Use of Isoflurane in Extracorporeal Circuit Leading Break in Polycarbonate Connector-Juniper Publishers
Juniper Publishers-Journal of Anesthesia
Abstract
Invent of cardiopulmonary bypass has
revolutionized the modern cardiac surgery. Mishaps during
cardiopulmonary bypass, near misses and lethal incidents are known. We
share one such rare case of break in polycarbonate connector due to the
use of isoflurane in extracorporeal circuit and its successful
management.
Keywords: Cardiopulmonary bypass; Polycarbonate; Isoflurane; Atrial septal defect
Cadiopulmonary bypass (CPB)
Cadiopulmonary bypass has undergone many
improvements since its first attempt to permit intracardiac surgery in
humans at the University of Minnesota Hospital by Dennis et al. on April
5, 1951 [1].
These improvements have not come without complications. Equipment
failure in cardiopulmonary bypass is lethal in most of the cases. In
extra-corporeal circulation by CPB, volatile anesthetics are generally
administered in the oxygen inlet line using a vaporizer to control the
blood pressure. However, volatile anesthetics have a physicochemical
effect on polycarbonates. There are reports of damaged plastic
anesthetic equipment and other medical devices [2-6], particularly damaged CPB parts made from polycarbonate, such as membrane oxygenators [5,6].
We share here such an equipment failure which was successfully managed
and tips to avoid such mishaps during the conduct of CPB.
Case Presentation
A 30 year old male (body surface area 1.52, full
pump flows 3.6litres/min) with no comorbidities was admitted for
surgical closure of atrial septal defect (ASD). Following induction of
anesthesia with thiopentone and maintainence was with isoflurane and
morphine sulphate. Surgery was done through midline sternotomy and CPB
was established with aortic and bicaval cannulation. After arresting the
heart with antegrade cold blood cardioplegia, under moderate
hypothermia (30 degree celsius), right atrium was opened to close the
ASD. As soon as the pericardial patch was started to suture close the
ASD, there was change in color of the arterial line from bright red to
dark color. After checking the circuit (preassembled by the
manufacturer), there was spontaneous disconnection of the gas inlet line
(Capiox SX 18R).
The problem was immediately picked up and
communication was made to anesthetist and the surgeon by the
perfusionist. Thought was given to further cooling the patient and
replace the oxygenator. As the anticipated pump run for this routinely
done surgery was just few minutes, decision was taken to handhold the
disconnected gas input connector (1/4inch) to the oxygenator, increasing
the FiO2 to 100%, sweep gas at 4litres/ min and to go ahead with
surgery. Periodic arterial blood gas analysis done showed no hypoxia or
acidosis. Patch closure of ASD was completed and cross clamp was
released after adequate deairing. Once cross clamp was released,
ventilation was resumed and there was no fall in saturations or increase
in ETCO2 noted. Came off CPB and patient was shifted to ICU with stable
hemodynamics. Total cross clamp time was 15 minutes and total CPB time
was 40 minutes. Patient became conscious 4 hours after shifting to ICU,
was extubated after 6 hours of surgery. He was discharged on third
post-operative day with no sequelae. After carefully reviewing the
incident, it was found that the cause of the crack in the connector was
traced to the initiation of CPB, when the vaporizer connected to the
membrane oxygenator was filled with isoflurane and droplets of
isoflurane fell onto the connector. After this incident, the isoflurane
vaporizer was then moved to a safer location to prevent a similar
incident from occurring again.
Discussion
CPB is the part and parcel of majority of the
cardiac surgeries from its invention in 1950s. According to a survey
between 1996 and 1998 by Mejak et al., a CPB incident of the reported
cases occurred once every 138 cases (0.7%). Break in polycarbonate
connector of extracorporeal circuit is one of the uncommon problems
encountered which may be potentially fatal.
In heart-lung bypass procedures, external circuits
comprising different devices and tubing sets that are used to provide
circulation, oxygenation and filtration of the blood as a temporary
substitute for circulatory and pulmonary function. To maintain
anesthesia and control blood pressure, a vaporizer may be included in
the circuit to allow vaporized halogenated anesthetic agent to be mixed
with the oxygen that supplies the oxygenator.
Leaching occurs when the plasticizer molecules in the PVC tubing are displaced by the anesthetic agent molecules [7].
This process is slow if the tubing is exposed only to vapors, but the
reaction can be accelerated if liquid anesthetic is accidentally spilled
from the vaporizer. As the plasticizer leaches from the tubing, the
tubing becomes stiff and can crack. An oily material, primarily the di
(2-ethylhexyl) phthalate (DEHP) plasticizer, collects inside the tubing.
Although PVC is the most commonly used plastic tubing for heart-lung
bypass circuits, plasticizers in other plastics may be soluble in
halogenated anesthetic agents and may exhibit the same problem as PVC
tubing.
Leaching of plasticizer is a known entity and care
should be taken and connection sites should be inspected by the
perfusionist while administering isoflurane. In our case, while
administering isoflurane gas by the perfusionist, there was reaction of
alcoholic agent (isoflurane) with medical grade polyvinyl chloride (PVC)
which led to melting of PVC and disconnection from the oxygenator at
the inlet site [8].
Liquid isoflurane accidently spilled from the vaporizer due to vigorous
shaking of the container. There was no blood leak from the oxygenator,
so the situation was managed by manually holding back the inlet line
with the connector.
Conclusion
CPB circuit though is undergoing continuous
modifications since its first use, are still not completely safe. During
administering anesthetic gases like isoflurane, perfusionist should be
cautious and look for the connection sites. Timely recognition and
thoughtful management of the mishap during CPB are lifesaving. This case
highlights the need for anesthesiologists to be alert to the
physicochemical effects of volatile anesthetics on polycarbonates.
Consent
Written informed consent was obtained from the
patient for publication of this case report and any accompanying images.
Hospital ethical committee approval was taken for publishing the case
report.
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