Effects of tracheal extubation on coronary blood flow,myocardial metabolism and systemic haemodynamic responses

Global coronary blood flow and metabolism were measured in seven patients on the first postoperative day following coronary revascularization to test the hypothesis that tracheal extubation produces adverse haemodynamic responses akin to those observed during tracheal intubation. Regional coronary flow and metabolic measurements were made in five of the seven patients. Extubation from a continuous positive airway pressure (CPAP) of 5 cm H₂O was associated with a statistically significant rise in cardiac index from 3.44 ± 0.23 L · min^-1 · m^-2 to 3.73 ± 0.15L·min^-1 ·m^-2 related to an increase in stroke index, without significant changes in heart rate, mean arterial and pulmonary capillary wedge pressure. Consequently the changes in myocardial oxygen consumption (8.52 ± 0.55 to 8.85 ± 0.93 ml · min^-1) and coronary blood flow (172 ± 18 to 179 ± 17 ml·min^-1) were less prominent than those reported during intubation, where substantial rises in myocardial oxygen consumption and coronary flow occurred. Two patients experienced cardiac lactate production but there were no changes in systemic or coronary haemodynamics, nor were there clinical or electrocardiographic signs of ischaemia. We conclude that extubation does not appear to be associated with adverse systemic or coronary haemodynamic responses in patients following coronary bypass grafting. However, the revascularized myocardium may remain vulnerable to anaerobic metabolism in the immediate postoperative period. Pour savoir si comme ľintubation, ľextubation de la trachée provoque des perturbations hémodynamiques, on a mesuré le métabolisme et la circulation coronarienne globale chez sept patients, au lendemain ďun pontage aorto-coronarien. On a aussi calculé les valeurs régionales de ces mêmes variables pour cinq ďentre eux. Ľindex cardiaque de 3.44 ± 0.23 L · min^-1 · m^-2 sous pression positive en respiration spontanée (CPAP) de 5 cm. H₂O s’est élevé à 3.73 ± 0.15 L · min^-1 · m^-2 post-extubation avec une augmentation significative du volume ďéjection. La fréquence cardiaque et les pressions artérielles moyennes et capillaires pulmonaires n’ont pas changé. Ainsi ľaugmentation de la consommation ďoxygène du myocarde de 8.52 ± 0.55 à 8.85 ± 0.93 ml · min^-1 et celle du flot coronarien de 172 ± 18 à 179 ± 17 ml · min^-1 ont été moindres que celles, importantes, déjà observées lors de ľintubation. On a noté chez deux patients une production de lactate par le myocarde, sans changement de ľhémodynamic systémique et coronarienne non plus que de signe clinique ou électrocardiographique ďischémie. Donc, après un pontage coronarien, ľextubation ne semble pas causer ďeffet néfaste sur les circulations systémique et coronarienne, toutefois, le myocarde revascularisé peut demeurer sensible au métabolisme anaérobique.     

随机系统的最小熵控制

本文放弃传统的MSE准则,从信息论观点出发,发展了随机系统的一种最小熵(ME)控制方法,并从ME控制的等价性、控制限度、存在性、唯一性及必要条件等方面,研究了ME控制的合理性和实用性。ME方法是一种全局分析法,它不仅包含了MSE和MAP准则,且由于全文在整个推导中并未假定高斯性、线性和非时变等,因而原则上适用于诸如非高斯、非线性、时变等传统方法难以处理的复杂系统;不仅适用于工程系统,将其推广到决策、社会、经济等领域会更为自然和切合实际。     

As_2O_3诱导人肝癌细胞凋亡及对Fas表达和钙含量的影响

化疗在原发性肝癌的综合治疗中占重要地位.为寻找肝癌治疗新的有效药物,我们观察了As2O3对人肝癌细胞株BEL7402的生物学效应,以期为As2O3临床治疗肝癌提供实验依据.     

