Chapter 6

• During catheterization of the internal jugular vein the possibility of placement of a vein dilator or central venous catheter into the carotid artery can be decreased by transducing the intravascular pressure waveform or by comparing the blood’s color or Pao2 with an arterial sample.
• The central venous pressure (CVP) catheter’s tip should not be allowed to migrate into the heart chambers.
• Relative contraindications to pulmonary artery catheterization include complete left bundle branch block (because of the risk of complete heart block), Wolff–Parkinson–White syndrome, and Ebstein’s malformation (because of possible tachyarrhythmias).
• Pulmonary artery pressure should be continuously monitored to detect an overwedged position indicative of catheter migration.
• Accurate measurements of cardiac output depend on rapid and smooth injection, precisely known injectant temperature and volume, correct entry of the calibration factors for the specific type of pulmonary artery catheter into the cardiac output computer, and avoidance of measurements during electrocautery.
• Capnography rapidly and reliably indicates esophageal intubation—a common cause of anesthetic catastrophe—but does not detect bronchial intubation.
• The electroencephalographic (EEG) changes that accompany ischemia, such as high-frequency activity, can be mimicked by hypothermia, anesthetic agents, electrolyte disturbances, and marked hypocapnia. Detection of changes in the EEG in an anesthetized patient should lead to an immediate review of possible causes of cerebral ischemia before irreversible brain damage has a chance to occur.
• Because hypothermia reduces metabolic oxygen requirements, it has proved to be protective during times of cerebral or cardiac ischemia.
• Redistribution of heat from warm central compartments (eg, abdomen, thorax) to cooler peripheral tissues (eg, arms, legs) from anesthetic-induced vasodilation explains most of the initial decrease in temperature, with actual heat loss being a minor contributor.
• During general anesthesia, however, the body cannot compensate for hypothermia because anesthetics inhibit central thermoregulation by interfering with hypothalamic function.

One of the primary responsibilities of an anesthesiologist is to act as a guardian of the anesthetized patient during surgery. In fact, “vigilance” is the motto of the American Society of Anesthesiologists (ASA). Because monitoring is helpful in maintaining effective vigilance, standards for intraoperative monitoring have been adopted by the ASA (the box on Standards for Basic Anesthetic Monitoring delineates minimum standards). Optimal vigilance requires an understanding of the technology of sophisticated monitoring equipment—including cost–benefit considerations. This chapter reviews the indications, contraindications, techniques and devices and associated complications, and other clinical considerations for the most important and widely used anesthetic monitors.

(Approved by the ASA House of Delegates on October 21, 1986 and last affirmed on October 15, 2003)

These standards apply to all anesthesia care although, in emergency circumstances, appropriate life support measures take precedence. These standards may be exceeded at any time based on the judgment of the responsible anesthesiologist. They are intended to encourage quality patient care, but observing them cannot guarantee any specific patient outcome. They are subject to revision from time to time, as warranted by the evolution of technology and practice. They apply to all general ...

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