The Infusion Problem Defined...

You may well be aware that gravity infusion sets are unreliable, inaccurate, unsafe and generally a major management problem.

Have you ever asked yourself:

Just why is it inaccurate?

Why do pre-calibrated, “dial-type” infusion sets not deliver the correct flow rate?

Why is it not safe to use and why is it not more reliable?

Why is it so difficult to calibrate and recalibrate these devices?

Why are all the complications and problems accepted as standard practice across the world?

The three main reasons are:

An ever-changing hydrostatic pressure;
Inability to shut down once the container runs empty; and
The inaccurate and complicated method of calibrating the flow rate.

1. An ever-changing hydrostatic pressure

All gravity sets have an inherent deficiency. Relying solely on gravity as the driving force to administer fluids, they do not compensate for changing hydrostatic pressure. This built-in deficiency causes a 35% change in set flow rates.

Are flow rates critical when maintenance fluids are administered?

Flow rate accuracy of intravenous infusion therapy is a prerequisite for administration of parenteral fluids to a hospitalised patient. The intention of the prescribing physician is for his/her patient to receive the fluids as per script for specific clinical indications. The body has a powerful defense against water deficit, but very little against water excess. An increase in serum sodium concentration of 4-5 mmol/l above the usual normal value is a powerful stimulus for thirst. A conscious patient will demand or drink water until the thirst subsides. On the other hand, hyponatremia does not create feelings of aversion to water. In other words, insufficiency of water intake will not remain uncorrected in a conscious patient, whereas no effective defense mechanism exists to prevent hyponatremia and fluid overload.

Fluid overload can lead to pulmonary congestion and hyponatremia, the most common electrolyte abnormality in hospitalised patients. If the plasma sodium concentration declines to less than 120 mmol/liter in 48 hours, brain swelling might result in herniation, with devastating consequences.

Who needs to cater for this flow rate deficiency?

Clinicians and overworked nursing staff at hospitals must take full responsibility in order to ensure correct flow rate and compensate for the built-in deficiencies of current technology.

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2. Inability to shut down once the container runs empty

To make matters worse, most gravity sets do not compensate for an infusion bag or bottle that will run empty.

A recent study showed that 53% of patients experienced an adverse event as a result of the above-mentioned (unplanned occurrence that impact on patient care or nursing time) of which:

  • 45% of these were as a direct result of air in line,
  • 50% of these were as a direct result of reverse back flow of blood.

In extreme cases, the air in the line can even cause an embolism that may result in the death of a patient.

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3. The inaccurate and complicated method of calibrating the flow rate

Drip chambers are calibrated as drops per milliliter (drops/ml) and the clinician’s scripts are prescribed as milliliter per hour (ml/hr). This conflicting method of calibration is clearly a major management problem for nursing staff and therefore correct calibration is no simple procedure.

Consequently, a clinical practice is implemented by nursing staff whereby they estimate the correct flow rate by merely glancing at the drip chamber and estimating the flow rate in order to calibrate the device.

According to a recent study, 125 ml per hour prescriptions represents 87% of infusion prescriptions in a standard hospital setup.

Actual flow rates vary from a minimum of 23 ml to a maximum of 500 ml per hour from such a prescribed flow rate. The median is 88 ml per hour (a 30% deviation from the pre-scribed flow rate of 125 milliliter per hour).

Only 7% of patients achieve a level of accuracy of 5% from the prescribed flow rate and if the acceptable deviation was hypothetically expanded to 10%, only 12% of patients are infused at an acceptable rate.

It is clear that under-infusion (72% of patients) is the norm with over-infusion occurring in 22% of the cases.

Quote from Fraser, N et al Data on File (Varori).

“This observational study proves that the current management of gravitational intravenous infusions sets impacts negatively on patient care, prescribed treatment, nursing time and cost containment.

The clinically significant variation in the actual versus prescribed flow rates (primary outcome) indicates that the current situation is scientifically incorrect and medically unacceptable.

The negative impact on quality of patient care is further exacerbated by the high incidence rate of unintended events; 53% of subjects in this study experienced one or more adverse events.

From a pharmaco-economic viewpoint, the financial relevance of this study is reflected in the wastage of R25.19 (approximately US$ 3.98) per patient per 24-hours infused. Extrapolated to the millions of hours infused per annum, this is an unexplored cost containment measure not to be underestimated.”

* All clinical studies and statistics have either been conducted or quality assured by Quintiles

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