• Daniel M. Thys, MD

        INTRODUCTION

The decision to use regional anesthesia can be a complex medical choice. Preexisting medical conditions, type of surgery, anesthetic risks, and patient characteristics all may have a profound impact on anesthetic choice and perioperative management. In patients with cardiovascular disease, regional anesthesia techniques (either alone or in conjunction with general anesthesia) can offer the potential perioperative benefits of stress response attenuation, cardiac sympathectomy, earlier extubation, shorter hospital stay, and intense postoperative analgesia.

        Neuraxial anesthesia has been shown to be useful in treating patients with coronary artery disease. This includes treatment of anginal symptoms, primary (or part of a combined) anesthetic for the surgical procedure, and acute postoperative pain management. Its use in the high-risk patient during noncardiac surgery can offer reduced blood loss and need for transfusion and a decreased incidence of thromboembolic events.

        Regional anesthetic options are not limited to neuraxial techniques when dealing with patients with cardiovascular disease. Paravertebral block has also been used as an adjunct to general anesthesia in the management of patients undergoing cardiac surgery. In addition, intercostal nerve blockade and parasternal block can be used for postoperative pain relief in patients after cardiac surgery. Cervical plexus block can be used in the anesthetic management of patients undergoing carotid endarterectomy. Lower extremity blocks, such as combined sciatic-femoral nerve block can also be used in high-risk patients in whom even modest alterations in hemodynamics would not be tolerated.

        Local anesthetics alone or in combination with narcotics are used for regional anesthesia in patients with cardiovascular disease. Ropivacaine is a commonly used local anesthetic during neuraxial anesthesia for cardiac surgery. Although its pharmacologic properties, including onset of action and duration of action, are essentially the same as those of bupivacaine, ropivacaine possesses less cardiotoxic properties, produces less central nervous system depression, and is associated with less motor blockade. Ropivacaine is often combined with sufentanil when used during epidural administration for cardiac surgery. Intrathecal narcotics in combination with general anesthesia can provide intraoperative and postoperative analgesia. The most common undesirable effects of intrathecal opioids are respiratory depression, nausea and vomiting, pruritus, and urinary retention. However, advances in narcotic formulations may allow for sustained- release delivery and target-specific affinity, which may reduce the potential of common narcotic side effects. Standard local anesthetic preparations are used in performing upper and lower extremity blocks in patients with cardiovascular disease.

        The most severe complication from neuraxial anesthesia is epidural hematoma formation. The incidence of hematoma formation ranges from 1:150,000 after epidural instrumentation to 1:220,000 for intrathecal instrumentation. Risk of hematoma formation after either technique is increased if performed before systemic heparinization. Currently, only a minority of practicing anesthesiologists use neuraxial blockade in the management of patients undergoing cardiac surgery. Patients presenting for major noncardiac surgery often receive anticoagulation to prevent venous thrombosis and pulmonary embolism. It appears that anesthesiologists more frequently perform neuraxial blockade on these patients after weighing the risk of hematoma formation against the benefits.

        THORACIC EPIDURAL ANESTHESIA

Physiologic Effects on the Cardiovascular System

Thoracic epidural anesthesia (TEA) blocks the cardiac afferent and efferent sympathetic fibers with loss of chronotropic

and inotropic drive to the myocardium.¹ The level of sympathetic blockade that follows a TEA depends in part on the degree of sympathetic tone before the block. This may explain why different studies report different effects of TEA on the cardiovascular system. Goertz et al.² used transesophageal echocardiography to assess the effects of TEA on cardiac function in healthy volunteers. TEA was not shown to produce significant changes in systolic or diastolic arterial pressures, heart rate, left ventricular end-systolic and end-diastolic crosssectional areas and left ventricular wall stress as measured under general anesthesia. However, left ventricular maximum elastance, as a measure of left ventricular contractility, was significantly reduced. This observation led the investigators to conclude that TEA severely alters left ventricular contractility even in healthy subjects without preexisting cardiac disease. In another study of healthy subjects, left ventricular ejection and diastolic filling performance were unchanged, but a decrease in cardiac output and fractional area shortening were observed³ (Table 57-1).

        Ottesen⁴ reported that TEA does not affect oxygen consumption (V02) during exercise. However, even at moderate workloads, systemic arterial blood pressures were significantly lower with TEA than during control exercise in healthy subjects. No other changes in systemic or pulmonary circulatory parameters were observed. In another exercise study, Wattwil et al.⁵ reported that after administration of TEA, heart rate, systolic blood pressure, stroke volume, and cardiac output decreased. They also injected local anesthetic (0.5% bupivacaine) intramuscularly and observed similar cardiovascular effects, leading them to the conclusion that the changes may be due in part to systemic effects.

        Several studies have documented the effects of TEA on cardiovascular function in patients with heart disease. In a small study of 10 patients scheduled for thoracotomy, a TEA with a mean analgesic level of C7 to T5 had only minor effects on the cardiovascular system.⁶ In patients with severe coronary artery disease and unstable angina pectoris, Blomberg et al.⁷ observed that TEA relieved chest pain. It also significantly decreased heart rate, systolic arterial, and pulmonary arterial and pulmonary capillary wedge pressures without any significant changes in coronary perfusion pressure, cardiac output, stroke volume, and systemic or pulmonary vascular resistances.

        Intraoperatively, Reinhart et al.⁸ observed lower cardiac index and oxygen delivery (Qo₂) in patients receiving TEA and general anesthesia than in those receiving general anesthesia alone; V02 were similar. They also reported that the oxygen supply-demand ratio (Q02/V02) was less in the TEA group throughout the perioperative period and about 30% below baseline values during early recovery. The authors attributed the reduced adaptation of cardiac output to tissue oxygen needs during TEA to negative inotropic and chronotropic effects of sympathetic blockade. In patients on chronic ß-adrenergic blocking medication, TEA has been reported to induce a moderate decrease in mean arterial pressure and coronary perfusion pressure, but without producing clinically significant cardiovascular effects.⁹

^a p< 0.01 vs before block.

