**1. Introduction**

14 Perioperative Considerations in Cardiac Surgery

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The cardiac surgical procedures are increasingly performed each year up to a number >700000 (data in 1997 in US) per year, of which >600000 are coronary artery bypass grafting (CABG) procedures. After 1997, there has been a gradual decrease in CABG procedures as percutaneous coronary interventions (PCI) grow. In 2005, a total of 699000 cardiac surgical procedures were reported, including 469000 surgical coronary revascularization procedures. It is still debated whether CABG procedures will continue to decrease as relative benefits of PCI continue to be evaluated. As the number of aging population increases and risk factors (e.g.,obesity and diabetes) occur, cardiovascular diseases are also estimated to increase; however, it is not clear that changes in life style or advancing medical management will reduce the prevalance and incidence of these diseases. Although the cardiac surgery is not the primary solution, CABG procedures are still the most commonly performed cardiac procedures and it will remain one of the management options (Thys,2009;London et al,2008). There is an explosive growth in these procedures due to improvements in operative outcomes, inclusion of older and sicker patients for cardiac surgeries and expansion of these surgeries to community hospitals. However, although the physicians develop greater confidence and capacity to perform the procedures, the morbidity, mortality and resource utilization are still higher in the elderly population; especially in octagenarians. Scott et al. (2005) reported longer intensive care unit (ICU) and hospital stay with higher rates of postoperative renal failure and neurologic complications; and Baskett et al. (2005) reported more death and stroke after CABG in octagenarians. As the cardiac surgical procedures grow with an aging population with increased mortality and morbidity, more anesthesiologists become specialized in cardiovascular anesthesiology, practicing cardiac anesthesia excusively in active cardiac surgical centers; changing their focus from anesthetic management of patients with cardiovascular diseases to cardiovascular medicine; medical and surgical management of cardiovascular patients (Thys,2009).

#### **2. Anesthetic management**

The primary goal of cardiac surgery is not just a minimally acceptable outcome where the patient survives without life-threatenening complications or persistent clinically manifest organ dysfunctions or simply hospital survival; but a healthy, productive long-term survivor (Murphy et al,2009).

Anesthetic protocols in cardiac surgery are investigated and analized in terms of their effect on postoperative mortality and incidence of myocardial infarction following cardiac surgery, postoperative cardiac troponin release, need for inotropic support, time on mechanical ventilation, ICU and hospital stay (Landoni et al,2009).

#### **2.1 Preoperative evaluation and premedication**

In order to reduce the fear and anxiety of the patient, provide analgesia for painful interventions such as vascular cannulation before anesthetic induction and to provide amnesia to some degree, pharmacological interventions are used. These agents are also supposed to prevent the anginal episodes which are clinically silent preoperatively. Oral, intravenous or intramuscular benzodiazepines are the agents that are most frequently chosen (London et al,2008). Agents and their dosages to be selected depend on the patients' age and physiologic status. High doses are desirable for the patients with coronary artery disease, whereas low doses are more appropriate for patients with valvular diseases whose physiologic status is compansated with enhanced sympathetic tone (Liu et al,2004). However, on arrival to the operating room the patients may receive further medications in case of an inadequate sedation, prior to the interventions that are planned before the induction. The beneficial effects of premedication should also be secured by the proper conditions of the operating room including the temperature and also the verbal interaction with the patient (London et al,2008).

#### *Most popular premedicants*

For anxiolysis and amnesia;


The anesthetist has an important role in preoperative administration of cardiovascular medications especially the anti-anginal medications, ensuring that these agents are ordered for morning with sips of water, as the cardiac anesthesiologist is becoming a 'perioperative physician' (London et al,2008).

#### **2.2 Monitoring**

On arrival to the operating room, before induction of anesthesia, preoxygenation, monitoring with pulse oximetry, ECG, non-invasive BP and radial artery cannulation for ABP, ECG and also for the high-risk patients central venous catheters and pulmonary artery catheter should be in place (Reich et al,2008).

#### **2.2.1 Electrocardiogram (ECG)**

A multi-lead ECG system with a continuous paper writeout and online ST-segment trending system is useful in early diagnosis of myocardial ischemia and detecting arrhythmias. Also a preinduction rhythm strip or frozen on the monitor screen may help to assess the changes intraoperatively (Morgan et al,2002). An angiographically identified areas that are at risk for transmural ischemia can be observed more sensitively by specific placement of the leads

organ dysfunctions or simply hospital survival; but a healthy, productive long-term

Anesthetic protocols in cardiac surgery are investigated and analized in terms of their effect on postoperative mortality and incidence of myocardial infarction following cardiac surgery, postoperative cardiac troponin release, need for inotropic support, time on

In order to reduce the fear and anxiety of the patient, provide analgesia for painful interventions such as vascular cannulation before anesthetic induction and to provide amnesia to some degree, pharmacological interventions are used. These agents are also supposed to prevent the anginal episodes which are clinically silent preoperatively. Oral, intravenous or intramuscular benzodiazepines are the agents that are most frequently chosen (London et al,2008). Agents and their dosages to be selected depend on the patients' age and physiologic status. High doses are desirable for the patients with coronary artery disease, whereas low doses are more appropriate for patients with valvular diseases whose physiologic status is compansated with enhanced sympathetic tone (Liu et al,2004). However, on arrival to the operating room the patients may receive further medications in case of an inadequate sedation, prior to the interventions that are planned before the induction. The beneficial effects of premedication should also be secured by the proper conditions of the operating room including the temperature and also the verbal interaction

The anesthetist has an important role in preoperative administration of cardiovascular medications especially the anti-anginal medications, ensuring that these agents are ordered for morning with sips of water, as the cardiac anesthesiologist is becoming a 'perioperative

On arrival to the operating room, before induction of anesthesia, preoxygenation, monitoring with pulse oximetry, ECG, non-invasive BP and radial artery cannulation for ABP, ECG and also for the high-risk patients central venous catheters and pulmonary artery

A multi-lead ECG system with a continuous paper writeout and online ST-segment trending system is useful in early diagnosis of myocardial ischemia and detecting arrhythmias. Also a preinduction rhythm strip or frozen on the monitor screen may help to assess the changes intraoperatively (Morgan et al,2002). An angiographically identified areas that are at risk for transmural ischemia can be observed more sensitively by specific placement of the leads

mechanical ventilation, ICU and hospital stay (Landoni et al,2009).

