thermogard_xp_physicians_manual_rev_3.pdf
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IVTM
TM
Intravascular Temperature
Management
PHYSICIAN MANUAL
Caution: Federal law restricts this device to sale by or on the order of a physician.
600248-001 Rev. 3
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Physician Manual Rev. 3
Copyright © 2011 ZOLL Circulation, Inc.
All rights reserved. Printed in U.S.A.
Trademarks
Alsius, CoolGard, CoolGard 3000, Thermogard XP, IVTM, Cool Line, Solex,
Quattro, and Icy are registered trademarks of ZOLL Circulation, Inc.
Mallinckrodt is a registered trademark of Mallinckrodt Inc.
Windows is a registered trademark of Microsoft Corporation.
Other products and names listed in this document may be trademarked by their
owners and no representation is made by ZOLL Circulation, Inc. as to rights thereto.
ZOLL Circulation, Inc
650 Almanor Avenue
Sunnyvale, California
U.S.A.
Telephone:
Facsimile:
+1-408-541-2140
+1-408-541-1030
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Contents
Introduction 5
Scope 5
Cool Line Catheter - Indications for Use 6
Warning – Fever Reduction 6
Icy, Quattro and SolexCatheters - Indications for Use 6
Thermoregulation 7
Normal Control of Body Temperature 7
Central Set-Point 7
Peripheral Responses 8
Summation of Peripheral and Central Sensory Signals 8
Increased Body Temperature 8
Thermal Regulation and Disease States 8
Pyrogens 8
Cerebral Injury 9
This Product in its Environment 10
Introduction 10
Treatment Algorithms 10
Max Power (MAX) 10
Controlled Rate 10
FEVER (FVR) 11
Warming (Warm) 11
The Patient Environment 11
Cool Line Catheter 13
Fever Management – The Standard of Care 13
Standard Methods of Fever Reduction 13
Fever Reduction Clinical Study 14
Clinical Study Summary 14
Objective: 14
Materials and Methods: 14
Results: 14
Clinical Study Results in Detail 15
Significant Reduction in Fever Burden 15
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Complications 17
Specific Use Effects 19
Obvious Fever 19
Masked Fever vs. Steady State 19
In Summary 20
Icy, Quattro & Solex Catheters 21
Cardiac Surgery 21
Afterdrop 21
Fast-Track Recovery After Cardiac Surgery 21
Rewarming Post-Cardiac Surgery 22
Neurosurgery 22
Operative Hypothermia 22
Rewarming 23
Catheter Selection 23
Specific Use Effects 25
Cardiac Function 25
Bradycardia 25
Arrhythmia 25
Lung Function 26
Sepsis 26
Infection 26
General Risks of Central Line Usage 27
Caveats to CVC Placement (CVC-WG) 27
Infection 28
Specific Operational Issues 30
Stop the Pump 30
Air Bubble Detector 30
Fluid Loss Detector 31
To check the integrity of the catheter: 31
To check the integrity of the tubing set: 31
Cool Line Catheter – Two Functions 32
Seven Days – Cool Line Catheter Only 32
“Dead Head” Pressure 32
Water and Propylene Glycol 32
Dual Temperature Probes 33
Single Use/Service Life 33
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Check the Pinwheel 33
References 34
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Introduction
Scope
This manual applies to the ZOLL Intravascular Temperature Management (IVTM™)
System which consists of both the CoolGard 3000® and the Thermogard XP®
Consoles and IVTM Catheters. It is intended to provide pertinent clinical information
to physicians as they use the IVTM System.
This manual should be read in conjunction with the Operation Manual for the IVTM
System. It is not intended to provide sufficient information to the untrained user to
understand the safe operation of the IVTM System. Please consult the Operation
Manual for the IVTM System and the Instructions For Use for the IVTM Catheters
prior to use.
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Cool Line Catheter - Indications for Use
®
The IVTM System and Cool Line Catheter is indicated for use in fever reduction, as
an adjunct to other antipyretic therapy, in patients with cerebral infarction and
intracerebral hemorrhage who require access to the central venous circulation and
who are intubated and sedated.
Warning – Fever Reduction
The safety of this device has not been demonstrated for fever reduction in patients
presenting with subarachnoid hemorrhage or primary traumatic brain injury. The
safety and effectiveness of this device was examined in a randomized controlled
trial of 296 patients. The mortality results reported in this trial, for the four patient
cohorts enrolled, are presented in the table below (CI – cerebral infarction, ICH –
intracerebral hemorrhage, PTBI – primary traumatic brain injury, SAH – subarachnoid
hemorrhage).
