Is the i.v. obstructed or infiltrated? A simple clinical test

Area of Science:

• Medical Devices
• Clinical Engineering
• Fluid Dynamics

Background:

• Gravity-fed intravenous (IV) infusions are common but can malfunction.
• Poor infusion performance can result from external obstruction or cannula infiltration.
• Differentiating the cause is crucial for timely intervention and patient safety.

Purpose of the Study:

• To evaluate the utility of pressure-flow relationships (PFR) in distinguishing between partial external obstruction and infiltration.
• To assess if PFR analysis can identify the cause of malfunctioning gravity-fed IV infusions.

Main Methods:

• Simulated obstruction using tourniquets and infiltration in patients with IV cannulae.
• Measured changes in flow rate (delta F) for discrete changes in pressure (delta P) at different fluid reservoir elevations.
• Assessed the impact of blood pressure cuff inflation on flow rates for different cannula sizes (16, 18, 20 gauge).

Main Results:

• Statistically significant differences in PFR were observed between obstructed and infiltrated cannulae.
• Mean venous resistance (23 mm Hg/L/hr) differed significantly from tissue resistance (280 mm Hg/L/hr), with no overlap.
• Blood pressure cuff inflation reduced flow in obstructed cases but had no effect in infiltrated cases.

Conclusions:

• Clinical observation of PFR is a valuable tool for diagnosing infiltration in poorly functioning IV infusions.
• The blood pressure cuff inflation test can further differentiate between intravascular obstruction and extravascular infiltration.
• These methods can improve the accuracy and speed of diagnosing infusion problems.