Iranian Journal of Critical Care Nursing Fall 2009, Volume 2, Issue 3; 113-115
Nurses' drug calculation ability in Intensive Care Unit
Nasiri E.* MSc, Babatabar H. D.1 MSc, Mortazavi Y.2 MSc
*
Faculty of Paramedicine, Mazandaran University of Medical Sciences, Sari, Iran;
Faculty of Nursing, Baqiyatallah University of Medical Sciences, Tehran, Iran;
2
Paramedicine Faculty, Mazandaran University of Medical Sciences, Babol, Iran
1
Abstract
Aims: Serving multiple forms of drugs, specially those used in milligrams, milliequivalents or concentration/percent,
mostly by nurses could be a source of calculation error. This study was performed to investigate nurses' calculation error
related to drugs which are mostly used in ICU.
Methods: In this descriptive study, 36 randomly selected ICU nurses of hospitals affiliated to Mazandaran university of
medical sciences completed a questionnaire including demographic items and 5 questions about the three main drugs used
in critical conditions. The answers were evaluated and categorized in three levels (low, moderate and good).
Results: Most ICU nurses’ (55/5%) drug calculation ability was moderate. There were no significant difference between
male and female nurses in drug calculation ability.
Conclusion: Nurses' drug calculation ability in non milli- or microgram unit drugs is low or moderate and they make lots of
mistakes. So, it is suggested that all ICU nurses learn drug calculation and attend some related educational classes.
Keywords: Intensive Care, Drug error, Nurses, Drug Calculation Ability
Introduction
The feature of special wards such as operating rooms
and intensive care units, in which patients need a
precise and tight care and treatment, and expectation
of urgent and critical situations, is always a matter of
concern for medical staff that take care of patients.
Due to the critical and complicated situation which
exists in the controlling very sick patients and their
higher mortality compared to other wards’ patients,
double job stress is put on treatment and care
processes and may lead to increase of error in care
process [1, 2]. Due to continuous presence in intensive
units, nurses play an important role in improvement
trend of very sick patients who need tight care. Errors
related to intravenous injection, misuse of equipments
and techniques, drug calculations’ error and other
cases have been reported in various studies. Among
various types of errors, computational errors related to
medications and drugs have been more reported [2]. In
addition to inadvertent and possible errors presented in
all parts of hospital, especially ICU, the difference in
types of medicines, may cause errors in the dosage
calculation provided for patient.
Majority of drugs are prescribed based on the
medicinal substance weight and their calculation is
done according to patient’s weight. In addition, a large
number of drugs are in injection form and the density
of drug in solvent is specified in milligrams or
micrograms in ml. Therefore, the amount of drug that
patient needs, can be easily, accurately and quickly
determined and calculated. However, some of
* Correspondence; Email: rezanf2002@yahoo.com
significant and applied drugs required in ICU, do not
follow this trend and are placed in ampoules or vials
based on dilution, mE, or as concentration/percentage.
Adrenaline 1000:1, Lidocaine 1% and Na bicarbonate
solution 8.4% which are among the main drugs in
medical emergencies and in critical situations such as
cardio-pulmonary resuscitation or in ICU, are some
examples [3]. Usually these drugs are prepared by
nurses and are presented to patients. The importance
of the accuracy in calculation of these drugs and
similar drugs is so high. The different impact of drugs
in different doses and their potential dangers and
irretrievable side effects have led to taking some
measures for reduction of computational errors. Due to
the necessity of preparation of nurses as the first care
and treatment forces who are faced with critical
situations and the importance of accurate and correct
application of drugs in shortest time, this study was
conducted to determine the calculation error in soluble
drugs used in intensive units.
Methods
The studied population in this descriptive study was
nurses working in intensive care units of hospitals
affiliated to Mazandaran University of Medical
Sciences. 36 people were randomly selected and
completed a researcher made questionnaire. The
questionnaire contained demographic items and five
questions about the three drugs used in critical cases
of cardio-pulmonary resuscitation at intensive care
units, which are used in various forms of
Received 2009/01/15; Accepted 2010/02/13
Nurses' drug calculation ability in intensive care unit (ICU)________________________________________________________________
concentration/percentage and mE (epinephrine,
lidocaine and sodium bicarbonate). The validity of this
questionnaire was confirmed based on previous
resources and information and obtaining experts’
opinion in terms of content and its reliability was
accepted after conducting an experimental study on
five nurses for two weeks with a retest and correlation
coefficient above 0.8. Data collection was done by
face-to-face method. Responses were evaluated in
three levels of “weak and disabled” (less than one or
one correct answer), “moderate” (two or three correct
answers) and “good” (four or five correct answers).
