Learning Objectives
By the end of this section, you will be able to:
- Discuss the pathophysiological changes to the patient’s cardiovascular concerns when in the intensive care unit
- Describe the medical assessments and therapies that apply to the critical care patient’s cardiovascular system
- Apply nursing concepts and plan associated nursing care for the critical care patient’s cardiovascular system
The heart is arguably the most important organ in the body because it is responsible for providing perfusion to all other body systems and organs. Care of the critically ill patient with cardiac dysfunction and impaired CO is challenging because of the complex and invasive therapies required to maintain hemodynamic stability. Critical care nurses must possess the technical expertise to implement and monitor these interventions; they also need superior clinical knowledge and critical thinking skills. Though there are many different cardiovascular conditions experienced by patients in critical care settings, many of them will require the use of hemodynamic monitoring, pharmacological interventions, and invasive cardiovascular support, all of which are discussed in this section.
Pathophysiological Insult to the Critical Care Patient’s Cardiovascular System
The underlying pathophysiologic mechanism of most critical cardiac conditions is a decrease in cardiac output, or the amount of blood the heart ejects each minute. A normal CO is 4–8 liters of blood per minute, illustrating the significance of the heart’s function and the need for consistently maintaining an adequate CO. Bedside hemodynamic monitoring is often implemented in the ICU to assess CO and other parameters to determine the level of functioning of the heart. See Table 35.2 for more information about hemodynamic parameters that are commonly monitored in the ICU.
Principles of Hemodynamic Monitoring
To understand the hemodynamic parameters being measured with invasive monitoring, it is important to become familiar with cardiac concepts that can directly influence heart function. As discussed in the chapter on the cardiovascular system, CO is calculated by multiplying the stroke volume, or the amount of blood ejected by the heart with each beat, by the heart rate, which is the number of heart beats per minute. Based on this formula, a decrease in heart rate will lower the patient’s CO and an increase in heart rate will increase CO. However, it is important to recognize that although an increased heart rate can initially act as a compensatory mechanism to improve CO, eventually the heart will tire, resulting in a decreased CO.
In addition to heart rate, stroke volume also plays a significant role in the determination of CO and function. There are three main factors that influence stroke volume: preload, afterload, and contractility.
- The degree of stretch of the ventricle's cardiac muscles right before they contract is called preload. In other words, it is how much blood the ventricles can hold.
- The amount of resistance the ventricles must overcome to pump out blood with a contraction is called afterload. This resistance is influenced by several factors, including blood vessel tone and constriction, blood viscosity, and structural competency of the heart muscle.
- The strength of the contraction of the heart muscle itself is called contractility.
Changes to any one of these components can drastically affect the patient’s stroke volume and overall CO.
Medical Assessments and Therapies
With knowledge of the mechanisms that influence CO, critical care nurses can assess and monitor hemodynamic parameters at the bedside with use of arterial catheters and pulmonary artery catheters. An arterial catheter is a small, flexible catheter that is inserted into either the radial or femoral artery and connected to monitoring equipment to reflect continuous blood pressure measurements. Figure 35.3 shows the different parts of an arterial line.
A pulmonary artery catheter, also known as a Swan-Ganz catheter, is a type of central venous catheter that is surgically inserted into the pulmonary artery and used to measure various pressures within the heart (Ziccardi & Khalid, 2023). Figure 35.4 shows the different parts of a pulmonary artery catheter. Pulmonary artery catheters assist with monitoring many different internal heart pressures, as listed and described in Table 35.2.
| Hemodynamic Parameter | Description | Normal Range |
|---|---|---|
| Cardiac output (CO) | Amount of blood ejected from the ventricles each minute | 4–8 L/min |
| Cardiac index | CO value that has been adjusted and personalized on the basis of the patient’s body size and surface area | 2.5–4.0 L/min/m2 |
| Stroke volume | Amount of blood ejected by the ventricle with each heartbeat | 60–100 mL/beat |
| Right ventricular end-diastolic pressure | Reflects right ventricular preload | 0–8 mm Hg |
| Left ventricular end-diastolic pressure | Reflects left ventricular preload | 4–12 mm Hg |
| Right atrial pressure and central venous pressure | Interchangeable terms that reflect the pressure of the blood volume in the right side of the heart at the end of diastole | 2–6 mm Hg |
| Pulmonary artery pressure | Pressure within the pulmonary artery | 11–20 mm Hg at rest |
| Pulmonary artery occlusion (“wedge”) pressure | Reflects the pressure in the left atrium; determined by injecting air into the balloon port, causing an occlusion or “wedge” | 8–12 mm Hg |
| Systemic vascular resistance | Resistance that the left ventricle must overcome to pump blood to the body | 800–1200 dynes/sec/cm−5 |
In addition to hemodynamic monitoring, there are several other diagnostic tests and procedures used in critical care settings to evaluate the function of the cardiovascular system. A description of these can be found in Table 35.3.
