Monitoring

Monitoring

1. Standard monitors (see Chapter 10).
   1. Continuous ECG display of both leads II and V₅ with ST segment trend analysis
   2. Temperature monitoring includes that of the nasopharynx (reflective of the core), the blood temperature (measured from pulmonary artery [PA] catheter), and bladder or rectal temperature, which represents the average body temperature.
2. Central venous and PA pressures
   1. Patients with normal ventricular function can be effectively managed with either central venous pressure (CVP) monitoring with or without transesophageal echocardiography (TEE) or a PA catheter.
   2. Pacing PA catheters provide pacing capability. They can be used to maintain a suitably high heart rate in patients with regurgitant valvular lesions (AI and MR) management of a variety of valvular lesions (AI and MR) and intraoperative conduction disorders. They can also be used during procedures in patients with prior sternotomies during which rapid access for epicardial pacing may not be possible. They are also used for rapid ventricular pacing or backup pacing for transcatheter aortic valve replacement (TAVR). Mixed venous oxygen saturation (SmvO₂) monitoring is available continuously with PA catheters specially equipped with a fiberoptic-linked oximeter. A decrease in SmvO₂ is the result of decreased cardiac output, decreased hemoglobin, increased oxygen consumption, or decreased SaO₂.
3. Intraoperative TEE is a useful tool to provide real-time information on cardiac anatomy and functional status, which can inform surgical and anesthetic decision making. The Society of Cardiovascular Anesthesiologists/American Society of Echocardiography TEE guidelines recommend the use of intraoperative in all open heart (e.g., valvular procedure) and thoracic aortic surgical procedures and to be considered in coronary artery bypass grafting (CABG) surgery. TEE may also be used to guide management during catheter-based intracardiac procedures (e.g., TAVR and MitraClips).
   1. The routine examination consists of 20 standard views. The probe is advanced into the esophagus (upper and mid-esophageal views) and then into the stomach for transgastric views.
   2. Application of intraoperative TEE includes assessment of global and regional LV and RV function, chamber sizes and valvular anatomy and function. TEE is very sensitive for detecting ischemia. Upon termination of CPB, it can be used to assess ventricular function, the presence of intracardiac air, and the presence of paravalvular leaks.
   3. Absolute contraindications to TEE are the presence of an esophageal stricture, tracheoesophageal fistula, and a history of esophageal surgery and esophageal trauma. TEE must be used cautiously in patients with esophageal varices and altered anatomy (e.g., from gastric bypass surgery) and in those who have had radiation therapy to the neck and mediastinum. The incidence of severe complications such as esophageal perforation is on the order of 0.1%.
   4. 3-Dimensional TEE can provide visualization of complex valvular features.
4. Neurologic monitors such as transcranial Doppler, multichannel electroencephalography, and near-infrared spectroscopy (NIRS) may improve neurologic outcome by alerting the clinician to perfusion imbalances during CPB. BIS monitor is a useful guide to titrate anesthetic agents for cardiac surgical patients being considered for early extubation.