Investigation of the parallel conductor model of impedance cardiography by means of exchange transfusion with stroma free haemoglobin solution in the dog

To test one of the assumptions underlying the calculation of stroke volume--namely, that the transthoracic impedance consists of a parallel connection of a tissue impedance and a blood resistance--experiments were carried out on four dogs in which blood was gradually replaced by a stroma free haemoglobin solution, with the purpose of changing the blood resistance while leaving the tissue impedance unchanged. This was accomplished by exchange transfusion in such a way that the volume of the circulating fluid remained constant and the distribution of fluid volume between the fluid compartments was not altered. During the exchange transfusions the mean decrease in resistivity of the circulating fluid was 54%. The packed cell volume and resistivity of every volume of removed circulating fluid were measured. Just before each exchange the real and imaginary parts of the transthoracic impedance were measured. The packed cell volume decreased exponentially with the number of exchanges. This indicates that the circulating fluid volume remained constant during the exchange transfusion. From the packed cell volumes an estimate of the circulating fluid volume was made. Because of the parallel connection all calculations were based on the use of admittance, which is the reciprocal value of impedance. The real and imaginary parts of the transthoracic admittance were calculated from the measured values of the real and imaginary parts of the transthoracic impedance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in the impedance cardiogram occurring with change in posture in patients with heart disease

The response of the heart to changes in posture from supine through sitting to standing was recorded by impedance cardiography. The study comprised 22 normal subjects and 74 patients with a variety of heart diseases. The results demonstrate that in normal subjects acceleration of blood in systole decreased on sitting and standing. In subjects with impaired cardiac function this acceleration increased on sitting and standing from the supine position. This clear-cut difference in response provides a subtle method of detecting impaired function and in addition, provides a method of monitoring the effects of vasodilator or other treatment.     

Accuracy of the impedance cardiogram in the measurement of cardiac output in the elderly

The cardiac output has been determined by radionuclide angiocardiography and by impedance cardiography in 93 elderly patients. The agreement between the two methods was excellent in patients in sinus rhythm, without regurgitant valvular lesions, and without severe airways obstruction or right bundle branch block. In atrial fibrillation the lack of correlation may be due to differences in heart rate during the two measurements, in regurgitant valvular lesions to the fact that impedance cardiography measures stroke output, whether forward or backward, in airways obstruction to high values for the basal thoracic impedance, and in right bundle branch block perhaps to the abnormal impedance wave-form often present.     

换血治疗新生儿高胆红素血症的预后分析

目的 评价换血疗法对新生儿高胆红素血症的预后,以积累临床经验,指导临床工作.方法 跟踪观察43例应用外周动静脉同步换血治疗的高胆红素血症的新生儿作为观察组,观察治疗后10～12个月时听力、发育及神经运动功能的状况.选取同期未应用换血治疗的高胆红素血症新生儿43例作为对照组.结果 观察组患儿在听力、发育及神经运动功能方面明显优于对照组.结论 换血治疗新生儿高胆红素血症,在改善患儿听力、发育及神经运动功能方面有重要价值,可以临床中推荐应用.     

Megakaryocytopoiesis in the rat: response to thrombocytopenia induced by exchange transfusion

We have studied the megakaryocytopoietic response in rats to acute thrombocytopenia induced by exchange transfusion of platelet-poor blood. Our analysis included serial determinations of peripheral blood counts, the size and number of megakaryocytes in sections of humeral marrow, the numbers of megakaryocytic (CFU-Meg) and granulocyte-macrophage (CFU-GM) colony-forming cells in marrow and spleen, and the proportion of CFU-Meg and CFU-GM in DNA synthesis. With exchange transfusion, the platelet count fell to 11% of the control value (101,000 +/- 49,000/mm3; mean +/- SD) and returned to normal by day 3; rebound thrombocytosis (peak 1,720,000 +/- 246,000/mm3) was observed on days 4 and 5. The average size of marrow megakaryocytes increased significantly on days 2 and 3 compared with normal (p less than 0.01), but the numbers of recognizable megakaryocytes did not change through day 5. The numbers of splenic CFU-Meg and CFU-GM increased significantly (p less than 0.05) on days 2-4 and on day 2, respectively, after the exchange; however, the numbers of marrow progenitors, which account for over 95% of total body progenitors, remained unchanged throughout the duration of the study. The proportion of CFU-Meg in DNA synthesis (mean +/- SD) increased from a baseline value of 17% +/- 4% to 33% +/- 11% (p less than 0.02) and 35% +/- 6% (p less than 0.001) on days 1 and 2, respectively, and returned to control values thereafter. There were no changes in the cell cycle activity of CFU-GM. Thus, acute selective thrombocytopenia induced by exchange transfusion causes an enlargement of marrow megakaryocytes and an increase in the fraction of CFU-Meg in cell cycle. These changes, occurring in the absence of immunologically mediated events, are the direct result of lowered platelet count.     

A study on the value of red cell exchange transfusion in transfusion dependent anaemias

We compared red cell exchange transfusions (RC Ex) on the Aminco Celltrifuge (continuous flow cell separator) with conventional transfusions in 17 patients aged between 7 and 24 years who have transfusion dependent homozygous beta-thalassaemia and two other patients with chronic transfusion dependent anaemias aged 20 and 22. We aimed to return the youngest cohort of cells ('Neocytes') from both donor blood and the patient and to discard older cells ('gerocytes'). Using RC Ex, red cell transfusion requirement was reduced by 30%, reducing significantly the iron load, and the transfusion interval was increased by 43%. There is a great demand by the patients to continue this therapy as they have appreciated the immediate benefit of reduced hospitalization.     

