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Written on 12th August 2022 by Julie Marsh

Healthcare safety watchdog, HSIB, has reported that patients in critical care may be at risk of brain injury from incorrect flushing of arterial lines.  HSIB’s investigation followed the potentially dangerous treatment of a patient with insulin for hyperglycaemia (raised blood sugar) because his arterial blood sample was contaminated by glucose which had incorrectly been used instead of saline to flush his arterial line.  

HSIB’s report, The use of an appropriate flush fluid with arterial lines, found that there is a known risk of brain injury or death of the patient associated with standard systems used for monitoring critically ill patients’ blood glucose levels if the wrong type of fluid is used to flush an arterial line. The report emphasises that despite safety alerts, multiple recommendations and changes in guidelines, there is still a continued risk of serious harm to patients arising from use of the wrong fluid to flush their arterial lines.  

What is arterial line blood sampling?

It is standard recommended treatment that adult patients who need critical care for serious or complex conditions have their blood pressure continuously monitored and their blood sugar (glucose) intermittently checked using an arterial line. Correct monitoring and control of blood glucose levels is associated with better outcomes for patients. Whilst in other settings blood sugar is often tested by a finger prick (capillary blood) test, in critical care units it is recommended that blood glucose is checked using samples of blood from the patient’s artery (via the arterial line) as arterial blood sampling provides more accurate results.

A cannula (thin tube) is inserted into the patient’s artery with tubes attached to a transducer device and a bag of saline which is known as the ‘flush fluid’. Changes of pressure in the fluid in the tubes are recorded by the transducer and the blood pressure within the artery is displayed as a continuous wave line on a monitoring screen. The saline solution flush fluid is used to keep the tubes open and free from clotted blood.

Using the wrong flush fluid is a recognised safety risk in the use of arterial lines. If glucose is used instead of saline, this can contaminate samples of arterial blood that are taken for blood sugar testing, and lead to a false raised blood glucose (hyperglycaemia) result. Patients who are incorrectly diagnosed with hyperglycaemia may be treated with insulin ( a drug which controls blood sugar), leading to dangerously low blood glucose levels (hypoglycaemia), a potential cause of coma, brain injury and death.

HSIB’s investigation was triggered by patients’ experiences – the reference event

HSIB was alerted to the safety risks from incorrect flush fluids used in arterial lines when a coroner issued a prevention of future deaths notice after finding that the use of glucose instead of saline to flush an arterial line had contributed to a 57-year-old woman’s death.  

HSIB started a national safety investigation, with reference to the experience of a 66-year-old man whose arterial line was incorrectly flushed with glucose during his treatment on a critical care unit for low blood pressure and sepsis after gallbladder drainage treatment.  The glucose contaminated his arterial blood samples, leading to a false diagnosis of hyperglycaemia and many hours of potentially dangerous insulin treatment.  His blood sugar dropped below safe levels (hypoglycaemia) and when the mistake was finally recognised the next day, the insulin was stopped and he needed glucose to bring up his blood sugar to safe levels. A brain scan the same day found no evidence of damage to his brain, but he died a few weeks later from an unrelated, hospital acquired COVID-19 infection.   

HSIB’s investigation identified multiple factors which contributed to the error and the delay in recognising the mistake, including staff shortages, fatigue and work overload with multiple competing demands on the nurses’ attention, issues relating to the labelling, packaging and storage of equipment and fluids for arterial lines, time pressures from the severe demands of the patient’s deteriorating condition.  Additional factors included the familiarity and  ‘normalisation’ of hyperglycaemia in patients with conditions such as sepsis in critical care, which resulted in the staff being less likely to question whether incorrect flush fluid and contamination of the sample might be the cause of the high blood sugar result.

HSIB’s search of the national incident reporting database over a five-year-period from 2016-2021 found 447 reports of adult patient safety incidents involving various incorrect flush fluids, suggesting that this is a system-wide problem.  HSIB also found that in recent years, many attempts have been made to raise awareness of these risks, including safety alerts issued by the National Patient Safety Agency (NPSA) in 2008 and the Medicines and Healthcare products Regulatory Agency (MHRA) in 2014, and system-wide recommendations by the Association of Anaesthetists of Great Britain and Ireland in 2014.

HSIB’s findings from their investigation into use of incorrect flush fluids in arterial lines 

HSIB’s findings from its national investigation into the patient safety risks from use of incorrect flush fluids in arterial lines included:

  • Despite safety alerts, multiple recommendations and changes in guidelines, the risk of harm and brain injury caused by low blood sugar levels (hypoglycaemia) associated with the use of incorrect flush fluids with arterial lines, continues to exist.
  • The physical layout and design of clinical and storage areas influence how reliably staff can correctly select similar-looking equipment and medication.
  • The labelling of bags of fluids, similar looking medications and manufacturers’ packaging reduce the reliability of selecting the correct flush fluid in the context of a critical care unit with time pressures and high workloads.
  • Current procurement and design of equipment isn’t helping to correctly identify flush fluids or prevent blood samples being  contaminated by flush fluids. Alternatives which may reduce the risk are currently available to the NHS but are not in use.
  • Normalisation and acceptance that critically ill patients may have altered blood glucose levels and require insulin treatment, and a perception that flush fluids are low risk may lead to delays in recognising when arterial line blood samples have been contaminated with glucose.  
  • The design of recording and monitoring systems relating to the arterial transducer line system and blood glucose levels do not easily alert staff to the potential use of the wrong flush fluid.
  • Workforce shortages and high workloads are reducing the safety controls, such as safety checks and training, which critical care units rely upon to avoid or identify the risk of using the wrong flush fluid.
  • Recommendations issued by national safety bodies and professional healthcare organisations over the last 14 years to address the safety of blood sampling from arterial lines have not been effectively implemented.

The report makes six safety recommendations and eight additional safety observations, to encourage more helpful design and clearer labelling of devices, equipment and fluids, to better manage and increase awareness of the risks associated with arterial lines and to develop, improve and implement consistent national guidance.

If you have been severely injured or suffered the loss of a loved one as a result of medical negligence and would like to find out more about claiming compensation, you can talk to one of our experienced solicitors, free and confidentially, by contacting us here.