-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 1
physiology.lf1.cuni.cz
Handout
SIM Lab: ICM Basics ICM = Intensive Care Medicine
THIS TEXT WILL BE UPDATED BY MAR 21
3. Blok (LS)
Here you find some self-study notes for ICM SIM Lab
List of competencies Block 1: Intensive Care Monitoring –
Respiration, Capnography, BP Block 3: Basics of Advanced life
support
The information provided here is simplified, tailored for the
purpose of Physiology SIM Labs The more you know before coming to
the SIM lab, the more time we can spend hands-on… ;-)
Thanks to Michal Pisinger for the translation.
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 2
KNOWLEDGE AND GOALS Required knowledge: SIM I1, B1 , B2, I2:
Basic examination of the patient without aids including hearing.
Evaluating conditions. SBAR. Examination with aids: ECG, NIBP,
SpO2, basics of capnometry. Normal ranges of parameters. Basics of
respiratory regulation. Basics of measuring IBP, normal curve.
Basics of respiratory masks, giving O2. First aid: BLS, AED
Goals:
The basics of anesthesia, resuscitation, and intensive care. (On
simulations) o Continual monitoring of patients in anesthesia or in
intensive conditions, evaluating
conditions o Recognizing serious/critical situations and timely
decisions to intervention, o Execution of some interventions,
principles
Cooperation in a group, basics of CRM (crisis resource
management). The dynamics of conditions; integrating other
physiological parameters.
Purpose: To prepare for practicals with anesthetized rats, where
we cannot rule out life threatening
complications. To illustrate the context of physiological
functions and parameters on clinical cases.
Knowledge (after completing the lab): Knowledge of principles
and usage of all listed parameters, methods of monitoring and
interventions. 1. Vital monitoring. Orientation on an expanded
monitor of an intensively monitored patient (ECG,
IBP, CVP, SpO2, RR, capno, T). Principles, context, norms,
indications, limits. a. CVP is a relatively easy to monitor
parameter. Is an indicator of (-volemia, preload,
pumping function of the right heart). b. ARTerial pressure in
serious disorders of hemodynamics commonly needs to be
measured invasively (advantages: continual measuring, reliable
even with very low values)
c. Respiration (RR) can be continually monitored with capnometry
or impedance. d. Capnometry (CO2) allows evaluating the adequacy of
ventilation, along with diffusion
and perfusion. 2. Urgent conditions: circulatory and respiratory
arrest.
a. Deciding when to begin and end urgent resuscitation
(monitored patient) b. Basics of expanded resuscitation (ALS),
execution c. Defibrillation - principle, indication (rhythms which
can be defibrillated)
3. Anesthesia (general) a. Anesthetics commonly inhibit the
respiratory center. The result of that can be hypoxia
and cardiac arrest. b. Anesthetics may inhibit the vasomotor
center and ANS. That can lead to hypotension,
bradycardia, ev. cardiac arrest. It can even prevent the
manifestation of a stress reaction (↑HR a BP).
c. Anesthesia is risky => need to monitor continually 4.
Serious conditions (bradycardia, hypoxia, hypotension,
dehydration/hypovolemia, insufficient
analgosedation). Recognition, principles of correction, chosen
reactions. a. Generally in hypoxia (SpO2 < 95% *) you need to
give oxygen. b. Hypoxia and pain significantly stimulate the
sympathicus.
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 3
BLOK 1 = Continuous Monitoring, Response The basics of
examination and monitoring (ECG, SpO2, NIBP, T) which have been
repeatedly gone through. Now we'll complete respiration and
pressure.
1. Monitoring respiration.
RR imp - measuring respiratory rate with impedance
After connecting ECG leads, not only will you see an ECG curve
on the patient monitor, but also the value of respiratory rate,
maybe even a respiratory curve. The monitor determines these values
on the basis of continually measuring electrical conductance of the
thorax (more precisely impedance). The change of conductance here
is because of the change of air in the lungs (more air = less
conductance). This method is very useful as a continual record of
respiratory rate. However, it isn't sufficiently precise and
robust, so you cannot measure spirometric parameters (lung volumes
and flow) from the impedance curve. Questions, tasks
Measure RR imp on yourselves (one from the group) with the help
of a patient monitor.
Why isn't RR imp a useful method for measuring ventilation?
[Impedance is greatly influenced by many factors other than just
breathing. The amount of water/blood, resistance of electrodes,
movement, … They're involved in every measurement of impedance]
Ventilation
In patients with artificial ventilation, the ventilator measures
many parameters including pressure in airways (Paw) and flow (from
this we can for example calculate minute ventilation (MV). These
parameters cannot be continually measured other than with a
ventilator. Questions, tasks
Examine the circle of the ventilator
Capnography (provides the parameters RR aw, etCO2)
Methods which provide a lot of information, for example
respiratory rate (RRaw) and alveolar concentration (etCO2), which
shows the adequacy of ventilating relative to metabolic demands.
