Occlusion tests


Some facts:

The Medicines and Healthcare products Regulatory Agency receives more incident reports on infusion devices than any other electronic medical device.  Infusion devices are the cause of more injuries to patients than any other electronic medical device (when not used correctly).


The risk of tissue injury to patients is higher if:

  • The wrong infusion device is used.
  • The device is incorrectly set up.
  • Staff do not receive adequate training. (Staff need to understand the clinical risk to appreciate the reasons why we would set different occlusion pressures for different areas)
  • The occlusion pressure sensor is out of calibration.


The use of the intravenous (IV) route for administration of fluids and medications always carries with it the risk of tissue damage following catheter malfunction. Extravasation, or infiltration, occurs when fluids or medications penetrate into the tissues surrounding an IV site following damage to the vessel endothelium.

Infusion Pump

The incidence of extravasations varies but is believed to range from 10% to 30% of patients receiving IV therapy.
Most extravasations have relatively minor sequela (after effects), but severe tissue injuries requiring surgical debridement (removal of dead tissue), tissue grafting, or amputation have been reported.




Risk Factors

There is little information available on methods for identifying patients at risk for extravasations.

Age is considered to be the most significant risk factor.

Infants and young children are known to have more extravasations, possibly due to their need for smaller catheters and their inability to communicate pain at the IV site as an early warning sign.


The elderly are also at risk. Other factors associated with extravasations include: increasing cannula gauge (smaller size), use of steel needles, darker skin which makes assessment difficult, and infusion of substances known to cause direct cell damage.


Reducing Risk

Using competency-based training for staff can reduce the risk of extravasation.  This should include training on using infusion devices and making them aware of how to set up variable occlusion pressures (where available)

  • Where the occlusion pressure can only be set by the EBME / Medical Physics technologist, the clinician should be consulted before pressures are set.  Ideally, pressures should be set individually for every patient.   Where this is not possible, occlusion pressures may be set to a 'general' pressure (in accordance with clinicians requirements).

If there is a tissue injury this may help to reduce the severity of injury caused to the patient.


Extravasation Hazards

All intravenous medications and fluids can cause tissue injury following Extravasation. However, certain substances are associated with a greater risk of tissue necrosis. Hyperosmolar substances, such as parenteral nutrition solutions, cause tissue damage by altering osmotic pressure.  Nearly all cancer chemotherapeutic agents have been reported to cause local tissue injury after extravasation. These agents cause direct cellular toxicity in the tissues they penetrate. Among this class, there are several agents (Table 1) which are considered to have a greater potential for causing substantial tissue necrosis.


Table 1.

Chemotherapeutic agents with a high potential for local tissue injury

  • Actinomycin D
  • Amsacrine
  • Dactinomycin
  • Daunorubicin
  • Doxorubicin
  • Epirubicin
  • Idarubicin
  • Mithramycin
  • Mitomycin
  • Vinblastine
  • Vincristine
  • Vindesine
  • Vinorelbine


Table 2 lists other medications associated with significant tissue injury.  The mechanisms involved vary. Acyclovir, phenytoin, and sodium thiopental are highly alkaline. Phenytoin and other medications such as diazepam have propylene glycol or ethyl alcohol diluents that can precipitate in local tissue, resulting in necrosis.


Table 2.

Examples of other IV medications associated with significant tissue damage

  • Acyclovir
  • Aminophylline
  • Calcium
  • Chlordiazepoxide
  • Diazepam
  • Digoxin
  • Dobutamine
  • Dopamine
  • Epinephrine
  • Mannitol
  • Nafcillin
  • Norepinephrine
  • Penicillin
  • Phenytoin
  • Potassium
  • Sodium thiopental
  • Vancomycin


Initial Management

Early intervention following extravasation can lessen the severity of tissue injury. The first steps after discovery of an infiltrated IV line are to discontinue the infusion and thoroughly examine the site. If the catheter appears to be lodged in the tissues, an attempt to aspirate any fluid remaining in the catheter can be made to lessen the amount of drug at the site.

Patient management often includes measures such as elevation of the site and the application of warm (dry) or cold compresses.   Despite their widespread use, documenting the efficacy of these methods has been difficult.



Extravasations are an inherent risk of intravenous therapy. The primary methods for reducing tissue injury following extravasation are discontinuation of the infusion and the administration of appropriate therapy. Other measures, such as elevation or the application of hot or cold compresses, may not affect ultimate outcome, but may increase patient comfort.



Extravasation - Extravasation is breakdown of tissue due to vesicant properties of an infiltrated drug or solution)

Vesicant - A vesicant is a drug or other agent that produces blisters. Vesicants are highly active corrosive materials even at extremely low concentration.

Necrosis - The sum of the morphological changes indicative of cell death and caused by the progressive degradation of enzymes, it may affect groups of cells or part of a structure or an organ.


See also:

Infusion Devices Training Tutorial




n.b. Links above no longer functional.

John Sandham 18/01/04


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