Time course of haemodynamic changes after maximal exercise

Abstract. The haemodynamic changes during 4 h following maximal upright bicycle exercise were evaluated in six normals in a randomized controlled crossover design. Total peripheral resistance was reduced to 2 h (-6·7 mmHgmin l^-1, P < 0·05); exercising and non-exercising vascular beds were vasodilated for 2h (-24·1 and -23·8 mmHg min ml^-1 100ml^-1 tissue, respectively, P < 0·05), associated with reductions in systolic (-5·8 mmHg, P < 0·05) and diastolic pressure (-8·3mmHg, P < 0·05). Rise in cardiac index for 1 h (+0·51min^-1 m^-2, P < 0·05) was accounted for by an elevated heart rate (+14·4 beats min^-1, P < 0·01) as stroke volume was unchanged. Body temperature was elevated until 40min (+0·20°C, P < 0·05). The return of all haemodynamic variables to control by 3h suggests a 3 h limit for a hypotensive effect of exercise. Rise in body temperature is not the only factor responsible for the hypotension.     

Detection of Dicrotic Notch in Arterial Pressure Signals

Objective. A novel algorithm to detect the dicrotic notch in arterial pressure signals is proposed. Its performance is evaluated using both aortic and radial artery pressure signals, and its robustness to variations in design parameters is investigated. Methods. Most previously published dicrotic notch detection algorithms scan the arterial pressure waveform for the characteristic pressure change that is associated with the dicrotic notch. Aortic valves, however, are closed by the backwards motion of aortic blood volume. We developed an algorithm that uses arterial flow to detect the dicrotic notch in arterial pressure waveforms. Arterial flow is calculated from arterial pressure using simulation results with a three-element windkessel model. Aortic valve closure is detected after the systolic upstroke and at the minimum of the first negative dip in the calculated flow signal. Results. In 7 dogs ejection times were derived from a calculated aortic flow signal and from simultaneously measured aortic flow probe data. A total of 86 beats was analyzed; the difference in ejection times was –0.6 ± 5.4 ms (mean ± SD). The algorithm was further evaluated using 6 second epochs of radial artery pressure data measured in 50 patients. Model simulations were carried out using both a linear windkessel model and a pressure and age dependent nonlinear windkessel model. Visual inspection by an experienced clinician confirmed that the algorithm correctly identified the dicrotic notch in 98% (49 of 50) of the patients using the linear model, and 96% (48 of 50) of the patients using the nonlinear model. The position of the dicrotic notch appeared to be less sensitive to variations in algorithm's design parameters when a nonlinear windkessel model was used. Conclusions. The detection of the dicrotic notch in arterial pressure signals is facilitated by first calculating the arterial flow waveform from arterial pressure and a model of arterial afterload. The method is robust and reduces the problem of detecting a dubious point in a decreasing pressure signal to the detection of a well-defined minimum in a derived signal.     

高血压病人左房收缩时间间期测定

为研究高血压病人之左室舒张功能，我们采用脉冲多普勒超声心动图技术测量分析了６６例高血压病人及４３例正常人的左房收缩时间间期。高血压组按有无第四心音分为两组。１８例高血压病人应用卡托普利治疗１周后分析左房收缩时间间期指标。高血压病人的心房射血前期及校正心房射血前期缩短，心房射血时间延长。高血压伴第四心音组与无第四心音组比较心房射血前期及校正心房射血前期缩短，心房射血时间延长。１８例高血压病人应用卡托普利治疗１周后左房收缩时间间期指标有明显改善。     

流式细胞术检测100例健康人外周血来源树突状细胞亚群

目的初步了解健康人外周血来源的树突状细胞亚群占白细胞总数的比例。方法采用免疫荧光三色标记流式细胞术检测100例健康人外周血树突状细胞亚群(DC1/D11C+和DC2/CD123+)。结果 DC1/CD11C+[男:(0.303±0.070)%,女:(0.255±0.079)%]和DC2/CD123+[男:(0.138±0.056)%,女:(0.109±0.039)%]亚群及DC1/DC2[男:(2.701±0.861)%,女:(2.508±0.989)%]在男与女之间差异均无统计学意义(P0.05)。结论流式细胞术检测外周血树突状细胞亚群快速准确,可能为健康人外周血树突状细胞占白细胞总数的比例提供大致参考。     