^b p< 0.05.

EDA, end-diastolic area; ESA, end-systolic area; FAC, fractional area change; PFR, peak filling rate; PER, peak ejection rate; D1/D2, ratio of peak dA/dt (change in area of left ventrical versus time) in the rapid filling phase (Dl) to the peak dA/dt in the atrial contraction phase (D2).

Reproduced, with permission, from Niimi Y, Ichinose F, Saegusa H, et al: Echocardiographic evaluation of global left ventricular function during high thoracic epidural anesthesia. J Clin Anesth 1997;9(2):118-124.

        Berendes et al.¹⁰ reported that in patients undergoing coronary artery bypass grafting (CABG) with combined TEA and general anesthesia, regional left ventricular function was significantly improved, and cardiac troponin I concentrations were reduced when compared with patients receiving general anesthesia alone (Figure 57-1). In addition, TEA reduced the concentrations of atrial and brain natriuretic peptides. The authors concluded that cardiac sympathectomy by TEA improves regional left ventricular function and reduces postoperative ischemia after CABG. In another study of CABG patients, TEA was associated with better hemodynamic stability before and after cardiopulmonary bypass when compared with general anesthesia.¹¹ In addition, TEA may provide improvement in pulmonary function, possibly because of more profound postoperative analgesia after cardiac surgery.¹²

        Cardiac function was also evaluated in patients with two- or three-vessel coronary artery disease who were treated with ß-adrenergic blocking agents. Systolic and diastolic arterial pressures, heart rate, and global and regional ejection fractions using equilibrium radionuclide angiography were measured at rest and during maximal exercise before and after TEA. During TEA exercise, systolic arterial pressure, diastolic arterial pressure, and the rate-pressure product, but not heart rate, were significantly lower when compared with control exercise. The global and anterolateral ejection fractions were significantly higher, and the regional wall motion score was significantly lower during TEA exercise than during control exercise. ST-segment depression was significantly lower during TEA exercise.¹³ Schmidt et al.¹⁴ noted that in patients with coronary artery disease, TEA induced a significant improvement in left ventricular diastolic function, whereas indices of systolic function did not change (Figures 57-2 through 57-4).

        Patients with cardiac disease are prone to hemodynamic changes during laryngoscopy and intubation, thus placing them at risk for ischemic events. TEA has been associated with stable hemodynamics and preservation of baroreflex sensitivity, suggesting withdrawal of vagal activity. Licker et al.¹⁵ reported that patients who received TEA in addition to general anesthesia had smaller increases in mean arterial pressure and heart rate during laryngoscopy and tracheal intubation than those who received general anesthesia only; this would suggest that TEA affords hemodynamic protection during these maneuvers.

Clinical Pearls

Figure 57-1. Patients’ global and regional left ventricular function and afterload. A: Preoperative and postoperative values of global left ventricular wall motion index. C: Left ventricular fractional area change (FAC). D: Left ventricular end-systolic meridional wall stress(es) as well as postoperative concentrations of cardiac troponin I in patients who received general anesthesia (GA) only or GA and high thoracic epidural anesthesia (TEA) (B). Values are given as mean (SD). Asterisks indicate P < .05. (Reproduced, with permission, from Berendes E, Schmidt C, Van Aken H, et al: Arch Surg 2003;138[12]:1283-1290.)

Management of Cardiac Disease

TEA has been used in the management of cardiac disease (Figure 57-5). Cardiac sympathetic blockade by TEA dilates stenotic coronary arteries and has been used to control pain in patients with unstable angina.¹⁶ The mechanism by which TEA reduces angina during long-term treatment is unclear. It has been reported that the improvement in symptoms probably results partly from an anesthetic effect and does not appear to be related to a change in myocardial blood flow or a reduction in stress-induced ischemia. In addition, new myocardial infarctions are not masked or missed in patients receiving TEA for symptomatic treatment of angina.¹⁷ The effects of long-term, home self-treatment with TEA on angina, quality of life, and safety were studied by Richter et al.¹⁸ Thirty-seven patients with refractory angina began treatment with TEA, using a subcutaneously tunneled epidural catheter and a bupivacaine solution. All but one of the patients improved symptomatically. The improvement was maintained throughout the treatment period (4 days to 3 years). The authors reported that the frequency of anginal attacks and nitroglycerin intake decreased, whereas the overall self-rated quality of life assessed by visual analog scale (VAS) increased.

Figure 57-2. Estimation of the myocardial performance index (MPI; Tei index). MPI is calculated from two time intervals as a-b/b. Interval a: from cessation to next onset of mitral flow. Interval b: from onset to cessation of aortic flow. Time intervals a and b are indicated in milliseconds. A typical example of measuring the MPI using Doppler ECG registration of mitral and aortic flow velocity profiles is demonstrated. For illustrative purposes, the original Doppler tracings of mitral inflow and left ventricular (LV) outflow are plotted together. ET, ejection time of LV outflow; ICT, isovolumic contraction time; IRT, isovolumic relaxation time. (Reproduced, with permission, from Schmidt C, Hinder F, Van Aken H, et al: The effect of high thoracic epidural anesthesia on systolic and diastolic left ventricular function in patients with coronary artery disease. Anesth Analg 2005;100[6]:1561 -1569.)

        Studies have looked at the number of anginal attacks and the severity of myocardial ischemia assessed by 48-hour ambulatory Holter monitoring in patients with severe, refractory unstable angina receiving TEA or standard antianginal therapy. Olausson et al.¹⁹ reported that the incidence of myocardial ischemia was lower in the TEA group (22% versus 61%; P < .05). The number ofischemic episodes per patient was 1.0 ± 0.6 in the TEA group and 3.6 ± 0.9 in the control group (P < .05), and the episode duration per patient was 4.1 ± 2.5 minutes and 19.7 ± 6.2 minutes in the TEA and the control groups, respectively ( P < .05).

