Post-Operative Cardiac Assessment and Common Complications, by Dorothy Beke.
Health care workers in all health care settings should always adhere to the latest World Health
Organization guidelines on hand hygiene and barrier precautions before and after contact
with a patient, bodily fluids, or patient surroundings.
For more information, please watch our video entitled "Hand Hygiene."
Hello, my name is Dorothy Beke.
I'm a clinical nurse specialist in the cardiac intensive care unit at the Children's Hospital
in Boston.
I will discuss cardiac issues related to nursing assessment and some common complications associated
with the cardiac post-operative patient.
Physiology.
In order to give the next several slides context, it's important to understand this formula.
Cardiac output equals heart rate times stroke volume.
Specifically, heart rate depends on both rate and rhythm.
Stroke volume depends on preload, contractility, and afterload.
Preload is the volume of blood in the heart during filling or diastole and reflects the
circulating intravascular volume.
Contractility refers to the heart muscle performance as a pump.
Afterload is the resistance of blood flow out of the heart.
Pulmonary vascular resistance is resistance of blood from the right ventricle to the lungs.
Systemic vascular resistance is the resistance of blood from the left ventricle to the body.
The pediatric heart is different.
Cardiac output is much more dependent on heart rate.
Tachycardia, or elevated heart rate, is one of the first signs of low cardiac output or
a heart that is working hard.
Nursing Physical Exam.
After establishing a baseline, perform this nursing physical exam within the hour of returning
from the operating room.
The cardiac physical exam includes evaluation of cardiac output by assessing vital signs,
heart sounds, temperature, pulses, peripheral profusion, and capillary refill.
The respiratory exam includes assessing breath sounds, observing chest rise and symmetry,
and assessing oxygen saturation and end tidal carbon dioxide.
The neurologic exam includes hourly assessment of the patient's pupil size and reaction to
light and assessment of level of consciousness until awake.
Patients are at risk for neurologic injury after cardiopulmonary bypass.
In order to identify pain while the patient is anesthetized, vital signs should be monitored.
Increased heart rate and blood pressure could indicate pain.
Once the patient moves, developmentally appropriate pain scales, if available, are used to score
a level of pain in response to treatments.
Assessment of gastrointestinal system includes measuring the patient's abdominal girth over
the umbilicus, assessing bowel sounds and palpating for liver enlargement, which may
be a sign of right heart failure.
Urine output should be assessed as a measure of renal perfusion.
The patient should also have serum electrolytes, creatinine, and blood urea nitrogen values
assessed as well, although the creatinine and BUN values, or blood urea nitrogen values,
may not be as accurate initially immediately after cardiopulmonary bypass.
In addition to serum electrolytes, initial blood work after cardiac surgery should include
an arterial blood gas analysis, ionized calcium, serum lactate, hematocrit and hemoglobin,
platelet count, and coagulation studies if the patient has had a cardiopulmonary bypass
run.
If the patient has central venous access such as an internal jugular central venous line,
than a mixed venous oxygen saturation should be obtained.
Initial Management and Monitoring.
Patients who are on cardiopulmonary bypass are placed on half of the usual maintenance
fluids for the first 24 hours.
Cardiac patients are at risk for skin breakdown because of decreased cardiac perfusion, immobility,
decreased oxygen saturation, and inadequate nutrition.
Patients must be repositioned every two hours to change pressure points.
Infants and small children are at greater risk for pressure wounds to the back of the
head, or occiput.
Larger patients are at greater risk for pressure-related wounds to the sacrum or lower back region.
Clinical Pearl: Repositioning to Change Pressure Points.
I'm going to reposition this patient to move the pressure off the bony prominences that
we've pointed out.
One of the most important things for us is to have the heels off the end of the bed.
So whatever you have at your disposal to use that's a soft device to lift the heels off
the end of the bed is adequate.
Other prominences that you'd want to cushion are the elbows and wrists.
And here, I'm just using blankets-- nice soft receiving blankets.
And either a pillow or a gel pillow under the head.
When we turn the patient, we can see there are other pressure areas on the coccyx, even
along the spine and on the scapula.
