Monitoring

Monitoring

1. Standard monitors
   1. Continuous ECG display of both leads II and V₅ with ST segment trend analysis.
   2. Temperature monitoring includes that of the oral or nasopharynx (core temperature), 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. PA catheter provides helpful data in managing hemodynamics of patients with valvular and redo surgeries. 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 can help surgical and anesthetic decision-making. The Society of Cardiovascular Anesthesiologists/American Society of Echocardiography TEE guidelines recommend the use of intraoperative TEE in all open heart (eg, valvular procedure) and thoracic aortic surgical procedures and to be considered in coronary artery bypass grafting (CABG) surgery. TEE provides guidance during catheter-based intracardiac procedures (eg, transcatheter aortic valve replacement [TAVR] and MitraClips).
   1. The routine examination consists of 20 standard views. The probe is advanced into the esophagus (upper and midesophageal views) and then into the stomach for transgastric views.
   2. Application of intraoperative TEE includes confirmation of the placement of guidewire or cannula, assessment of global and regional ventricular function, chamber sizes, and valvular anatomy and function. TEE is very sensitive for detecting ischemia. It is also used to assess ventricular function, the presence of intracardiac air, and the presence of paravalvular leaks.
   3. Absolute contraindications to TEE:
      1. Esophageal stricture
      2. Tracheoesophageal fistula
      3. History of recent esophageal surgery and esophageal trauma.
      4. TEE must be used cautiously in patients with esophageal varices and altered anatomy (eg, 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 detailed images of valve and other structures.
4. Neurologic monitors such as transcranial Doppler, multichannel electroencephalography (EEG), and near-infrared spectroscopy may improve neurologic outcome by alerting the clinician of cerebral ischemia. Processed EEG (BIS or Sedline) monitor is a useful guide to predict the depth of anesthesia.