Math Phobia? Does math drive you nuts? Does it take you what seems like hours to complete your calculations? ME, TOO!

Transcription

1 Hi, I m Jamie Davis, the Podmedic, host of popular online radio programs such as The Nursing Show and MedicCast Podcast. I wanted to personally welcome you to this educational disc or online course because I think that this an important topic for all of us to review from time to time. You have purchased this video series because you are struggling with successfully computing medication math problems. Whether you are a nurse, physician, paramedic, or other medical professional, medication and drug calculations are a necessary part of your job. Patient safety depends on you calculating correctly each and every time. This ebook is part of a video tutorial series that includes both video and audio segments, slides of the presentations, and student handouts. It is designed to review and refresh medication math for medical professionals at all levels from EMTs and paramedics on the street to nurses, physicians and others. We ll take the basic concepts and break them down, simplifying them for you (and me). Math Phobia? Does math drive you nuts? Does it take you what seems like hours to complete your calculations? ME, TOO! I know that a lot of people who listen to my shows online think I m some kind of genius paramedic or nurse to do what I do. No, I work hard to produce the materials, research the facts, and when it comes to math, fall back on tried and true techniques to make it easier for me. Still think you can t do it? I think you can and I ll tell you why... If you can learn and master the steps of a basic assessment, then I am confident that you can learn the methodical steps to become a confident medical mathematician! The problem with most students whom I ve met is when they look at math, their eyes cross. Seriously! It s as if everything starts to swim around and before they know it everything just becomes a big jumble of numbers and signs. If only they had a step by step plan, a way of doing things that would allow them to be successful and safe when calculating patient doses and other medical math like metric conversions. This program is a road map to med math success for you. No one goes on a trip to a destination by just randomly driving and expecting to get there, or at least get there in a reasonable time frame. You DO NOT want to be arriving at medication dosages by accident! 1 Med Math Simplified - at NursingTopStudent.com

2 Since accidental dosing is not a desired patient outcome, we need to come up with a better way, together to get the job done. Here s what we re going to do. We re going to take things step by step - plan our approach so that every calculation becomes the same. We ll follow the same steps and complete the problem, the same way, every time. We ll start out with a review of some common conversions needed for medical calculations. Then we ll get into the Med Math Simplified plan for every formula. Finally, we ll touch on some of the tricks and short cuts that are out there and why it s not a good idea to become too reliant on them all of the time. SECTION 1: MEASUREMENT CONVERSIONS In these initial segments, we ll review the common measurement conversions out there and take a look at some of the non-standard ones, too. The most important conversions involve converting metric units to larger and smaller units. Next we ll look at non-standard unit conversions like converting pounds to kilos and some of the old apothecary weights and measures. Finally we ll look at setting up the math conversion problems to make sure we get the correct answer. The METRIC SYSTEM!!!! Ok, maybe that s a bit much, but this is really important. For some of you, this may be an easy review, for others, this may be the basis of you med math challenges. The important part is to stick around and review this info together so we can move forward. This is the basis of everything that follows. The metric system is easy because it is entirely based on units of ten. If you can count by tens and hundreds then the numbers are easy in the metric system. I have found, though, that the base units and prefixes tend to mix people up so we ll spend most of our time focusing on those. Just remember that the next higher or lower units of measure are either bigger or smaller by a factor of 10. Simply add or subtract a zero, or move a decimal point to convert the number to the next unit of measure. Metric base units: Meter is a unit of length or in really big lengths - distance. If you measure a pencil, it is a simple length measurement but measure how far it is to the next town, and it is better thought of as a distance. Still, it all is based on the meter as the root term. A meter is roughly equivalent to a yard in english measure or 3 feet. For reference, a man is about 2 meters tall. Gram is a unit of weight or mass. Depending on the thing being measured, it will either be a really big number (something heavy) or small number (lightweight). A gram is about the weight of paper clip. So it is pretty small - about.35 ounces each in english measures. 2 Med Math Simplified - at NursingTopStudent.com

3 Liter is a unit of volume or displacement. It is roughly equal to a quart in English measure. Let s move on to the metric prefixes. Remember each is a multiple of 10 s so you are just adding or subtracting zeroes, or moving the decimal a number of places to the right or left. Common Metric Prefixes: Kilo is the largest measurement prefix we ll be using. You will most commonly see this in measures of weight where you are estimating a patient s weight or converting from pounds to KILOgrams. Kilo signifies one thousand times the base unit so a kilogram is one thousand grams. Centi moves the base unit smaller, reducing the base unit by 100. You will most commonly see this in describing wounds or short distances on a body: for instance, the wound was 2 cm across and was 5 cm to the left of the patient s midline. A centimeter is 1/100 of a meter. You will most likely only use this in terms of length or distance and not for weights or volume. Milli makes the base unit one thousand times smaller. It is going to be the most commonly seen prefix in medication math as it refers really small divisors of the base units. For instance 1 mg is 1/1,000 of a gram (that s 1/1,000 of that paperclip). This is useful for volume measurement as well, since a liter is so large, a ml is a much easier unit of measurement for dosing medications in solutions. Micro reduces the base unit one million times and will most commonly be used in weights in micrograms. This is really small but it is important to note the difference and be very careful. If you mistake a microgram measurement for a milligram measurement, you will give the patient one thousand times their normal dose! 3 Med Math Simplified - at NursingTopStudent.com

