Note: Descriptions are shown in the official language in which they were submitted.
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
APPARATUS, SYSTEMS, AND METHODS FOR WARMING MATERIALS
Field of the Invention
The present invention relates to apparatus, systems, and methods for the
warming of materials.
Background of the Invention
Commonly during the performance of surgical procedures utilizing sterile
fields, solutions need to be used for irrigation of tissues and for other
purposes. When
1o irrigating solutions are used, or when irrigating solutions are applied to
tissues over
large surface areas, contact with a solution that is cooler than body
temperature can
lead to clinically important cooling of the tissues or of the entire patient
and potential
hypothermia. A supply of irrigating solutions at or warmer than body
temperature is
therefore generally kept available. Providing warmed solutions, however,
requires
15 attention from the nursing staff. Presently, sterile saline and other
solutions for use in
the operating room°are warmed up and stored in heated cabinets. When
additional
warm solutions are needed, a nurse or technician must retrieve a fresh supply
from the
storage cabinet. The solution must then be sterilely poured into a receptacle
on the
sterile field, from which location it immediately begins to lose heat.
2o Receptacles available to hold surgical fluids are generally bowls or
similar
containers open to air and uninsulated. The typical receptacle for containing
fluids
provides no means for maintaining the fluid's temperature. Therefore, even
though
initially warmed, the heated fluid rapidly cools after it has been poured. By
the time
the fluid is applied to the patient, it may be significantly cooler than body
temperature.
25 Application of those fluids to the patient may cause clinically important
hypothermia.
This hypothermia may have significant deleterious effects on patients
including
problems with blood clotting. In the pediatric patient population, hypothermia
can be
particularly hazardous to patients. To raise the temperature of a volume of
fluid that
has cooled, additional heated fluid may be added to the basin. This additional
volume
30 of fluid may be unnecessary for surgical purposes and is employed only to
raise the
mixture's temperature to a more suitable level. Similarly, the staff may not
think of or
have readily available newly warmed fluids, thereby exposing the patient to
cool fluids
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-2-
and subsequent hypothermia. From the clinical standpoint, the additional fluid
is
unnecessary and may go to waste. Other methods besides fluid mixing would be
desirable for keeping a volume of fluid warm on the sterile field.
Warming units have been devised for other applications where maintaining a
sterile field is not an issue. U. S. Patent No. 4,996,405 and U. S. Patent No.
3,766,360
are examples of such devices. The surgical setting poses a distinct problem,
however,
in that any warmer adapted for residing on the sterile field must itself be
sterile and
remain sterile throughout the surgical procedure. The energy source for a
warmer
1o designed to reside on a sterile field must similarly not interfere with the
ambient
sterility of this workspace. There remains in the art, therefore, a need for a
warming
unit particularly adapted for functioning in a sterile surgical environment.
Such a
warming unit would desirably be in its outer aspect sterile or sterilizable.
Such a
warming unit would further be able to achieve a relatively constant
temperature in a
volume of fluid. Mechanisms for controlling temperature have been disclosed in
other
patents relating to devices suited for other, non-sterile applications, for
example U. S.
Patent Nos. 4,153,833, 4,900,161, and 4,962,297. Advantageously, a warming
unit
adapted for the surgical environment would be usable with conventional fluid
receptacles. It would also be desirable to provide a warming unit efficiently
fabricated
from relatively inexpensive materials and adapted for use with disposable
components.
No commonly available device exists that satisfactorily keeps a solution warm
once it is on the sterile field.
Certain technologies are known in the art to use chemical means for providing
local heat, for example U. S. Patent No. 4,077,390, U. S. Patent No.
4,872,442, U. S.
Patent No. 5,791,334, U.S. Patent No. 6,116,231 and U. S. Patent No.
4,572,158.
There remains a need in the art, however, for a warming apparatus particularly
adapted
to the needs of the surgical setting.
Summary
3o In an embodiment, an apparatus for generating heat comprises a rigid
container
within which a material to be warmed is contained, a chamber disposed about
the
container, and an activatable heating substance positioned within the chamber,
which
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-3-
activatable heating substance when activated releases heat to warm the
material within
the container.
In an embodiment, the heating substance is a supercooled salt solution. In an
embodiment, the apparatus further comprises an initiator which activates the
heating
substance. In an embodiment, the initiator comprises a plunger penetrably
displaceable
into the chamber to contact the activatable heating substance. In an
embodiment, the
chamber comprises a hole and a foil seal sealing the hole, and wherein the
plunger is
penetrably displaceable through the foil seal and the hole.
