Hemodynamic Monitoring: A-line, CVP, PAC, TEE
Cardiovascular Anesthesia · 10 min read
Five questions to ask of every hemodynamic monitor: What does it actually measure? What can confound it? What decision does it inform? What does the literature say about outcome impact? When is the next monitor justified? This lecture works through the four major invasive options.
Arterial line — beat-to-beat truth
Indications: anticipated significant hemodynamic instability, anticipated frequent ABGs, vasoactive infusions, controlled hypotension, beach-chair (zero at TRAGUS), patients where NIBP cycle (every 3-5 min) is too slow. Sites: radial (default — Allen test), femoral (resuscitation, cardiac), brachial (avoid if possible — single artery to forearm), pedal/posterior tibial. Square-wave test confirms damping (1-2 oscillations = optimal; over-damped = clot/kink/air; under-damped = stiff tubing/resonance). MAP is the most reliable number — trust MAP over systolic when waveform is questionable.
MAP calculator →Central venous catheter + CVP
Indications: vasopressor infusion, multiple drug infusions, no peripheral access, central oxygen saturation (ScvO₂) monitoring, total parenteral nutrition. Sites: right IJ (default, ultrasound-guided), subclavian (lower infection risk, higher pneumothorax risk), femoral (highest infection risk, fast access in code). CVP NUMBERS: a single CVP value is poor predictor of fluid responsiveness (Marik review 2008); CVP TRENDS during fluid challenge are more useful. CVP ≠ left-sided filling in independent RV/LV failure. Use CVP to identify problems (pericardial tamponade — equalization), not to direct routine fluid therapy.
Pulmonary artery catheter (Swan)
PAC fell out of routine use in the 2000s after multiple negative trials (PAC-Man Lancet 2005; ESCAPE JAMA 2005 in CHF — no mortality benefit). Modern use: pulmonary hypertension diagnosis + management, severe RV failure, complex cardiac surgery, mixed venous saturation in shock states. Direct measurements: CVP, RV pressure, PA pressure (systolic + diastolic + mean), PCWP/PAWP. Derived: cardiac output (thermodilution), SVR, PVR, mixed venous saturation. Wedge pressure approximates left atrial pressure (and LVEDP) only in West zone 3 + normal mitral valve. PAC is a tool for cardiac anesthesia teams + ICU, not routine OR.
Transesophageal echocardiography
TEE is the most informative single hemodynamic monitor. Direct visualization of: LV/RV size + function, valves (regurgitation/stenosis severity), pericardial effusion, regional wall motion abnormalities (early MI detection), volume status (LVEDA), aortic dissection, intracardiac air/clot. INDICATIONS — Class I: cardiac surgery (CABG, valve), suspected aortic dissection, persistent unexplained instability. Class II: high-risk non-cardiac surgery, suspected PE, hemodynamic monitoring when other monitors insufficient. CONTRAINDICATIONS: esophageal stricture/perforation/diverticulum, recent UGI surgery, active UGI bleed. Requires 6-month formal training + ongoing case volume per ASE/SCA standards.
Standard TEE views →Pulse contour + minimally invasive cardiac output
FloTrac / EV1000 / LiDCO / PiCCO: derive stroke volume + cardiac output from arterial waveform. Advantages: no PA catheter, faster set-up, suitable for OR + ICU. Limitations: less accurate in arrhythmias, after vasodilators (rapid SVR changes), after large bleeds (auto-calibration issues). PROVIDES: SV, CO, SVV (stroke volume variation), PPV (pulse pressure variation). SVV/PPV >12-13% predicts fluid responsiveness in mechanically ventilated, sinus rhythm, VT ≥8 mL/kg, no spontaneous effort patient. Good for goal-directed fluid therapy in moderate-risk surgery.
Echo first — TTE/POCUS
Point-of-care ultrasound (POCUS) in anesthesia: Focused TTE/POCUS in PACU or pre-op identifies new cardiac dysfunction, pericardial effusion, IVC variability for fluid status, lung B-lines for pulmonary edema. Five views (parasternal long + short, apical four-chamber, subcostal, IVC) give most information. Increasingly part of CRNA + anesthesiologist core skill. Lower-stakes, no esophagus, no contrast — ideal as first-line evaluation tool.
Choosing — escalation principle
Match monitor invasiveness to expected case difficulty + patient risk. Healthy ASA I-II elective: NIBP + ECG + SpO₂ + EtCO₂ sufficient. ASA III with cardiac history: add A-line. Vasopressor needs or large fluid shifts: add CVC. Cardiac surgery, severe pulmonary HTN, RV failure: add PAC ± TEE. Suspected dissection, unexplained instability: TEE. Recognize indication CREEP: invasive monitor selected for one reason but kept in for the entire case → infection/complication risk; remove when no longer needed. Document indication + duration.
References
- · Miller's Anesthesia 9e Ch 47 (Cardiovascular Monitoring)
- · Marik Chest 2008 (CVP review — limitations)
- · PAC-Man Lancet 2005 (PA catheter trial)
- · ASE/SCA TEE Guidelines 2020
- · Hadian + Pinsky Crit Care 2007 (Functional hemodynamic monitoring)