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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Specific Use Effects
Cardiac Function
The use of any central catheter brings with it potential for alterations in cardiac
function. Hypothermia applications bring attendant risks of bradycardia and
ventricular arrhythmia. IVTM catheters do not carry additional risk in this respect
when used in a normothermia application since the intention is to maintain the patient
at a normal body temperature. The discussion below explains this in more detail.
Bradycardia
The induction of bradycardia is not a particular risk of normothermia applications of
the IVTM System .
Bradycardia is an inevitable result of hypothermia. Cardiac tissue is an excitable
tissue. Bjornstad et al [11] studied the cardiac effects of hypothermia in dogs. There
is a linear increase in the duration of the epicardial monophasic action potentials
(MAP) and ventricular effective refractory period (VERP) with decreasing temperature
from normal to 25°C. Bradycardia that does not revert with a return to normothermia
requires further investigation.
Arrhythmia
The induction of ventricular arrhythmia is not a particular risk of normothermia
applications of the IVTM System except insofar as this is theoretically possible with
any central line insertion due to direct physical cardiac irriation.
Ventricular arrhythmia are of concern in hypothermia. Cooling reduces the
monophasic action potential. As a result, Bjornstad et al [11] showed a
corresponding decrease in the fibrillation threshold during electrophysiological
testing. Similar work has been done by Mortensen et al (1993) and Bjornstad et al
(1995) with little evidence that agents that alter ion channel behavior can modify the
effect.
The effects of hypothermia upon an individual heart will worsen with the extent of preexisting cardiac disease. Conventional wisdom is that ventricular fibrillation cannot
be reversed at temperatures below 25-28°C and that coma is induced somewhere
below 30°C[28][29]. However Thomas & Cahill [30] reported electromechanical
cardiac recovery at 25.6°C and DaVee & Reineberg [31] at 20°C.
There exists a specific risk with any system that relies upon cardiac output, such as
the IVTM catheters, for heat exchange. In the event that the catheter system is used
in patients that are moderately to severely hypothermic (i.e. below 32°C) it is possible
that fibrillation will occur and be irreversible until the heart is warmed. With no
cardiac output , there is no mechanism to raise that patient’s core temperature.
Death would ensue unless the patient was on coronary bypass or could be rapidly
rewarmed by other means.
In the usual cardiovascular situation, the patient is warmed to the mid-30’s prior to
disconnection from the bypass pump so that this situation does not arise.
In Neurological hypothermia, it is important not to depress the cardiac temperature
below 30ºC. The CoolGard 3000 is limited by design to prevent the selectio of setpoint temperatures to below 32ºC as a result.
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Lung Function
It must be stressed that, as with any central line, the placement of the line must be
verified by chest x-ray. As with any central venous line, both late perforation of a
large vessel and delayed presentation of a pneumothorax are possible.
Sepsis
In the rewarming post-opeartive period, procedural infections should not develop
simply because there is usually insufficient time for organisms introduced during
surgery to have reached a pathological mass. However it should be remembered
that the IVTM System can mask fever. Infections could predate the surgical
procedure. Clinical signas of sepsis should never be ignored just because of the
absence of a fever.
Infection
In this indication, the use of IVTM catheters is intended only for the short period
during and post-procedure. Standard asceptic techniques should be followed, in
accordance with the Instructions for Use, during insertion. Standard management
practices for insertion sites of central lines should be followed for IVTM Catheters.
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General Risks of Central Line Usage
The IVTM catheter functions as a central line. As with any central line, the risks of
usage relate to the insertion technique, the materials and design of the catheter, and
to the state of the patient. 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.
Caveats to CVC Placement (CVC-WG)
The following are the general caveats to the use of a central venous catheter
published by the Central Venous Catheter Working Group [6][7][8].
1. Central venous catheterization should be performed only when the potential
benefits appear to outweigh the inherent risks of the procedure.
2. The catheter tip should not be placed in, or allowed to migrate into, the heart.
3. Catheter tip position should be confirmed by radiograph or other imaging
modality and be rechecked periodically.
4. Central venous catheterization must be performed by trained personnel well
versed in anatomical landmarks, safe technique, and potential complications.
Users in training must be closely supervised by qualified personnel to assure
their technical expertise before independent performance of these
procedures. Ongoing monitoring should be undertaken to assure continued
experience.
5. Those placing CVCs should be familiar with the specific equipment used as
well as the proper selection of insertion site and catheter type, size, and
length.
6. Those caring for patients with indwelling central venous catheters should be
well informed of the appropriate care and associated complications of CVCs.
