Events during Diastole Events during Systole - AACN

39 Pages·2013·7.58 MB·English

by  Dave Savage

4/6/2013
Cardiac Blood Flow
Beth Torres, PhD, RN, CCRN
CJW Medical Center
1 2
Events during Diastole Events during Systole
Remember: During systole the cardiac muscle has to overcome
The cardiac muscle gets its perfusion during diastole. the pressures ahead of each chamber:
Perfusion is determined by coronary perfusion pressure The right ventricle meets low to no pressure in the lungs.
Coronary Perfusion Pressure = Diastolic BP – PCWP The left ventricle must overcome the diastolic pressure in the
Normal: 60 -80 mmHg 3 aorta. 4

Compensation for Decreased Cardiac Output
Hemodynamics
  cardiac output  heart rate.
 Heart rate is controlled by stimulation of
Cardiac Output = HR x Stroke Volume (SV)
both the sympathetic and
parasympathetic nervous system
Normal Cardiac Output: Heart Rate

4-8liters / minute Preload Cardiac Output

Afterload Stroke Volume

Contractility

Muscle Synchrony
5 6
1
4/6/2013
Stroke Volume (SV) Preload
Stroke Volume- the amount of volume ejected The force on the ventricle during relaxation (diastole)
by the ventricle with each systolic contraction Primary determinant is the volume of blood filling the
ventricle
OR, amount of blood ejected by the heart with Right Ventricle = RVEDP (Right heart preload):
each beat Right Atrial Pressure (RAP); CVP
Normal: 60-130ml Normal values: 2-6mmHg

SV = (CO/HR) x 1000 Left Ventricle = LVEDP (Left heart preload):
PCWP, PAWP, or PAOP
Pulmonary Artery Diastolic (PAD)
Left Atrial Pressure (LAP)
Normal values: 8-12mmHg
7 8
Contractility
Afterload
Defined as the squeezing force generated by the
Afterload—the ventricular force or pressure ventricles.
required to overcome impedance to ejection.
Refers to both the pressures of this ejection and the
As impedance , ejection velocity and SV , amount of blood ejected.
while ventricular workload & O2 consumption 
Manipulate with inotropic drugs

Systemic vascular resistance (SVR): Left
Normal SVR: 900-1400 dynes /sec/cm-5
Best global measure is CO

Pulmonary vascular resistance (PVR): Right
Normal ejection fraction is 50 – 70 %
Normal PVR: 50-250 dynes /sec/cm-5
9 10
Cardiac Index
Supply & Demand
Cardiac Index—a more precise expression of CO,
which takes into account the patient’s size Coronary artery patency Heart rate
Normal CI = 2.5-4.2 L/min Diastolic filling time Preload
Diastolic pressure Afterload
CI < 2.0 is considered cardiogenic shock Hemoglobin Contractility
1.8-2.2 is low perfusion Arterial oxygen saturation
Oxygen extraction by the
Calculate:
tissue Oxygen Demand
Oxygen Supply
CI = CO
BSA
11 Heart 12
2
4/6/2013
Factors of SvO & ScvO
SVO 2 2
2
SVO2 – amount of oxygen in the mixed SaO2 CO
venous blood in the pulmonary artery
Normal SVO: 70-75% (range 60-80%)
2
An estimate of the amount of oxygen
returning to the cardiopulmonary circulation
Reflects the patient’s ability to balance O
2
supply and demand at the tissue level
Hgb
O Tissue
2
Consumption
13 14
Oxygen Delivery
Question
SvO2 = 75% SaO2 = 100%
Which of the following is a normal
Venous
compensatory response to a decrease in
Return
cardiac output?
a. Increased oxygen delivery
b. Decreased oxygen consumption

Oxygen Arterial c. Increased oxygen extraction
Oxygen
Consumption 25% Delivery d. Decreased serum lactate

The Cell
15 16
Cardiac Assessment
Arterial Waveform
Hemodynamic Monitoring Systolic Ejection (A)
Peak of waveform
ECG Interpretation Normal 90-140
Diastole (C) A