Pulmonary gas exchange after multiple airway occlusion by beads in the dog

Patients with asthma frequently show a bimodal distribution of ventilation-perfusion (VA/Q) ratios. One mode is centered on a VA/Q ratio of near normal value, whereas the other has a very low VA/Q ratio. There is usually almost no perfusion of unventilated units. We have suggested that this bimodal pattern is caused by complete obstruction of some airways with ventilation of their distal alveoli through collateral channels. To test this hypothesis we occluded airways of anesthetized dogs with beads of 1.6, 2.4, and 4.8 mm in diameter, and measured VA/Q distributions using the multiple inert gas elimination technique. Beads were inserted via a bronchoscope until the Pao2 fell by 20 mm Hg, or its value was less than 70 mm Hg. Occlusion of small airways (1.6 mm diameter) resulted in a mild increase in dispersion of VA/Q ratios. With 2.4 mm beads, the dispersion increased further. By contrast, all dogs given 4.8 mm beads showed a bimodal distribution of VA/Q ratios. All animals developed some shunt. We interpret these results as showing that when 1.6 mm airways are occluded, collateral ventilation to distal units is so efficient that ventilation is only mildly impaired; however, as occlusion becomes more proximal, collateral ventilation is less effective until with 4.8 mm beads, the ventilation of distal units is so poor that a bimodal pattern develops. The results suggest that the bimodal distributions seen in asthma are compatible with complete obstruction of some airways, and that the levels of obstruction may affect the pattern of VA/Q distribution.     

A pilot study of the possibility and the feasibility of haemoglobin dosing with red blood cells transfusion

Background and Objectives Red blood cell concentrates (RBCs) are the major blood component transfused. Although the haemoglobin content is variable, the transfusion dose is prescribed as units of red cell concentrates. Thus, by chance, large volume patients may receive a low haemoglobin dose and low volume patients may be transfused with haemoglobin‐rich RBCs. The aim of this study was to evaluate whether the haemoglobin increment (grams per litre) in the patient can be predicted from the haemoglobin dose (in grams) transfused, with and without correction for estimated blood volume. If this is true, it may be possible to achieve the predicted transfusion outcome by selecting RBCs for each patient. Materials and Methods Haemodynamically stable patients scheduled for day treatment with transfusion of RBCs were recorded. A total of 52 transfusions episodes, 27 for women and 25 for men, were recorded. Blood volumes were estimated, haemoglobin content in the RBCs was measured before transfusion, and pre‐ and post‐transfusion haemoglobin concentrations were obtained. Results The haemoglobin content of the RBCs prepared for transfusion showed a wide range, varying from 38·7 g/unit to 69·0 g/unit. There were statistically significant correlations between haemoglobin concentration in the RBCs and haemoglobin increment in patients. Conclusion Post‐transfusion increment in circulating haemoglobin can be predicted from the haemoglobin content of transfused cells, but knowledge of the patient’s blood volume improves the accuracy of prediction. It may be feasible to select the high haemoglobin content RBC for patients with largest blood volume and vice versa.     

Glycosylated haemoglobin in clarification of the origin of hyperglycaemia in acute cerebrovascular accident

In 148 patients admitted to hospital with acute cerebrovascular accidents (CVA), the levels of glycosylated haemoglobin (HbA1c) and blood glucose were measured to evaluate the effect of the duration and severity of hyperglycaemia on stroke outcome. Eighty-eight (59%) patients had clearly normal blood glucose and HbA1c concentrations (blood glucose less than 5.5 mmol l-1, HbA1c less than 8.6%). The remaining 60 patients were defined as hyperglycaemic. Nineteen (13%) had known diabetes, whereas in 23 (16%) hyperglycaemia was probably due to unrecognized diabetes. In 18 (12%) patients transient hyperglycaemia was observed. Recovery after CVA was best among normoglycaemic patients (good 45%, moderate 29%, poor 14%, fatal 12%) and poorest among diabetic patients (moderate 21%, poor 37%, fatal 42%). Fatal outcome in patients from the normoglycaemic group differed significantly from patients belonging to known diabetic and unrecognized diabetic groups (p less than 0.05), but was not different from that in patients with transient hyperglycaemia, who did however differ from both diagnosed and unrecognized diabetic patients (p less than 0.05). No significant differences were found between CVA outcome in the known diabetic and unrecognized diabetic groups.     

昆明地区健康成人脉冲振荡肺功能测定

目的确定昆明地区健康成人脉冲振荡肺功能的正常参考值及预计值。方法185例昆明地区的的健康成人,常规肺功能正常,测定脉冲振荡肺功能,指标包括R(5~35)Hz粘性阻力,X(5~35)Hz弹性阻力及惯性阻力,Fres(共振频率),Zrs(呼吸总阻抗),Rc(中心阻力),Rp(周边阻力),顺应性Cl、Cb及Cm等。结果X5~X35、Cl、Cb、Cm、Rp不呈正态分布。建立了阻抗R的多元回归方程式。结论建议临床使用本地区正常预计值,实测值/预计值%保持不变。     

Localization of the origin of ventricular arrhythmia by means of Frank's vectorcardiogram

Frank's lead system vectorcardiogram (VCG) was used to record the ventricular arrhythmias (VA) of different areas induced by pacing in 22 canines and by stimulating the epicardium of different areas in 8 patients of mitral stenosis during operation. The results showed that VCG can localize the origin of VA of 13 areas in canines and 9 areas in human. To localize the VA at or near ventricular septum VCG is more accurate than ECG (94% vs 70%).