Those two need to be considered when we're moving the patient and taking pressure off
those points.
Mixed venous saturation and serum lactate are the two best measures to predict low cardiac
output.
Mixed venous saturation is one of the first values to change and is an early indicator
of myocardial dysfunction.
Mixed venous saturation is 72-75% in normal two ventricle physiology patients.
Mixed venous saturation should not be more than 30 points lower than arterial oxygen
saturation.
In two ventricle physiology patients, mixed venous saturation is best obtained from a
pulmonary artery catheter.
Otherwise, mixed venous saturation may be obtained from the internal jugular catheter.
Serum lactate will rise when tissues are not being adequately oxygenated as a result of
poor cardiac output.
Acid-base balance is another indicator of cardiac output.
In patients with decreased cardiac output, metabolic acidosis will develop as a result
of inadequate tissue perfusion and oxygenation.
Monitoring end organ perfusion includes assessment for neurologic injury, renal dysfunction,
and injury to other organ systems.
Rewarming after cardiac surgery causes the patient to vasodilate, decreasing cardiac
preload leading to tachycardia.
You need to replace volume as needed.
Temperatures above 37 degrees Celsius may be treated with paracetamol or acetaminophen
and external cooling measures.
Increased temperature raises the metabolic demand of the heart, making it work harder
and causing greater oxygen consumption.
Research indicates that for every one degree rise in Celsius, there is as much as an 11%
increase in myocardial oxygen consumption.
Rapidly rising temperatures above normal may worsen a neurologic injury, or decrease the
seizure threshold.
Therefore, patient rewarming should be done slowly.
Complications.
Causes of low cardiac output after cardiac surgery include factors related to cardiopulmonary
bypass.
These include the inflammatory response, myocardial ischemia related to aortic cross-clamp, reperfusion
injury, inadequate myocardial protection, alterations in pulmonary and systemic vascular
resistance, and ventriculotomy incision.
Other factors include cardiac arrhythmias, cardiac tamponade, and residual cardiac lesions.
If the patient presents with signs of low cardiac output, residual anatomic lesions
should be ruled out.
Sources of residual lesions may include an aortic arch obstruction, a ventricular septal
defect, or any other lesion that may impair forward flow of blood through the heart and
out of the aorta.
Assess saturations and intracardiac pressures, laboratory studies, and changes in vital signs.
If pulmonary artery saturation is greater than 80%, residual ventricular septal defect
with left to right flow should be suspected.
An echocardiogram may be helpful in diagnosing a problem.
Cardiac catheterization may be needed for diagnosis and intervention.
Residual anatomic lesions may need to be corrected to avoid persistent low cardiac output.
It's important to distinguish surgical bleeding from nonsurgical bleeding.
Surgical bleeding is bleeding that requires re-operation.
Non-surgical bleeding can be corrected by treating abnormal clotting factors.
Abnormal values should be treated with the appropriate blood products.
The patient may need volume replacement to maintain preload and hematocrit.
Hypertension should be avoided and treated.
Hypertension may cause excessive bleeding from fresh suture lines, or may lead to wound
dehiscence.
If bleeding continues despite treatment and blood loss is greater than 10 mL/kg/hr, surgical
bleeding should be suspected.
This requires re-operation for internal bleeding.
Although hyperthermia should be avoided, if the patient's body temperature is too low,
clotting abnormalities may persist.
Clotting occurs best if temperature is closer to normothermia.
Chest tubes should be kept patent to avoid cardiac tamponade.
Cardiac tamponade is a clinical syndrome caused by the accumulation of fluid in the pericardial
space resulting in reduced ventricular filling and hemodynamic compromise.
Patients may develop cardiac tamponade as a result of bleeding.
The clinical signs of tamponade not may include a large amount chest tube drainage that suddenly
decreases or stops.
The patient develops an increased heart rate, increased filling pressures, and decreased
blood pressure or narrow pulse pressure.
Low blood pressure is a late sign of tamponade.
Cardiac tamponade is a surgical emergency.
These signs and symptoms need to be addressed immediately.
The blood around the heart must be drained before the patient develops cardiac arrest.
Please help us improve the content by providing us with some feedback.