[Definitions in mechanical ventilation]. / Conceptos de ventilación mecánica.

Mechanical ventilation can be defined as the technique through which gas is moved toward and from the lungs through an external device connected directly to the patient. The clinical objectives of mechanical ventilation can be highly diverse: To maintain gas exchange, to reduce or substitute respiratory effort, to diminish the consumption of systemic and/or myocardiac O2, to obtain lung expansion, to allow sedation, anesthesia and muscle relaxation, and to stabilize the thoracic wall, etc. Ventilation can be carried out by negative extrathoracic pressure or intermittent positive pressure. According to the cycling mechanism, positive-pressure ventilators are classified as pressure-cycled, flow-cycled, or mixed, and according to the type of flow in continuous-flow ventilators, as intermittent flow or constant basic flow. Finally, high-frequency ventilators are classified according to their high-frequency mechanism as intermittent positive pressure, oscillatory high-frequency and high-frequency jet ventilators.

[Techniques and complementary techniques. Intubation, sedation and adaptation to mechanical ventilation]. / Técnicas y tratamientos complementarios. Intubación, sedación y adaptación a la ventilación mecánica.

Endotracheal intubation consists on placing a tube in the trachea either through the mouth (orotracheal intubation) or through the nose (nasotracheal intubation). Although maintaining the airway patent and providing adequate ventilation are not synonymous with intubation, this procedure provides a closed ventilation system while ensuring patency and protecting the airway. Intubation is fairly safe in oxygenated and physiologically stable patients but it is not free from serious complication and consequently it should always be considered as a dangerous technique, especially in critically-ill patients. In addition, given that the anatomy of the airway in children differs according to age, the techniques used to intubate show considerable variations. For all these reasons and despite the often urgent nature of airway problems in children, the placement of an endotracheal tube must be approached in a deliberate and calm manner if trauma to the airway and patient instability are to be avoided. Thus, whenever circumstances permit, intubation should be carefully prepared with assessment of factors that might cause problems such as the indication for intubation, possible airway abnormalities, risk of aspiration, and hemodynamic, respiratory and neurological status. Such and evaluation allows the most appropriate intubation technique to be chosen.

[Cerebral infarct secondary to carotid artery dissection]. / Infarto cerebral isquémico por disección de arteria carótida interna.

Dissection of the internal carotid artery is an important cause of ischemic stroke in children and young patients. Trauma and/or an underlying structural defect of the arterial wall have been suggested to be predisposing factors. The typical patient presents with ipsilateral headache or neck pain, ipsilateral Horner's syndrome and delayed ischemic symptoms. Diagnosis is given by ultrasound, transcranial Doppler, magnetic resonance imaging, magnetic resonance angiography and conventional angiography. Treatment of this type of injury includes anticoagulation therapy, antiplatelet therapy and surgery. We report a 14-year-old boy with internal carotid artery dissection who presented with ischemic stroke.

Oxygen consumption, lactate metabolism, and gastric intramucosal pH in an experimental liver transplantation model.

OBJECTIVE: To assess the usefulness of measuring whole-body oxygen consumption (VO2), arterial lactate concentration, and gastric intramucosal pH (pHi) as parameters for evaluating hepatic graft viability in a model of experimental liver transplantation. DESIGN: Experimental, prospective study. SETTING: Hospital laboratory for experimental surgery. SUBJECTS: Twenty-eight Landrace-Largewhite pigs: 14 donors and 14 recipients. INTERVENTIONS: Orthotopic liver transplantation. Two groups were differentiated by graft preservation status: an optimal-graft group (group 1), which received donor livers that had been preserved in Collins solution at 4 degrees C for <4 hrs (n = 7), and an injured-graft group (group 2), which received donor livers that had been preserved in Collins solution at 4 degrees C for >24 hrs (n = 7). MEASUREMENTS AND MAIN RESULTS: Hemodynamic parameters, variables related with systemic and hepatic oxygen and lactate metabolism, gastric pHi, and arterial pH were measured at two stages: a) preanhepatic stage; and b) neohepatic stage (60 mins after reperfusion). There were no differences in VO2 between graft groups or stages. In the neohepatic stage, hepatic oxygen extraction and lactate turnover were significantly higher in the optimal-graft group than in the injured-graft group. In the neohepatic stage, gastric pHi decreased significantly and arterial lactate concentrations increased significantly in both groups. CONCLUSIONS: Changes in hepatic VO2 cannot be detected by VO2 measurements. Optimal-state grafts increased their lactate turnover as a result of substrate overload, but injured grafts did not. Therefore, the evolution of arterial lactate concentrations in the immediate postoperative period may be useful for the early evaluation of transplanted livers. Gastric pHi can be a useful measurement in the immediate posttransplantation period for differentiating between hyperlactacidemia produced by liver dysfunction (normal pHi) and hyperlactacidemia produced by lactate generation as a consequence of inadequate tissue oxygenation or of a mixed origin (abnormal pHi).

Intubación, sedación y adaptación a la ventilación mecánica / Intubation, sedation and adaptation to mechanical ventilation

La intubación traqueal consiste en la colocación de un tubo en la tráquea, bien a través de la boca (intubación orotraqueal) o de la nariz (intubación nasotraqueal). Aunque el mantenimiento de una vía aérea permeable y una adecuada ventilación no es sinónimo de intubación, ésta asegura y protege la vía aérea al tiempo que proporciona un sistema cerrado de ventilación. Aunque la intubación es un procedimiento bastante seguro en el paciente estable y adecuadamente oxigenado, no es una técnica exenta de complicaciones graves. Por este motivo, debe ser considerada siempre una técnica de riesgo, sobre todo en el paciente crítico. Además, dado que la anatomía de la vía aérea en el niño es diferente según la edad, la técnica de intubación presenta importantes variaciones, que deben ser tenidas en cuenta. Por todo ello, a pesar de la naturaleza urgente de la patología de la vía respiratoria en niños, la colocación de un tubo endotraqueal debe ser abordada de forma organizada y juiciosa para evitar traumatismos de la vía aérea y deterioro de la situación clínica del paciente. De este modo, siempre que las circunstancias lo permitan, la intubación debe prepararse cuidadosamente, valorando las circunstancias que puedan dificultarla como: motivo de la intubación, posibles malformaciones de la vía aérea, riesgo de aspiración, situación hemodinámica, respiratoria y neurológica. Esta valoración permitirá decidir la técnica de intubación más apropiada (AU)

Infarto cerebral isquémico por disección de arteria carótida interna / Ischemic stroke secondary to carotid artery dissection

La disección de la arteria carótida interna es una causa importante de ictus isquémico en niños y pacientes jóvenes. En la patogenia se han implicado traumatismos y/o un posible defecto estructural de la pared arterial. Las manifestaciones clínicas típicas incluyen cefalea o dolor de cuello y síndrome de Horner en el lado de la disección, con la aparición después de síntomas isquémicos cerebrales. La ecografía, el Doppler transcraneal, la resonancia magnética (RM), la angiorresonancia y la angiografía proporcionan el diagnóstico. Las opciones de tratamiento comprenden anticoagulantes, antiagregantes plaquetarios y cirugía. Presentamos un adolescente de 14 años con un ictus isquémico secundario a disección de la arteria carótida interna. (AU)