The answer to each question was considered as correct
or incorrect. Chi square analysis was used to
investigate the relationship between variables.
Results
83% of subjects were female and 17% were male.
Their average work experience was 7 years (minimum
1 and maximum 14 years). All the studied samples had
encountered patients who needed cardio-pulmonary
resuscitation at least one and maximum more than 20
times, and this research’s studied drugs had been used
for them.
Table 1- Frequenct distribution of nurses’ encountering the
number of very-sick patients who needed studied drugs.
Encountering
Number Percentage
number
1-9
16
%44
10-19
10
%33
10
%33
Table 2- Frequency distribution of response status related to
medications’ calculation by ICU nurses
Calculation status
Number Percentage Conclusion
0
0
Disable
Without correct answer
8
22
Weak
Only one correct answer
20
55.5
Moderate
Two or more correct answers
Four or more correct
8
22
Good
answers
The majority of intensive care units’ nurses are
“medium” in calculation of drugs rate (55.5%) and
22% of them were weak and had many errors in drug
calculation. In addition, there were no significant
difference between working experience and the ability
of pharmaceutical calculation. 100% of critical care
unit nurses had at least one error in pharmaceutical
calculation in their history. Tables 1 to 3 show the
results.
Table 3- Frequency of response to drug calculation by ICU nurses
by exclusive questions
Correct
Incorrect
Exclusive questions
Percentage
Percentage
cases
cases
How much(mg)
adrenaline is in in 4
8
22
28
78
ml 1:1000 solution?
How much (mg)
lidocaine is in 10 ml
36
100
0
0
1% lidocaine ?
How much (m mol)
sodium bicarbonate
2
6
34
94
is in 100 ml 8.4%
solution?
How much (mg)
adrenaline is in 10
ml vial of
12
33
24
67
bupivacaine 0.25%
with concentration
of 1:20000?
How much (ml) of
1:10000 solution is
needed for getting
26
72
10
28
one mg of
adrenaline?
Discussion & Conclusion
With regard to variety and difference in patients’
weight, sex and environmental sensitivities governing
ICU and multiple crises at intensive care units, results
show that the dose calculation ability for drugs
diluted in ampoules or drugs which are prepared in
concentration/percentage (indeed are not adjusted and
prepare based on milligrams/micro grams) have been
“moderate” or “weak”. According to results, more
than 77% of nurses are in “moderate” or “weak” status
in medication dose calculation. In such condition,
injection of incorrect doses of drugs, in performing of
treatment and care procedures like resuscitation and
other urgent conditions, causes disorder in treatment
process and consequences that are even more
hazardous. Santamaria et al. reported that 58% of
nurses could not calculate the correct dose of
medications [2]. Also, Bindler et al. reported
concordant results with present study. They reported
that 81% of nurses are not able to calculate drugs
correctly [6]. Certain drugs are of high importance in
critical conditions and some drugs such as epinephrine
and nitroglycerin have high impacts with low doses,
and there is trivial difference between the minimum
and maximum dose of drugs such as dopamine.
Therefore, there is no possibility of numerous errors
for nurses and the stress caused by responsibility can
cause increase in medication calculation errors. The
usual methods of dose calculation, which are done in
milligrams or micrograms per kilograms of patients’
__________________________________________________________________________________________________ Nasiri E. et al.
weight, lead to lower percentage of errors. Similar to
other studies, this study shows that certain forms of
soluble drugs, which are in concentration/percentage
or mE, reduce the calculating ability of nurses to
“medium” and causes a plenty of errors. Therefore, the
necessary in-service instructions should be presented
to all nurses in field of dose calculation and more
attention should be paid to this issue in nursing
education; and if possible, pharmaceutical companies
should consider more obvious units for soluble drugs
that are in form of ampoules or vials, so that they
wouldn’t be ambiguous or confusing.
Reference
1- Coomber S, Todd C, Park G, Baxer P, Firth-Cozens J, Shore S.
Street in UK intensive care unit doctors. Br J Anaesthesia.
2002;89(6):873-81.
2- Santamaria N, Norris H, Claton L, Scott D. Drug calculation
competencies of graduate nurses. Collegian Gul. 1997;4(3):18-21.
3- Flaatten H, Hevroy O. Errors in the intensive care unit (ICU).
Acta Anaesthesiologica. 1999;43(6):614-16.
4- Sarah B, Vittone RN. Ethics in the ICU. Crit Care Nurs Clin N
Am. 2002;14:157-63.
5- Cartwright M. Numberacy needs of the beginning registered
nurse. Nurse Educ Today. 2002;16(2):137-43.
6- Bindler R, Bayne T. Medication calculation ability of registered
nurses. Image J Nurs. 1999;23(4):221-4.