In an embodiment, the initiator comprises a plunger and a trigger coupled to
the
to plunger, the plunger adjacent a hole into the chamber, and the hole sealed
by a
diaphragm, when the trigger is unpulled. In an embodiment, the plunger
penetrates the
diaphragm when the trigger is pulled, and the activatable heating substance is
contacted
to an ambient environment. In an embodiment, the plunger is hollow, and the
ambient
environment comprises a quantity of air inside the plunger.
In an embodiment, the activatable heating substance comprises calcium
chloride, and the initiator comprises water. In an embodiment, the initiator
comprises a
plunger penetrably displaceable into the chamber and removably coupled to an
activator. In an embodiment, the initiator comprises a spring flexibly mounted
in an
opening of the chamber. In an embodiment, the initiator comprises a disk
flexibly
2o mounted in an opening of the chamber.
In an embodiment, the initiator comprises a screw having a noninsulated
proximal end and an electrically insulated distal end, which screw is disposed
in a
threaded hole into the chamber such that the proximal end does not contact the
activatable heating substance. In an embodiment, the screw is advanced through
the
threaded hole, whereby the proximal end contacts the activatable heating
substance and
activates the substance.
In an embodiment, the apparatus further comprises a lid removably coupled to
the container. In an embodiment, the lid comprises a hinge and wherein a
portion of
the lid is hingedly rotatable.
3o In an embodiment, the apparatus further comprises an insulating sleeve
disposed about the chamber. In an embodiment, the insulating sleeve comprises
one of
neoprene, styrofoam, or urethane.
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-4-
In an embodiment, with activation, the activatable heating substance produces
heat sufficient to warm the material within the container to a preselected
temperature.
In an embodiment, wherein with activation, the activatable heating substance
produces
heat sufficient to maintain the material above room temperature for at least
about 2
hours and most preferably at least about 4 hours. In an embodiment, the
activatable
heating substance comprises about 1250 milliliters of supercooled sodium
acetate
solution having a concentration of about 17.68 molar, which substance upon
activation
produces heat sufficient to warm about 800 milliliters of material at about
68.5 degrees
Fahrenheit to a temperature between 95 and 120 degrees Fahrenheit and maintain
it
1o between 95 and 120 degrees Fahrenheit for at least 4 hours. In an
embodiment,
wherein the activatable heating substance comprises about 400 milliliters of
supercooled sodium acetate solution having a concentration of about 17.68
molar,
which substance upon activation produces heat sufficient to maintain about 500
milliliters of material pre-warmed to about 98.6 degrees Fahrenheit at a
temperature
between 95 and 120 degrees Fahrenheit for at least 4 hours.
In an embodiment, the container comprises one of polypropylene, nylon,
polyethylene, vinyl, stainless steel, and titanium. In an embodiment, the
container
comprises a spout. In an embodiment, the apparatus is sterilizable. In an
embodiment
the apparatus is designed to work with existing surgical fluid bowls.
2o In an embodiment, the heating substance has a first state prior to
activating and
a second state after activating. In an embodiment, the heating substance is
restored to
the first state after activation and may be activated again.
In an embodiment, a warming container comprises an inner wall and an outer
wall, the inner wall defining an inner chamber to receive an article to be
warmed
therein, the outer wall and inner wall defining an outer chamber, the outer
chamber
being airtight, the inner wall separating the outer chamber from the inner
chamber and
preventing communication between the chambers; a supercooled aqueous salt
solution,
disposed within and at least partly filling the outer chamber; and an
initiator associated
with the warming container for selectively activating the supercooled aqueous
salt
3o solution to cause the solution to undergo an exothermic crystallization.
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-5-
In an embodiment, a warming container comprises a bowl, a sleeve disposed
about the bowl, the bowl and sleeve defining a chamber therebetween, and a bag
containing an activatable heating substance disposed within the chamber.
In an embodiment, a system for warming surgical fluids comprises a power
source; a sterile enclosure for the power source; a resistive heater powered
by and
operably connected to the power source, the resistive heater being capable of
being
rendered sterile prior to its operable connection to the power source and
further capable
of remaining sterile after being operably connected to the power source; and a
bowl
holder dimensionally adapted for stably holding a surgical bowl and capable of
to transferring heat produced by the resistive heater to surgical fluid
contained within the
surgical bowl.
