The Open Nursing Journal




ISSN: 1874-4346 ― Volume 13, 2019
LETTER

A Comprehensive Formula for Calculating the Infusion Rate of Medications Diluted with Infusion Solution



Mohammad Reza Soltani Zarandi1, Hadi Khoshab2, *
1 Inspection Unit, Police Hospital, Kerman, Iran.
2 School of Nursing and Midwifery, Bam University of Medical Sciences, Bam, Iran.


Article Information


Identifiers and Pagination:

Year: 2019
Volume: 13
First Page: 136
Last Page: 138
Publisher Id: TONURSJ-13-136
DOI: 10.2174/1874434601913010136

Article History:

Received Date: 18/04/2019
Revision Received Date: 19/06/2019
Acceptance Date: 24/06/2019
Electronic publication date: 31/07/2019
Collection year: 2019

Article Metrics:

CrossRef Citations:
0

Total Statistics:

Full-Text HTML Views: 679
Abstract HTML Views: 255
PDF Downloads: 275
ePub Downloads: 141
Total Views/Downloads: 1350

Unique Statistics:

Full-Text HTML Views: 340
Abstract HTML Views: 166
PDF Downloads: 131
ePub Downloads: 86
Total Views/Downloads: 723
Geographical View

© 2019 Zarandi et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: (https://creativecommons.org/licenses/by/4.0/legalcode). This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


* Address correspondence to this author at School of Nursing and Midwifery, Bam University of Medical Sciences, Bam, Iran; Tel: 00989132425700;
Fax: 003442510847; Email: hadikhoshab@gmail.com






DEAR EDITOR,

Drug administration is an integral part of the nurse’s role [1Bernius M, Thibodeau B, Jones A, Clothier B, Witting M. Prevention of pediatric drug calculation errors by prehospital care providers. Prehosp Emerg Care 2008; 12(4): 486-94.
[http://dx.doi.org/10.1080/10903120802290752] [PMID: 18924013]
], and drug calculations are one of the most important nursing care measures [2Khoshab H, Nouhi E, Tirgari B, Ahmadi F. A survey on teamwork status in caring for patients with heart failure: A cross-sectional study. J Interprof Care 2018; 1-7.
[PMID: 30207808]
]. There are various calculating formulas for different drug orders and the multiplicity of these methods has led to the difficulty of various calculations [3Toney-Butler TJ, Wilcox L. Dose Calculation 2018.] to the extent that one of the most common nursing errors is mistakes in the calculation of drug dosage especially, the infusion rate of drug solutions [4Wright K. Student nurses need more than maths to improve their drug calculating skills. Nurse Educ Today 2007; 27(4): 278-85.
[http://dx.doi.org/10.1016/j.nedt.2006.05.007] [PMID: 16876919]
]. A single formula that can comprise all different aspects of the physician's order, drug dose, and type of infusion set used and ultimately can express infusion rate in terms of drops per minute (gtt/min) and milliliter per hour (ml/hr) can partly reduce this problem. Mistakes in calculating the infusion rate are more important in Iran because of the limited financial resources for supplying the infusion pumps and other automatic injecting devices that have the ability of drug calculation and infusion rate. In this research, researchers tried to innovate a simple, uniform and applicable formula that can be used for a wide range of infusions.

Two of the valid and widely used formulas and their limitations and disadvantages are:

A) [5Ansel HC. Pharmaceutical calculations 2012.]

The most important limitations include:

(1) It is not able to calculate the infusion rate in gtt/min (because the type of infusion set is not included).

(2) The concentration of the drug should be available. Although the volume of drug solution and the amount of he drug (diluted) are usually present, the calculation of the concentration will prolong the process and the probability of errors increases.

(3) The dose of the drug should be in mcg, mg or a specified unit, while the drugs may be used in different units, such as gram.

(4) The units of drug dose and concentration should be identical, while this formula does not have the ability to make them identical.

B) [6Lapham R. Drug Calculations for Nurses: A step-by-step approach 2015.]

The most important limitations include:

(1) It is not able to calculate the infusion rate in gtt/min (because the type of infusion set is not included).

(2) The number 1000 is used for converting mg to mcg. Whereas, if the drug unit is in gram and the order is in mcg, then this formula is not applicable.

The benefits and advantages of our formula:

(1) The infusion rate is calculated in gtt/min, while having the ability to calculate it in mL/hr too (Tips for using this formula No 5).

(2) There is no need to calculate drug concentration.

(3) It is applicable for any type of drug unit.

(4) It is able to make different dose units and drug units identical.

(5) Unlike the two previous formulas, the type of infusion set is included.