Cardiac Surgery

Coronary Artery Bypass Grafting

As an anesthetic for CABG, TEA offers thoracic and cardiac sympathectomy, attenuation of the stress response, analgesia for surgery, and postoperative analgesia, which may improve outcome after CABG. One review suggests that for patients undergoing CABG surgery, the risk:benefit ratio is in favor of epidural and spinal anesthesia, provided no specific contraindications exist and the guidelines for the use of regional techniques in cardiac surgery are followed.²⁰ Patients managed with regional anesthetic techniques seem to benefit from superior postoperative analgesia, shorter postoperative ventilation, reduced incidence of supraventricular arrhythmias, and lower rates of perioperative myocardial infarction. The results of this particular analysis suggest that for each episode of neurologic complication that might occur, 20 myocardial infarctions and 76 episodes of atrial fibrillation would be prevented. Thus, regional anesthesia and analgesia would be considered an effective strategy that improves perioperative morbidity.

        As an adjunct to general anesthesia, TEA can be useful in off-pump CABG. Salvi et al.²¹ reported on 106 patients receiving TEA combined with sevoflurane general anesthesia. The mean time to extubation was 4.6 ± 2.9 hours. VAS scores for pain during the first 24-hour period were less than 2 in all patients. The average intensive care unit (ICU) stay was 1.5 ± 0.8 days. Incidences of perioperative myocardial infarction, myocardial ischemia, and atrial fibrillation were 2.8%, 7.5%, and 10.6%, respectively. Two patients died—one from multiorgan failure and the other from myocardial infarction. Heart rate, mean arterial pressure, cardiac index, and systemic vascular resistance were not affected by TEA alone. Mean arterial pressure and cardiac index decreased ( P < .05) when general anesthesia was induced and remained stable thereafter. Neither heart rate nor systemic vascular resistance changed from baseline during the operation. The authors concluded that thoracic epidural block as an adjunct to general anesthesia is a feasible technique in off-pump CABG. It induces intense postoperative analgesia and does not compromise central hemodynamics.

Figure 57-3. Estimates of left ventricular preload (EDA; end-diastolic cross-sectional area [cm²]), afterload (a_m(_es); endsystolic meridional wall stress [10³/dynes/cm²)] global systolic function (fractional area change [FAC] [%]), and global diastolic function (flow propagation velocity [V_p] [cm/s]). Data are represented as scatterplots. Mean values are superimposed as horizontal lines and SD as vertical lines. The P values denote comparisons before (1) and after (2) high thoracic epidural anesthesia (paired t test). (Reproduced, with permission, from Schmidt C, Hinder F, Van Aken H, et al: The effect of high thoracic epidural anesthesia on systolic and diastolic left ventricular function in patients with coronary artery disease. Anesth Analg 2005;100[6]:1561-1569.)

        Kessler et al.²² compared TEA alone (ropivacaine plus sufentanil, n = 30), TEA combined with general anesthesia (n = 30), and general anesthesia alone in patients scheduled for off-pump CABG surgery. The general anesthetic consisted of propofol, remifentanil, and cisatracurium. Intraoperative heart rate decreased significantly with TEA alone or in combination with general anesthesia. None of the patients with TEA alone was admitted to the ICU; all were monitored in the intermediate care unit for an average of 6 hours postoperatively and were allowed to eat and drink as desired on admission. Postoperative pain scores were lower in both groups with TEA. There were no differences among groups in overall patient satisfaction. The authors concluded that general anesthesia + TEA appeared to be the most comprehensive anesthetic, allowing for revascularization of any coronary artery and providing good hemodynamic stability and reliable postoperative pain relief.

Figure 57-4. Comparison of the myocardial performance index (MPI), the ratio of isovolumic relaxation time versus ejection time (IRT/ET), and the ratio of isovolumic contraction time versus ejection time (ICT/ET) before (1) and after (2) high thoracic epidural anesthesia (HTEA). The boxes extend from the 25th to the 75th percentile. The error bars extend down to the smallest value and up to the largest. The lines at the middle of the boxes are the medians. MPI and IRT/ET, but not ICT/ET, changed significantly after HTEA (paired t test). (Reproduced, with permission, from Schmidt C, Hinder F, Van Aken H, et al: The effect of high thoracic epidural anesthesia on systolic and diastolic left ventricular function in patients with coronary artery disease. Anesth Analg 2005;100[6]:1561 -1569.)

Figure 57-5. The Epiport epidural catheter with subcutaneous access port at T1. (Reproduced, with permission, from Gramling-Babb PM, Zile MR, Reeves ST: Preliminary report on high thoracic epidural analgesia: Relationship between its therapeutic effects and myocardial blood flow as assessed by stress thallium distribution. J Cardiothorac Vase Anesth 2000;14[6]:657-661.)

        Stritesky et al.²³ reported on 129 patients undergoing cardiac surgery awake with spontaneous ventilation using TEA for anesthesia. Ninety patients underwent on-pump surgery and 39 underwent off-pump surgery. A thoracic epidural block was placed 1 hour before skin incision at the T2-T4 level. Forty-two cases had aortic valve replacement, 32 patients underwent on-pump CABG, 12 had off-pump CABG, 12 had mitral valve replacement, 27 underwent sternal wound reexploration, and 4 had combined procedures. There were 10 conversions to general anesthesia and no deaths. Mean duration of stay in the ICU was 7.2 hours; in-hospital stay 5.1 days. Low cardiac output syndrome, stroke, renal insufficiency, and pulmonary dysfunction were not observed in patients who underwent TEA. Less postoperative pain was also demonstrated.

        The authors felt that TEA provided rapid recovery and early outpatient care of patients after cardiac surgery and that TEA would be beneficial for patients with preoperative pulmonary dysfunction.

