Norbert Rolf

High thoracic epidural anesthesia, but not clonidine, attenuates the perioperative stress response via sympatholysis and reduces the release of troponin T in patients undergoing coronary artery bypass grafting.

UNLABELLED In this prospective study, we evaluated whether high thoracic epidural anesthesia (TEA) or i.v. clonidine, in addition to general anesthesia, affects the cardiopulmonary bypass- and surgery-associated stress response and incidence of myocardial ischemia by their sympatholytic properties. Seventy patients scheduled for elective coronary artery bypass graft (CABG) received general anesthesia with sufentanil and propofol. TEA was randomly induced before general anesthesia and continued during the study period in 25 (anesthetized dermatomes C6-T10). Another 24 patients received i.v. clonidine as a bolus of 4 microg/kg before the induction of general anesthesia. Clonidine was then infused at a rate of 1 microg x kg(-1) x h(-1) during surgery and at 0.2-0.5 microg x kg(-1) x h(-1) postoperatively. The remaining 21 patients underwent general anesthesia as performed routinely (control). Hemodynamics, plasma epinephrine and norepinephrine, cortisol, the myocardial-specific contractile protein troponin T, and other cardiac enzymes were measured pre- and postoperatively. During the preoperative night and a follow-up of 48 h after surgery, five-lead electrocardiogram monitoring was used for ischemia detection. 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 elevations > or = 0.2 mV or new ST depression > or = 0.1 mV occurred in > 70% of the control patients but only in 40% of the clonidine group and in 50% of the TEA group. We conclude that TEA (but not i.v. clonidine) combined with general anesthesia for CABG demonstrates a beneficial effect on the perioperative stress response and postoperative myocardial ischemia. IMPLICATIONS Thoracic epidural anesthesia combined with general anesthesia attenuates the myocardial sympathetic response to cardiopulmonary bypass and cardiac surgery. This is associated with decreased myocardial ischemia as determined by less release of troponin T. These findings may have an impact on the anesthetic management for coronary artery bypass grafting.

Thoracic epidural anesthesia and the patient with heart disease : Benefits, risks, and controversies

I n the Western world, cardiovascular morbidity is the most common primary cause of death (1,2). Coronary artery disease is a widespread concomitant condition in patients undergoing surgery (1,3). The patient with coronary artery disease is susceptible to myocardial infarction, dysrhythmias, ventricular failure, and cardiac death (1). Patients with chronic cardiovascular disease have a high risk of adverse cardiac outcome after surgery, especially after acute perioperative ischemic events (4). The optimal anesthetic and analgesic management for these patients remains undefined (5). Numerous studies have shown that stimulation of the sympathetic nervous system plays a major role in the development of perioperative myocardial ischemia (6-9). Activation of cardiac sympathetic efferents may reduce myocardial oxygen availability by inducing poststenotic coronary constriction (lo), which can lead to redistribution of myocardial blood flow with a reduction of blood supply to the subendocardium. Myocardial oxygen consumption is increased by tachycardia and increased contractility. This mismatch between oxygen delivery and demand during sympathetic activation can lead to myocardial ischemia, decreased arrhythmia threshold, and ventricular failure. In several patient populations with a high prevalence of coronary artery disease (such as peripheral vascular disease), the use of regional anesthesia has been investigated to improve outcome (11-13). Thoracic epidural anesthesia (TEA) aims at a more specific reversible blockade of cardiac sympathetic efferents and afferents and provides intraand postoperative analgesia or-in the nonsurgical population-effective therapy of angina1 pain (14). This review focuses on TEA and does not examine studies of lumbar epidural anesthesia and cardiac outcome in detail.

