improvement over the use of open systems in an
uncontrolled environment, it should not be
assumed that product sterility is automatically
guaranteed. There is huge variation in the
environmental quality of clinical areas in
oncology units, variation in cleaning and
sanitisation practices, differences in staff training
and competency assessment and, subsequently,
the potential for significant variation in the
bioburden that challenges the integrity of the
CSTD in different centres. In the opinion of the
author, the use of CSTDs in this type of
environment requires careful validation and
control for each individual area in which
infusions are prepared to ensure sterility is not
compromised. Closed systems are increasingly
deployed in infusion/injection administration sets
to minimise the exposure of chemotherapy
nurses to cytotoxic drugs in outpatient clinics.
There is currently much debate concerning
whether pharmacy should provide infusion bags
and syringes of cytotoxic drugs with CSTD devices
already fitted. The aim is to avoid compromising
sterility or risking cytotoxic contamination when
nurses spike infusion bags or connect syringes,
but in solving these issues other problems around
product integrity are created. Progress on these
matters will require much more ‘joined-up’
thinking between nursing and pharmacy staff.
and pharmaceutical isolators discharge air outside
of the isolator through one or two HEPA filters,
and ideally to the outside of the building via
fan-assisted external ducting. As with product
protection, above, the open face of the Class II
cabinet presents a potential weakness in that
disturbance of the air flow in the ‘protective
curtain’ of air directed vertically from the top of
the open face into the plenum at the base of the
work area might permit air currents to drift from
the cabinet to the outside. The author has seen
smoke tube experiments where a combination of
overloading the cabinet with equipment (syringe
filling pump) and movement in the aseptic room
in front of the cabinet have resulted in trails of
smoke tracking along the operator’s arms,
through the protective curtain and into the
proximity of the operators face.
Isolators provide a physical barrier between
the cytotoxic manipulation area and the operator.
After initial resistance from UK pharmacy staff in
the 1980s, most technicians and pharmacy
assistants prefer isolators because they ‘feel safer’.
There may, however, be an element of a ‘false
sense of security’ about this. In the case of
a positive pressure isolator, leaks in the isolator
chamber, gloves or sleeves, exhaust HEPA filters
or the external ducting could result in
contaminated air being pumped into the outside
environment. As with Class II cabinets, isolators
(whether operated under positive or negative
pressure) must be validated, monitored, tested
and fully maintained to work effectively.
A less obvious problem with isolators relates
to the fact they are containment devices, and also
difficult to clean and remove cytotoxic drug
residues. 2 This means that the inside of isolators
and transfer hatches can become contaminated
with cytotoxics, even when regular cleaning
Protection of staff
In the pharmacy setting, mechanical ventilation
in the form of Class II cytotoxic cabinets and
isolators are at the top end of the controls
designed to protect staff from occupational
exposure to cytotoxic drugs. The hierarchy
beneath this includes staff training, safe systems
of work, personal protective equipment and
environmental monitoring. Both Class II cabinets
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