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Biomedical subjects

J G Reves

Publications and source records attributed to J G Reves.

At least 127 records · Page 7Linked to original sources
PubMed1989

The effects of deep hypothermic cardiopulmonary bypass and total circulatory arrest on cerebral blood flow in infants and children.

Cardiopulmonary bypass management in infants and children involves extensive alterations in temperature, hemodilution, and perfusion pressure, with occasional periods of circulatory arrest. Despite the use of these biologic extremes of temperature and perfusion, their effects on cerebral blood flow are unknown. This study was designed to examine the relationship of mean arterial pressure and nasopharyngeal temperature to cerebral blood flow during deep hypothermic cardiopulmonary bypass (18 degrees to 22 degrees C) with and without periods of total circulatory arrest. Cerebral blood flow was measured before, during, and after deep hypothermic cardiopulmonary bypass using xenon clearance techniques in 25 children, aged 2 days to 60 months. Fourteen patients underwent repair with circulatory arrest. There was a highly significant correlation of cerebral blood flow with temperature during cardiopulmonary bypass (p = 0.007). During deep hypothermic bypass there was a significant association between cerebral blood flow and mean arterial pressure (p = 0.027). In infants undergoing repair with deep hypothermia alone, cerebral blood flow returned to prebypass levels in the rewarming phase of bypass. However, in patients undergoing repair with circulatory arrest, no significant increase in cerebral blood flow during rewarming or even after bypass was observed (p = 0.01). These data show that deep hypothermic cardiopulmonary bypass significantly decreases cerebral blood flow because of temperature reduction. Under conditions of deep hypothermia, cerebral pressure-flow autoregulation is lost. This study also demonstrates that cerebral reperfusion after deep hypothermia is impaired if the patient is exposed to a period of total circulatory arrest.

Blood Pressure↗
PubMed1989

Effects of cardiopulmonary bypass on cerebral blood flow in neonates, infants, and children.

Cardiopulmonary bypass (CPB) management in neonates, infants, and children requires extensive alterations in temperature, pump flow rate, and perfusion pressure, with occasional periods of circulatory arrest. The effect of these alterations on cerebral blood flow (CBF) are unknown. This study was designed to determine the relation of temperature and mean arterial pressure to CBF during hypothermic CPB (18 degrees-32 degrees C), with and without periods of total circulatory arrest. CBF was measured before, during, and after hypothermic CPB with xenon-clearance techniques in 67 pediatric patients, aged 1 day-16 years. Patients were grouped based on different CPB techniques: group A, repair during moderate-hypothermic bypass at 25 degrees-32 degrees C; group B, repair during deep-hypothermic bypass at 18 degrees-22 degrees C; and group C, repair with total circulatory arrest at 18 degrees C. There was a significant correlation of CBF with temperature during CPB. CBF significantly decreased under hypothermic conditions in all groups compared with prebypass levels under normothermia. In groups A and B, CBF returned to baseline levels in the rewarming phase of CPB and exceeded baseline levels after bypass. In group C, no significant increase in CBF was observed during rewarming after total circulatory arrest (32 +/- 12 minutes) or after weaning from CPB. During moderate-hypothermic CPB (25 degrees-32 degrees C), there was no association between CBF and mean arterial pressure. However, during deep-hypothermic CPB (18 degrees-22 degrees C), there was an association between CBF and mean arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

The effect of age on cerebral blood flow during hypothermic cardiopulmonary bypass.

Cerebral blood flow was measured in 20 patients by xenon 133 clearance methodology during nonpulsatile hypothermic cardiopulmonary bypass to determine the effect of age on regional cerebral blood flow during these conditions. Measurements of cerebral blood flow at varying perfusion pressures were made in patients arbitrarily divided into two age groups at nearly identical nasopharyngeal temperature, hematocrit value, and carbon dioxide tension and with equal cardiopulmonary bypass flows of 1.6 L/min/m2. The range of mean arterial pressure was 30 to 110 mm Hg for group I (less than or equal to 50 years of age) and 20 to 90 mm Hg for group II (greater than or equal to 65 years of age). There was no significant difference (p = 0.32) between the mean arterial pressure in group I (54 +/- 28 mm Hg) and that in group II (43 +/- 21 mm Hg). The range of cerebral blood flow was 14.8 to 29.2 ml/100 gm/min for group I and 13.8 to 37.5 ml/100 gm/min for group II. There was no significant difference (p = 0.37) between the mean cerebral blood flow in group I (21.5 +/- 4.6 ml/100 gm/min) and group II (24.3 +/- 8.1 ml/100 gm/min). There was a poor correlation between mean arterial pressure and cerebral blood flow in both groups: group I, r = 0.16 (p = 0.67); group II, r = 0.5 (p = 0.12). In 12 patients, a second cerebral blood flow measurements was taken to determine the effect of mean arterial pressure on cerebral blood flow in the individual patient. Changes in mean arterial pressure did not correlate with changes in cerebral blood flow (p less than 0.90). We conclude that age does not alter cerebral blood flow and that cerebral blood flow autoregulation is preserved in elderly patients during nonpulsatile hypothermic cardiopulmonary bypass.

