Transcript Treatment of low cardiac output

Cardiovascular Hemodynamics
Michael J. Lazar, MD
The Big Picture
What is our goal in the ICU for cardiac
surgery patients?
 End-organ perfusion

– Keeping the blood pressure high enough to
perfuse the tissues
– Keeping the delivery of oxygen adequate
 Oxygen Consumption
 Oxygen Delivery
Cardiac Inotropes
4/8/2017 2
Topics of the Day
Blood Pressure
 Cardiac Output- why do we really care
 What is and how do you fix Oxygen
Delivery
 When, why and how to use pressors
 What medications do cardiac patients go
home on

Cardiac Inotropes
4/8/2017 3
General Range of Blood Pressure
Postop SBP < 130 secondary to concerns
for suture lines and bleeding
 Aneurysms SBP around 100
 Preop levels +/- 10%

– Gradual decrease to “normal” levels

Why do we care?
Cardiac Inotropes
4/8/2017 4
Blood Pressure and Flow

Organs are able to
autoregulate blood flow
within a given range of
pressures

Outside this range they
loose the ability to control
their local environment
and depend entirely on the
systemic pressure

The brain and kidneys are
particularly sensitive to
alterations in blood
pressure
Cardiac Inotropes
4/8/2017 5
Obviously pressure is only part of
the story
The body will maintain blood pressure at
all costs
 When cardiac output is low, pressure is
increased by peripheral vasoconstriction
 This allows a driving pressure to certain
organs but reduces flow to others
 How does this occur?

Cardiac Inotropes
4/8/2017 6
Distribution of Cardiac Output
• Increases in cardiac
output are regulated by
individual organs
• Within limits the flow can
be modified by local
changes in vascular tone
• At extremes of blood
pressure, both high and
low, local regulation is
ineffective.
Cardiac Inotropes
4/8/2017 7
Flow By Organ System
Organs vary in range of blood flows and these are generated by
adjustments in the tone of the resistance arteries and arterioles of
the organ vessels
Brain
Heart
Gut
Renal Muscle Skin
Bone
ml/min per 100 g
-------------------------------------------------------------------------------Basal
60
75
100
400
5
10
3
Maximal
120
400
150
420
200
350
5
Minimal
55
70
30
30
3
3
2
Several patterns:
high basal, little further at max:
kidney
low basal, high max:
skeletal muscle, skin
basal near minimal:
heart, brain
Cardiac Inotropes
4/8/2017 8
Detecting a problem


blood pressure
compensatory sympathetic stimulation
– tachycardia
– sweating
– vasoconstriction

organ dysfunction
– mental state
– urine output

tissue hypoxia
– pH
– lactate
Cardiac Inotropes
4/8/2017 9
Expected values following
cardiac surgery
Mean arterial pressure (MAP)
70–95 mm Hg
Systolic blood pressure (SBP)
90–140 mm Hg
Right atrial pressure (RAP)
5–15 mm Hg
Left atrial pressure (LAP)
5–15 mm Hg
Cardiac index (CI) = CO/BSA
2.0– 4.4L/min
Systemic vascular resistance (SVR)
SVR = (MAP - RAP/CO) x 80
SVRI = (MAP - RAP / CI) x 80
1400–2800 dyn·s·cm5/m2
Cardiac Inotropes
4/8/2017 10
Topics of the Day
Blood Pressure
 Cardiac Output- why do we really care?
 What is and how do you fix Oxygen
Delivery
 When, why and how to use pressors
 What medications do cardiac patients go
home on?