In an embodiment, the power source comprises a rechargeable battery. In an
embodiment, the sterile enclosure is disposable. In an embodiment, the
resistive heater
surrounds a portion of the surgical bowl. In an embodiment, the system further
comprises a temperature controller for regulating the heat produced by the
resistive
heater. In an embodiment, the system.further comprises a temperature feedback
system
having a temperature sensor that senses the temperature of the fluid within
the surgical
bowl and a temperature signaler that signals the temperature controller to
regulate the
heat produced by the resistive heater so as to achieve a pre-selected
temperature within
2o the fluid.
In an embodiment, a method for waxming a material comprises providing an
apparatus for generating heat, comprising a rigid container and an activatable
heating
substance disposed about the container; positioning the material to be warmed
within
the container; and activating the heating substance.
In an embodiment, a method for warming a material comprises providing an
apparatus for generating heat, comprising a rigid container, placing an
activatable
heating substance around the container; positioning the material to be warmed
within
the container; and activating the heating substance.
In an embodiment, a method for warming a material comprises providing an
3o apparatus for generating heat, comprising a rigid container, an activatable
heating
substance disposed about the container, and an initiator to activate the
activatable
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-6-
heating substance; positioning the material to be warmed within the container;
and
activating the initiator.
In an embodiment, the heating substance has a first state prior to activating
and
a second state after activating. In an embodiment, the method fiuther
comprises
restoring the heating substance to the first state.
Brief Description of the Figures
The following figures depict certain illustrative embodiments in which like
reference numerals refer to like elements. These depicted embodiments are to
be
1o understood as merely illustrative of embodiments and not limiting in any
way.
FIG. 1 depicts a perspective view of an embodiment of a surgical solution
warmer system.
FIG. 2A depicts a top view of an embodiment of a fluid warmer system.
FIG. 2B depicts a side view of an embodiment of a fluid warmer system.
FIG. 2C depicts a front view of an embodiment of a fluid warmer system.
FIG. 3 depicts a side view of another embodiment of a fluid warmer system.
FIG. 4 depicts a partial cross-section view of an embodiment of a fluid warmer
system.
FIG. 6 depicts a cross-section view of an embodiment of a surgical solution
warmer system.
FIG. 7 depicts in partial cross-section an embodiment of an activation
assembly.
FIG. 8 depicts a cross sectional view of another embodiment of a solution
warmer system.
FIG. 9 provides a perspective view of embodiment of a solution warmer system
and air activation mechanism.
FIG. 10 depicts the solution warmer system and a spring activation mechanism.
FIG. 11 depicts the solution warmer system and a disk activation mechanism.
FIG. 11A depicts the solution warmer system and a screw activation
mechanism.
FIG. 11B depicts the solution warmer system and a screw activation
mechanism in the activated mode.
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
FIG. 12 depicts a solution warmer having a bag containing activatable heating
substance.
FIG. 13 is a graph showing a heating profile of a warmer containing prewarmed
fluid.
FIG. 14 is a graph showing a heating profile of a warmer containing room
temperature fluid.
Detailed Description
to ~ 1. General
Any device being considered for use in the operating room, cardiac
catheterization lab, interventional radiology suite, or other sterile settings
readily
apparent to one of skill in the art should provide certain features so that it
can be safely
used in the surgical setting. First, a warmer being kept on the sterile field
must not
15 interfere with the sterility of the sterile field. Next, a warmer must be
electrically safe
in the presence of flammable anesthetics and other gases. In addition, a
warmer should
warm fluids to a preselected temperature range so that the fluids are not too
hot or too
cool to be safely applied to the patient. Furthermore, the container for the
fluids being
kept warm should desirably either be disposable or easily sterilizable.
Additionally,
2o because the tables used for holding instruments and other apparatus used in
surgery are
moved around during the prep process and sometimes during the surgery, it is
preferred
that the warmer be completely~mobile without the need for further set up or
prep each
time it is moved. In some instances it is desirable to configure the warmer
for use with
existing hospital surgical fluid bowls.
2. Definition '
As used herein, the term "activatable heating substance" includes any
substance
that responds to an initiator or an initiating stimulus by producing heat.
Examples of
such substances include supercooled salt solutions and any compounds capable
of
3o undergoing exothermic chemical or physical changes. Initiating stimuli
include
application of any form of energy, including chemical, mechanical, thermal,
solar,
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
_g_
electromagnetic, ionizing radiation, and any other form of energy known to one
of skill
in the art.
