Applied cardiopulmonary pathophysiology : ACP最新文献

During recent years interest has focused on two completely fluorinated ethers, desflurane and sevoflurane, which promise a shorter induction of and emergence from anesthesia. Their physicochemical properties differ from isoflurane, enflurane and halothane, thus requiring new technical equipment and leading to a change in anesthesiological procedures. Low-flow anesthesia with desflurane can be performed, the technical equipment is available, especially vaporizers and gas analyzers. In contrast to anesthesia with isoflurane, enflurane and halothane, the initial high-flow wash-in period with desflurane can be shorter and the vaporizer setting can remain unchanged after fresh gas flow reduction. In order to administer desflurane and sevoflurane in closed circuit technique, new technical equipment is needed. Therefore, a computer controlled anesthesia machine was modified and the feedback mechanism to maintain the end-tidal anesthetic concentration was simulated. Isoflurane, desflurane or sevoflurane needed the same time for wash-in. Wash-out was slower with isoflurane; however, the technical equipment should be adapted to increase the elimination of the new agents. The consumption of desflurane and sevoflurane is effectively reduced by low-flow and closed circuit anesthesia.

The aim of the study was to compare the residual heparin in the composition of autologous blood retransfusion units harvested during cardiac surgery under extra-corporeal circulation with three different intraoperative autologous blood savers. In this institutionally approved study, thirty patients undergoing CABG were randomly assigned to three groups according to the intraoperative blood saver used during the procedure: {HAEMONETICS Cell Saver IV (n=10)--DIDECO/SHILEY STAT (n=11)--BRAT 250 (n=9)}. Anaesthesia and conduct of bypass were identical for all patients. The initial heparin dose was 300IU-kg -1 and was supplemented to maintain an activated coagulation time over 480s. The harvested blood was processed according to the procedure defined by each equipment manufacturer. The biological study was performed on the first blood sediments sampled before administering protamine to the patient. Blood cell count, residual heparinemia assessed by its anti-Xa activity using an amidolytic method {STACHROM HEPARIN--DIAGNOSTICA STAGO}, and weight of the blood sediment proteins were determined. Demographic data did not differ between groups. Despite a slight but significant difference between groups, the three devices provided virtual elimination of heparin. The total protein content was significantly higher in the BRAT 250 group. There was a highly significant positive correlation between the anti-Xa activity and total protein content. Haematologic data were within clinically acceptable ranges.

Percutaneous cardiopulmonary bypass has been introduced to support circulation in critical patients. In our preliminary experience we resuscitated two patients who sustained a prolonged cardiac arrest (52 min. and 31 min.) after coronary angiography and elective cardiac surgery, respectively. Cannulation was achieved percutaneously within 10 min. in both cases. Pump flow ranged from 2 to 31/m. Total support lasted from 52 min. to 180 min.. Both patients were successfully weaned. Patient 1 was declared brain dead and expired 17 days later. Patient 2 was discharged from the hospital and is doing well. Cannulation was attempted in a third patient after 30 min. of cardiac arrest. Despite surgical cut down of the femoral vessels, it was impossible to advance the arterial cannula because of bilateral occlusive disease. We conclude that PCPS is a powerful technique in selected patients to recover a stable cardiac function after prolonged cardiac arrest.

The IVOX device represents an early prototype of an intravascular membrane oxygenator that is capable of transferring significant amounts of O 2 and CO 2. It employs new hollow-fiber membrane technology and thromboresistant coatings that should allow the development of a membrane oxygenator that can be placed either intravascularly or ex vivo to provide significant gas exchange without the adverse effects seen in prior ECMO studies including bleeding from heparinization and plasma breakthrough resulting in the gradual deterioration of gas exchange. It may well be that this technology will eventually supplant conventional mechanical ventilation in the support of patients requiring intensive ventilator assistance or in those that are long term weaning problems, thus avoiding the not insignificant problems associated with high intensity and/or long term mechanical ventilation.

Since the first long term successful single lung transplant in 1983, followed by a successful double lung transplant in 1986, lung transplantation has become established world-wide as an accepted option in the treatment of end-stage respiratory disease of various etiologies. Both procedures carry acceptable morbidity and mortality rates with the actuarial 5 year survivor rate of 80%. Single or double lung transplantation offers many advantages over heart-lung transplantation and is gradually supplanting the latter in most centers with certain exceptions. Differentiating injection from rejection continues to be a major problem but with added experience and new diagnostic tools this obstacle will be overcome.

Substantial technological progress has been made recently in the area of perioperative cardiovascular monitoring. Specialized monitoring may be performed for problems identified by preoperative evaluation. New technologies have been developed for monitoring the blood pressure continuously and non-invasively. Electrocardiographic monitoring of perioperative ischemia has been characterized. Newer techniques in echocardiography such as the use of contrast, and tissue characterization allowed improved monitoring of ischemia as well as ventricular function. Continuous monitoring of cardiac output can be performed by impedance cardiography and Doppler ultrasound and by continuous thermodilution. Improved rules for the differentiation of ventricular from supraventricular tachycardia have been developed. Detection of MI has been facilitated by new scintigraphic and enzymatic techniques. In critically ill patients, multi-system monitoring may be required to adequately assess the cardiovascular system.

Circulatory shock represents critical reductions of blood flow to tissues with curtailed delivery of energy substrate and especially oxygen. Generation of lactic acid highlights the onset of anaerobic metabolism and represents the clinical hallmark of perfusion failure. For the purpose of classification, prognostication and management, we now recognize four mechanisms by which circulatory shock may evolve. The first three represent states of decreased cardiac output in which shock may stem from acute decreases in circulating volume (hypovolemic shock), loss of patency to mainstream blood flow (obstructive shock) or impaired myocardial function (cardiogenic shock). The fourth one represents altered distribution of blood flow such that perfusion failure may emerge despite increases in total blood flow (distributive shock).