Mortality by Diagnosis (ITT)
Cool Line
Control
n
N
%
n
N
%
p-value*
CI
3
16
18.8
3
14
21.4
0.74
ICH
8
33
24.2
7
27
25.9
1.00
PTBI
10
44
22.7
4
38
10.5
0.24
SAH
13
61
21.3
7
63
11.1
0.15
*Fischer’s exact test
For more details on the results of this study please refer below to the section on
Clinical Experience.
Icy , Quattro & Solex Catheters - Indications for
Use
®
®
®
The IVTM System, using either the Icy , Quattro or Solex Catheters, is indicated for
use:
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in cardiac surgery patients to achieve and or maintain normothermia
during surgery and recovery/intensive care, and,
•
to induce maintain and reverse mild hypothermia in neuro surgery
patients in surgery and recovery/intensive care.
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Thermoregulation
Human beings are mammals: as such their physiology operates to set and maintain
o
o
body temperature within a narrow band about a set-point, nominally 37 ± 1 C.
Normal Control of Body Temperature1
The body temperature is a reflection of the equilibrium state between the body and its
o
o
environment. Within an environmental range of approximately 13 C to 54 C, a normal
o
unclothed human can maintain a core body temperature somewhere between 36 C
o
and 37.9 C [1].
Heat is generated within the body via chemical and physical processes of the body.
The physical processes include both bodily activity and cellular respiration. Heat is a
byproduct of cellular respiration–most of this heat is generated in skeletal muscle
and, to a lesser extent, in brown fat and in the liver. Seventy five percent or more of
total energy input is released back to the environment directly as heat (depending
upon the level of physical activity). Shivering is a specific example of muscular
activity to produce heat.
Heat loss is via conduction to materials in direct contact with the body, via convection
to the air, and via infrared emissions. We use clothing to help minimize this heat loss.
Respiration and sweating are specific evaporative/ convective mechanisms (heat is
conducted to the surface layer of water where it then drives a phase change–the
movement of unsaturated air accelerates the process); the latter being specifically
variable in response to body temperature. Typical sources of human heat loss in a
room at normal temperatures are shown in the table below [1].
Table 1. Human Heat Loss by Source.
Source
Percent
Radiation
60%
Evaporation
22%
Conduction to objects
3%
Convection/conduction to air
15%
In general, humans have a central control mechanism that seeks to maintain body
temperature in reference to a set-point. This set-point can be varied by both internal
and external mechanisms. For a given set-point, the body will act to maintain a
temperature (see following). For example, with a fever, attempts to withdraw heat will
be resisted until the set-point for that febrile body temperature is reset.
Central Set-Point
Temperature regulation is centered in the hypothalamus. The preoptic area of the
hypothalamus seems to serve as the thermostatic center for the body.
1 Unless otherwise stated, the general references used in this chapter are
Guyton and Hall, 2001 [1] and Schonbaum and Lomax, 1991 [2].
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Peripheral Responses
The skin carries sensory receptors to both cold and heat; although, the cold sensors
are ten times more numerous. These cutaneous temperature sensors serve as a
strong stimulus to shivering and serve to increase or decrease both sweating and
vasodilatation. The response of the sensors is dominated by their response to cold.
Summation of Peripheral and Central Sensory Signals
The posterior hypothalamus receives signals from both the peripheral temperature
sensors and from the preoptic area of the hypothalamus. The signals are integrated
and central control signals are sent to the skin to modify sweating, vasodilatation, and
piloerection.
The dorsomedial portion of the posterior hypothalamus is normally inhibited by the
preoptic portion and excited by cutaneous cold sensors. Excitation of this area due to
cold leads to stimulation of muscle cells via the lateral columns. This action increases
the resting tone of the muscle, which triggers the stretch reflex. The resulting
contraction pattern is an oscillation between opposing muscle groups with no purposeful movement.
Increased Body Temperature
The body’s temperature increases either from increased heat generation (cellular
respiration or shivering), or reductions in skin losses. Increased cellular respiration at
rest is possible by two mechanisms: chemical thermogenesis and thyroxine-mediated
increases in the metabolic rate.
Chemical thermogenesis in adult humans (who lack brown fat) is limited to no more
than 10–15% of the basal metabolic energy output. It is the result of the uncoupling
of oxidative phosphorylation in response to circulating norepinephrine and
epinephrine.
In a cold environment, significant increases in thyroxine level and therefore metabolic
drive, do occur. However this is a long-term adaptation and is of little consequence in
discussing the short-term regulation of body temperature.
For the intubated and sedated patient:
•
Shivering is pharmacologically damped or lost.
