Use Of Extension Sets With Smiths Medical Infusion Pumps

April 09, 2020

In line with recent FDA thinking regarding COVID-19, Smiths Medical is providing the following information about adding extension sets to infusion pump tubing to create length allowing the pumps to be placed outside patients’ rooms. This is a clinical decision that should consider the practice implications described by the Infusion Nurses Society (INS), Institute for Safe Medication Practices (ISMP) and Emergency Care Research Institute (ECRI) in the links below.


Additionally, Smiths Medical has published the “Factors to Consider When Selecting Infusion Disposables..” In general, there are many parameters that affect the accuracy of delivery of an infusion pump. This would include the viscosity of the drug, the height of the pump compared to the patient, the gauge and length of the vascular access device, the drug reservoir (syringe size and brand, bag, etc.), and the characteristics of the tubing between the pump and patient including, but not limited to, tubing bore, length, filters, and backcheck valves. These factors may also impact the functionality of the pump’s internal time to occlusion alarm performance. This information should be considered along with the attached information to consider when deciding to add length to pump tubing.

Mathematical modeling data demonstrating the use of micro- and small-bore extensions sets with our delivery sets has been conducted for the Medfusion® 3500 and 4000 pumps with minimal degradation on accuracy, performance, and minimal nuisance alarms. Refer to the “Medfusion® Back Pressure Calculation Table” provided with this letter for further details. These statements have not been evaluated by the FDA.

CADD® pumps are designed to be used with a single extension set or a single administration set. There are several CADD® administration sets that are over 10 feet long that may be suitable for locating the pump outside the room. Use with longer length extension sets such as MX20194 (20' x .046" ID) will increase back pressure by 50 mmHg at 150 mL/hr flowrate, which may impact delivery accuracy. When connecting multiple pumps to the same patient line, back pressure will increase further. Carefully monitor delivery under these circumstances and consider raising the pump or increasing flow rate to compensate.

Please contact your local Smiths Medical account manager or customer service representative with any additional questions. You may also visit Customer Services to leave a question and one of our customer service representatives will respond to you directly.

Extended Administration Set Potential Impacts

Clinical Implications and Considerations


Reference


Extended tubing impact on the back pressure of the line
Depending on the number and size of extension sets used, the back pressure of the line can be increased by 10x.
The back-pressure calculations can be used to determine the necessary occlusion alarm settings for the Medfusion® 4000 pump when using extended sets. At normal or low-pressure settings, the Medfusion® pump will operate with minimal nuisance alarms.
Medfusion® Back Pressure Calculation Table
Back pressure impact on occlusion alarm settings for the Medfusion® 4000 pump
The table in the Medfusion® operator’s manual, also shown below, correlates the occlusion alarm settings to the pressures they detect.
Medfusion® Operator’s Manual Occlusion Alarm Table
Back pressure impact on the accuracy of the Medfusion® pump
The Medfusion® pump has a published accuracy of +/- 2% (not including syringe variation) at infusion back pressures of -100 mmHg to +300 mmHg. Per the predicted downstream back pressure calculations, the pump will maintain +/-2% accuracy with extended sets when placed at or above the infusion site.
Medfusion® Back Pressure Calculation Table
Back pressure impact on the accuracy of the CADD® pump
Backpressure increase of 100 mmHg (generated for example by placing the pump four feet below the infusion site) will result in -10% to 5% delivery accuracy.
CADD® HPCA 4.2 Operators Manual
Extended set impact on titratable drips on the Medfusion® pump
There should not be any noticeable change to Medfusion performance with regards to titration. Rate changes and bolus changes should be seen within seconds of programming at the infusion site. Any delay would be due to the normal stiction that needs to be overcome in syringes.
 
Increased priming volume impact on infusions
Increased priming volume at the beginning and end of an infusion will require careful determination and administration of flush volumes.
ECRI- Considerations When Used with
Long Extension Sets outside Patient Rooms to Help Reduce Staff PPE Use
Extended set availability
Smiths Medical manufactures a variety of longer length extension sets up to 240 inches and can be found in our Infusion Disposable Catalog. Availability may be limited due to current surge in demand.
Infusion Disposable Catalog

 

Medfusion® Back Pressure Calculation Table


The Medfusion® pump has a published accuracy of +/- 2% (not including syringe variation) at infusion back pressures of -100 mmHg to +300 mmHg. Per the predicted downstream back pressure calculations, the pump will maintain +/-2% accuracy with extended sets when placed at or above the infusion site based on the modeled data.

All calculations are done on a Medfusion® pump with Saline in a 60 mL syringe delivered intravenously through a Jelco® 20G peripheral intravenous catheter (PIVC).
The following Smiths Medical extension sets are referenced in the table below:

  • MX20194 – Small Bore Extension with Pinch Clamp, Male Leur Lock - 240" (609 cm) APV 6.5 mL
  • MX448 – Small Bore Extension with Removable Slide Clamp, Male Luer Lock
  • 536040 – Micro Bore Extension with Male Luer Lock, APV 0.3 mL, 61" (155 cm)

 

Infusion Set used with (1) 60 mL syringe
Set Length (in)
Pump Height r/t Patient (in)
Physio-logic Pressure (mm Hg)
Fluid Flow Rate (mL/hr)
Catheter Back Pressure (mm Hg)
Total Predicted* Downstream Back Pressure (mm Hg)
20 Feet Prime Vol (mL)
1x MX20194
Small bore
240.00 36.00 3 1 0.02 -64.3  6.5
1x MX20194
240.00 0 7 5 0.09 7.2 6.5
1x MX20194
240.00
-36.00  15 10 0.18 82.8 6.5
10x MX448
Small bore
236.00 36.00 7 1 0.02 -58.9 2.7
10x MX448
236.00 -36.00 7 5 0.09 81.4 2.7
4x 536040
Micro Bore
244.00 36.00 15 1 10.82 -10.9 0.7

 

*Note predicted back pressure will differ based on combination of components including: Flow rate, vascular access device gauge, infusion extension set bore and length, and position of pump in relation to patient. Micro Bore tubing creates high back pressure than small or standard bore tubing.

 

Medfusion Model 4000 pump

Operation Model

Occlusion Alarm

For 1 mL Syringes, the occlusion limit is fixed at Very High.

Very High (1 mL syringe only, selectable): 50 psi (2585 mmHg) (345 pKa)

For Syringes with a volume greater than 1 mL, the user can set the occlusion limit for Very Low to High.

High:        16 psi (827 mmHg) (110 kPa)

Normal:    12 psi (621 mmHg) (83 kPa)

Low:          8 psi (413 mmHg) (55kPa)

Very Low:  4 psi (206 mmHg) (28 kPa)