Background: In this study, we aim to investigate the simulation of the cardiovascular system using an electronic circuit model under normal and pathological conditions, especially the Eisenmenger syndrome. Methods and Results: The Eisenmenger syndrome includes a congenital communication between the systemic and pulmonary circulation, with resultant pulmonary arterial hypertension and right-to-left reversal of flow through the defect. When pulmonary vascular resistance exceeds systemic vascular resistance, it results in hypoxaemia and cyanosis. The Westkessel model including Resistor-Inductance-Capacitance pi-segments was chosen in order to simulate both systemic and pulmonary circulation. The left and right heart are represented by trapezoidal shape stiffness for better simulation results. The Eisenmenger syndrome is simulated using a resistance (septal resistance) connected between the left ventricle and right ventricle points of the model. Matlab® is used for the model implementation. In this model, although there is a remarkable increase in the pulmonary artery pressure and right ventricle pressure, left ventricle pressure, aortic pressure, aortic flow, and pulmonary compliance decrease in the Eisenmenger syndrome. In addition, left-to-right septal flow reversed in these diseases. Conclusion: Our model is effective and available for simulating normal cardiac conditions and cardiovascular diseases, especially the Eisenmenger syndrome.

Summary

Background and objectives: Autonomic circulatory regulation and airway anatomy in children are significantly different from those in adults. There is no available published data to compare whether there is a clinically relevant difference in the haemodynamic responses to fibreoptic orotracheal intubation (FOI) under the same conditions between children and adults. In this randomized clinical study, we compared the blood pressure (BP) and heart rate (HR) changes during FOI in 40 children aged 3.5–9 yr and 40 adults aged 21–57 yr, ASA 1 scheduled for elective plastic surgery under general anaesthesia requiring orotracheal intubation. Methods: Anaesthesia was induced with intravenous (i.v.) injection of fentanyl and propofol, and face mask inhalation of isoflurane before FOI. Noninvasive BP and HR were recorded before induction (baseline values), after induction (postinduction values), at intubation and for 5 min after intubation at 1-min intervals. The percentage changes of BP and HR at each time point were calculated. Results: In children and adults, HR at intubation and 1–3 min after intubation were significantly higher than baseline and postinduction values. In adults, BP at intubation increased significantly compared to the postinduction values but did not exceed baseline values. In children, BP at intubation and 1 min after intubation were significantly higher than postinduction and baseline values. As compared to adults, FOI caused a more significant pressor response in children. The percentage changes of BP at intubation and 1 min after intubation were larger in children than in adults. However, there was no significant difference in the percentage change of HR during the observation between children and adults. Conclusions: Under general anaesthesia, FOI might cause a more significant pressor response in children than in adults.

Summary

Background and objective: The GlideScope® videolaryngoscope is a newly developed laryngoscope for tracheal intubation recently introduced into clinical anaesthesia. In this randomised clinical study, we compared the haemodynamic responses to orotracheal intubation using a GlideScope® videolaryngoscope and a fibreoptic bronchoscope. Methods: Fifty-six adult patients, ASA I–II scheduled for elective plastic surgery under general anaesthesia requiring orotracheal intubation were randomly allocated to either the GlideScope® videolaryngoscope group or the fibreoptic bronchoscope group. After a standard intravenous anaesthetic induction, orotracheal intubation was performed. Noninvasive blood pressure and heart rate were recorded before and after induction, at intubation and for 5 min after intubation at 1 min intervals. Results: As compared with the post-induction values the orotracheal intubations using a fibreoptic bronchoscope and a GlideScope® videolaryngoscope resulted in the significant increases in blood pressures which did not exceed their baseline values. In the two groups, heart rates at intubation and within 2 min after intubation were significantly higher than their baseline values. However, there were no significant differences in blood pressures and heart rates at all time points, their maximal values and maximal percent changes during the observation and the times required to reach their maximal values between the two groups. Conclusions: The orotracheal intubations using a fibreoptic bronchoscope and a GlideScope® videolaryngoscope produce similar haemodynamic responses.

