Prebypass Period Research Articles

Effects of Extracorporeal Circulation on Renal Function in Coronary Surgical Patients

Comment Although the authors found a logical result, it is a surprising one. Extracorporeal circulation did not adversely affect renal function. In fact, the functional alterations that occurred preopera-tively and in the prebypass period seem almost to be reversed by the benefits of extracorporeal circulation. Although that may be extrapolating the data a little too far, it is clear from the results obtained that the most hazardous times for renal damage to patients are the prebypass and postbypass periods.

Case 3—1996 unusual cause of hypotension after cardiopulmonary bypass

A 60-year-old 120-kg woman with severe aortic stenosis presented for aortic valve replacement. She presented with progressive exertional dyspnea, paroxysmal nocturnal dyspnea, and two-pillow orthopnea. Other pertinent conditions included hypertension, morbid obesity, and chronic phlebitis. Peak systolic pressure gradient was 75 mmHg, and the calculated aortic valve area was less than 1 cm 2. Cardiac catheterization also showed mild coronary atherosclerosis and normal left ventricular function. Preoperative medications included methyldopa, hsinopril, and warfarin. Warfarin was discontinued 6 days before surgery. Physical examination showed a grade I I I /VI systolic ejection murmur at the right upper sternal border that radiated to the carond arteries. Her chest x-ray showed mild interstitial fibrosis but was otherwise normal. Electrocardiogram (ECG) showed sinus rhythm, left ventrlcular hypertrophy, an old inferior myocardial infarction, and mtraventricular conduction delay. Laboratory results included a white blood cell count of 6,200/ixL, Hgb 13.5 g/dL, hematocrit 40.3%, and prothrombin time 13.4 seconds (normal range 11.0 to 12.0 seconds). After premedicatlon with morphine, 6 nag intramuscularly, the patient was brought to the operating room and placed supine on the operating room table. Routine monitors (ECG, nonmvaswe blood pressure (BP); pulse oxlmeter) were applied, and a pulmonary artery catheter was placed without difficulty via the right internal jugular vein. After several unsuccessful attempts at placing a 20-G right femoral arterial catheter, a 20-G 15-cm left femoral arterial catheter was placed with some difficulty. The right femoral artery had been successfully punctured with a Seldinger needle, but difficulties in advancing a guideline precluded successful cannulahon. General anesthesia was induced using etomidate, 0.1 mg/kg, fentanyl, 8 Ixg/kg, midazolam, 30 ixg/kg, and succinylcholine, 1.2 mg/kg. General anesthesia was maintained using fentanyl, 30 txg/kg, and isoflurane, up to 0.8 minimum alveolar concentration for BP control. Hemoglobin concentration after anesthetic reduction was 12.3 g/dL. The prebypass period was uneventful with mlmmal blood loss, and 1,500 mL of lactated Ringer's solution was administered intravenously before cardiopulmonary bypass (CPB). Anticoagulataon was achieved with 300 U/kg of heparin, and the activated clotting time was maintained at greater than 400 seconds throughout CPB for a total heparln dose of 40,000 units. Representatwe hemodynamics before CPB were BP 95/55, pulmonary artery (PA) pressure 26/16, right atrial pressure (CVP) 11, and cardiac index (CI) 1.8 L/min/m 2. The extracorporeal circuit was primed with 1,500 mL of balanced salt solution, 500 mL of 5% mannmtol solution, and 5,000 units of heparin. The initial hemoglobin concentration during CPB was 7.3 g/dL, which was increased to 8.8 g/dL by the end of CPB with 2 units of packed red blood cells (RBCs). An additional 1,200 mL of Plasmalyte was administered during bypass. Blood loss during CPB was conserved by a Haemonetics Cell Saver (Haemonetics, Inc, Bramtree, MA) device and did not appear excessive. The patient separated easily from bypass with a central venous pressure (CVP) of 3 mmHg and PA pressures of 28/13 mmHg. CI was 2.5 L/min/m 2, and protamine, 350 mg, was administered over 15 minutes. Soon after the protamine infusion was completed, the patient's systolic blood pressure (SBP) decreased to 64 mmHg. Intravenous hetastarch 6% was administered to maintain adequate CVP and PA diastolic pressures. However, even after 1,000 mL of hetastarch, hypotensmon continued. PAL pressure remained around 28/15 mmHg, while CVP remained less than 5 mmHg. CI was 4 to 4.5 L/min/m 2, whereas systemic vascular resistance (SVR) was 500 to 600 dyne/s/cm -5. With SBP m the 60s (mmHg) and mean arterial pressure (MAP) m the high 40s (mmHg), an anaphylactic or anaphylactoid reaction to protamine was presumed to be causing the hypotension. Diphenhydramine, 50 mg, and hydrocortisone, 120 rag, were administered intravenously, an epinephrine bolus (100 Ixg) was administered, and an epinephrine infusion was begun at 8 ixg/min. This therapy increased SBP into the 80s (mmHg), which was maintained by repeated 100-1xg boluses of epinephrine and by increasing the epinephrine infusion rate to 10 to 20 ~g/min. ABG