Cardiac Inotropes
4/8/2017 11
Oxygen Delivery





The body needs oxygen to live
Oxygen delivery is the body’s capacity to deliver
this oxygen
The delivered oxygen must be more than the
oxygen consumed
SVO2 as the gold standard for delivery
consumption mismatch
Ideally we would rather increase oxygen delivery
rather than decrease consumption -- How?
Cardiac Inotropes
4/8/2017 12
Oxygen Delivery
Oxygen
Delivery
(DO2)
Cardiac Output
(CO)
Oxygen
Content
Cardiac Inotropes
4/8/2017 13
Oxygen Delivery
DO2 = Oxygen Content x Cardiac Output
=(1.38 x Hgb x SaO2 + Pa02 x .0031) x HR x SV x 10
Things to fix :
1. Hemoglobin
2. Saturation
3. Cardiac Output
Cardiac Inotropes
4/8/2017 14
Oxygen Delivery
Oxygen
Delivery
(DO2)
Cardiac Output
(CO)
Heart Rate
(HR)
Oxygen
Content
Stroke Volume
(SV)
Hemoglobin
(Hgb)
Cardiac Inotropes
Hemoglobin
Saturation
(PaO2)
4/8/2017 15
Oxygen Content

Hemoglobin – Transfuse to ≈ 10 g/dL
– Most efficient delivery of oxygen through
capillary beds
– pAO2 contributes little to oxygen delivery

Oxygen Saturation ≈ 100%
– Concern for oxygen toxicity
– Increased PEEP can decrease CO (best PEEP)
Cardiac Inotropes
4/8/2017 16
Importance of
Hemodynamics
Oxygen
Delivery
(DO2)
Cardiac Output
(CO)
Heart Rate
(HR)
Oxygen
Content
Stroke Volume
(SV)
Hemoglobin
(Hgb)
Cardiac Inotropes
Hemoglobin
Saturation
(PaO2)
4/8/2017 17
Importance of Hemodynamics
Cardiac Output
(CO)
Heart Rate
Stroke Volume
Preload
Contractility
Cardiac Inotropes
Afterload
4/8/2017 18
The Starling Curve
Different lines
represent
different
contractile states
 Volume status
moves the
patient along
each line

Cardiac Inotropes
4/8/2017 19
How do we measure LV preload?
Wedge Pressure
The wedge is an estimate of the End
Diastolic Pressure of the Left Ventricle
 This is in turn an estimate of the End
Diastolic Volume of the LV
 This is the preload from the startling
curve.

Cardiac Inotropes
4/8/2017 20
The Gold Standard
TTE –
Transthoracic
echocardiogram
 TEE –
Transesophageal
echocardiogram
 Direct
visualization of
the Left Ventricle

Cardiac Inotropes
4/8/2017 21
Cardiac Inotropes
4/8/2017 22
Mitral Regurgitation
Cardiac Inotropes
4/8/2017 23
Aortic Stenosis
Cardiac Inotropes
4/8/2017 24
Importance of Hemodynamics
Cardiac Output
(CO)
Heart Rate
Stroke Volume
Preload
Contractility
Cardiac Inotropes
Afterload
4/8/2017 25
The Starling Curve
Afterload is the force
the heart beats
against
 No blood is ejected
until vascular
resistance is
overcome
 As afterload is
reduced, more of
the cardiac energy is
used to eject blood.

Cardiac Inotropes
4/8/2017 26
How do we measure Afterload?
Systemic vascular
resistance
 SVR = (MAP RAP/CO) x 80
 This is a calculated
number depends on
each of the
parameters of the
equation.

Cardiac Inotropes
4/8/2017 27
Importance of Hemodynamics
Cardiac Output
(CO)
Heart Rate
Stroke Volume
Preload
Contractility
Cardiac Inotropes
Afterload
4/8/2017 28
Topics of the Day
Blood Pressure
 Cardiac Output- why do we really care
 What is and how do you fix Oxygen
Delivery
 When, why and how to use pressors
 What medications do cardiac patients go
home on