7. Manufacturers should include specific labeling to address potential
complications of CVC use. Users should read all manufacturer’s labels,
instructions, and warnings, as these contain important and useful information
essential for the safe and effective placement of the catheter.
8. Except as may occur in certain emergencies, catheterization should be
performed with full aseptic technique to include hand washing, sterile gloves,
masks, hats, gowns, drapes, and proper use of suitable skin antiseptic.
9. Catheters placed in less-than-sterile fashion should be replaced as soon as
medically feasible.
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Infection
Catheter Related Bloodstream Infection (CR-BSI) are of concern with any catheter.
There is a significantly increased risk of CR-BSI [42] associated with:
•
Inexperience of the operator and nurse-to-patient ratio in the intensive
care unit,
•
Catheter insertion with less than maximal sterile barriers,
•
Placement of a CVC in the internal jugular or femoral vein rather than
subclavian vein,
•
Placement in an old site by guidewire exchange,
•
Heavy colonization of the insertion site or contamination of a catheter
hub, and
•
Duration of CVC placement > 7 days.
The US Center for Diseases Control has published Guidelines for the Prevention of
Intravascular Catheter-Related Infections[43]. The recommended preventive
strategies with the strongest supportive evidence are:
•
Education and training of healthcare providers who insert and maintain
catheters;
•
Maximal sterile barrier precautions during central venous catheter
insertion;
•
Use of a 2% chlorhexidine preparation for skin antisepsis;
•
No routine replacement of central venous catheters for prevention of
infection; and
•
Use of antiseptic/antibiotic-impregnated short-term central venous
catheters if the rate of infection is high despite adherence to other
strategies (ie, education and training, maximal sterile barrier precautions,
and 2% chlorhexidine for skin antisepsis).
The same Guidelines make the following recommendations relating to the
replacement of catheters in relation to the management of catheter-related infection.
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Table 11. Summary of Recommended Frequency of Replacements for Catheters,Dressings,
Administration Sets, and Fluids
Device
Replacement and
relocation of
device
Replacement of
catheter-site
dressing
Replacement of
administration
sets
Hang time for
parenteral fluids
Central venous
catheters
including
peripherally
inserted central
catheters and
hemodialysis
Catheters.
In adults, do not
replace catheters
routinely to
prevent catheterrelated infection.
In pediatric
patients, no
recommendation
for the frequency
of catheter
replacement.
Replace gauze
dressings every 2
days and
transpar-ent
dressings every 7
days on shortterm catheters.
Replace the
dressing when
the catheter is
replaced, or when
the dressing
becomes damp,
loosened, or
soiled, or when
inspection of the
site is necessary.
Replace
intravenous
tubing and addon devices no
more frequently
than at 72-hour
intervals. Replace
tubing used to
administer blood
products or lipid
emulsions within
24 hours of
initiating the
infusion.
No
recommendation
for the hang time
of intravenous
fluids, including
nonlipidcontaining
parenteral
nutrition fluids.
Complete
infusions of lipidcontaining fluids
within 24 hours of
hanging the fluid.
Replace
disposable or
reusable
transducers at 72hour intervals.
Replace
continuous flush
device at the time
the transducer is
replaced.
Given the above, the following points are worth noting about IVTM heat exchange
catheters:
1.
As with any central line, the primary method for the prevention of CR-BSI
with IVTM catheters is to employ a thorough asceptic technique during
insertion and with handling of the insertion site and catheter blood path
components..
2.
IVTM catheters are labeled for indwelling use for 2-7 days depending upon
model.
3.
The Start-Up Kit, with its associated tubing, is supplied sterile. Once primed,
using an asceptic technique, it should remain sterile. Unless there is a
breach of the catheter balloon or manifold there is no infection risk to the
patient from this fluid as it does not enter the patient.
4.
ZOLL supplies Chlorhexidine Gluconate skin preparations and a
Chlorhexidine Gluconate insertion site patch to help reduce the risk of skin
commensals colonizing the shaft.
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Specific Operational Issues
WARNING! PATIENTS MUST BE CONTINUOUSLY
MONITORED.
Patients being treated with the IVTM System must be checked frequently (hourly)
when the IVTM System is operating. It is possible for malfunctions or misuse of
the IVTM System to result in patient injury or death.
ZOLL strives for the highest possible quality in its product–you expect that. Where
failure modes can be anticipated, we have designed the product so that, should it fail,
it will fail in a patient-safe manner.
Stop the Pump
The IVTM System is designed so that internal failure modes that pose a threat to the
patient will cause the system to stop the pump and sound an audible alarm. This is a
safe mode of operation because heat exchange will rapidly cease if there is no flow
through the catheter. If the pump is inactive, it is more difficult to make infusion
errors.