3. Embodiments
In one embodiment, depicted in FIG. 1, a fluid warmer system 10 is adapted for
keeping solutions warm on sterile field. FIG. 1 illustrates a bowl 22 that may
contain
fluids, the bowl being positioned upon a warming mechanism. The warming
mechanism may include a resistive heater 14 upon which or within which the
bowl 22
may be seated or positioned. A resistive heater 14 may be constructed to match
the
1o size or shape of the bowl 22. As used herein, the bowl 22 may be any type
of
receptacle adapted for containing surgical fluids. For example, a metal
solution bowl
commonly available in the operating suite may be used. Similarly, a metal
pitcher may
be used as a bowl 22 to contain fluids within the solution warmer system 10.
Customized bowls may be devised and included as part of the solution warmer
system
10. While standard plastic irrigation bowls may not be suitable because they
will not
tolerate prolonged elevated temperatures, it will be apparent to practitioners
in the art
that alternative materials for bowl construction may be employed
satisfactorily within
the scope of the present invention. In the depicted embodiment, there is a
depression in
the resistive heater plate 14 that provides a bowl holder 28 for the bowl 22.
Other
2o types of bowl holders 28 can also be employed. For example, a latch may be
provided
that clips onto a rim or groove in the bowl 22. Or a spring loaded button may
be
configured to snap into an indentation in the bowl. Other securing
arrangements may
also be constructed. The resistive heater 14 may be positioned at the bottom
of the
bowl 22 as illustrated in FIG. 1. Alternatively, a resistive heater 14 may be
constructed
that surrounds the bowl 22 entirely or partially. In such an embodiment, the
shaping of
the resistive heater 14 that holds the bowl 22 is understood to be a bowl
holder 28, as
the term is used in this application. In the depicted embodiment, a
temperature sensor
24 is shown as part of the warming mechanism. The temperature sensor 24
functions
to keep the temperature of the resistive heater 14 at an appropriate level.
The
3o temperature sensor 24 may include a feedback circuit or any other
arrangement familiar
to skilled artisans for regulating temperatures. In the depicted embodiment, a
temperature controller 20 is illustrated that performs the necessary
temperature
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-9-
adjustments in response to signals from the temperature sensor 24. FIG. 1
shows an
enclosure 12 positioned to cover the internal elements of the solution warmer
system
10. These internal elements include a battery 18 and the temperature
controller 20.
The enclosure 12 may be provided as a sterile or sterilizable box-like
structure into
which the assembled internal elements may be placed. In certain embodiments,
the
enclosure 12 may be disposable and intended for single use. The enclosure 12
is
adapted for becoming and remaining sterile on the back table in the operating
room.
Similarly, the warming mechanism and the bowl 22 are adapted for becoming and
remaining sterile. The construction of the fluid warmer system 10 provides,
therefore,
1o an entirely sterile device that should pose no risk to the integrity of the
sterile field.
Figs. 2A, 2B and 2C show, respectively, a top view, a side view and a front
view of an embodiment of the present invention. FIG. 2A depicts the top of the
fluid
warmer system without a bowl in place. The resistive heater 14 as shown here
is a
_ square plate with the temperature sensor 24 centered therein. As mentioned
previously,
other shapes of the resistive heater 14 may be utilized in the present
invention.
Similarly, other,positioning of the temperature sensor 24 are consistent with
the present
invention. FIG. 2B shows a side view of the device, with its contents made
visible.
Illustrative dimensions are marked on the figure. In this figure, a battery
charger 30 is
shown along with a sealed lead acid battery 18 and a temperature controller
20. The
2o battery charger 30 may run from a standard alternating current as would be
found in the
operating room, permitting the lead acid battery 18 to be charged during the
procedure
as necessary. In other embodiments of the present invention, there may not be
a
battery charger 30 present in the device. In these embodiments, the fluid
warmer might
be entirely powered by non-rechargeable batteries. Yet other embodiments might
rely
upon an external source of power instead of batteries. FIG. 2C shows a front
view of
the warming device with its contents made visible, wherein the battery 18, the
temperature controller 20 and the battery charger 30 are seen, all enclosed
within the
enclosure 12. Those elements that singly or in combination provide power to
heat the
resistive heater 14 may be termed the power source. An indicator may be
provided on
3o the surface of the enclosure 12 to show battery life, the charging status
of the battery,
or the use of an external power source.
