KEY POINTS

1. Although a stethoscope should be present in every anesthetizing location, continuous stethoscopy is an insensitive method for early detection of untoward hemodynamic events.
2. Most automated noninvasive blood pressure measuring devices use an oscillometric measurement technique and rarely cause complications. Caution should be exercised in patients who cannot complain of arm pain, those with irregular rhythms that force repeated cuff inflation, and individuals receiving anticoagulant therapy.
3. Direct arterial pressure monitoring should be widely used in operative patients with severe cardiovascular diseases or those undergoing major surgical procedures that involve significant blood loss or fluid shifts.
4. The Allen test for palmar arch collateral arterial flow is not a reliable method to predict complications from radial artery cannulation. Despite the absence of anatomic collateral flow at the elbow, brachial artery catheterization for perioperative blood pressure monitoring is a safe alternative to radial or femoral arterial catheterization.
5. The accuracy of a directly recorded arterial pressure waveform is determined by the natural frequency and damping coefficient of the pressure monitoring system. The optimal dynamic response of the system

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   will be achieved when the natural frequency is high, thereby allowing accurate pressure recording across a wide range of damping coefficients.
6. Rather than the common placement at the midaxillary line, the preferred position for alignment (or "leveling") of external pressure transducers is approximately 5 cm posterior to the sternomanubrial junction. When using external transducers and fluid-filled monitoring systems, this transducer location will eliminate confounding hydrostatic pressure measurement artifacts.
7. Because of wave reflection and other physical phenomena, the arterial blood pressure recorded from peripheral sites has a wider pulse pressure than central aortic pressure does.
8. Methods to reduce mechanical complications from central venous catheters include the use of ultrasound vessel localization, venous pressure measurement before the insertion of large catheters, and radiographic confirmation that the catheter tip lies outside the pericardium and parallel to the walls of the superior vena cava.
9. Of the many complications of central venous and pulmonary artery catheters, catheter misuse and data misinterpretation are among the most common.
10. Pulmonary artery wedge pressure is a delayed and damped reflection of left atrial pressure. Wedge pressure provides a close estimate of pulmonary capillary pressure in many cases, but it may underestimate capillary pressure when postcapillary pulmonary vascular resistance is increased, as in patients with sepsis.
11. The use of central venous, pulmonary artery diastolic, or pulmonary artery wedge pressure as an estimate of left ventricular preload is subject to many confounding factors, including changes in diastolic ventricular compliance and juxtacardiac pressure.
12. Most randomized prospective clinical trials have failed to show that pulmonary artery catheter monitoring results in improved patient outcome. Reasons cited for these results include misinterpretation of catheter-derived data and failure of hemodynamic therapies that are guided by specific hemodynamic indices.
13. Systolic pressure variation, the change in systolic arterial blood pressure measured during a positive-pressure mechanical ventilation cycle, provides an accurate measure of left ventricular preload that is more reliable than central venous or pulmonary artery pressure measurements.
14. Thermodilution cardiac output monitoring, the most widely used clinical technique, is subject to thermal errors introduced by rapid intravenous fluid administration, positive-pressure mechanical ventilation, and tricuspid valve regurgitation.
15. Mixed venous hemoglobin saturation is inversely proportional to cardiac output, but is also dependent on arterial hemoglobin saturation, hemoglobin concentration, and oxygen consumption.
16. Newer methods of cardiac output monitoring, including esophageal Doppler and pulse contour analysis, allow beat-to-beat estimation of left ventricular stroke volume and measurement of other cardiovascular variables.
17. The activated coagulation time is the most widely used method for point-of-care coagulation testing and titration of intraoperative heparin therapy. Alternative coagulation tests assess blood heparin concentration, platelet function, or viscoelastic properties of the coagulation system.