Frequency and severity of desaturation events during general anesthesia in children with and without upper respiratory infections

STUDY OBJECTIVE To determine whether anesthesia in the presence of a mild upper respiratory infection (URI) was associated with episodes of desaturation or reactive airway problems. DESIGN A prospective study. SETTING Inpatient and outpatient units of a university medical center. PATIENTS Four hundred two pediatric patients. INTERVENTIONS Patients were monitored with continuous recordings of oxygen saturation (SpO2), capnography, and electrocardiogram. A separate anesthesiologist was present throughout each case to observe for complications and interview the anesthesia team. The decision to anesthetize patients with a URI was left to the discretion of the anesthesia team. MEASUREMENTS AND MAIN RESULTS Thirty patients with a URI and 372 patients without one were studied. One hundred ninety-six patients were managed with endotracheal intubation and 206 with face mask; 15 in each group had a URI. There was no increase in major desaturation events (SpO2 of 85% or less for 30 or more seconds) but minor desaturation events (SpO2 of 95% or less for 60 or more seconds) were increased (p = 0.02). There was no increased frequency of laryngospasm (1 in 30 vs. 22 in 372), but there was a higher frequency of bronchospasm in intubated patients (2 in 15 vs. 1 in 181; p = 0.016). CONCLUSIONS Children with a mild URI have an increased frequency of minor desaturation episodes, and intubated patients with a URI have an increased frequency of bronchospasm. It appears that children with a mild URI may be safely anesthetized, since the problems encountered are generally easily treated and without long-term sequelae.

Milrinone Modulates Endotoxemia, Systemic Inflammation, and Subsequent Acute Phase Response after Cardiopulmonary Bypass (CPB)

BACKGROUND Compromised splanchnic perfusion and the resulting intestinal mucosal injury leads to a decreased mucosal barrier function, which allows translocation of intestinal flora and endotoxemia. The authors evaluated the effects of milrinone on splanchnic oxygenation, systemic inflammation, and the subsequent acute-phase response in patients undergoing coronary artery bypass grafting. METHODS This open, placebo-controlled randomized clinical study enrolled 22 adult patients in two groups. Before induction of anesthesia, baseline values were obtained and patients were randomized to receive milrinone (30 microg/kg bolus administered progressively in 10 min, followed by a continuous infusion of 0.5 microg x kg(-1) x min(-1)) or saline. The following parameters were determined: hemodynamics; systemic oxygen delivery and uptake; arterial, mixed venous and hepatic venous oxygen saturation; intramucosal pH (pHi); and mixed and hepatic venous plasma concentrations of endotoxin, interleukin 6, serum amyloid A, and C-reactive protein. RESULTS Milrinone did not prevent gastrointestinal acidosis as measured by pHi, but its perioperative administration resulted in significantly higher pHi levels compared with control. Venous and hepatic venous endotoxin and the interleukin 6 concentration were reduced significantly in the milrinone group. Serum amyloid A values were attenuated in the milrinone group 24 h after surgery. No significant differences could be seen in routinely measured oxygen transport-derived variables. CONCLUSIONS Perioperative administration of low-dose milrinone may have antiinflammatory properties and may improve splanchnic perfusion in otherwise healthy patients undergoing routine coronary artery bypass grafting.

Effects of Thoracic Epidural Anesthesia with and without Autonomic Nervous System Blockade on Cardiac Monophasic Action Potentials and Effective Refractoriness in Awake Dogs

BackgroundThe effects of thoracic epidural anesthesia (TEA) on myocardial repolarization and arrhythmogenicity are only incompletely understood. This is primarily because of the lack of appropriate experimental models. In most of the studies performed thus far, TEA was used in anesthetized animals. Baseline anesthesia itself may have modified the effects of TEA. This study investigates right atrial and ventricular repolarization by recording monophasic action potentials after TEA in awake dogs. The authors hypothesized that an antiarrhythmic role of TEA exists, which may be related to a direct effect of TEA on myocardial repolarization. MethodsThe hypothesis was tested in an in vivo canine model, in which atrial and ventricular myocardial action potential duration and refractoriness are recorded by means of monophasic action potential catheters. ResultsThoracic epidural anesthesia significantly increased ventricular monophasic action potential duration for cycle lengths shorter than 350 ms. Changes in monophasic action potential duration were paralleled by a concomitant prolongation of effective refractory period (ERP) at higher rates so that the ratio of ERP to action potential duration was unaffected. ConclusionsThis model helps to study the role of TEA on ventricular repolarization and arrhythmogenicity. Because lengthening of repolarization and prolongation of refractoriness may, in some circumstances, be antiarrhythmic, TEA may be protective against generation of ventricular arrhythmias mediated, e.g., by increased sympathetic tone. The results also imply that the beneficial role of TEA might be stronger at the ventricular site as compared with the atrium. At atrial sites there was only a trend toward prolongation of repolarization even at short cycle lengths.

