Reference Guide
Hemodynamic Monitoring
Swan-Ganz catheter, arterial lines, CVP, cardiac output, and shock patterns
Reference Values
| Parameter | Normal Range |
|---|---|
| Right Atrial Pressure (RAP/CVP) | −1 to +8 mmHg |
| Right Ventricular Pressure | 15–28 / 0–8 mmHg |
| Pulmonary Artery Pressure | 15–28 / 5–16 mmHg; mean 10–22 mmHg |
| Pulmonary Capillary Wedge Pressure (PCWP) | 6–15 mmHg (mean) |
| Cardiac Output (CO) | 4.8–7.3 L/min |
| Cardiac Index (CI) | 2.8–4.2 L/min/m² |
| Systemic Vascular Resistance (SVR) | 700–1600 dyn·s·cm⁻⁵ |
| Pulmonary Vascular Resistance (PVR) | 0.25–2 Wood units (20–130 dyn·s·cm⁻⁵) |
| Mixed Venous O₂ Saturation (SvO₂) | 65–75% |
| Cardiac Power Output (CPO) | >0.6 W (low predicts MCS need) |
| PA Pulsatility Index (PAPi) | >1.0 (low suggests RV failure) |
Key Note
All pressures should be read at end-expiration, when intrathoracic pressure most closely approximates atmospheric pressure, regardless of ventilation mode.
The PAC provides direct measurement of right-sided pressures, PA pressures, and an estimate of left atrial pressure via the wedge, along with cardiac output by thermodilution. Despite debate (ESCAPE trial found no mortality benefit in routine use), contemporary reappraisal supports invasive hemodynamic profiling in cardiogenic shock and patients on mechanical circulatory support (MCS).
Clinical Use Pearls
- CPO = MAP × CO / 451; CPO <0.6 W predicts mortality and need for MCS escalation in cardiogenic shock
- PAPi = (PA systolic − PA diastolic) / RAP; PAPi <1.0 (especially <0.9 in acute MI) predicts RV failure and need for right-sided MCS
- Transpulmonary gradient (mean PAP − PCWP) >12 mmHg suggests pulmonary vascular disease
- Cardiac index = CO / BSA; thermodilution curves should be reproducible within ~10% across three injections
- Continuous CO (CCO) averages over 4–12 min; STAT CCO updates every 30–60 seconds
- Limitations: thermodilution unreliable with severe TR, intracardiac shunts, or arrhythmias
Setup & Zeroing
- Transducer leveling: Phlebostatic axis (4th intercostal space, midaxillary line)
- Re-zero whenever the system is opened to air or readings are questioned
- Tubing: Short (<122 cm), stiff, non-compliant; remove all air bubbles
- Pressure bag: Maintain ≥300 mmHg
Square Wave (Fast-Flush) Test
| Response | Oscillations | Cause | Clinical Effect |
|---|---|---|---|
| Optimally Damped | 1–2 | Properly set up system | Accurate readings |
| Underdamped | >2 | Air bubbles, long/compliant tubing, catheter whip | Falsely HIGH SBP, falsely LOW DBP |
| Overdamped | 0–1 (sluggish) | Clot, kink, large air bubble, loose connection | Falsely LOW SBP, falsely HIGH DBP; loss of dicrotic notch |
Troubleshooting Sequence
Check stopcocks → Check pressure bag (≥300 mmHg) → Flush line and tighten connections → Re-zero → Reposition catheter (especially radial site) → Consider replacement if persistently damped.
