Anaesthesia for thoracic surgery in children

Introduction proliferate in number is uncertain, but it is approximately 2 years, when there are normally some During early life anatomical and physiological 300 million present (5). differences, immaturity, size constraints, and difThe diaphragm is a complete membrane by ferent pathology, define the practical limits of 8 weeks gestation. At birth, 10–30% of its striated transposing techniques of anaesthesia for adult muscle fibres are Type 1 (fatigue resistant) compared thoracic surgery into paediatric practice. In children with 50% in adults (6). undergoing thoracic surgery, the lungs are often healthy, the pathological process affecting other organs whereas adult thoracic surgical practise comprises patients with pulmonary pathology Physiological changes at birth compounded by surgical trauma. Anaesthesia for intrathoracic surgery in children involves preserving The first few breaths of extrauterine life overcome physiological stability, minimizing surgical the resistive forces of fluid in the lungs, surface pulmonary trauma, providing postoperative tension of the intra-alveolar air–liquid interface, and analgesia, managing pleural drains and above all, elastic recoil of the chest wall. integration with providers of postoperative care. An intrapleural pressure of−100 cmH2O has been described (7) but in most babies –20 cmH2O appears to suffice (8). Distribution of gas throughout the lungs Anatomy and physiology is achieved because expiratory intrapleural pressures Pulmonary development reach 20–30 cmH2O as a result of grunting respiration (9). The tracheobronchial tree arizes as a bud from the Blood flow through the pulmonary circulation oesophagus during the fourth week of intrauterine establishes as pulmonary vascular resistance (PVR) life. By the sixteenth week, terminal bronchioles are decreases in response to respiration and the larger completely formed (1). At 24 weeks, saccules, capable arterial oxygen and smaller carbon dioxide partial of functioning for gas exchange are formed (2) and pressures of extrauterine life. PVR decreases further alveolar type 2 (surfactant producing) cells are over the next 10 days as collagen and elastin are laid present (3). After 28 weeks, the area available for down in proximal vessels and there is increased gas exchange increases exponentially as alveoli demarcation between intimal and medial cells in proliferate (4) reaching around 50 million in number distal vessels: the net effect is an increased luminal by full term. The age at which alveoli cease to diameter and decreased medial thickness (10,11). Inadvertent hypoxaemia or acidosis at this stage may induce right to left shunting at atrial level because Correspondence to: S.R. Haynes, Department of Cardiothoracic of the immaturity and consequent lability of the Anaesthesia, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK. pulmonary vasculature (12).