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Biomedical subjects

T Pasch

Publications and source records attributed to T Pasch.

At least 73 records · Page 4Linked to original sources
PubMed1997

Effect of progressive haemodilution with hydroxyethyl starch, gelatin and albumin on blood coagulation.

We have compared the effects of progressive (30% and 60%) in vitro haemodilution with hydroxyethyl starch (HES), gelatin (GEL) and albumin (ALB) with haemodilution using 0.9% saline in 96 patients by thrombelastography. Haemodilution with HES, GEL and ALB significantly (P < 0.05) compromised coagulation time (k), angle alpha and maximal amplitude (MA), with HES having the most negative effect at 30% and 60% haemodilution (P < 0.05). Haemodilution with saline significantly affected all variables of blood coagulation and clot lysis measured by thrombelastography, resulting in an increased coagulability at 30% haemodilution. To specifically assess the intrinsic effect of plasma expander molecules on blood coagulation and clot lysis, we analysed the difference between saline diluted blood (same degree of haemodilution) and plasma expander diluted blood. Prolongation of reaction time (r) was found for HES at 30% and 60% haemodilution and for ALB at 60% haemodilution and an increase in clot lysis by HES, GEL and ALB became evident. We conclude that HES, GEL and ALB compromised blood coagulation, while the maximum effect was found with HES.

Adolescent↗
PubMed1997

Accuracy and clinical performance of a continuous intra-arterial blood-gas monitoring system during thoracoscopic surgery.

Accuracy and performance of the only currently available intra-arterial blood-gas monitoring system (Paratrend 7, PT7) were assessed in 23 patients during thoracoscopic surgery using one-lung ventilation. Over a wide range of values for arterial PO2 (6.1-61.1 kPa), PCO2 (4.1-9.5 kPa) and pH (7.19-7.50), 138 arterial blood-gas values obtained by PT7 were compared with corresponding in vitro laboratory blood-gas measurements. We found good clinical performance with the PT7 and good agreement between PT7 values and in vitro measurements for arterial PO2 (bias (1.96 SD) = 0.38 (9.52) kPa), PCO2 (0.31 (0.76) kPa) and pH (-0.017 (0.065)). Also, the bias for sequential changes between two, consecutive times was not significantly different from the ideal value of 0. We conclude that the PT7 is helpful in monitoring patients during thoracoscopy.

Adult↗
PubMed1997

Video-assisted thoracoscopic volume reduction surgery in patients with diffuse pulmonary emphysema: gas exchange and anesthesiological management.

Arterial blood gases were studied prospectively using continuous intraarterial blood gas monitoring during thoracoscopic volume reduction surgery (VRS) in 24 patients with advanced diffuse pulmonary emphysema. Additionally, the early postoperative course (48 h) of arterial blood gases was studied retrospectively. Twenty-six operations were performed using a combination of thoracic epidural and general anesthesia with left-sided double-lumen intubation for one-lung ventilation (OLV). Arterial blood gases were determined awake, during two-lung ventilation prior to surgery, during OLV (extreme values), and after tracheal extubation. Additionally, the extremes during the whole procedure were determined: avoiding excessive peak inspiratory pressures (26.4 +/- 7.0 cm H2O), minimum PaO2 was 77 +/- 39 mm Hg (mean +/- SD), maximum PaCO2 65 +/- 14 mm Hg (P < 0.0001 versus preoperative values), and minimum pHa 7.22 +/- 0.08 (P < 0.0001). One tension pneumothorax occurred during OLV. Immediate postoperative extubation was performed in 25 of 26 cases, reintubation was necessary in two cases. One patient with coronary artery disease died 36 h after surgery. Hypercapnia (maximum PaCO2 49 +/- 8 mm Hg, minimum pHa 7.37 +/- 0.04, P < 0.01) was still observed 48 h after surgery. These results demonstrate that adequate oxygenation can be preserved during OLV for VRS, but CO2 elimination is impaired. However, intraoperative hypercapnia and immediate postoperative tracheal extubation are well tolerated.

Adult↗
PubMed1996

Subtraction procedure for the registration of tissue perfusion with Doppler ultrasound.

