Cardiovascular Monitoring in Noncardiac Surgery





Key Points




  • 1.

    Excellent cardiac and hemodynamic management is essential to achieving good outcomes in patients with cardiovascular disease, particularly those undergoing high-risk noncardiac surgery.


  • 2.

    Much cardiovascular information can be obtained from the standard American Society of Anesthesiologists monitors, including those usually associated with evaluation of respiratory function (pulse oximetry, capnography). The pulse oximeter plethysmograph can be used to assess adequacy of the peripheral circulation; expired capnography reflects pulmonary blood flow and cardiac output.


  • 3.

    The five-electrode electrocardiographic system commonly used perioperatively allows rapid diagnosis of a wide variety of cardiac abnormalities, including rhythm disturbances, conduction abnormalities, myocardial ischemia, myocardial infarction, and electrolyte abnormalities.


  • 4.

    Although often unreliable as an intravascular volume monitor, invasive monitoring of the central venous pressure (CVP) can be useful in the management of cardiac patients. CVP provides information about the systolic and diastolic performance of the heart in response to fluid administration, as well as waveform information that can aid in the diagnosis of abnormalities such as tricuspid regurgitation and junctional rhythms.


  • 5.

    The pulmonary artery catheter is a very powerful monitor, providing a wide array of data that include right-sided pressures, cardiac performance, and a surrogate for left atrial pressure (pulmonary capillary wedge pressure). Although its use has declined in noncardiac surgery, it is still very useful in select patients such as those with pulmonary hypertension or right ventricular failure. It is also useful for monitoring left ventricular function and solving hemodynamic problems when transesophageal echocardiography is unavailable.


  • 6.

    Minimally invasive and noninvasive means of continuously monitoring arterial blood pressure, as well as cardiac output and dynamic parameters such as stroke volume variation, are now widely used. They are particularly useful in cardiac patients undergoing high-risk surgery. They facilitate perioperative goal-directed therapy (PGDT), enhanced recovery from surgery, and rapid diagnosis of hemodynamic problems.


  • 7.

    Noninvasive monitors that assess tissue oxygenation, pH, and perfusion are likely to be further developed and used. Because the purpose of circulation is tissue perfusion, it is logical to quantify tissue perfusion and oxygenation. Somatic near-infrared spectroscopy is currently used for this purpose in PGDT algorithms.



Perioperative care includes effective cardiac, hemodynamic, and fluid management. Excellent cardiovascular management is particularly important in patients undergoing major noncardiac surgery and those with preexisting cardiovascular disease. It is only with meaningful, accurate monitoring that appropriate cardiac, hemodynamic, and fluid therapy can be provided. This chapter focuses on the various means by which the cardiac and hemodynamic status can be monitored, ranging from noninvasive to highly invasive techniques. Other indicators of cardiovascular function, such as urine output, are discussed as well. Echocardiography is not discussed here; it is presented in Chapter 10 .




Standard American Society of Anesthesiologists Monitors


Most of the standard American Society of Anesthesiologists (ASA) monitors provide information about the cardiovascular system ( Box 9.1 ). Electrocardiogram (ECG), arterial blood pressure, heart rate, and intraarterial pressure tracings are obviously useful, but those used to monitor respiratory function, such as end-tidal carbon dioxide (ETCO 2 ) and pulse oximetry with its plethysmograph tracing, can also provide valuable cardiovascular information. The standard ASA monitors are listed in Table 9.1 .



Box 9.1

Basic Perioperative Monitors of Cardiovascular Function




  • •

    Electrocardiogram


  • •

    Heart rate


  • •

    Noninvasive blood pressure


  • •

    Pulse oximetry with plethysmograph analysis



    • •

      Perfusion index


    • •

      Pleth variability index



  • •

    End-tidal carbon dioxide



    • •

      Pulmonary blood flow



  • •

    Auscultation of heart sounds



    • •

      Amplitude and frequency of S 1 for inotropic state


    • •

      Amplitude and frequency of S 2 for systemic blood pressure





Table 9.1

Standard American Society of Anesthesiologists Monitoring

From American Society of Anesthesiologists Standards for Basic Monitoring, http://www.asahq.org .




























































Category Monitor Frequency
Circulation Electrocardiogram a Continual
Arterial blood pressure a Every 5 min (minimum)
Heart rate a Every 5 min (minimum)
Circulatory function (one of the following) a :


  • •

    Auscultation of heart sounds a



  • •

    Intraarterial pressure tracing a

Continual


  • •

    Ultrasound of peripheral pulse a



  • •

    Pulse plethysmography or oximetry a

Ventilation End-tidal carbon dioxide a Continual
Oxygenation Inspired gas Continual
Pulse oximetry a Continual
Patient color a
Temperature Temperature probe Immediately available, when changes in body temperature are anticipated

a Parameters that are useful in cardiovascular monitoring.



