Wayne H. Bellows

The Risk of Myocardial Ischemia in Patients Receiving Desflurane versus Sufentanil Anesthesia for Coronary Artery Bypass Graft Surgery

Desflurane, a coronary vasodilator, may induce myocardial ischemia in patients with coronary artery disease. To determine whether desflurane is safe to administer to the at-risk patient population (with known coronary artery disease), we compared the incidence and characteristics of perioperative myocardial ischemia in 200 patients undergoing coronary artery bypass graft (CABG) surgery randomly assigned to receive desflurane (thiopental adjuvant) versus sufentanil anesthesia. Under conditions of hemodynamic control, perioperative ischemia was assessed using continuous echocardiography (precordial: during induction; transesophageal: during surgery) and Holter electrocardiography (ECG); hemodynamics (including pulmonary artery pressure) were measured continuously. Hemodynamic results: During induction, no significant changes in hemodynamics occurred in the sufentanil group, while in the desflurane group, heart rate, systemic and pulmonary arterial pressure increased and stroke volume decreased significantly. During the intraoperative period, the incidence of hemodynamic variations was low in both anesthetic groups; however, the prebypass incidence of tachycardia (greater than 120% of preoperative baseline heart rate) was greater in the desflurane group (4 +/- 7% of total time monitored) than in the sufentanil group (1 +/- 6%) (P = 0.0003). Similarly, the incidence of prebypass hypotension (less than 80% of preoperative baseline systolic arterial blood pressure) was greater in the desflurane group (21 +/- 14%) than in the sufentanil group (15 +/- 16%) (P = 0.01). ECG results: Preoperatively, 15% (28/191) of patients developed ECG ischemia, with no difference between patients who received desflurane, 13% (12/96) or sufentanil, 16% (16/95) (P = 0.6). During anesthetic induction, 9% (9/99) of patients who received desflurane developed ECG ischemia, compared with 0% (0/98) who received sufentanil (P = 0.007). During the prebypass period, 5% (10/197) of patients developed ECG ischemia, with no difference between patients who received desflurane, 7% (7/99) or sufentanil, 3% (3/98) (P = 0.3). Postbypass, 12% (24/194) of patients developed ECG ischemic changes, with no difference between patients who received desflurane, 13% (13/97) or sufentanil, 11% (11/96) (P = 0.9). Echocardiographic results: The incidence of precordial echocardiographic ischemia during anesthetic induction was 13% (5/39) in the desflurane group versus 0% (0/29) in the sufentanil group (P = 0.1). Moderate to severe transesophageal echocardiographic (TEE) ischemic episodes occurred in 12% (21/175) of patients during prebypass, with no significant difference between the desflurane group, 16% (15/91) and the sufentanil group, 7% (6/84) (P = 0.09). TEE ischemic episodes occurred in 27% (49/178) of patients during the postbypass period, with no difference between the desflurane, 29% (27/92) and sufentanil, 25% (22/86) groups (P = 0.7).(ABSTRACT TRUNCATED AT 400 WORDS)

Increases in P-wave dispersion predict postoperative atrial fibrillation after coronary artery bypass graft surgery.