Thoracic Epidural Anesthesia During Coronary Artery Bypass Surgery

The effects of high thoracic epidural anesthesia (TEA) on cardiac sympathetic nerve activity, myocardial blood flow and metabolism, and central hemodynamics were studied in 20 patients undergoing coronary artery bypass grafting (CABG). In 10 of the patients, TEA (T1-5 block) was used as an adjunct to a standardized fentanyl-nitrous oxide anesthesia. Hemodynamic measurements and blood sampling were performed after induction of anesthesia but prior to skin incision and after sternotomy. Assessment of total and cardiac sympathetic activity was performed by means of the norepinephrine kinetic approach. Prior to surgery, mean arterial pressure (MAP), great cardiac vein flow (GCVF), and regional myocardial oxygen consumption (Reg-MVO2) were lower in the TEA group compared to the control group. During sternotomy there was a pronounced increase in cardiac norepinephrine spillover, MAP, systemic vascular resistance index (SVRI), pulmonary capillary wedge pressure (PCWP), GCVF, and Reg-MVO2 in the control group. These changes were clearly attenuated in the TEA group. None of the patients in the TEA group had metabolic (lactate) or electrocardiographic signs of myocardial ischemia. Three patients in the control group had indices of myocardial ischemia prior to and/or during surgery. We conclude that TEA attenuates the surgically mediated sympathetic stress response to sternotomy, thereby preventing the increase in myocardial oxygen demand in the pre-bypass period without jeopardizing myocardial perfusion.

The Effects of Anesthetic Technique on the Hemodynamic Response and Recovery Profile in Coronary Revascularization Patients

This study was undertaken to assess the effects of propofol (versus enflurane, fentanyl, and thiopental) on hemodynamic stability and recovery characteristics when used for maintenance of anesthesia during elective coronary artery bypass grafting (CABG) procedures.Ninety premedicated patients scheduled for elective coronary revascularization had anesthesia induced with fentanyl 25 micro gram/kg intravenously (IV). When the mean arterial blood pressure (MAP) increased 10% above preoperative baseline values, patients were randomized to receive one of four anesthetic treatments: enflurane, 0.25-2.0%; fentanyl, 10-20 micro gram/kg IV bolus doses; propofol, 50-250 micro gram centered dot kg-1 centered dot min-1 IV; or thiopental, 100-750 micro gram centered dot kg-1 centered dot min-1 IV. The maintenance anesthesia was titrated to achieve hemodynamic stability (i.e., maintain the MAP within 10% of the baseline values and heart rate [HR] within 20% of the baseline values). After bypass, anesthetic and cardiovascular drugs were titrated to maintain the MAP >65 mm Hg and the cardiac index (CI) >2.3 L centered dot min-1 centered dot m-2. Recovery was assessed by noting the times at which patients first opened their eyes, responded to verbal communication, correctly responded to specific commands, underwent tracheal extubation, and were discharged from the intensive care unit (ICU). Although less intraoperative hypertension was noted in the propofol-treated patients (19 +/- 11 min vs 38 +/- 26 min, 30 +/- 24 min, and 30 +/- 23 min in the enflurane, fentanyl, and thiopental groups, respectively) (P = 0.04), the incidence of hypotension did not differ significantly among the groups. Vasopressor drugs were required more often during the prebypass period in fentanyl and propofol patients (4/22 and 5/23, respectively) compared to the thiopental group (0/21) (P < 0.05). During CPB, fentanyltreated patients required vasoconstrictors more often than patients in the other three treatment groups (14/22 vs 6/24, 4/23, and 5/21 in the enflurane, propofol, and thiopental groups, respectively) (P < 0.01). Although fentanyl-treated patients had significantly greater requirements for inotropic support during weaning from CPB than propofol-treated patients (14/22 vs 7/23) (P < 0.038), there were no significant differences among the groups in the postbypass or ICU periods. Propofol-treated patients responded to verbal stimuli (2.1 +/- 1.3 h vs 4.0 +/- 3.5 h, 4.7 +/- 2.7 h, and 5.6 +/- 3.6 h in the enflurane, fentanyl, and thiopental groups, respectively) (P = 0.01) and followed commands earlier (propofol 7.3 +/- 5.2 h vs enflurane 12.5 +/- 5.7 h, fentanyl 13.1 +/- 6.6 h, and thiopental 12.8 +/- 6.7 h) (P = 0.01). In addition, propofoltreated patients were tracheally extubated sooner than patients in either the fentanyl or the thiopental group (14 +/- 5 h vs 29 +/- 19 h and 20 +/- 4 h, respectively) (P = 0.001). Although the cost of the study drug was highest in the propofol group (propofol $46 +/- 22 vs enflurane $7 +/- 3, fentanyl $10 +/- 4, and thiopental $6 +/- 3), the ability to "fast track" patients receiving propofol would be expected to offset its greater cost. We conclude that shorter-acting drugs (e.g., propofol and enflurane) can facilitate an early recovery after coronary artery revascularization without compromising intraoperative hemodynamic stability. (Anesth Analg 1995;81:900-10)