Cardiac Inotropes
4/8/2017 29
Commonly Used Postoperative Medications
Dopamine
Medication
Dopamine
Clinical effect
Adverse effect
At 2–3 µg/kg/min, mainly renal Raises
vasodilation via dopaminergic
myocardial O2
receptors
consumption
At 4–10 µg/kg/min, mainly
positive inotropic and
chronotropic effects via beta1
receptors
Dosing(IV)
2.0–20
µg/kg/min
Arrhythmogenic
At >10 µg/kg/min, mainly raises
BP and SVR via alpha receptors
Receptor stimulation overlap
Cardiac Inotropes
4/8/2017 31
Commonly Used Postoperative Medications
Epinephrine
Medication
Epinephrine
Clinical effect
Positive inotrope
Positive chronotrope
Adverse effect
Dosing(IV)
Increases myocardial
O2 consumption
0.008–0.06
µg/kg/min
(0.5–4.0 µg/min)
Tachycardia
At low doses, causes
vasodilation from beta2
activity
>2µg/min raises BP via
increasing alpha;
activity
Arrhythmogenic
High doses can
exacerbate metabolic
acidosis from alpha
effect
Cardiac Inotropes
4/8/2017 32
Commonly Used Postoperative Medications
Norepinephrine
Medication
Clinical effect
Norepinephrine
Raises BP and SVR
Less positive
inotropy
Adverse effect
Dosing(IV)
Increases myocardial O2
consumption
0.03–0.3
µg/kg/min
Intense vasoconstriction
can lead to visceral and
renal ischemia
(2.0–20 µg/min)
Exacerbates metabolic
acidosis by increasing
anaerobic glycolysis and
lactate production
Exacerbates hyperglycemia
Cardiac Inotropes
4/8/2017 33
Commonly Used Postoperative Medications
Phenylephrine
Medication
Clinical effect
Adverse effect
Phenylephrine Raises BP and SVR
Often reflex decrease in
HR
Useful in patients with
high cardiac index and
severely vasodilated
Dosing(IV)
Increases myocardial
O2 consumption
0.15–3.0
µg/kg/min
Tolerance develops
(10–200 µg/min)
Can cause visceral
and renal ischemia
Can exacerbate
metabolic acidosis
Cardiac Inotropes
4/8/2017 34
Commonly Used Postoperative Medications
Milrinone
Medication
Milrinone
Clinical effect
Positive inotrope
Adverse effect
Hypotension
Decreases SVR
Decreases pulmonary vascular
resistance (ideal for RV failure)
Dosing(IV)
Loading dose:
50–75 µg/kg
Maintenance:
0.25–0.75
µg/kg/min
Decreases coronary vascular
resistance
Most favorable effect on
myocardial O2 consumption
Cardiac Inotropes
4/8/2017 35
Commonly Used Postoperative Medications
Nitroprusside
Medication
Nitroprusside
Clinical effect
Adverse effect
Arterial vasodilatation
Reflex tachycardia
Increases venous
capacitance
Inhibition of hypoxic
pulmonary vasoconstriction
( V/Q mismatch )
Decreases SVR and PVR Tachyphylaxis
Rapid onset
Short half-life
Dosing(IV)
0.3–10
µg/kg/min
Usual dose:
0.3–4.0
µg/kg/min
Cyanide toxicity
–Metabolic acidosis
–Methemoglobinemia
Thiocyanate toxicity
–Seizures
–Psychosis
Cardiac Inotropes
4/8/2017 36
Commonly Used Postoperative Medications
Nitroglycerin
Medication
Nitroglycerin
Clinical effect
Adverse effect
Dosing(IV)
Increases venous capacitance Tolerance can occur
(major effect)
with continuous
dosing
0.1–10
µg/kg/min
(10–700
Coronary vasodilatation
µg/min)
Methemoglobinemia
Decreases SVR and PVR (less
than nitroprusside
Cardiac Inotropes
4/8/2017 37
Commonly Used Postoperative Medications
Calcium
Medication
Calcium
Clinical effect
Positive inotrope
Adverse effect
Temporary effect
Dosing(IV)
1g CaCl
Stabilizes myocardial
membranes in setting of
hyperkalemia
Cardiac Inotropes
4/8/2017 38
Commonly Used Postoperative Medications
Triiodothyronine
Medication
Triiodothyronine
Clinical effect
Adverse effect
Positive inotrope
Tachycardia
Decreases SVR
May be arrhythmogenic
Dosing(IV)
Loading dose:
0.4–0.8 µg/kg
in OR after xclamp
removed
Maintenance:
0.1–0.12
µg/kg/h over
6h
Cardiac Inotropes
4/8/2017 39
Hmmm
That’s way too
much
information to
remember
 Lets look at
how these
drugs work