Electrocardiogram


The ECG is a mainstay for monitoring cardiac status. Continuously monitoring cardiac electrical activity, it provides heart rate and rhythm data, as well as assessment of cardiac conduction (PR interval, QRS duration) and repolarization (ST segment, T-wave morphology, and QT interval). The normal morphologies of the ECG signal and the ECG intervals are shown in Fig. 9.1 .




Fig. 9.1


Electrocardiographic morphology of one cardiac cycle and intervals.


A three-lead system, using three or four electrodes (right arm, left arm, left leg, ground), allows monitoring of limb leads I, II, or III, providing primarily rhythm and conduction data. This can suffice for healthy patients, but a five-electrode system (right arm, left arm, left leg, precordial, ground) is usually used perioperatively and in intensive care units. This system allows simultaneous monitoring of a limb lead (usually lead II) and a precordial “V” lead that enhances the detection of myocardial ischemia. The sensitivity for detecting myocardial ischemia when using a combination of leads II and V 5 has been reported to be 80%. The V lead can be placed according to the particular area of interest, ranging from anterior (V 1 ) to lateral (V 6 ) ( Fig. 9.2 ), with V 3 to V 5 generally being the most sensitive for anterior-lateral myocardial ischemia (lead II is used for inferior wall ischemia).




Fig. 9.2


Placement of the five-electrode system commonly used in operating rooms and intensive care units. The precordial lead (V) can be placed according to the area of interest, with the V 3 to V 5 positions generally being the most sensitive for myocardial ischemia.


Myocardial ischemia most often manifests as ST-segment depression, although elevated ST segments, change in T-wave morphology, new conduction defects, or frequent premature ventricular contractions may also be signs of myocardial ischemia. ECG monitoring systems have automated digital signal processing to continuously display heart rate, QT interval, and ST-segment depression or elevation, as well as alarm systems for these parameters.


Abnormal rhythms, such as sinus bradycardia and tachycardia, junctional rhythms, atrial fibrillation, right and left bundle branch blocks, and heart block, are not uncommon in cardiac patients. All these abnormalities can be detected using a five-electrode system ( Tables 9.2 and 9.3 ). Whereas a limb lead such as lead II is preferred for conduction and rhythm detection, the precordial leads are preferred for diagnosis of myocardial ischemia, infarction, and bundle branch blocks.



Table 9.2

Common Perioperative Cardiac Electrical Abnormalities and Their Preferred Lead for Detection




































































Cardiac Abnormality Preferred Lead Common Characteristics
Sinus bradycardia II HR <60 beats/min, with normal P wave and narrow QRS
Sinus tachycardia II HR >100 beats/min, with normal P wave and narrow QRS
Supraventricular tachycardia II HR >100 beats/min, narrow QRS
Ventricular tachycardia II HR >100 beats/min, wide QRS complex
Junctional (AV nodal) rhythm II P waves absent; CVP shows “canon” waves; may be slow
First-degree AV block II PR interval >200 ms
Second-degree AV block Mobitz I II Progressive lengthening of PR interval culminating in nonconducted P wave
Second-degree AV block Mobitz II II Occasional nonconducted P waves
Complete AV block II P waves not associated with QRS
Premature ventricular contractions II Wide QRS, premature with compensatory pause
Premature atrial contractions II Narrow QRS without compensatory pause
Right bundle branch block Precordial P wave followed by wide QRS in V 1 and V 2 ; may be a normal variant
Left bundle branch block Precordial P wave followed by wide QRS in V 5 and V 6 ; if old, may indicate old conduction system injury; if new, may indicate myocardial ischemia
Myocardial ischemia Precordial ST-segment depression
Myocardial infarction Precordial ST-segment elevation

AV, Atrioventricular; CVP, central venous pressure; HR, heart rate.


Table 9.3

Electrocardiographic Morphology of Common Abnormalities Encountered Perioperatively in Cardiac Patients















































ECG Diagnosis Example Comments
Atrial fibrillation


Narrow QRS, irregularly irregular
Atrial flutter


Regular, flutter sawtooth waves, narrow QRS
Complete heart block


No conduction through AV node; P waves unassociated with QRS complexes
AV dissociation


Regular, atrial and ventricular unrelated, QRS duration depends on ventricular source, ventricular rate faster than atrial
Left bundle branch block


V 1 , V 2 , V 3; QRS >0.12 s, regular; ST segment and T deflection opposite that of QRS; rate <100 beats/min; signifies significant coronary disease
Inferior wall myocardial infarction


ST segment elevation in inferior leads (II, III, aVF)
Anterior wall myocardial infarction


ST-segment elevation in anterior precordial leads
Myocardial ischemia


ST-segment depression
Hyperkalemia


Peaked T waves
Premature ventricular contractions
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