A Gastric Laceration After Transesophageal Echocardiography in a Patient Undergoing Aortic Valve Replacement

Transesophageal echocardiography (TEE) is a low risk procedure frequently used for intraoperative monitoring in patients undergoing cardiac surgery. Daniel et al. [1] demonstrated an 0.18% overall complication rate in 10,419 awake and asleep TEE examinations. Gastrointestinal complications of TEE are rare and have been previously confined to the oropharynx and esophagus [2]. There are four cases of esophageal lacerations resulting in gastrointestinal bleeding in the literature [3,4]. We report a case of gastric laceration resulting in gastrointestinal bleeding in a patient after intraoperative TEE examination. Case Report A 65-yr-old man underwent elective aortic valve replacement for severe aortic regurgitation and mild aortic stenosis causing progressive angina and congestive heart failure. His medical history was also remarkable for coronary artery disease (status postcoronary artery bypass grafting in 1984), a previous cerebrovascular accident, and a remote smoking history. He denied a history of peptic ulcer disease, gastritis, or increased bleeding tendencies. His medications included daily enteric-coated aspirin, captopril, and atenolol. Preoperatively, the hemoglobin was 14.9 g/dL, the hematocrit was 42.9%, the prothrombin time was 12.8 s, and the partial thromboplastin time was 30 s. Cardiac catheterization demonstrated patency of three of four saphenous vein grafts. The ejection fraction was estimated to be 45%-55%. After induction of anesthesia and tracheal intubation, a Hewlett Packard Omniplane TEE probe was inserted into the esophagus without difficulty. The heart and aorta were examined from the esophagus and from the stomach. The probe was only slightly anteflexed in the stomach to obtain the short axis view of the left ventricle. The initial examination was performed without apparent incident and the probe was left in the unlocked position in the stomach throughout the pre-bypass period for monitoring of left ventricular function. After the examination, 24,000 U of heparin were administered intravenously. Aminocaproic acid 10 g was administered intravenously over 30 min, followed by an infusion of 5.0 g over 6 h. After heparinization, cardiopulmonary bypass was initiated, the native aortic valve was excised, and a Starr-Edwards valve was inserted. TEE imaging was done while on bypass to assist with the removal of intracardiac air. After uneventful separation from bypass, the probe was advanced to 50 cm and the tip was anteflexed to 120 degrees to obtain an apical long axis view for better visualization of the prosthetic valve. Two units of packed red blood cells was given for a hematocrit of 22% and 1 U of platelets was given for generalized nonsurgical bleeding. Protamine 350 mg was given to reverse the initial heparin dose of 24,000 U. An orogastric tube was placed as per routine after the TEE probe was removed and 150 mL of blood was suctioned from the stomach. On arrival in the intensive care unit, an additional 500 mL of blood was suctioned from the stomach and an emergent endoscopy was performed. The examination demonstrated a fibrin clot in the cardia of the stomach at the proximal aspect of a 5-cm strip of denuded mucosa Figure 1. The edges were sharp and well circumscribed and there was no active bleeding. An additional 3 U of packed red blood cells was given for a hematocrit of 26%. The patient made a full recovery without any evidence of further bleeding.Figure 1: The laceration is seen between the two arrows. The arrows point to the laceration's well circumscribed edges.Discussion The overall incidence of gastrointestinal bleeding with TEE in awake and asleep patients is 0.02%. Despite the low risk of bleeding, multiple factors contribute to the potential for gastrointestinal bleeding in patients requiring cardiopulmonary bypass [2,3,5,6]. Insertion and manipulation of the probe is blind, and there is no patient feedback for painful stimulus. Anticoagulation and postcardiopulmonary bypass coagulopathies may exacerbate any bleeding. Finally, the probe remains in the esophagus or stomach for the duration of surgery, and the examination is conducted prior to, during, and after cardiopulmonary bypass. Examination may require an apical four-chamber view, which requires into the stomach. In this patient, the apical fourchamber view was attempted to provide better visualization of the aortic valve. With this maneuver, the probe is anteflexed in the cardia of the stomach with the tip in contact with the gastric mucosa. The gastric cardia was the location of the laceration seen on endoscopy. The laceration appeared to be traumatic in origin due to the sharp, well circumscribed edges. We believe that in this patient, the laceration most likely occurred while obtaining this view. In conclusion, the potential for gastrointestinal bleeding exists in patients undergoing TEE examination during cardiac procedures. As the apical four-chamber view requires extreme anteflexion and may be more likely to injure the gastric mucosa, extra caution may be warranted when obtaining this view.

