Optimizing Cardiac Output After Surgery, by Dorothy Beke.
Hello.
My name is Dorothy Beke.
I'm a clinical nurse specialist in the Cardiac Intensive Care Unit at the Children's Hospital
Boston.
In this video on post-operative considerations after pediatric cardiac surgery, I will discuss
issues related to optimizing cardiac output in the post-operative pediatric cardiac patient.
Maintaining Cardiac Output.
Preserve myocardial function and minimize oxygen consumption by decreasing stress to
the heart.
Too much inotropic support, such as with dopamine or epinephrine, causes the heart to work harder,
produces cardiac arrhythmias, and increases both systemic and pulmonary vascular resistance.
Low intracardiac or central venous pressures will cause tachycardia and decreased peripheral
perfusion.
Fluid boluses of 5 to 10 milliliters per kilogram may be indicated to ensure adequate cardiac
preload.
Monitor for Increased Systemic and Pulmonary Vascular Resistance.
Increased pulmonary vascular resistance may be due to excessive pulmonary blood flow,
inflammatory and ischemic responses related to cardiopulmonary bypass, edema, or prolonged
mechanical ventilation.
Increased systemic vascular resistance may be related to left ventricular failure, cardiopulmonary
bypass, hypoxia, acidosis, or low body temperature, or pain.
Measures to decrease pulmonary and systemic vascular resistance include adequate mechanical
ventilation and oxygenation, analgesia and sedation as well as afterload reducing agents
such as nitroprusside.
Milrinone has both inotropic and afterload reducing effects.
Maintain cardiac output for improving cardiac contractility with inotropic medications such
as dopamine, and by maintaining normal acid-base balance and adequate tissue oxygenation.
Normal sinus rhythm will optimize cardiac output.
Milrinone.
The PRIMACORP trial was one of the few multi-centered, randomized, double blinded, placebo-controlled
trials of a pediatric cardiovascular drug.
Milrinone is a non-catecholamine inotropic agent with vasodilatory and lusitropic or
cardiac relaxation effects.
It has been shown to improve cardiac output while lowering filling pressures and systemic
and pulmonary vascular resistance with minimal cardiac oxygen consumption.
In the PRIMACORP trial, patients were randomized to high-dose Milrinone of 0.75 micrograms
per kilogram per minute, 1/3 were randomized to low-dose Milrinone of 0.25 micrograms per
kilogram per minute, and 1/3 were randomized to placebo.
The prophylactic use of Milrinone in a 64% relative risk reduction in developing low
cardiac output syndrome and the first 36 hours after cardiopulmonary bypass with high-dose
Milrinone of 0.75 micrograms per kilogram per minute.
Low Cardiac Output Syndrome.
In this study by Wernovsky and colleagues, they compared two cardiopulmonary bypass strategies
of infants with transposition of the great arteries, following an arterial switch operation.
This study found that there was a median maximal decrease in cardiac index by 33%, which occurred
6 to 12 hours after cardiopulmonary bypass.
25% of the patients developed a cardiac index of less than two liters per minute, per meter
squared, in their first night following surgery.
When cardiac index is less than two liters per minute, per meter squared, mortality and
morbidity may be higher.
Low cardiac output is common and can be predicted after complex pediatric heart surgery.
Patients may be most critical during this identified timeframe, and care should be taken
to avoid stressful interventions, which may cause the patient to deteriorate.
Also, this study demonstrated that as cardiac output decreased, both pulmonary and systemic
vascular resistance increased.
Post-operative management strategies should focus on anticipating and managing low cardiac
output before it occurs.
Cardiac Arrhythmias.
Over 25% of pediatric patients have cardiac arrhythmias after cardiac surgery.
Risk factors for developing arrhythmias are volume overload, ventricular hypertrophy,
myocardial ischemia, ventriculotomy incision, multiple suture lines, and serum electrolyte
disturbances.
Treat cardiac arrhythmias in order to optimize cardiac output, especially in an unstable
patient.
An electrocardiogram and atrial wire tracing will help to diagnose the rhythm.
Treatments of arrhythmias include anti-arrhythmic medications, maintaining normal electrolyte
levels, especially potassium, magnesium, and calcium.
Induced hypothermia will slow cardiac conduction and decrease the heart rate.
If the patient has pacing wires, use external cardiac pacing to improve cardiac conduction.
Pacing Wires.
In the operating, two atrial wires may be placed on the right atrium, and two ventricular
wires may be placed on the right ventricle.
These wires are used to externally pace the atrium and ventricle when an abnormal rhythm
occurs and leads to a decrease in cardiac output.
Pulmonary Hypertension.
Normal pulmonary artery pressure is usually 15 mmHg, and should be less than 1/2 the systemic
blood pressure.
Common causes of post-operative elevated pulmonary artery pressure include anatomical obstruction
to pulmonary blood flow, such as pulmonary valve stenosis, or branch pulmonary stenosis;
residual intracardiac left-to-right shunts; or a large pre-operative left-to-right shunt,
such as with a large ventricular septal defect.
A pulmonary hypertension crisis presents with a low oxygen saturation.
Immediate intervention is indicated.
Common causes of pulmonary hypertensive crisis are hypoxemia and hypoventilation, acidosis,
and hypercarbia, and these can be produced by suctioning the endotracheal tube.
Extra care should be taken when suctioning a high risk patient.
Consider sedating and instilling lidocaine into the endotracheal tube, prior to suctioning,
to decrease bronchospasm.
Other causes the pulmonary hypertensive crisis are hypothermia, alpha-adrenergic inotropes,
such as epinephrine, and environmental stressors, including pain.
Optimal ventilation is necessary to avoid and treat pulmonary hypertension.
If a pulmonary hypertensive crisis occurs, prompt action must be taken so the patient
does not have a cardiac arrest.
The patient should be hyperventilated with 100% oxygen while sedation and analgesia medications
are administered.
Consider paralysis.
The patient should be maintained alkalotic, and the administration of sodium bicarbonate
should be considered.
Afterload reducing agents are helpful, however, inhaled nitric oxide, if available, is the
treatment of choice.
Nitric oxide is a selective pulmonary vasodilator, which directly affects the lung vasculature
and has no systemic vascular effects.
Summary.
So in summary, of all the nursing considerations for post-operative management for pediatric
cardiac surgical patients, it's important to remember that interdisciplinary sign out
is crucial to managing post-operative cardiac patients.
Thorough nursing assessment is required to monitor trends and changes.
Many post-operative complications can be predicted and the appropriate management strategies
can be implemented before a patient deteriorates.
Skilled communication within the team is critical for prompt intervention and optimal patient
management.
Patient outcomes are dependent on good clinical and communication skills of the bedside nurse.
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