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At least 91 records · Page 5Linked to original sources
PubMed2006

Model of arterial tree and peripheral control for the study of physiological and assisted circulation.

Peripheral vasomotion, interstitial liquid exchange, and cardiovascular system behaviour are investigated by means of a lumped parameter model of the systemic and peripheral circulation, from the aortic valve to the venules. This modelling work aims at combining arterial tree hemodynamics description, active peripheral flow regulation, and fluid exchange. The arterial compartment is constructed with 63 RCL segments and 30 peripheral districts including myogenic control on arterioles, metabolic control on venules, and Starling filtration through capillary membrane. The arterial behaviour is characterised as to the long term stability of pressure/flow waves in the different segments. Peripheral districts show autoregulatory capabilities against pressure changes over a wide range and also self-sustained oscillations mimicking vasomotor activity. A preliminary study was carried out as to the model response to changes induced by cardiopulmonary bypass (CPB). Among the induced alterations, the system responds mainly to hemodilution, which increased peripheral fluid loss and oedema beyond the compensatory capabilities of local regulation mechanisms. This resulted in an overall increase total arterial resistance. Local transport deficits were assessed for each district according to the different metabolic demand. This study shows the requirement of a suitable description of both arteries and peripheral mechanisms in order to describe cardiovascular response non-physiological conditions, as well as assisted circulation or other pathological conditions.

Arteries↗
PubMedDate not supplied

[Synchronous mechanical heart massage during assisted circulation].

In tests on dogs specially devised cardiac massage appliances and a monitoring system synchronizing the mechanical massage with the R wave on the ECG were used in carrying out a synchronous mechanical chest massage in conditions of an experimentally induced incompetence of the cardiac ventricles. Optimal parameters of the hemodynamics were recorded with the massage proceeding in such a manner, when mechanical action on the cardiac ventricles coincided with termination of the maximum pressure period of the myocardium. The synchronous ancillary cardiac massage effected under conditions of ventricular incompetence was found to be attended by a rise of cardiac output and increased aortic pressure, falling tension in the auricles and normalization of the acid-base equilibrium figures. Synchronization of the massaging appliance operation with cardiac contractions is an effective method of assisted circulation in acute incompetence of the heart valves.

Animals↗
PubMedDate not supplied

Development and clinical application of a next generation implantable echocardiography probe for monitoring cardiac function under assisted circulation after open heart surgery.

Post-operative cardiac function generally is monitored by electrocardiography, invasive measurement of blood pressure, and determination of hemodynamic variables, such as pulmonary pressures and cardiac output with a Swan-Ganz catheter. In recent years, transesophageal echocardiography has been introduced into clinical use, but it is not a popular method of monitoring for various reasons, including the difficulty of application to unconscious post-operative patients. Since 1991, we have been developing a small implantable echocardiography probe. This probe was tested in 15 patients who underwent open heart surgery for severe left ventricular hypofunction, and its clinical utility was demonstrated. No deaths occurred in this series. The implantable echocardiography probe allowed post-operative cardiac function to be monitored in real-time. The ejection fraction, the cardiac output, the status of valves after valvuloplasty, the presence of cardiac tamponade, and other variables could be assessed. The echocardiography probe can be positioned at any site where specific information is desired during surgery. It can be inserted as easily as a pericardial drain tube and is removed in the same manner when no longer necessary. This probe has the potential to be useful for monitoring patients on assisted circulation after cardiac surgery.

Assisted Circulation↗
PubMed1998

Development of vibrating flow pump for left ventricular assist circulation.

Vibrating flow pump (VFP) can generate high frequency oscillated blood flow within 10-40 Hz. In this study, new type VFP was developed as a ventricular assist device. Left Ventricular assist circulation using VFP were performed as aseptic animal experiments using goats. hemodynamic parameters were recorded continuously at awake state. Driving frequency of VFP was 25 Hz and pump flow rate was controlled to approximately 2 l/min. Frequency of VFP was 25 hz and pump flow rate was controlled to approximately 2 L/min. Frequency analysis method was used for analyzing hemodynamics. The peak of power was observed at 25 Hz from the Fourier transformation of blood flow waveform. Systemic vascular resistance was decreased by the start of left ventricular assistance using oscillated blood flow. No fatal arrhythmia was observed during this study. As the conclusion, new type VFP has a sufficient performance for left ventricular assistance. Small size blood pump may be enabled by the oscillated blood flow because VFP is driven at high frequency moving with short stroke volume.

