**Risk stratification**

128 Perioperative Considerations in Cardiac Surgery

Myocardial ischaemia is one of the most frequent causes of precardiotomy low output syndrome. The dysfunctional myocardium may not be irreversibly damaged and possibly only 'stunned'or 'hibernating'. Revascularization of the reversibly injured heart areas may result in improved cardiac performance. The first priority should therefore be prompt surgery avoiding further alterations in myocardial contractility, possibly by introducing an IABP preoperatively. However, inadequate myocardial protection during cardiac surgery may exacerbate ischaemic injury in some patients. Patients with longer standing previous poor preoperative cardiac function or with recently irreversibly injured ischaemic heart

areas, will of course continue to have poor ventricular performance postoperatively.

conduction issues, pulmonary hypertension and right ventricular failure.

For the successful therapeutic approach of failure to wean, a correct diagnosis of the underlying cause is necessary. The heart failure may be procedure related or patient specific and includes inadequate myocardial protection, reperfusion injury, ischaemia, infarction, incomplete revascularization, metabolic, uncorrected pathology, mechanical issues,

The priority is to preserve end organ function. Preload and heart rhytm should be optimized, and positive inotropic and/or vasopressor drugs are often used to maintain adequate cardiac output and blood pressure. Although this strategy will restore

Heart failure cannot be ascertained unless the volume status is optimal. However, it is difficult to ascertain volume loading using single haemodynamic measures. Pressure estimates such as pulmonary capillary wedge pressure and central venous pressure are generally unreliable indicators of LV and RV preload. Uncoupling between PCWP and LVEDP frequently occurs as a consequence of elevated pulmonary vascular resistance, pulmonary

Volumetric estimates by echocardiography or transpulmonary thermal dilution techniques are more predictive of preload. In predicting fluid responsiveness in ICU patients, it is preferable to use more reliable dynamic indicators reflecting hypovolaemia, such as stroke volume variation, than static parameters. (16) Several devices are now being used to assess

Echocardiography is of great value in the perioperative cardiac surgical setting. It not only is helpfull in assessing the optimal volume status, but may also immediately identify causes of cardiovascular failure, including valvular problems, cardiac tamponade, systolic anterior motion of the anterior mitral valve leaflet and pulmonary embolism. Echocardiography may differentiate between acute right, left and global heart failure as well as between systolic and

If there are echocardiographic signs of RV failure, a pulmonary artery catheter (PAC) preferably with continuous SvO2 measurement should be introduced. PACs can differentiate between pulmonary hypertension and RV ischaemia, which necessitates a reduction of RV afterload. PAC and TEE are complementary to each other for diagnosis and treatment of the cardiac surgical patient. Indications for the use of a PAC are, high risk and/or complex cardiac surgery, hemodynamic instability, low cardiac output syndrome, pulmonary hypertension,

haemodynamics in most patients, mechanical circulatory support may be indicated.

venoconstriction, mitral stenosis and reduction in transmural cardiac compliance.

cardiac function based on pulse contour analysis of an arterial waveform. (17)

*Precardiotomy heart failure* 

*Failure to wean* 

*Postcardiotomy heart failure* 

diastolic dysfunction.

*Monitoring and assessing volume status* 

Risk stratification is increasingly used in open-heart surgery to help adjust resources to predicted outcome. According to all scoring systems major clinical risks include heart failure, unstable coronary syndromes, significant arrhythmias and severe valvular disease. The euroSCORE is mostly used to calculate operative risk, although updating its sensitivity is warranted. (20,21)

In addition to scoring systems, levels at hospital admission of B-type natriuretic peptide (BNP) and the amino-terminal fragment of pro-BNP (NT pro-BNP) are powerful predictors of outcome with regard to in-hospital mortality and rehospitalisation in heart failure patients. (22)