The method of obtaining the formula is as follows:

As we know, the infusion rate (when the infusion time is known) is obtained from the following method:

On the other hand, if we do not have the total infusion time, we can get it from the following formula using the total dosage of the drug and the physician's order:

By replacing the second formula in the first, considering and applying other conditions (Drug orders based on the patient's weight, the difference of the drug unit with the physician's order, and finally the request for the administration of the infusion of the drug in terms of hours or minutes), the formula for calculating the infusion rate will be as follows:

Tips for using this formula:

(1) Regarding the use of this formula, the volume of the serum (or solution) should be in mL, and the physician's order and the total dose of the drug inside the serum (or solution) should be available.

(2) All physician's orders expressed as dose/time, or dose/weight /time, can be calculated and executed using this formula.

(3) The drug dosage can have any unit, but since the unit converter in the denominator is to equalize the unit of the drug dosage with the physician's order, it is only used when the drug unit in solution is not the same as the unit of the physician's order. For example, the drug is in mg, but the physician's order is in mcg (mcg/min, mcg/kg/min, etc.), in which case, the unit converter is 1000 (mcg = 1000mg). So if the dosage of the drug inside the serum (or solution) is the same as the unit of the physician's order (both mg, U, etc.), we will not use the unit converter in the denominator of the fraction.

(4) The drop factor is used in the numerator of the fraction to convert the serum (or solution) volume (ml) to the drop (gtt). In microset, this number is 60 (60 drops = 1 ml) and in the infusion set, it is 10, 15 or 20 (according to the infusion set type).

(5) To use the syringe pump for infusion, you must calculate the infusion rate as milliliter per hour (ml/hr). Also, in some infusion pumps, even using regular infusion set, it is necessary to set the infusion rate as ml/hr. On the other hand, we know that the infusion rate is in microset in gtt/min = ml/hr (1cc =60 gtts and 1h=60min). Therefore, through the microset formula (i.e, taking the number 60 as the drop factor) and taking into account, the solution volume (according to the volume of the syringe, serum, etc.) we reach the answer in gtt /min and set the same number as ml/hr on the infusion pump.

(6) The patient's weight in the numerator of the fraction should be used only for drugs prescribed by the weight (Example: mcg/kg/min). Note that the unit of the physician's order must be the same as the unit of the patient's weight (kg, lb…).

(7) Since the number 60 in the denominator is to convert hr to min, we only use it when the physician's order is expressed in terms of hours (mg/hr, u/hr, mcg/kg/hr, etc.). So, if the physician's order is in minutes (mg/min, mcg, mcg/kg/min, etc.), we will not use the number 60 in the denominator.

(8) Consider that if the dose of the drug in the solution changes (half, twice, etc.), we will use the same modified dose. For example, if 4 ampules of 100mg Lidocaine are poured in the serum (400mg), we use the number 400 in the denominator.

(9) It is recommended that we use this formula for infusions in which the total infusion time is not determined.

Applicable Example

Q: We want to infuse Midazolam according to the physician's order as 30mcg/kg/hr for a patient weighing 70kg. If we pour three 5mg ampules of this drug in a 20 ml syringe and dilute it to the volume of 20 ml, calculate the infusion rate:

A: As already mentioned, the infusion rate in the syringe pumps is in ml/hr, whereas the final infusion rate of the above formula is in gtt/min. But it has already been determined that in microsets, the infusion rate in gtt/min would be equal to ml/hr. Therefore, the drop factor here is 60.

=2.8 gtt/min =2.8ml/hr

(1) As the drug is prescribed by weight, then the patient's weight is used in the numerator.

(2) Since the dosage is in mg, but the physician's order is in mcg, the number 1000 is used in the denominator as the unit converter (mcg = mg × 1000).

(3) Since the physician's order is hour (mcg/kg/hr), the number 60 is used in the denominator to convert the unit into minutes.

(4) Because three 5mg ampules are used, the total dosage of the drug in the syringe is considered 15mg

FUNDING

None.

CONFLICT OF INTEREST

The authors declare no conflict of interest, financial or otherwise.

ACKNOWLEDGEMENTS

Declared none.

REFERENCES

[1] Bernius M, Thibodeau B, Jones A, Clothier B, Witting M. Prevention of pediatric drug calculation errors by prehospital care providers. Prehosp Emerg Care 2008; 12(4): 486-94.
[http://dx.doi.org/10.1080/10903120802290752] [PMID: 18924013]
[2] Khoshab H, Nouhi E, Tirgari B, Ahmadi F. A survey on teamwork status in caring for patients with heart failure: A cross-sectional study. J Interprof Care 2018; 1-7.
[PMID: 30207808]
[3] Toney-Butler TJ, Wilcox L. Dose Calculation 2018.
[4] Wright K. Student nurses need more than maths to improve their drug calculating skills. Nurse Educ Today 2007; 27(4): 278-85.
[http://dx.doi.org/10.1016/j.nedt.2006.05.007] [PMID: 16876919]
[5] Ansel HC. Pharmaceutical calculations 2012.
[6] Lapham R. Drug Calculations for Nurses: A step-by-step approach 2015.

