METHOD AND SYSTEM FOR TREATING HIGH INTRACRANIAL PRESSURE
USING HYPOTHERMIA
RELATED APPLICATIONS
Priority is claimed from co-pending U.S. patent application serial no. 09/266,452,
filed March 11, 1999.
FIELD OF THE INVENTION
The present invention relates to methods and systems for lowering intracranial
pressure (ICP).
BACKGROUND
High intracranial pressure (ICP) is a major complication of severe head injury and
many other pathologies, including brain tumors, acute hydrocephalus, craniosynostosis and
benign cranial hypertension. It is believed that as a result of cellular injury and the brain's
inflammatory process, the brain can swell, increasing ICP. Since ICP is the difference
between mean arterial blood pressure and cerebral perfusion pressure (CPP), high ICP
generally means low CPP, which can lead to a risk of ischemia (lack of oxygen to the brain).
In any case, it is widely believed that an elevated ICP is closely correlated to poor medical
outcomes.
It has been discovered that the medical outcome for a patient suffering from high ICP
can be improved by lowering ICP using hypothermia, i.e., by lowering ICP below about 20
mm Hg by cooling the patient below normal body temperature (38°C). As understood by the
present invention, the medical outcome for many such patients might be significantly
improved if the patients were to be mildly or moderately cooled to 32°C-37°C relatively
quickly for a short period, e.g., 12-72 hours.
Currently, to the extent that hypothermia is used to lower ICP, cooling blankets, ice
lavages, or other external means are used. As understood herein, however, such cooling
methods are difficult to control, are typically somewhat slow to cool the patient, and being
applied to the skin can cause a natural shivering reaction which increases ICP considerably
and which consequently should be avoided for patients suffering from high ICP.
Systems and methods have been disclosed that propose cooling blood flowing to the
brain through the carotid artery. An example of such systems and methods is disclosed in co-
pending U.S. pat. app. serial no. 09/063,984, filed April 21, 1998, owned by the present
assignee and incorporated herein by reference. In the referenced application, various
catheters are disclosed which can be advanced into a patient's carotid artery and through
which coolant can be pumped in a closed circuit, to remove heat from the blood in the carotid
artery and thereby cool the brain. The referenced devices have the advantage over other
methods of cooling (e.g., wrapping patients in cold blankets) of being controllable, relatively easy to use, and of being capable of rapidly cooling and maintaining blood temperature at a
desired set point.
As recognized in co-pending U.S. pat. app. serial no. 09/133,813, filed August 13,
1998, owned by the present assignee and incorporated herein by reference, the above-
mentioned advantages in treating high ICP by internal cooling can also be realized by cooling
the patient's entire body, i.e., by systemic, internally-induced hypothermia. The advantage of
systemic hypothermia is that, as recognized by the present assignee, to induce systemic
hypothermia a cooling catheter or other cooling device need not be advanced into the blood
supply of the brain, but rather can be easily and quickly placed into the relatively large vena
cava of the central venous system. Moreover, since many patients already are intubated with
central venous catheters for other clinically approved purposes anyway, providing a central
venous catheter that can also cool the blood requires no additional surgical procedures for
those patients. A cooling central venous catheter is disclosed in the present assignee s co-
pending U.S. patent applications serial nos. 09/253,109, filed February 19, 1999 and
09/305,613, filed May 5, 1999, both of which are incorporated herein by reference.
SUMMARY OF THE INVENTION
A method for treating high ICP in a patient includes determining that the patient has a
high ICP, and in response lowering the patient's temperature using at least one catheter
placed in the venous system of the patient.
In a preferred embodiment, the method can also include elevating the patient's head,
and/or hyperventilating the patient, and/or draining cerebral spinal fluid from the patient as
necessary to lower ICP. Moreover, if necessary the method can include administering one or
more of: a sedative, a paralytic, a diuretic, and a barbiturate, to the patient to lower ICP.
In another aspect, a system for treating elevated pressure in a patient's head includes
at least one catheter having a heat exchange region on a distal portion thereof, and at least
one pressure probe advanceable into the patient to provide a signal representative of ICP.