Implication of the systolic hump in systemic arterial pressure waves

The systolic hump in the aortic blood pressure wave is defined as the aorticresistance component proportional to the aortic blood flow superimposed on the windkessel component. An electrical analogue comprising a series resistance (aortic resistance) plus a resistance (peripheral resistance) and capacitance (aortic compliance) in parallel (i.e. windkessel component) is used for analysis. Curve fitting using the leastsquares method is performed on calculated and measured blood pressure waves from dogs under haemodynamical conditions induced by infusion of three drugs (noradrenaline, isoproterenol and acetylcholine). The curve fitting RMS (root mean square) errors are <3% for blood pressure waves and <30% for blood flow waves, with good agreement between measured and calculated blood flow waveforms. Infusion of noradrenaline and acetylcholine is found to induce a significant decrease and increase in the aortic resistance, respectively. Although only a small fraction of the blood pressure wave, the systolic hump has a marked effect on the systolic pressure waveform.     

Surface activation markers of T lymphocytes: role in the detection of infection in neonates

Diagnosis of perinatal infection in the newborn is difficult; there may be few clinical signs and current tests are slow or non-specific. Detection of organisms, antigen or specific antibody to common pathogens often requires repeat samples and does not give immediate results. Haematological parameters, although relied upon frequently to diagnose infection in the neonate prior to a positive bacterial isolation, are unreliable and insensitive. Indicators such as an increase in neutrophil band cell counts are highly variable between morphologists. Infection induces the expression of a number of T lymphocyte surface markers, including CD45RA/CD45RO and CD45RO. The use of changed expression of surface markers as a laboratory test for detection of infection in neonates was evaluated. We used multiparameter flow cytometry to detect expression of early (CD45RA/CD45RO) and late (CD45RO) activation markers. In the respective groups of 50 full term (including 25 normal vaginal deliveries and 25 caesarean deliveries) and 30 premature, i.e. < 36 weeks gestation (born by either normal vaginal delivery or caesarean delivery) the CD45RA isoform was brightly expressed on newborn ‘naive’ CD4⁺ T cells, whereas the CD45RO isoform (including both ‘bright’ and ‘dim’ populations) was present on < 19% of CD4⁺ T cells from these newborn infants. In a group of 37 infants, tested to evaluate possible effects of non-infective parameters such as respiratory distress and iso-immunization, no significant changes in surface marker expression were found and specificity of the test was confirmed. In 14 neonates with documented sepsis, up-regulation of dual staining CD45RA/CD45RO isoforms on CD4⁺ T cells was detected early in the infection. In addition, we found that CD45RO expression persisted for several weeks after bacterial infection, and up to several months in viral infection. In conclusion, detection of T cell activation by flow cytometry for the early diagnosis of neonatal infection is an easy test to carry out on small volumes of blood, is inexpensive, and may be a specific indicator of infection.     

Estimation of average flow in ungated 3D phase contrast angiograms

Three dimensional (3D) phase contrast angiograms contain velocity data, which is discarded after the reconstruction of the projections. In extension to earlier work on velocity quantification with ungated 2D phase data, this paper shows that a useful estimate of the average velocity and flow rate can be extracted from ungated 3D phase contrast angiograms. Simulations and experiments in a phantom and in vivo were performed. For pulsatile flow and strong spin saturation, an over-estimation of the flow rate at the net in-flow end of the imaging volume and underestimation at the net out-flow end was observed. Imaging at lower RF tip angles yielded flow rates close to the correct value within the entire imaging volume. In contrast to ungated 2D experiments, the flow rates determined by repeated 3D experiments showed no variation.     

Differential effects of sulindac on renal hemodynamics and function in the rat

Renal hemodynamics were studied using an electromagnetic perivascular flow sensor in anesthetized rats injected i.v. with vehicle, 5 or 10 mg/kg body weight (b.w.) sulindac. No hemodynamic changes occurred with vehicle (n=6), but mean arterial pressure was significantly decreased (by 15 mmHg) with sulindac (n=12). In the 5 mg/kg b.w. sulindac group (n=7), renal blood flow progressively and significantly increased from 7.88±0.36 to 8.98±0.58 ml/min, except during concomitant intrarenal infusion of 3 mg/kg b.w. per h proadifen (n=7). The pressure limits for efficient and no renal blood flow autoregulation remained unchanged (approx. 100 and 80 mmHg, respectively). In the 10 mg/kg b.w. sulindac group (n=5), renal blood flow did not change but autoregulatory pressure limits were lowered by 10 mmHg 2 h after treatment (P<0.025). Also, Na⁺ retention was marked. Prostanoid excretion in urine was significantly reduced with either dose but basal plasma renin activity was not (about 8 ng/ml per h; n=15). When plasma renin activity was enhanced after a reduction in renal perfusion pressure (n=21), it was decreased from 11.5±1.2 to 7.4±0.2 ng/ml per h only by 10 mg/kg b.w. sulindac (P<0.05; n=6). In conclusion, differential effects of sulindac on renal hemodynamics, Na⁺ excretion and plasma renin activity were demonstrated. Renal hemodynamic changes could be related in part to the cytochrome P-450 arachidonic acid pathway.     