•
Central control, driven by the summation of peripheral and central
sensory input, is reduced or lost.
•
Disturbed hypothalamic function can directly reset the temperature setpoint.
Thermal Regulation and Disease States
Fever is a response to either endogenous or exogenous pyrogens, or direct effects
upon the hypothalamic temperature control centers.
Pyrogens
Endogenous pyrogens are families of polypeptides (e.g., interleukin 1) that are
produced by macrophages, monocytes, and other white cells. They are mediators of
inflammation. They act centrally upon the hypothalamus to modify thermoregulation.
The typical fever response shows an initial abrupt rise in core temperature to a peak
(acute phase response) with a more gradual decay to normothermia. Endogenous
pyrogens do not appear to have other than central effects upon thermoregulation.
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Exogenous pyrogens are polypeptides of origin external to endogenous pyrogens but
of similar action.
Cerebral Injury
Sustained changes in the thermoregulatory set-point are observed with irritation or
compression (tumor) of the hypothalamus. In addition, intra-cerebral release of
endogenous pyrogens (cerebral inflammation) can have the same effect. The
hypothalamus is exposed to cerebrospinal fluid as well as to blood, so it can be
subject to the action of CSF-borne pyrogens [2].
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This Product in its Environment
Introduction
The first law of thermodynamics can only be applied after defining the system. For
our purposes the system consists of three elements:
1. The patient:
• Is intubated and sedated.
• Is warmer than the environment and therefore will lose heat to the
environment.
• Will lose more heat to the environment if wet than if dry.
2. The environment. This is typically controlled by air conditioning that is far
more powerful than the patient (i.e., it will react to overcome any heat the
patient adds to the environment). Within this discussion, outside of the
performance of the IVTM System , the single most significant effect upon
the patient is the rate of heat loss to the environment.
NOTE: When comparing catheter performance, only results obtained
from controlled in-vitro methods should be used. Heat exchange to the
environment within the clinical setting can be significant and variable
depending upon environmental conditions and the degree to which the
patient is able to maintain his/her body temperature.
3. There are two heat transfers that occur in the IVTM System:
•
Between the fluid in the cold well of the IVTM System and the saline
in the coil of the Start-Up Kit.
•
Between the saline in the catheter balloons and the blood of the
patient.
The IVTM System responds to both the difference between the patient’s temperature
and the set-point and to the rate of change of the patient’s temperature. The system
will add or remove heat to maintain the patient at the set-point.
Treatment Algorithms
There are four treatment algorithms in RUN: “Max Power”, “Controlled Rate”,
"Warming", and “FEVER”.
Max Power (MAX)
In this treatment option, the IVTM System seeks to make the patient’s temperature
the same as the selected target temperature. It will keep the saline pump operating
unless the patient’s temperature “inverts”. This occurs whenever:
A. Bath Temperature > Patient Temperature > Target Temperature,
OR
B. Bath Temperature < Patient Temperature < Target Temperature.
Controlled Rate
In this treatment option, the IVTM System will attempt to move the patient’s
temperature to the target temperature at the programmed rate of heat exchange (°C
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/hr). When the patient reaches the target temperature, the IVTM System will revert to
the MAX treatment option i.e. it will attempt to make the patient’s temperature the
same as the selected target temperature.
NOTE: Controlled Rate
Controlled rate operates in both warming and cooling modes.
FEVER (FVR)
In this treatment option, the IVTM System will starting cooling the patient once the
patient temperature is above the target temperature. It does this by keeping the bath
at its coldest permissible temperature and then operating the saline pump whenever
the patient’s temperature moves above the target temperature. Maximum cooling
power is always applied as with Max Power.
WARNING! “Lo” patient temperature alarm limit with “FEVER”
The IVTM System will NOT heat the patient when the “FEVER” treatment option
has been selected. The “Lo” patient temperature alarm limit ensures that an
alarm occurs should the patient stop regulating his/her own body temperature.
Such patients will cool to room temperature. This can occur when the patient
dies or becomes comatose.
INVESTIGATE ALL PATIENT TEMPERATURE ALARMS.
Warming (Warm)
In this treatment option, the IVTM System will start warming the patient once the
patient temperature is below the target temperature. It does this by keeping the bath
at its warmest permissible temperature and then operating the saline pump whenever
the patient’s temperature moves below the target temperature. Maximum warming
power is always applied as with Max Power.
WARNING! “Hi” patient temperature alarm limit with
“Warming”
The IVTM System will NOT cool the patient when the “Warming” treatment option
has been selected. The “Hi” patient temperature alarm limit ensures that an
alarm occurs should the patient become febrile.
