Acta chirurgica Scandinavica. Supplementum最新文献

Postoperative pulmonary complications are not uncommon, and the factors that contribute to lung dysfunction are well documented. Postoperative pain, spasm, and paralysis are all known to reduce lung function, although relief of pain does not completely restore function. Rather, diaphragmatic dysfunction has been found to persist even with adequate pain relief. Functional residual capacity is reduced both by the supine position and anesthesia. During anesthesia, the reduced FRC can contribute to airway closure during expiration and to a compression atelectasis that in turn precipitates hypoxemia and infection. Muscle paralysis can also create or contribute to atelectasis. Microthromboembolism impedes perfusion distribution, adding to the other causes of a ventilation-perfusion mismatch. Different anesthetic techniques and intraoperative management may help prevent or reduce the incidence of postoperative lung complications.

The effects of continuous lumbar epidural anesthesia and two types of general anesthesia on blood loss and hemodynamics during and after total hip replacement were compared in three groups of patients. Fourteen patients received local anesthetics via continuous lumbar epidural administration; 10 patients received inhalational anesthetics and breathed spontaneously after endotracheal intubation; and 14 received artificial ventilation after intubation and intermittent intravenous (i.v.) injections of pancuronium and fentanyl. The results documented that both intraoperative and postoperative blood losses were significantly reduced in patients subjected to total hip replacement under lumbar epidural anesthesia as compared with the patients receiving the two general anesthetic techniques. Hemodynamic differences explained the differences in blood loss. The epidural anesthesia induced hypotension on the arterial and venous sides as compared with the two general anesthetic techniques. Inhalational anesthesia also induced hypotension on the arterial and venous sides intraoperatively as compared with general anesthesia with artificial ventilation. Postoperatively, the hemodynamics of the general anesthesia groups were similar, and no differences in blood loss occurred. Continuous' epidural anesthesia can be viewed as a tool to achieve hypotensive anesthesia--notably on the venous side--for the purpose of minimizing blood loss. The reduction in blood loss associated with lumbar epidural anesthesia is beneficial in decreasing the hazard and cost of blood transfusion.

Deep vein thrombosis and pulmonary embolism are significant hazards of surgery, especially in orthopedic procedures. However, the true incidence of these complications is unknown. Many surgeons are now using prophylactic methods to prevent the postoperative occurrence of thromboembolic disease. Pneumatic compression devices are recommended in some instances, especially in cases where increased bleeding could be devastating. Several pharmacologic agents are also used, alone or in combination with pneumatic devices. These include subcutaneous heparin, warfarin, dextran, and aspirin. Each agent has advantages and disadvantages. The US National Institutes of Health (NIH) and numerous ongoing clinical trials are attempting to establish recommendations and guidelines for the use of prophylaxis against postoperative deep vein thrombosis and pulmonary embolism.

Studies have shown that lumbar epidural and spinal anesthesia seem to offer two distinct clinical advantages over general anesthesia, particularly in total hip replacement patients. These major regional blocks reduce the frequency of deep vein thrombosis and pulmonary embolism and reduce intraoperative and postoperative blood losses. The beneficial effects on thromboembolism are probably explained by several factors, such as hyperkinetic blood flow in the lower legs, reduced tendency to coagulation, and improved fibrinolytic function. The effects of local anesthetics on leukocytes, platelets, erythrocytes, and plasma proteins and on the interactions among various blood cells and endothelial cells are other factors in the protection against thromboembolism. Sympathicomimetic agents (i.e., epinephrine in the local anesthetic solution together with ephedrine given prophylactically to maintain a stable blood pressure) probably also play a significant role, notably on fibrinolytic function. The reduction in blood loss and thus in transfusion requirements may also be important.

The effect of anesthetic methods on mental function has been the subject of much discussion and debate over many years. Although it is commonly recognized that sedative, narcotic, and anesthetic agents have observable effects on cerebral function at the time of administration, more subtle and less easily detectable effects may persist into the postoperative period. Identifying and describing the effects of these drugs requires reliable and reproducible methods of measurement. The tests used for evaluating the effect of anesthetic methods on mental function are reviewed. The roles played by intraoperative and postoperative factors and their possible involvement in detectable decrement in mental function are described. Early postoperative effects of anesthetic methods on cognitive function are discussed, and the evidence for prolonged changes in mental function following anesthesia (particularly in the elderly) is reviewed.

Numerous experimental and clinical studies have documented that trauma-including surgery-alters the immune response, and that the response is a function of the magnitude of the injury or operation. The abnormalities seen after surgical operations on humans or animals include decreased antibody response, decreased neutrophil chemotaxis, decreased delayed-type hypersensitivity reaction, abnormal neutrophil adherence, serum immunosuppressive factors, decreased fibronectin levels, reduced serum opsonic activity, and reduced efficacy of interleukin-2. These abnormalities involve all aspects of the host defense mechanisms, both the cellular and humoral mediators and the specific and nonspecific immune responses. The capacity to control these responses in surgical patients may have important clinical applications.