Tissue perfusion, i.e., in muscles or parenchymatous organs, is of both physiological and pathophysiological interest. The measurement of tissue perfusion is an unsolved problem. The Doppler ultrasound method is well suited to this purpose. However, measurements using this technique may be disturbed by movements or vibrations such as heart motion, muscle trembling or vibration of the subsoil (i.e. the examination table). These interfering movements produce Doppler frequencies in the same frequency range as slowly flowing erythrocytes, causing artifacts to appear in the measured data. The goal of this project was to suppress such artifacts with the help of a subtraction procedure. The mathematical theory of this subtraction procedure and its implementation in a newly developed two channel Doppler system are presented. This system was successfully tested on a phantom which is able to generate flow and movement artifacts. Preliminary measurements in the forearms of volunteers showed that movement artifacts can be at least partially suppressed.

Adult↗
PubMed1996

Perioperative course and recovery after heparin-coated cardiopulmonary bypass: low-dose versus high-dose heparin management.

OBJECTIVE: To compare two heparin managements for a cardiopulmonary bypass (CPB) procedure with heparin-coated equipment. The hypothesis was that a lower heparin dose may reduce blood loss and homologous transfusion requirements and influence the speed of postoperative recovery. DESIGN: Prospective, randomized, and open study. SETTING: Operating room and intensive care unit in a university hospital. PARTICIPANTS: Twenty-four patients undergoing first-time elective coronary artery surgery. INTERVENTIONS: Heparin-coated CPB equipment (Duraflo II; Baxter-Bentley) was used in all patients. The study group (n = 12) received low-dose (100 IU/kg i.v. and 0 to 1,000 IU/L priming; target level of activated coagulation time [ACT] over 180 seconds during CPB; suction in a red cell washing device); and the control group (n = 12) received high-dose (300 IU/kg i.v. and 5,000 IU/L priming; ACT over 480 seconds; standard cardiotomy suction) heparin management. MEASUREMENTS AND MAIN RESULTS: ACT remained above 200 seconds after the initial heparin dose in the study group for the CPB duration up to 99 minutes. In 11 of 12 patients in the control group, additional heparin was required during CPB. Total doses of heparin and protamine (mean 8,017 v 50,508 IU and 83 v 325 mg, respectively; p < 0.0001), volume of homologous blood transfusion (median 600 v 1450 mL; p < 0.025), and blood products exposure (median 0.5 v 5.0 units/patients; p < 0.05) were significantly lower in the study group. Postoperative chest drainage showed a trend to lower volume loss (median 705 v 930 mL; p < 0.08) in patients managed with low-dose heparin. Oxygenator resistance during CPB, perioperative laboratory analyses (oxygen and metabolic data, hematocrit, platelet count, prothrombin, thrombin, activated partial thromboplastin time, fibrinogen, D-dimers, creatine kinase, and myocardial band of creatine kinase concentration), fluid balance, and the time periods required for extubation, stay in the intensive care unit, and hospital discharge were not different between the groups. There were no evidences of myocardial infarction in any of 24 patients, and all recovered after the procedure. CONCLUSION: Low-dose heparin management enabled uneventful procedures with heparin-coated CPB equipment, significantly decreased protamine and homologous blood requirements, but did not reduce chest drainage or influence the postoperative course and recovery in patients after coronary artery surgery.

Adult↗
PubMed1996

Radial artery tonometry: moderately accurate but unpredictable technique of continuous non-invasive arterial pressure measurement.