What is it: Continual record of pCO2 in air which we are breathing
(inhalation and exhalation). etCO2 depends esp. on: i) production
of CO2, ii) circulation - bringing CO2 into the lungs iii)
pulmonary diffusion, iv) minute ventilation see the diagram.
Significance: Especially evaluating the adequacy of ventilation.
ATTENTION, capno also depends on perfusion and others see below.
Normal values cca 40 +/- 4 mmHg (cca 5.2 kPa) Indication: in all
patients with secured airways, when ventilating with a mask (not
always, but is becoming more common) Principle: CO2 is calculated
spectophotometrically (infrared) in the air, which flows through a
breathing tube. The sensor is located in a way that it can
continually sample inhaled and exhaled air. (Where is it?) The
output is typically: i) curve of pCO2 over time ii) value of pCO2
at the end of exhalation (EtCO2) iii) respiratory rate value
(RR)
Capnometry is an analogous method, however, it only provides
EtCO2 a RR, not a curve (graph).
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 4
Questions, tasks
Measure capnography (one from the group), notice the values of
etCO2 and RRaw. Reach hypo- and hypercapnia. What influences the
value of EtCO2: (for starters evaluate every parameter
individually)
o Circulatory arrest o Defect of pulmonary diffusion, o
Hyperventilation, o Hypoventilation. o Disproportion of
ventilation-perfusion
2. Monitoring blood pressure (NON/INVASIVE)
NONINVASIVE:
CVP can be roughly estimated just by looking at the filling
level of the neck veins. It isn't very handy for continual
monitoring.
ARTerial pressure can be monitored noninvasively with a cuff
from the patient monitor, which can be programmed to repeatedly
measure in intervals according to need (typically minutes up to
hours) Output: SYS/DIA (mean)
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 5
INVASIVE: Invasive (direct, bloody) measuring of pressure is
directly in the blood vessels (ev. heart). Significance: i.
Continual measurement (important especially in failing
circulation).
ii. Reliable measuring even in very low pressure (for ex. in
shock), when measuring with a cuff is complicated. iii. Is the only
precise method of measuring CVP
Principle: percutaneous introduction of catheter into blood
vessels. The sensor is usually on the outside of the patient's
body, at heart level Why?. The sensor and catheter are connected
with a tube (similar to a saline one) filled with physiological
solution which must be without air (vented) Why?.
Central venous pressure (CVP)
CVP is the pressure in large veins at heart level. CVP depends
mostly on i) venous return, ii)filling of blood vessels and iii)
pumping function of the right heart iv) venous tone/pressure of the
thorax Significance: Lowered values CVP are for example in
hypovolemia, lowered return, increased during hypervolemia and
conditions, where the heart is failing to pump blood. It's possible
to come up with it ;-) Normal values of CVP are around 2-8
mmHg.
CVP - Execution
For measuring CVP, it is necessary to introduce a catheter where
the distal end is in the caval vein at heart level. The typical
access point is the jugular or subclavial vein. Cathetrization of
central veins is mostly standard in many departments because of
long term infusion therapy, parenteral nutrition etc. (ICU,
surgery, ARO). Cathetrization of central veins carries certain
risks (infections, thrombosis, pneumothorax during introduction).
It must be smaller than expected benefit.
Output of invasive measuring CVP is a curve on the monitor
labelled as CVP and a numbered value of mean pressure, typically in
mmHg.
Arterial blood pressure (ABP, ART, RAD, FEM, Ao, …)
ART is the pressure in the arterial vessels (at the end of the
catheter, but it is relative to heart level) ART typically depends
on: i) cardiac output, ii) peripheral vascular resistance, iii)
volume of circulating fluids Significance: evaluating hemodynamics,
managing treatment with vasopressors, estimating organ perfusion
Indications: Hemodynamically unstable patients (ICU, ARO,
operations), cardiovascular operations Risks. Injuring arteries,
ischemia of vessels, air embolism, bleeding. Risks are bigger than
in CVP and must be assessed against benefit. In unstable
hemodynamics, IBD is completely indicated. Output of invasive
measuring ART is a curve on the monitor labelled as ABP or ART or
according to the respective artery, RAD, FEM, Ao, PAP,… or heart
section (LVP, RVP, RAP …) along with numbered values of SYS/DIA
(mean), typically in mmHg.
