Central Venous Pressure (CVP)

Definition

Central Venous Pressure (CVP) is the pressure measured in the thoracic vena cava near the right atrium, reflecting:

• Right atrial pressure (RAP)
• Right ventricular preload
• The interaction between venous return and right heart function

Physiologically: CVP = back-pressure to venous return

Normal Values

Physiological Determinants of CVP

CVP is governed by Guyton’s venous return model:

1. Mean Systemic Filling Pressure (MSFP)

• Pressure generated by stressed venous volume
• Increased by:
• Fluid bolus
• Venoconstriction (noradrenaline)
• Decreased by:
• Venodilation (sepsis, anesthetics)

2. Intrathoracic Pressure

CVP should be measured at end-expiration

3. Venous Tone

• Venoconstriction → ↑ CVP
• Venodilation (sepsis, anesthesia) → ↓ CVP

Measurement of CVP

Catheter Sites

• Internal jugular vein (preferred)
• Subclavian vein
• Femoral vein (less reliable)

Zero Reference Level

• Phlebostatic axis:
• 4th intercostal space
• Mid-axillary line
• Level of right atrium

Technique

1. Patient supine (0–30°)
2. Transducer zeroed to atmospheric pressure
3. Measure at end-expiration
4. Avoid catheter tip abutting vessel wall

CVP Waveform Analysis

Normal CVP Waveform Components

Abnormal Waveforms 

Clinical Interpretation of CVP

Low CVP

• Hypovolemia
• Vasodilation (sepsis, anesthesia)
• Excessive diuresis

High CVP

CVP and Fluid Responsiveness

Key Exam Concept

CVP is NOT a reliable predictor of fluid responsiveness

• Static preload marker
• Poor correlation with stroke volume response
• Supported by:
• Surviving Sepsis Campaign
• Multiple meta-analyses

Dynamic Use of CVP

CVP in Specific ICU Conditions

1. Sepsis

• CVP may be low, normal, or high
• Elevated CVP associated with:
• AKI
• Hepatic congestion
• Increased mortality
• Targeting CVP is no longer recommended

2. ARDS

• PEEP increases CVP without increasing preload
• High CVP worsens pulmonary edema & RV strain

3. Cardiac Tamponade

• Elevated CVP
• Equalization of diastolic pressures
• Prominent x descent, absent y descent

4. Right Ventricular Failure

• CVP is a key congestion marker
• CVP >15 mmHg suggests venous congestion
• CVP/PCWP ratio helps differentiate RV vs LV failure

CVP vs Other Hemodynamic Variables

Complications of CVP Monitoring

• Infection
• Thrombosis
• Pneumothorax
• Air embolism
• Catheter malposition

Current Guideline Perspective

• Not a resuscitation target
• Useful for:
• Trend monitoring
• RV failure assessment
• Venous congestion evaluation
• Waveform diagnosis

Key Exam Pearls

• CVP reflects backward failure, not forward flow
• High CVP ≠ adequate preload
• Rising CVP with falling BP = danger sign
• Always interpret CVP with clinical context & dynamic indices

Suggested References

• Harrison’s Principles of Internal Medicine
• Irwin & Rippe’s Intensive Care Medicine
• Vincent JL – Textbook of Critical Care
• Surviving Sepsis Campaign Guidelines
• Guyton & Hall Physiology