Endorsements



"Open access will revolutionize 21st century knowledge work and accelerate the diffusion of ideas and evidence that support just in time learning and the evolution of thinking in a number of disciplines."


Daniel Pesut
(Indiana University School of Nursing, USA)

"It is important that students and researchers from all over the world can have easy access to relevant, high-standard and timely scientific information. This is exactly what Open Access Journals provide and this is the reason why I support this endeavor."


Jacques Descotes
(Centre Antipoison-Centre de Pharmacovigilance, France)

"Publishing research articles is the key for future scientific progress. Open Access publishing is therefore of utmost importance for wider dissemination of information, and will help serving the best interest of the scientific community."


Patrice Talaga
(UCB S.A., Belgium)

"Open access journals are a novel concept in the medical literature. They offer accessible information to a wide variety of individuals, including physicians, medical students, clinical investigators, and the general public. They are an outstanding source of medical and scientific information."


Jeffrey M. Weinberg
(St. Luke's-Roosevelt Hospital Center, USA)

"Open access journals are extremely useful for graduate students, investigators and all other interested persons to read important scientific articles and subscribe scientific journals. Indeed, the research articles span a wide range of area and of high quality. This is specially a must for researchers belonging to institutions with limited library facility and funding to subscribe scientific journals."


Debomoy K. Lahiri
(Indiana University School of Medicine, USA)

"Open access journals represent a major break-through in publishing. They provide easy access to the latest research on a wide variety of issues. Relevant and timely articles are made available in a fraction of the time taken by more conventional publishers. Articles are of uniformly high quality and written by the world's leading authorities."


Robert Looney
(Naval Postgraduate School, USA)

"Open access journals have transformed the way scientific data is published and disseminated: particularly, whilst ensuring a high quality standard and transparency in the editorial process, they have increased the access to the scientific literature by those researchers that have limited library support or that are working on small budgets."


Richard Reithinger
(Westat, USA)

"Not only do open access journals greatly improve the access to high quality information for scientists in the developing world, it also provides extra exposure for our papers."


J. Ferwerda
(University of Oxford, UK)

"Open Access 'Chemistry' Journals allow the dissemination of knowledge at your finger tips without paying for the scientific content."


Sean L. Kitson
(Almac Sciences, Northern Ireland)

"In principle, all scientific journals should have open access, as should be science itself. Open access journals are very helpful for students, researchers and the general public including people from institutions which do not have library or cannot afford to subscribe scientific journals. The articles are high standard and cover a wide area."


Hubert Wolterbeek
(Delft University of Technology, The Netherlands)

"The widest possible diffusion of information is critical for the advancement of science. In this perspective, open access journals are instrumental in fostering researches and achievements."


Alessandro Laviano
(Sapienza - University of Rome, Italy)

"Open access journals are very useful for all scientists as they can have quick information in the different fields of science."


Philippe Hernigou
(Paris University, France)

"There are many scientists who can not afford the rather expensive subscriptions to scientific journals. Open access journals offer a good alternative for free access to good quality scientific information."


Fidel Toldrá
(Instituto de Agroquimica y Tecnologia de Alimentos, Spain)

"Open access journals have become a fundamental tool for students, researchers, patients and the general public. Many people from institutions which do not have library or cannot afford to subscribe scientific journals benefit of them on a daily basis. The articles are among the best and cover most scientific areas."


M. Bendandi
(University Clinic of Navarre, Spain)

"These journals provide researchers with a platform for rapid, open access scientific communication. The articles are of high quality and broad scope."


Peter Chiba
(University of Vienna, Austria)

"Open access journals are probably one of the most important contributions to promote and diffuse science worldwide."


Jaime Sampaio
(University of Trás-os-Montes e Alto Douro, Portugal)

"Open access journals make up a new and rather revolutionary way to scientific publication. This option opens several quite interesting possibilities to disseminate openly and freely new knowledge and even to facilitate interpersonal communication among scientists."


Eduardo A. Castro
(INIFTA, Argentina)

"Open access journals are freely available online throughout the world, for you to read, download, copy, distribute, and use. The articles published in the open access journals are high quality and cover a wide range of fields."


Kenji Hashimoto
(Chiba University, Japan)

"Open Access journals offer an innovative and efficient way of publication for academics and professionals in a wide range of disciplines. The papers published are of high quality after rigorous peer review and they are Indexed in: major international databases. I read Open Access journals to keep abreast of the recent development in my field of study."


Daniel Shek
(Chinese University of Hong Kong, Hong Kong)

"It is a modern trend for publishers to establish open access journals. Researchers, faculty members, and students will be greatly benefited by the new journals of Bentham Science Publishers Ltd. in this category."


Jih Ru Hwu
(National Central University, Taiwan)


Browse Contents




Webmaster Contact: info@benthamopen.net
Copyright © 2019 Bentham Open