Anesthesia for Aortic and Mitral Valve Replacement in a Patient with Carcinoid Heart Disease

Anesthesia for Aortic and Mitral Valve Replacement in a Patient with Carcinoid Heart Disease

Thoracic Epidural Anesthesia During Coronary Artery Bypass Surgery

The effects of high thoracic epidural anesthesia (TEA) on cardiac sympathetic nerve activity, myocardial blood flow and metabolism, and central hemodynamics were studied in 20 patients undergoing coronary artery bypass grafting (CABG). In 10 of the patients, TEA (T1–5 block) was used as an adjunct to a standardized fentanyl-nitrous oxide anesthesia. Hemodynamic measurements and blood sampling were performed after induction of anesthesia but prior to skin incision and after sternotomy. Assessment of total and cardiac sympathetic activity was performed by means of the norepinephrine kinetic approach. Prior to surgery, mean arterial pressure (MAP), great cardiac vein flow (GCVF), and regional myocardial oxygen consumption (Reg-MVo2) were lower in the TEA group compared to the control group. During sternotomy there was a pronounced increase in cardiac norepinephrine spillover, MAP, systemic vascular resistance index (SVRI), pulmonary capillary wedge pressure (PCWP), GCVF, and Reg-MVo2 in the control group. These changes were clearly attenuated in the TEA group. None of the patients in the TEA group had metabolic (lactate) or electrocardiographic signs of myocardial ischemia. Three patients in the control group had indices of myocardial ischemia prior to and/or during surgery. We conclude that TEA attenuates the surgically mediated sympathetic stress response to sternotomy, thereby preventing the increase in myocardial oxygen demand in the pre-bypass period without jeopardizing myocardial perfusion. (Anesth Analg 1994;79:1075–81)

Propofol-fentanyl anesthesia: A comparison with isoflurane-fentanyl anesthesia in coronary artery bypass grafting and valve replacement surgery

The hemodynamic effects of propofol-fentanyl and isofluranefentanyl anesthesia during the prebypass period were compared in 42 patients undergoing coronary artery bypass grafting (CABG) and 22 patients undergoing valve replacement (VR) for stenotic lesions. Anesthesia was induced with fentanyl, 25 μg/kg, and pancuronium, 0.1 mg/kg, and was maintained with a propofol infusion commenced at 4 mg/kg/h (range 1 to 10 mg/kg/h) orwith isoflurans commenced at 1% (range 0 to 2%). Additional fentanyl, 7.5 μg/kg, was given before stemotomy. Hemodynamic measurements were made before induction of anesthesia and at various times in the prebypass period. In the VR group, there were no significant differences between the two anesthetics in any hemodynamic variables during the study. Significant decreases ( P < 0.05) in mean arterial pressure (MAP 14%), left ventricular stroke work index (LVSWI 29%), and stroke volume index (SVI 24%) occurred after 15 minutes of propofol anesthesia in the CABG group. With isoflurane MAP was well maintained with reductions in LVSWI and SVI of 22% and 20%, respectively. Isoflurane was, however, associated with a significant increase in heart rate (HR) in the CABG group ( P < 0.05), whereas no significant change in HR occurred in CABG or VR patients receiving propofol. With both techniques there were no significant changes in right-sided or left-sided filling pressures or in systemic vascular resistance index in the CABG or VR groups, except for a decrease in pulmonary artery occlusion pressure in the propofol VR group and isoflurane CABG group at the time of aortic cannulation. Propofol produced similar hemodynamic changes in the CABG and VR groups. Both anesthetic techniques caused myocardial depression and effectively controlled the autonomic responses to sternotomy in both groups. The study suggests that propofol-fentanyl anesthesia is an acceptable technique for CABG surgery and for VR in patients with stenotic valvular heart disease.