Comparative hemodynamic effects of three different parenterally administered lipid emulsions in conscious dogs

OBJECTIVE To compare the hemodynamic side effects of three structurally different lipid emulsions. DESIGN Randomized, controlled, prospective animal study. SETTING University research laboratory. SUBJECTS Six chronically instrumented mongrel dogs. INTERVENTIONS On separate days, all animals were submitted to three different treatments, in a randomized order. After baseline measurements, either a long-chain triglyceride emulsion (treatment 1), a mixed medium-chain triglyceride/long-chain triglyceride emulsion (treatment 2), or an omega3 polyunsaturated fatty acid long-chain triglyceride (PUFA) emulsion (treatment 3) was administered intravenously over 30 mins. MEASUREMENTS AND MAIN RESULTS Global and regional hemodynamics (sonomicrometry) were recorded for 2 hrs after baseline measurements. Arterial blood gases and plasma concentrations of hemoglobin, triglycerides, total protein, and glucose were recorded for 2 hrs. Long-chain triglycerides did not affect the cardiovascular performance in awake animals. However, medium-chain triglycerides/long-chain triglycerides and omega3 PUFA caused marked increases in systemic vascular resistance (from 1833 +/- 154 to 3277 +/- 163 mm Hg/dynexsec5, p < .05), heart rate (from 89 +/- 6 to 158 +/- 10 beats/min, p < .05), and depressed ventricular performance (wall-thickening fraction [as percentage from baseline] decreased to 53 +/- 9%, p < .05). CONCLUSIONS Commercially available lipid emulsions can cause profound cardiovascular side effects at high doses, depending on their composition. Whereas long-chain triglyceride emulsions have virtually no effects on hemodynamics in normal dogs, medium-chain triglyceride/long-chain triglyceride, and omega3 PUFA emulsions should be used with caution in critically ill patients with compromised cardiovascular function.

Persistent cardiac arrhythmias in pediatric patients: effects of age, expired carbon dioxide values, depth of anesthesia, and airway management.

The presence of persistent arrhythmias was correlated with hypercarbia (end-tidal CO2 greater than or equal to 55 mm Hg for greater than or equal to 60 s). A continuous strip chart recording of oxygen saturation, a capnogram, and an electrocardiogram were obtained from 402 children. No episodes of arrhythmia occurred in 153 patients younger than 2 yr compared with 24 patients 2 yr of age or older (P = 0.0001). Older patients whose airways were managed via a mask had a higher incidence (13.2% [21 of 159 patients]) than tracheally intubated patients (3.3% [3 of 90 patients]) (P = 0.01). In older patients whose tracheas were intubated, hypercarbia was associated with arrhythmia in 1 of 20 hypercarbia episodes. Seven of 16 patients with hypercarbia, whose airways were managed via a mask, had an arrhythmia (P = 0.0014); in eight, arrhythmias were associated with light anesthesia; in seven, arrhythmias were not associated with either hypercarbia or light anesthesia. Arrhythmias developed in 13 of 55 patients 2 yr old or older whose airways were managed via a mask and who were undergoing orchiopexy or herniorrhaphy as compared with 1 of 30 tracheally intubated patients (P = 0.016). There was a higher incidence of arrhythmias during halothane anesthesia compared with that during all other techniques (P = 0.035). The authors conclude that the incidence of arrhythmias is extremely low in infants younger than 2 yr. Hypercarbia is associated with arrhythmias in pediatric patients whose airways are managed via a mask but not in patients whose tracheas are intubated.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of thoracic epidural anesthesia on functional recovery from myocardial stunning in propofol-anesthetized dogs.