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-10-
FIG. 3 shows one possible configuration of the enclosure 12. In the depicted
embodiment, the enclosure is shown to have a lid 40 which may be opened and
closed
to admit the internal elements of the device. As has been previously
described, the
enclosure 12 is adapted for holding such internal elements as a battery, a
battery
charger, and a temperature controller. The lid 40 shown in FIG. 3 opens at a
hinged
junction 42 and closes with a latch 44 at the end opposite the hinged joint
42. Any type
of easily operated latch 44 would be suitable. The lid 40 opens sufficiently
that the
internal elements can be placed within the enclosure 12 without contaminating
the
external surface of the sterile enclosure 12. In the depicted embodiment,
attachment
to pegs 48 may be seen which interface with the internal elements of the
device and also
interface with the resistive heater 14. As shown in this figure, the
attachment pegs 48
are dimensionally adapted for fitting into a corresponding set of attachment
slots 50.
Energy to power the resistive heater 14 may flow from the internal elements
through the attachment pegs 48, thereby to pass unimpeded through the sterile
enclosure 12. Other opening mechanisms for the enclosure 12 may be substituted
for
the embodiment depicted here. For example, a specially constructed battery and
related apparatus may be inserted into a slot provided in the enclosure 12
using a tool
shaped to fit into the slot on a distal end and shaped to be held on its
proximal end by a
circulating nurse in the operating room on its proximal end. In another
embodiment, a
2o hinge door may be provided on a lateral aspect of the enclosure through
which a
battery could be inserted into the device. A tool could be provided with a
distal sterile
end that could releasably engage the hinge door, permitting the circulating
nurse to
open and close it. The proximal end of the tool, available for the nurse to
hold, could
allow the nurse to open and close the door and further could there be
releasing
mechanism so that the tool could be disengaged from the hinge door once it is
secured.
FIG. 4 depicts yet another embodiment of the present invention, showing a
bowl 22 surrounded by a resistive heater 14 so that fluids in the bowl are
heated on all
sides. A lid 62 is also shown as a useful option for keeping the heated fluids
warm.
The resistive heater 14 is shown schematically in relation to the internal
elements 60 of
3o the warming system 10. It is understood that the internal elements 60 may
not reside
below the resistive heater 14, but rather may be positioned in a convenient
place that
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-11-
allows them to provide energy to the resistive heater 14 and also allows them
to be
inserted into the sterile or sterilizable enclosure 12.
In certain embodiments, sterility may be ensured by providing a disposable
sterile drape adapted for enclosing the enclosure surrounding the internal
elements. In
these embodiments, the sterile drape comprises a sterile enclosure for the
power source.
An alternative to integrating the heater into the warming plate is to
integrate the heater
coil into the disposable drape. A variety of shapes for the heating element
may also be
envisioned. A representative shape of heating coils or heating etchings is
attached as
FIG. 5, although a wide variety of other shape arrangements can be used, as
will be
1o appreciated by practitioners of ordinary skill.
FIG. 6 depicts an embodiment of a surgical solution warmer system 10
according to the present invention. The figure provides a cross sectional view
of the
warmer system 10 having a fluid receptacle 12 with a receptacle wall 14. The
receptacle wall 14 is in direct contact with a chamber 20 which may be filled
with a
15 chemical solution or activatable heating substance that, upon activation,
generates heat
energy. The receptacle wall 14 may be made of any material that will transmit
heat to
a solution placed within the fluid receptacle 12 and that will tolerate the
heat generated
by activated heating substance. In an embodiment, polypropylene may be used to
form
the fluid receptacle 12. The receptacle 12 may also be formed from other
materials,
2o such as nylon, polyethylene, vinyl, stainless steel, and titanium, and
other materials
may readily be envisioned by practitioners of ordinary skill in the art. .In
the depicted
embodiment, fluid may be poured into the fluid receptacle 12 through a hinged
lid 38.
The hinge 40 shown in FIG. 6 is placed in the mid portion of the lid 38. Other
hinged
arrangements and other opening and closing mechanisms for the lid may be
provided in
25 other embodiments of the present invention.
In the depicted embodiment, the chamber 20 for holding the heating substance
is contained between the receptacle wall 14 and an outer wall 18. An insulator
or
sleeve 22 may be provided to retain the heat generated by the activated
heating
substance within the warmer system 10. In one embodiment, the fluid receptacle
12
3o could be made to contain one to two liters of solution and may keep that
solution at
body temperature for between about two and five hours, depending on
environmental
conditions and container design.