Automatic Adjustment of Pacing Parameters Based on Intracardiac Impedance Measurements

SCHALDACH, M.: Automatic Adjustment of Pacing Parameters Based on Intracardiac Impedance Measurements. The selection of the parameters used for rate control is determined not only by technical feasibility, but also by patient considerations. Technical feasibility considerations include long-term stability and reliability of the sensor, as well as susceptibility to interference. The patient considerations relate to the patient's physical state, including the various physiological and pathologic conditions. The rate response must be in proportion to circulatory demand. The specificity of the rate response is of particular importance for the patient with low cardiac reserve. The development of future pacemakers aims at providing additional patient benefits, with a reduction of the effort associated with initial parameter selection and patient follow-up. This will be achieved by utilizing a better understanding of the integration of the control mechanisms for the entire cardiovascular system under physiological and pathological conditions. To support the development of the future pacemakers, we must utilize realistic multiparametric models of the cardiovascular system. These models will assist the evaluation of potential algorithms for integrating multisensor signals into a single pacing rate. The parameterization and validation of these models are important issues to be addressed. Intracardiac impedance measurements in conjunction with microprocessor controlled signal processing and improved lead technology provide a great variety of practical applications for physiological control of the pacing rate and the automatic adjustment of pacemaker parameters. The concepts of an "intelligent" pacemaker capable of automatic control in response to changes in the pacing requirements under a variety of physiological and clinical conditions are presented.     

Exercise capacity and cardiovascular changes in patients with beta-thalassaemia major

Despite the introduction of deferoxamine, 50% of thalassaemia major patients die before the age of 35 years predominantly from iron induced heart failure. Indeed, the assessment of myocardial performance may be of particular interest since it can reveal an early myocardial dysfunction. By using impedance cardiography and mass spectrometry, we studied the cardiac function and the oxygen extraction ratio (O(2)ER) of 14 thalassaemic patients and 15 control healthy subjects during an incremental cycle-ergometer test. The achieved mechanical power output and the relative O(2) uptake did not reach any significant difference between groups. At the highest workload, O(2)ER reached significantly higher values in thalassaemic patients versus control subjects while the relationship between cardiac index (CI) and O(2)ER (CI/O(2)ER) decreased showing a lower contribution of cardiovascular system to maintain O(2) uptake. Results of this study imply that CI/O(2)ER allows an early diagnosis of the iron induced myocardial dysfunction, whereas it is not clinically patent yet. To our knowledge, this is the first study revealing an O(2)ER pivotal role as compensatory mechanism to maintain a normal working capacity in subjects suffering from thalassaemia major.     

The effects of low dose insulin infusions on the renin angiotensin and sympathetic nervous systems in normal man

To examine the effects of physiological insulin concentrations on the renin-angiotensin and sympathetic nervous systems, healthy volunteers were studied by the euglycaemic glucose clamp technique with sequential 60 min 0.5 and 1.0 mU kg-1 min-1 insulin infusions and, subsequently, by a control infusion simulating clamp conditions. Plasma renin activity increased from 0.8 +/- 0.1 ng ml-1 h-1 basally to 1.0 +/- 0.2 ng ml-1 h-1 during the 0.5 mU infusion to 1.4 +/- 0.1 ng ml-1 h-1 during the 1 mU infusion but did not change during control infusion (0.9 +/- 0.3 ng ml-1h-1 to 0.9 +/- 0.2 ng ml-1h-1 to 1.0 +/- 0.1 ng ml-1h-1) (P less than 0.001 insulin vs. control by ANOVAR). Plasma angiotensin II increased during insulin (21.2 +/- 1.8 to 25.2 +/- 2.3 to 29.3 +/- 2.4 pg ml-1) but not during control infusion (24.0 +/- 2.8 to 23.6 +/- 2.6 to 23.5 +/- 2.5 pg ml-1) (P less than 0.001 insulin vs. control). Serum aldosterone did not change significantly during either infusion (insulin: 239 +/- 89 pmol l-1 to 237 +/- 50 pmol l-1 to 231 +/- 97 pmol l-1, control: 222 +/- 79 to 237 +/- 50 to 213 +/- 97 pmol l-1). Plasma noradrenaline increased to a greater extent during insulin (1.03 +/- 0.2 to 1.14 +/- 0.8 to 1.27 +/- 0.17 nmol l-1) than control infusion (0.86 +/- 0.09 to 0.97 +/- 0.09 to 0.99 +/- 0.09 nmol 1-1 (P less than 0.01 insulin vs. control). Changes in mean systolic blood pressure during insulin infusion were significantly different from control (+ 3 vs. -4 mmHg, P less than 0.001). In conclusion acute hyperinsulinaemia within the physiological range increases circulating hormones of the renin-angiotensin and sympathetic nervous systems and also increases systolic blood pressure.     

