【正文】 . ? ⑷ Very low or high blood pressures may not correlate with intraarterial measurements. C. Arterial blood pressure ? 4. Invasive blood pressure monitoring. ? a. Indications ? ⑴ Need for tight blood pressure control (., induced hyper or hypotension). ? ⑵ Hemodynamically unstable patient. ? ⑶ Frequent arterial blood sampling. ? ⑷ Inability to utilize noninvasive blood pressure measurements. C. Arterial blood pressure ? b. Interpretation ? ⑴ Systolic blood pressure is often monitored in situations when high pressure may cause rupture (., aneurysm). ? ⑵ . MAP is often monitored for assessing adequate perfusion pressure of vital ans. C. Arterial blood pressure ? c. Materials. ? ⑴ Transducer. ? ⑵ Tubing. ? ⑶ Setup. ? ⑷ Flush apparatus. C. Arterial blood pressure ? 5. Procedure: arterial cannulation ? a. Locations. ? b. Direct cannulation technique of the radial artery. ? c. Transfixion technique (also called bloodless technique). C. Arterial blood pressure ? d. Considerations for placement ? ⑴ Femoral and axillary artery cannulation is best performed. ? ⑵ The modified Allen test. ? ⑶ Blood pressure and pulses should be assessed in both right and left sides. ? ⑷ Prior cannulation may result in thrombosis and proximal pulsation should be assessed before placement. C. Arterial blood pressure ? e. Complications may necessitate using an alternative means of blood pressure measurement. ? ⑴ Dampened waveforms may result from arterial obstruction, catheter occlusion or clot, kinking of the pressure tubing, air in the tubing, loss of flush pressure in tubing, or transducer failure. ? ⑵ Rare plications include arterial thrombosis, ischemia, infection, and fistula or aneurysm formation. D. Central venous pressure (CVP) and cardiac output ? 1. CVP ? a. Indications ? ⑴ Measurement of the right heart filling pressures to assess intravascular volume and right heart function. ? ⑵ Drug administration to the central circulation. ? ⑶ Intravenous access for patients with poor peripheral access. ? ⑷ Indicator injection for cardiac output determination (., green dye cardiac output). ? ⑸ Access for insertion of pulmonary artery catheter. D. CVP and cardiac output ? b. Waveform. The CVP tracing contains three positive deflections—the a, c, and v waves—and two negative slopes—the x and y descents. ? The waves correspond to atrial contraction, isovolemic ventricular contraction including tricuspid bulging, and right atrial filling, respectively. The x descent corresponds to atrial relaxation and systolic collapse, and the y descent corresponds to early ventricular filling and diastolic collapse. D. CVP and cardiac output ? c. Analysis ? ⑴ Range. The CVP is normally 2 to 6 mm Hg. ? ⑵ Decreases in CVP indicate an increase in cardiac performance, decreased venous return, or a decrease in intravascular volume (mean systemic pressure). When a CVP decrease is associated with an increase in blood pressure, without changes to the systemic vascular resistance, the CVP has fallen because of increased cardiac performance. If blood pressure is decreased, then decreased CVP is due to decreased intravascular volume or venous return. D. CVP and cardiac output ? ⑶ Increases in CVP indicate either a decrease in cardiac performance, increased venous return, or an increase in volume (mean systemic pressure). When this increase is associated with increased blood pressure, without changes to the systemic vascular resistance, the cause of increased CVP is an increase in volume or venous return. With an associated decrease in blood pressure, the increased CVP is due to decreased cardiac performance. CVP BP 原因 處理 低 低 血容量不足 補(bǔ)充血容量 低 正常 心功能良好，血容量輕度不足 適當(dāng)補(bǔ)充血容量 高 低 心功能差，心排血量減少 強(qiáng)心、供氧、利尿、糾正酸中毒、適當(dāng)控制補(bǔ)液或謹(jǐn)慎選用血管擴(kuò)張藥 D. CVP and cardiac output ? d. Pathology and CVP ? ⑴ Cannon a waves are due to the atrium contracting against a closed tricuspid valve, as during atrioventricular dissociation. ? ⑵ Large v waves are due regurgitant flow during ventricular contraction, as with tricuspid regurgitation. D. CVP and cardiac output ? e. Positive pressure ventilation will affect both the cardiac output and venous return. At low levels of PEEP, the CVP increases with increased PEEP. At high levels of PEEP (over about 15 cm H2O), CVP increases as the cardiac output is depressed because of impaired right ventricular output. D. CVP and cardiac output ? 2. Procedure: CVP ? a. Locations. ? b. Materials. ? ⑴ Multiple lumen catheters are directly inserted. ? ⑵ An introducer catheter is a largebore catheter with a septum valve. ? ⑶ Ultrasound imaging can be used to help identify the anatomy, assist catheter insertion, and verify placement. D. CVP and cardiac output ? c. Complications ? ⑴ Dysrhythmias. ? ⑵ Arterial puncture. ? ⑶ Pneumothorax, hemothorax, hydrothorax, chylothorax, or pericardial tamponade may bee evident with vital sign changes. They are in part ruled out with chest radiography. The risk of pneumothorax is highest with subclavian vein insertion. ? ⑷ Infection and air embolism may occur. D. CVP and cardiac output ? d. internal jugular Seldinger technique. ? ⑴ Position and preparation. ? ⑵ Landma