        Several other studies have shown TEA to be effective for CABG surgery in the awake patient^24–26 (Figure 57-6). Kessler et al.²⁷ reported on the feasibility and complications of TEA as the sole anesthetic in 20 patients undergoing beating-heart arterial revascularization. Minimally invasive direct coronary CABG (MIDCAB) via partial lower sternotomy was used in 10 patients with single-vessel disease, whereas complete median sternotomy with off-pump coronary artery bypass grafting (OPCAB) was chosen for 10 patients with multivessel disease. An epidural catheter was inserted at the Tl-2 or T2-3 level. An epidural infusion of ropivacaine 0.5% and sufentanil 1.66 mcg/mL was started to establish anesthetic levels at C5-6 for OPCAB and at Tl-2 for MIDCAB. Nine OPCAB and eight MIDCAB procedures were completed while the patients were awake and spontaneously breathing during the entire procedure. Three patients required intraoperative conversion to GA because of surgical pneumothorax (OPCAB), insufficient anesthesia, or phrenic nerve palsy (both MIDCAB).

Figure 57-6. Coronary artery bypass grafting through a lower ministernotomy while the patient is awake. (Reproduced, with permission, from Aybek T, Kessler P, Dogan S, et al: Awake coronary artery bypass grafting: Utopia or reality? Ann Thorac Surg 2003;75[4]:1165-1170.)

        In both groups, the heart rate decreased significantly ( P < .05) by 10-15% during the procedure. Compared with baseline, mean arterial blood pressure was decreased significantly only during coronary anastomosis. Paco2 increased from 42 ± 2 mm Hg to 46 ± 7 mm Hg (P < .05) throughout the perioperative course during OPCAB, whereas it remained almost unaltered during MIDCAB procedures. All patients rated TEA as “good” or “excellent” and reported a high degree of satisfaction with the procedure.

        Anderson et al.²⁸ found similar results when studying the use of TEA for awake cardiac surgery. He reported on a total of 10 operations including 7 MIDCAB, 2 transmyocardial revascularizations (TMR) and 1 MIDCAB/TMR hybrid. The mean preoperative forced expiratory volume for 1 second (FEVj) was 1.9 liters. Significant intraoperative hypoxia or hypercarbia was not seen. One patient required intubation during the procedure for restlessness not associated with hypoxia. Two others required brief periods of assisted ventilation. All procedures were completed without incident. The mean operating time and length of stay were 70 minutes and 4.7 days, respectively. Postoperative pain control and patient satisfaction were excellent.

        Although ischemic damage to the myocardium is inevitable during CABG surgery, the extent of the damage may be influenced by the anesthetic technique used. Barrington et al.²⁹ reported on the effect of TEA on the release of troponin I, time to tracheal extubation, and analgesia during elective CABG surgery. One hundred twenty patients were randomized to general anesthesia or general anesthesia plus TEA. The general anesthesia group received fentanyl (7-15 mcg/kg) and a morphine infusion. The TEA group received fentanyl (5-7 mcg/kg) and an epidural infusion of ropivacaine 0.2% and fentanyl 2 mcg/mL until postoperative day 3. Researchers found no differences in troponin I levels between the study groups. The time to tracheal extubation in the TEA group was 15 minutes (range 10-20) compared with 430 minutes (range 284-590) in the general anesthesia group (P < .0001). Analgesia was improved in the TEA group compared with the general anesthesia group. Mean arterial blood pressure and systemic vascular resistance in the ICU were lower in the TEA group. They concluded that TEA for CABG had no effect on troponin release but improved postoperative analgesia and was associated with a reduced time to extubation (Table 57-2; Figure 57-7). Kendall et al.³⁰ conducted a prospective, randomized study to determine the baseline values of troponin T release after off-pump CABG in 30 patients randomly allocated to receive propofol, isoflurane, or isoflurane plus TEA. All other treatments were standardized. They found that mean troponin T levels at 24 hours were not significantly different between the groups (P = .41).

GA, general anesthesia; HTEA, high thoracic epidural anesthesia; IQR, interquartile range; troponin 112 h and 24 h, samples are taken 12 and 24 hours after release of aortic cross-clamp; Q wave, new persistent Q wave on day 5.

Reproduced, with permission, from Barrington MJ, Kluger R, Watson R, et al: Epidural anesthesia for coronary artery bypass surgery compared with general anesthesia alone does not reduce biochemical markers of myocardial damage. Anesth Analg 2005;100(4):921-928.

Figure 57-7. Kaplan-Meier survival plot for time to extubation. • = high thoracic epidural anesthesia (HTEA) group; + = general anesthesia (GA) group (P < .0001). (Reproduced, with permission, from Barrington MJ, Kluger R, Watson R, et al: Epidural anesthesia for coronary artery bypass surgery compared with general anesthesia alone does not reduce biochemical markers of myocardial damage. Anesth Analg 2005;100[4]:921 -928.)

        Loick et al.³¹ investigated the effects of general anesthesia with TEA or with intravenous clonidine on the stress response and incidence of myocardial ischemia in patients undergoing CABG surgery. Seventy patients scheduled for elective CABG surgery received general anesthesia with sufentanil and propofol. In 25 patients, TEA was induced before general anesthesia and continued during the entire study period. Another 24 patients received intravenous clonidine as a bolus of 4 mcg/kg before the induction of general anesthesia. Clonidine was then infused at a rate of 1 mcg/kg/h during surgery and at 0.2-0.5 mcg/kg/h postoperatively. The control group consisted of 21 patients who underwent general anesthesia as performed routinely Hemodynamics, plasma epinephrine and norepinephrine, cortisol, troponin T, and other cardiac enzymes were measured pre- and postoperatively Both TEA and clonidine reduced the postoperative heart rate compared with the control group without jeopardizing cardiac output or perfusion pressure. Plasma epinephrine increased perioperatively in all groups but was significantly lower in the TEA group. Neither TEA nor clonidine affected the increase in plasma cortisol. The release of troponin T was attenuated by TEA. New ST-segment elevation or depression occurred in more than 70% of the control patients but only in 40% of the clonidine group and in 50% of the TEA group. The investigators concluded that TEA, but not intravenous clonidine, combined with general anesthesia for CABG demonstrated a beneficial effect on the perioperative stress response and decreased postoperative myocardial ischemia.

