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Critical care medicine has increasingly become an area of interest to the obstetrician–gynecologist. Pregnancy complications such as shock, thromboembolism, acute respiratory distress syndrome (ARDS), and coagulation disorders can lead to significant morbidity. Furthermore, the approach to these patients can be influenced by a variety of physiologic changes that are unique to pregnancy. This chapter provides a basic approach to some of the common clinical problems that often require complex multidisciplinary care and knowledge of invasive hemodynamic monitoring.
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The flow-directed pulmonary artery catheter has been a major addition to the clinician's armamentarium because of its applicability to a wide range of cardiorespiratory disorders. The catheter allows simultaneous measurement of central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), cardiac output, and mixed venous oxygen saturation. The pulmonary artery catheter is a 7F triple-lumen polyvinyl chloride catheter with a balloon and thermodilution cardiac output sensor at the tip. The distal port is used to measure PAP when the balloon is deflated and PCWP when inflated. A proximal lumen is present 30 cm from the balloon tip; this can be used to monitor the CVP and to administer fluids and drugs. Both ports can be used to withdraw blood. Oximetric catheters also have 2 optical fibers that permit continuous measurement of mixed venous oxygen saturation by reflection spectrophotometry.
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A 16-gauge catheter is used to gain access to the internal jugular or subclavian vein (Fig. 23–1). Pertinent anatomic landmarks for the internal jugular vein approach are shown in Figure 23–2. A guidewire is then introduced into the vein through the catheter, and the 16-gauge catheter sheath is removed. A pulmonary artery catheter is inserted over the guidewire, and the guidewire is removed. The central venous and pulmonary artery ports are connected to a pressure transducer, so that the characteristic waveforms of the various heart chambers can be identified as the catheter is advanced (Fig. 23–3). When the catheter is in the superior vena cava, the balloon is inflated with 1–1.5 mL of air, and the catheter is advanced forward into the main pulmonary artery. Table 23–1 shows the average distance in centimeters the catheter must be advanced from various insertion sites. From the main pulmonary artery, the flow of blood moves the catheter into a branch of the pulmonary artery, where it wedges and records the PCWP.
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