Summary

Objective: The objective of this study was to describe the diastolic pressure–flow relationship and to assess critical occlusion pressure in arterial coronary bypass grafts in human beings. Methods and results: Fifteen patients were studied following elective surgical coronary artery bypass grafting. Flow in the left internal mammary artery bypass to the left anterior descending artery was measured and simultaneously, aortic pressure, coronary sinus pressure and left ventricular end-diastolic pressure were recorded. The zero-flow pressure intercept as a measure of critical occlusion pressure was extrapolated from the linear regression analysis of the instantaneous diastolic pressure–flow relationship. Mean diastolic flow was 46 ± 17 mL min−1, mean diastolic aortic pressure was 60.5 ± 10.0 mmHg. Diastolic blood flow was linearly related to the respective aortic pressure in all patients (R-values 0.7–0.99). The regression lines had a mean slope of 2.1 ± 1.2 mL min−1 mmHg−1. Mean critical occlusion pressure was 32.3 ± 9.9 mmHg and exceeded mean coronary sinus pressure and mean left ventricular end-diastolic pressure by factors of 3.1 and 2.6, respectively. Conclusions: Our data demonstrate the presence of a vascular waterfall phenomenon in the coronary circulation after internal mammary artery bypass grafting. Critical occlusion pressure in arterial grafts considerably exceeds coronary sinus pressure as well as left ventricular end-diastolic pressure and should thus be used as the effective downstream pressure when calculating coronary perfusion pressure. Our data further suggest that the slope of diastolic pressure–flow relationships provides a more rational approach to assess regional coronary vascular resistance than conventional calculations of coronary vascular resistance.

Background and objective: The effects of administering albumin 5%, hydroxyethylstarch 6% and succinylated gelatine 4% on oxygen transport and left ventricular function were prospectively investigated in different experimental conditions: baseline, fluid load, after 10 min of myocardial ischaemia and after reperfusion.

Methods: Twenty-seven rabbits received at random one of three colloids in escalating boluses over 10–15 min to achieve left ventricular end-diastolic pressures (LVEDP) between 8 and 10 mmHg. A branch of the left anterior descending coronary artery was then temporarily occluded by a ligature and released after 10 min. Myocardial function was assessed using left ventricular pressure recordings and dimension data obtained from ultrasound crystals inserted onto the ventricular wall. Blood was sampled for the determination of oxygen delivery and consumption, the oxygen extraction ratio, acid-base status, and glucose and lactate concentrations.

Results: Administration of the colloids similarly increased oxygen delivery and improved left ventricular function in all groups. Peak rate of pressure development (dP/dtmax) and oxygen delivery were reduced during ischaemia and reperfusion. The decrease in dP/dtmax was more pronounced in the hydroxyethylstarch group.

Conclusions: Administration of albumin 5%, hydroxyethylstarch 6% and succinylated gelatine 4% had similar effects on oxygen delivery and myocardial function. After ischaemia and during reperfusion, the decrease in myocardial function was most pronounced with hydroxyethylstarch 6%.

Background and Objective To investigate the response to general anaesthetics of different sodium channel subtypes, we examined the effects of pentobarbital, a close thiopental analogue, on single sodium channels from human ventricular muscle and compared them with existing data from human brain channels.

Methods Sodium channels from preparations of human ventricular muscle were incorporated into planar lipid bilayers in the presence of batrachotoxin, a sodium channel activator. Single channel currents were recorded in symmetrical 100mmolL−1 and 500mmolL−1 NaCl before and after the addition of the anaesthetic pentobarbital (0.34–1.34mmolL−1).

Results The blocking effect of pentobarbital on the fractional open time had an IC50 of 690 μmol L−1 in 500 mmolL−1 NaCl, whereas it had a significantly lower IC50 of 400 μmol L−1 in 100 mmolL−1 NaCl. Pentobarbital caused a significant shift of steady-state activation to hyperpolarized potentials (fmax = −42 mV, IC50=2 mmolL−1). This effect was independent of NaCl concentration.

Conclusion Despite pharmacological and electrophysiological differences between human cardiac and human brain sodium channels their responses to pentobarbital are similar. The finding of channel block being dependent on the electrolyte concentration is novel for sodium channels.

In anaesthetized dogs, stellate ganglion blockade led to a moderate disturbance in left ventricular diastolic function. We investigated the effect of a left-sided block, following injection of 10 mL bupivacaine 0.5%, on echocardiographic variables of ventricular function in eight otherwise healthy patients with sympathetically mediated pain syndromes. After the blockade, heart rate (control: 66±3 (mean± SEM), block: 64± 3 min−1) and mean arterial blood pressure (88.5±6.0 vs. 84.0±8.1 mmHg) were unchanged, but afterload decreased (end-systolic meridional wall stress; 69.6±9.9 vs. 59.8±7.1, P<0.05). Stroke volume increased from 71.2±8.1 to 79.6±7.4 mL, P <0.05. Variables of systolic function were unchanged, but relaxation was prolonged (isovolumic relaxation time; 71±5 vs. 81±4 ms, P<0.05). In patients who were ASA I, there was a small impairment in echocardiographic variables during ventricular relaxation after a left stellate ganglion blockade. This small effect did not compromise ventricular function, and the heart responded with a small stroke volume increase to the simultaneous afterload reduction.