Neutrophil Lactoferrin Release During Open Heart Surgery Is Unrelated to Complement Activation

The relationship between neutrophil activation and complement activation during open heart surgery was evaluated by measuring plasma lactoferrin and C3a des Arg (C3a) in 30 adult patients undergoing coronary artery surgery. Measurements were made before induction of anesthesia, before cardiopulmonary bypass, at the end of bypass, and 10 min after protamine infusion. Changes in the measured parameters thus reflected activation during the three distinct phases of cardiac surgery: pre cardiopulmonary bypass, the bypass phase, and the heparin neutralization phase. A major rise in lactoferrin occurred in the pre bypass period, from 99 +/- 13 (mean +/- SEM) to 647 +/- 48 ng/ml (p < 0.001). During this time, C3a levels did not rise significantly (384 +/- 22 to 439 +/- 36 ng/ml). The bypass procedure resulted in a rise of both lactoferrin and C3a levels, with lactoferrin reaching 1,092 +/- 69 ng/ml and C3a increasing to 1,884 +/- 179 ng/ml after bypass (p < 0.001 for both). In individual patients, however, the changes in lactoferrin during bypass did not correlate with changes in C3a levels (r = -0.06). After protamine infusion, C3a levels reached 3,301 +/- 324 ng/ml, while the plasma lactoferrin levels declined to 522 +/- 57 ng/ml. Thus, during open heart surgery, neutrophil activation, as measured by plasma lactoferrin concentration, does not correlate with complement activation resulting from the bypass procedure or the protamine neutralization of heparin. The potential clinical relevance of the neutrophil granular release of lactoferrin is discussed.

High-dose steroids prevent placental dysfunction after fetal cardiac bypass

Surgical treatment of certain congenital heart lesions in utero may have a therapeutic advantage over postnatal repair or palliation. For fetal heart surgery to be possible, a method to support the fetal circulation is necessary. Early experimental attempts at fetal cardiac bypass were unsuccessful because of increased placental vascular resistance during and after fetal cardiac bypass, which led to decreased placental flow, fetal asphyxia, and death. Our laboratory has demonstrated that the administration of indomethacin (a cyclooxygenase inhibitor) during fetal cardiac bypass prevents this increase in placental vascular resistance during and after fetal cardiac bypass. The specific mechanism by which indomethacin achieves this effect is likely to be either by inhibiting the production of a placental vasoconstrictive prostaglandin or by diverting substrate from the cyclooxygenase pathway to the lipoxygenase pathway, thereby potentially increasing the production of a placental vasodilating leukotriene. To examine these potential mechanisms in more detail, we inhibited both prostaglandin and leukotriene synthesis at the phospholipase stage with high-dose steroids. Fourteen fetal lambs were used in the study. Six animals received indomethacin (3 mg/kg), four received high-dose steroids (Solu-Medrol 50 mg/kg), and four animals were used as controls. Observations were made during a 1-hour prebypass period, a 30-minute bypass period, and a 2-hour postbypass period. Placental blood flow and placental vascular resistance were calculated at four times during the experiments: before sternotomy; after sternotomy; during bypass at 30 minutes; and 30 minutes after cessation of bypass. Similar to indomethacin, high-dose steroid administration during fetal cardiac bypass prevents the rise in placental vascular resistance and preserves placental blood flow during and after fetal cardiac bypass. This study suggests that the production of a placental vasoconstrictive prostaglandin is responsible for the increase in placental vascular resistance and decrease in placental blood flow observed after fetal cardiac bypass. (J T HORAC CARDIOVASC SURG 1994;107:116-25)

Arterial Pressure during Open Cardiac Surgery: Radial vs. Dorsalis Pedis

Fifty consecutive adult patients undergoing elective coronary artery bypass grafting or valve replacement had their left radial and dorsalis pedis arteries cannulated with 20G arterial cannula during a standard anesthetic induction. Similar pressure monitoring systems were used for both arteries. The left radial and dorsalis pedis pressures were recorded at 10-minute intervals during the prebypass, postbypass, and postoperative periods (up to 6 hours) and statistically analyzed. There were 38 male and 12 female patients, with a mean (SD) age of 50.3 (11.3) years. In the prebypass period, the dorsalis pedis systolic was significantly higher than the left radial systolic pressure; whereas, the mean arterial pressure was similar in both arterial systems. During the postbypass period, systolic and mean pressures in the dorsalis pedis were significantly lower than those in the left radial. The normal prebypass relationship of the dorsalis pedis and left radial was reestablished in the postoperative period at a mean time (SD) of 4.8 (1.2) hours after moving to the intensive care unit.