| Diagnostic Test | Description | Clinical Significance |
|---|---|---|
| Chest radiography (X-ray) | Use of electromagnetic waves to produce images of the heart and surrounding structures | Used to evaluate the size and structure of the heart, heart positioning, abnormal fluid accumulation, and structural defects |
| 12-Lead electrocardiogram | Noninvasive use of sticky leads placed on the chest and connected to a monitor to determine heart rate and rhythm by measuring internal electrical activity | Used to diagnose or rule out cardiac dysrhythmias and myocardial infarction |
| Echocardiogram | Noninvasive use of ultrasound waves to visualize the internal and external structure of the heart | Used to diagnose valve disorders, congenital defects, and cardiac tumors and to calculate ejection fraction |
| Cardiac catheterization | Invasive procedure that involves insertion of a catheter through the radial or femoral artery and advancing it up to the heart | Used to identify and determine the severity of blockages within the coronary arteries as the cause of the cardiogenic shock |
Pharmacological Supports
Medications used in critical care settings for cardiovascular support are called vasoactive medications, meaning they exert their effects on blood vessels and have the potential to significantly alter hemodynamics. Most of these medications are given intravenously and may only be administered in the ICU or progressive care unit (a.k.a., “stepdown units”), where there are more resources available for frequent hemodynamic monitoring. Additionally, doses of many of these drugs must be titrated by the critical care nurse according to standing orders and specific parameters set by the health-care provider to achieve optimal hemodynamic effects. A description of some of the most common classes of cardiovascular medications are presented in Table 35.4.
| Medication Class | Examples (Example Brand Name) | Action | Side or Adverse Effects | Nursing Considerations |
|---|---|---|---|---|
| Beta-blockers |
|
Block beta-adrenergic receptors, resulting in decreased heart rate, blood pressure, and heart contractility |
|
|
| Calcium channel blockers |
|
Blocks flow of calcium into heart and blood vessels, resulting in muscle relaxation and a decreased workload on the heart |
|
|
| Inotropes |
|
Improves CO by increasing heart contractility |
|
|
| Nitrates |
|
Relaxation of smooth muscle in blood vessels, resulting in vasodilation and decreased workload of the heart |
|
|
| Vasopressors |
|
Vasoconstriction of blood vessels, resulting in an increased blood pressure |
|
|
Nonpharmacologic Interventions
In addition to pharmacologic treatments, there are nonpharmacologic interventions that can be implemented in critical care settings to provide cardiovascular support. Most of these interventions are invasive and require complex medical equipment at the bedside, which must be monitored closely by the critical care nurse.
To decrease afterload and improve perfusion of the coronary arteries during diastole, intra-aortic balloon pumps (IABPs) are used. These devices are often used after invasive cardiac surgeries, with severe heart failure exacerbations, or after large myocardial infarctions (Khan & Siddiqui, 2023). The procedure involves the insertion of an introducer sheath into the femoral artery. The IABP catheter is then inserted into the sheath and advanced until the balloon part of the catheter is in the aorta. The IABP is often referred to as a counter-pulsation device, meaning that it inflates when the heart is not contracting (during diastole) and deflates during contraction (systole) (Figure 35.5.) When the balloon inflates during diastole, it pushes blood into the coronary arteries, which improves perfusion to the heart muscle and decreases cardiac workload. When the balloon deflates during systole, it reduces afterload, making it easier for blood to be pumped out to the rest of the body. IABPs are highly invasive and require specialized training to operate. Because they are inserted into a large artery, it is imperative that the ICU nurse monitor the patient closely for signs of bleeding or neurovascular changes such as a diminished pedal pulse, which may indicate thrombosis.
Another invasive cardiovascular therapy that may occur in the ICU is extracorporeal membrane oxygenation (ECMO). This procedure involves the use of a machine that acts as an artificial heart and lungs for the patient when their organs are not functioning at optimal levels. Blood is pumped from the right side of the heart to the ECMO machine, where it is oxygenated and warmed, and then sent back to the body (Figure 35.6.) Because the blood bypasses the heart and lungs, it gives them time to rest, which is important for patients who have experienced severe trauma or disease to these organs (Mayo Clinic, n.d.). ECMO is highly invasive and requires a high level of nursing skill to monitor and operate the equipment. Complications with ECMO are common and include bleeding, clotting, infection, and limb ischemia. Treatment of a patient receiving ECMO is interdisciplinary, inclusive of perfusionists who assist in the maintenance of the machine and a cardiologist who evaluates the response to the therapy.