Animals↗
PubMed1991

Hepatic venous oxygen saturation monitoring in patients with assisted circulation for severe cardiac failure.

In order to assess the adequacy of hepatic perfusion, hepatic venous oxygen saturation (ShvO2) was monitored in five patients undergoing mechanical circulatory support. Two patients were with intra-aortic balloon pumping (IABP), one was with a left ventricular assist device (LVAD), and two were with biventricular assist devices (BVAD). The mean ShvO2 values during assistance in each patient ranged from 27 to 84%. One patient with IABP showed persistently low ShvO2 (less than 30%) in spite of higher mixed venous oxygen saturation (SvO2) and subsequently developed hepatic dysfunction and multiple organ failure. In another patient, ShvO2 was 22% on average during LVAD, but increased to greater than 50% after adding a right ventricular assist device (RVAD). Of 3 patients with persistently high ShvO2 (44-80%, on average), only one developed hepatic failure--probably from prior severe shock--and the other two did not develop hepatic failure. There was a significant negative correlation between ShvO2 and splanchnic excess lactate, the parameter of anaerobic metabolism in the splanchnic area. In contrast, there was no correlation between simultaneously measured ShvO2 and SvO2 values when analyzed in a range of SvO2 below 70%. ShvO2 monitoring may be useful for evaluation of hepatic perfusion status in the management of critical patients, requiring assisted circulation.

Heart Failure↗
PubMed1989

Successful treatment of acute postoperative right heart failure with low-dose prostaglandin e(1) and assisted circulation.

Immediately after undergoing emergency mitral valve replacement, a 60-year-old woman suffered acute postoperative right heart failure and could not be weaned from cardiopulmonary bypass, despite treatment with multiple drugs. Circulatory assistance was instituted by means of femoro-femoral bypass with a roller pump and a hollow-fiber oxygenator; inotropic drugs and drugs aimed at reducing pulmonary vascular resistance (nitroprusside, moxaverine, and isoproterenol) were also given. The patient's systolic pulmonary pressure underwent a progressive decrease, but her systolic systemic pressure remained below 60 mmHg until 8.5 hours after aortic clamp release, when we were able to begin an infusion of prostaglandin E(1), a drug not readily available in our hospital. Fifteen minutes after the infusion was started, at 5 ng/kg/min, the patient's systolic systemic pressure reached 85 mmHg and her systolic pulmonary pressure decreased to 55 mmHg. During the next 2 hours, epinephrine treatment was discontinued, and the assisted circulatory flow was reduced to 0.5 L/min/m(2), while the PGE(1) infusion was increased to 10 ng/kg/min. Assisted circulation was soon discontinued, and the patient's hemodynamic condition remained stable.

Journal Article↗
PubMed1993

Clinical experience of assisted circulation with a centrifugal pump at Tokyo Women's Medical College.

In postpericardiotomy patients, the use of pulsatile pumps is limited in a semielective fashion to patients whose postoperative marginal hemodynamics are expected preoperatively. Since 1989, 25 patients have undergone assisted circulation with a centrifugal pump: 15 (60%) were weaned from the pump, and 7 (28%) survived. In 1988, we heparin-coated the Bio-Pump using the Carmeda technique and developed a totally heparin-coated left heart bypass system together with heparin-coated cannulas and tubing. Four postpericardiotomy patients underwent left heart bypass with this system without heparin for 2 to 9 days. No thrombus was detected in the system. Left heart bypass with a centrifugal pump has been used as a supportive method in surgical repair of thoracic or thoracoabdominal aortic aneurysm. To overcome intraoperative hypothermia and hypoxia, we used a small membrane oxygenator with a heat exchanger in 11 patients, and postoperative recovery dramatically improved. We also developed a preassembled percutaneous cardiopulmonary support (PCPS) system with an automatic priming function using Terumo's straight path centrifugal pump and small membrane oxygenator in cooperation with the Terumo Corporation. This system was used in a patient with cardiogenic shock after acute myocardial infarction. The setup and priming took only 5 min, and 2.5-3.5 L/min of flow was obtained.

Adult↗