Effects of a continuous diltiazem infusion on renal function during cardiac surgery

Thirty-five male patients undergoing coronary artery surgery were studied to investigate renal function during a continuous infusion of the calcium channel blocker diltiazem. All patients had preoperative renal function within normal limits (serum creatinine below 0.133 mmol/L) and were randomly divided into three groups: Control (C), Diltiazem 1 (D1), and Diltiazem 2 (D2). Diltiazem was infused in D1 (1 μg/kg/min) and D2 (2 μg/kg/min) patients throughout surgery and during the following 36 hours. Glomerular function was investigated using the endogenous creatinine clearance while tubular function was assessed by means of water and sodium reabsorption tests, as well as urinary enzyme activity measurements. Hemodynamic monitoring was performed using a pulmonary artery catheter. The glomerular filtration rate of C and D1 patients showed a significant fall during cardiopulmonary bypass (CPB) with respect to the prebypass period and returned to the baseline values only in the postoperative period. A similar change was not observed in D2 patients. The analysis of variance demonstrated that the glomerular filtration rate was significantly higher in Group D2 versus Group C during and after CPB ( P = 0.03 and P = 0.04, respectively). Furthermore, after CPB, urinary output was significantly improved in D2 patients, both versus C and D1 patients ( P = 0.003), notwithstanding a lower mean arterial pressure in the D2 Group ( P = 0.04 v C Group). Tubular function was not influenced by diltiazem infusion. It is concluded that a continuous diltiazem infusion, at a dose of 2 μg/kg/min during cardiac surgery, may be useful to prevent a decrease in glomerular function secondary to cardiopulmonary bypass.

Propofol‐fentanyl anaesthesia in cardiac surgery: a comparison in patients with good and impaired ventricular function

The haemodynamic effects of propofol-fentanyl anaesthesia for elective cardiac surgery were compared in 24 patients with good left ventricular function (ejection fraction > 45%, left ventricular end-diastolic pressure < 16 mmHg) and nine patients with impaired function. Anaesthesia was induced with fentanyl 25 micrograms.kg-1 and pancuronium 0.1 mg.kg-1 and was maintained with a variable rate propofol infusion, mean rate 2.61 mg.kg-1 x h-1 in the good ventricular function group and 2.71 mg.kg-1 x h-1 in the impaired function group. Additional fentanyl 7.5 micrograms.kg-1 was given before sternotomy. Ventilation to normocarbia was with air and oxygen (FIO2 0.6). Haemodynamic measurements were made before induction, after tracheal intubation, before and after sternotomy and before aortic cannulation. There were no significant differences between the groups in any haemodynamic variables during the study. Twenty minutes after intubation both groups showed a decrease from pre-induction values in mean arterial pressure (p < 0.05) and left ventricular stroke work index (p < 0.05), the reduction in left ventricular stroke work index remaining significant during the prebypass period in both groups. There were no significant changes in right or left sided filling pressures, systemic vascular resistance or heart rate. The technique decreased cardiac work and effectively controlled the autonomic responses to sternotomy in both groups. This study suggests that propofol may be a suitable adjunct to opioid anaesthesia in patients with impaired ventricular function having cardiac surgery.

RETRACTED: VOLUME REPLACEMENT WITH HYDROXYETHYL STARCH SOLUTION IN CHILDREN

In 30 consecutive children undergoing cardiac surgery, two different types of fluid were given randomly for volume replacement in the pre-bypass period. In group 1 (n = 15), low molecular weight hydroxyethyl starch solution (LMW-HES) (6% HES; mean molecular weight 200,000 Da, molar substitution 0.5) and in group 2 (n = 15) 20% albumin (HA) was infused from the induction of anaesthesia until the start of cardiopulmonary bypass (CPB). In addition to haemodynamic values, various laboratory variables were measured before and after CPB until the morning of the 1st day after operation. The patients did not differ in diagnosis and conduct of CPB (lowest rectal temperatures: group 1 29.0 (SD 1.1) degrees C; group 2 29.4 (1.0) degrees C). Haemodynamic data (MAP, HR, CVP), anti-thrombin-III, fibrinogen, platelet count and coagulation variables were comparable between the groups until the 1st day after operation. Postoperative blood loss and the use of homologous blood or blood products were similar in all children. Albumin concentration increased after infusion of albumin (35-47 g litre-1) and was significantly greater until the end of the operation compared with the LMW-HES-treated children. Colloid osmotic pressure, however, was similar in the two groups and returned to baseline values on the 1st day after operation (LMW-HES group 19.31 (1.2) mm Hg; HA group 18.0 (1.3) mm Hg). Post-bypass urine output and creatinine values also did not differ between the groups. Anaphylactic reactions were not observed in any of the patients. It can be concluded that LMW-HES solution can be used effectively and safely for volume replacement in the pre-bypass period in small children undergoing cardiac surgery.