**2.1 Preoperative evaluation and premedication** 

with the patient (London et al,2008).

 Diazepam oral: 0.1-0.15 mg/kg Midazolam intravenous: 1-2 mg

Fentanyl intravenous: 50-75 µg

physician' (London et al,2008).

**2.2.1 Electrocardiogram (ECG)** 

Morphine intramuscular: 0.1-0.15 mg/kg

catheter should be in place (Reich et al,2008).

*Most popular premedicants*  For anxiolysis and amnesia;

For analgesia;

**2.2 Monitoring** 

survivor (Murphy et al,2009).

(Reich et al,2008). The electrocoutery may interfere with ECG recordings resulting in difficulty in dysrhythmia analysis in the operating room (Morgan et al,2002).

#### **2.2.2 Arterial blood pressure monitoring (ABP)**

The radial artery is used for the CABG procedures to monitor the blood pressure. The cannulation is applied before anesthetic induction in order to observe the hemodynamic response closely (Reich et al,2008). Radial artery cannulation requires the testing of the competancy of ulnar collateral circulation of the hand in case of radial artery thrombosis. This test is the Allen test; however it is not completely reliable. Some centers prefer the nondominant side for cannulation and some other prefer to use the side opposite to the proposed internal mammarian artery dissection to avoid inaccurate measurements caused by the sternal retractors tenting the subclavian artery. Furthermore, after the period of hypothermia there can be alterations in the measurements from radial artery (lower than aortic pressure with a gradient 10-30 mmHg) which is mainly caused by decreased vascular resistance. Temporarily measuring blood pressure directly from the aorta via a needle or cardioplegia cannula can be an acceptable approach (Morgan et al,2002).

#### **2.2.3 Central venous cannulation**

Cardiac surgery is associated with large fluid shifts and need for multiple drug infusions (Morgan et al,2002). In order to measure pressure to regulate volume infusion and for both volume and vasoactive drug administration, central venous catheterization (CVC) has become a routine practice (London et al,2008). CVC is used for measuring the right ventricle (RV) filling pressures giving an estimate for intravascular volume status and RV function. For accurate measurement of the pressures, the catheter tip should be in one of the large thoracic veins or the right atrium. With a short and straight course to the right atrium (RA) assuring RA or superior venous cava (SVC) localization of the catheter tip, internal jugular vein is preferred for the site of this central catheterization (Reich et al,2008).

Following serial measurements to observe the trends is more reliable and safe when compared to individual numbers. Central venous pressure (CVP) is not a direct indicator of left heart filling pressure, but it may provide an estimate for these pressures in patients with good LV function. The catheter can also be used for both indicating the RA pressures and cerebral venous pressure if the tip is in SVC. The increase in CVP may result in a decrease in cerebral perfusion pressure. Occasionally this may be caused by a malposition of the catheter during CPB, which is to be corrected immediately by the surgeon to avoid cerebral edema and poor cerebral perfusion (Reich et al,2008).

CVC may be applied before induction using sedation including small doses of midazolam and fentanyl supplemented by oxygen via a face mask avioiding hypoxia, or after induction of anesthesia. Multi-lumen catheters allow for both fluid administration and drug infusions at the same time (Morgan et al,2002).

#### **2.2.4 Pulmonary artery catheterization (PAC)**

The PAC providing various physiologic information has been shown to have little effect on clinical outcome, leading to a lower use currently; decreased 60-80% over the past decade. Although the criteria to use PAC have not been demonstrated clearly, it is recommended to be reserved for high-risk patients, as the patients with multi-system dysfunction are increasingly scheduled for cardiac surgical procedures (Reich et al,2008).

*High-risk patients requiring PAC (Reich et al,2008)* 

	- EF<40%
	- Acute or Chronic congestive heart failure
	- Elevation of left ventricular end-diastolic pressure (LVEDP) on preoperative catheterization
	- Need for preoperative intraaortic balon pump (IABP)
	- Acute or chronic severe mitral regurgitation due to ischemia
	- Ventricular septal defect after myocardial infarction
	- Other mechanical complications
	- Recent, large myocardial infarction
	- Severe unstable angina
	- Known poor revascularization targets or severe microcirculatory disease
	- Reoperation
	- Catheterization laboratory PCI 'crash'
	- Renal failure (need for dialysis)
	- Severe chronic obstructive pulmonary disease

PAC provides detailed information with various parameters such as PCWP, PA diastolic pressure and derived parameters, estimating the left ventricular filling pressures-preload more precisely than CVC (Reich et al,2008;Morgan et al,2002). However, there are some limiting factors altering the accuracy of these measurements such as mitral stenosis, LA myxoma, pulmonary venous obstruction, elevated alveolar pressure, decreased left ventricular compliance and aortic insufficiency; which are to be considered during the anesthetic management (Reich et al,2008).
