Cause of Device-Related Incident
Device factors; Support system failures; User errors

Clinical Specialty or Hospital Department
CCU / ICU / NICU; OR / Surgery; Pediatrics; Pulmonary / Respiratory Therapy

Device Factors
Design / labeling error

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Exsanguination

Support System Failures
Poor prepurchase evaluation

Tampering and/or Sabotage
*Not stated

User Errors
Failure to perform pre-use inspection; Inappropriate reliance on an automated feature

UMDNS
Oxygenators, Extracorporeal, Membrane [17-643]; Pumps, Extracorporeal Perfusion [13-203]

Inadequately Secured Connections on ECMO Tubing Circuits



Hazard [Health Devices May 1994;23(5):206-7]

Problem

In the course of investigating an incident in which tubing separated at a connection during extracorporeal membrane oxygenation (ECMO), which contributed to a patient's death at a member hospital, we learned that some hospitals performing ECMO do not use supplemental securement devices, but instead rely solely on hosebarb connections to secure tubing/component junctions in the ECMO circuit. Because ECMO patients are already severely compromised, tubing separation in an ECMO circuit can cause hypovolemic complications or death, depending on the location of the separation.

In this case involving a young adult patient who had been on ECMO for 10 days, the ECMO tubing separated without warning, resulting in significant blood loss. The separation occurred at a critical junction in the ECMO circuit where 1/2-inch tubing coming from the circuit blood pump was joined to 3/8-inch tubing. The loss of blood contributed to the patient's death. We also learned that, in an unrelated case at another hospital, a separation had occurred in a similar location in an ECMO circuit; fortunately, this patient survived.

Background

ECMO is a treatment reserved for critically ill patients, most often neonates with respiratory disorders, and often involves shunting blood around the heart and lungs through an extracorporeal blood circuit and membrane oxygenator. Roller or centrifugal heart-lung bypass pumps are used to circulate blood through the ECMO circuit. Treatment courses can be as short as a few days or as long as a month or more.

As with heart-lung bypass circuits, which perform a function similar to ECMO circuits, manufacturers commonly custom assemble ECMO tubing circuits with components specified by the hospital. However, whereas heart-lung bypass circuits are generally assembled with plastic tie bands, glued connections, or other types of supplemental securement devices familiar to perfusionists, such devices are not always specified for ECMO circuits, as indicated by the two incidents mentioned above. (With heart-lung bypass circuits, the use of supplemental securement devices is considered the standard of care, and perfusionists assume that such devices will help prevent separations.)

Discussion

The exact cause of the tubing separation in the reported incident has not yet been determined; however, our testing of identical tubing circuits during this investigation has yielded the following information, which we believe may be relevant to other ECMO circuits in use:

  • Static pressures between 880 and 980 mm Hg (17 and 19 psi) can cause abrupt separation of the tubing/hosebarb connections on the ECMO circuits we tested when no supplemental securement devices are used.
  • Prolonged exposure (12 days) to roller-pump-generated oscillatory pressures with a mean value as low as 500 mm Hg (10 psi) can cause slow leakage at connectors from ECMO tubing filled with saline warmed to 37° C (98° F), which we used to simulate body-temperature blood.

While pressures in the ECMO circuit are not normally expected to reach values as high as those that we determined can cause immediate tubing separation, the margin of safety may be smaller than anticipated. The pulsatile pressure generated by the roller pump over the course of several days or weeks, combined with the warmth of the blood in the tubing, may weaken the connection and allow it to separate at lower pressures. Moreover, prolonged exposure of the tubing to warm blood may alter the tubing's mechanical properties (e.g., causing it to swell or soften), possibly changing its dimensions and thus influencing the security of the connections.

We performed a preliminary test with plastic-tie-banded connections and found that the banding did provide an added degree of security. While we are not aware of any studies that have thoroughly examined whether supplemental securement of blood circuit tubing connections improves their security and we recognize that the use of these devices can introduce other problems (e.g., overtightening of tie bands resulting in cut tubing or cracked hosebarb connectors), ECRI believes that supplemental securement measures can provide an added margin of safety and should be used in ECMO circuits.

Recommendations

  1. If your supplier of ECMO or bypass circuits is not already providing connections with supplemental securement (e.g., tie banding, ultrasonic welds, solvent welds), change your hospital's specification to include one of these features. When opening the sterile pack, always inspect tubing circuits for connector security and for defects.
  2. If the circuits are supplied without some means of supplemental securement or if connections are to be made in the hospital when preparing the circuits for patients, use tie banding to help secure connections. Inspect tubing and connectors after securing them with the bands to ensure that the tubing has not been cut and that the connectors have not been cracked.
  3. When operating ECMO systems for prolonged periods, recognize that pressures, particularly on the premembrane side of the circuit, can quickly rise (e.g., as a result of clotting); therefore, these pressures require accurate monitoring. Because pressure transducer lines can clot, which can mask dangerously high pressures or prevent monitoring systems from detecting a disconnection, they must be aspirated regularly with a syringe.
  4. ECMO circuit monitoring systems are not a replacement for continued vigilance, and technologists should be aware of changes that can precede dangerous conditions. If they note a fine spray or dripping blood at any connection in the circuit, tubing separation is likely to follow, and they should take immediate measures to reduce pressures and secure the connection.

UMDNS Terms

  • Oxygenators, Extracorporeal, Membrane [17-643]
  • Pumps, Extracorporeal Perfusion [13-203]

Cause of Device-Related Incident

Device factor: Design/labeling error

User errors: Failure to perform pre-use inspection; Inappropriate reliance on an automated feature

Support system failure: Poor prepurchase evaluation

Mechanism of Injury or Death

Exsanguination


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