INVESTIGATE ALL PATIENT TEMPERATURE ALARMS.
The Patient Environment
The patient is in equilibrium with his/her environment. The average human generates
between 75 and 100 watts of energy. Much of this is spent in simply keeping the
body hotter than the environment–heat is lost through convection/conduction to the
air and materials that touch the body (sweat facilitates this loss), heat is lost through
respiration, and heat is lost via infrared radiation.
The rate of heat loss, under normal conditions, is primarily affected by the ratio of the
surface area of the patient’s body to his/her weight. Think of the body as a stack of
cubes: some on the surface that can lose heat to the environment and others inside
that have no direct contact. Only the outside surfaces of the cubes that are the
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surface of the body can lose heat to the environment, yet all the cubes generate
heat.
The larger the patient, the less surface area there is per unit of volume by which to
lose heat. Smaller people heat more quickly for a given energy expenditure and lose
heat to a colder environment more quickly than a larger person starting from the
same body temperature.
When the IVTM System is active, heat is removed from the patient. In a febrile
patient, the amount of excess heat is the product of the temperature increase and the
thermal mass of the patient, unless the patient has as yet untapped reserves for heat
generation. The higher the temperature the patient is allowed to reach prior to
starting therapy, the longer it will take to return the patient to a normal temperature.
For a given patient, the stronger the endogenous drive to heat production, the longer
it will take to cool that patient. Larger patients will take longer to cool than smaller
patients because they have more thermal mass.
In some cases, the IVTM System may not have sufficient power to reduce the
patient’s temperature to normal levels. The use of the IVTM System does not
preclude the use of other antipyretic measures. For example, pharmacological agents
that can reduce the endogenous drive to increased temperature or any mechanisms
for increasing heat loss from the skin will still be of benefit.
1. It is important to use the IVTM System in conjunction with conventional
antipyretic measures.
2. Whenever possible, for antipyretic therapy, it is best to precool the IVTM
System prior to connection to the patient to optimize performance. This can
be done, for example, at the time that the patient is being prepared for
insertion of the central line.
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Cool Line Catheter
Fever Management – The Standard of Care
Fever management has become a standard of care in the neuro-ICU. According to
American Heart Association guidelines established for the management of patients
with acute ischemic stroke and spontaneous intracerebral hemorrhage, body temperature should be maintained at a normal level [3][4].
Standard Methods of Fever Reduction
Standard fever management in the majority of major medical centers in the U.S.
consists of antipyretic drug therapy using acetaminophen or ibuprofen, and
external/physical cooling. Physical cooling includes surface cooling with water or airfilled cooling blankets, ice packs, nasogastric or rectal lavage, or alcohol baths.
Pharmacological agents such as acetaminophen, aspirin, other nonsteroidal antiinflammatory agents, and corticosteroids appear to inhibit the febrile response by
inhibiting prostaglandin synthesis, thus interfering with prostaglandin-mediated action
on the hypothalamus. In most clinical practices, antipyretic drugs are often prescribed
to combat temperatures greater than 38.5°C.
External cooling by different methods, such as using rotary fans and sponging the
body surface with water, are also used.
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Fever Reduction Clinical Study
®
The CoolGard (Model 2060) was a predecessor to the CoolGard 3000 (Model
CoolGard 3000). The CoolGard 3000 has been cleared based upon the data
gathered with the CoolGard heat exchange system. The performance of the
CoolGard/Cool Line catheter system was studied as part of a clinical
investigation, entitled:
A Prospective, Randomized, Controlled Multicenter Clinical Study to Evaluate the
Safety and Effectiveness of the CoolGard System with Cool Line Catheter in
Reducing Fever in Neurointensive Care Unit Patients.
Clinical Study Summary
Objective:
To study the effectiveness of catheter based heat exchange systems in the reduction
of elevated temperatures in critically ill neurological and neurosurgical patients.
Materials and Methods:
This study was a prospective randomized, non-blinded trial in which conventional
treatment of fever with acetaminophen and water cooling blankets (conventional
group) (standardized across centers) was compared to conventional treatment plus a
catheter based heat exchange system (ZOLL Circulation, Inc., Sunnyvale, CA)
(catheter group). Four patient populations were included in the trial: subarachnoid
hemorrhage (SAH), intracerebral hemorrhage (ICH), ischemic infarction (CI) and
traumatic brain injury (TBI). To be eligible the patient’s temperature had to exceed
o
38 C on 2 occasions or for >4 hours and they had to require central venous access.
Temperature was recorded hourly for a minimum of 3 and up to 7 days following
randomization. The temperatures were graphed and the area under the fever curve
o
which exceeded 38.0 C was used as an index of fever burden. The efficacy of the
catheter based system was determined by its ability to reduce fever burden in an
intention to treat analysis. The safety of the catheter system was also examined.