If the pump stops, check the display screen. You may have failed to hear or respond
to an audible alarm.
The pump will also stop under normal operating conditions:
1. Temperature inversion. The IVTM System will deactivate the pump
whenever one of the following states occurs to prevent unwated heat
transfer from/to the patient:
Coolant Temperature <Patient Temperature < Target Temperature
Coolant Temperature > Patient Temperature > Target Temperature.
Normal pump operation will recommence once the inversion has reverted.
2. The IVTM System ‘self checks” its cooling engine each hour. To do this,
it stops the pump so that the heat load of the patient is removed from the
analysis.
3. The IVTM System is operating in “Fever Mode”.
Air Bubble Detector
In uncommon circumstances, it is possible for air to enter the tubing circuit of the
Start-Up Kit. In such cases, the integrity of the catheter prevents air entry into the
patient. In the rare event of a second, simultaneous failure of the catheter, air entry
into the patient is possible.
The IVTM System features an air bubble detector. This will cause three things to
occur if a significant amount of air enters the Start-Up Kit:
1. An audible alarm will sound.
2. The screen will display an appropriate error message:
“Air Trap Warning–Refer To Manual. Press Enter To Proceed.”
3. The IVTM System will stop managing the patient’s fever.
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ALWAYS INVESTIGATE AIR BUBBLE ALARMS.
At a minimum, locate the source of the air or confirm that there is no breach in the
tubing circuit. If the circuit has been demonstrated to be intact, disconnect tubing set
from catheter and re-prime the circuit to exclude all air. After re-establishing IVTM
System function, verify that there is not a failure somewhere in the tubing path. If in
doubt, replace the tubing set. Ensure that there is sufficient fluid within the tubing
circuit.
Air entry into the tubing circuit does not, of itself, cause injury. A second point failure
of the catheter is required before injury can result.
Fluid Loss Detector
The IVTM System integrates its air bubble and fluid loss detection methods. Optical
sensors detect the presence of air inside a reference cylinder. Loss of fluid from the
cooling circuit sufficient to empty this cylinder will cause an air bubble detection
alarm.
ALWAYS CHECK FOR FLUID LOSS WITH AN AIR BUBBLE ALARM.
It is recommended that the bags of saline solution used to prime and run the IVTM
System tubing system be limited in volume to 500 ml or less. In the event of a fluid
leak into the patient, the maximum amount of fluid that can enter the patient is the
volume of the bag less the volume of fluid left in the tubing system after the alarm has
been triggered (i.e., in the worst case, 400ml of the 500ml fluid in the system can
enter the patient).
The cooling circuit is a closed loop system–usually fluid loss alarms indicate a breach
somewhere in this closed loop. With any fluid loss alarm, check both the integrity of
the catheter and the tubing of the Start-Up Kit (see following). PERIODICALLY
CHECK the tubing of the Start-Up Kit for significant air bubbles and replace the kit if
necessary.
To check the integrity of the catheter:
1. Stop operation of the IVTM System.
2. Using aseptic technique, disconnect the tubing set from the catheter and
properly cap both the catheter and tubing set.
3. Fill a sterile 5 ml syringe with sterile saline.
4. Connect the syringe to the INFLOW lumen of the catheter and disconnect the
outflow cap. Infuse the 5 ml of saline–it should flow out the outflow lumen.
5. Now cap the OUTFLOW lumen and pull 5 cc of vacuum and sustain this for at
least 10 seconds. Approximately 4 ml of saline, but not blood, should enter
the syringe and you should be able to maintain the vacuum.
6. Ease the vacuum and recap the INFLOW lumen.
To check the integrity of the tubing set:
1. Look for obvious leakage.
2. Remove the tubing from the pump raceway and inspect for damage (return it
to position if undamaged).
3. Check along the tubing from the pump to the patient for sources of fluid loss.
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Look for damage to the tubing and/or the presence of air within the tubing.
•
Inspect, and tighten as necessary, each Luer fitting (do not use
instruments to tighten Luer fittings).
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4. Similarly, check the tubing that returns to the pump from the patient. Examine
the saline bag to ensure that it has not been accidentally compromised (for
example, the spike may have damaged the bag wall).
5. Lastly, trace the tubing from the saline bag back to the pump.
Cool Line Catheter – Two Functions
The Cool Line is both a heat exchange catheter and a central venous line. The loss
of heat exchange function, for any reason, does not necessarily invalidate the use of
the catheter as a central line.