Aged↗
PubMed1988

Anesthetic implications for the management of patients with acute myocardial infarction: a matched cohort study of patients undergoing emergency myocardial revascularization.

Emergency coronary artery bypass grafting (CABG) is advocated as a treatment of acute myocardial infarction (AMI). To attempt to define anesthetic management problems in this patient group, a retrospective study was conducted comparing the perioperative courses of 23 patients undergoing emergency CABG during AMI with 23 elective patients, individually matched for gender, operating surgeon, ejection fraction, and aortic crossclamp time. The 23 AMI patients were anesthetized 5.98 +/- 3.0 (range 1.5 to 11.0) hours after the onset of chest pain. Anesthetic agents were similar for both groups. Induction of anesthesia was well tolerated by AMI patients. Tolerance of cardioplegic arrest was impaired in the AMI group as evidenced by the sharp increase in frequency of inotropic support required to discontinue bypass in the AMI group compared to elective patients (12/23 v 3/23; P less than .005). Fifteen AMI patients who received preoperative streptokinase had greater postoperative bleeding. Three AMI patients died postoperatively. The number of patients requiring prolonged postoperative ventilation and extended ICU care was higher in the AMI group. It is concluded that patients undergoing emergency CABG during AMI represent a greater risk than elective patients. They have a higher incidence of myocardial dysfunction following cardioplegic arrest during bypass. Those who receive preoperative thrombolytic therapy exhibit greater bleeding tendencies.

Anesthesia, Intravenous↗
PubMed1988

Use of the Walton-Brodie strain gauge arch to measure contractile force during anaesthesia.

The Walton-Brodie strain gauge arch is an instrument that quantitatively measures CF. Like many methods, the strain gauge arch is affected by loading conditions and heart rate. Nevertheless, this methodology, when properly used, has proved very useful in describing the direct action of anaesthetic drugs. Knowledge from strain gauge arch use has stimulated research to explain the negative inotropic effect of anaesthetics and helped clinicians understand the cardiovascular effects of drugs that they may wish to use.

Anesthesia↗
PubMed1988

Esmolol and left ventricular function in the awake dog.

Hypotension has been the most frequently reported adverse reaction associated with infusion of the beta 1-adrenergic receptor antagonist esmolol. In some patients, this hypotension has apparently occurred independent of reduction in heart rate or systemic vascular resistance, suggesting decreased stroke volume. In the present study, the preload recuitable stroke work area (PRSWA) model was used to evaluate the negative inotropic effects of esmolol in nine chronically instrumented awake dogs. Left ventricular (LV) transmural pressure and minor axis diameter were measured by micromanometers and sonomicrometry, respectively. Vena caval occlusions were performed so that an analog of stroke work (area within LV transmural pressure-diameter loop) could be measured over a range of preloading conditions during esmolol infusions of 0, 100, 300, 1000, and 3000 micrograms/kg-1.min-1 (n = 9), and at 15 and 30 min after termination of esmolol (n = 8). The linear relationship between stroke work and end-diastolic diameter was characterized for each caval occlusion by a slope and x-intercept. PRSWA was calculated for each caval occlusion as slope/two times the square of the difference between x-intercept and the largest end diastolic diameter observed in the study of a particular dog. Heart rate was different from control (91 +/- 4) only at the highest esmolol dose (127 +/- 4). LV peak positive dP/dt, minor axis ejection shortening, stroke work, and PRSWA were depressed from control at esmolol doses greater than or equal to 300 micrograms.kg-1.min-1. All parameters except dP/dt recovered within 30 min following termination of esmolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1988

Myocardial tolerance to total ischemia in the dog anesthetized with halothane or isoflurane.