Differences in β-adrenergic receptor density and adenylate cyclase activity between normal and leukaemic leukocytes

Abstract. An identical class of high-affinity binding sites for the ¹²⁵I-labelled β-adrenergic antagonist hydroxybenzylpindolol, was identified on intact human normal and leukaemic peripheral blood leukocytes. On normal unfractionated lymphocytes, polymorphonuclear leukocytes, and monocytes, receptor density did not differ significantly (1200–1400 receptors per cell; P > 0.3), but it was higher on B- than on T-lymphocytes ( P < 005). In leukaemia, monocytic blast cells expressed highest receptor numbers, whereas very low receptor density was seen on the pathologic B-cells from chronic lymphocytic leukaemia. Among normal leukocytes, adenylate cyclase activation by hormones (isoproterenol, prostaglandin E₁, histamine) and sodium fluoride was strongest in plasma membranes from monocytes, but very weak in polymorphonuclear leukocytes either due to uncoupling of hormone receptors from adenylate cyclase or to low catalytic activity. In T-cells, enzyme activity was significantly lower than in B-cells. Loss of adenylate cyclase sensitivity to hormones and fluoride occurred in leukaemic cells from chronic and acute lymphocytic leukaemia.     

肺动脉血流时间间期法预测肺动脉压的价值——脉冲多普勒与心导管同步性对比研究

在62例接受右心导管检查的患者中测量了肺动脉收缩压、平均压及平均压的自然对数值(PASP、PAMP、LnPAMP),并应用多普勒超声技术同步测量了肺动脉血流的AT、AT/ET、PEP/ET和PEP/AT。结果显示,PEP/AT与肺动脉压三项指标的相关最佳(r分别为0.65、0.63和0.62);AT、AT/ET与肺动脉压的相关次之(r分别为-0.54、-0.55和-0.50以及-0.42、-0.45和-0.43);PEP/ET与肺动脉压的相关较差(r分别为0.39、0.38和0.42)。     

Comparative haemodynamic effects of dobutamine and isoproterenol in man

Dobutamine was infused at a rate of 8 mcg/kg/min in 17 patients with or without congestive heart failure. Cardiac output increased from an average 2.92 to 4.45 1/min/m2 (p<0.001) with no change in mean aortic pressure (93.4 to 97.8 mmHg) and only a slight increase in heart rate (78 to 87 beats/min). Left ventricular end-diastolic pressure decreased from an average 19 to 13.7 mmHg (p<0.01). Peak left ventricular dp/dt was doubled (1147 to 2370 mmHg/sec, p<0.001) and Vmax increased from 1.08 to 2.18 circ/sec (p<0.001). In 10 patients given equi-inotropic doses (100 per cent increase in peak dp/dt) Isoproterenol produced a greater increase in cardiac output (71 percent) than Dobutamine (51 percent). isoproterenol caused mean aortic pressure to fall significantly (8 percent) while no change was noted with Dobutamine. Accordingly, peripheral vascular resistances were reduced to a greater extent with Isoproterenol than with Dobutamine (p<0.05). Mean pulmonary arterial pressure decreased significantly (25±5.9 to 22±5.7 mmHg, p<0.05) with Isoproterenol infusion and remained unchanged with Dobutamine infusion. Dobutamine increased both stroke work (57 percent) and minute work (83 percent). With Isoproterenol however, only minute work was significantly increased (90 percent). Dobutamine therefore is a potent inotropic drug, with mild chronotropic and peripheral vascular effects and may be valuable in the management of severe heart failure not associated with hypotension.     

