monitoring麻醉监测.ppt

Monitoring,Sanqing Jin, pH.D., M.D., Department of Anesthesia, Sixth Affiliated Hospital， Sun Yat-sen University 中山大学附属第六医院麻醉科 靳三庆 博士 博士生导师,I. Standard monitoring,AStandard monitoring for general anesthesia involves oxygenation, ventilation, circulation, and temperature. BStandard monitoring for monitored anesthesia care and regional anesthesia involves oxygenation, ventilation, circulation, and temperature. CAdditional monitoring.,II. Cardiovascular system,ACirculation,1Flow to organs is directly related to pressure gradient and inversely related to vascular resistance. 2Pressure gradient can be estimated by the difference between mean arterial pressure (MAP) and venous pressure, or, for the cerebral circulation in the case of increased intracerebral pressure (ICP), the difference between MAP and ICP.,ACirculation,3. Signs and symptoms of perfusion abnormalities a. Central nervous system: mental status changes, neurologic deficits. b. Cardiovascular system: chest pain, shortness of breath, ECG abnormalities, wall motion abnormalities. c. Renal: decreased urine output, elevated BUN and creatinine, decreased fractional excretion of sodium. d. Gastrointestinal: abdominal pain, decreased bowel sounds, hematochezia. e. Peripheral: cool limbs, poor capillary refill, diminished pulses.,B. ECG,1. Mechanism of monitoring a. Electrode pads. b. Electrode locations. c. Modes and options Monitors often have several choices for filtering of noise, most commonly called “diagnostic”and “monitor” modes. The diagnostic mode should be used when monitoring for ischemia. Automatic trending of ST segment changes is often available and useful for monitoring the development of ischemia over time.,B. ECG,2. Rhythm detection 3. Ischemia detection. Monitoring leads II and V5 allows for detection of ischemia anywhere in a large area of the myocardium. Lead II monitors the inferior portion of the heart, supplied by the right coronary artery. Lead V5 monitors the bulk of the left ventricle, supplied by the left anterior descending artery. Lead I may be monitored on patients in whom the left circumflex artery is at risk.,C. Arterial blood pressure,1. Analysis. Systolic and diastolic blood pressures are measured by a variety of methods. The pressure created by a contracting heart corresponds to the systolic pressure, while the pressure during relaxation corresponds to the diastolic blood pressure. Mean arterial blood pressure is the average arterial blood pressure during systole and diastole.,C. Arterial blood pressure,2. Manual blood pressure a. Auscultation. b. Limitations Cuff size. The cuff width should cover two-thirds of the upper arm or thigh. Requires active operator participation Prone to operator error and interpretation Vasoconstriction and low blood pressure may make sounds difficult to auscultate. Rapid deflation may give low pressure readings.,c. Doppler or palpation Palpation also may be used to determine approximate systolic blood pressure based on whether the pulse may be palpated at key points: radial artery (80 mm Hg), femoral artery (60 mm Hg), or carotid artery (50 mm Hg). This method provides estimates when the blood pressure is very low. d. Limitations Cannot determine diastolic blood pressure. Same limitations as auscultation method.,C. Arterial blood pressure,3. Automated noninvasive blood pressure. a. Limitations Motion artifact. Venous congestion and ischemia may result from frequent blood pressure measurements. Dysrhythmias may make values difficult to interpret or increase cycle time. Very low or high blood pressures may not correlate with intra-arterial measurements.,C. Arterial blood pressure,4. Invasive blood pressure monitoring. a. Indications Need for tight blood pressure control (e.g., induced hyper- or hypotension). Hemodynamically unstable patient. Frequent arterial blood sampling. Inability to utilize noninvasive blood pressure measurements.,C. Arterial blood pressure,b. Interpretation Systolic blood pressure is often monitored in situations when high pressure may cause rupture (e.g., aneurysm). . MAP is often monitored for assessing adequate perfusion pressure of vital organs.,C. Arterial blood pressure,c. Materials. Transducer. Tubing. Set-up. 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 Femoral and axillary artery cannulation is best performed. The modified Allen test. Blood pressure and pulses should be assessed in both right and left sides. 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. 