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The use of an appropriate flush fluid with arterial line


The national investigation

This investigation will look at the risks to critically ill patients when the wrong fluid is attached to an arterial line.

An arterial line is a system used to continuously monitor a patient’s blood pressure and obtain blood samples. A cannula is inserted into the patient’s artery and tubing is used to attach to a device called a transducer. The tubing is connected to a bag of fluid known as the arterial flush and should only contain 0.9% sodium chloride (saline).

The pressure change of the fluid within the connecting plastic tubing transmits an electrical signal through the transducer to a monitoring device. The monitoring device records the blood pressure within the artery as a continuous wave line on the monitoring screen.

The use of the incorrect flush fluid can provide misleading results from the blood samples taken from an arterial line. In the event of glucose being mistaken for 0.9% sodium chloride (both clear fluids delivered in similar bags) a patient’s blood test may suggest a high level of blood sugars. This can mislead a clinician who may initiate insulin treatment. This may lead to unrecognised and dangerously low blood sugar levels. Prolonged periods of low blood sugars may cause brain damage or death.

Despite a large body of evidence and warnings over the last 13 years, events involving the wrong fluid used in conjunction with arterial lines continue to happen. HSIB was contacted by the Department of Health and Social Care and asked to consider this issue in response to a coroner’s investigation and the issuing of a prevention for future death notice.

Reference event

HSIB identified a patient safety incident involving a 66 year old man, where the wrong flush fluid was used whilst he was being treated in an NHS trust’s critical care unit.

The patient had received treatment to drain his gallbladder and became very unwell with sepsis. He was admitted to a critical care unit with severely low blood pressure. An arterial line was inserted and the wrong fluid was attached, glucose was used instead of 0.9% sodium chloride.

The impact of the use of the wrong fluid was the contamination of blood tests taken from the site of the arterial line, which consequently misled clinicians to deliver insulin. The wrong fluid went unnoticed for approximately 16 hours and the treatment of insulin reduced the patient’s blood sugar levels to below the recommended limit. The patient survived the event and no neurological harm was identified.

Investigation summary

The investigation will:

  • Consider the systemic factors recognised as influencing staff performance and the reliability in the delivery of care relevant to arterial lines
  • Consider how national guidance and working environments influence the safety in storage and use of arterial flush fluids
  • Consider how equipment design, national and international standards influence the effectiveness of existing safety controls relied upon in the use of arterial lines