Radial artery tonometry provides continuous measurement of non-invasive arterial pressure (CNAP) by a sensor positioned above the radial artery. An inflatable upper arm cuff enables intermittent oscillometric calibration. CNAP was compared with invasive radial artery pressure recordings from the opposite wrist in 22 high-risk surgical patients with an inter-arm oscillometric mean arterial pressure difference < or = 10 mm Hg. Oscillometric, tonometric and invasive digital pressure values, and invasive and CNAP waveforms were obtained by the same instrument (Colin BP-508). Correlation coefficients (r) of invasive vs oscillometric values (n = 481 pairs) were 0.83, 0.90 and 0.92, and mean absolute errors of oscillometry were 7.6, 4.7, and 2.6 mm Hg for systolic, diastolic and mean arterial pressures, respectively. Correlation was poor for systolic (r = 0.80), diastolic (r = 0.77) and mean (r = 0.84) invasive vs CNAP values (n = 1375). Compared with oscillometry, mean absolute errors of 15.2, 10.9 and 9.4 mm Hg for systolic, diastolic and mean CNAP, respectively, were significantly (P < 0.001) higher. Mean prediction errors of CNAP, compared with invasive values, were -5.8 (SD 14.2) mm Hg for systolic, +7.2 (8.3) mm Hg for diastolic and +3.9 (8.8) mm Hg for mean arterial pressure. Individual patient accuracy of CNAP was assessed as good (individual prediction error < or = 5 (8) mm Hg and individual absolute error < or = 10 mm Hg) in seven patients, as acceptable (< or = 10 (12) and < or = 15 mm Hg) in 11 patients, and as inadequate in four of 22 patients. Individual accuracy of oscillometry was good or acceptable in all 22 patients. The trend in CNAP changes (difference between consecutive measurements) was sufficiently accurate during induction of anaesthesia, as only 47 (7.6%), 14 (2.3%) and 27 (4.4%) of 616 systolic, diastolic and mean CNAP values differed by more than 10 mm Hg of invasive pressure trends. We conclude that: intermittent oscillometry provides accurate arterial pressure monitoring; CNAP measurements offer a reliable trend indicator of pressure changes during induction of anaesthesia and may be considered an alternative to invasive pressure measurements, should arterial cannulation be difficult in an awake patient; and accuracy of absolute CNAP values is only moderate and unpredictable, thus radial artery tonometry should not replace invasive monitoring in high-risk patients during major surgical procedures.

Adult↗
PubMed1996

Hemodilution tolerance in elderly patients without known cardiac disease.

Hemodilution tolerance is not well defined in elderly patients. In 20 patients older than 65 yr and free from known cardiovascular disease, hemodynamic variables, ST segment deviation, and O2 consumption were determined prior to and after 6 and after 12 mL/kg isovolemic exchange of blood for 6% hydroxyethyl starch. The mean age of the patients was 76 +/- 2 yr (mean +/- SEM, range 66-88 yr). During hemodilution, hemoglobin decreased from 11.6 +/- 0.4 to 8.8 +/- 0.3 g/dL (P < 0.05). With stable filling pressures, cardiac index increased from 2.02 +/- 0.11 to 2.19 +/- 0.10 L.min-1.m-2 (P < 0.05) while systemic vascular resistance decreased from 1796 +/- 136 to 1568 +/- 126 dynes.s.cm-5 (P < 0.05) and O2 extraction increased from 28.0% +/- 0.9% to 33.0% +/- 0.8% (P < 0.05) resulting in a stable O2 consumption during hemodilution. No alterations in ST segments were observed in lead II during hemodilution. In lead V5, ST segment deviation became slightly less negative during hemodilution from -0.03 +/- 0.01 to -0.02 +/- 0.01 mV (P < 0.05). The moderate decrease in hemoglobin was fully compensated by both an increase in cardiac index and in O2 extraction. Electrocardiographic signs of myocardial ischemia were not observed in this population. In conclusion, isovolemic hemodilution to a hemoglobin value of 8.8 +/- 0.3 g/dL is well tolerated in elderly patients free from known cardiac disease at the ages of 65-88 yr.

Abdomen↗
PubMed1996

Hemodilution tolerance in patients with coronary artery disease who are receiving chronic beta-adrenergic blocker therapy.