Lowest portion of waveform B
Heart Sounds
Normal 60-90
Dicrotic Notch (B)
Closure of Aortic valve
C
17 18
3
4/6/2013
Peripheral Arterial Waveform Review: Right Atrial Waveform
The PA catheter is threaded manually to the
right atrium. A continuous pressure reading
will demonstrate a CVP /RA waveform
Normal RA:
2-6 mmHG
19 20
Preload CVP waveform
What Decreases:
What Increases: Pressure measurement is taken from
Hypovolemia
Vasoconstriction the a waveform (mean) at end-
Position Change
↑ fluid volume expiration
Vasodilation
Right Heart Damage ↑ ventricular filling Normal RA/CVP: 2-6 mmHg
time
Atrial Arrhythmias
Pericardial Effusion Bradycardia
PEEP
Tension
Pneumothorax
21 22
Right Ventricular Waveform Pulmonary Artery Waveform
As the PA catheter floats through the pulmonic valve and
The RV is very irritable and ectopy is a potential
into pulmonary circulation, the pulmonary systolic pressure
complication during PA catheter insertion
remains similar to RV systolic pressure
Watch the monitor closely for Ventricular
The catheter should stay here during continuous
Tachycardia
monitoring. Normal PA:
Sys: 20-30 mmHg
Normal RV:
Sys: 15-30 Dia: 5-10
Dia: 2-6 mmHG Mean: 10-20
23 24
4
4/6/2013
Pulmonary Capillary Wedge Pressure Phlebostatic axis
Apudlvmanocnea ruyn atirlt eitr yb escliogmhtelys lsomdagleledr iant a Normal PCWP: Head of the bed can range from flat to 60 degrees
than the inflated balloon. 4 – 12 mmHG PA pressures may be significantly different in patients
No blood flows distal to the catheter in a lateral position.
tip. Allow 5 minutes for stabilization after changing the
This pressure, the pulmonary artery patient’s position
occlusion pressure (POAP), reflects
LV pressure when the mitral valve
is open.
Resembles CVP waveform. The a
wave falls later in the T-P cycle.
The PCWP should be 1-4 mmHG
lower than the PAD.
IT SHOULD NEVER BE HIGHER!
25 26
Technical Factor:
Technical Factors:
Mechanical Ventilation
Effect of Patient Respirations
If the patient is on a mechanical ventilator, the
positive pressure “pushes up” the PA tracing.
“Ventilator Valleys”
A PEEP > 10 will artificially elevate PA pressures
If patient is breathing spontaneously, the negative
pressure “pulls down” the PA tracing. “Spontaneous
sky”
The most accurate reading is obtained at respiratory
end expiration.
27 28
Technical Factor:
Spontaneous Respirations Afterload
 Normal SVR = 900-1400 dynes/sec/cm3
SVR = MAP-CVP x 80
CO
 MAP = systolic BP + (2) diastolic BP
3
 Example:
 BP = 120/80 (93)
 CVP = 5
 CO = 5
 SVR = [(93 – 5) / 5] x 80 = 1406
29 30
5
4/6/2013
ECG Monitoring
Pulmonary Vascular Resistance (PVR)

Pulmonary Vascular Resistance (PVR) Treatment of Significant Arrhythmias
reflects blood flow through the pulmonary
circulation
The resistance is influenced by the
pulmonary capillaries & arteries
Normal PVR = 50-250 dynes/sec/cm
PVR = MPAP-PCWP x 80
CO
31 32
Conduction System
Refractory Period
KEY CONCEPT: An electrical stimulus landing on
the T wave, may cause disorganized ventricular
33 contractions OR VENTRICULAR FIBRILLATION3 4
Question
Premature Ventricular Contractions
The cardiac monitor shows the rhythm below
for your patient. Which of the following
medications might the physician order?

The complexes have a QRS > .12 seconds.

Significance:
• PVC’s can occur in healthy persons with normal hearts and no a. Atropine
apparent cause.
• Patients can be asymptomatic or feel “racing heart” / skipped b. Adenocard
beats.
• Frequent PVC’s increase risk of fatal arrhythmias x 5. c. Cardizem
• Treat: More than 6/min, multi-focal, R on T configuration
d. Amiodarone
35 36
6
4/6/2013
Amiodarone
A patient with which of the following is at
greatest risk for torsades de pointes?
Dosage:
Non-VT/V.fib: 150 mg IV over 10 min.
Pulseless VT/V.fib: 300mg IV bolus a. Depressed ST segment
b. Tall, tented T waves
Adverse effects: c. Prolonged QT interval
Hypotension and bradycardia are common
during initial bolus. d. u-wave
May be prevented by slowing the rate of
infusion.
37 38
Second Line Drug: Lidocaine
Too Fast
Administration:
Bolus: 1.0-1.5 mg/kg IVP; may repeat in 5-10
minutes to max of 3mg/kg
Infusion: 1-4 mg/min

Does not prolong QT

Adverse effects:
Confusion (most common), seizures,
tremors.

39 40
Sinus Tachycardia
Supraventricular Tachycardia
Rate: 100-150 bpm
Significance:
If very fast, the heart cannot refill & results
in ↓CO
This tachycardia originates above the ventricles, but
below the SA node.
Characteristics:
TREAT THE CAUSE!  Rate: Rapid! Usually 160-250. May start / stop abruptly.
 QRS is normal looking.
 No bizarre, early, or late beats.