Should the catheter’s balloons fail or the heat exchange functionality not be required,
the Cool Line should still function as a viable central line. Simply cap the inflow and
outflow lumens together to ensure the sterility of the catheter and use the infusion
lumens as you would any central line.
Seven Day Dwell Time – Cool Line Catheter Only
The Cool Line catheters, and the associated Start-Up Kit, are cyclically pressuretested to ensure that they can withstand the forces of the pump over extended
periods of time. ZOLL labels its catheters for no more than seven days use. It is
recommended that an over-the-wire exchange be conducted after this time if heat
exchange support is still required.
If heat exchange functionality is no longer required, the catheter may remain in situ if
its central line functions are still required. In such cases ZOLL recommends that you
disconnect the IVTM System and, using aseptic technique, cap the inflow and outflow
lumens of the catheter together. The catheter may then be used as you would any
central line.
“Dead Head” Pressure
The IVTM System relies upon fluid being pumped to and from the patient. This is
done under pulsatile pressure. Each time the rotor pump sweeps the tubing there is a
peak in the pressure in the tube and more fluid flows through the system. Usually the
inflow lumen has an operating pressure that is almost the same as that in the tubing
at the pump and the pressure then drops along the length of the IVTM catheter so
that the return pressure is low.
Should the return tubing be occluded, the entire length of the catheter will see
pressures that are effectively the same as those at the pump. Our engineers call this
the “dead head” pressure. This pressure is not sufficient to rupture the balloon or the
catheter. However, cyclically stressing the catheter with this pressure for prolonged
periods of time is not recommended.
Water and Propylene Glycol
The fluid in the bath is a propylene glycol and water mixture. Should the bath level
drop, this will usually be simply due to water evaporation from the bath (at room
temperature glycol will not noticeably evaporate). In such cases, add distilled water to
the bath to return it to its original fill level (the heat exchange coils must be covered).
The safe handling of the glycol is a simple matter. Spills can be safely wiped up with
paper towel and disposed of in the ordinary trash. As with any chemical spill, wearing
gloves is preferable. It is not flammable under normal conditions and not volatile.
ZOLL can supply Material Safety Data Sheets on the material used (for details,
contact our Customer Service department).
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Dual Temperature Probes
The IVTM System features dual temperature probes. One probe, the sensing probe,
is typically placed in the bladder and is used to control the IVTM System’s action. The
other probe, the backup probe, is typically placed in the rectum and acts as a fail-safe
mechanism. If the difference in reported temperatures between the two probes
exceeds 2ºC, an alarm is sounded to warn the operator. If this occurs, it is usually
due to one of these events:
•
One of the probes has failed.
•
One of the probes has become dislodged from the patient.
The use of two temperature probes is the preferred operating mode for the IVTM
System. It is permissible in the IVTM System to deselect the backup probe (for
details see the Operation Manual). In this mode, the user is expected to use a
backup temperature monitoring device that is part of the bedside monitoring setup.
When using a single probe, for patient safety, it is important to set the temperature
alarm limits of the backup temperature monitoring system as described in the
Operation Manual. Failure to do so exposes the patient to the risk of injury.
For example, consider a patient with a single, bladder temperature probe in place
and a core temperature that is stable at 36.5ºC. If the bladder catheter is slowly
dislodged, the temperature sensor will indicate a temperature that moves
gradually from the bladder temperature to the temperature of the bed (in this
example let us say 32ºC). The system would sense this as a drop in core
temperature and begin to heat the patient. If the alarm limit on the backup sensor
is properly set, the operator’s attention would be immediately drawn to the
dislodgement of the first probe as the patient’s core temperature rose.
Single Use/Service Life
All IVTM catheters, and the associated Start-Up Kit, are subject to cyclically loading
as a result of the peristaltic pump within the IVTM System. They may fail due to
fatigue, with the leaking of saline into the patient, if used beyond their service life.
Use of catheters and Start-Up Kit beyond the recommended service life is potentially
dangerous. IVTM catheters and Start-Up Kit are strictly intended for single use.
Check the Pinwheel
In an earlier section the importance of ensuring proper flow through the catheter was
stressed. The Start-Up Kit features a clear plastic pinwheel close to the patient
connections on the Start-Up Kit tubing set. This pinwheel provides a general and
immediate indicator of flow within the system. It is a sound general practice to
arrange the tubing set so that this simple visual indictor can be seen at the patient
bedside. This pinwheel is not a calibrated instrument, however, absence of
movement of the pinwheel indicates the need to check for compression of the tubing
set or kinking of the catheter.
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