冠心病左室收缩功能不全患者等容舒张时间及肺静脉血流频谱变化的研究

目的：研究冠心病左室收缩功能不全患者左室等容舒张时间（IRT）和肺静脉血流频谱变化。方法：心尖双平面Simpson法测定左室射血分数（LVEF）；脉冲多普勒测右上肺静脉血流频谱（S、Si、D、Di、PA、PAi、S/D）及二尖瓣口前向血流频谱（E、Ei、A、Ai、E/A）；连续多普勒测定IRT；对各组数据进行统计学分析。结果：当左室收缩功能不全时IRT延长、肺静脉血流频谱S峰变慢、二尖瓣血流频谱假性正常化。相关分析结果表明左室收缩功能与舒张功能变化显著相关。结论：冠心病左室收缩功能不全患者存在左室舒张功能异常，IRT延长与肺静脉血流频谱S波减低比二尖瓣血流频谱更为敏感地反映了舒张功能异常。     

Changes in left ventricular ejection time and pulse transit time derived from finger photoplethysmogram and electrocardiogram during moderate haemorrhage

Objectives: Early identification of haemorrhage is difficult when a bleeding site is not apparent. This study explored the potential use of the finger photoplethysmographic (PPG) waveform derived left ventricular ejection time (LVET_p) and pulse transit time (PTT) for detecting blood loss, by using blood donation as a model of controlled mild to moderate haemorrhage. Methods: This was a prospective, observational study carried out in a convenience sample of blood donors. LVET_p, PTT and R‐R interval (RRi) were computed from simultaneous measurement of the electrocardiogram (ECG) and the finger infrared photoplethysmogram obtained from 43 healthy volunteers during blood donation. The blood donation process was divided into four stages: (i) Pre‐donation (PRE), (ii) first half of donation (FIRST), (iii) second half of donation (SECOND), (iv) post‐donation (POST). Results and conclusions: Shortening of LVET_p from 303+/?2 to 293+/?3 ms (mean+/?SEM; P<0·01) and prolongation of PTT from 177+/?3 to 186+/?4 ms (P<0·01) were observed in 81% and 91% of subjects respectively when comparing PRE and POST. During blood donation, progressive blood loss produced falling trends in LVET_p (P<0·01) and rising trends in PTT (P<0·01) in FIRST and SECOND, but a falling trend in RRi (P<0·01) was only observed in SECOND. Monitoring trends in timing variables derived from non‐invasive ECG and finger PPG signals may facilitate detection of blood loss in the early phase.     

Non-invasive measurements of cardiac output in atrial fibrillation: Inert gas rebreathing and impedance cardiography

Abstract

Background. Atrial fibrillation (AF) is associated with significant morbidity and mortality. To test the effect of interventions, knowledge of cardiac output (CO) is important. However, the irregular heart rate might cause some methods for determination of CO to have inherent weaknesses. Objective. To assess the validity of these methods in AF, a new inert gas rebreathing device and impedance cardiography was tested with echocardiography as reference. Methods. Using a cross-sectional design, 127 patients with AF and 24 in SR were consecutively recruited. Resting CO was measured using inert gas rebreathing (n = 62) or impedance measurement of intrathoracic blood flow (n = 89) in separate studies with echocardiographic measurement as reference. Results. CO determined with impedance cardiography was mean 4.77 L/min ± 2.24(SD) compared to 4.93 L/min ± 1.17 by echocardiography (n = 89, n.s.) in patients with AF. CO by inert gas rebreathing was 4.98 L/min ± 2.49(SD) compared to 5.70 L/min ± 2.49 by echocardiography (n = 62, n.s.) in patients with AF and SR (AF 5.42 ± 2.9 vs. 6.27, n.s. and SR 4.09 ± 1.08 vs. 4.35 ± 0.86, n.s.). Mean bias between impedance cardiography and echocardiography was 0.14 ± 0.95 L/min and ?0.13 ± 0.98 L/min between inert gas rebreathing and echocardiography. Inert gas rebreathing showed larger intra-patient variation than impedance cardiography (0.11 vs. 0.054). Correlation between inert gas rebreathing and echocardiography was r = ?0.060 and between impedance cardiography and echocardiography was r = 0.128. Impedance cardiography and inert gas rebreathing both underestimated CO compared to echocardiography. Conclusion. Variation between the inert gas rebreathing and the reference method for AF patients was less than desired. Impedance cardiography was superior to inert gas rebreathing and showed acceptable agreement with echocardiography and variability similar to echocardiography.     