4 Non-Standard Units of Measure Now we ll look at non-standard units of measure including the old apothecary system. This system is being phased out, but you may find an older physician who still prescribes using this system. The apothecary system is based in old, non-standardized weights and measures. This means that depending on your textbook or reference source, you might have two different conversions from drams to milliliters. The Joint Commission guidelines for medication safety and error reduction would call this a violation of standard practices and I, personally, would not take an order written this way. In cases where I received an order written in non-standard units, I would ask the doctor to rewrite it or a pharmacist to convert it for me. Conversions from teaspoons is useful for medications in solution for oral administration (pediatric meds particularly). A teaspoon is equivalent to 5 ml. The teaspoon is being phased out because a teaspoon is also the common name for a spoon in your flatware set. These are not standardized in any way so dosing is better with a measuring cup or spoon designed for medications. The same is true of the tablespoon, since many unknowing parents may just use a bigger spoon like a soup spoon or serving spoon. A tablespoon is three teaspoons or 15 ml. Here are some samples from the apothecary system. Other non-standard measurements include the ones listed below. These are more important since these are more commonly needed in calculations. Converting from pounds to kilograms happens quite frequently. pounds (lbs.) = 0.45 kg (2.2 lb/kg) teaspoon (t.) = 5 ml tablespoon (T.) = 15 ml ounce = 30 ml 4 Med Math Simplified - at NursingTopStudent.com

5 Conversion Math Formulas Let s look at conversions between metric measures as well as conversions between metric and the non-standard weights and measures. This requires setting up an equation that you will solve with some basic algebra. Setting up these equations or formulas is the key to correctly figuring med math. The formula is the most important part of the process so let s look a basic version of the formula first. Formula Layout: Figure out which value you want (what is the question asking you for?) Place that on the left side of the equation. Figure out the value(s) you have. Place that on the right side of the equation. Determine your conversion values. Multiply the value you have by the conversion values. Let s start with a basic conversion you ll be running all of the time - converting pounds to kilograms. Here s the practice problem: You have a patient who weighs 220 pounds. What is his weight in kilograms (kg)? Yeah, I know. We can all do this one in our heads. Every adult male is exactly 100 kilos, right? Seriously, though. Get in the habit of setting up these problems correctly from the start. Even on the easy ones. Look at the question again and follow our steps in laying out the equation for the first time. What do you want to know? -- The weight in kilograms. Place kilogram (kg) on the left side of the equals sign. What do you know? -- The weight in pounds. Place the weight in pounds on the right side of the equals sign. What is the conversion? pounds per kilograms. Multiply the weight in pounds by the conversion value 2.2 pounds per kilogram. NOTE: As you build the formula you ll need to keep a few rules in mind. You want the value labels to cancel out I ll turn that over though and say it s 1 kilogram per 2.2 pounds. And you need to get in the habit of doing that to make sure you are getting the answers you want. Put the corresponding value you want on top on the opposite side of the equation. 5 Med Math Simplified - at NursingTopStudent.com

6 Do the Math Let s convert this one. First, cancel out the pieces of the equation you can. Remember from your basic algebra classes, you may cancel values or like numbers on a one for one basis from the the top and bottom of the equation. That leaves you with 220 kilograms divided by 2.2. When you do the math and you get 100 kg. Now this whole time you ve been saying, Jamie, I already know that one. I can do it in my head! and you are right. But this is about setting up the equation so that you can run the equation the same way each and every time you need to do so. Let s try one more. The bag of saline you have is labeled 1 Liter. How many milliliters do you have? Ok, let s set up the equation again. What do you want to know? -- How many milliliters do you have. What do you know? -- You have 1 Liter. What is the conversion you need to use here? -- 1 Liter is equal to 1,000 milliliters. Remember to put the value you want on the top! Let s cancel out the values we can. When you do, you are left with a final answer of 1,000 milliliters. Conversion Review Let s review some key points before we move on to laying out more complex equations. Understand the underlying relationships of the Metric system. Know the different factors of ten for each of the various prefixes and how they modify the base values. Non Standard Conversions are out there even as we strive for a universal safe dosing and medication standard. It is important to recognize them and to memorize at least a few of them. Do the Math. The last part you have to do. Sorry. No tricks here. If you think you need additional resources or a refresher about basic math or algebra, I d suggest talking to your school about what resources and tutoring they make available. 6 Med Math Simplified - at NursingTopStudent.com