Normal Waveform Components
- a wave – Atrial contraction; corresponds to RV end-diastole. Best approximates true RV filling pressure
- c wave – Tricuspid valve closure/bulging into RA at onset of ventricular systole
- x descent – Atrial relaxation; blunting suggests RV dysfunction
- v wave – Passive atrial filling against a closed tricuspid valve
- y descent – Atrial emptying after tricuspid opening
Abnormal Findings
| Abnormality | Interpretation |
|---|---|
| Loss of a waves | Atrial fibrillation |
| Flutter a waves | Atrial flutter |
| Cannon a waves | AV dissociation, junctional/ventricular rhythm, complete heart block |
| Giant v waves | Tricuspid regurgitation; acute MR reflected at PCWP |
| Blunted x descent | RV dysfunction |
| M or W pattern (steep x and y) | Constrictive pericarditis |
| Blunted y descent | Cardiac tamponade |
| Arterial-appearing waveform | Catheter migration into RV — reposition immediately |
Methods Comparison
| Method | Principle | Strengths | Limitations |
|---|---|---|---|
| PAC Thermodilution (bolus) | Cold saline RA → PA thermistor | Gold standard; well-validated | Operator-dependent; inaccurate with TR, shunts |
| Continuous CO (PAC) | Thermal filament algorithm | Trending without injections | 4–12 min lag; STAT 30–60 s |
| Transpulmonary (PiCCO) | Central venous → arterial thermistor | Provides EVLW, GEDV | Requires femoral arterial line |
| Pulse Contour (calibrated) | Arterial waveform + calibration | Continuous; less invasive | Drifts; needs recalibration |
| Pulse Contour (uncalibrated) | Waveform algorithm only | Minimally invasive | Poor in low EF, high-dose vasopressors |
| Fick (calculated) | VO₂ / (CaO₂ − CvO₂) × 10 | Useful in shunts, severe TR | Requires assumed VO₂ or metabolic cart |
| Echo (LVOT VTI) | LVOT area × VTI × HR | Noninvasive | Operator-dependent |
Hemodynamic Profiles
| Shock State | CI | SVR | CVP | PCWP | SvO₂ |
|---|---|---|---|---|---|
| Hypovolemic | ↓ | ↑ | ↓ | ↓ | ↓ |
| Cardiogenic (LV) | ↓ | ↑ | ↑ | ↑ | ↓ |
| Cardiogenic (RV) | ↓ | ↑ | ↑↑ | ↓ or N | ↓ |
| Tamponade | ↓ | ↑ | ↑ (equalized) | ↑ (equalized) | ↓ |
| Massive PE | ↓ | ↑ | ↑ | ↓ | ↓ |
| Distributive/Septic | ↑ or N | ↓↓ | ↓ or N | ↓ or N | ↑ or N |
| Mixed (cardiogenic + vasoplegic) | ↓ | ↓ | ↑ | ↑ | ↓ |
RV Failure Pattern
- CVP/RAP >15 mmHg, CVP/PCWP ratio >0.8
- PAPi <1.0, low PA pulse pressure, blunted x descent
- Dilated/hypokinetic RV on echo, septal shift
- Avoid volume loading once CVP is high — worsens RV dilation and ventricular interdependence
- Optimize rhythm (sinus, AV synchrony), reduce RV afterload (treat hypoxia/hypercapnia/acidosis)
- Add inotropy (milrinone, dobutamine, epinephrine), inhaled pulmonary vasodilators
- Consider RV MCS (RVAD, Impella RP, VA-ECMO) if refractory
Clinical Pearls
- Read all hemodynamic pressures at end-expiration
- A normal CVP does not exclude RV failure — look at PAPi, x descent, RV size, CVP/PCWP ratio
- Cannon a waves on CVP in a bradycardic patient → AV dissociation — check pacer and rhythm
- New giant v wave on PCWP → acute mitral regurgitation (e.g., papillary muscle rupture)
- Falling SvO₂ (<60%) is an early sign of inadequate O₂ delivery — evaluate CO, Hgb, SaO₂, VO₂
- Sudden cessation of chest tube output + rising filling pressures + narrowing pulse pressure = tamponade until proven otherwise
- Hypotension after intubation → loss of sympathetic tone + decreased preload from PPV — treat with fluid, vasopressor, minimize PEEP
- In RV failure, volume is the enemy — favor diuresis, inotropy, and afterload reduction
- Always confirm pacer capture and sensing at start of every shift and before transport
S.K.
The World-Class Cardiac Intensivist
This content is for educational reference only. Always follow institutional protocols and exercise clinical judgment.