Results:
A total of 296 patients were enrolled over 20 months half of which were randomized
to receive conventional fever management and half conventional management and
the catheter based heat exchange system. Of the patients 41% had SAH, 24% TBI,
23% ICH and 13% ischemic stroke. The two fever control groups were matched in
terms of age, body mass index, gender and overall GCS distribution. Fever burden
for the first 72 hours was 7.92 degree hours in the conventional group and 2.87
degree hours in the catheter group demonstrating a 64% reduction in fever burden
with the catheter system. There was no increase in infections or the use of sedatives,
narcotics or antibiotics in the catheter group.
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The safety of this device has not been demonstrated for fever reduction in patients
presenting with subarachnoid hemorrhage or primary traumatic brain injury. The
safety and effectiveness of this device was examined in a randomized controlled trial
of 296 patients. The mortality results reported in this trial, for the four patient cohorts
enrolled, are presented in the table below (CI – cerebral infarction, ICH –
intracerebral hemorrhage, PTBI – primary traumatic brain injury, SAH – subarachnoid
hemorrhage).
Table 2. Mortality by Diagnosis (ITT)
Cool Line
Control
n
N
%
n
N
%
p-value*
CI
3
16
18.8
3
14
21.4
0.74
ICH
8
33
24.2
7
27
25.9
1.00
PTBI
10
44
22.7
4
38
10.5
0.24
SAH
13
61
21.3
7
63
11.1
0.15
*Fischer’s exact test
Clinical Study Results in Detail
Significant Reduction in Fever Burden
The table below, Reduction in Fever Burden, provides the results of the study in
terms of its primary end-point for all patients using an intention to treat analysis.
There was an highly significant reduction in the fever burden when comparing the
use of the IVTM System with the standard methods of fever management.
Table 3. Fever Burden – ITT Data Set
Log Scale
Natural Scale
Cool Line
Control
Cool Line
Control
N
154
142
154
142
Mean
1.42
2.23
2.87
7.92
1.19 – 1.52
2.06 – 2.41
2.27 – 3.58
6.82 – 10.09
95% CI
p-value
% Reduction
64%
<0.0001
This result was obtained with a significant reduction in the use of topical cooling
devices and antipyretic medication use. These results in the following two tables.
The two graphs below present the mean temperatures, left justified over the study
period, for all patients within the Cool Line and Control cohorts.
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Cool Line Patients (Mean Temperature ± SD)
39
38.5
38
37.5
37
36.5
36
0
20
40
60
Hours
Control Patients (Mean Temperature ± SD)
39
38.5
38
37.5
37
36.5
36
0
20
40
60
Hours
The reduction in fever burden was accompanied by a reduction in the use of
adjunctive cooling means as presented in the tables below.
Table 4. Use of Topical Cooling Devices
Cool Line
Control
% Reduction
p*
One or more topical cooling
device (n/N, %)
26 / 154
16.9
67 / 142
47.2
64%
<0.0001
Cooling Blanket use (n/N, %)
25 / 154
16.2
59 / 142
41.6
61%
<0.0001
Other device use (n/N, %)
7 / 154
4.6
19 / 142
13.4
66%
0.008
* Fisher’s exact test
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Table 5. Antipyretic Use during Treatment Period
Cool Line
Any antipyretic medication use
Control
p*
n/N
%
n/N
%
94 / 154
61.0
127 / 142
89.4
<0.0001
•
Acetaminophen
87 / 154
56.5
124 / 142
87.3
<0.0001
•
Ibuprofen
16 / 154
10.4
29 / 142
20.4
0.02
•
Aspirin
18 / 154
11.7
12 / 142
8.5
0.44
* Fisher’s exact test
Complications
The following table lists the number of complications reported, by body system, for all
Cool Line and Control cohort patients within the first 30 days. The numbers
presented are the total number of reported adverse events by category and then total
overall. A patient may have had none, one or many adverse events reported in the
course of the study.
Table 6. Complications
Cool Line
Control
Body as a whole
15
9
Cardiovascular
26
21
GI
21
19
Hematologic
19
14
Infectious
93
74
Metabolic/Endocrine
24
18
Neurologic
49
52
Other
10
9
Peripheral vascular
15
13
Pulmonary
66
51
Renal
7
4
Total
330
275
The following table summarizes the SCVIR Guidelines for expected rates of success
and complications and the proposed threshold rates at which some form of retraining
or other action is indicated. In terms of complications, the use of the Cool Line is
generally associated with complication rates within SCVIR guidelines.