7 Quiz # 1 Conversion Math Convert the following measurements to the indicated value. Round decimal values to the nearest tenth pounds (convert to kilograms) 2. 3 ounces (convert to milliliters) 3. 2 table spoons (convert to milliliters) 4. 5 teaspoons (convert to milliliters) pounds (convert to kilograms) Convert the metric system values to the indicated value. Show all decimals values. 6. 1,250 ml (convert to liters) Liters (convert to milliliters) Grams (convert to micrograms) Grams (convert to milligrams) milligrams (convert to micrograms) Note about pounds to kilogram conversions. The values of 2.2 pounds per kilogram and 1 pound equaling 0.45 kg are rounded decimal values. The actual conversions are: pounds per kilogram or 1 pound equals kg. When using the rounded values, you will notice a minor difference if you use one calculation form versus another. This is a negligible difference in dosing calculations. To avoid confusion, for this tutorial series, we will use 2.2 pounds per kilogram as our standard conversion value for all weight conversions from pounds to kilograms. Answer key Quiz #1 1.) 36.4 kg; 2.) 90 ml; 3.) 30 ml; 4.) 25 ml; 5.) 61.4 kg; 6.) 1.25 Liters; 7.) 0.52 ml; 8.) 4200 mcg; 9.) 42 mg; 10.) 12,000 mcg 7 Med Math Simplified - at NursingTopStudent.com

8 FORMULAS Gathering Information There are four parts to laying out your formulas correctly and they all have to do with gathering and ordering your information. When you are asked a question on a test or quiz, you are given a set of information. That information is what you will draw from to answer the question. In some cases, there may be more information than you need and part of your job will involve weeding out the information that is important from the information that is not. Setting up your formula correctly will help but that weeding out process is part of another whole lesson on testing strategies that I am not going into at this time. Gather your information starting with your orders or what your test question is asking you. In the case of orders, that would be from your protocols, standing orders, or from an online order via medical control, such as administer 20 ml/kg fluid resuscitation. This is usually going to be stated in terms of the following values or something similar. What Final Dose Do You Need? mg/ml g/l Drops/Min (or gtts/min) mg/hour tablets/dose In the case of a test question, it is usually stated in clear terms although it may be inferred. For instance: A doctor writes orders for a patient to receive 4 mg of morphine sulfate IV push PRN for complaints of sharp pain. You have a vial with 10 milligrams of morphine sulfate. There are 10 milliliters of solution in the vial. There is no question specifically asked here but you would infer that an IV push indicates liquid measurement so you would use a syringe and the answer would be in milliliters. So the question here is asking How many ml do we need? 8 Med Math Simplified - at NursingTopStudent.com

9 Determine Medication Concentration After we have determined what our question or orders are asking us for, let s move in to looking at the available medications or concentration on hand. This may be a multiple step process in complex problems but we ll keep it to one step right now. You are looking for labeling information on your medication vials or IV bags such as: mg/ml g/l... mg dissolved in... 1 tablet contains... In our previous question, this would be 10 mg of morphine sulfate in 10 ml of normal saline. Finally, look at the orders or test question and determine what conversions you need to be prepared to do. This might be converting patient weight from pounds to kilograms or another conversion. Remember to use your metric system knowledge from our conversions segment of this video series. Factors of 10 are key and memorizing the major conversions. 1 gram = 1,000 mg 1 mg = 1,000 mcg 1 L = 1,000 ml Drip Set Factor is # of drops per milliliter (gtts/ ml). 9 Med Math Simplified - at NursingTopStudent.com

