Current anaesthesia and critical care最新文献

The induction of transplantation tolerance has become a major goal, because modern immunosuppressive therapy has not improved chronic rejection rates, and is associated with significant side effects. This article aims to explain the principles of immunological tolerance. Mechanisms of central tolerance involve deletion of self-reactive T cells. Mechanisms of peripheral tolerance are reviewed and also the identification of a subset of regulatory T cells which are characterised by the expression of the transcription factor FoxP3.

Interesting recent insights on the role of the ‘anti-inflammatory’ cytokine transforming growth factor β which can ultimately lead to the generation of inhibitory Tregs or inflammatory Th17 cells (CD4 helper T cells which secrete the pro-inflammatory cytokine IL17) are discussed.

There are many ways to induce experimental tolerance in animals, however these are difficult to translate tolerance into the clinical context. In addition, standard immunosuppressive agents are calcineurin inhibitors which block T cell activation and IL-2 production. These drugs not only inhibit the activation of effector T cells, but also Tregs, therefore inhibiting Treg driven tolerance induction. Other classes of immunosuppressive drugs should be introduced into the clinic to allow for the possibility of tolerance induction. Strategies to modulate immune responses following transplantation and their potential risks are discussed.

General anesthesia causes atelectasis and airway closure in dependent areas of the lung. Both kinds of collapse induce a deterioration of gas exchange characterized by a decrease in arterial oxygenation and an increase in dead space. The severity of this lung dysfunction is proportional to the amount of collapsed tissue that depends on anesthesia, surgical and patient’s factors.

Lung collapse can be partially prevented by decreasing FiO₂ and/or by applying CPAP during the induction of anesthesia. However, only lung recruitment maneuvers can resolve atelectasis completely. These recruitment maneuvers are ventilatory strategies aimed to restore the normal aeration of the lungs. The maneuvers consist in a brief and controlled increase in airway pressure to open up those pulmonary areas with collapse. Afterward, the lungs are ventilated with a protective strategy setting keeping the lungs open in time with enough positive-end expiratory pressure and low driving pressure. This article describes the physiological and clinical background of lung recruitment maneuvers applied during the intra-operative period.

Presently, the majority of anesthesia machines or workstations are ventilators that incorporate a classic circle system/circuit with a CO₂ absorber that allows rebreathing of exhaled gases. The performance characteristics of these machines are related to the physical structure of the breathing circuit. Limitations related to the classical circle breathing circuit are progressively disappearing with the arrival on the market of modern anesthesia machines with modified circular circuits, which offer a series of advantages in relation to the classic circular circuit. The present review describes the basic functional characteristics common to any anesthesia machine and that determine their clinical performance. The knowledge of these characteristics is essential for the clinical use of anesthesia machines and for analyzing their evolution.

Stroke due to intracerebral hemorrhage is a recognized life threatening but rare complication of eclampsia and severe pre-eclampsia. Literature reporting the anesthetic management of combined emergency cesarean section and craniotomy are scarce. We describe the anesthetic management of a 21-year-old primigravida who underwent combined emergency cesarean section and craniotomy for intracerebral hemorrhage secondary to severe pre-eclampsia. Management of a pregnant woman with an intracerebral bleed and the emergency situation is an anesthetic challenge. A combined procedure as above requires good communication and co-ordination between various specialities and attention to details to ensure successful maternal and neonatal outcome.

Organ transplantation remains the most cost-effective treatment for many patients with end-stage organ diseases. In clinical transplantation, the main concern is the continuing rise in the number of patients on transplant waiting lists and the widening imbalance between demand and supply of organs from suitable donors. In renal transplantation, the majority of kidneys available are recovered from heart beating donors (HBDs). In recent years, shortage of kidneys from these donors has led to using organs from non-heart-beating donors (NHBDs) to expand the donor pool. However, these organs are often exposed to periods of both warm and cold ischaemic damage which determine short-term and long-term functional and survival outcomes of allografts. Therefore, minimising organ responsiveness to ischaemic injury could be beneficial in improving immediate allograft function. A wide range of protocols and techniques are being developed aiming to minimise ischaemic damage and maintain organ viability between organ harvesting and transplantation. Hypothermic preservation is being used in many transplantation centres to reduce metabolic requirements and promote cellular tolerance to ischaemia. In this article, techniques used in ex-vivo organ preservation will be discussed as well as characteristics of perfusate solutions that are being used to prolong organ viability pre-transplantation.

Fat embolism syndrome is an unexpected and alarming complication that is difficult to actively prevent, hard to diagnose with confidence and has limitations in effective treatment modalities. The syndrome is a melange of respiratory, haematological, neurological and cutaneous symptoms and signs associated with trauma and other disparate surgical and medical conditions. The pathogenesis is still debated. It is clear that fat emboli are quite common yet the clinical syndrome is rare. Diagnosis is by pattern recognition as befits a syndrome, but the recently defined features on MRI could now be used to increase the probability of the diagnosis. Various therapeutic options have been tried and failed. At present steroids have a single meta-analysis suggesting benefit but it is in the trauma population where they may be contra indicated for other reasons, i.e. infection, so their place is ill defined. Supportive treatment is the mainstay.