Whole body oxygen consumption after hypothermic cardiopulmonary bypass.

Whole body oxygen consumption and the substrate for energy production during the post-bypass period have not been clarified. We hypothesized that the substrate composition for energy production during post-bypass period might be different from that during pre-bypass period because of surgical diabetic state induced by hypothermic cardiopulmonary bypass (CPB). We measured whole body oxygen consumption, carbon dioxide production and respiratory quotient by the gas exchange method using the Datex Deltatrac before and after hypothermic cardiopulmonary bypass. We also measured oxygen consumption by Fick's principle. Whole body oxygen consumption (P < 0.001) and carbon dioxide production (P < 0.05) increased significantly above pre-CPB values after the termination of CPB. Respiratory quotient (P < 0.01) decreased significantly below pre-CPB values after the termination of CPB. We conclude that oxygen consumption increased significantly above pre-bypass values after the termination of hypothermic cardiopulmonary bypass at least under the fentanyl, diazepam, chlorpromazine anesthesia with continuous infusion of nitroglycerin and nicardipine. The changes in respiratory quotient suggest a relatively higher ratio of lipid metabolism for energy production during post-bypass period.

Effects of steal-prone anatomy on intraoperative myocardial ischemia

Objectives. Our study abjective was to determine whether the presence of steal-prone anatomy conferred an increased risk in the of intraoperative myocardial ischemia.Background. Coronary artery steal of collateral blood flow has been demonstrated for many vasodilators, including isoflurane, the most commonly used inhalational anesthetic agent in the United States. It has been postulated that patients with steal-prone anatomy (total occlusion of one coronary artery that is supplied distally by collateral flow from another coronary artery with a (50% stenosis) may be particularly at risk for the development of intraoperative myocardial ischemia when an anesthetic with a vasodilator property is being administered.Methods. We evaluated the risk of myocardial ischemia under isoflurane anesthesia (vs. a high dose narcotic technique using sufentanil) using continuous intraoperative electrocardiography and transesophageal echocardiography in patients with and without steal-prone anatomy undergoing coronary artery bypass graft surgery.Results. Sixty-two (33%) of the 186 patients had steal-prone anatomy: in 5 (8%) the collateral-supplying vessel was ≥50% to 69% stenosed, in 24 (39%) it was ≥70% to 89% stenosed and in 33 (53%) it was ≥90% stenosed. The iscidence of ischemia (trsnsesophageal echocardiography or intraoperative electrocar-diography, or both) was similar in patients with and without steal-prone coronary anatomy (18 [29%] of 62 patients vs. 39 [31%] of 124 patients, p = 0.87, 95% confidence interval = -0.13 to 0.17). The incidence of intraoperative ischemia was similar in patients who received isoflurane or sufentanil anesthesia (20 [32%] of 62 patients vs. 37 [30%] of 124 patients, p = 0.87). Use incidence of tachycardia and hypotension was low (increases in heart rate = 9.8%, and decreases in systolic blood pressure = 10.8% of total monitoring time during the prebypass period compared with preoperative baseline values). The incidence of adverse cardiac outcome was similar in patients with and without preoperative steal-prone coronary anatomy (4 [7%] of 62 patients vs. 14 [11%] of 124 patients, p = 0.53).Conclusions. These findings demonstrate that under strict hemodynamic control the presence of steal-prone anatomy does not confer an increased risk in the development of intraoperative myocardial ischemia.

Do plasma catecholamines influence microcirculatory blood flow in cardiac surgery patients?

To investigate whether plasma catecholamines influence blood flow on the microcirculatory level, forehead and forearm skin blood flow was measured by a two-channel laser Doppler blood flux monitor in 50 patients undergoing aortocoronary bypass grafting. Macrohaemodynamics, plasma viscosity, and skin temperatures were additionally monitored. Plasma catecholamines (adrenaline [AD] and noradrenaline [NOR] ) were determined using high-pressure liquid chromatography (HPLC) from arterial blood samples. In the prebypass period, blood concentrations of both catecholamines increased slightly showing a wide range of values (AD ranging from 3 to 955 pg/ml; NOR ranging from 27 to 5326 pg/ml). In spite of the tremendous increase in plasma catecholamines before and after bypass, laser Doppler flow (LDF) remained almost stable in this period. Neither LDF nor macrocirculatory parameters were correlated to plasma catecholamines. Cardiopulmonary bypass (CPB) resulted in a significant increase in catecholamines (AD ranging from 80 to 2480 pg/ml; NOR ranging from 188 to 9898 pg/ml). Although haematocrit and plasma viscosity were significantly reduced during CPB, LDF decreased in comparison to baseline values (LDF forehead: -25%; LDF forearm: -35%) ( p&lt;0.05). It is concluded that plasma catecholamine levels were markedly changed during cardiac surgery showing a wide range of concentrations. Microcirculatory flow assessed by laser Doppler remained almost unaffected by these alterations and was not correlated to AD or NOR plasma concentrations. However, during CPB a significant increase in catecholamines can contribute to the risk of microperfusion abnormalities which can be assessed by laser Doppler technique.