Atrial fibrillation (AF) is a common complication after coronary artery bypass graft (CABG) surgery. In this study we examined the effect of surgery on atrial electrophysiology as measured by P-wave characteristics and to determine the potential predictive value of P-wave characteristics on the incidences of postoperative AF in patients undergoing CABG surgery. Patients undergoing elective CABG surgery were monitored by continuous electrocardiogram (ECG) telemetry during the in-hospital period until discharge for the occurrence of postoperative AF. Differences in P-wave characteristics (P-wave duration, amplitude, axis, dispersion, PR interval, segment depression, and dispersion) were compared between the pre- and postoperative 12-lead ECG measurements, and also between patients with and without postoperative AF. The association of postoperative AF and potential clinical predictors and P-wave characteristics were determined by multivariate logistic regression. Postoperative AF occurred in 81 (27%) of 300 patients. Univariate analysis showed that patients who subsequently developed postoperative AF compared with those without AF were significantly older (mean age 68 ± 8 versus 63 ± 10 yr, P < 0.0001), had a larger body surface area (BSA) (2.03 ± 0.24 versus 1.92 ± 0.22 m2, P = 0.0002), were more likely to have a history of AF (8 of 81 versus 1 of 219, P = 0.003), used preoperative antiarrhythmic medications more frequently (7 of 81 versus 4 of 219, P = 0.01), and had a more frequent rate of return to the operating room for postoperative complications (9 of 81 versus 9 of 219, P = 0.029). Furthermore, the postoperative P-wave duration decreased to a larger extent (mean change −11.3 ± 0.1 ms versus −8.4 ± 0.1 ms, P < 0.0001), and the P-wave dispersion increased postoperatively to a larger extent (3.1 ± 15.5 ms versus −1.6 ± 14.6 ms, P = 0.028) in those who subsequently developed AF compared with those without AF. Multivariate logistic regression showed age (odds ratio [OR] = 1.1, 95% confidence interval [CI]: 1.06–1.15, P < 0.0001), BSA (OR = 38.1, 95% CI: 8.2–176, P < 0.0001), and an increase in postoperative P-wave dispersion (OR = 1.03, 95% CI: 1.01–1.05, P = 0.01) to be independent predictors of postoperative AF. No surgical factor was identified to be responsible for this postoperative change in atrial electrophysiology.

Automated Electrocardiograph St Segment Trending Monitors: Accuracy in Detecting Myocardial Ischemia

Continuous automated ST segment trending devices (ST trending monitors) are included in most new operating room electrocardiography (ECG) monitors to facilitate ischemia detection, but their efficacy is not well validated.Therefore, we compared their accuracy with that of Holter ECG recorders in detecting ST segment changes (both analyzed offline) in 94 patients undergoing coronary artery bypass graft surgery. Holter ECG tapes were analyzed using standard criteria for determining ECG ischemic episodes, which were compared with those measured by the ST trending monitors. Overall, 42 ischemic episodes were detected by using the Holter monitor in 30 patients. Of the 42 episodes, 38 (90%) were also detected by the ST trending monitors. Sixteen episodes of ST segment deviation were detected by the ST trending monitors, but not by the Holter. The sensitivity of the three ST trending monitors in detecting ischemia was 75%, 78%, and 60% for the Marquette (Milwaukee, WI), Hewlett Packard (Andover, MA), and Datex (Helsinki, Finland) monitors, respectively, with a specificity of 89%, 71%, and 69% relative to the Holter. Compared with the HP and Datex monitors, the Marquette monitor has the best agreement with the Holter (K 0.64). Conditions in which ST trending monitors may be inaccurate were identified and included the appearance of small R-wave amplitude, drifting baseline, and during periods of conduction abnormalities and pacing. We conclude that ST trending monitors have only moderate sensitivity and specificity (<75% overall) in accurately detecting ECG ST segment changes compared with Holter ECG recordings. Therefore, sole reliance on ST trending monitors for the detection of myocardial ischemia may be insufficient. Implications: Using Holter recordings as the reference standard for detection of intraoperative ischemia, ST trending monitors were found to have overall sensitivity and specificity of 74% and 73%, respectively. Several conditions contribute to the inaccuracy of ST trend monitoring, and additional modification of their performance is necessary to achieve better agreement with the Holter analysis. (Anesth Analg 1998;87:4-10)

Transesophageal echocardiography in myocardial revascularization: II. Influence on intraoperative decision making