Myocardial tolerance to total ischemia was compared in animals anesthetized with halothane or isoflurane by measuring the time required for development of cardiac rigor in the absence of coronary circulation or wall stress. Sixteen dogs, eight in each group, were anesthetized with equally potent inspired concentrations of either halothane (2 MAC) or isoflurane (2 MAC), intubated, and ventilated. Thirty minutes later, the heart was rapidly excised. A left ventricular slab was prepared and maintained at 37 degrees C. A portion of each slab was placed in a compressibility gauge that detects rigor onset by an abrupt increase in resistance to tissue deformation. Subendocardial tissue pressure was continuously measured in a second slab using needle-tipped Millar pressure transducers. A third slab was used for intermittent tissue sampling and HPLC assay of high-energy nucleotide levels. There were no differences in pre-ischemic heart rate, mean arterial pressure, glucose, lactate, PO2, PCO2, pH, plasma epinephrine, or norepinephrine levels between the two groups. The onset of rigor as measured by the compressibility gauge was delayed in the halothane group (68 +/- 7.2 vs. 60 +/- 5.0 min; P less than .05). Tissue ATP and ADP levels declined throughout the period of ischemia, with a trend towards preservation in the halothane group. The data show that myocardial tolerance to total normothermic ischemia is improved in animals anesthetized with halothane compared to isoflurane, independent of the effects on hemodynamics or collateral coronary circulation.

Adaptation, Physiological↗
PubMed1988

alpha 1-Adrenergic responsiveness during coronary artery bypass surgery: effect of preoperative ejection fraction.

Elevated catecholamines and beta-adrenergic receptor hyporesponsiveness (or desensitization) have been demonstrated in failing human myocardium, but the role of the alpha-adrenergic receptor remains unclear. The authors tested the hypothesis that alpha 1-adrenergic responsiveness decreases in patients with impaired ventricular function undergoing coronary artery revascularization. Impaired ventricular function was defined prospectively by left ventricular ejection fraction less than or equal to 40% (group I, n = 12), and normal ventricular function by ejection fraction greater than 40% (group II, n = 22). Phenylephrine (Phe) pressor dose-response curves were established prior to anesthesia, during fentanyl anesthesia, and during fentanyl anesthesia plus hypothermic cardiopulmonary bypass at the time of aortic cross-clamp (anes + CPB/AXC). Polynomial regression of the Phe dose response curve estimated the Phe dose required to increase mean arterial blood pressure 20%, designated PD20. Although pre-anesthesia PD20 and anes + CPB/AXC PD20 values were not affected by ejection fraction, significant differences in PD20 (P less than 0.05) between groups occurred during fentanyl anesthesia (group I = 2.28 +/- 1.60 micrograms.kg-1, group II 1.57 +/- 0.98 micrograms.kg-1; mean +/- SD). Anes + CPB/AXC was associated with a significant reduction in PD20 in both groups compared with pre-anesthesia (P less than 0.01). Our results suggest impairment of alpha 1-adrenergic responsiveness occurs during fentanyl anesthesia in patients with ejection fractions less than or equal to 40% (evidenced by greater PD20 values). Although this impairment may be due to altered Phe pharmacokinetics, these results also support the possible existance of alpha 1-adrenergic receptor desensitization in this group. Reduction in PD20 during anes + CPB/AXC in all patients points to more powerful effects than fentanyl anesthesia alone; such influencing effects may include hemodilution, hypothermia, elevated plasma catecholamines, exclusion of the pulmonary circulation, or altered Phe pharmacokinetics.

Anesthesia, Intravenous↗
PubMed1988

Cognitive dysfunction after coronary artery bypass surgery: a case-controlled study.

Twenty-two patients screened from a sample of 391 having coronary artery bypass grafting (CABG) showed significant declines on the Mini-Mental State Examination (MMSE) administered preoperatively and four days postoperatively. The MMSE is a 30-point cognitive function screening instrument for dementia and delirium. These patients were compared with 22 matched control subjects who exhibited intact cognitive function postoperatively. The study assessed the association between postoperative cognitive dysfunction and socioeconomic status, potential effects of selected surgical/anesthetic factors, and preoperative anxiety and depression (Zung Anxiety and Center for Epidemiologic Studies-Depression [CES-D] self-rating scales). The results indicate that a higher preoperative level of depression reported on the CES-D (mean score of study patients 22.1 versus 12.7 for controls) is significantly associated with the development of postoperative cognitive dysfunction (P less than .01). The educational and occupational levels of study patients were significantly below those of controls (P less than .01, P less than .02). Occurrence of a postoperative complication was the only surgical/anesthetic factor found to be significantly associated with cognitive dysfunction (P less than .01). These findings suggest that preoperative depression significantly increases the risk for immediate postoperative cognitive dysfunction, and that lower socioeconomic status may confer greater risk for postoperative cognitive morbidity.

Adult↗
PubMed1988

Current prognosis of ischemic mitral regurgitation. Implications for future management.