Hemodilution tolerance is not well defined in patients with coronary artery disease receiving beta-adrenergic blockers chronically. Ninety patients scheduled for coronary artery bypass graft (CABG) surgery were randomized to a hemodilution (n = 60) and a control group (n = 30). During midazolam-fentanyl anesthesia, hemodynamic variables, ST segment deviation, and O2 consumption were determined prior to and after 6 and 12 mL/kg isovolemic exchange of blood for 6% hydroxyethyl starch. Hemoglobin decreased from 12.6 +/- 0.2 to 9.9 +/- 0.2 g/dL (mean +/- SEM, P < 0.05). With stable filling pressures, cardiac index increased from 2.05 +/- 0.05 to 2.27 +/- 0.05 L.min-1.m-2(P < 0.05) and O2 extraction from 27.4% +/- 0.6% to 31.2% +/- 0.7% (P < 0.05), resulting in stable O2 consumption. No alterations in ST segments were observed in leads II and V5 during hemodilution. Individual increases in cardiac index and O2 extraction were not linearly related to age and left ventricular (LV) ejection fraction (P = 0.841, P = 0.799). We conclude that isovolemic hemodilution to a hemoglobin value of 9.9 +/- 0.2 g/dL is well tolerated and fully compensated in patients with coronary artery disease receiving beta-adrenergic blockers chronically. Within the investigated ranges, the compensatory mechanisms during hemodilution are largely independent of age (35-81 yr) and LV ejection fraction (26%-83%).

Adrenergic beta-Antagonists↗
PubMed1995

Continuous non-invasive blood pressure monitoring by brachial artery displacement method in high-risk surgical patients.

Continuous non-invasive blood pressure (CNBP) measurements were compared to invasive radial artery pressure recordings in 26 patients with cardiac, vascular and/or pulmonary disease. Patients were studied during general anaesthesia (n = 6), regional anaesthesia (n = 10), or combined technique (n = 10) for abdominal or transurethral surgery. CNBP was obtained from a cuff placed around the upper arm and simultaneously compared to invasive pressure from the ipsilateral radial artery. A CNBP device (7001 Cortronic) used intermittent oscillometric measurement for calibration. Through a cuff continuously inflated to a pressure of 20 mmHg, a microprocessor-controlled electro-pneumatic acquisition system sensed displacements of the brachial artery wall. Amplified, digitally converted, filtered and transformed data were displayed as a continuous pulse pressure waveform and digital pressure values on the screen. The CNBP method functioned without disturbances before surgery in all patients. Intra-operative use of electrocautery or a spontaneous occurrence of warning on the screen repeatedly triggered oscillometric recalibration, hence CNBP measurements were discontinued in nine patients. Coefficients of correlation (r) of all invasive and CNBP pairs (n = 1111) were 0.68, 0.58 and 0.70 for systolic, diastolic, and mean blood pressures, respectively. Prediction errors (bias, mean +/- SD) were -13.6 +/- 22.5 mmHg (on average CNBP < invasive pressure) for systolic, +13.0 +/- 12.4 mmHg (CNBP > invasive pressure) for diastolic and +5.0 +/- 13.9 mmHg (CNBP > invasive pressure) for mean CNBP, as compared to radial artery pressure values. Absolute errors (precision) were 25.3 +/- 9.4 mmHg for systolic, 17.4 +/- 4.5 mmHg for diastolic, and 13.9 +/- 4.6 mmHg for mean CNBP. During anaesthesia induction (n = 672) the difference between consecutive measurements (trend of pressure changes) with invasive and CNBP method exceeded 20 mmHg in 90 (13.3%) instances for systolic, in 33 (4.9%) instances for diastolic, and in 45 (6.6%) instances for mean blood pressure. In conclusion, the CNBP method by brachial artery wall displacement failed to measure the blood pressure reliably and to display the trend of pressure changes correctly during anaesthesia induction. In its present form this CNBP method should not replace invasive blood pressure monitoring in high-risk patients neither for anaesthesia induction nor during non-thoracic surgical procedures.

Abdomen↗
PubMed1994

[Risk assessment and patient information before anesthesia].

In order to determine the risk of anesthesia the anesthesiologist has to assess both the physical and the psychological status of the patient. The essential basis of any preoperative medical evaluation are the history and complete physical examination of the patient. Few laboratory screening tests and, in case of pathological findings, specific diagnostic procedures will ensue. If possible, preoperative therapies must be considered in order to reduce the risk resulting from concomitant diseases. However, apart from the patients diseases, both the risks of the anesthetic and surgical procedures contribute to the overall perioperative risk. On the basis of the preoperative evaluation, the anesthesiologist determines the methods of anesthesia to be applied. He also informs the patient about the planned anesthesia, the sequence of further measures, the risk of anesthesia, and accompanying risks. The family doctor can help to facilitate the preoperative assessment by performing certain examinations himself and by providing the anesthesiologist with relevant informations. By giving a piece of advice to the patient he can help to prepare him for anesthesia and to reduce fear and apprehensiveness.

