Hemodynamic Monitoring: MAP and Pulse Pressure

• Hemodynamic monitoring measures pressure, flow, and oxygenation within the cardiovascular system.
• It assesses heart function, fluid balance, and the impact of fluids/drugs on cardiac output (CO).
• Hemodynamic parameters are obtained through both invasive and noninvasive methods.
• These parameters include arterial pressures, central venous pressure (CVP), pulmonary artery wedge pressure (PAWP), CO/CI, SV/SVI, SVV, SaO2, and SvO2.

Mean Arterial Pressure (MAP)

• MAP represents the average pressure within the arterial system.
• The formula is MAP = (SBP + 2DBP) / 3.
• The normal range for MAP is 70-100 mm Hg.
• Critical care monitors calculate and display MAP.

Pulse Pressure

• Pulse pressure is the difference between systolic and diastolic pressures.
• It's usually about 1/3 of the systolic pressure (e.g., 120/80 BP has a pulse pressure of 40).
• Increased pulse pressure can be due to exercise, atherosclerosis, or neurologic issues.
• Decreased pulse pressure may occur with heart failure or hypovolemia.

Arterial Pressure Lines

• Arterial lines are an invasive method for continuous blood pressure monitoring.
• A small catheter is inserted into an artery (usually radial, but brachial or femoral can be used).
• The catheter connects to pressurized 0.9% sodium chloride and a transducer, displaying a waveform and constant BP readings.
• Arterial lines allow the healthcare provider to track trends and sudden BP changes.
• They can also be utilized for frequent blood draws.
• The transducer must be at the level of the midaxillary line (right atrium) for accurate readings.
• Transducer too low leads to falsely high readings; too high leads to falsely low readings.

Central Venous Pressure (CVP)

• CVP is an invasive hemodynamic monitoring technique.
• It estimates right atrial pressure and preload and measures pressure in the vena cava.
• CVP may be used to guide fluid resuscitation in shock, though its accuracy for fluid responsiveness is debated.
• The expected reference range for CVP is 8-12 mm Hg.
• Monitoring requires a central venous access device (CVAD) in the internal jugular or subclavian vein, advanced into the superior vena cava.
• Pressure is measured via a transducer at the level of the tricuspid valve.
• Decreased CVP can indicate hypovolemia, blood loss (over 10%), vena cava dilation, or decreased intrathoracic pressure.
• Elevated CVP can indicate decreased cardiac contractility, dysrhythmias, valve dysfunction, or heart failure.
• Other causes of increased CVP include excessive PEEP, fluid retention, ventilation/perfusion ratio alterations, increased intra-abdominal/pericardial pressures, tension pneumothorax, pericardial tamponade, or right ventricular dysfunction.
• Nurses should assess trends in the client's data, and ensure transducers are level with the phlebostatic axis and zeroed.

Pulmonary Artery Catheterization

• Used to evaluate shock etiology via mixed venous oxygen saturation.
• Assesses volume status in severe shock.
• Evaluates pericardial illnesses.
• Pulmonary artery (PA) catheters assess right-sided filling pressures, cardiac valves, intracardiac shunts, CO, and vascular resistance.
• A balloon can be inflated to measure pulmonary capillary wedge pressure, estimating left-sided filling pressure.
• Involves inserting a catheter through a vein (brachial, antecubital, jugular, or femoral) into the right heart and pulmonary artery.
• Pressure waveforms are sent to a monitor.
• Can be performed under fluoroscopy or at the bedside using echocardiography/ultrasound.
• Preparation involves strict sterile techniques.
• Potential complications include infection, hemothorax/pneumothorax, air embolism, arrhythmias, vessel rupture, pulmonary infarction, or thromboembolism.
• To obtain PCWP, a catheter is advanced into smaller pulmonary artery branches to briefly block blood flow.
• The reading is a pressure in the left atrium during diastole.

Infection Prevention for Invasive Lines

• Use all-inclusive kits.
• Practice meticulous hand hygiene.
• Use chlorhexidine for dressing changes.
• Change transparent dressings every 7 days.
• Change gauze dressings every 48 hours or when soiled.
• Access lines as little as possible.
• Scrub hubs with disinfectant for 30 seconds before access.
• Change central line tubing up to every 96 hours with strict asepsis.

Continuous Renal Replacement Therapy (CRRT)

• CRRT is a blood purification therapy used in acute kidney injury, often due to trauma or sepsis.
• Decreased perfusion leads to kidney dysfunction, causing toxin and fluid accumulation.
• Systemic alterations include acid-base imbalances, fluid overload, and encephalopathy.
• The therapy filters the blood, removing fluid and toxins, then returns the clean blood.
• Complications during the 24-hour therapy can include catheter-related issues, hemorrhage, infection, pneumothorax, and air embolism.
• CRRT is a gradual, continuous process better tolerated than intermittent hemodialysis.
• Types of CRRT: continuous venovenous hemofiltration (CVVH), continuous venovenous hemodiafiltration (CVVHDF), slow continuous ultrafiltration (SCUF), and continuous venovenous hemodialysis (CVVHD).

Intra-Aortic Balloon Pump (IABP)

• IABP is temporary support for cardiogenic shock, increasing myocardial oxygen and decreasing demand.
• It decreases afterload and supports diastolic aortic pressure, increasing perfusion and coronary blood flow.
• The balloon inflates during diastole, pushing blood into circulation, and deflates before systole.
• This improves diastolic pressure and decreases systolic aortic pressure by decreasing afterload, left ventricle wall stress, and myocardial oxygen demand.
• Cardiac output improves by increasing stroke volume, especially in clients with decreased left ventricular function.
• The nurse must obtain informed consent prior to the procedure.
• A balloon is inserted into the femoral artery and placed with the tip distal to the left subclavian artery and the proximal portion above the renal arteries.
• Placement is confirmed by chest x-ray or fluoroscopy.
• A transducer monitors intra-aortic pressure.
• Nurses caring for IABP clients need specialized training and hemodynamic monitoring skills.
• Clients require bedrest to avoid balloon displacement.
• Monitor peripheral pulses distal to the insertion site.
• Balloon migration can lead to complications like stroke or decreased blood supply to the left arm.
• Monitor for infection, thrombosis, or bleeding.
• Daily chest x-rays confirm balloon position.
• Unstable hemodynamics require urgent troubleshooting of the device's function.

Overview of hemodynamic monitoring, which assesses cardiovascular function via pressure, flow, and oxygenation measurements. Covers Mean Arterial Pressure (MAP) calculation and normal ranges. Explains Pulse Pressure, its calculation, and factors causing variations.