10 Layout Your Formula Now that you ve gathered your information let s layout our pieces using the formula we looked at during the conversion review earlier. I can t stress enough that no matter how complex your problem is, if you lay it out this way and work through it methodically, you will be successful. Time and again, when I show this process to people, the mistakes are made when people try to cut corners. Take this step by step and don t skip steps because you think you can combine things and do the math in your head. That is where the mistakes happen. We ll look at a simple problem now and then tackle a more complex one later on. Formula Example #1 Let s look at the medication math problem from the example earlier. Remember to gather information. It isn t a bad idea to write down the items as you come to them. Orders: Give patient 4 mg of morphine. You have a 10 ml vial with 10 mg of morphine inside. How many ml do you draw up? That is the problem from before. Let s look at the information we have and start laying the problem out for you. Start with what the problem is asking for and put it on the LEFT: How many ml? On the right side start with Concentration on hand. It is very important to make sure that the value on the top (the numerator) is the same on both sides of the equation. Fill in ordered dose to the right, in this case that is 4 mg ordered. Remember that you can cancel values and numbers that are the same on the top as the bottom of the equation. If you have set your problem up correctly, you will alternate values starting with the first items set up to the right until you have all information accounted for. When you cancel out, you are left with the values you need. In this problem, that is milliliters. Now do the math, which in this situation is easy since the only number left is four! The correct answer to this problem is 4 ml to be drawn up into the syringe. Formula Example #2 Let s do a more complex problem. Now for those nurses or transport paramedics with IV pumps, this dopamine problem doesn t crop up very often. The issue is one that is faced by anyone without an IV pump, so we ll take it on. It is also a common question on many paramedic tests and exams. 10 Med Math Simplified - at NursingTopStudent.com

11 First, gather your information: Orders: 5 mcg/kg/min Dopamine You have a 250 ml bag with 400 mg of Dopamine inside and a 100 kg patient. How many drops per minute do you set using minidrip set (60 gtts/ml)? This question is going to be more complex but don t cross you eyes and decide it s too hard. Complex does not mean hard it just has a few more steps. The steps are all simple. So let s take it one step at a time. First, what is the problem or order asking for? What do you need to know at the end? To give the dopamine to this patient using a minidrip IV set, you need to know how many drops per minute to administer. Ok, place that on the left. Cool, step one done. Next, we usually start with concentration on hand but since this question is asking for drip rate, let s use the drip set concentration information. The drip set is 60 drops per milliliter. This is important because we want to make sure our final values match from left to right. Match up the drops on the top and ml on the bottom. Now add in the drug we have on hand. We could call this 400 mg in 250 ml but we want to alternate values top and bottom. Since we already have ml on the bottom here with the drip rate, let s put ml on the top so we can cancel it out. This means we have 250 ml over 400 mg. Next we add the ordered dose. Since we have a wt measure on the bottom with the IV bag concentration, let s put the micrograms on the top here. I know we are going to have to convert it but then the formula wouldn t fit on the screen so we ll set it up this way and do the conversion as a separate step. You could lay the whole right side out with the conversion from milligrams to micrograms and it will be the same so feel free to do that on your paper -- You are doing this along with me, right? Ok! Let s pull out the pesky conversion part and leave the drops/ml part there. We know that there are how many micrograms in a milligram? There are one thousand micrograms in a milligram. Remember to alternate top and bottom so we can cancel values later on and you lay out the problem this way. 11 Med Math Simplified - at NursingTopStudent.com

12 You are about to get a funky answer to this conversion after you cancel the values out. You will get 1250 ml/kg 400,000 minutes. Just stay with me here, cause we are not done yet. Remember, step by step by step! Plug this back right where it all came from and you get -- We can cancel the ml values and then just do the first step of the math. Leaving you first with this and then with this. The final step is to see if the problem makes sense. Does it make sense that the patient gets drops per minute? Of course not and that is because we forgot something else. That answer is drops per kilogram. This answer is for drops per kilogram per minute. How many kilos was our patient? That patient was one hundred kilograms. So this is easy. Multiply the answer by 100 and you get drops per minute or rounded up to 19 drops per minute. Step number six is very important, especially in the field. If you are not sure of the answer or it looks wrong - DO THE CALCULATIONS AGAIN. For instance, you are figuring a milliliter syringe draw for an IM injection. You get a value of 20 milliliters after your calculations are completed. Using step 6, you realize that this is too much fluid for an IM injection. The answer might be 2 milliliters if you simply missed a decimal point somewhere or your conversion formula was wrong but DON T GUESS! Take your time and build the formula from scratch, double checking your numbers along the way. Pay special attention to the problem and areas where you suspect you went wrong (such as decimal placement and conversion formulas). You may find your mistake, complete the formula and have a value that is much more reasonable for the application or route of administration. Before we end this section on Formula Layout let s review: Formula Layout Review: Review Your Conversions Gather Information Layout Your Problem Run The Math Check Answer Against Knowledge 12 Med Math Simplified - at NursingTopStudent.com

