Dosage calculation loading dose and secondary dose

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Hi,

Can someone please help me. I can't seem to work this problem. I've tried for days. I've even pulled up old threads and worked it like one of them said to no avail. My test is next week - feeling discouraged.

1. Medication order: Loading dose, mix magnesium sulfate 20 g in 1000 mL D5W. Infuse 4 g over 30 minutes, then maintain at 1 g/hr. Maintain primary IV 1000 mL D5W at 60 mL/hr after magnesium sulfate loading dose.

Available: Magnesium sulfate 50% in 10 mL vials

Calculate the secondary rate for the loading dose.

Answer ________________ 400

I take the secondary dose as "then maintain at 1g/hr. I don't believe that I use the concentration of the magnesium in figuring the rate, but I have worked the problem with it in there.

DO: 20 g/1000 ml; secondary rate order then maintain at 1 g/hr

on hand; 50% in 10 ml vial, which I understand to be 50/100 concentration (do not believe i need concentration to work the problem)

so I did ML/HR = 1000 ml/20 g x 1/hr= 50

I've worked it where i changed the grams to ml = 0.05

I've worked it so many different ways and researched it, but I am just not figuring it out. Please help! Thanks in advance.

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Specializes in OR, Nursing Professional Development.

The secondary rate refers to how the infusion will be given- at the same time as the primary fluids. You will not stop the fluids while your medication infuses. I think that is what is throwing off your calculation, which is asking for the loading dose rate- the 4g over 30 minutes. Try it that way and see what you come up with.

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oops typo above - changed from grams to ml is grams to milligrams

Too funny; It so works. I had figured with both rates loading dose and maintain at 1g/hr in the problem, but not just the loading dose. I guess I was stressing myself out with such a lengthy problem with different terminology.

Thanks for the help!

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So, does it say calculate the secondary dose just to throw me off? What are the two different fluids that are infusing and which is infusing at 1g/hr? I guess I don't understand how the system works, which is why I couldn't figure out how to solve the problem.

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mix magnesium sulfate 20 g in 1000 mL D5W; I read this as they are mixed together as one - thanks

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.

1. Medication order: Loading dose, mix magnesium sulfate 20 g in 1000 mL D5W. Infuse 4 g over 30 minutes, then maintain at 1 g/hr. Maintain primary IV 1000 mL D5W at 60 mL/hr after magnesium sulfate loading dose.

Available: Magnesium sulfate 50% in 10 mL vials

Calculate the secondary rate for the loading dose.

Answer ________________ 400

Ok you need to mix mag sulfate 20gm in 1000ml D5W. You need to give a total of 4 grams over 30 mins for a loading dose from the 1000ml bag with 20gm of Mag Sulfate.

How many mls of that IVF contains 4grams of mag sulfate.....? Then infuse that amount over 30 mins.

Then decrease the infusion to infuse at 1gm per hour.

The distractor.....Maintain primary IV 1000 mL D5W at 60 mL/hr after magnesium sulfate loading dose. Which means you will eventually have 2 IV's running simultaneously after the loading dose it has no bearing on the actual problem.

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Thanks so much for helping me with that question. Here is another one that I can't see to figure out while it is simple.

There are several formulas. I was using the Devine formula, which worked for a similar question, which I pasted below. All possible formulas are below as well. These do not work out to the given answer. Please help - thanks

Males: IBW = 50 kg + 2.3 kg for each inch over 5 feet.

Females: IBW = 45.5 kg + 2.3 kg for each inch over 5 feet.

45.5+ [2.3 × (__ in. – 60 in.)] = 54.7 kg

24. Find the ideal body weight for a man who is 6 feet 3 inches.

Answer ________________87.5

50 + [2.3 × (75 in. – 60 in.)] = 84.5 kg devines

Men: IBW=106 pounds (lb) for first 5′ + 6 lb for each inch over 5′

106 + 6 x 15 = 196 lb divided by 2.2 = 89.09

Ideal Body Weight (in kilograms) = 52 kg + 1.9 kg for each inch over 5 feet(robinson)\

52 + 1.9 x 15 = 80.5

48 kg + 2.7 kg for each inch over 5 feet )\hamwi

48 + 2.7 *15 = 88.5

82. Find the ideal body weight for a woman who is 5 feet 8 inches.

Answer ________________63.9

45.5+ [2.3 × (68 in. – 60 in.)] = 63.9 kg

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.

I keep getting the answer you are getting...I would check with your instructor

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I sent him an email - thanks.

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