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Table 7. Complication Rates Compared to SCVIR Data
Specific Major Complications for Image-guided Central Venous Access
SCVIR
Expected
Complication
Rate(%)
SCVIR
Proposed
Threshold
Rate(%)
Subclavian and jugular
approaches
Observed Complication Rate
(%) in Cool Line/ CoolGard
Clinical Trial
Cool Line
Control
1-2
3
0.9
3.3
Hemothorax
1
2
1.9
0
Hematoma
1
2
0
0
Perforation
0.5-1
2
0
0
Air embolism
1
2
0
0
Wound dehiscence
1
2
0
0
Procedure-induced sepsis
1
2
0
0`
Thrombosis
4
8
3.3
7.8
Pneumothorax
None of the procedure related adverse events are unexpectedly high. There is no
indication that the Cool Line has unacceptable performance as a central line.
There were 4 patients in whom a CL-2085B could not be inserted. There were 2
patients for whom a CL-2295A could not be inserted but in whom success was
achieved with a CL-2085B.
The first pass and overall success rates for CL-2085B are presented in the table
below for the three insertion sites, Femoral, Jugular and Subclavian. Insertions were
considered a failure if the failure was not due to an operator error (e.g. contamination
of first catheter prior to insertion and then successfully implanting the second catheter
on its first attempt would be counted as a successful insertion even though two
catheters were used).
Table 8. Cool Line Catheter Insertion Success
n pts
1st Pass Success n,%
Success n,%
Femoral
20
14
70%
20
100%
Jugular
22
19
86%
22
100%
Subclavian
111
107
96%
108
96%
Total
153
140
92%
150
98%
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Specific Use Effects
Obvious Fever
Upon first presentation of a fever in a patient in a neurologic intensive care unit,
standard practice should include the taking of appropriate cultures and antibiotic
therapy based upon the result. This practice should be continued when using the
IVTM System and Cool Line catheter.
Patient Temperature
Bath Temperature
FEVER
COLD
If the IVTM System and Cool Line catheter have been in use for some time, the
presence of a fever requires investigation. It is possible for a patient to spike a fever
and overcome the capacity of the system. Should this occur at any time the physician
should:
1. Confirm that the system is functioning properly.
•
Make sure that the system is turned on and is connected.
•
Check the display to make sure that an alarm state has not been deactivated.
•
Confirm that the pin-wheel flow indicator is spinning.
•
Confirm that the patient temperature probe is working. (When standard
probes fail they usually do so as an open circuit. This failure mode would
be automatically detected and brought to your attention.)
2. Begin the standard regimen for the investigation of fever.
In very light patients or in the elderly, fever response may be, respectively, either
easily overcome by the system or naturally damped. Regardless of patient temperature or weight, the presence of a cold bath (i.e., minimum bath temperature)
should be regarded as the equivalent of a fever and the standard regimen for
investigating a fever should be started. If in doubt, turn the IVTM System to
standby mode for 1-2 hours and monitor the patient’s temperature. Restart the
system as clinically indicated.
Masked Fever vs. Steady State
These two states can be difficult to distinguish. If in doubt, put the IVTM System into
standby mode and observe the patient’s temperature for 1-2 hours. Restart the
system as clinically indicated.
With the IVTM System, there is a clear indicator of the activity of the system on the
right hand edge of the display. The red/blue meter indicates whether the IVTM
System is heating (red) or cooling (blue). In fever response mode, the display will
indicate MAX COOLING, this should alert the user to the possibility of another episode
of sepsis and standard antisepsis regimens should be followed.
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The IVTM System automatically logs both the patient temperature and the bath
temperature into memory. A review of this history record will show the time at which
the fever was initiated (a rise in temperature to the trigger threshold). The IVTM
System history record will also display the cooling bath temperature over time.
In Summary
The IVTM System is a heat exchange unit. If the IVTM System is cooling, fever is
present. Normal antisepsis regimens should be initiated.
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Icy, Quattro & Solex Catheters
Cardiac Surgery
Afterdrop
Evidence that general hypothermia is of benefit to patients undergoing
cardiopulmonary bypass (CPB) has existed since the 1940’s. Not withstanding the
development of warm cardioplegia and beating heart techniques, hypothermic CPB
remain a standard method used in open-chest cardiac surgery. CPB is done with a
blood oxygenator system (“the pump”) that has high heat exchange capabilities.