        Liu et al.³² recently conducted a meta-analysis of 15 trials that studied the effects of perioperative central neuraxial analgesia on outcome after CABG. The total number of patients was 1178. According to the analysis, TEA does not affect the incidences of mortality (0.7% TEA vs 0.3% general anesthesia) or myocardial infarction (2.3% TEA vs 3.4% general anesthesia). However, TEA does significantly reduce the risk of arrhythmias (odds ratio 0.52), pulmonary complications (odds ratio 0.41), and time to tracheal extubation (by 4.5 hours). TEA reduces analog pain scores at rest by 7.8 mm and with activity by 11.6 mm. The authors concluded that there were no differences in the rates of mortality or myocardial infarction after CABG surgery with central neuraxial analgesia. More rapid tracheal extubation, decreased pulmonary complications and cardiac arrhythmias, and reduced pain scores were, however, benefits of TEA.

        Fillinger et al.³³ conducted a prospective, randomized, nonblinded clinical trial assessing the effects of anesthetic on recovery from cardiac surgery. Sixty patients scheduled for elective cardiac surgery with cardiopulmonary bypass were randomly assigned to 1 of 2 study groups. One group was to receive general anesthesia during surgery and intravenous opioid analgesia after surgery, whereas the second group received TEA combined with general anesthesia during surgery and epidural analgesia for the first 24 postoperative hours. They found no statistically significant differences in time to tracheal extubation, duration of postoperative ICU stay, duration of postoperative hospitalization, pain control, urinary free cortisol, cardiopulmonary complication rate, or total hospital charges.

        The most feared complication of TEA is epidural hematoma. Studies have found that, in the setting of cardiac surgery, following a set of standard safety measures averts the occurrence of symptomatic epidural hematomas. These measures consist of preoperative coagulation tests including aPTT, platelet count, and prothrombin time and the cessation of antiplatelet drugs before surgery.^34,35 Scott et al.³⁶ conducted a prospective, randomized, controlled study of the incidence of major organ complications in 420 patients undergoing routine CABG with or without TEA. All patients received a standardized general anesthetic. Patients in the TEA group received TEA for 96 hours. Patients in the general anesthesia group received narcotic analgesia for 72 hours. Both groups received supplementary oral analgesia. New supraventricular arrhythmias occurred in 21 of 206 patients (10.2%) in the TEA group compared with 45 of 202 patients (22.3%) in the general anesthesia group (P = .0012). Pulmonary function (maximal inspiratory lung volume) was better in the TEA group (P < .0001). Extubation was achieved earlier ( P < .0001) and with significantly fewer lower respiratory tract infections in the TEA group (TEA = 31 of 206, general anesthesia = 59 of202; P = .0007). Significantly fewer patients had acute confusion (general anesthesia = 11 of 202, TEA = 3 of 206; P = .031) and acute renal failure (general anesthesia = 14 of202, TEA —4 of206; P = .016) in the TEA group. The incidence of stroke was insignificantly less in the TEA group (general anesthesia = 6 of 202, TEA = 2 of 206; P = .17). No neurologic complications were associated with TEA. The researchers concluded that continuous TEA significantly improved the quality of recovery after CABG surgery compared with general anesthesia and conventional narcotic analgesia.

        Turfrey et al.³⁷ reported similar results after performing a retrospective analysis of the perioperative course of 218 patients who underwent routine CABG. All patients received a standardized general anesthesia, using target-controlled infusions of alfentanil and propofol. One hundred patients also received TEA with bupivacaine and clonidine, started before surgery and continued for 5 days after surgery. The remaining 118 patients received a target-controlled infusion of alfentanil for analgesia for the first 24 hours after surgery, followed by intravenous patient-controlled morphine analgesia for a further 48 hours. New arrhythmias requiring treatment occurred in 18% of the TEA group of patients compared with 32% of the general anesthesia group (P = .02). There was also a trend toward a reduced incidence of respiratory complications in the TEA group. The time to tracheal extubation was decreased in the TEA group, with 21% of the patients being extubated immediately after surgery compared with 2% in the general anesthesia group (P < .001). No serious neurologic problems resulted from the use of TEA.

Valvular Surgery

Although most studies on the use of TEA in cardiac surgery have focused on CABG, a few investigations and case reports describe its use in valvular surgery. Hemmerling et al.³⁸ have reported on the feasibility and hemodynamic stability of immediate extubation after simple or combined aortic valve surgery using TEA and general anesthesia. Thirty patients with an ejection fraction of more than 30% undergoing aortic valve surgery were studied prospectively. After initiation of TEA, general anesthesia was induced with fentanyl 2-4 mcg/kg, propofol 1-2 mg/kg, and endotracheal intubation was facilitated by rocuronium. Anesthesia was maintained with sevoflurane titrated according to bispectral index (target = 50). Perioperative analgesia was provided by TEA (bupivacaine 0.125% at 6-14 mL/h). Patients underwent simple aortic valve surgery (n = 17) or combined aortic valve surgery (n = 13) with additional CABG (n = 8), replacement of the ascending aorta (Bentall procedure; n = 4), and repair of open foramen ovale (n = 1). All 30 patients were extubated within 15 minutes after surgery at 36.5°C. There was no need for reintubation. Pain scores were low immediately after surgery and at 6, 24, and 48 hours after surgery. During and up to 6 hours after surgery, there was no significant hemodynamic change due to TEA. Fifteen of the 30 patients needed temporary pacemaker activation. There were no complications related to TEA. The authors concluded that immediate extubation is feasible after aortic valve surgery with TEA and maintenance of hemodynamic stability throughout surgery.