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-12-
In an embodiment, a warmer system according to the present invention may use
the technology of supercooled fluids to produce heat. In one embodiment, a
food grade
salt such as sodium acetate may be instilled into the chamber 20 as the
activatable
heating substance. This salt freezes (crystallizes) at 130 degrees Fahrenheit
and is
supercooled while contained within the chamber. Supercooling may be achieved
by
melting all crystals (accomplished, e.g., by immersing in a sufficiently hot
liquid, oven,
autoclave, or microwave energy source) and allowing the solution to cool. The
supercooled liquid may be made to crystallize by introducing a metallic nidus
for
crystallization. As the supercooled liquid, crystallizes, its temperature
increases to the
to freezing point of 130 degrees Fahrenheit. This heat may then be conducted
across the
receptacle wall 14 to heat the fluid contained within the fluid receptacle 12.
Other suitable supercooled solutions include lead acetate, calcium nitrate
tetrahydrate, sodium pyrophosphate, sodium thiosulfate, and trimethylol ethane
hydrate. Chemical heating from within the chamber 20 may also be achieved by
using
other agents, for example calcium chloride that can be activated by water. It
is
particularly advantageous to provide heating substances that can be reused
simply by
autoclaving or otherwise heating the container to reactivate them.
FIG. 7 shows one embodiment of an activation assembly 24 adaptable for use
in the present invention. This figure shows a cross-section of a wall of the
solution
2o warmer system 10. The chamber 20 is shown, wherein heating substance may be
placed ready for activation. The activation assembly 24 as shown here uses a
plunger
tip 32 as the nidus for crystallizing the supercooled liquid contained within
the
chamber 20. According to the illustrated embodiment, pressure may be exerted
upon
the plunger plate 28 to propel the plunger tip 32 through an aperture 30 that
has been
previously sealed. As the plunger tip 32 is urged into the aperture 30, it
breaks the
seal. The aperture 30 is dimensionally adapted so that it will receive the
plunger rod 34
in an airtight fit. The fit of the plunger rod 34 within the aperture 30
effectively seals
the chamber 20 so that none of the heating substance can escape. Once the
plunger tip
32 comes into contact with the heating substance, crystallization will take
place, with
3o the production of heat as previously described.
In the depicted embodiment, the plunger system may be removable so that a hot
solution of sodium acetate or similar heating substance can be installed into
the
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-13-
chamber 20 through the aperture 30, following which the aperture 30 may be
sealed.
The plunger system may be then reinstalled and positioned so that it can be
activated
with finger pressure to penetrate the sealed aperture 30 and thus contact the
heating
substance to initiate crystallization. Other systems using similar plunger
type
mechanisms may also be designed in keeping with the spirit of this invention.
A
variety of plunger materials and surface finishes can be envisioned that may
facilitate
piercing the sealed aperture 30 or that may more advantageously activate the
heating
solution.
The plunger apparatus or similar activation assembly 24 may be positioned on
1o any surface of the solution warmer system 10. Although the activation
assembly 24 is
shown in this figure as if situated on the top of the system 10, it can just
as readily be
positioned on the side or on the bottom to permit easy access. Although the
depicted
system 10 as shown in these figures illustrates a chamber 20 into which a
heating
substance may be directly poured, it is understood that a heating substance
may be
installed in the warmer system pre-contained within a bag, a box or some other
container that could be penetrated by the activation assembly 24 in order to
produce
heat.
FIG. 8 depicts an embodiment of a solution warmer 10 configured as a pourable
pitcher 42. In the depicted embodiment, fluid is retained within a fluid
reservoir 48,
2o having been poured through a spout 58. Surrounding the fluid reservoir is
an inner
wall 50 adjacent to which activatable heating substance 44 such ~as sodium
acetate
crystals integrated in the container wall is directly applied. Surrounding the
heating
substance 44 is an outer wall 52 that also serves an insulating function. This
embodiment features a handle 54 that would allow fluids within the fluid
reservoir 48
to be easily poured through the spout 58 as needed. A variety of lids (not
shown),
hinged, press fit, screwtop, latched, or otherwise, may be constructed
appropriately for
the dimensions of the spout 58. In the illustrated embodiment, the warming
capability
is integrated directly into the pouring container, allowing freedom to
dispense solutions
directly and easily.
3o The pourable pitcher 42 shown in FIG. 8 can be made disposable with cheap,
injection-molded materials, or it can be made reusable by employing more
durable
plastics or metal materials. Materials may include nylons, polyethylene,
vinyl, and
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-14-
other plastics or ceramics familiar to skilled artisans, or may include metals
such as
stainless steel, titanium or others. As with the previously depicted
embodiment, a
variety of activation mechanisms are available. For example, activation can be
by a
metal disk that is brought into contact with the heating substance 44. Or, for
example,
a plunger mechanism may be used. Triggers may be placed on the handle 54 that,
upon depression, urged the activating element into the heating substance.
