Intraoperative Monitoring, Echocardiography, and Hemodynamic Management
Monitoring
Standard monitoring includes ECG, pulse oximetry, capnography, temperature, and noninvasive blood pressure; cardiac surgery usually adds invasive arterial pressure and central venous access. Arterial lines provide beat-to-beat pressure and blood sampling, but accuracy depends on transducer level, damping, and waveform quality. Central venous pressure reflects right atrial pressure, not volume responsiveness; trends and waveform are more useful than a single number. Pulmonary artery catheters can measure CO, mixed venous saturation, and PA pressures, but interpretation requires attention to zeroing, wedge position, and respiratory variation. TEE is central for valve assessment, ventricular function, filling, and complications; know the standard views and contraindications.
Echocardiography and hemodynamics
Use TEE to answer focused questions: Is the LV full? Is contractility adequate? Is there a new regional wall motion abnormality? Is a valve stenotic, regurgitant, or prosthetic? Distinguish preload from filling pressure; a small LV with underfilling differs from a dilated, stiff LV. Dynamic indices such as pulse pressure variation and stroke volume variation predict fluid responsiveness only with controlled ventilation, sinus rhythm, adequate tidal volume, and no spontaneous effort. Do not use them in open chest, arrhythmia, or right heart failure without caution.
Traps
A common trap is treating a high CVP as proof of volume overload or a low CVP as proof of hypovolemia. Another is accepting a wedge pressure without confirming waveform and balloon position. TEE contraindications include esophageal pathology and unstable cervical spine in some positions; examine before inserting. Worked example: hypotension with clear lungs, a small LV on TEE, and pulse pressure variation of 18% during controlled ventilation suggests fluid responsiveness; give a small fluid bolus and reassess. Rule of thumb: a monitor answers a question only if the question and its limitations are defined first.