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Biomedical subjects

B Kleinman

Publications and source records attributed to B Kleinman.

At least 37 records · Page 2Linked to original sources
PubMed1992

Myocardial metabolism and adaptation during extreme hemodilution in humans after coronary revascularization.

OBJECTIVE: This study was designed to evaluate the oxygen transport adjustments and myocardial metabolic adaptation that occurs with different levels of hemodilution during normothermia after cardiopulmonary bypass. DESIGN: Prospective, nonrandomized study. SETTING: Operating room in a university hospital. PATIENTS: Eight patients with ejection fractions (> 40%) undergoing elective coronary artery bypass grafting. METHODS: Before the institution of cardiopulmonary bypass, blood was withdrawn from patients to a target hematocrit of 15%. After coronary artery bypass grafting, a catheter was inserted directly into the coronary sinus. After the patients were rewarmed to 37 degrees C, they were weaned from cardiopulmonary bypass. Hemodynamic indices were measured, as well as measurements of myocardial oxygen consumption (VO2) and myocardial metabolism (lactate extraction and coronary sinus hypoxanthine). Measurements were made at three different hematocrit values: 15%, 20%, and 25%. Hematocrit was increased by autologous blood transfusion. MEASUREMENTS AND MAIN RESULTS: The three levels of hemodilution (hematocrit: 17.4 +/- 3.4%; 23.0 +/- 3.7%; 27.8 +/- 4.8%) were significantly different from baseline (hematocrit 37 +/- 2.6%; p < .05). Oxygen delivery, which increased with autologous transfusion, exceeded 350 mL/min/m2 at each level of dilution. The myocardial VO2 increased significantly after autologous transfusion compared with the most dilute condition (7.0 +/- 3.7 mL/min at hematocrit 17.4% vs. 11.2 +/- 4.8 mL/min at hematocrit 23.0% and 12.4 +/- 4.0 mL/min at hematocrit 27.8%). This transfusion-induced increase was also true of myocardial oxygen extraction. Lactate extraction and hypoxanthine release were normal and unchanged at each level of hemodilution. Systemic oxygen extraction ratio increased with hemodilution and decreased with autologous transfusion. CONCLUSIONS: Hemodilution to a hematocrit of approximately 15% is tolerated in anesthetized humans after coronary artery bypass surgery. There was no evidence of myocardial ischemia, as demonstrated by absence of S-T depression on the electrocardiogram, lactate extraction, or hypoxanthine release. In selected patients, postoperative transfusion may be based on systemic physiologic end-points, such as oxygen extraction ratio, rather than set hematocrit values.

Blood Transfusion, Autologous↗
PubMed1991

Cardiovascular adjustments and gas exchange during extreme hemodilution in humans.

OBJECTIVE: To examine the cardiovascular adjustments and pattern of gas exchange that occur during hemodilution. DESIGN: Nonrandomized prospective study. SETTING: Operating room in a university hospital. PATIENTS: Seven patients undergoing elective aortocoronary artery bypass surgery. INTERVENTIONS: Before initiating cardiopulmonary bypass, the patients' hematocrit levels were decreased to approximately 15%. This hemodilution was done by removing a sufficient amount of autologous blood from the aortic cannula and replacing it with a sufficient amount of crystalloid solution. After the discontinuation of cardiopulmonary bypass, measurements were made at a hematocrit of approximately 15%. Then, after autologous blood infusion, measurements were made at a hematocrit of 20%, followed by more blood infusion to approximately 25% with repeat measurements. MEASUREMENTS AND MAIN RESULTS: The following measurements were made before hemodilution and then at all three levels of hemodilution: heart rate, mean arterial pressure (MAP), right atrial pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, and cardiac output. From these measurements, the following derived variables were calculated: cardiac index, systemic vascular resistance, and pulmonary vascular resistance. From measurements of arterial oxygen content, mixed venous oxygen content, and cardiac output, intrapulmonary shunt (Qsp/Qt), oxygen uptake (VO2), oxygen extraction ratio, and oxygen delivery (DO2) were derived. The MAP was lowest (57 +/- 3 [SD] vs. 92 +/- 3 mm Hg) at the lowest hematocrit. The cardiac index was highest (4.0 +/- 0.3 vs. 2.3 +/- 0.6 L/min.m2) at the lowest hematocrit. DO2 was lowest at the lowest hematocrit but VO2 remained constant at all levels of hematocrit. The oxygen extraction ratio increased as hematocrit decreased. With progressive increases in hematocrit, DO2 increased and Qsp/Qt decreased. CONCLUSIONS: The data suggest that, during hemodilution, tissue autoregulation of VO2 and utilization are not impaired, but gas exchange function (Qsp/Qt) is impaired.

