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Written on 31st March 2023 by Susan Brown

Healthcare watchdog, the Healthcare Safety Investigation Branch (HSIB) has warned that incorrect use of central venous catheters in dialysis treatment may cause life-threatening injury from air embolism. The report, Safety risk of air embolus associated with central venous catheters used for haemodialysis treatment, highlights that air embolism, caused by air being allowed to enter the patient’s bloodstream through their dialysis catheter, can cause heart failure, cardiac arrest or the patient’s death.

HSIB’s aim is that this investigation will improve patient safety by helping healthcare staff to use tunnelled haemodialysis central venous catheters safely. This type of central line is commonly used to access the blood supply during dialysis treatment of patients with kidney failure.  HSIB warns that if the catheter is left ‘uncapped and unclamped’ without attaching a syringe, letting air into the bloodstream, the patient may be at risk of life-threatening air embolism.

Nearly 30,000 people in the UK receive dialysis treatment. Haemodialysis catheters are used in more than one million treatments a year for thousands of patients with kidney failure. One national database shows that 14 air embolus patient safety incidents involving uncapped and unclamped lines were reported between 2017 and 2022. Another database identified 70 reports of central lines being found uncapped and unclamped in the same 5-year period.

HSIB found a lack of safeguards to reduce the risks of injury from uncapped and unclamped catheters and called for action to be taken to raise awareness of the risks amongst NHS staff.

What is haemodialysis?

Haemodialysis is a treatment for people with poor kidney function, which filters and purifies their blood to prevent unwanted substances building up to harmful and potentially fatal levels. During haemodialysis, blood is taken from the patient’s body and passed through a dialysis machine where it is filtered and then passed back into the body.

HSIB’s investigation focussed on the use of tunnelled dialysis catheters, which is one of the ways in which the patient’s blood supply can be accessed for dialysis treatment.  This involves inserting a plastic tube through a vein in the patient’s neck into a large vein in their chest.  The end of the tube which is outside the body is split into two tubes, each with a clamp and with a cap on the end. The patient’s blood flows out of the body and through the dialysis machine via one tube and out of the machine and back into the body via the other tube continuously during haemodialysis treatment. The clamps on the tubes can be opened to access the patient’s blood supply, such as during dialysis or to take a blood sample. If the catheter (tube or line) is unclamped without the tube being connected to the dialysis machine or a syringe for taking blood, the blood supply will be open to the air, with a risk of creating an air embolus.

What is an air embolism?

Air embolism is the name given to air bubbles (air embolus) which get into a vein and block the flow of blood. This dangerous condition can cause heart failure and cardiac arrest and death. The catheters used in haemodialysis are designed to allow a high volume of blood flow and have a wider internal diameter than other types of central line. This increases the risk of large air embolus (air bubbles) entering the bloodstream if the catheter is uncapped and unclamped without first being connected to a syringe by someone who is not familiar with the medical device, the equipment or the task.

HSIB’s investigation found that air embolism during treatment using haemodialysis catheters is considered to be rare and ‘avoidable’ with correct care. However, HSIB also found that research into the safe use of central venous catheters for dialysis hasn’t focussed on their use once they are already in place.  In practise, HSIB found that healthcare staff in hospitals which do not routinely provide dialysis treatment are less likely to have the skills, competence and correct equipment to manage haemodialysis catheters safely.

HSIB notified following Coroner’s ‘Prevention of Future Deaths’ report after air embolus led to patient’s death.

HSIB’s investigation was triggered by a Prevention of Future Deaths report by a coroner after a 75-year-old, long-term haemodialysis patient suffered a cardiac arrest from an air embolus, which ultimately led to her death. During hospital investigations for an infection,  a blood sample was carried out by a medical student under the supervision of a junior doctor. The doctor unclamped the line which had been uncapped by the student, allowing air into the patient’s blood supply through the open line. The patient suffered a cardiac arrest from an air embolism and was resuscitated, but died two days later from multi-organ failure and sepsis.

HSIB found that her blood cultures had been taken from a haemodialysis catheter in an inappropriate location, without access to necessary equipment, by staff who were not competent to perform the procedure. The report notes that the General Medical Council (GMC), which sets and regulates training standards for doctors, says that taking blood samples from central lines is a specialist procedure which is beyond the level of competence required for newly qualified doctors.

In recent months, further cases have been reported to HSIB arising from central venous catheter lumens (tubes) being left open, including the death of a patient after an air embolus entered his brain, causing a catastrophic brain injury.

Findings from HSIB’s safety risks from dialysis catheters investigation report

Key findings from HSIB’s investigation included:

  • No long-term haemodialysis catheters on the UK market, or currently being developed, have integrated ‘safety-valves’.
  • The current design of dialysis catheters is not helpful in reducing risk because manual clamps on dialysis catheters rely on healthcare staff to ensure that the clamp is on before accessing the catheter port.
  • An assumption that incidents involving dialysis catheters are the result of ‘human error’ rather than the equipment’s design has led to incidents being under-reported to the Medicines and Healthcare products Regulatory Agency (MHRA).
  • Aids to safety which are used for other haemodialysis devices, such as coloured patient wristbands, alert cards carried by patients, line labelling and educating of family members, are not consistently used for haemodialysis catheters.
  • The training and education in the risks of catheter-related air embolism for medical staff at all levels is inconsistent.
  • There are no national training guidelines or recognised national training for the safe use of haemodialysis catheters.
  • There is also a general lack of literature and knowledge of air embolism  relating to access to catheters already in place, rather than during insertion or removal of the catheter.

HSIB recommended that GMC guidance makes clear that newly qualified doctors should only take blood from peripheral sites, such as arms or hands, and not from central lines. Medical students need help to handle uncertainty in clinical settings. HSIB also  recommended that MHRA’s dialysis guidance should address the safety risks of air embolus from unclamped haemodialysis catheters.

In addition, HSIB made safety observations suggesting that it might be helpful if manufacturers of haemodialysis catheters developed catheters which maintained a sealed system, to reduce the risk of an air embolism. Other observations included considering how junior doctors could be supported to work safely within their level of competence and decline tasks which are beyond their competence, specifically in relation to accessing haemodialysis catheters where they lack the necessary training and competence. HSIB also suggested that visual alerts about the risks of haemodialysis catheters and standardisation of vascular access services in hospitals might be helpful in raising awareness and reducing patient safety incidents.

Air embolism from central venous catheters (central lines) can cause catastrophic injury, including cardiac arrest, damage to the brain and other vital organs, and death. With correct equipment design, training and care these devastating incidents can be avoided. We welcome HSIB’s findings and insights into how the healthcare system can raise awareness and reduce risk, in the hope that further unnecessary harm to patients can be avoided.

If you have been seriously injured or bereaved as a result of medical negligence, or have been contacted by HSIB/HSSIB or NHS Resolution , you can talk to a specialist medical negligence claims solicitor, free and confidentially, by contacting us here.