Cardiac Inotropes
4/8/2017 40
Alpha receptors

alpha1 receptors:
– post synaptic cardiac - stimulation causes significant increase in
contractility without an increase in rate
– effect more pronounced at low heart rates
– slower onset and longer duration than beta1 response

alpha2 receptors:
– presynaptic in heart and vasculature
– appear to be activated by norepinephrine released by
sympathetic nerve itself and mediate negative feedback
– inhibition of further norepinephrine release

post synaptic alpha1 and alpha2 receptors in peripheral
vessels mediate vasoconstriction
Cardiac Inotropes
4/8/2017 41
Beta receptors
post synaptic beta1 receptors are
predominant adrenergic receptors in heart
 Stimulation causes increased rate and
force of cardiac contraction.
 post synaptic beta2 receptors in
vasculature mediate vasodilatation

Cardiac Inotropes
4/8/2017 42
Dopamine receptors
peripheral DA1 receptors mediate renal,
coronary and mesenteric arterial vasodilatation
and a natriuretic response
 DA2 receptors:

– presynaptic receptors found on nerve endings
– inhibit norepinephrine release from sympathetic nerve
endings
– inhibit prolactin release and may reduce vomiting

stimulation of either DA1 or DA2 receptors
suppresses peristalsis and may precipitate ileus
Cardiac Inotropes
4/8/2017 43
Receptor pharmacology
Agent
Alpha1 Alpha2 Beta1 Beta2 Dopamine
Dobutamine
+
+
++++ ++
0
Dopamine
++/+++
?
++++ ++
++++
Epinephrine
++++ ++++ ++++ +++
0
Norepinephrine
+++
Phenylephrine
++++ +++
+++
++
+
0
+
+
0
Cardiac Inotropes
4/8/2017 44
Receptor pharmacology
Dopamine
Little bit of everything
Dobutamine
Beta
Epinephrine
Alpha, Beta
Norepinephrine
Apha, small beta
Phenylephrine
Alpha
Milrinone
Like beta
Vasopressin
Like alpha
Cardiac Inotropes
4/8/2017 45
Putting It All Together
Treatment of low cardiac output
(CI < 2.0–2.2 L/min/m2)
1.
Consider surgical complications, including
 Coronary graft occlusion
 Valve malfunction
 Tamponade
 Bleeding
 Coronary spasm
Cardiac Inotropes
4/8/2017 47
Treatment of low cardiac output
(CI < 2.0–2.2 L/min/m2)
2. Optimize heart rate and rhythm
– Increase rate to 90–100 beats per minute
– Atrial pacing if no heart block
– A-V pacing if heart block exists
Cardiac Inotropes
4/8/2017 48
Treatment of low cardiac output
(CI < 2.0–2.2 L/min/m2)
3. Low blood pressure
(SBP <100 mm Hg or MAP <70 mm Hg)
–
If LAP * <15 mm Hg and HCT 25, administer
Ringer's lactate or hetastarch
–
If LAP <15 mm Hg and HCT <25, administer PRBCs
–
If LAP 15 mm Hg, start dopamine or other inotropic
agent, then add nipride when MAP >70 mm Hg
Cardiac Inotropes
4/8/2017 49
Treatment of low cardiac output
(CI < 2.0–2.2 L/min/m2)
4. Normal or high blood pressure
(SBP >100 mm Hg or MAP >70 mm Hg)
–
If LAP <15 mm Hg and HCT 25, administer Ringer's
lactate or hetastarch, plus nipride or other vasodilator
–
If LAP <15 mm Hg and HCT <25, administer PRBCs,
plus nipride or other vasodilator
–
If LAP 15 mm Hg, administer nipride/other
vasodilator and consider diuretic
Cardiac Inotropes
4/8/2017 50
Treatment of low cardiac output
(CI < 2.0–2.2 L/min/m2)
5. If CI and BP still low,
place IABP
Cardiac Inotropes
4/8/2017 51
When all else fails
Remember that if
nothing more can be
done about delivery, we
can often do something
about consumption
 Limiting stressors is a
start
 Paralytics are a last
resort

Cardiac Inotropes
4/8/2017 52
Oxygen Consumption

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




Fever 10%
Shivering 50-100%
ET Suctioning 7-70%
Sepsis 50-100%
Visitor 22%
Position Change 31%
Weighing 36%






Work of Breathing
40%
Procedure 7%
MSOF 20 - 80%
Dressing Change 10%
Bath 23%
CXR 25%
Cardiac Inotropes
4/8/2017 53
Topics of the Day
Blood Pressure
 Cardiac Output- why do we really care?
 What is and how do you fix Oxygen
Delivery
 When, why and how to use pressors
 What medications do cardiac patients go
home on?