Time course of early and late changes in plasma DNA in trauma patients

BACKGROUND: Cell-free DNA concentrations increase in the circulation of patients after trauma and may have prognostic potential, but little is know concerning the temporal changes or clearance of the DNA or its relationships with posttraumatic complications. We investigated temporal changes in plasma DNA concentrations in patients after trauma with use of real-time quantitative PCR. METHODS: Serial plasma samples were taken from two trauma populations. In the first study, samples were collected every 20 min from 25 patients within the first 3 h of trauma. In the second study, samples were collected every day from 36 other trauma patients admitted to the intensive care unit (ICU). RESULTS: In the first study, plasma DNA was increased within 20 min of injury and was significantly higher in patients with severe injury and in patients who went on to develop organ failure. In patients with less severe injuries, plasma DNA concentrations decreased toward reference values within 3 h. In the second study, plasma DNA concentrations were higher in patients who developed multiple organ dysfunction syndrome between the second and fourth days of admission than in patients who did not develop the syndrome. In patients who remained in the ICU with continuing organ dysfunction, plasma DNA remained higher than in healthy controls even at 28 days after injury. Most survivors with multiple organ dysfunction syndrome showed an initial very high peak followed by a prolonged smaller increase. CONCLUSIONS: Plasma DNA concentrations increase early after injury and are higher in patients with severe injuries and in those who develop organ failure. Increased plasma DNA persists for days after injuries, especially in patients with multiple organ dysfunction syndrome.     

Local and central sympathetic reflex control of blood flow in skeletal muscle and subcutaneous tissue in normal man

Summary. The effect of age and sex on relative changes in blood flow and vascular resistance in skeletal muscle and subcutaneous tissue during postural changes and during local increase in transmural pressure was studied in 33 healthy subjects. The intra-individual variation was studied in five subjects. Blood flow was measured by the local ¹³³Xenon wash-out method. No relation to age or sex was seen in the centrally elicited sympathetic vasoconstrictor responses in subcutaneous tissue and skeletal muscle and in the locally elicited vasoconstriction in subcutaneous tissue. A small, but statistically significant, correlation to sex and age was found in the local sympathetic vasoconstrictor response in skeletal muscle. The age correlation was caused only by an attenuated response in the young subjects below 40 years of age and may be fortuitous. The intra-individual variation was acceptably small. Based on the present results, a reduction in blood flow in skeletal muscle and subcutaneous tissue during centrally or locally elicited sympathetic vasoconstriction of 10% or less should be considered abnormal. The local ¹³³Xenon wash-out method is of value in examining patients suspected of dysfunction in the sympathetic part of the autonomic nervous system.     

Characterization and mechanisms of the cardiovascular and haemodynamic alterations induced by scorpion venom in rats

