Central Venous Catheterization

• Invasive Pressure Monitoring involves the use of central venous and pulmonary artery catheters.

Central Venous Catheterization

• Central venous catheterization, also known as a central line, central venous line, or central venous access catheter, involves inserting a catheter into a large vein.
• This procedure is indicated in the following cases:
  • Volume resuscitation
  • Emergent venous access
  • Nutritional support
  • Administration of inotropes
  • Hemodialysis
  • Central Venous Pressure (CVP) monitoring
• CVP catheterization is indicated for assessing circulating blood volume, filling pressures of the heart, and right ventricular function.
• Patients undergoing major surgery or trauma, and those with pulmonary edema, often require CVP monitoring.
• Common insertion sites include:
  • Subclavian vein
  • Internal jugular vein
  • Femoral vein
• Venous pressure is the average blood pressure in the venous compartment.
• Central venous pressure, often referred to as "filling pressure," measures the pressure of blood returning to or filling the right atrium.
• Blood reaches the right atrium via the Superior/Inferior Vena Cava.
• Used to estimate preload and right atrial pressure, making it useful in assessing hemodynamic status in critically ill patients.
• It assesses fluid balance, blood circulation, cardiac function, and overall circulatory failure.

CVP Waveforms

• Factors increasing CVP include:
  • Hypervolemia
  • Pleural effusion
  • Tension pneumothorax
  • Cardiac tamponade
  • Congestive heart failure
  • Mechanical ventilation with positive end-expiratory pressure
  • Valvular heart disease
• Factors decreasing CVP include:
  • Hypovolemia
  • Distributive shock
• Atrial fibrillation results in the absence of effective Right Atrium (RA) contractions.
• Cannon A waves occur when the right atrium and right ventricle contract simultaneously, commonly due to junctional rhythm, ventricular pacing, ventricular tachycardia, or complete heart block.
• Prominent A waves are associated with tricuspid stenosis, increased resistance of blood flow from the RA to the Right Ventricle (RV), slow and delayed atrial emptying, and attenuated Y-descent.
• Prominent V waves are associated with tricuspid regurgitation and backflow of blood from the RV to the RA.
• Systemic Vascular Resistance (SVR) is the resistance in the circulatory system used to create blood pressure.
• SVR = ((MAP – CVP) / CO) × 80
  • MAP = (SBP + 2 × DBP)/3, SVR is 320 when MAP is 50 mmHg, CVP is 10 mmHg, and CO is 10.
• Normal SVR ranges from 900-1200 dynes.sec.cm-5 or 11-15 Woods Units.
• SVR increases with sympathetic stimulation (pain, agitation, epinephrine, dopamine, norepinephrine, ketamine), negative intrathoracic pressure, and hypothermia.
• SVR decreases with adequate sedation, analgesia, vasodilators (milrinone, dobutamine, nitroprusside, ACE inhibitors), positive pressure ventilation, fever, and sepsis

Pulmonary Artery Catheterization

• Pulmonary artery catheterization is done using a Swan-Ganz catheter.
• The Swan-Ganz catheter is a soft catheter with an expandable balloon tip, used to measure blood pressure in the pulmonary artery.
• It is a diagnostic procedure where a small catheter is threaded through a vein in the arm, thigh, chest, or neck passing through the right side of the heart.
• It allows assessment of:
  • Left ventricular filling pressure
  • Pulmonary vascular resistance
  • Arteriovenous oxygen difference
  • Mixed venous oxygen levels
• It measures:
  • Pulmonary artery pressure
  • Right atrium pressure
  • Right ventricle pressure
  • Cardiac output (CO)
  • Indirect measurement of the pressure in the left atrium of the heart
• Indications for PA Catheterization:
  • Evaluation or diagnosis of pulmonary hypertension
  • Distinguishing etiology of shock based on mixed venous oxygen saturation (SvO2) measurement such as in septic or cardiogenic shock.
  • Assessment of volume status in severe shock
  • Evaluation of pericardial illnesses such as cardiac tamponade or constrictive pericarditis
  • Assessment of right-sided valvular disease, congenital heart disease, cardiac shunts when surgical repair is planned.
• Insertion sites include:
  • Subclavian vein
  • Internal jugular vein
  • Femoral vein
• Pulmonary Artery Catheter Lumens:
  • Red: Pulmonary Artery (balloon/PAWP)
  • Yellow: Pulmonary Artery (PAP/SvO2)
  • Blue: Right Atrium (CVP)
  • White: Right Atrium (meds)

Hemodynamic Values

• Central Venous Pressure: The normal CVP waveform includes a, c, v, x, and y waves.
• Right Ventricular Pressure: An RV waveform is obtained.
• Pulmonary Artery Pressure: An arterial waveform including systolic pressure, reflected pressure wave, inflection point, systolic pressure wave, and diastolic pressure is obtained along wth inflection time.
• Typical values for pulmonary artery pressure are:
  • Systolic: 25 mmHg
  • Mean: 16 mmHg
  • Diastolic: 10 mmHg
• Pulmonary Capillary Wedge Pressure: This is used to assess left ventricular filling, represent left atrial pressure, and assess mitral valve function.
• RA/CVP (0-5) has a, c, v, x, and y waves
• RV (15-25/0-8) is a rapid, positive spike with no wave components

Pulmonary Artery Pressures

• PA systolic pressure should be in the 20-30 mm Hg range.
  • It increases with high pulmonary vascular resistance.
  • Decreases with poor right heart function and pulmonary vasodilation.
• PA diastolic pressure should be in the 8-15 mm Hg range.
  • Normally reflects left heart filling pressures.
  • It does not reflect left heart filling pressures when pulmonary vascular resistance elevated.
• Increased PAP can be caused by:
  • Pulmonary Arterial Hypertension
  • Left heart failure/mitral valve disease
  • Lung disease/hypoxemia (emphysema/ILD)
• Decreased PAP can be caused by:
  • Hypovolemia
  • Pulmonary vasodilators
  • Right Heart Failure
  • Obstruction like Pulmonary Embolism
• Pulmonary Capillary Wedge Pressure ranges from 4 to 12 mm Hg.
  • It is must be interpreted in light of the patient's medical history (history of MI will cause a stiff left ventricle and lead to higher pressures)
  • It elevates with left heart failure or mitral stenosis.
  • It decreases with hypovolemia.
• Causes of increased or decreased PAWP pressures:
  • Decreased PAWP: Hypovolemia
  • Increased PAWP: Cardiac tamponade, constrictive pericarditis, hypervolemia, Mitral regurgitation or stenosis
• Normal pulmonary vascular resistance (PVR) is less than 250 dynes/sec/cm5 or 2 Wood units.

Cardiac Output

• CO can be determined according to Fick's Estimated Method
• Under normal conditions, the cardiac output is directly related to oxygen consumption.
• If the cardiac output fails to keep up with the oxygen consumption needs, then C(a-v)O2 increases
• Normal value is between 4-8 L/min.
• The formula for finding CO = 130 x BSA/CaO2-CvO2
  • 130: Estimated oxygen consumption rate of an adult in mL/min/m²
  • BSA: Body surface area in m²
• Arterial Oxygen Content (CaO2) = (0.003×PaO2)+(1.34×HbxSaO₂)
  • CaO2 = Total O2 content (ml/dl)
  • PaO2 = Partial pressure of O2 in the blood
  • Hb = Hb content (in g/dl)
  • SaO2 = Hb saturation with O2 (as a decimal)