The purpose of this investigation was to examine the effects of thoracic epidural anesthesia (TEA) on myocardial stunning during propofol anesthesia.Six dogs were chronically instrumented for measurement of left atrial, aortic, and left ventricular pressure, maximal rate of increase of left ventricular pressure, and myocardial wall-thickening fraction (WTF). Myocardial blood flow was determined with colored microspheres. Experiments were performed on separate days with 1) 10 min of left anterior descending artery (LAD) ischemia during propofol anesthesia without TEA, and 2) 10 min of LAD ischemia during propofol anesthesia with TEA. WTF was measured as baseline (BL) prior to propofol anesthesia and at predetermined time points until complete recovery from stunning. Propofol anesthesia caused a significant decrease of WTF in the LAD-perfused myocardium (LAD-WTF) compared to BL in awake animals. LAD ischemia led to a further significant decrease of LAD-WTF. There were no significant differences in LAD-WTF between the two experimental conditions at any of the time points measured. TEA did not change subendocardial blood flow in nonischemic myocardium. During ischemia neither the subendocardial/subepicardial nor the occluded/normal zone blood flow ratio were affected by TEA. After myocardial ischemia during propofol anesthesia TEA does not affect functional recovery of stunned myocardium in dogs. (Anesth Analg 1997;84:723-9)

The early response genes c-jun and HSP-70 are induced in regional cardiac stunning in conscious mammals.

OBJECTIVES A reversible contractile dysfunction without necrosis after transient myocardial ischemia has been termed stunning. The molecular mechanisms underlying this phenomenon are only now beginning to be unraveled. It is conceivable that the expression of early-response genes may play a crucial role in stunning. METHODS The expression of HSP-70, c-jun, and GRP-94 was investigated in a chronically instrumented dog model (n = 9). The left anterior descending coronary artery was occluded temporarily for 10 minutes after the animals had fully recovered from instrumentation. The wall thickening fraction was measured in the left anterior descending coronary artery and the nonischemic ramus circumflex of the left coronary artery-perfused region. When the wall thickening fraction of the left anterior descending coronary artery had recovered to 50% of preocclusion values, tissue samples were obtained from the areas perfused by the left anterior descending coronary artery and the nonischemic ramus circumflex of the left coronary artery. RESULTS The messenger RNA of HSP-70 was increased to 214% +/- 26% in the area perfused by the left anterior descending artery compared with that perfused by the nonischemic ramus circumflex of the left coronary artery. There was no difference in the messenger RNA of GRP-94. The HSP-70 content was elevated to 130% +/- 14% in the left anterior descending artery compared with the area perfused by the ramus circumflex of the left coronary artery, and the c-jun protein content was 70% +/- 25% higher in the ischemic area compared with the control area. CONCLUSIONS The induction of early-response genes observed here may indicate that they play an adaptive role in myocardial stunning, even in conscious mammals.

Coronary Artery Bypass Grafting With an Expanded Polytetrafluoroethylene Graft

BACKGROUND We report our experience with the Perma-Flow aortocoronary-right heart graft in 15 patients in whom autologous conduits were not available. METHODS Fifteen patients received 39 coronary anastomoses--10 to left anterior descending coronary artery branches, 15 to circumflex coronary artery branches, and 14 to branches of the right coronary artery. Early angiography was done in 11 patients. RESULTS One patient died on postoperative day 17 of multiorgan failure. The graft was patent at postmortem examination. Of 30 coronary anastomoses at risk, 24 were patent. Three connections to the left anterior descending system were occluded in patients with an additional internal mammary artery graft to the same coronary system, and three connections to the circumflex system were occluded in patients with a history of major posterior infarction. Three of five distal anastomoses to the right atrial appendage were occluded, whereas all six connections to the superior vena cava were patent. None of the patients had shown recurrent angina at a mean follow-up of 10.9 months (range, 2-39 months). CONCLUSIONS The synthetic Perma-Flow coronary graft appears to be a safe alternative in patients in whom arterial or venous conduits are not available. Competitive flow may lead to anastomotic occlusions. The appropriate site for the distal arteriovenous fistula seems to be the superior vena cava.