Factors related to renal haemodynamics in young type-1 diabetes mellitus patients

The influence of metabolic control (HbA_1c), noradrenaline (NA) and insulin-like growth factors (IGF-I and IGF-II) on renal function and size was investigated in 11 insulin-dependent diabetes mellitus patients aged 11–17 years. Renal function was evaluated in terms of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). Renal size was determined as renal parenchymal volume (RPV) by ultrasonography. The patients' HbA_1c values ranged from 8.2% to 12.9% (normal range 5.5–8.5%) and their GFR and ERPF were higher than normal. Their IGF-II values were higher, and NA and IGF-I levels were lower than those of healthy controls. Inverse correlations between NA and GFR (r=–0.66) and NA and ERPF (r=–0.63) were found. No correlation was found between serum IGF-I and renal functional parameters. The IGF-II values correlated with GFR and HbA_1c (r=0.63,r=0.70 respectively). There were linear correlations between RPV and GFR, RPV and ERPF, HbA_1c and GFR, and ERPF and RPV. Decreased NA concentrations and increased IGF-II values appear to be factors contributing to renal hyperfunction in these patients.     

Detection of cytoplasmic IL-1 beta in peripheral blood mononuclear cells from intensive care unit (ICU) patients.

Cytokines including IL-1 beta have been implicated in the pathophysiology of sepsis and the systemic inflammatory response. It is believed that certain critically ill patients may be 'primed' with respect to cytokine production, and that subsequent 'triggers' may cause exaggerated cytokine production in these patients with exacerbation of their clinical condition; however, no means of identifying 'primed' patients has been described. The presence of cytoplasmic IL-1 beta within peripheral blood mononuclear cells (PBMC) from patients in the ICU was investigated as a means of identifying 'primed' patients, using fluorescent antibody labelling and flow cytometry. The study revealed that PBMC from ICU patients had a different staining pattern for IL-1 beta than those from healthy subjects, and that PBMC from certain ICU patients did indeed stain strongly for IL-1 beta; however, the presence of these strongly staining cells was not associated with clinical condition or outcome. It is concluded that whilst it might be possible to identify 'primed' patients in the ICU using this technique, this is of no clinical value as a predictor of clinical course.     

Blood flow acceleration in the carotid and brachial arteries of healthy volunteers: respective contributions of cardiac performance and local resistance

Summary— The influence of local resistance and cardiac performance on peripheral blood acceleration was investigated in 14 healthy male volunteers. Steady and pulsatile flow was studied in the brachial and in the common carotid arteries, ie, two territories that exhibit marked differences in resistive characteristics. Instantaneous blood velocity (V), mean blood velocity (V_m) and artery diameter (D) were evaluated at rest by an ultrasonic range-gated pulsed Doppler flowmeter using a double transducer probe, thus allowing the calculation of mean blood flow (Q). Mean local resistance (R) was obtained by dividing the mean arterial pressure by Q. The peak value of the local acceleration of the blood was obtained by computer-assisted calculation of the first derivative of instantaneous blood velocity (G_max = +dV/dt_max). Peak aortic blood acceleration (GAo) was simultaneously measured from the suprasternal notch using a pulsed Doppler velocity meter. In the brachial and the common carotid arteries, G_max was of a similar magnitude (551 ±30 and 555 ± 44 cm/s², respectively) despite major differences in the respective D, V_m, Q and R values. In neither artery was there a relationship between G_max and either resting Q or R. At the brachial artery level, G_max was positively related to GAo ( r = 0.79, P = 0.0008). At the common carotid artery level, there was a weak, although non significant relationship between G_max and GAo ( P = 0.08). Our results indicate that the local acceleration of peripheral blood flow in the brachial artery is related rather to upstream central impulse than to downstream hemodynamics, and suggest some regional differences in the hemodynamic determinants of the local acceleration of peripheral blood flow.