Comparison of a metronome-guided prehospital medication infusion technique with manual calculation: a simulated randomized, controlled, cross-over study


 BackgroundLimited research regarding administration of timed medication infusions in the prehospital environment has identified wide variability with accuracy, timing, and overall feasibility. This study was a pragmatic, randomized, controlled, crossover study comparing two different techniques for medication infusion administration. We hypothesized that the use of a metronome-based technique would decrease medication dosage errors and reduce time to administration for intravenous medication infusions. Methods Forty-two nationally registered paramedics were randomized to either a metronome-based technique versus a standard stopwatch-based technique. Each subject served as a control. Subjects were asked to establish an infusion of amiodarone at a dose of 150 mg administered over 10 minutes, simulating treatment of a hemodynamically stable patient with sustained monomorphic ventricular tachycardia. Descriptive statistics and multiple linear regression were used for data analysis. Results When compared to a standard stopwatch-based technique, a metronome-based technique was associated with faster time to goal, fewer mid-infusion adjustments, and greater ease of use. Conclusions Use of a metronome technique for establishing medication infusion rates may help prehospital clinicians provide safer and more precise medication delivery.


ABSTRACT Background
Limited research regarding administration of timed medication infusions in the prehospital environment has identified wide variability with accuracy, timing, and overall feasibility. This study was a pragmatic, randomized, controlled, crossover study comparing two different techniques for medication infusion administration. We hypothesized that the use of a metronome-based technique would decrease medication dosage errors and reduce time to administration for intravenous medication infusions.

Methods
Forty-two nationally registered paramedics were randomized to either a metronome-based technique versus a standard stopwatch-based technique.
Each subject served as a control. Subjects were asked to establish an infusion of amiodarone at a dose of 150 mg administered over 10 minutes, simulating treatment of a hemodynamically stable patient with sustained monomorphic ventricular tachycardia. Descriptive statistics and multiple linear regression were used for data analysis.

Results
When compared to a standard stopwatch-based technique, a metronome-based technique was associated with faster time to goal, fewer mid-infusion adjustments, and greater ease of use.

Conclusions
Use of a metronome technique for establishing medication infusion rates may help prehospital clinicians provide safer and more precise medication delivery.

Consent for Publication
Not applicable.

Availability of Data and Materials
The datasets generated and/or analysed during the current study are located in the METRONOMEEMS repository persistent web link to datasets: https://www.dropbox.com/s/3uz6rh4xz70p56z/metronome_data.dta?dl=0.

Competing Interests
Dr. Galvagno reports personal fees from Northwest Anesthesia Seminars, grants from the Department of Defense, and is an employee of the United States Air Force Reserve.
However, nothing in this work is related to this employment. The views expressed are those of the author and do not reflect the views of the US Air Force, the Department of Defense, or US Government.
The remaining authors have no competing interests to disclose.

Funding
No funding was required for this study. Materials used were donated by the Anne Arundel County Fire Department (expired materials). This work was not funded by an external agency.

Authors' Contributions
SMG conceived the study design, performed data collection, completed all data analysis and interpretation, and drafted the article.
JW conceived the study design, performed data collection, and critically revised the article.
JC, JH, AN and KSR conceived the study design, performed data collection, and critically revised the article.

Delivery of intravenous (IV) infusions of fluid and medications is a challenging but
foundational skill for prehospital clinicians. 1 An infusion pump is preferred to ensure appropriate dosing, but such devices are expensive, require extensive training, and are not available in many EMS systems. Even when using intravenous infusion flow regulators, deviations from expected infusion volumes are common and potentially harmful. 2,3 Conventional calculation of prehospital IV infusion rates requires a mathematical computation based on the medication dose, delivery interval, and number of drops in the IV administration set per volume. Thus, a method to mitigate the difficulty and potential for error when administering prehospital IV infusions could assist EMS clinicians by facilitating accurate infusion control.
As the scope of prehospital medicine continues to evolve, the ability to quickly and safely administer IV medication infusions will remain an essential skill to enhance patient outcomes. For example, in patients with refractory ventricular fibrillation, early administration of amiodarone has been associated with improved neurological outcomes for some out-of-hospital cardiac arrest (OHCA) patients. 5,6 The objective of this study was to assess the effectiveness, accuracy, and ease of use of a metronome-guided IV medication infusion technique. We hypothesized that when compared to conventional prehospital IV medication infusion techniques, the metronome technique would be associated with fewer errors and decreased time to target infusion rate.

Methods
Nationally registered paramedics (NRP) from Anne Arundel County Fire Department, Maryland, USA, served as subjects during this study. This study was deemed exempt from institutional review board oversight (HP-00096185) at the University of Maryland School of Medicine since the aim of this research was to test the simulated effectiveness of an instructional technique for calculating medication infusion rates in a prehospital environment. The study was conducted in a stationary ambulance, where participants were asked to correctly establish an intravenous infusion rate using one of two techniques. Using a random number generator, subjects were initially randomized to either a "standard" group using micro drippers and a calculation or a "metronome" group using an audible cadence to establish the correct medication infusion rate. Each subject served as her or his own control; the order of medication infusion rate performance was reversed after the initial assigned technique was complete. Primary outcomes of interest included time to target infusion rate (from start to finish), time to goal medication infusion rate, and total elapsed time. Ease of use was evaluated with a 5-point Likert scale with a value of "1" indicating most difficult and "5" indicating easiest.
Subjects were asked to establish an infusion of amiodarone at a dose of 150 mg administered over 10 minutes, simulating treatment of a hemodynamically stable patient with sustained monomorphic ventricular tachycardia. Multiple IV administration sets (15-, 20-, and 60 drips/mL) were used to simulate restocking from different receiving hospitals. The amiodarone vial (3 mL) was injected into a 100 mL IV bag of 5% dextrose in water. Subjects were required to use the following formula to establish the correct infusion rate (drops):