The effect of administering or withholding dextrose in pre-bypass intravenous fluids on intraoperative blood glucose concentrations in infants undergoing hypothermic circulatory arrest

Thirty-six fasted infants under 1 year of age who were scheduled for elective cardiac surgery using hypothermic bypass with circulatory arrest were randomized to receive a lactated Ringer's (LR) solution (group I) or a LR with 5% dextrose solution (group II) in the pre-bypass period. Marked increases in blood glucose concentrations were found following institution of bypass and circulatory arrest in the children in both groups. There was no correlation between the amount of dextrose infused in the pre-bypass period and the presence of hyperglycemia following institution of bypass. A single patient in group I was hypoglycemic (blood glu cose <30 mg/dL) on the initial glucose determination and the blood glucose did not increase during the pre-bypass period. Elimination of dextrose from the parenteral fluids given before bypass will not eliminate hyperglycemia following institution of bypass: however, it may expose pediatric patients to the risks of hypoglycemia before bypass.

Coronary artery bypass grafting using two different anesthetic techniques: Part I: Hemodynamic results

Hemodynamic changes were studied during two different anesthetic techniques in 54 patients undergoing coronary artery bypass grafting (CABG). All patients had normal to moderately impaired left ventricular function and were randomly assigned to two groups. In 27 patients, high thoracic epidural analgesia (TEA) with bupivacaine 0.375% plus sufentanil 1:200,000 (ie, 5 μ/mL) was used in combination with general anesthesia with midazolam/N 20; in the other 27 patients, general anesthesia (GA) with midazolam and sufentanil was used. After induction of epidural analgesia, heart rate and mean arterial pressure (MAP) decreased. Changes in cardiac index, systemic vascular resistance, and pulmonary capillary wedge pressure were not observed, whereas the stroke volume index increased significantly. After induction of intravenous anesthesia MAP decreased (20%) in both groups. During the pre-bypass period, metaraminol was used in 7 of 27 patients in the GA group and in 5 of 27 patients in the TEA group to treat hypotension. Inotopic drugs were used in 5 patients in the GA group and in none in the TEA group to treat a low CO. Ten GA patients and 4 TEA patients developed hypertension after sternal spread and the GA patients required more nitroprusside. Four GA patients developed electrocardiographic evidence of prebypass ischemia and, therefore, more nitroglycerin was needed for treating myocardial ischemia. More sodium nitroprusside was needed in the GA group during cardiopulmonary bypass (CPB) and the post-bypass period to treat hypertension with a high SVR. In conclusion, hemodynamic stability was more pronounced in the TEA than the GA group before and after CPB.

Coronary artery bypass grafting using two different anesthetic techniques: Part 3: Adrenergic responses

Twenty patients were studied during and after coronary artery bypass grafting (CABG). The patients were randomly assigned to two groups. In 10 patients, intraoperative general anesthesia (GA) was based on a combination of intravenous (IV) sufentanil and midazolam. In 10 other patients, thoracic epidural analgesia (TEA) with 0.375% bupivacaine plus sufentanil, 1:200,000 (5 μ/mL), and intraoperative GA with midazolam/N 2O were used. During the prebypass period, lower heart rates (HR), less variability in mean arterial pressure (MAP), and systemic vascular resistance (SVR) was accompanied by less variability in plasma norepinephrine (NE) concentrations in the TEA group. Although no differences were observed between the groups in perfusion pressure and the amount of vasoactive drugs used during the bypass period, variability in SVR was less in the TEA group. This was accompanied by less increase in NE and less variability in epinephrine (E) plasma concentrations. However, cortisol (Co) release was higher during this period in the TEA group. Weaning from bypass was accompanied by higher MAP and SVR in the TEA group at a lower HR, whereas no differences were observed in the E, NE, and Co plasma concentrations between the groups. During the first and second postoperative days, better pain relief and lower E and Co plasma concentrations were found in the TEA group It can be concluded that better hemodynamic stability during the prebypass and bypass periods was accompanied by less E and NE release during these periods. Co release in the TEA group was higher during the bypass period. Weaning from bypass was characterized by better hemodynamics in the TEA group. Better postoperative pain relief was accompanied by less E and Co release in the TEA group.