This study was conducted to determine how transesophageal echocardiography (TEE) guides intraoperative decision making during myocardial revascularization.Although its usefulness in influencing clinical decision making during cardiac valvular surgery is well documented, the clinical utility of TEE in patients undergoing myocardial revascularization is less clear. We studied the performance of five community-based, full-time cardiac anesthesiologists during 75 surgical procedures. All patients were monitored with radial artery and pulmonary artery catheters as well as biplane TEE. Immediately after each clinical intervention, the anesthesiologist was asked to determine how real-time TEE influenced the therapy, which single monitor was most influential, and why each therapy was initiated. Of the 584 interventions, TEE was the single most important guiding factor in 98 instances (17%). Interventions involving fluid administration contributed to 277 of 584 (47%) of the total clinical decisions. TEE was the most important monitor influencing fluid administration in 82 of 277 instances (30%), versus the pulmonary artery catheter in 20 of 277 instances (7%). TEE was the single most important monitor in guiding other therapies as follows: antiischemic therapy, 8 of 38 = 21%; vasopressor or inotrope administration, 4 of 115 = 3%; vasodilator therapy, 1 of 38 = 3%; antiarrhythmic medications, 0 of 16 = 0%; and depth of anesthesia, 1 of 72 = 1%. In 2 of 75 patients (3%), critical surgical interventions were made solely on the basis of TEE. Also, TEE was found to act in concert with other monitors in 254 of 584 interventions (43%). TEE is often influential in guiding decision making in myocardial revascularization when incorporated as a routine monitor in the intraoperative setting. Information from TEE has been most commonly used to guide the management of fluid administration and institution of antiischemic therapy. In a small subset of patients, TEE appears to be useful in guiding critical surgical interventions. (Anesth Analg 1996;82:1139-45)

Assessment of ventricular function in critically III patients: Limitations of pulmonary artery catheterization☆

Abstract Objective: To determine the accuracy of conventional hemodynamic assessment using pulmonary artery catheterderived data in critically ill patients. Design: Cohort study. Setting: Kaiser Permanente and Veterans Affairs Medical Centers. Participants: Twenty-five consecutive patients who had undergone elective aortocoronary bypass surgery. Measurements and Main Results: In the intensive care unit, conventional assessment (CA) was performed hourly by clinicians using conventional (radial artery and pulmonary artery) hemodynamic measurements from which left ventricular (LV) function and intracardiac volume were estimated. Simultaneously, transesophageal echocardiography (TEE) data were recorded on videotape, blinded to the clinicians, and quantitatively analyzed off-line. TEE-determined LV function was classified as either normal (ejection fraction ≥40%) or abnormal (ejection fraction 22 cm2). Conclusion: Evaluable data included 130 of 150 (87%) observations of simultaneously collected CA and TEE data, averaging 5.6 ± 4.4 observations per patient. The overall predictive probability for conventional clinical assessment of normal ventricular function was 98% ( 118 121 ), whereas for abnormal ventricular function it was 0% ( 0 9 ). For CA of volume, the overall predictive probabilities for hypovolemia, normovolemia, and hypervolemia were 50% ( 3 6 ), 60% ( 69 115 ), and 22% ( 2 9 ). Although conventional clinical assessment of normal LV function in the intensive care unit correlates well with echocardiographic assessment, both LV dysfunction and extremes of preload (hypovolemia or hypervolemia) are assessed poorly by clinicians using conventional clinical monitoring with pulmonary artery catheterization.

Effects of Dobutamine on Hemodynamics and Left Ventricular Performance after Cardiopulmonary Bypass in Cardiac Surgical Patients

BACKGROUND Dobutamine is commonly used to improve ventricular performance after cardiopulmonary bypass. The authors determined the effect of dobutamine on hemodynamics and left ventricular performance immediately after cardiopulmonary bypass in patients undergoing coronary artery bypass graft surgery. METHODS One hundred patients received sequential 3-min infusions of dobutamine at 0-40 microg x kg(-1) x min(-1) immediately after cardiopulmonary bypass. Ten additional patients who received no dobutamine served as controls. Hemodynamics and left ventricular performance (fractional area change by transesophageal echocardiography, stroke volume index, and thermodilution cardiac index) were measured. Mixed-effects modeling accounted for repeated-measures data and interindividual differences and allowed for potential effects of covariates. RESULTS Heart rate increased in a dose-dependent manner. The slope of HR versus dobutamine dose was steeper in individuals in whom peak dobutamine dose was not reached compared with that in the remaining individuals; slope decreased 2.71 +/- 0.68% per year of age. Dobutamine affected blood pressure minimally, but slightly decreased pulmonary capillary wedge pressure and central venous pressure. Systemic vascular resistance initially increased with dobutamine 10 microg x kg(-1) x min(-1) and remained constant with larger doses. Dobutamine produced a dose-dependent increase in left ventricular performance, primarily by increasing heart rate, because stroke volume index decreased with dobutamine dose. CONCLUSION Our results suggest that the response to graded dobutamine infusion in the post-cardiopulmonary bypass period differs from that previously reported. After cardiopulmonary bypass, the dominant mechanism by which dobutamine improves left ventricular performance is by increasing heart rate. Dobutamine affects blood pressure minimally.

