally would not have access to.

I got a peak of 386ug/ml with a Vd of 6.5.

Where did I go wrong? Or did I?

By the way the patient had Tonic-Clonic seizures for 3 min. after the first dose with a glucose level of 18. 5 hours after the dose.

The childs Creatnine Tripled in 24 Hours.

The peak is the maximum level that we measure for serum toxicity, therefore, we can equate any subsequent abnormalities with a particular peak level.

Ok.. you and I agree on the Vd.. 6.5L. so what happens when you dump 700mg into a copartment of 6.5L? 700mg/6.5L = approximately 100ug/ml... right?

So..if trough was around 140ug/ml... another 700mg will add about 100ug/ml..so the peak will be around 240ug/ml.

 

[sdn1977]

Agree with Epic - but...with the caveat - we are dealing with a very immature metabolism so none of the parameters you have for adults works.

The seizures could be anything - not necessarily related to the vanc. What is the pts dx?

Given they were really loading this baby with vanc, they think they have a very septic baby & probably had other stuff on board. We can't comment without knowing all of it.

Now - why are they loading over time like this? Dose 1 @ time 0, dose 2 @ time 9h, dose 3 @ time 15hr - what's up with that? You're chasing steady state....It appears on the surface that different prescribers are writing - ER, resident, attending??? Could that be? If so, you need to consolidate all the loading doses into one general dose over a given set period of time then order a blood level drawn at the appropriate time. Are they doing q 24hr dosing? I really don't know what is the accepted practice in infants since I don't work with them.

Also - where are these levels being drawn from? I'm guessing the baby is not being stuck peripherally every 6h - probably drawn from a central line. Is the central line perhaps a double or triple lumen? If so, the nurse must be very, very careful to stop whatever infusion is running into the line he/she is drawing the level for (the vanc) for 10 min or so, flush with D5 or NS then draw the blood. Otherwise, you'll get a vanc level which correlates with what is in the lumen or very close to it - not the actual blood level.

You need to wait a few hours for steady state to occur. You take your best guess based on what the child's liver & kidneys are doing (why did the BUN & Cr increase over 24hr???) Normally, when a child comes in septic, your first lab values reflect dehydration & some organ damage secondary to dehydration. Fluid replacement changes that, but there may be other issues which impact this child. The kidneys seem to be taking an hit. You gotta ask why & how will the liver react as well. There may be some dye issues if the child had an MRI or CT as well, which is recoverable, but you'll need to decrease the dose for a bit.

For vanc - you want a high enough peak for a sufficient amount of time, otherwise it is drug wasted. I'm not sure with a child this sick you could test the hearing adequately. That's probably not the major concern at the moment, altho as Epic mentioned, it is a concern.

Did I ever mention why I hate to do peds/neonates???

 

[Epic]

Agree with Epic - but...with the caveat - we are dealing with a very immature metabolism so none of the parameters you have for adults works.

Yup...hard to predict clearance....

100mg/kg q8h... that's insane. Lawsuit.

 

[sdn1977]

Yup...hard to predict clearance....

100mg/kg q8h... that's insane. Lawsuit.

Protect yourself - get blood levels at the appropriate time. Stop chasing the loading doses. Ask one of the pedi/neonate rxs on here how often vanc is dosed @ thise age/wt/dx & do your trough/peak around the next dose.

No guessing - dose based on factual evidence, but gained factually. Go find out how the nurses are drawing!

Thats my advice.

 

[Med5517]

As far as the dosing, it was ordered q6 but the ER nurse forgot to give the 2nd dose on time at 1700. Then the child seized so the dose was not given until 2000.

As far as fluids, the child was on TPN at the time.

After the first 700mg dose was given, the labs showed very elevated liver enzyme levels.

Now as far as the Vd. By the next day, the child was dx with ARI. It would be difficult to determine but I would assume that the Vd does not remain constant. With the onset of Nephrotoxicity and liver damage, I would conclude that the Vd would increase at least after the first dose.

It seems that with the first overdose of medication, the kidneys go into a mini ARI. Now they are playing catch up trying to clear whatever they can stating with the smallest molecules first. Vd starts to increase. The body starts to get starved of Glucagon and there you have the seizure. As the larger molecules start to clear, Vd begins to decrease again. As Dextrose is introduced, the hypoglycemia resolves. When the next dose is given though, the GFR will definitely take a hit. Now your mini ARI gets more complicated and the Vd once again increases. Without being able to return to equalibrium, the kidneys will continue to decrease in efficiency until they are in full ARF.

I think that a straight 100ug/ml for a 6.5-7 Vd may not work here. That probably only works in a renally stable patient. But at least we have a starting point.

 

[Epic]

Why would volume of distribution fluctuate?

 

[Epic]

I think that a straight 100ug/ml for a 6.5-7 Vd may not work here. That probably only works in a renally stable patient. But at least we have a starting point.

Renal function affects clearance. Volume of distribution refers to the compartments where the drug is ditributed. Since Vanco is protein bound somewhat...about 55% I think, there are factors that may affect the Vd. However, it would be safer to assume Vd as a constant in a patient.

 

[no-see-um]

Neonates clear vanco faster. We also worry about overdosing with patients, but with antibiotics, underdosing is pretty important, as well. Some patients actually need higher doses of vanco.

 

[Epic]

Neonates clear vanco faster. We also worry about overdosing with patients, but with antibiotics, underdosing is pretty important, as well. Some patients actually need higher doses of vanco.

Yeah... but not as high as what this little patient received. Very unfortunate. Always double and triple check dosing for peds.