Blood Pressure↗
PubMed1990

Effect of opening the pericardium on right ventricular hemodynamics during cardiac surgery.

The impact of the pericardium on right ventricular performance in the presence of normal filling pressures was evaluated using a rapid response RVEF thermodilution pulmonary artery catheter and TEE. In eight patients with normal right coronary arteries undergoing coronary artery bypass surgery, hemodynamic measurements revealed increased right ventricular end-diastolic and end-systolic volumes with diminished RVEF after opening the pericardium. In eight additional patients with right coronary artery disease, directionally similar changes in right ventricular volume were seen. Ejection fraction, however, was unchanged possibly due to altered right ventricular compliance. Echocardiogram evaluation of right ventricular area changes in patients with compromised right coronary systems corresponded to ejection fraction determinations obtained with thermodilution technique.

Cardiac Surgical Procedures↗
PubMed1990

Permeability pulmonary edema following lung resection.

The etiology of edema associated with pulmonary resection was investigated in five patients during the immediate postoperative period. Three patients received pneumonectomy while two patients had one lobe resected. All patients suffered from severe respiratory distress and had x-ray evidence of diffuse interstitial pulmonary edema within 12 hours of surgery. Hemodynamic data were obtained with radial and pulmonary artery catheters. Edema fluid was obtained along with blood samples for simultaneous determination of protein and albumin content. All patients studied had normal or high cardiac output, normal cardiac filling pressures, and edema fluid protein to serum protein ratio of 0.6 or greater suggestive of permeability changes contributing to edema fluid accumulation. Calculated shunt fraction exceeded 25 percent in all patients. Pulmonary edema has been noted in patients following pulmonary resection in the early postoperative period. In patients reviewed here, two factors appeared to be significant. First is an increase in pulmonary capillary pressure associated with passage of a normal to high cardiac output in a reduced volume pulmonary vascular bed. The second factor, as demonstrated by protein content in the edema fluid, is injury to the alveolar capillary membrane.

Blood Proteins↗
PubMed1989

Dynamic response of the ROSE damping device.

Methods used in clinical practice to increase the damping of a transducer hydraulically coupled to an intraarterial blood-pressure monitoring system often decrease the undamped natural frequency of the system. This leads to spuriously high systolic and low diastolic pressure readings. The ROSE damping device is being marketed as a possible solution to the problem. We tested the dynamic response of three different catheter systems, with various pressure-tubing lengths of 1 to 7 feet (30.5 to 213.4 cm), with and without the ROSE damping device. The device was able to substantially increase damping and at the same time maintain the undamped natural frequency. Typically it increased the damping coefficient from a minimum of 0.17 +/- 0.01 to a minimum of 0.33 +/- 0.01, while never significantly decreasing the undamped natural frequency. In testing a sample of 25 devices we did observe, however, a wide variability in damping characteristics among different devices. Damping coefficients ranged between 0.19 and 1.20.

Blood Pressure Determination↗
PubMed1989

Understanding natural frequency and damping and how they relate to the measurement of blood pressure.

The model that describes the physical behavior of a fluid-filled catheter-transducer blood pressure monitoring system is a simple mass-spring system. When the mass is displaced and then released, there results a characteristic motion called simple harmonic motion. The full description of this motion requires defining the concepts of undamped and damped natural frequency, as well as of damping itself. Once these concepts are defined and the mass-spring system clearly understood, their relevance to recording blood pressure measurement by fluid-filled catheters is explained. The apparent paradox of how damping can affect undamped natural frequency is clarified. Finally, impedance matching is explained in the context of how some damping devices work. Detailed mathematical proofs are relegated to an appendix.

Blood Pressure Determination↗
PubMed1989

The value to the anesthesia-surgical care team of the preoperative cardiac consultation.