Cardiac Inotropes
4/8/2017 55
Beta-Blockers
Beta-blockers should be used as a firstline medication to prevent postoperative
atrial fibrillation
 Researchers found that beta-blockers used
in patients undergoing heart surgery
decreased the incidence of post-operative
atrial fibrillation (AF) and shortened
hospital stay

Cardiac Inotropes
4/8/2017 56
Discharge Medications






Metoprolol 50mg PO BID
ECASA 325mg PO daily
or
ASA 81mg & Plavix 75mg daily
ACE inhibitor if needed
Norvasc 5mg PO daily
Imdur 30mg PO daily
No routine nitrates or calcium channel blockers
Cardiac Inotropes
4/8/2017 57
Discharge Medications

Coumadin 5mg daily
really dosed by INR and followed with coumadin clinic

Coumadin 5mg daily
Amiodarone 200mg BID
– Then 200 daily for 3 months

Lasix 40mg daily
KDur 40meq daily
Cardiac Inotropes
4/8/2017 58
Thank You
Cardiac Work
minute work of the heart = HR x SV x
developed pressure,
 A rise in heart rate, a rise in stroke
volume, and a rise in aortic pressure all
lead to a rise in oxygen consumption

Cardiac Inotropes
4/8/2017 60
Placing a PA Catherter

On a rare day at the beach in California,
H.J.C. Swan noticed a sailboat moving
quickly despite the calm weather. This led
to the initial idea of devising a catheter
with a parachutelike or sail-like device
attached.
Cardiac Inotropes
4/8/2017 61
When does the Wedge not Reflect
Preload?
1. PAWP
is less than LVEDP
2. PAWP
is greater than LVEDP
3. PAWP
equals LVEDP, but LVEDP does
not correlate with LVEDV
*Ideal Situation--PAWP equals LAP equals LVEDP, and LVEDP is
proportional
to LVEDV. When this is true, PAWP can he used as a measure of left
Cardiac Inotropes
4/8/2017 62
ventricular preload.
When does the Wedge not Reflect
Preload?
1. PAWP
is less than LVEDP
– Aortic regurgitation
– Reduced left ventricular compliance
2. PAWP
is greater than LVEDP
3. PAWP equals LVEDP, but LVEDP does
not correlate with LVEDV
Cardiac Inotropes
4/8/2017 63
When does the Wedge not Reflect
Preload?
1.
PAWP is less than LVEDP.
2.
PAWP is greater than LVEDP.
 When catheter tip is in Zone 1 or 2;
 may occur from artificial ventilation, with or without PEEP or
 from volume depletion Atrial myxoma
 Thoracic tumors pressing on pulmonary veins
 Mitral stenosis or regurgitation
 Increased left ventricular compliance
3.
PAWP equals LVEDP, but LVEDP does not
correlate with LVEDV
Cardiac Inotropes
4/8/2017 64
When does the Wedge not Reflect
Preload?
1.
PAWP is less than LVEDP
2.
PAWP is greater than LVEDP
3.
PAWP equals LVEDP, but LVEDP does not
correlate with LVEDV
•Decreased left ventricular
compliance
•Increased left ventricular compliance
•Increased right ventricular volume
•Decreased right ventricular volume
•Pericardial tamponade
•Removal of pericardium
•Some drugs, e.g., isoproterenol
•nitroglycerin
Cardiac Inotropes
•High LVEDV
•Low LVEDV
•Tachycardia
•Bradycardia
•PEEP
•Myocardial ischemia and
infarction
•Myocardial hypertrophy
4/8/2017 65