Urine and Plasma Catecholamine and Cortisol Concentrations after Myocardial Revascularization Modulation by Continuous Sedation

Background: Cardiopulmonary bypass is associated with substantial release of catecholamines and cortisol for 12 or more h. A technique was assessed that may mitigate the responses with continuous 12‐h postoperative sedation using propofol. Methods: One hundred twenty‐one patients having primary elective cardiopulmonary bypass graft (CABG) surgery were enrolled in a double‐blind, randomized trial and anesthetized using a standardized sufentanil‐midazolam regimen. When arriving at the intensive care unit (ICU), patients were randomly assigned to either group SC (standard care), in which intermittent bolus administration of midazolam and morphine were given as required to keep patients comfortable; or group CP (continuous propofol), in which 12 h of continuous postoperative infusion of propofol was titrated to keep patients deeply sedated. Serial perioperative measurements of plasma and urine cortisol, epinephrine, norepinephrine, and dopamine were obtained; heart rate and blood pressure were recorded continuously, and medication use, including requirements for opioids and vasoactive drugs, was recorded. Repeated‐measures analysis was used to assess differences between study groups for plasma catecholamine and cortisol levels at each measurement time. Results: In the control state‐before the initiation of postoperative sedation in the ICU‐no significant differences between study groups were observed for urine or plasma catecholamine or cortisol concentrations. During the ICU study period, for the first 6–8 h, significant differences were found between study groups SC and CP in plasma cortisol (SC = 28 +/‐ 15 mg/dl; CP = 19 +/‐ 12 mg/dl; estimated mean difference [EMD] = 9 mg/dl; P = 0.0004), plasma epinephrine (SC = 132 +/‐ 120 micro gram/ml; CP = 77 +/‐ 122 micro gram/ml; EMD = 69 micro gram/ml; P = 0.009), urine cortisol (SC = 216 +/‐ 313 micro gram/ml; CP = 93 +/‐ 129 micro gram/ml; EMD = 127 micro gram/ml; P = 0.007), urine dopamine (SC = 85 +/‐ 48 micro gram; CP = 52 +/‐ 43 micro gram; EMD = 32 micro gram; P = 0.002), urine epinephrine (SC = 7 +/‐ 8 micro gram; CP = 4 +/‐ 5 micro gram; EMD = 3 micro gram; P = 0.009), and urine norepinephrine (SC = 24 +/‐ 14 mg; CP = 13 +/‐ 9 mg; EMD = 11 mg; P = 0.0004). Reductions in urine and plasma catecholamine and cortisol concentrations found for the CP group generally persisted during the 12‐h propofol infusion period and then rapidly returned toward control (SC group) values after propofol was discontinued. Postoperative opioid use was reduced in the CP group (SC = 97%; CP = 49%; P = 0.001), as was the incidence of (SC = 79%; CP = 60%; P = 0.04) and hypertension (SC = 58%; CP = 33%; P = 0.01), but the incidence of hypotension was increased (SC = 49%; CP = 81%; P = 0.001). Conclusions: Cardiopulmonary bypass graft surgery is associated with substantial increases in plasma and urine catecholamine and cortisol concentrations, which persist for 12 or more h. This hormonal response may be mitigated by a technique of intensive continuous 12‐h postoperative sedation with propofol, which is associated with a decrease in tachycardia and hypertension and an increase in hypotension.

