【正文】 ring total intravenous anesthetic. ? d. Closedloop anesthesia, in which BIS directly guides administration of the hypnotic agent. This is not available in the United States at this time because of its investigational nature. A. Bispectral index (BIS) ? 3. BIS interpretation ? a. Recall of words or pictures is depressed at BIS values of 70 to 75. A BIS of 40 to 60 correlates with general anesthesia. ? b. Increasing concentrations of hypnotic agents predictably lower BIS. ? c. BIS is not affected by opioids, so the target BIS needs to be selected based on anesthetic technique. Thus, in the absence of opioids or analgesics, BIS should be 25 to 35。 with the use of opioid or analgesic supplementation, BIS can be 45 to 60. A. Bispectral index (BIS) ? 4. Complications. BIS may be inaccurate because of artifacts from different sources. ? a. Excessive muscle activity may elevate BIS. ? b. Seizure and “abnormal brain”rarely result in erroneous BIS values due to atypical EEG patterns or anatomy. ? c. Specific hypnotic agents have different effects on BIS. ? d. External electrical or mechanical interference may make BIS unreliable. ? 5. Materials. B. Other methods of awareness monitoring ? B. Other methods of awareness monitoring are entropy monitoring, using a DatexOhmeda spectral entropy algorithm, and midlatency auditory evoked potentials, both of which correlate well with anesthetic agent effect on awareness. V. Temperature monitoring ? A. Mechanism. ? B. Indications ? 1. Need to control temperature during induced hypothermia and rewarming (., during cardiopulmonary bypass or vascular neurosurgery). ? 2. Infants and small children. ? 3. Adults subjected to large evaporative losses or low ambient temperatures are prone to hypothermia. ? 4. Febrile patients. ? 5. Patients with autonomic dysfunction. ? 6. Malignant hyperthermia. V. Temperature monitoring ? C. Monitoring sites ? 1. Skin temperature, as measured on the forehead, is normally 3176。 F to 4176。 F below core temperature. ? 2． The axilla is a mon site and is usually 1176。 F below body temperature. ? 3． Tympanic membrane temperature correlates well with core temperature. V. Temperature monitoring ? 4． Rectal temperature changes lag behind those of core body temperature. ? 5. Nasopharyngeal temperature, measured at the posterior nasopharynx, reflects the brain temperature. ? 6. Esophageal temperature monitoring reflects the core temperature well. ? 7. Blood temperature measurements may be obtained with the thermistor of a PAC. ? VI. Neuromuscular blockade monitoring ? Figure . Percutaneous radial artery cannulation. A: Direct threading method. BD: Transfixing method. Positioning of the hand and forearm is the same for both methods. ? Figure . A normal central venous pressure tracing is shown in the bottom half of the figure with its corresponding electrocardiogram in the top half. Waves a, c, and v on the venous pressure tracing are labeled. The x descent occurs between waves c and v。 the y descent occurs after the v wave. (From Kaplan JA. Cardiac anesthesia, 2nd ed. Philadelphia: WB Saunders, 1987:186, with permission.) ? Figure . Effect of positive endexpiratory pressure (PEEP) on the venous return/cardiac output curves. PEEP has the effect of shifting the Starling curve to the right by a degree equal to the transmitted extracardiac pressure. At high levels of PEEP (15 cm H2O), the curve can be depressed secondary to increased right ventricular afterload. The central venous pressure measured is consequently higher. MSP, mean systemic pressure. Figure . Cannulation of the right internal jugular vein (Seldinger technique). See text for details. ? Figure . Left ventricular pressureolume relationships. (A) The cardiac cycle (ABCDA) is limited by the endsystolic pressureolume relationship (describing the contractility) and the enddiastolic pressureolume relationship. The pulmonary artery occlusion pressure (PAOP) approximates the left ventricular enddiastolic pressure. An increase in PAOP may be ascribed to decreased diastolic pliance (B), an increase in left ventricular enddiastolic volume (LVEDV) (C), or a bination of both. An increase in LVEDV often results from decreased contractility in the setting of a properly performing right ventricle (C). SBP, systolic blood pressure。 DBP, diastolic blood pressure. ? Figure . Characteristic pressure waves seen during insertion of a pulmonary artery catheter. CVP, central venous pressure。 IJ, internal jugular。 RA, right atrium。 RV, right ventricle。 PA, pulmonary artery。 PCW, pulmonary capillary wedge. Figure . A: Normal capnograph. I, dead space expiration。 II, mixed dead space and alveolar gas expiration。 III, alveolar gas expiration and plateau。 0, inspiration. Phase IV is an upswing that occurs at the end of phase III. B: Capnographs that may be seen in practice. 1, rapidly extinguishing uncharacteristic waveform, patible with esophageal intubation。 2, regular dips in endexpiratory plateau, seen in underventilated lungs or in patients recovering from neuromuscular blockade。 3, upward shift in baseline and plateau, seen with rebreathing of carbon dioxide, miscalibration, and so forth。 4, restrictive pulmonary disease。 5, obstructive pulmonary disease。 6, cardiogenic oscillations.