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 6
Questions, tasks: Examine the model of direct blood pressure
measurement. Try changing the position of the
sensor and aeration to see how it affects measurement. Color the
ART curve (from memory). Why is measuring art more dangerous than
CVP? Why must the sensor for IBP be at heart level while a
sphygmomanometer for NIBD doesn't? What is the difference between a
IBP curve and SpO2 (more precisely plethysmographic)? What is
"zeroing pressure“? [calibrating the sensor according to
atmosphere. Atmospheric
pressure is set as 0 mmHg] Can coagulation/thrombosis endanger
the catheter, embolism/thrombosis of blood vessels?
[YES. The catheter is usually continually flushed by a
physiological solution with heparin. Very slowly]
Would you be capable of willfully changing your CVP value? Note:
The sensor must be zeroed to the value of atmospheric pressure
before introduction
(also continually).
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 7
3. ICM TROUBLESHOOTING HINTS (monitored patient) In patients who
are monitored continuously the decision making process differs from
Basic Life Support algorithms. In monitored patients there often is
a lot more reliable data available - both anamnestic and real-time,
continuous. Thus the priority often is checking CIRCULATION (vs.
BREATHING in BLS) The table below gives brief overview how to
assess and troubleshoot various issues in intensive care. This is
NOT an algorithm or prioritized list. Thus it is essential to
understand the principles to be able to respond adequately in
various circumstances.
Symptom Check Possible solutions (FIX TECH. ISSUES FIRST)
D danger
Many… Don't underestimate unexpected risks.
R response
Movement Pain response
Reaction to pain (depth of anesthesia)
Pulse, pressure
Consider deepening anesthesia
A airway
WHEEZING NOT BREATHING
Airways (head-tilt, secretion, aids securing airways)
Head-tilt Sucking up secretion of
airways
B breathing
still NOT BREATHING NORMALLY
Mask + resusci bag Breathing tube (airtight?) Ventilator
Begin breathing with bag
C circulation
Signs of arrest HR < ~40 bpm Cyanosis/pale
ECG, skin color, pulse, pressure Quality of monitoring
CPR Circulation Support?
ECG unreadable VT/VF HR < ~40 bpm
Attachment of electrodes. Gel? Settings of leads Manipulation
with the patient?
Tremor?
VF/VT => CPR + DEFI Circulation support (HR)
SpO2 < 95% Signal Low Inaccessible 100%
Attachment of sensor Peripheral hypoperfusion? (cold
extremities, hypotension, strangulation,..)
Breathing incl. hearing Inhaled oxygen (FiO2)
Options: Secure airways Administer O2 Ventilation support
Circulation Support Treat acral parts
BP Not recording High Low
Cuff Link IBP Manipulation/is the patient moving?
Options in hypotension: Administer fluids Cardiac support
Vasopressors Options in hypertension: Remove Stressor
Vasodilation
etCO2 Not recording High Low
Location of the sensor Breathing circuit tight? (no leak?)
Breathing incl. auscultation Hemodynamics Metabolism
-> ventilation adjust. -> hemodynamic support -> see
later.
T Low (High) Check thermometer location Check thermometer
connection
Warm up (solutions, air)
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 8
BLOCK 2 = ICM Simulations
This part is aimed at experiential learning and has no
self-study text.
Basic competencies in simulation medicine and relevant chapters
from ALS and Physiology are expected (See the Knowledge section
above.)
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 9
BLOCK 3 = ALS essentials We presume the knowledge of basics life
suppotr (BLS). Let's shortly summarize some differences between ALS
and BLS. The essential difference is that in ALS we have various
aids at hand, often including monitoring. Priorities based on
urgency:
Recognizing cardiac arrest. Beginning chest compression.
Connecting a monitor/defibrillator - timely defibrillation (if it
is indicated). Ventilation Oxygenation, eventually securing the
airways Getting entry into the vasculature, pharmacological
support. The main priority is circulation, but we often make our
decisions based on ventilation. That may cause
confusion.
1. Recognizing cardiac arrest and deciding to initiate
resuscitation In real life situations the decisions aren't that
trivial even for professionals. Decisions is mainly based on: 4.
Presence of unconsciousness (however in patients under anesthesia
this isn't really meaningful) 5. ECG: asystole or ventricular
fibrillation (VF) 6. ECG + central pulse in other rhytms when we
suspect circulatory arrest. Note: If we don't have machines: the
way we make our decisions is like in BLS. Gasping or no breathing
(not checking pulse)
2. Chest compression
7. The principles and procedure are the same as in BLS: o Begin
as soon as possible trying to substitute the mechanical function of
the heart, therefore
securing circulation o It is vital to compress with the minimal
amount of interruptions. How see below.
8. There is a difference from BLS if we are simultaneously
ventilating with a bag and mask: o Ratio of compressions:breaths is
30:2 o during inspirations we interrupt the compressions for about
5 s.
3. Defibrillation The principle of defibrillation is a discharge
which causes a synchronized depolarization of all
cardiomyocytes that then become refractory, thus an opportunity
appears of making a new heart rhythm capable of generating
perfusion (ideally a sinus one).