Upon completion of the cardiac procedure, the blood is rewarmed nearly to
normothermia before discontinuing the bypass pump. After disconnection from the
bypass pump, it is common for patient’s body temperature spontaneously drop back
2º to 5ºC in the absence of interventions to the contrary [15]. This is thought to occur
due to thermodilution of core blood as peripheral vascular beds vasodilate postoperatively. The patient would once again be hypothermic (termed “afterdrop”).
The effects of this “afterdrop” are varied. “Hypothermia predisposes the patient to
cardiac dysrrhythmia, increases systemic vascular resistance, precipitates shivering,
which increases oxygen consumption and carbon dioxide production, and impairs
coagulation. Furthermore, hypothermia causes a decrease in cardiac output by
producing bradycardia along with the increase in peripheral
vasoconstriction”[32][27][13][21].
Proper temperature control also requires that the patient not become hyperthermic.
As normal self-regulating mechanisms struggle to become reestablished, shivering
and other warming measures may produce “rebound” hyperthermia. Stevens’ (cit)
also found approximately 40% of the cardiopulmonary bypass patients they observed
reached hyperthermia four hours or more after arrival in the ICU. To avoid this
complication, Stevens and her group recommend discontinuation of active rewarming
efforts at 36.0ºC, and administration of acetaminophen to reduce additional
temperature increase upon achievement of normothermia. The concern of
hyperthemia is the increased metabolic demand results in greater cardiac work. A
device that warms a patient should, ideally, be able to prevent hyperthermia.
Fast-Track Recovery After Cardiac Surgery
The trend in post-operative care for patients recovering from CPB is to seek early
extubation and ambulation. This is termed the “fast-track” approach. The
development of the Fast Track recovery of CPB patients was driven primarily by a
desire to allow higher throughput in existing centers capable of supporting CPB.
Fast-track recovery produces shorter intubation time, and reduced intensive care and
overall lengths of stay. This approach involves optimization of all aspects of the CAB
procedures from the anesthetics used to the post-operative care. It has been shown,
however, that this can be done without increasing morbidity or mortality. Average
USA postoperative lengths of stay for isolated, primary elective CABG were 6.4 days
in 1997 with more complex cases averaging 10.5 days. Some authors report “UltraFast Track” results 70% of patients being discharged in less than or equal to 4 days
[25].
Typically patients are cared for in a cardiac surgery recovery area by cross-functional
teams with the aim being extubation within 4-6 hours after the termination of the
procedure [26][20][14][17]. “Safe extubation requires that the patient be alert and
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cooperative, be hemodynamically stable and warm, is not bleeding, and has
adequate respiratory function” [22]. The maintenance of normothermia is one of
many homeostatic functions that must return. In focused trials it has been shown
that, with attention to temperature management post-operatively, the recovery team
can eliminate postoperative shivering which resulted in the lowering of oxygen
uptake, carbon dioxide production, and required ventilatory volumes[18][21].
Variation in external conditions such as room temperature and humidity, patient size,
and concurrent pharmacologic treatments affect both the core temperature and the
speed at which it changes.
In effect, the thermal challenge after CPB is to restore the patient to normothermia
quickly, but without allowing an overshoot of the target temperature. Measures used
historically for temperature control are effective in different applications, and each
has its disadvantages.
Rewarming Post-Cardiac Surgery
The most commonly used warming techniques are external and “passive”; that is,
they rely primarily on the body’s own heat-producing mechanisms to restore normal
temperature. Applying heated or reflective blankets, using radiant heat sources from
overhead or near the bed, and raising the room temperature are uncomplicated,
inexpensive and readily available. However, they are labor-intensive and can be
uncomfortable for nursing staff and visitors.
“Active” rewarming methods such as heated mattresses and forced-air tents seem to
be more effective and faster at raising the core temperature; but they too require
substantial management by hospital staff, and still leave the temperature fluctuating
around a desired target. Villamaria et al [24] reported, in a randomized controlled
trial, that both forced air warming devices and more conventional warm blankets and
overhead heating lamps showed similar performance. They reported rewarming
rates of 0.25ºC per hour. In a randomized controlled trial, the use of warming
blankets in a typical recovery area resulted in a 0.5ºC/h increase in core temperature
[16]. The rate for the Bair Hugger system was 0.75ºC/h.
Neurosurgery
Operative Hypothermia
Hypothermia is desired in some forms of neurosurgical procedures and has been
used for over a decade [33]. Outside of the use of cardiac bypass pumps, the limit to
this hypothermia is typically set to 32°C to avoid the temperatures at which cardiac
ventricular arrhythmia are likely[28][29]. The theoretical basis for the use of
hypothermia comes from studies that show reduced intra-operative stress responses
[34] and ischemic insult, and better neural repair in the context of cooling[35][36].