The scope of this work was to investigate the nature, chronology and mechanisms of the cardiovascular disorders induced by scorpion envenomation. Anaesthetized rats were instrumented for measurement of cardiac output (CO), renal (RBF) and muscular (HBF) blood flows (pulsed Doppler flowmetry), blood pressure, heart rate and dP/dt. Buthus occitanus venom (BO) was administered intravenously in the absence/presence of different pre-treatments. BO dose-dependently (150-300 microg/kg) increased blood pressure, dP/dt, total peripheral (TPR), renal (RVR) and muscular (HVR) vascular resistances, and decreased CO, RBF and HBF. Recovery occurred after 150 but not after 300 microg/kg. BO, 600 microg/kg, produced qualitatively similar effects but arrhythmias developed and mortality increased. Pre-treatment with phentolamine prevented the rises in TPR, RVR, HVR and blood pressure and the decreases in CO, RBF and HBF induced by BO, 300 microg/kg. Pre-treatment with propranolol prevented the rise in dP/dt and the occurrence of arrhythmias and limited the rise in RVR and the drop in RBF induced by BO, 300 microg/kg. Phentolamine, propranolol and their combination also prevented BO, 600 microg/kg-induced mortality. Other pre-treatments (bosentan, losartan, diltiazem, mepyramine) were almost ineffective vs. BO effects. Finally, BO, 300 microg/kg, induced a 30-40-fold increase in plasma epinephrine and norepinephrine levels, but no change in plasma endothelin-1 levels. Thus in anaesthetized rats, the pattern of the cardiac and systemic and regional haemodynamic effects of BO is typically that of and results from catecholamine outpouring-induced alpha- and beta-adrenoceptor stimulation.     

The Use of Impedance Cardiography in Predicting Mortality in Emergency Department Patients With Severe Sepsis and Septic Shock

Objectives: Pulmonary artery catheterization poses significant risks and requires specialized training. Technological advances allow for more readily available, noninvasive clinical measurements of hemodynamics. Few studies exist that assess the efficacy of noninvasive hemodynamic monitoring in sepsis patients. The authors hypothesized that cardiac index, as measured noninvasively by impedance cardiography (ICG) in emergency department (ED) patients undergoing early goal‐directed therapy (EGDT) for sepsis, would be associated with in‐hospital mortality. Methods: This was a prospective observational cohort study of patients age over 18 years meeting criteria for EGDT (lactate > 4 or systolic blood pressure < 90 after 2 L of normal saline). Initial measurements of cardiac index were obtained by ICG. Patients were followed throughout their hospital course until discharge or in‐hospital death. Cardiac index measures in survivors and nonsurvivors are presented as means and 95% confidence intervals (CI). Diagnostic performance of ICG in predicting mortality was tested by receiver operating characteristic (ROC) curve and areas under the ROC curves (AUC) were compared using Wilcoxon test. Results: Fifty‐six patients were enrolled; one was excluded due to an inability to complete data acquisition. The mean cardiac index in nonsurvivors (2.3 L/min·m², 95% CI = 1.6 to 3.0) was less than that for survivors (3.2, 95% CI = 2.9 to 3.5) with mean difference of 0.9 (95% CI = 0.12 to 1.71). The AUC for ICG in predicting mortality was 0.71 (95% CI = 0.58 to 0.88; p = 0.004). A cardiac index of < 2 L/min·m² had a sensitivity of 43% (95% CI = 18% to 71%), specificity of 93% (95% CI = 80% to 95%), positive likelihood ratio of 5.9, and negative likelihood ratio of 0.6 for predicting in‐hospital mortality. Conclusions: Early, noninvasive measurement of the cardiac index in critically ill severe sepsis and septic shock patients can be performed in the ED for those who meet criteria for EGDT. There appears to be an association between an initial lower cardiac index as measured noninvasively and in‐hospital mortality. ACADEMIC EMERGENCY MEDICINE 2010; 17:452–455 © 2010 by the Society for Academic Emergency Medicine     

Effect of indomethacin upon angiotensin-induced changes in blood pressure and plasma aldosterone in normal man

Abstract. The effect of indomethacin (75 mg/day for 3 days) on the response to i.v. angiotensin II was investigated in eight healthy, sodium-repleted, male subjects. Indomethacin reduced the release of aldosterone during the i.v. administration of angiotensin II (5, 10 and 20 ng kg^-1 min^-1), whereas the pressor response to angiotensin II and to succinamyl¹-val⁵-phenylglycine-acetate⁸-angiotensin II, an agonistic angiotensin II-analogue, was increased. Plasma renin concentration was reduced following treatment with indomethacin. These data confirm the modulatory influence of endogenous prostaglandins upon the vasoconstrictor effect of angiotensin II and could suggest a direct interference of prostaglandins with the secretion of aldosterone.