Defibrillation therefore has a purpose if the electrical
activity of the ventricles is preserved which is albeit chaotic or
quite fast (more than the max. effective frequency). We call these
rhythms defibrillatable rhythms: o ventricular fibrillation (VF) o
ventricular tachycardia without an effective circulation (pVT).
Defibrillation is not indicated (is not meaninfful) in: o
asystole (no electrical activity – there is nothing to synchronize)
o arrests with a normal or organized rhythm (this already are
synchronous, so nothing to
synchronize) o severe bradycardia or blocks (also is
synchronous)
Defibrillation must occur as soon as possible, but it is usually
preceded by compressions (before a defibrillator is available).
Beware! Timely defibrillation increases secondary survival with
a good neurological result in up to 40 % (in asystole it is 6-15
%).
How see further studies.
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 10
4. Ventilation In sudden cardiac arrests tha tis witnesssed or
the duration is short and clearly documented it is
possible to omit ventilations for about 5 minutes (cf. O2 stores
in the body and also gasping). We can ventilate with a bag or
ventilator through a mask or with another aid that secures the
airways. Ventilation with a bag and a mask is done synchronically
with compressions with a ratio of 30:2 A breath should last at
max.1s, interrupting compressions at max. 5s. Ventilating with a
positive overpressure isn't physiological and has its risks:
o worsens venous return o may lead to an inflation of the
stomach with a risk of aspiration.
How to ventilate with a mask see the introductory lab protocol
for the summer semester. Beware! The preparation of a resuscitation
bag or securing the airways musn't delay the start of chest
compressions or cause long term interruptions.
5. Teamwork We can presume that in ALS there will be a
cooperation of some professionals. For teamwork to be effective, it
must be coordinated (and practiced). Otherwise a group can be
counterproductive. Managing critical situations in medicine is for
now partly neglected. It's called CRM (crisis resource management)
and it has sophisticated methodics, especially in the military, and
critical . Here are just the principles, the details will be in
higher grades. And what is even more important here is practice
One leads regardless the number of team members. Ideally the
leader doesn't do anything else. If 2 rescuers:
o the leader is behind the head, monitors, ventilates and
compresses the chest o the second member of the team does
everything else (see below)
If more rescuers: o one monitors breathing and circulation - if
the team is small, it is always the leader o one provides
ventilation, takes care of the airways, eventually secures them
with aids (this is
also usually done by the leader, who again is standing behind
the head) o one simply compresses the chest. o one connects and
works with the monitor along with the defibrillator o one secures
the entrance to the vasculature and administeres drugs per
instruction by MD o eventually one takes care of the protocol
More on Chest Compressions The main goal is to substitute the
function of the mechanical function of the heart as soon as
possible, Compressions by themselves usually don't renew heart
functions. Procedure:
o Begin immediately, definitely and without delay o In the
middle of the chest, between the nipples, straight down. (Compare
the location of the heart in
the chest) We usually compress with both of our palms together.
What is significant is obviously the result, not the technique.
(it's possible to do it with one hand, two hands, from the side,
head…)
o Depth 5-6 cm, child 1/3 anteroposterior line of the chest.
Beware! insufficient depth decreases effectiveness
significantly.
o Frequency 100 – 120 /min Beware! Slow frequencies cause an
insufficient cardiac output, the return is quite fast and
insufficient along with the filling of the heart.
o Do not interrupt (or for just a few seconds only!). Beware!
There needs to be a sufficient pressure for perfusion. The pressure
becomes sufficient after about 1 minute of good uninterrupted
compressions, During interruptions the pressure falls to zero after
a few seconds. That's why it's very important not to interrupt
compressions and to uphold the ratio of compressions:ventilation
30:2 (compared to the former 5:1 or 15:2).
-
Phys SIM Labs B3 – ICM Basics ver 12032017 Page | 11
Did you get stuck? Try the concept "10 seconds -for-10 minutes“
(M. Rall, modified)h
1. Problem?
Ask yourself and all of your team members, ‘What is the biggest
problem right now?’ – ‘What is the most dangerous aspect of the
problem?’ (‘What outcome would I like to have least?’).
2. Opinions? Clarify the above with all available team members.
3. Facts? Gather available information. 4. Plan?
Using input from the team, make a treatment plan. This includes
the plan as well as the sequence of actions. On many occasions we
observed team leaders giving orders as ideas came to mind, not
necessarily in order of priority.
5. Distribute?
Distribute the workload by assigning tasks and responsibilities.
This may include such activities as reporting on thresholds, e.g.:
‘Keep an eye on O2 saturation and let me know if it falls below
94%.’
6. Check!
Before diving into work, involve all team members again to
encourage them to raise any further concerns or suggestions for
improvement or refinement.