        Klokocovnik et al.³⁹ describe a patient who underwent aortic valve replacement through a ministernotomy while awake under TEA. The procedure was not converted to general anesthesia or to a conventional operation and was performed without adverse incidents. The patient was discharged from the hospital on the second postoperative day. There were no complications within 30 days after surgery. Kozian et al.⁴⁰ report on a tricuspid valve replacement without any adverse events using TEA and balanced general anesthesia.

Congenital Surgery

The effects of combined TEA and general anesthesia on hemodynamic and respiratory variables have been reported in children undergoing cardiac heart surgery. Slin’ko et al.⁴¹ report that in 55 patients age 1-14 years, TEA was used in combination with oxygen-air-halothane anesthesia. In one group, lidocaine and fentanyl were used for TEA, and in another clonidine and lidocaine. In a control group, standard intravenous fentanyl-diazepam anesthesia was combined with oxygen-air-halothane anesthesia. In the clonidine-lidocaine group, the endocrine stress response was decreased in comparison with other groups, even without narcotics. Hemodynamics remained stable even in patients with NYHA (New York Heart Association) class III-IV heart disease. These same investigators also report that TEA has been found to be safe and effective for postoperative pain in children after heart surgery.⁴² In one study, 40 children received epidural analgesia after open-heart surgery. Lidocaine was injected in a dose of 1.5-2 mg/kg every 1.5-2 hours. Controls (n = 16) received intravenous fentanyl 4? diazepam analgesia. Respiratory response and awakening were significantly earlier ( P < .001) in the epidural group. Cooperation with nurses was much better in this group, too. No side effects were observed in the epidural group.

        Peterson et al.⁴³ report on a retrospective study describing the results of the use of regional anesthesia in 220 pediatric cardiac operations. They indicate that tracheal extubation in the operating room could be achieved for 89% of the patients. Ninety-five percent of the patients had pain scores less than or equal to 4.0 at all intervals postoperatively. Adverse effects of regional anesthesia included emesis, pruritus, urinary retention, postoperative transient paresthesia, and respiratory depression (Table 57-3). The incidence of peridural hematoma was zero. The rate of adverse effects was lower using the TEA approach compared with various caudal, lumbar epidural, and spinal approaches. Hospital stay was not prolonged because of regional anesthetic complications. In this study, regional anesthesia was found to be safe and effective in the management of pediatric patients undergoing cardiac surgery.

        Hammer et al.⁴⁴ evaluated whether spinal anesthesia or TEA in combination with general anesthesia was associated with circulatory stability, satisfactory postoperative sedation/analgesia, and a low incidence of adverse effects. They found no significant differences in the incidence of clinically significant changes in vital signs, oxygen desaturation, hypercarbia, or vomiting when comparing TEA with spinal anesthesia for children undergoing cardiac surgery.

L/C SSE, lumbar/caudal single-shot epidural; L/C Cath, lumbar/caudal catheter epidural; Intrath, intrathecal single-shot; Thorac Cath, thoracic catheter epidural; CNS, central nervous system..

Reproduced, with permission, from Peterson KL, DeCampli WM, Pike NA, et al: A report of two hundred twenty cases of regional anesthesia in pediatric cardiac surgery. Anesth Analg 2000;90(5):1014-1019.

Noncardiac Surgery in Patients with Cardiovascular Disease

When TEA is used for major vascuar surgery, it is reported to provide more hemodynamic stability and better pain control than general anesthesia or monitored anesthesia care with local anesthesia.⁴⁵ TEA has been found safe and effective for endovascular aortic aneurysm repair, especially in patients with severe coexisting diseases. In addition, TEA minimizes sedation and postoperative analgesic requirements, decreases cardiopulmonary complications, and decreases overall hospital stay, thereby reducing cost.

        Bonnet et al.⁴⁶ investigated the hemodynamic consequences of abdominal aortic surgery with infrarenal crossclamping in 21 patients randomized to one of two groups. In group I (n = 11), neuroleptanesthesia was used, whereas group II (n = 10) received TEA at the T8-T9 level. In all patients, hemodynamic measurements were performed using pulmonary artery catheters. The use of TEA was characterized by greater hemodynamic stability during surgery. Patients in the neuroleptanesthesia group experienced significant lability of blood pressure, heart rate, and cardiac index.

        Her et al.⁴⁷ compared intraoperative hemodynamic variables and postoperative morbidity between a group of patients undergoing abdominal aortic surgery—one with combined TEA and general anesthesia (n = 30) and one with general anesthesia alone (n = 19). Patients in the combined group were given epidural bupivacaine intraoperatively and epidural morphine postoperatively. After cross-clamping of the aorta, cardiac index and pulmonary capillary wedge pressure did not change in the combined group, whereas cardiac index decreased (mean change, 0.30 L/min/m²; P = .006) and pulmonary capillary wedge pressure increased (mean change I mm Hg; P = .007) in the group with general anesthesia alone. After unclamping of the aorta, cardiac index increased in both groups (mean change, 0.26 L/min/m², P = .002 and 0.30 L/min/m² P = .001, respectively). Postoperatively, the necessity for ventilatory support and the incidence of respiratory failure were lower in the combined group than in the general anesthesia alone group (P = .0002 and P = .018, respectively). In addition, vasodilator therapy was required less frequently in the combined group (P = .002). Duration of ICU stay was shorter in the combined group (2.7 days vs 3.8 days; P = .003). The authors concluded that for infrarenal abdominal aortic surgery, combined TEA and general anesthesia is associated with more stable intraoperative hemodynamics and significantly less postoperative morbidity than general anesthesia alone.