The details of the present invention, both as to its structure and operation, can best be
understood in reference to the accompanying drawings, in which like reference numerals
refer to like parts, and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view of the cooling system using the first cooling catheter;
Figure 2 is a schematic view of the cooling system using the second cooling catheter;
and
Figure 3 is a flow chart of the present invention for treating high ICP in a patient.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring initially to Figure 1, a therapeutic system, generally designated 10, is shown
for treating high ICP in a patient 12. As shown, the system 10 includes a cooling system 14
that can be a water-bath system such as the system disclosed in the present assignee's co-
pending U.S. patent application serial no. 09/220,897 filed December 28, 1998 and
incorporated herein by reference, or a cooling system including at least one thermal electric
cooler (TEC) 16, as disclosed in the present assignee's co-pending U.S. patent application
serial no. 09/260,950, filed March 2, 1999 and incorporated herein by reference. In any case,
the cooling system 14 can be considered a source of coolant, preferably sterile saline, for the
catheters of the present invention.
As set forth in these applications, the cooling system 14 can include a heat exchanger,
a pump, and, if desired, a controller. Preferably, the pump is a peristaltic pump, but other
types of positive displacement pumps, such as but not limited to piston pumps and gear pumps, or even centrifugal pumps, can be used. A peristaltic pump is preferred in the
present implementation because it can pump coolant without directly contacting the coolant,
but instead simply by squeezing a tube through which the coolant flows. In this way, the
pump is reusable, and only the present catheters and portions of the system 10 coming in
direct contact with the coolant need be made disposable to render an advantageously
disposable and sterile coolant delivery system. The controller controls the rate at which
coolant is pumped by the pump and, if desired, the rate at which heat is added or subtracted
from the coolant. The controller can be implemented by a software-executing processor or
by discrete logic circuits or other electronic circuitry device to establish a desired patient temperature by appropriately controlling the pump and/or heat exchanger in response to a
temperature signal derived from a sensor in the patient 12.
As shown in Figure 1 , a first cooling catheter 18 can communicate with the cooling
system 14 via coolant supply and return lines 20, 22. The coolant lines 20, 22 can be IV lines
or tubes or other suitable fluid conduits, such as metal (steel) tubes. When the coolant lines
20, 22 are plastic tubes, they can be connected to the catheter 18 and the cooling system 14
by suitable connecting structure, such as Luer fittings, interference fits, solvent bonding, heat
staking, ultrasonic welding, and the like.
The first cooling catheter 18 includes a heat exchange region 24. The heat exchange
region 24 can be established by one or more hollow fibers, as disclosed in the above-
referenced U.S. patent application serial no. 09/133,813. Alternatively, the heat exchange
region 24 can include one or more cooling membranes such as balloons as disclosed in the above-referenced U.S. patent application serial nos. 09/253,109 and 09/305,613. For
example, the heat exchange region 24 of the first catheter 18 can be established by four
axially staggered balloons, each ten millimeters in diameter when inflated with coolant.
In any case, as set forth in the referenced applications, coolant is circulated in a closed
fluid communication loop between the heat exchange region 24 and cooling system 14 to
remove heat from the patient 12. As set forth in greater detail below, the first catheter 18 is
advanced (preferably through an introducer sheath) into the vena cava of the patient 12
through a groin entry point 26 to establish hypothermia in the patient 12. Preferably, the
catheter 18 is advanced either through the saphenous vein or femoral vein.
In addition to or in lieu of the first catheter 18, a second cooling catheter 28 (Figure 2)
which is configured for use as a central venous catheter can be advanced into the central
venous system of the patient through a neck entry point 29. The second catheter 28 can be
embodied by the catheter disclosed in the above-referenced patent application serial nos.
09/253,109 and 09/305,613. Accordingly, the second catheter 28 can communicate with the
cooling system 14 via coolant supply and return lines 30, 32. Also, the second catheter 28
can communicate with one or more central venous components 34, such as IV infusion
devices, drug delivery syringes for infusing epinephrine, blood withdrawal devices, and so
on. The component 34 can also be established by a device such as a syringe for infusing a
diuretic such as Mannitol into the patient, or for administering sedatives or paralytics to the
patient. Also, the component 34 can be used to administer barbiturates to the patient.
As disclosed in the referenced applications, the second catheter 28 includes a heat
exchange region 36 that can be established by one or more membranes such as balloons,
although it could be established by hollow fibers in the manner of the catheter 18, but on a
smaller scale. The catheter 28 can be advanced into the superior vena cava through the
jugular vein or subclavian vein to cool the patient 12 by means of coolant circulating in a closed loop between the cooling system 14 and the balloon 36. As mentioned above, the
second catheter 28 can also be used to undertake conventional central venous catheter
functions.
Referring back to Figure 1 , in addition to the cooling components discussed above,
the system 10 can include a cerebral spinal fluid (CSF) drainage system, represented by a box
38, that is coupled to the patient via a line 40 that communicates with the patient's spine or
brain cavity for draining excess CSF from the patient. Also, a ventilation system 42 can be
connected to the patient 12 via a tube 44 to hyperventilate the patient.