Ischemic mitral regurgitation is a serious and increasingly common clinical disorder, but at present, little is known of the associated prognostic implications, especially in specific therapeutic subgroups. Over a 6.5-year period beginning January 1, 1981, postinfarction mitral regurgitation was demonstrated ventriculographically in 2,343 (19%) of 11,748 patients having significant coronary artery disease defined at cardiac catheterization. Moderate or severe regurgitation was observed in 381 (3%), and among these patients, four treatment groups were defined: Group I (medical, n = 165), Group II (reperfusion, n = 63), Group III (coronary artery bypass only, n = 94), and Group IV (valve replacement or repair in addition to coronary bypass, n = 59). Multivariable regression analysis of survival data in the overall population and in specific treatment groups was performed with the Cox proportional hazards model. Defined and undefined selection biases precluded formal quantitative survival comparisons among some treatment groups; however, unadjusted and adjusted survival analysis for each group revealed several interesting concepts. First, increasing severity of mitral regurgitation had a progressively negative impact on survival prognosis regardless of treatment. Congestive heart failure, the number of associated disorders, acute presentation requiring cardiac care unit admission, diminished ejection fraction, increasing coronary obstruction, and advanced age all worsened prognosis (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Beneficial effects of endotracheal extubation on ventricular performance. Implications for early extubation after cardiac operations.

Early endotracheal extubation has been shown to be a safe postoperative management option in patients having cardiac operations. However, few objective data exist on the response of ventricular performance to early termination of controlled ventilation. Seven patients undergoing routine elective coronary artery bypass grafting or adult repair of atrial septal defect were studied after intraoperative placement of left ventricular micromanometers, left ventricular minor axis dimension crystals, and left atrial and intrapleural pressure catheters. Physiologic data were recorded intraoperatively, during controlled mandatory ventilation in the intensive care unit, and during spontaneous respiration immediately after extubation. Extubation to spontaneous breathing was associated with a significant decline in intrapleural pressure and significant increases in left ventricular end-diastolic diameter, ejection diameter shortening, stroke work, and cardiac output. The augmented left ventricular diastolic filling seemed to result from the fall in intrapleural pressure and perhaps from normalization of right ventricular afterload. The preload recruitable stroke work relationship showed that myocardial contractility remained constant after extubation, and ventricular function improved primarily because of increased preload associated with shifting of the capacitance blood volume toward the chest. Thus endotracheal extubation enhances cardiac performance after uncomplicated cardiac surgical procedures, and by this mechanism early extubation may be clinically beneficial as a routine adjunct to postoperative care.

Cardiac Output↗
PubMed1988

A clinical comparison of mitral valve repair versus valve replacement in ischemic mitral regurgitation.

Severe mitral regurgitation caused by acute myocardial infarction has been a particularly difficult management problem with disappointing clinical results. Over a 75-month period, ending March 31, 1987, 611 patients underwent mitral valve operations at Duke University Medical Center. Within this group, 55 patients had clearly defined ischemic mitral regurgitation, and 37 of these required emergency operations. Thirty-one of the 55 patients had isolated posterior papillary muscle dysfunction, nine had papillary muscle rupture, and 15 had severe ventricular dysfunction and generalized annular dilatation. Thirty-two patients were treated with primary mitral valve replacement, and 23 had mitral valve repair. In 18, repair was accomplished by a transventricular approach, combining the techniques of commissural annuloplasty, papillary muscle shortening or reimplantation, and infarct exclusion. Transventricular mitral valve repair proved to be safe, expeditious, and effective in restoring valve competence. Although the repair and replacement groups were similar with respect to all relevant baseline characteristics, improved operative survival was observed after valve repair, as compared to replacement, both for the overall group (p = 0.03) and for acute papillary muscle dysfunction (p = 0.05). These data suggest that a policy of predominant mitral valve repair, when appropriately applied in patients with ischemic mitral regurgitation, offers the potential for improving therapeutic results.

Cardiopulmonary Bypass↗
PubMed1987

Sufentanil disposition during cardiopulmonary bypass.

In order to investigate the ability of a computer-assisted continuous infusion (CACI) system to maintain constant plasma levels of sufentanil during cardiopulmonary bypass (CPB) using pharmacokinetic data derived from healthy surgical patients to determine the infusion rate, ten patients were anaesthetized with diazepam, enflurane and oxygen until ten minutes prior to the expected time of initiation of CPB. At that point, an infusion of sufentanil, aimed to reach a central compartment concentration of 5 ng.ml-1, was started via CACI. Plasma concentrations of sufentanil, haematocrit, total protein and albumin concentrations, and nasopharyngeal and CPB inflow temperatures were obtained at predetermined intervals before and up to 90 min after the initiation of CPB. Plasma concentrations of sufentanil reached 3.8 +/- 0.4 ng.ml-1 before CPB and approached the 5.0 ng.ml-1 set point (4.7 +/- 0.4 ng.ml-1) over the 90 min of CPB. In conclusion, our results show that it is possible to obtain stable plasma levels of sufentanil on CPB using a pharmacokinetically driven infusion scheme; however, our data suggest that use of such a system may lead to accumulation of drug during CPB.

Aged↗