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. Rare complications include arterial thrombosis, ischemia, infection, and fistula or aneurysm formation.,D. Central venous pressure (CVP) and cardiac output,1. CVP a. Indications Measurement of the right heart filling pressures to assess intravascular volume and right heart function. Drug administration to the central circulation. Intravenous access for patients with poor peripheral access. Indicator injection for cardiac output determination (e.g., green dye cardiac output). Access for insertion of pulmonary artery catheter.,D. CVP and cardiac output,b. Waveform. The CVP tracing contains three positive deflectionsthe a, c, and v wavesand two negative slopesthe 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 Range. The CVP is normally 2 to 6 mm Hg. 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, 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.,D. CVP and cardiac output,d. Pathology and CVP Cannon a waves are due to the atrium contracting against a closed tricuspid valve, as during atrioventricular dissociation. 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. Multiple lumen catheters are directly inserted. An introducer catheter is a large-bore catheter with a septum valve. Ultrasound imaging can be used to help identify the anatomy, assist catheter insertion, and verify placement.,D. CVP and cardiac output,c. Complications Dysrhythmias. Arterial puncture. Pneumothorax, hemothorax, hydrothorax, chylothorax, or pericardial tamponade may become evident with vital sign changes. They are in part ruled out with chest radiography. The risk of pneumothorax is highest with subclavian vein insertion. Infection and air embolism may occur.,D. CVP and cardiac output,d. internal jugular Seldinger technique. Position and preparation. Landmarks. Placement. Lidocaine (1%) infiltrate the soft tissues. A finder needle is inserted. (6) A thin-wall needle or a catheter. (7) The guide wire is passed. A rigid dilator is advanced. A catheter or introducer is inserted. A chest radiograph.,D. CVP and cardiac output,e. The SCV is one of the most common central venous line locations. Position and preparation. Landmarks: clavicle, suprasternal notch, and lateral border of the SCM. Placement.,D. CVP and cardiac output,f. Femoral vein. Position and preparation. Landmarks include the femoral artery, inguinal ligament, anterior superior iliac spine (ASIS), and pubic tubercle. The femoral vein is immediately medial to the femoral artery. If the artery is not palpable, it is reliably located one-third of the distance from the pubic tubercle to the ASIS. Placement.,D. CVP and cardiac output,g. External jugular vein is cannulated similarly to an internal jugular vein. h. Basilic vein may be used to access the central circulation with a long catheter. Passing the guide wire into the SCV may be difficult but may be facilitated by abducting the ipsilateral arm and turning the head toward the side of insertion.,D. CVP and cardiac output,3. Pulmonary artery catheterization and pulmonary artery occlusion pressures. a. Mechanism. Inserted through introducer catheter. It passes through the vena cava, right atrium, and right ventricle and into the pulmonary artery. The PAC is able to measure 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 Unexplained hypotension. Access for cardiac pacing. Surgical procedures with significant physiologic changes (e.g., open aortic aneurysm repair, lung or liver transplant). Acute myocardial infarction with shock. The PAC should be used only if the potential benefit of diagnosis or guidance in treatment outweighs the risks of complications. The PAC should be discontinued once active measurement is no longer necessary.,D. CVP and cardiac output,c. PAP and PAOP 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. 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. Increase in PAOP can be due to an increase in end-diastolic volume, decrease in compliance, or both. Decrease in PAOP can be due to a decrease in end-diastolic volume, increase in compliance, or both.,D. CVP and cardiac output,e. Pathology and PAOP Large a waves may be due to either left ventricular hypertrophy (LVH) or atrioventricular dissociation. Large v waves are the result of mitral regurgitation. Right heart dilatation can cause shifting of the interventricular septum into the left ventricle, decreasing the left ventricular end diastolic compliance. Thus, LVEDP will be elevated. Pulmonary embolism will cause an elevation of the PAP without a concomitant elevation of the PAOP.,D. CVP and cardiac output,f. Materials/catheter types: Venous infusion (VIP, VIP+) catheters provide extra ports for infusion and sampling. Paceports. Continuous cardiac output catheters. Oximetric catheters. 