Anesthesia, General↗
PubMed1994

Assisted circulation without systemic heparinization.

The need for improvements in materials and equipment for extracorporeal circulation has been obvious for years. Among the surfaces with biologically active compounds, those with heparin binding have been found sufficiently thromboresistant and particularly suitable for different types of artificial perfusion. Partial left heart bypass (LHBP) was performed in 10 anesthetized, acutely instrumented, and open-chested mongrel dogs (weight 23 to 50 kg) with a servo-controlled roller pump. The pump flow was maintained at 50 mL/kg/min for 6 hours. Heparin surface-coated equipment was used without additional heparin. For LHBP with a standard circuit, the total amount of heparin during the study period was (mean +/- SD) 487 +/- 124 IU/kg. The right atrial, pulmonary artery, and left ventricular end-diastolic pressures, cardiac output, left ventricular output, right and left ventricular stroke work, pulmonary gas exchange, and acid-base balance changed similarly with both systems. Blood loss (204 +/- 78 v 1,240 +/- 586 mL, P < 0.0005), volume substitution requirements (647 +/- 48 v 1,860 +/- 764 mL, P < 0.0025), and oxygen extraction ratio (mean 25.4 to 32.0 v 25.4 to 56.4%, P < 0.025) were significantly lower, and mean aortic pressure (mean 65 to 69 v 62 to 38 mmHg, P < 0.025) and hemoglobin concentration (mean 9.1 to 8.1 v 9.4 to 3.9 g/dL, P < 0.05) were significantly higher during 6 hours of LHBP without systemic heparinization. Low but stable oxygen delivery was provided with heparin-coated LHBP, whereas it showed a descending trend (mean 14.0 to 10.8 v 13.4 to 5.5 mL/kg/min, P < 0.1) with the standard circuit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Cardiovascular and coronary physiology of acute isovolemic hemodilution: a review of nonoxygen-carrying and oxygen-carrying solutions.

Acute isovolemic hemodilution is used increasingly to avoid the potentially serious side effects of homologous blood transfusions. Cardiovascular physiology during hemodilution is characterized by a marked increase in cardiac output and organ blood flow to compensate for the decrease in arterial oxygen-carrying capacity. During advanced hemodilution an increased oxygen extraction is also observed, such that oxygen consumption generally is maintained even during advanced hemodilution. The increase in cardiac output is related mainly to a decrease in blood viscosity and an enhanced sympathetic tone resulting in stimulation of the heart. The magnitude and the mechanisms involved in the increase depend upon species, state of awareness (awake versus anesthetized), type of anesthesia, type of exchange solution, and condition of the heart prior to hemodilution. Recent laboratory findings, as well as clinical practice in cardiac surgery, suggest that moderate hemodilution to hematocrit values of approximately 25% is well tolerated in single vessel coronary artery disease which should thus not be regarded as an absolute contraindication for moderate hemodilution. An integral concept to minimize homologous blood transfusions consists of preoperative autologous blood donation, preoperative isovolemic hemodilution, meticulous (asanguineous) surgical technique, and acceptance of minimum hemoglobin levels during the entire hospitalization. The incidence of homologous blood transfusions will be reduced using acute isovolemic hemodilution. This incidence will be further reduced once hemoglobin solutions become clinically available for specific indications. At present, research activities are concentrated on defining the critical level of hemodilution in various pathologic conditions and to investigate pharmacology and physiology of the new hemoglobin solutions. Finally, several chemically modified hemoglobin-based oxygen-carrying solutions devoid of renal toxicity will be available in the future. The cardiovascular physiology and pharmacology of these hemoglobin solutions have been studied. Cardiac output is generally constant and oxygen extraction is increased to maintain oxygen consumption during hemodilution with hemoglobin solutions. In most studies, some vasoconstriction was observed also, which might result from interaction of the hemoglobin molecule with the EDRF/NO system. However, with enhanced purification, chemical modification or microencapsulation of the hemoglobin molecule, vasoconstriction can be limited.

Blood Substitutes↗