Inadequately Secured Connections on ECMO Tubing Circuits
Hazard [Health Devices May 1994;23(5):206-7]
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.
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.)
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
- 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.
- 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.
- 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.
- 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.
- 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.
- Oxygenators, Extracorporeal, Membrane [17-643]
- Pumps, Extracorporeal Perfusion
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