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 commonly 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 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. Dye dilution is commonly done with a central venous catheter and an arterial line.,D. CVP and cardiac output,c. Physiologic interpretation The typical range of CO is 4 to 8 L/min, while the CI is 2.4 to 4.0 L/min/m2. Respiration will affect the cardiac output, cardiac output should be measured at end-expiration. 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: Sheath placement. Balloon examination. All ports are flushed to ensure patency and are attached to calibrated pressure transducers Placement. Securing the sheath to the introducer proximally and at the 70-cm 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 low-flow state, or a dilated right ventricle.,D. CVP and cardiac output,e. Complications Dysrhythmias. Right bundle-branch block. PA rupture or infarction. Pacemakers do not contraindicate PAC placement, although fluoroscopic guidance should be used if the pacemaker is less than 6 weeks old. Balloon rupture. (6) Valve damage, catheter knotting, thrombus formation, and infection.,D. CVP and cardiac output,6. Echocardiography (echo) a. Mechanism. b. Indications Hypotension of unknown cause. Uninterpretable PAC values. Suspected intracardiac masses or vegetations. Valvular abnormalities. Shunts. (6) Air embolism. Pericardial disease. Thoracic aneurysm/dissection.,D. CVP and cardiac output,c.Methods Transthoracic echocardiogram. Transesophageal echocardiogram requires that the patient be topically, locally, or generally anesthetized, but it may be performed intraoperatively and allows superior visualization of the left heart.,III. Respiratory system,A. Mandatory respiratory monitors during general anesthesia Pulse oximetry, capnography, a fraction of inspired oxygen analyzer, and a disconnect alarm. Direct visualization of the chest and a precordial or esophageal stethoscope may provide additional information. During regional anesthesia, respiration may be monitored with direct visualization, oximetry, and capnography.,B. Oxygenation,Easily measured by pulse oximetry. Other methods: qualitative assessment of skin color, and arterial blood gas sampling. 1. Method. 2. Interpretation. Normal range in a healthy adult is 96% to 99%, while values above 88% may be acceptable in patients with lung disease. A high pulse oximeter reading (SpO2) generally indicates that oxygen is available in the lungs, taken up in the blood, and delivered to distal tissues. A low SpO2 may be due to a problem along the above pathway or to an error in monitoring.,B. Oxygenation,3. Limitations. a. Oximetry may be a late reporter of inadequate gas exchange. b. Carboxyhemoglogin will provide falsely elevated readings. c. Methemoglobin absorbs light at both 660 and 940 nm, resulting in a saturation of 85%, which does not correlate with the true saturation.,B. Oxygenation,d. Methylene blue, indocyanine green, indigo carmine, and isosulfan blue injections transiently result in falsely low saturation readings. e. SpO2 tends to be falsely overestimated at low saturations (below 80%). f. Low perfusion, motion, and nail polish may cause SpO2 measurements to be uninterpretable or unreliable.,C. Ventilation,Ventilation is assessed by end-tidal carbon dioxide measurements (i.e., capnography) and spirometry. 1. Method. The measurement of carbon dioxide is often based on infrared light absorption to determine concentration. Carbon dioxide may be measured either at the breathing circuit (mainstream capnograph) or via aspiration of gas samples by the capnograph (sidestream capnograph).,C. Ventilation,2. Waveform. a. Phase 0 is the inspiratory segment. b. Phase I is the carbon dioxide-free gas that is not involved in gas exchange. c. Phase II is the rapid upswing. d. Phase III is a plateau that involves alveolar gas and has a small positive slope. PetCO2 is measured at the end of phase III. e. Phase IV is a terminal upswing. f. Alpha angle.,C. Ventilation,3. Range and analysis a. Normally, PetCO2 is 2 to 5 mm Hg lower than arterial CO2 pressure, so the typical range for end-tidal carbon dioxide during general anesthesia is 30 to 40