13 Quiz # 2 Formula Math Layout and calculate the following drug dose problems. Round all doses to the nearest tenth except for drip rates which should be rounded up. 1. You have received orders to administer 10 mg IM of Merperidine (Demerol) to your patient. You receive a 1 ml ampule containing 25 mg. How many milliliters of the solution do you administer to your patient? 2. A patient with a suspected narcotics overdose is not breathing. Your protocol orders an IV dose of Naloxone (Narcan) at the rate of 0.4 to 2.0 milligrams titrated to return of spontaneous respirations. You draw up the full 2 milligram dose into a syringe from the vial containing 4 mg in 10 milliliters of solution. How many milliliters did you draw up into the syringe? Questions 3-5 all relate to the following scenario. You have a 60 pound 10 year old female who needs to receive pain management for a broken arm following a bike accident. You are ordered to administer 0.2 mg/kg of morphine sulfate to her. You get a pre-filled syringe with 4 mg of morphine sulfate in 4 ml of solution. 3. How many milligrams is her dose? 4. Do you have enough medication on hand? 5. You have gone back to the dispensary and exchanged the original syringe for a vial with 20 mg of morphine sulfate in 10 ml of solution. How many ml does the patient receive? Questions 7-10 all relate to the following scenario. A patient is brought up to your cardiac unit with an mini drip set (60 gtts/ml) IV drip of dopamine running at 30 drops per minute by your observation. The medication bag is labeled as 500 ml containing 800 mg of Dopamine. The orders are for this patient to receive 8 mcg/kg/minute. 6. Do you have all of the information you need to calculate if the drip rate is correct? 13 Med Math Simplified - at NursingTopStudent.com

14 Quiz # 2 Formula Math (page 2) 7. What else do you need to know? 8. A look at the patient s chart shows he weighs 68 kg, is the current drip rate correct? 9. What should the IV drip rate be for this patient? Questions refer to the following scenario: A 170 pound patient received 3 IV doses of the anti-biotic gentamicin over the last 24 hours. Each dose was 300 milligrams. The patient was supposed to receive no more than 7 mg/kg/day. 10. Did the patient receive the correct dose? 11. What was the patient s maximum daily dose supposed to be? Questions refer to the following scenario: A 130 kg patient in ventricular tachycardia received an IV bolus of Lidocaine at 1 mg per kg. A follow up drip at 2 mg/minute has been ordered. The solution bag you are using has 1,000 mg of lidocaine dissolved in 250 ml of normal saline. 12. What is the medication concentration of Lidocaine in mg/ml? 13. What drip rate would deliver the correct dose using a mini drip set (60 gtts/ml)? 14. The orders are to increase the dose to 3 mg/min. What would the new drip rate be? 14 Med Math Simplified - at NursingTopStudent.com

15 Quiz # 2 Formula Math (page 3) 15. You do not have a mini drip IV set and must use a maxi drip set with a rating of 20 drops per milliliter. What would the 3 mg/minute drip rate be using the new drip set? Answer key Quiz #2 (all answers figured independently - set up each problem separately without prior rounded results) 1.) 0.4 ml; 2.) 5 ml; 3.) 5.5 mg; 4.) No; 5.) 2.7 ml; 6.) No; 7.) Weight in kg; 8.) No; 9.) 20.4 or 21 gtts/min; 10.) No; 11.) mg/day; 12.) 4 mg/ml; 13.) 30 gtts/min; 14.) 45 gtts/min; 15.) 15 gtts/min 15 Med Math Simplified - at NursingTopStudent.com

16 USING TABLES, CHARTS, AND SHORTCUTS This segment in the Med Math Simplified series is going to cover using tricks and tables. We ll start with using pre-made tables that you might find in a pocket drug guide, for instance. Next we ll look at using patient specific tables such as what you might find for a patient in an ICU or critical care transport situation. Finally, we ll look at some of the more popular tricks and shortcuts which I left until last on purpose. We ll talk about why late on. Pre-Made Tables Using pre-made tables is very common and usually very safe in most situations. When produced by a trusted resource such as a reputable publishing or medical supply house, they are very reliable. They are commonly arranged by dose per weight. Dosing is standardized to meet most but not all situations so some caution is still advised. These tables and charts come in many shapes and sizes depending on their source. It may be a photocopied dosing chart used by your unit in a hospital. A drip rate table used in the back of a treatment protocol for EMS providers. Some pre-made tables are arranged for specific situations and caution should be used since some understanding of treatment context is important. In the case of a pediatric dosing tape, instead of dose per weight, they may be dose per height or length. In this case the tape is laid next to the child and where the child ends is where the dosing ranges start. Because these are created for pediatric patients, this is one of those situations where understanding the treatment context is important. Doses for a very small adult who matches a range on the pediatric tape would not be appropriate. Understanding treatment context is also true for very obese patients whose dense muscle body weight is less than their total body weight and may cause overdosing on certain drugs. When in doubt, consult with the prescribing resource (physician, nurse practitioner, or PA) before using a standardized chart for these patients. Finally, there are pocket ACLS or EMS guides with dosing tables in them. The same rules for caution apply to these guides as well, but they can be a very valuable resource. Here s an example of a pre-made dopamine drip rate chart. Remember that problem from the previous segment? Don t you wish you had this in your hands then? This dopamine drip table is laid out with the weight in kilograms on the left and dose related drops per minute rate in micrograms along the top. The reason I save this section for last is that you need to have the basis to make the calculations on the fly. What if your pocket guide fell out during an extrication or someone used the last photocopied guide on your unit and you need to dose your patient now? You need to know how to do these calculations. The guides are just the icing on the cake. 16 Med Math Simplified - at NursingTopStudent.com

