【文章內(nèi)容簡(jiǎn)介】 sure the pressure at each of the locations mentioned above. ? Inflating the balloon at the tip of the catheter allows measurement of PAOP, or “wedge”pressure, reflecting the left atrial pressure and left ventricular preload. D. CVP and cardiac output ? b. Indications ? ⑴ Unexplained hypotension. ? ⑵ Access for cardiac pacing. ? ⑶ Surgical procedures with significant physiologic changes (., open aortic aneurysm repair, lung or liver transplant). ? ⑷ Acute myocardial infarction with shock. ? ⑸ The PAC should be used only if the potential benefit of diagnosis or guidance in treatment outweighs the risks of plications. The PAC should be discontinued once active measurement is no longer necessary. D. CVP and cardiac output ? c. PAP and PAOP ? ⑴ Waveform. The PAP waveform is similar in shape to the systemic arterial waveform. The PAC could measure the PAOP recording, which is similar to the CVP waveform. This waveform approximates the left atrial pressures. ? ⑵ Range. The normal PAP is 15 to 30 mm Hg systolic and 5 to 12 mm Hg diastolic. The normal range for PAOP is 5 to 12 mm Hg. At end expiration, this approximates the left atrial pressure and the left ventricular end diastolic volume. D. CVP and cardiac output ? d. PAOP analysis is used to assess the left heart performance. ? ⑴ Increase in PAOP can be due to an increase in enddiastolic volume, decrease in pliance, or both. ? ⑵ Decrease in PAOP can be due to a decrease in enddiastolic volume, increase in pliance, or both. D. CVP and cardiac output ? e. Pathology and PAOP ? ⑴ Large a waves may be due to either left ventricular hypertrophy (LVH) or atrioventricular dissociation. ? ⑵ Large v waves are the result of mitral regurgitation. ? ⑶ Right heart dilatation can cause shifting of the interventricular septum into the left ventricle, decreasing the left ventricular end diastolic pliance. Thus, LVEDP will be elevated. ? ⑷ Pulmonary embolism will cause an elevation of the PAP without a conitant elevation of the PAOP. D. CVP and cardiac output ? f. Materials/catheter types: ? ⑴ Venous infusion (VIP, VIP+) catheters provide extra ports for infusion and sampling. ? ⑵ Paceports. ? ⑶ Continuous cardiac output catheters. ? ⑷ Oximetric catheters. ? ⑸ Right ventricular ejection fraction catheters use a rapid response thermistor to calculate the right ventricular ejection fraction in addition to cardiac output. D. CVP and cardiac output ? 4. Cardiac output ? a. Mechanism. Cardiac output is most monly determined with either thermodilution or dye dilution. A known quantity of tracer (cold saline or dye) is injected into the central circulation, and the concentration of the tracer is plotted as a function of time as it is pumped through the circulation. An algorithm is then used to correlate this with cardiac output/index. D. CVP and cardiac output ? b. Methods of measurement ? ⑴ Thermodilution :Typically, 10 mL of cold saline is injected into the CVP port over 4 seconds and the change in temperature is monitored at the thermistor located at the tip of the catheter within the main pulmonary artery. ? ⑵ Dye dilution is monly done with a central venous catheter and an arterial line. D. CVP and cardiac output ? c. Physiologic interpretation ? ⑴ The typical range of CO is 4 to 8 L/min, while the CI is to L/min/m2. ? ⑵ Respiration will affect the cardiac output, cardiac output should be measured at endexpiration. ? ⑶ Pathology and cardiac output ? (a) Tricuspid regurgitation tends to underestimate the cardiac output/cardiac index. ? (b) Intracardiac shunting will produce erroneous cardiac output measurements. D. CVP and cardiac output ? 5. Procedure: pulmonary artery catheter ? a. Locations and prep are similar to that of the central venous catheter. The PAC is invariably placed through an introducer catheter. D. CVP and cardiac output ? b. Technique. The PAC is prepared and examined as follows: ? ⑴ Sheath placement. ? ⑵ Balloon examination. ? ⑶ All ports are flushed to ensure patency and are attached to calibrated pressure transducers.. ? ⑷ Placement. ? ⑸ Securing the sheath to the introducer proximally and at the 70cm mark distally ensures the ability to manipulate the PAC aseptically. D. CVP and cardiac output ? c. Distances. From the right internal jugular vein, each location appears “on the tens.”The right atrium is reached at 20 cm, the right ventricle is reached at 30 cm, the pulmonary artery is reached at 40 cm, and the PAOP should be at 50 cm. ? d. During PAC insertion, difficulty in passing the catheter into the right ventricle and pulmonary artery may be encountered because of balloon malfunction, valvular lesions, a lowflow state, or a dilated right ventricle. D. CVP and cardiac output ? e. Complications ? ⑴ Dysrhythmias. ? ⑵ Right bundlebranch block. ? ⑶ PA rupture or infarction. ? ⑷ Pacemakers do not contraindicate PAC placement, although fluoroscopic guidance should be used if the pacemaker is less than 6 weeks old. ? ⑸ Balloon rupture. ? (6) Valve damage, catheter knotting, thrombus formation, and infection. D. CVP and cardiac output ? 6. Echocardiography (echo) ? a. Mechanism. ? b. Indications ? ⑴ Hypotension of unknown cause. ? ⑵ Unin