FIG. 9 depicts a solution warmer 10 according to the present invention
configured as a pourable pitcher 42 featuring an air activation mechanism 60
attached
to the handle 54. It has been demonstrated that exposure to air has the
ability to initiate
1o crystallization of supercooled sodium acetate solution and other
activatable heating
substances. The air activation mechanism 60 depicted herein is predicated upon
this
observation. In this figure, a rubber diaphragm 64 is shown covering an
opening (not
shown) in the outer wall 52. The trigger arm 62, when pulled, urges forward a
hollow
plunger 68 that penetrates the rubber diaphragm 64. This allows the inflow of
a
controlled amount of air, based upon the dimensions of the hollow interior of
the
hollow plunger 68. This embodiment also permits filling or refilling of the
heating
substance through the outer wall 52, with the opening used for filling being
coverable
by the rubber diaphragm 64. In the depicted embodiment, controlled activation
of the
heating substance is available without use of a metal disk or rod that might
migrate
2o around within the container or need to be physically deform. A variety of
trigger in
plunger mechanisms may be used to allow controlled exposure of air into the
heating
substance. Other containers, such as PVC bags containing sodium acetate can
also be
activated by air by using other systems, such as a manual open and close valve
or
check valve (one-way valve) to let air into the bag. This embodiment is
illustrated with
a hinged lid 70; as will be appreciated by skilled practitioners, a variety of
lids and
stoppers may be substituted.
FIG. 10 shows another embodiment of an activation assembly adapted for use
in the present invention. This figure shows a cross section of a wall of the
solution
warmer system 10. The chamber 20 is shown wherein an activatable heating
substance
3o may be placed ready for activation. An initiator 100 includes a metal
spring 102 as the
nidus for crystallizing the activatable heating substance contained within the
chamber
20. The spring 102 is stretched across an opening of the chamber 20 and the
ends of
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-15-
the spring suitably anchored. A flexible membrane 104 is applied across the
opening
in the chamber 20, enclosing the spring 102 such that the chamber 20 is
sealed.
According to the illustrated embodiment, pressure may be exerted on spring 102
through the flexible membrane 104 causing the spring 102 to flex. The flexing
of the
' spring 102 initiates crystallization in the activatable heating substance.
FIG. 11 shows another embodiment of an activation assembly adapted for use
in the present invention. This figure shows a cross section of a wall of the
solution
warmer system 10. The chamber 20 is shown wherein activatable heating
substance
may be placed ready for activation. An initiator 100 includes a metal disc 108
as the
l0 nidus for crystallizing the activatable heating substance contained within
the chamber
20. The disc 108 is disposed in an opening in the chamber 20 and the edge of
the disc
suitably anchored. A flexible membrane 104 is applied across the opening in
the
chamber 20 such that the chamber 20 is sealed.. According to the illustrated
embodiment, pressure may be exerted.on the disc 108 through the flexible
membrane
104, causing the disc 108 to flex. The flexing of the disc 108 initiates
crystallization in
the activatable heating substance.
FIG. 11A shows another embodiment of an activation assembly adapted for use
in the present invention. This figure shows a cross section of a wall of the
solution
warmer system 10. The chamber 20 is shown wherein activatable heating
substance
2o may be placed ready for activation. A screw 110 penetrates the chamber,20
through a
threaded hole. The screw has a noninsulated proximal end 112 and an
electrically
insulated distal end 114. The proximal end 112 may have bare metal, which
provides
the nidus for crystallizing the activatable heating substance contained within
the
chamber 20. The screw 110 is partially threaded into a hole in the chamber 20.
The
threads can be molded into the wall of the chamber 20 or a standard nut can be
spin
welded or otherwise mounted onto the chamber wall.
The screw 110 may be a metal screw, comprising preferably aluminum or
stainless steel. The electrically insulating material disposed on the distal
end 114 may
be any suitable electrically insulating material, and is preferably a polymer
coating on
the distal end 114. The screw 110 and female threads are dimensioned to
provide
sufficient interference to make an airtight hermetic seal. There may be
optionally
applied a coating or an additional section of a different material to the
female threads to
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-16-
ensure the seal is completely airtight during all shipping and sterilization
processes.
Alternatively, the screw can be non-metal and contain an insert or coating of
a suitable
activating material. An example of such embodiment is a plastic screw with a
metal
insert capable of activating the warmer when the insert contacts the solution.