As understood by the present invention, one way to measure ICP is to advance a pressure probe 45, shown schematically in Figure 2, into the head of the patient 12. The
pressure probe 45 can include a pressure sensor 45a on the distal end of the probe 45, with
the sensor 45a being connected to a pressure indicator 45b that indicates ICP. Alternatively,
the pressure probe 45 can be advanced into the neck of the patient to position the sensor 45a
in the jugular vein of the patient. In either embodiment, the pressure sensor 45a generates a
pressure signal that represents a measure of ICP.
Figure 3 shows the details of a preferred method for treating high ICP in the patient
12. As indicated at block 46, hypothermia is induced by advancing the first catheter 18
through the groin into the vena cava, and then circulating coolant through the first catheter
18. Once target temperature of 32°C-37°C has been reached, the first catheter 18 can be
removed and the second catheter 28 advanced into the vena cava through a neck entry point
to maintain target temperature. It is to be understood that while this is one preferred
sequence of the order of steps for inducing hypothermia in a high ICP patient, other
sequences can be used. For example, the first catheter 18 can be used exclusively to the
second catheter 28, the second catheter 28 can be used exclusively to the first catheter 18, or
both catheters 18, 28 can be used together simultaneously.
Moreover, as indicated at block 47 in Figure 3, if desired hypothermia can be induced
after first receiving the pressure signal from the sensor 45 a. If desired, either one or both of
the catheters 18, 28 can be prepositioned in the patient, with cold coolant flow through the
heat exchange regions of the catheters being established only after high pressure is sensed.
The cold coolant flow can be established manually by a person after observing a high
pressure reading on the indicator 45b, or it can started automatically. In such a system, the
signal from the pressure sensor 45 a (or a signal from a circuit component that is activated by
a predetermined high pressure signal from the sensor 45a) can be input to the above-
mentioned controller of the cooling system 14 to activate the above-mentioned system pump
or to cause the above-mentioned cooling components to lower the temperature of the coolant
flowing through the catheters 18, 28, or both.
In any case, in addition to establishing hypothermia using the catheters of the present
invention, the preferred method also contemplates elevating the head of the patient at block
48 by, e.g., thirty degrees or so. If ICP remains above a predetermined threshold pressure,
e.g., 20mm Hg as indicated by the pressure indicator 45b, the patient can be sedated and/or
paralyzed at block 50 by infusing a sedative or paralytic into the patient using, e.g., the
component 34 and second catheter 28 shown in Figure 2.
If ICP still remains above the threshold pressure, at block 52 cerebral spinal fluid
(CSF) can be drained from the patient using the CSF system 38 shown in Figure 1. If ICP
still remains high, a diuretic such as Mannitol can be administered at block 54 through, e.g.,
the second catheter 28 using a syringe as the component 34. Should ICP still remain high,
the ventilation system 42 shown in Figure 1 can be used to hyperventilate the patient at block
56. In the event that hyperventilation fails to lower ICP sufficiently, at block 58 barbiturates
can be administered using, e.g., the component 34 and second catheter 28 shown in Figure 2.
If necessary, at block 60 appropriate surgery can be performed to alleviate the high ICP.
The above method acts are set forth in the presently preferred order, it being
understood that the method acts could be performed in other orders as determined to be
-in¬
appropriate. In any case, it is to be appreciated that as represented by the arrows 62,
hypothermia can be induced during some or all of the above method acts, or in lieu thereof.
While the particular METHOD AND APPARATUS TREATING HIGH INTRACRANIAL PRESSURE USING HYPOTHERMIA as herein shown and described in
detail is fully capable of attaining the above-described objects of the invention, it is to be
understood that it is the presently preferred embodiment of the present invention and is thus
representative of the subject matter which is broadly contemplated by the present invention,
that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is
accordingly to be limited by nothing other than the appended claims, in which reference to an
element in the singular is not intended to mean "one and only one" unless explicitly so stated,
but rather "one or more". All structural and functional equivalents to the elements of the
above-described preferred embodiment that are known or later come to be known to those of
ordinary skill in the art are expressly incorporated herein by reference and are intended to be
encompassed by the present claims. Moreover, it is not necessary for a device or method to
address each and every problem sought to be solved by the present invention, for it to be
encompassed by the present claims. Furthermore, no element, component, or method step in
the present disclosure is intended to be dedicated to the public regardless of whether the
element, component, or method step is explicitly recited in the claims. No claim element
herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase "means for".