 Too fast to see a P wave.
Significance:
 Must treat if prolonged
41 42
7
4/6/2013
SVT Treatment Atrial Flutter
Try VAGAL maneuvers. Significance:
If not effective, administer: Consider this a hazardous rhythm because it can
suddenly change to a rapid ventricular response.

ADENOSINE
Indicated for stable SVT If patient is stable, no initial treatment.
unresponsive to vagal maneuvers.
Dose: 6 mg IV PUSH If ventricular rate is rapid, treatment is required.
12 mg IV PUSH
12 mg IV PUSH

Adenosine depresses sinus & AV node activity.
HALF LIFE: 10 seconds

Not effective in ventricular rhythms. 43 44
Atrial Fibrillation
R-R interval is always irregular Question

Significance: A 69-year-old patient presents to the ED with
If stable or chronic may be tolerated. complaints of palpitations and irregular heart
If patient has symptoms, treatment will be beats for the last three of days. The cardiac
required. monitor shows atrial fibrillation, a heart rate of
136 beats/min. His blood pressure is 124/76 mm
Consider hazardous because ventricular rate
Hg. Which of the following medications would
can suddenly ↑.
the physician likely order?
Also lose atrial “kick”, which is 20% of the CO
a. Lidocaine
b. Cardizem
c. Corvert
d. Adenocard
45 46
To Control Rate,
Irregular Narrow Complex Use Selective β- Blockers
Tachycardia: Control of Rate Non-Selective:
Propranolol (Inderal)
Rate can be controlled by: Nadolol (Corgard)
Selective agents:
Beta Blockers
Atenolol (Tenormin)
Calcium Channel Blockers Betaxolol (Zebeta)
Amiodarone * Metoprolol (Lopressor)
Vasodilatory, Non-selective
*Not considered a first line Labetalol (Normodyne)
agent for narrow complex Carvedilol (Coreg)
Shortest half-life:
tachycardias
Esmolol
47 48
8
4/6/2013
To Control Rate: Ventricular Tachycardia
Use Calcium Channel Blockers Wide & bizarre QRS (> .12 sec)

Significance:
Slows AV node conduction & prolongs AV
Treatment is REQUIRED
nodal refractoriness
Pulse or NO Pulse?

Pulse & STABLE? Use AMIODARONE
Example: Diltiazem
Pulse & UNSTABLE

ELECTRICAL CARDIOVERSION
Do not use in:
Drug-induced tachycardia
Heart blocks
Concurrent use of Beta blockers.
49 50
Question
Electrical Cardioversion
The nurse should perform which of the
following interventions for a patient Immediate electrical cardioversion is indicated
with chest pain, hypotension, and for a patient with serious signs & symptoms
tachycardia at a rate of 180 beats/min? related to tachycardia.
a. Administer amiodarone 150mg IV over 10
min
b. Administer adenosine 6 mg rapid IVP
c. Perform synchronized cardioversion
d. Defibrillate with 300 joules
51 52
Synchronized Cardioversion: Synchronized Cardioversion:
Energy Selection Energy Selection
Start with 100 joules. If the rhythm does not change, recharge to 200 joules
& repeat

Repeat with 300 joules & 360 joules, if needed.

Complications include:
Deterioration into ventricular fibrillation
Push the Synch button! Embolization of a thrombus

53 54
9
4/6/2013
Synchronized Cardioversion:
Too Slow
Pre-Medication
For awake, alert patients who are hemodynamically
stable, pre-medicate with both a sedative and a
analgesic
Sedatives
 Diazepam
Watch for apnea &
 Midazolam hypoventilation after
 Etomidate sedation.
Analgesics
Frequent vital signs are
 Fentanyl required before
 Morphine & after cardioversion
 Merperidine

55 56
Sinus Bradycardia 3Heart Block
Characteristics: Significance:
PREPARE TO PACE!
HR > 60 May be normal in
All intervals within healthy, young New guidelines:
normal limits patient. chronotropic drips
except rate Treat symptomatic
bradycardias!
57 58
Symptomatic Bradycardia Temporary Pacemakers
Treat Bradycardia with BRADE
Use an external generator. 3 types:

Atropine: 0.5 mg IV push Transcutaneous
Repeat every 3 – 5 min to total of 0.04 mg/kg (3 mg)

Transvenous
Dopamine: 2 to 10 mcg/kg/min

Epinephrine gtt: Start at 1 mcg/ min and titrate Epicardial
to patient response.
59 60
10