A retrospective analysis of 202 consultations for preoperative cardiology evaluation was conducted. The most common problems generating the consultation were: (1) abnormal electrocardiogram, 45 patients; (2) chest pain, 36 patients; (3) history of myocardial infarction, 27 patients; (4) dysrhythmia, 25 patients; and (5) hypertension, 23 patients. The most common diagnoses by the consultants were: (1) arteriosclerotic heart disease, 46 patients; (2) angina, 20 patients; and (3) hypertension, 40 patients. Mitral valve prolapse was the most common valvular disease (18 patients). Of the consultation requests, 108 asked for an evaluation; 79 asked for a "clearance"; 9 did not specifically ask for anything; and 6 asked a highly specific question. Most consultations provided a diagnosis (96%), addressed the problem (80%), and provided logical recommendations (96%). A minority of the consultations "cleared" a patient (28%), provided for follow-up care (41%), or suggested intraoperative monitoring techniques (41%). Out of the 189 patients who eventually had surgery, 137 patients had no change in their preoperative therapy, while 52 patients had a change in preoperative therapy. There was no difference in the incidence of complications between these two groups. An important finding was that 15% of the study group (31 patients) had disease processes (hypertension and angina) that were newly diagnosed by the consultant or felt to be not adequately treated before the consultation. It is concluded that few requesting anesthesiologists and surgeons ask for clarification of a specific problem, while most responses from the cardiology consultants provided necessary information. In addition, the preoperative cardiac consultation was found to identify medical conditions requiring long-term care and follow-up.

Adolescent↗
PubMed1988

Reduction in mortality from cardiac causes in goldman class IV patients.

In 1977, Goldman et al evaluated cardiac patients for non-cardiac operations and showed a high incidence of cardiac death in high-risk cardiac patients (Goldman class IV). The present study was designed to prospectively evaluate the incidence of cardiac death as well as overall mortality in 49 patients belonging to Goldman class IV at the present time. Four patients of 49 (8.2%) died of cardiac causes, and seven other patients died of non-cardiac causes. Thus, the overall mortality rate was 22.4% (11/49). There has been a marked reduction in cardiac mortality from 56% in Goldman et al's 1977 data to 8.2% in the present data. All of the developments and advances in patient care over the past 10 years probably contributed to this reduction in mortality from cardiac causes.

Adult↗
PubMed1986

Qualitative evaluation of coronary flow during anesthetic induction using thallium-201 perfusion scans.

Qualitative distribution of coronary flow using thallium-201 perfusion scans immediately postintubation was studied in 22 patients scheduled for elective coronary artery bypass surgery. Ten patients received a thiopental (4 mg/kg) and halothane induction. Twelve patients received a fentanyl (100 micrograms/kg) induction. Baseline thallium-201 perfusion scans were performed 24 h prior to surgery. These scans were compared with the scans performed postintubation. A thallium-positive scan was accepted as evidence of relative hypoperfusion. Baseline hemodynamic and ECG data were obtained prior to induction of anesthesia. These data were compared with the data obtained postintubation. Ten patients developed postintubation thallium-perfusion scan defects (thallium-positive scan), even though there was no statistical difference between their baseline hemodynamics and hemodynamics at the time of intubation. There was no difference in the incidence of thallium-positive scans between those patients anesthetized by fentanyl and those patients anesthetized with thiopental-halothane. The authors conclude that relative hypoperfusion, and possibly ischemia, occurred in 45% of patients studied, despite stable hemodynamics, and that the incidence of these events was the same with two different anesthetic techniques.

Anesthesia↗
PubMed1983

Effects of low-dose dobutamine on coronary hemodynamics, myocardial metabolism, and anginal threshold in patients with coronary artery disease.

Fourteen patients with coronary artery disease and normal or near-normal left ventricular function were studied at rest and during atrial pacing until the occurrence of angina (12 patients) before and during infusion of dobutamine (3.80 +/- 0.45 micrograms/kg/min). At rest, during the infusion, three patients developed chest pain, mean ST segment depression increased from 0.02 to 0.08 mV (p less than .001), and myocardial lactate extraction fell from +17.5% to -1.4% (p less than .05). These ischemic changes were associated with significant increases in arterial systolic pressure (134 to 149 mm Hg), heart rate (79 to 91 beats/min), coronary sinus flow (89 to 113 ml/min), and myocardial oxygen consumption (10.8 to 13.5 cc/min). In contrast, during atrial pacing, dobutamine did not reduce the pacing threshold or further increase myocardial oxygen consumption or ST segment changes; however, arterial mean and diastolic pressures were significantly lower with pacing during dobutamine infusion compared with control pacing. In the absence of heart failure, dobutamine in low doses can cause myocardial ischemia in patients with coronary artery disease. The absence of increased ischemia from dobutamine during pacing may reflect reversal of pacing-induced ventricular dysfunction.

Aged↗