        Different results, however, were obtained by Garnett et al.,⁴⁸ who studied the incidence of perioperative myocardial ischemia in patients undergoing elective aortic surgery. Patients were randomly assigned to one of two groups. One group (n = 48) received combined general anesthesia and epidural anesthesia and postoperative epidural analgesia for 48 hours; the other group (n = 51) received general anesthesia followed by postoperative intravenous analgesia. The authors reported that myocardial ischemia was common because it occurred in 55% of patients. In the hospital, preoperative ischemia was uncommon (combined = 8; general anesthesia = 3). Ischemic events were common intraoperatively (combined = 25; general anesthesia = 18), with mesenteric traction producing the largest number of events (combined = II; general anesthesia =11). Postoperative ischemia was most common on the day of surgery. Termination of epidural analgesia produced rebound ischemia (60 events in 9 patients). The authors concluded that combined general anesthesia and epidural anesthesia and postoperative epidural analgesia do not reduce the incidence of myocardial ischemia or morbidity compared with general anesthesia and postoperative intravenous analgesia.

        Norris et al.⁴⁹ studied patient outcomes in 168 patients undergoing surgery of the abdominal aorta using different types of anesthesia. Patients were randomly assigned to receive either TEA combined with general anesthesia or general anesthesia alone intraoperatively and either intravenous or epidural patient-controlled analgesia (PCA) postoperatively (four treatment groups). PCA was continued for at least 72 hours. Length of stay and direct medical costs for patients surviving to discharge were similar among the four treatment groups. Postoperative outcomes were also similar among the groups with respect to death, myocardial infarction, myocardial ischemia, reoperation, pneumonia, and renal failure. Postoperative pain scores were the same for the four groups, but epidural PCA was associated with a significantly shorter time to extubation (P = .002). Times to ICU discharge, ward admission, first bowel sounds, first flatus, tolerating clear liquids, tolerating regular diet, and independent ambulation were also equivalent for the four groups. The authors concluded that in patients undergoing surgery of the abdominal aorta, TEA combined with general anesthesia and followed by either intravenous or epidural PCA, offers no major advantage or disadvantage when compared with general anesthesia alone followed by either intravenous or epidural PCA.

        Davies et al.⁵⁰ prospectively studied intraoperative hemodynamics and outcomes in 50 patients undergoing elective abdominal aortic surgery who were randomized to receive either combined epidural (T9-T10 level) and general anesthesia and postoperative epidural analgesia or general anesthesia and postoperative intravenous morphine infusion. The use of intraoperative vasopressors was significantly higher in the combined group (P < .01), but the use of intravenous glyceryl trinitrate was significantly lower (P < .01). No significant difference was found between groups in regard to blood loss, volume replacement, and the number of patients requiring postoperative ventilation. Two patients in the combined group died postoperatively compared with one in the general anesthesia group (nonsignificant). There was no significant difference between groups in the total number or type of postoperative complications. The authors concluded that combined epidural anesthesia with general anesthesia altered intraoperative cardiovascular management but did not affect postoperative outcome.

        Gelman et al.⁵¹ studied the effect of TEA on the cardiovascular function of morbidly obese patients undergoing gastric bypass surgery. Patients were given general anesthesia alone or a combination of TEA and general anesthesia. Circulatory function was measured and calculated using radial artery cannulation and pulmonary artery catheterization with pulmonary artery thermodilution catheters. During surgery, the TEA group demonstrated greater decreases in cardiac index, left and right ventricular stroke work, systolic blood pressure-heart rate product, arteriovenous oxygen content difference, oxygen consumption, and intrapulmonary shunt compared with the general anesthesia group. Postoperatively, epidural analgesia was associated with decreases in left ventricular stroke work, systolic pressure- heart rate product, arteriovenous oxygen content differences, and oxygen consumption compared with values observed when patients experienced pain. Morphine given for relief of postoperative pain was not associated with significant changes in cardiovascular function. The authors concluded that continuous TEA used for upper abdominal surgery in morbidly obese patients benefits intraoperative cardiovascular function, as reflected by a decrease in left ventricular stroke work, and postoperatively by relief of pain.

Acute Pain Management

In patients with cardiac disease undergoing cardiac surgery, good pain management is an important goal to improve outcomes and reduce postoperative complications. The value of TEA in this setting has been studied extensively. Royse et al.⁵² studied 80 patients who were randomized to TEA or intravenous morphine analgesia for postoperative pain control after CABG with cardiopulmonary bypass. A thoracic epidural catheter was inserted the night before surgery at either the T1 – T2 or T2-T3 level. Eight milliliters of 0.5% ropivacaine with 20 meg fentanyl was administered before induction of anesthesia. Ropivacaine 0.2% with 2 mcg/mL fentanyl was then infused at a rate of 5-14 mL/h to attain a sensory block of T1 to T10. Pain was measured using a VAS scale from 0 to 10. Psychological morbidity, intraoperative hemodynamics, ventricular function, lung function, and physiotherapy cooperation were also assessed. On the third postoperative day, TEA and morphine were stopped, and only oral medications were used. Acetaminophen, indomethacin, and tramadol were allowed as supplemental analgesics in both groups. Pain scores were significantly less with TEA on postoperative days 1 and 2 at rest and with coughing. When TEA and morphine were stopped on day 3, there were no significant differences. Secondary endpoints of postoperative depression and posttraumatic stress subscales of the Minnesota Multiphasic Personality Inventory were lower with TEA. In addition, extubation occurred earlier with TEA (2.6 vs 5.4 hours; P < .001). TEA showed improved physiotherapy cooperation ( P < .001),arterial oxygen tension (P = .041), and peak expiratory flow rate (P = .001). Mean arterial pressure was lower with TEA (P = .036); otherwise, no differences were found in intraoperative hemodynamics or ventricular function.