17 Patient Specific Tables? Patient specific tables are more common in facilities with special patient populations such as pediatric hospitals, home care for chronic and seriously ill patients and they are common for inter-facility transport ambulances. I expect to see them more often since computers make creating these charts on a per patient basis easy to do. They are not commonly used in the emergency care setting due to the variety and scope of the patient population coupled with the resources at hand in the back of an ambulance. There is one exception to this standard, though. I ll revisit the pediatric assessment tapes again here since they qualify as a patient specific table of a sort. Pediatric assessment tapes are common in the pre-hospital setting since the need for pediatric medication dosing is generally a rare occurrence in that arena. Having the doses premeasured on a chart rather than memorized is a valuable resource for seldom used knowledge and skills. Patients with chronic illnesses and medical needs may have tables for use in their home care situations where the care givers may rotate in and out frequently. Special needs patients such as dialysis patients may have their own dosing regimen related to their kidney function. When to Use or Not Use Patient Specific Tables I ll refer back to my early days as a basic EMT. For the rest of you, think of the five R s rights of medication administration. Any question you can apply to a medication, you may apply to a patient specific dosing table. The five R s are: Right patient Right medication Right dose Right date Right route Is this chart for the right patient, right medication, dose, or dates? If the patient has lost 40 pounds since the chart was made 2 months ago, it probably doesn t apply to them any more. In the case of medical orders, is there a physician s signature accompanying the chart or table. This may not apply to every case but if it does for your application, you should look for it. When in doubt, fall back on your tried and true dosing calculations. 17 Med Math Simplified - at NursingTopStudent.com

18 Tips, Tricks and Shortcuts Many of the people who are looking for information on medication and drug calculations are looking for what is contained in this section of this series. This segment of the Med Math Simplified series was left for last for two reasons. First, because I didn t want students and providers to get lazy and not learn the process of calculating a drug dose on the fly. Second, these shortcuts and calculation tricks apply only to a relatively small segment of the medications or patient population. They are not useful for the vast majority of what you will actually need in a real patient care situation. Before we start into the shortcuts, I wanted to address some good tips to keep in mind as you work in a patient care setting. These shortcuts and time savers are okay, since they don t compromise patient care and improve on your efficiency in a safe manner. These are more of a tools of the trade list. Pocket items for drug dosing calculations include: Calculator Extra Pens/Pencils Note Pad or Scrap Paper Patient Chart, Vital Information, or Identifiers Pocket Guide with Reliable Charts and Medication Information Valid Order by Physician, Other Prescriber, or EMS Protocols Another useful trick for drug calculations is learning to guess a patient s weight correctly. First, guessing a patient s weight can be a chore. Some will tell you that most adults are okay with an assumption of a round easily divided figure (50, 100, or 150 kilograms). Even though it would be nice to think of every adult as one hundred kilos or multiples thereof, you would end up under or overdosing many of your patients. Here are some tips for getting a more accurate patient weight in the field or home care situation. Ask the patients Ask family members Compare the patient to bystanders (Careful with this one or you ll offend some poor old lady watching you work) Compare the patient to members of your crew NOTE: If you are using IV sets without IV pumps to deliver medication drips or fluid therapy, count your drip rates often and tape the drip-rate rollers down so they don t move as you transport the patient or, in the case of a hospitalized patient, no one adjusts it without you knowing. These dosing mechanisms are inexact and not preferred if an IV pump is available for dosing. 18 Med Math Simplified - at NursingTopStudent.com