Link to Learning
Visit this overview of ECMO provided by Yale Medicine.
External pacing, also called transcutaneous pacing, is another cardiovascular intervention that is performed in the ICU. This process involves the placement of electrode pads on the patient’s chest to deliver shocks that keep the heart maintaining an adequate rate (Figure 35.7.) This procedure is performed when the patient is experiencing symptomatic bradycardia or some degree of heart block. This is only a temporary solution, however, and these patients will often need to be sent to the operating room quickly after initiation of the external pacing, to receive a permanent pacemaker.
Exemplar: Cardiogenic Shock
Cardiogenic shock is a life-threatening cardiac disorder that may be experienced by patients in the ICU. Most often, this condition occurs secondary to a large myocardial infarction (MI), or heart attack, but it can result as a secondary complication from many other disorders as well (National Heart, Lung, and Blood Institute. 2022).
Cardiogenic shock due to injury or death of the cardiac tissue causes the heart to stop pumping effectively. The inability of the heart to pump effectively results in severe hypotension and a lack of perfusion to all other body systems. This can lead to MODS.
When the heart is damaged, it loses some of its cardiac muscle strength and is unable to contract effectively. Without a strong heart contraction, less blood can be ejected, resulting in a decreased stroke volume and CO. The forward flow of blood backs up into the pulmonary system, resulting in fluid overload and hypoxia because the heart is no longer able to process the blood and pump it to other parts of the body. The heart will attempt to compensate for the decreased CO by increasing heart rate, but eventually the workload of the heart becomes too great and the body develops cardiogenic shock. Clinical manifestations of cardiogenic shock resemble those of left-sided heart failure, including
- crackles in the lungs
- diaphoresis
- hypotension
- S3 heart sound
- shortness of breath
- tachycardia
Treatment for cardiogenic shock focuses on determining and treating the underlying cause and decreasing the workload of the heart through both pharmacologic and nonpharmacologic interventions, some of which are discussed later in this section. Additionally, treatment involves providing supportive care to the rest of the body’s organs and tissues that are negatively affected by decreased perfusion.
Nursing Concepts and Care
Nursing care of the critically ill patient experiencing cardiovascular dysfunction is complex and requires optimal clinical judgment and critical thinking skills. The nurse must be prepared to quickly intervene based on subtle changes in the patient’s condition. These requirements are reflected within the Clinical Judgment Measurement Model, with each step of the model being explored further in the following sections.
Recognizing Cues and Analyzing Cues
First and foremost, critical care nurses must perform frequent assessments of the cardiovascular system. These assessments allow the nurse to detect subtle changes from baseline. Beyond physically assessing heart sounds and circulation (e.g., capillary refill, pulses), the nurse should closely monitor hemodynamic parameters such as CO and stroke volume and intervene as necessary on the basis of those findings.
Prioritizing Hypotheses, Generating Solutions, and Taking Action
Nursing care often involves administration of vasoactive medications that can significantly alter patient hemodynamics. Because of this, the nurse must have extensive knowledge of the mechanism of the medications and monitor and evaluate their effects closely. As with most medications administered in the ICU, frequent dose titrations, or adjustments, are based on the patient’s hemodynamics and the physician’s standing orders, requiring both careful assessment and attention to detail. Without proper attention to the effects of these medications, cardiovascular function may be greatly altered, resulting in systemic complications that could have otherwise been prevented. In addition to administering and titrating medications, the critical care nurse is responsible for maintaining invasive therapies such as IABPs and ECMO. These therapies present risks such as bleeding and thromboembolism, so the critical care nurse should be able to assess for these complications and intervene appropriately.
Read the Electronic Health Record
Caring for the Critically Ill Patient with Heart Failure
The nurse is caring for a patient admitted to the cardiac intensive care unit (CICU). Review the patient’s electronic health record (EHR) and answer the questions that follow.
Nurse’s note (0800):- Patient brought to CICU from emergency department [ED]. ED nurse reports that the patient is exhibiting signs of biventricular heart failure. Pulmonary artery catheter was placed in the ED. Patient has been connected to the bedside monitor and vital signs are currently stable. Will continue to monitor.
- BP [blood pressure]: 90/52 mm Hg
- Cardiac index [CI]: 2–3 L/min
- CVP [central venous pressure]: 7 mm Hg
- BP: 82/52 mm Hg
- CI: 1–1.5 L/min
- CVP: 10 mm Hg
- Normal saline @ 100 mL/h (Widiarti et al., 2024)
- Dobutamine 5 μg/kg/min IV continuous infusion (titrate to maintain systolic BP >100 mm Hg)