Clinical Perspectives: The Need for Innovation in Infusion Pump Fluid Delivery

Pumping Up Pump Performance:
The Need for Innovation in Infusion Pump Fluid Delivery

 As clinicians, we’ve heard it all before—the importance of compliance in smart pump drug library utilization, the need for EMR integration and benefits of bar code medication administration with large volume infusion pumps. But what about the most basic aspect of technology common across all infusion systems—the pumping technology itself?

The majority of today’s large volume infusion pumps use linear peristaltic technology to deliver fluids to patients. This technology has inherent shortcomings, which will be detailed further below. With these shortcomings, pumps have the potential to not only hamper patient care, but also bring potential harm to patients. To enhance patient safety, innovation is needed to develop more sophisticated pump technology that is capable of delivering fluids accurately and consistently.

Case in point: During a busy shift on a post-op surgical unit, a heparin infusion was started on an elderly patient for deep vein thrombosis. Two registered nurses meticulously double checked the order and the patient’s recent blood work. Together, they programmed the “smart” infusion pump with dose error reduction software within the appropriate limits.¹

Thirty minutes later, the heparin bag was almost empty. No alarms had sounded. No spill was evident. The infusion was still continuing at the programmed rate. Once discovered, the infusion was stopped immediately, the patient was assessed, the physician called to treat the life-threatening overdose.

How did this happen? Every protocol was followed, yet the patient’s life was in jeopardy. How smart is a pump that doesn’t know it is delivering medication in a potentially lethal dose?

The Problem of Uncontrolled Flow

It is important to understand the mechanics of infusion flow and how this impacts the pump technology that is available with the majority of large volume infusion pumps.

Anyone who examines the FDA MAUDE or MEDSUN database on large volume infusion pump malfunctions will find that an empty bag and uncontrolled flow is not uncommon.²  Almost daily such incidents are reported involving pumps from market-leading vendors to start-ups. Little of today’s ever-expanding healthcare innovation has focused on the infusion pump, particularly on the mechanics of large volume pumps and their linear peristaltic pump platforms. Why does infusion pump technology seem to lag so far behind when patients’ lives hang in the balance?

Understanding Pump Mechanics

An understanding of pump mechanics is crucial to appreciate the problem of potential infusion pump uncontrolled fluid flow. Today, the majority of infusion pumps rely on compression of the administration set to move fluid along its pathway. In fact, the same linear pathway that makes the tubing easy to prime and function as a gravity drip also poses a significant risk of uncontrolled flow.

Most large volume infusion pumps move fluid through linear peristalsis with synchronized finger compression, followed by release to the tubing set. Healthcare professionals know the concept: think of food moving through the GI tract. The peristalsis is virtually the same. Most, but not all, pumps rely on a calibrated administration set specific to the pump that is inserted into the device housing.

The design of these pumps inherently accounts for its failures. Linear peristaltic infusion pumps rely on continuous occlusion along their straight pathways to deliver fluids and prevent inadvertent flow. The pump is only capable of indirectly measuring flow by monitoring the gears and cams that control the peristaltic finger pressure involved along the fluid pathway. From this, it infers the infusion rate and flow accuracy.

However, most pumps are not aware whether these mechanics are working effectively or of the quality of compression that results. Therefore, the pump has no way of truly assessing what volume of fluid was actually delivered to the patient and correcting any inaccuracies.

In particular, the pump may not recognize when either a gear or finger fails, when tubing is misaligned or when inadequate pressure is applied to the tubing segment. The most disastrous outcome is insufficient compression resulting in deficient tubing resistance, allowing the fluid to flow uncontrollably into the patient. Adding to the problem, in some devices, insufficient compression causes the tubing set to become permanently deformed, setting off occlusion alarms. In this case, the only remedy is to change out the administration set.

However, when infusion pump mechanics fail, pumps will not always alarm to notify the clinician about the risk of over- or under-infusion. As noted by medtech watchdog ECRI, current infusion technology continues to require the clinician to inspect the infusion pumps for damage as the ultimate safeguard to prevent free flow from roller clamp malfunction as well as to monitor the drip chamber for appropriate flow.³ Additionally, infusion pumps need to be taken out of service as frequently as every six to twelve months for preventative maintenance and calibration to ensure proper function of these mechanisms.

User Beware

Many clinicians falsely assume pumps are delivering fluid accurately, especially at lower flow rates, when precision is most critical. Ask the NICU nurse whose vulnerable patients require extremely precise dosing. They generally will only use a syringe pump, rather than a large volume pump even when an administration set with low contained volume is available. Large volume pumps erroneously get credit for accuracy because fluid delivery is averaged over time. These pumps can remain idle for long time periods and then compensate by delivering a micro bolus of fluid, putting the patient at significant risk.

Another challenge with current pumping technology is that it still relies on clinicians to understand the physics of fluid delivery. In particular, they must recognize that bag height can compromise flow accuracy. For secondary fluid delivery, clinicians must remember to drop the primary bag and place the secondary bag sufficiently above it. Further, they cannot forget to release the clamp on the secondary line so that the pump will be able to sense an occlusion and deliver from the secondary bag.

Sensors Should make Sense

Current pumping technology is equipped with sensors that assess administration set pressure build up due to an occlusion or degrading IV access due to a clot or other blockage. However, the infusion system cannot act on this information, and it is only conveyed to the clinician when a designated occlusion pressure threshold triggers an alarm. The thresholds are set high to diminish the frequency of alarms. Therefore, the problem often is not addressed until it becomes critical with long periods of no flow and could result in a delivery of a micro bolus.

Many clinicians also are under the impression that the infusion pump can successfully detect most IV infiltrations and they do not. However, typically an infusion must be underway for some time before sensors will detect a pressure build up in the interstitial space surrounding an infiltrated IV— if it is detected at all—and trigger an alarm. Notably, occlusion pressure thresholds typically are set arbitrarily high, especially in critical care areas, to decrease nuisance alarms. No studies have documented as to why they really need to be so high, and what harm can come to the patient as a result.

Just the Beginning

As anyone who has even occasional experience with infusion pumps knows—and that would be most people in healthcare—the devices are rife with problems. Pump mechanical issues are just the beginning. Today, infusion pumps lack innovation in management of common alarms for occlusion pressure sensing and air-in-line. Pump user interfaces call for human factor design to assist in prevention of programming errors and issues managing head height dependence for piggyback infusions. Retrofitting of legacy hardware with new IT technologies such as bar code scanning, RTLS and EHR integration results in other shortcomings.

As other healthcare technologies advance, the industry is beginning to take notice. Meaningful innovations in infusion pumps are beginning to emerge. So, let’s not take these problems for granted. Pump pain points don’t have to be a way of life. Let’s all push to elevate infusion pump safety and the performance of the infusion pump.

The Fresenius Kabi Team

References:

(1) https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/Medsun/medsun_details.cfm?id=52988

Noted Data from the FDA’s Medical Product Safety Network (MedSun) that is cited in the MAUDE database.

(2) https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/search.cfm and https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/Medsun/searchReportText.cfm 

(3) ECRI Institute.Executive (Nov 2016) Brief: Top 10 Health Technology Hazards for 2017. A report for health devices, Nov 2016- See more at: https://www.ecri.org/Resources/Whitepapers_and_reports/Haz17.pdf