19 Old Paramedic s Tricks I left this one for last on purpose because these techniques for arriving at patient drip doses really are cheating and when used without caution, you can kill or seriously injure a patient. I am not exaggerating here. If you use these tips and methods, you do so at your own risk and the risk of your patient. They apply to specific medications and work in very specific situations only. When used outside of those situations, these methods are worse than guessing. That said, let s move on. There are two primary methods used out there for common paramedic drugs. The Dopamine and Lidocaine clocks and the Dopamine Divide by Ten (and subtract two) method. Let s start with the two clock methods. Dopamine Clock Method The dopamine clock method is one shortcut that applies to dopamine administration. It assumes a dose of ten micrograms per kilogram per minute. Other doses that are multiples of 5 or ten can be arrived at by doubling or halving the resulting drip rate based on whether you double or halve the dose per kilogram per minute. The answers you receive will get you CLOSE to the correct drip rate for your patient. Design your clock face as shown in the diagram to the right. Inside the clock face, write the minutes of the hour (15, 30, 45, 60). Outside the clock face, write 400 next to the 15, 800 next to 30, 1200 next to 45, and 1600 next to 60 at the top. Find the patient s weight in kilograms. (I didn t say you wouldn t have to do any math.) In this example let s get a patient that s easy to figure and go with an 80 kilogram patient. Multiply the patient s weight by 10. (80 X 10 = 800) Find the 800 on the outside of the clock and the corresponding number on the inside of the clock is the drip rate in drops per minute. With this method, the challenges and guessing starts when you try to examine a patient who is 100 kilograms. Where is 1,000 on the outside of the clock and what is the corresponding number on the inside? You will find yourself figuring more math for most of these calculations than you might for a simple drug draw or using a pocket chart. Lidocaine Clock Method Start with some assumptions. (You know what that means) We assume that there are 4 mg of lidocaine for each milliliter of IV solution. This is equivalent to 2 grams of lidocaine in 500 milliliters of normal saline solution or 4 grams of lidocaine in 1,000 milliliters normal saline. Do the metric conversion and you get 4,000 milligrams in 1,000 milliliters or 4 mg/ml. You must also assume that you are using a minidrip IV set up which drips at 60 drops per milliliter. The system works on the principle that the minute values in the clock face at each quarter hour match up to 1, 2, 3, or 4 milligrams/minute IV drip rate at this medication concentration. 19 Med Math Simplified - at NursingTopStudent.com

20 The limitations of this method are related to the medication and the assumptions of the model. The advent of other, more reliable antiarrhythmics like amiodarone means that many systems are phasing out the use of lidocaine or pushing it to a second tier use in cardiac patients. Also, remember that this method only works for the specific concentration and delivery methods involved in the model. Other concentrations require calculation using the tried and true methods found at the beginning of this series. Dopamine 10 and 2 Method The following method for dopamine drip rates also makes some assumptions in order to work as expected. The Dopamine 10 and 2 method assumes that you have a patient 100 kilogram patient (220 pounds) or one that is pretty close to that weight. It also assumes that your dose is 5 micrograms per kilogram per minute. Take the patient s weight in pounds (220 lbs.) and divide that number by 10. ( = 22). Subtract 2 from the result of the weight calculation and that s CLOSE to the correct drip rate. What do I mean by close? I mean that as patient s weight moves farther from 100 kilos, higher or lower, this method becomes less accurate. Try this example and see what I mean. You have a patient who is 50 kilograms. Using the 10 and 2 method, you would divide the patient s weight by 10 to give you an answer of 5 and then subtract 2, leaving you with a drip rate of 3 drops per minute. This will severely underdose this 50 kilogram patient. How do I know? Let s check our answer using one of our earlier calculations in the formulas section of this series. We found that for a 5 mcg/kg/ minute dose, we had to administer drops per kilogram. Do the math and you get drops per minute or rounded up to 10 drops per minute. The 10 and 2 method has given a mere third of the expected dose which is unacceptable. Is It Ever Okay To Use The Shortcuts? A question I get a lot from listeners and students is, Is there ever a time to use these shortcuts and tips from the old paramedic s back of tricks. Sure there are. One of the best ways to use these methods is to check your work. Once you ve run the full formula and calculation, remember the step that asks if the answer makes sense? Use these shortcuts to double check your work. They will let you know if you are in the ballpark or not. For instance, remember the drip rate calculation from the example in the formulas section? The Dopamine ten and two method would provide you with a check on problem we did in the earlier segment. A 220 pound man, divided by 10 and subtract two gives you a drip rate of 20. We came up with 19 so we 20 Med Math Simplified - at NursingTopStudent.com

21 are in the range and our number is probably correct. If we had used our initial finding of less than a drop per minute, we would know that we were wrong when double checking with this method. Another time to use these shortcuts is in really unusual and urgent situations. These are situations that 99 percent of us will never encounter. (This can be interpreted by the lawyers out there as never.) If you find yourself in a situation when you literally have seconds to make a decision, make it and move on to the next patient. The key is to later make sure you come back and double check your dose the right way, and do it as soon as possible. Just to reiterate, I can t recommend these methods when performing actual patient care but I will leave it up to you to decide when and where you might need this. The final use for these old paramedic tricks is in megacodes. Some instructors love these things. It saves them time and for some of them, I think it seems to show you know the ropes. Just a note for those in my region. If you ever come by me in a megacode, you better do it the right way first! Then you can amaze me with your knowledge of parlor tricks and slight of hand. Let s review Tips, Tricks, and Shortcuts: Use Pre-Made Tables Carefully Patient Specific Tables Are Useful Use Tricks and Shortcuts Sparingly 21 Med Math Simplified - at NursingTopStudent.com