Typical conventional methods of cooling involve the use of cooling blankets and/or
convection via cold air. Iwata et al [37] showed cooling rates using conventional
convection and water blanket methods of 2.5°C in 1.5 hours (i.e. 1.6ºC/h). Their
study was a randomized controlled trial that examined the difference in cooling rates
between two anesthetic agents; Profofol and Sevoflurance. Their well controlled data
provides an insight into the rate of cooling that is expected in such patients. It also
illustrates that the use of more than one method of cooling is acceptable within this
clinical setting.
The limits of surface cooling are set by vasoconstriction [38]. As skin temperature
drops skin vasoconstriction increases so that heat exchange between the external
environment and the internal milieu is reduced. The skin acts as an insulator. As a
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result endovascular methods of cooling allow the removal of heat at rates greater
than can be achieved with surface cooling for the same driving ΔT (i.e. difference in
temperature) between the core of the patient and the cooling source.
Gal and Cundrle [39] showed similar effects in their study of mild hypothermia in
patients scheduled for neurosurgical procedures. Using “back and front” cooling
blankets they reported that “the patients were cooled at a rate of 1.1+/-0.3 degrees
C/h and rewarmed at a rate of 0.9+/-0.4 degrees C/h.”. They reported no
complications attributed to the cooling in 20 elective patients.
Inoue et al [40] reported on active conventional cooling and rewarming rates
comparing device alone with device plus amrinone. Amrinone is an inotrope that
causes, amongst other things, decreased peripheral resistance i.e. it will reduce the
thermal insulation offered by the skin by reducing peripheral vasoconstriction.
Cooling rates were 0.96 vs 1.36ºC/h and rewarming rates were 1.02 v 0.73ºC/h for
the control v the Amrinone group respectively. The cooling device int his case was a
blanket system.
The above short literature review summarizes current expectations as to cooling and
rewarming rates in the context of neurosurgery.
Rewarming
Hypothermia after neurosurgery is of concern and occurs for reasons similar to those
described for cardiac surgery with the added problem of not having the efficient
warming provided by the cardiac bypass pump [41]. Shivering is associated with an
undesirable increase in left ventricular systolic work index and oxygen consumption
index in post-operative neurosurgical patients. Endovascular heat exchange
catheters offer controlled rewarming and help to ensure post-operative
normothermia.
Catheter Selection
The IVTM System and the various IVTM catheters offer a convenient alternative,
allowing fine and automatic control of the core temperature that can be maintained
until biological temperature-control mechanisms are fully reestablished. In this
application , the IVTM System can be used with four catheters of similar concept but
varying size.
The Icy catheter is suitable for femoral vein placement without a sheath for up to 4
days. It has a 8.5 Fr shaft. The Icy catheter has been CE marked and has proved
safe in clinical use .
The Quattro catheter is suitable for femoral vein placement without a sheath for up to
4 days. It has a shaft size of 9.3 Fr.
The Solex catheter is suitable for jugular vein placement without a sheath for up to 48
hours. It has a shaft size of 9.3 Fr.
Publications on the clinical use of IVTM Catheters include abstracts and peer
reviewed article[19][12][23].
For all IVTM catheters, please refer to the “Instructions for Use” for the complete list
of contra-indications, warning and instructions for a particular catheter. The section
below provides a guide to physicians to assist in catheter selection.
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Table 9. Catheter Characteristics
Effective Length
Infusion Lumen
Nominal Power
(cooling / heating)
Icy
38 cm
Proximal, Middle and
Guidewire (Distal) lumen
140 / 35 W
Quattro
45 cm
Proximal, Middle and
Guidewire (Distal) lumen
180 / 50 W
Solex
25 cm
Proximal, Middle and
Guidewire (Distal) lumen
140 / 35 W
Catheter
Anesthetized patients are unable to turn on normal heat generation (e.g. through
shivering or adrenergic drive) and have impaired peripheral vascular responses i.e.
they are rendered essentially poikilothermic by the anesthetic. Under these
conditions, these catheters will provide approximately the following rates of cooling
and heating in a 75 kg person:
Table 10.
Catheter
Cooling
Heating
Icy
2 ºC / hr
0.5 ºC / hr
2.5 ºC / hr
0.8 ºC / hr
2 ºC / hr
0.5 ºC / hr
Quattro
Solex
The Icy and Quattro catheters are femoral lines.
The Icy has a lower surface area and is therefore theoretically less likely to cause
thrombo-embolic events. It is also significantly shorter in its applicable length.
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