Transesophageal echocardiography in myocardial revascularization: I. Accuracy of intraoperative real-time interpretation

Transesophageal echocardiography (TEE) is increasingly used intraoperatively as a monitor of ventricular function and volume.Despite its increasing use, whether data from TEE monitoring can be interpreted accurately on-line in real-time is unknown. We studied the performance of five community-based, full-time cardiac anesthesiologists during 75 surgical procedures in which biplane TEE monitoring was used. Every 10 min intraoperatively, each anesthesiologist evaluated the video cine loop display of echocardiographic images to provide a real-time visual estimate of left ventricular ejection fraction area (EFA) and left ventricular filling at the level of the short axis and to assess regional wall-motion of the short axis and transgastric longitudinal views using a predefined scoring system. The same video images were analyzed quantitatively off-line by two blinded investigators. Intraoperative real-time estimates of EFA correlated moderately with off-line quantification (r = 0.8, P = 0.0001). Of the 662 cine loops analyzed by both off-line and real-time techniques, 386 (55%) were within +/- 5% of each other, 495 (75%) were within +/- 10% of each other, 561 (85%) were within +/- 15% of each other, and 617 (93%) were within +/- 20% of each other. The overall sensitivity and specificity of real-time echocardiographic ischemia detection were both 76%. However, there was individual variation among the five anesthesiologists. Recognition of normal and severe regional wall-motion abnormality, such as akinesis, had more concordance between real-time and off-line analysis, 93% and 79%, respectively, than recognition of mild regional wall-motion abnormalities. Anesthesiologists can estimate EFA in real-time to within +/- 10% of off-line values in 75% of all cases. Real-time identification of normal regional function is more accurate than identification of abnormal function, i.e., there is variability in quantifying the severity of regional dysfunction. (Anesth Analg 1996;82:1132-8)

Effects of acadesine on the incidence of myocardial infarction and adverse cardiac outcomes after coronary artery bypass graft surgery

Background Acadesine (AICA riboside) (5-amino-1-[beta-D-ribofuranosy]imidazole-4-carboxamide) is a purine nucleoside analog belonging to a new class of agents generally termed adenosine regulating agents (ARAs) that increase the availability of adenosine locally in ischemic tissues. The effects of acadesine on the incidence of fatal and nonfatal myocardial infarction (MI) and on the incidence of all adverse cardiovascular outcomes (cardiac death, MI, congestive heart failure, life-threatening dysrhythmia, or cerebrovascular accident) was investigated in patients undergoing coronary artery bypass graft (CABG) surgery.

Histologic assessment of right atrial appendage myocardium in patients with atrial fibrillation after coronary artery bypass graft surgery.

Atrial fibrillation (AF) is a common complication after coronary artery bypass graft (CABG) surgery. Despite the prevalence of AF occurring after cardiac surgery, its pathophysiology is incompletely understood. Our previous study demonstrated that age and left atrial enlargement were independent predictors of postoperative AF. Accordingly, the purpose of this study was to determine whether cellular changes such as fibrosis and/or hypertrophy occurred in the atrium in patients who subsequently developed postoperative AF. Right atrial appendage tissue was obtained during atriotomy in patients undergoing elective CABG surgery. Quantitative assessment of atrial fibrosis was performed with Sirius red stain, and atrial cell diameter was measured with the HE stain. Linear regression, t test, χ2 test or Fisher exact test were used for statistical analysis. Sixty-one patients (mean age 71 ± 8 years) were studied. Increasing age was significantly associated with fibrosis (beta 0.3, 95% CI: 0.06–0.55, p = 0.017). The amount of right atrial fibrosis tended to correlate with the incidence of postoperative AF (p = 0.08). Cell diameter was not significantly different between patients with versus without postoperative AF (p = 0.85). These results suggest that the age-related atrial fibrosis rather than cellular hypertrophy may be important in the pathogenesis of AF after CABG surgery and should be further investigated.