22 Medication Math Simplified Final Exam Convert the following values to the indicated format. Round all decimals to the nearest hundredth if necessary pounds (to kg) pounds (to kg) 3. 8 ounces (to ml) ounces (to ml) 5. 11,000 ml (to Liters) mcg (to mg) mg (to mcg) ounces (to ml) ounces (to Liters) mg (to mcg) 22 Med Math Simplified - at NursingTopStudent.com

23 Medication Math Simplified Final Exam (page 2) Complete the following medication calculations. Unless otherwise indicated, round all decimals to the nearest tenth. (Remember, all drip rates are rounded to the next whole number.) 11. A patient is experiencing congestive heart failure symptoms including pulmonary edema. Orders are received to administer 80 mg of furosemide to the patient IV. You have a vial of furosemide containing 100 mg in 20 ml. How many ml do you give this patient? The following scenario pertains to questions A 127 pound patient is experiencing a severe anaphylactic reaction to a bee sting. Your protocols indicate an IM injection of epinephrine in a dose of 0.01 mg/kg. You have an ampule of Epinephrine 1:1,000 (1 mg in 1 ml). The maximum dose you are allowed to give is 1 mg. 12. What is the patient s weight in kg? 13. What is the ordered dose for this patient in mg? 14. How many ml will you draw up in a syringe for injection? The following scenario pertains to questions You have orders to administer 0.25 mg/kg IV of Diltiazem (Cardizem) to a patient experiencing symptomatic atrial fibrilation. The patient weighs 162 pounds. The drug comes in a powdered form containing 100 mg. The recommended concentration in your drug guide is 5 mg/ml. 15. What amount of normal saline solution will you use to mix with the powdered drug to reach the recommended concentration? 16. How many ml of your concentrate will you draw up for your IV administration? 23 Med Math Simplified - at NursingTopStudent.com

24 Medication Math Simplified Final Exam (page 3) 17. A patient is supposed to take 100 mg of furosemide by mouth every day. The patient s pharmacy fills the prescription with scored tablets containing 40 mg each. The tablets may be cut in half. How many tablets should the patient take? 18. A patient is experiencing severe nausea and vomiting. The physician orders a single 4 mg slow IVP dose of Ondansetron (Zofran). You have a 20 ml container of the drug labeled 40 mg in 20 ml of normal saline. What is amount you would draw into your syringe for this patient? The following scenario pertains to questions A patient IV drip is set up using a maxi-drip set (15 drops/ml). The patient weighs 154 pounds. The orders are to administer 2 ml/kg/hour of D-5W. 19. How many ml per hour should the patient receive? 20. How many ml per minute? 21. How many drops per minute using the indicated drip set will deliver the desired dose? The following scenario pertains to questions A pediatric patient weighing 143 pounds with an occurrence of SVT (supraventricular tachycardia) is ordered to receive a dose of the drug Adenosine (Adenocard). The initial dose of 0.1 mg/kg is to be followed by up to two follow up doses of 0.2 mg/kg. Maximum initial dose is 6 mg with follow up dose maximums of 12 mg. You are handed a syringe with the correct dose in the amount of 6 ml. You know that the vial of the medication contained 60 mg in 20 ml. 22. How many milligrams of Adenosine are in the syringe you were handed? 23. Is the syringe you ve been handed the correct dose? 24 Med Math Simplified - at NursingTopStudent.com

25 Medication Math Simplified Final Exam (page 4) 24. If the dose is wrong, how many ml should be injected in the initial dose? 25. How many ml should be injected in the second or third doses? Answer key: Final Exam 1.) kg; 2.) kg; 3.) 240 ml; 4.) 600 ml; 5.) 11 L; 6.) 0.5 mg; 7.) 8,730 mcg; 8.) 1,920 ml; 9.) 1.92 L; 10.) 32 mcg; 11.) 16 ml; 12.) 57.7 kg; 13.) 0.6 mg; 14.) 0.6 ml; 15.) 20 ml; 16.) 3.7 ml; 17.) 2.5 or 2 1/2 tablets 18.) 2 ml; 19.) 140 ml; 20.) 2.3 ml/min; 21.) 34.5 or 35 gtts/min; 22.) 18 mg; 23.) No; 24.) 2 ml (maximum); 25.) 4 ml (maximum) 25 Med Math Simplified - at NursingTopStudent.com