Volume (mL) / Minutes x Infusion Set Drip Factor (drops/mL) = Flow Rate (drops/min) Formula 1. Intravenous infusion set calculation.
For example, using a volume of 103 mL of amiodarone, at 20 drips/mL, the flow rate for a 10-minute infusion was 206 gtts/min. Once the flow rate was calculated, subjects were instructed to establish an infusion of amiodarone using either the standard or metronome technique according to the randomization scheme. For the standard technique, a watch was used to synchronize the drops/min. In the metronome group, a Quik Time ® metronome (John Hornby Skews & Co., Leeds, UK) was used.
Depending on the drips/min per the infusion set used, the metronome cadence was adjusted to match the desired flow rate.
Descriptive statistics and multiple linear regression (with appropriate regression diagnostics) were used for data analysis. Using a one-way ANOVA to detect a statistically significant difference of 2 minutes between techniques, at an alpha of 5% and with 80% power, a total of 12 participants were required in each group. All tests were two-tailed and a P value of < 0.005 was considered statistically significant. 7 Analyses were performed in Stata version 15 (Stata Corp, College Station, TX) and GraphPad Prism 7.0d (GraphPad Software, La Jolla, CA).
The mean number of years each subject had worked as an NRP was 10.4 (6.7). Twelve (14.6%) NRPs had prior experience working for critical care transport organizations, none were registered nurses, and two (2.4%) were physician's assistants.
In the standard group, adjustments to the drip rate were required 63% of the time; in the metronome groups, adjustments were required in 34.4% (P=0.14). Infusions were  When controlling for total years of experience and critical care transport experience with multiple linear regression, time to goal infusion rate was significantly faster in the metronome group (mean of 13 second faster; 95% confidence interval, 22-7 seconds; P < 0.001). Ease of use was reported to be significantly higher for the metronome group (median ranking 5, IQR 4-5) compared to the standard group (median ranking 2, IQR 2-3; P < 0.001) (Figure 3).

Discussion
Administration of intravenous medication infusions in the prehospital arena is an arduous task. Even when using intravenous infusion flow regulators, significant deviations from volume and flow rates are possible, leading to potential medical delivery errors. 2 When delivering fluid volumes alone, accuracy may be highly variable. 4 In this randomized, cross over study, use of a metronome was associated with greater ease of use and shorter time to goal infusion rate.
The results of this study have significant implications for prehospital clinicians.
Infusions of lidocaine and amiodarone may be associated with clinically relevant outcomes, and proper dosing is essential. In one large randomized double-blind study, 8 both of these agents have been associated with improved survival to hospital admission, 6 and amiodarone has been shown to be moderately effective for the treatment of sustained ventricular tachycardia. 5 Amiodarone is also associated with improved neurological outcome at hospital discharge for out-of-hospital cardiac arrest in patients who had ventricular fibrillation as the presenting dysrhythmia. 9 The prehospital literature is largely devoid of data describing safe and efficient practices for medication infusion delivery. Park et al. compared four methods of infusion control in a cohort of emergency medicine nurses, highlighting the inaccuracy of dial flow controllers and supporting the use of an "intravenous infusion therapy helper" based on a metronome and drop counter. 10 A phone application with a metronome-like flow rate control function was used control the volume of a fluid infusion. Compared to a stopwatch technique, the volume of fluid was more precise with the metronome-based technique, although an additional control was added using a control function within the application to add additional precision. The outcome of interest in this study was fluid volume, not medication dosing. In our study, use of an off-the-shelf metronome demonstrated superior effectiveness and ease of use. Metronome applications for smartphones are prevalent, free, and can be used in the field to adjust medication flow rates. Such techniques could prove useful for EMS jurisdictions administering infusions that require timing, such as amiodarone, lidocaine, magnesium, epinephrine, and others.
There are a number of limitations to our work. The crossover nature of this study may have introduced confounding due to carryover between technique assignments since the metronome technique might have helped the participants remember a correct drip cadence. Although the metronome group had a lower overall number of premature infusion completions, compared to the standard technique, this difference was not statistically significantly different, likely due to the sample size. Although randomized and administered in a simulated prehospital setting, this study did not involve actual patients and only one medication infusion was assessed. It is possible that other medication infusions may be subject to a greater or lesser degree of error.

Conclusion
Precise control of prehospital medication infusions is required to prevent harm and maximize therapeutic effectiveness. As many EMS jurisdictions across the world do not have access to electronic infusion pumps, novel techniques are required for training and clinical practice. In this study, the use of a metronome technique was associated with faster time to goal infusion rate and greater ease of use compared to standard techniques.