Annales françaises d'anesthèsie et de rèanimation
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To review anaesthesia ventilators in current use in France by categories of ventilators. ⋯ Anaesthesia ventilators can be allocated into three groups, depending on whether they readminister expired gases or not or allow both modalities. Contemporary ventilators provide either constant volume ventilation, or constant pressure ventilation, with or without a pressure plateau. Ventilators readministering expired gases after CO2 absorption, or closed circuit ventilators, are either of a double- or a single-circuit design. Double-circuit ventilators, or pneumatical bag or bellows squeezers, or bag-in-bottle or bellows-in-bottle (or box) ventilators, consist of a primary, or driving circuit (bottle or box) and a secondary or patient circuit (including a bag or a bellows or membrane chambers). Bellows-in-bottle ventilators have either standing bellows ascending at expiration, or hanging bellows, descending at expiration. Ascending bellows require a positive pressure of about 2 cmH2O throughout exhalation to allow the bellows to refill. The expired gas volume is a valuable indicator for leak and disconnection. Descending bellows generate a slight negative pressure during exhalation. In case of leak or disconnection they aspirate ambient air and cannot act therefore as an indicator for integrity of the circuit and the patient connection. Closed circuit ventilators with a single-circuit (patient circuit) include a insufflating device consisting either in a bellows or a cylinder with a piston, operated by a electric or pneumatic motor. As the hanging bellows of the double circuit ventilators, they generate a slight negative pressure during exhalation and aspirate ambient air in case of leak or disconnection. Ventilators not designed for the readministration of expired gases, or open circuit ventilators, are generally stand-alone mechanical ventilators modified to allow the administration of inhalational anaesthetic agents.
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Ann Fr Anesth Reanim · Jan 1997
Review[Right ventricular function: physiological and physiopathological features].
Sinus and conus constitute the two cavities of the right ventricle. They are anatomically and functionally different. The sinus is a flow-generator and the conus a pressure-regulator. ⋯ They are responsible for ventricular dilation and ischaemia with a decrease in cardiac output, generating a vicious circle. Treatment includes the removal of the cause, and the maintenance of systemic arterial pressure and biventricular contractility. It is difficult to assess the effects of intravenous vasodilators on right ventricular afterload.
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Barbiturates, etomidate and propofol decrease cerebral blood flow (CBF), mediated by a decrease in cerebral metabolism, thus decreasing intracranial pressure (ICP). As the reduction in CBF is secondary to a decrease in cerebral metabolism, these agents will have little effect on CBF or ICP in patients without active cerebral metabolic activity. Ketamine is usually not administered for the anaesthetic management of patients at risk of intracranial hypertension because of the reported increases in cerebral metabolism, CBF and ICP. ⋯ Desflurane and sevoflurane have similar effects. CO2 reactivity is preserved with all inhaled agents. In patients with increased ICP however, it would be preferable to avoid these agents or to administer very low doses.
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Haemodynamic effects of hypertonic saline solutions (HSS) have been extensively studied in animals and humans. Hypertonic sodium chloride (7.5%, 2,500 mOsm. L-1) either alone or combined with colloids, remains the standard solution. ⋯ Haemorrhagic shock is the main indication for small volume resuscitation with HSS. Other potential situations for the use of HSS are volume replacement in perioperative period, septic shock or burn injury and cardiopulmonary resuscitation. Before recommending the clinical use of HSS, additional clinical studies are required to substantiate the benefits of HSS over colloids.
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Early and efficient management of severely burned patients facilitates outcome improvement. Pre-hospital care includes fluid loading with 2 mL.kg-1/% burn over the first six hours, sedation and analgesia, prevention of hypothermia and ventilatory support for either critically burned patients or facial, cervical or pulmonary burn injury. The transient stay in a general hospital before transfer to a burn centre allows extension of initial care, the critical investigation for associated injuries (intoxication, multiple trauma) and to perform initial local treatment with sterile coverage or vaseline gauze after a revised assessment of the burned skin area, and possibly escharotomies. ⋯ Finally, chemical or electrical burn, radiation, associated CO intoxication or multiple trauma, as well as burn injury in infants, raise specific problems. With improvement in early intensive care, the survival rate of the most severely burned patients is obviously improving. New techniques in skin substitution will probably further improve the final outcome.