        Liem et al.⁵³ studied the effects of intraoperative and postoperative epidural pain management during and after CABG on the recovery time, postoperative pulmonary and cardiac parameters, VAS scores, and sedation scores. They compared the findings with those of patients anesthetized with general anesthesia whose postoperative pain was relieved with intermittent intravenous administration of nicomor- phine. Fifty-four patients were studied postoperatively after uncomplicated CABG surgery. In the TEA group (n = 27), intraoperative analgesia was based on TEA in combination with general anesthesia. In the general anesthesia group (n = 27), intravenous anesthesia with high-dose sufentanil and midazolam was used. Postoperative pain management in the general anesthesia group consisted of intermittent intravenous administration of nicomorphine 0.1 mg/kg every 6 hours, whereas in the TEA group patients received a continuous high TEA with 0.125% bupivacaine plus sufentanil. Patients in the TEA group awakened earlier (148 minutes vs 335 minutes), resumed spontaneous respiration earlier (326 minutes vs 982 minutes), and were extubated earlier (463 minutes vs 1140 minutes). VAS scores, sedation scores, and postoperative Pao2 were significantly (P < .01) better in the TEA group. The incidence of tachycardia ( 15 vs 2 patients) and postoperative myocardial ischemia ( 12 vs 4 patients) was higher in the general anesthesia group. The authors concluded that intraoperative and postoperative pain treatment with epidurally administered bupivacaine plus sufentanil improved the recoverytime, as well as pulmonary and cardiac outcomes after CABG, when compared with intravenous postoperative pain treatment after intraoperative general anesthesia with sufentanil and midazolam.

        Hemmerling et al.⁵⁴ studied 100 consecutive patients undergoing OPCAB surgery to examine the feasibility of immediate extubation after using opioid-based analgesia or TEA and compare postoperative analgesia between continuous TEA versus PCA. Perioperative analgesia was provided by TEA (n = 63) using bupivacaine 0.125% at a continuous rate of 8-14 mL/h and repetitive boluses of bupivacaine 0.25% during surgery. In the other group (n = 37), perioperative analgesia was achieved by intravenous fentanyl boluses (up to 15 mcg/kg) and remifentanil 0.1-0.2 mcg/kg/min, followed by morphine PCA after surgery. Ninety-five patients were extubated within 25 minutes after surgery (TEA n = 62; PCA n = 33). Five patients were not extubated immediately because their core temperature was lower than 35^oC. One patient was reintubated because of agitation (TEA group); one was reintubated because of severe pain and morphineinduced respiratory depression (PCA group). Pain scores were generally low after surgery, with pain scores in the TEA group being significantly lower immediately, at 6 hours, 24 hours, and 48 hours after surgery (P < .05) (Figure 57-8). The authors concluded that immediate extubation is possible after OPCAB surgery using either opioid-based analgesia or TEA, but TEA provides significantly lower pain scores after surgery compared with morphine PCA.

        However, when Bois et al.⁵⁵ studied 124 patients to assess the role of postoperative analgesia on myocardial ischemia after aortic surgery using intravenous PCA or TEA, different results were obtained. In the PCA group, a bolus of morphine, 0.05 mg/kg, was given, followed by 0.02 mg/kg of morphine on demand every 10 minutes. Bupivacaine 0.125% and fentanyl 10 mcg/mL were used in the TEA group. Analgesics were titrated to maintain a VAS score ≤ 3. The overall incidence of myocardial ischemia was 18.4-18.2% for TEA and 18.6% for PCA (P = not significant). There were no differences between the groups in the total duration of ischemia per patient (22.2 ± 119.8 minutes for TEA and 20.5 ± 99 minutes for PCA) and the number of episodes per patient (0.69 ± 2.1 for TEA and 1.2 ± 4.9 for PCA). Twenty-three patients had an adverse cardiac outcome, but there were no differences between the groups. Although the postoperative pain control was superior with TEA, its use did not result in a lower incidence of early myocardial ischemia when compared with intravenous PCA with morphine.

Figure 57-8. Mean postoperative pain scores at rest by group (PCA, black; TEA, white) and time (the highest pain score immediately after surgery and within 6, 24, and 48 hours after surgery). Data are presented as means ± standard deviation. PCA, patientcontrolled analgesia with morphine; TEA, high thoracic epidural analgesia; P < .05. (Reproduced, with permission, from Hemmerling TM, Prieto I, Choiniere JL, et al: Ultra-fast-track anesthesia in off-pump coronary artery bypass grafting: A prospective audit comparing opioid-based anesthesia vs thoracic epidural-based anesthesia. Can J Anaesth 2004;51 [2]:163-168.)

        In patients who underwent CABG, a comparative audit of the use of TEA versus intravenous opioids for postoperative pain control showed no significant differences in the frequency or intensity of persistent pain (defined as pain still present 2 or more months after surgery).⁵⁶ Similarly in patients undergoing cardiac valve replacement, TEA was shown to provide excellent analgesia in the peri- and postoperative period, but did not offer a protective effect on chronic poststernotomy pain.⁵⁷

        LUMBAR EPIDURAL ANESTHESIA

Physiologic Effects on the Cardiovascular System

The influence of lumbar epidural anesthesia (LEA) without cardiac sympathectomy on global and regional left ventricular function was investigated before surgery in healthy subjects and in patients suffering from stable mild effort-related angina.⁵⁸ In both groups, epidural blockade was performed with 10 mL of 0.5% bupivacaine. Radionuclide angiography was used to determine cardiac output, left ventricular ejection fraction, and end-systolic and end-diastolic volumes and to analyze left ventricular wall motion. Throughout the procedure, patients with a history of angina exhibited neither chest pain nor ECG evidence of myocardial ischemia. At control, left ventricular ejection fraction and systolic pressurevolume ratio were lower in the patients with angina. These patients also had evidence of regional left ventricular dysfunction. Epidural blockade without volume loading resulted in slight improvements in left ventricular ejection fraction and regional function. Such changes were not observed in normal patients. After volume loading, the improvements in ventricular function subsided. These observations led the authors to conclude that LEA may improve global and regional ventricular function in patients with angina provided that volume loading is limited.

        Another study reported that LEA enhances cardiac vagal tone mainly through a decrease in venous return.⁵⁹ In hypertensive patients, LEA has been shown to cause decreases in mean arterial pressure, with associated decreases in systemic vascular resistance and cardiac output.⁶⁰

Clinical Pearls

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Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Stimulating Catheters. Ultrasound-Assisted Nerve Blocks in Adults. Cutaneous Blocks for the Upper Extremity. Cervical Plexus Block.