ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
-
The anaerobic threshold represents an objective measure of functional capacity and is useful in assessment of pulmonary and cardiovascular dysfunction. This study determined the anaerobic threshold in total artificial heart animals and evaluated the performance of the total artificial heart system. Five animals with total artificial hearts were put under incremental exercise testing after exercise training. ⋯ The value of the anaerobic threshold in total artificial heart animals implies that the performance capacity of a total artificial heart is not sufficient to meet the oxygen requirements of vigorously exercising skeletal muscle. The protocol does not allow for driving parameter changes during exercise, and this situation, combined with the manual mode of the control system used, was inadequate to allow the total artificial heart animals to exercise more vigorously. Using an automatic control mode might be helpful, as well as considering the relationship between indices of oxygen metabolism, such as oxygen delivery, oxygen consumption, and oxygen extraction rate, in the control algorithms in total artificial heart control systems.
-
Clinical Trial
Efficacy of extracorporeal life support in the setting of adult cardiorespiratory failure.
The efficacy of extracorporeal life support (ECLS, ECMO) in the management of severe adult cardiorespiratory failure remains controversial. The purpose of this review is to evaluate the authors' institutional experience with ECLS in adult patients. Between 1988 and 1993, 65 moribund patients with respiratory (n = 51) and cardiac (n = 14) failure were supported with ECLS. ⋯ The only prognostic indicator of survival that could be identified was the period of time on the ventilator before the initiation of ECLS (survivors = 3.0 +/- 2.4 days, nonsurvivors = 6.1 +/9- 4.0 days, P < 0.005). It is concluded that ECLS can be a life saving modality for the management of severe adult cardiorespiratory failure. Earlier institution of ECLS in the course of cardiopulmonary failure may improve outcome.
-
Improvements made in current generation perfluorocarbon emulsions (PFCEs) warrant renewed interest in PFCEs as an oxygen (O2) carrying substance during cardiopulmonary bypass (CPB). Before embarking on in vivo studies of PFCEs during CPB, an in vitro study was designed to: 1) demonstrate increased O2 content attributable to PFCEs, and 2) compare O2 transfer to a PFCE crystalloid mixture by four oxygenator designs (one bubble oxygenator, two hollow fiber membrane oxygenators, and one silastic membrane oxygenator). A circuit was designed to circulate fluid between a deoxygenating device and a test oxygenator. ⋯ Protocol I showed that the AVO2 differences and O2 transfer rates were higher in the crystalloid PFCE mixture than in the crystalloid solution, although statistical comparison was precluded by the small sample size. In protocol II, the hollow fiber and silastic membrane oxygenators had higher (P < 0.05) AVO2 differences and oxygen transfer rates than the bubble oxygenators at all flows and temperatures tested. Future trials to evaluate PFCEs during cardiopulmonary bypass should use hollow fiber or silastic membrane oxygenators, rather than bubble oxygenators, to maximize transfer of O2 to the PFCE.
-
The intravascular oxygenator and carbon dioxide removal device (IVOX; CardioPulmonics, Salt Lake City, UT) has been shown to perform 30% of the gas exchange in animals and patients with acute respiratory failure. Among the factors that limit gas exchange is the mass transfer resistance in the blood phase. To determine if a reduction in mass transfer resistance by mixing venous blood can enhance the O2 transfer and CO2 removal by IVOX, a right atrium-pulmonary artery venovenous bypass circuit was used in sheep to model the adult vena cava. ⋯ It is concluded that reduction in the mass transfer resistance by blood mixing improves gas exchange. Because O2 is more diffusion limited, it is more dependent upon mixing of blood for gas exchange than CO2. More design improvements to incorporate active mixing may further enhance the gas exchange performance of IVOX.
-
Comparative Study
Monitoring of blood gases during prolonged experimental cardiopulmonary bypass and their relationship to brain pH, PO2, and PCO2.
Eight adult goats under went 5 hr of normothermic cardiopulmonary bypass (CPB) with pulsatile (n = 3) and nonpulsatile flow (n = 5). PaCO2 was maintained at 30-40 mmHg and blood flow rate at 50 ml/min/kg. Brain tissue pH, PO2, and PCO2, arterial and venous blood gases, and other systemic variables were monitored. ⋯ Brain tissue PO2 closely followed the values of PvO2, suggesting that PvO2 can be an indicator of brain tissue PO2 during normothermic CPB and must be monitored during the procedure. Brain tissue acidosis is evidently related to neurologic dysfunction after CPB, and must be addressed. Replacement of the priming solution with whole blood or artificial blood, reduction of the priming volume, and application of vigorous pulsatile flow appear feasible interventions to mitigate brain tissue acidosis during CPB.