During
manufacture, the screw 110 is partially screwed into the chamber wall such
that only
the electrically insulated distal end protrudes into the chamber and contacts
the
activatable heating substance. This screw insertion may take place while the
activatable heating substance is still well above its melt temperature.
With reference to FIG. 11B, the solution warmer may be activated by turning
the screw 110, thereby causing the proximal end 112 of the screw 110 to enter
the
chamber 20. Once the proximal end 112 enters the chamber 20 and contacts the
activatable heating substance, the surface energy associated with the metal
provides the
energy of crystallization required to begin the desired exothermic reaction.
FIG. 12 shows yet another embodiment of a surgical fluid warmer. In this
is embodiment a bag 118 containing activatable heating substance is provided.
A bowl
fits within the sleeve 22 of the warmer 10, thereby defining a chamber 20. A
bag 118
containing an activatable heating substance occupies the chamber 20. When
heating is
desired, the activatable heating substance is activated inside the bag 118 in
any manner
described herein or in, e.g., U.S. Patents Nos. 5,791,334, 5,736,110,
5,058,563,
5,056,589, 4,899,727, 4,872,442, 4,860,729, 4,829,980, 4,587,950, 4,572,158,
and
4,077,390, the disclosures of which are incorporated herein by reference. The
bowl is
placed on top of the bag 118. Surgical fluid may introduced into the bowl at
any time.
In this embodiment the bag 118 may be replaced during a procedure to prolong
the
heating action of the warmer.
Although the apparatus, systems and methods described herein may be adapted
for deployment in a sterile field, they may also be deployed in a nonsterile
field. They
may also be maintained in a nonsterile field that was formerly sterile.
Any of the above embodiments may be further insulated to prolong heating
capacity by the addition of an insulating sleeve 22 around the fluid warmer.
Such
3o insulating sleeve 22 can be made from any suitable insulating materials
including but
not limited to neoprene, Styrofoam or urethane. Additionally, insulation can
be
incorporated into the fluid warmer body or an air space provided for
insulation.
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-17-
In an embodiment, supercooled sodium acetate is used as the activatable
heating substance. When activated, the supercooled sodium acetate is an
exothermic
energy source. In an embodiment, the concentration of the sodium acetate
solution is
between about 10 to about 20 molar, preferably between about 17 and about 18
molar,
more preferably about 17.68 molar. As will be appreciated by one of skill in
the art,
molarity of the solution can be adjusted to vary the heating profile.
Example 1
A surgical warmer as disclosed above was constructed containing 400 ml of
to supercooled 17.68 molar sodium acetate solution. 500 ml of water pre-warmed
to 98.6
degrees Fahrenheit was added to the container and the activatable heating
substance
activated. The external walls and lid of the warmer were insulated with a one-
quarter
inch insulating neoprene sleeve. The warmer achieved a heating profile as
shown in
FIG. 13. The warmer maintained the solution at a temperature equal to or
greater than
15 100 degrees Fahrenheit for a duration equal to or greater than about 4
hours.
Example 2
A surgical warmer was constructed as disclosed above containing 1250 ml of
supercooled 17.68 molar sodium acetate solution. 800 ml of water at 68.5
degrees
2o Fahrenheit was added to the container and the activatable heating substance
activated.
The external walls and lid of the warmer were insulated with a one-quarter
inch
insulating neoprene sleeve. The warmer achieved a heating profile as shown in
FIG.
14. The warmer warmed the solution to a temperature equal to or grater than
100
degrees Fahrenheit in a time period less than 1 hour and maintained the
solution at a
25 temperature equal to or greater than 100 degrees Fahrenheit for a duration
equal to or
greater than about 4 hours.
It will be understood that embodiments of the invention described above are
illustrative of some of the applications and principles of the present
invention. Various
modifications may be made by those skilled in the art without departing from
the spirit
3o and scope of the invention. Furthermore, although the present invention has
been
illustrated by reference to embodiments usable in a medical setting, the
solution
warmer system and activation assembly are adaptable to a variety of non-
medical
CA 02413696 2002-12-23
WO 02/07656 PCT/USO1/22694
-18-
purposes, as will be evident to those of ordinary skill in the art. For
example, a
pourable pitcher as described above could be used with some modification to
keep
other liquids warm. A person of ordinary skill in the art could adapt the
systems
described herein to produce, for example, an insulated container to incubate a
beverage. Accordingly, the invention is not to be limited to the illustrated
embodiments provided above, but is to be understood by the claims set forth
below,
which are to be interpreted as broadly as allowed by law.
We claim:
