Clinics in Anaesthesiology最新文献

Barotrauma is a well-recognized complication of positive pressure ventilation. Excessive pressure applied to the lungs causes widespread disruption of alveoli. The gas escapes into the perivascular space to form pulmonary interstitial emphysema (PIE). The small bubbles coalesce and stream towards the mediastinum. The gas either accumulates there, or if the pressure is continued, it moves up into the neck and over the body to form subcutaneous emphysema, ruptures the mediastinal pleura to cause a pneumothorax, or moves down alongside the aorta and oesophagus to form pneumoretroperitoneum and with even higher pressures, pneumoperitoneum. The danger from extra-alveolar air (EAA) in the form of pneumothoraces, is well recognized. However, gas in the other sites can also cause complications. Lung disruption caused by PIE can cause hypoxia and hypercarbia, as well as more chronic respiratory impairment in the form of bronchopulmonary dysplasia (BPD). Cardiorespiratory embarrassment can result from mediastinal emphysema and upper airways obstruction from subcutaneous emphysema. Splinting of the diaphragms and cardiovascular impairment can be caused by raised intraabdominal pressure associated with pneumoretroperitoneum and pneumoperitoneum. Like many conditions in medicine, the best way of managing barotrauma is prevention. There are now alternative ways of artificially maintaining gas exchange apart from conventional ventilation and PEEP. Techniques such as CPAP, reversed inspiration: expiration (I: E) ratios, IMV, LFPPV with ECRCO₂ and hypoxic pulmonary vasoconstriction can often maintain gas exchange at lower airway pressures than IPPV and PEEP. As a result, there is less cardiovascular depression and a much lower incidence of lung disruption by barotrauma.

Inhalation anaesthetics provide the basis for most of paediatric anaesthetics. The object of the anaesthetist is to provide the surgeon with ideal operating conditions and to provide the child with a safe anaesthetic. This can be done by understanding the advantages and limitations of the various inhalation anaesthetics and adjuvants. This provides the 'ideal’ anaesthetic state and in addition gives the anaesthetist enormous satisfaction.

Although advances in paediatric surgery and anaesthesia have virtually eliminated unexpected perioperative mortality, considerable morbidity remains. Pain and vomiting are common postoperative problems that are physically and psychologically harmful to the child. Pain can be reduced or eliminated by a planned approach to the conduct of anaesthesia and the management of the postoperative period. A continuous infusion of morphine or other opiate analgesics is safe even in small infants, minimizing the risk of respiratory depression and vomiting. Similarly, the use of long-acting local anaesthetic agents for neural blockade can guarantee profound analgesia for prolonged periods. The local and regional techniques employed in adults can be safely applied to co-operative children either intraoperatively or postoperatively. The incidence of vomiting after anaesthesia remains unacceptably high in most institutions. It can be reduced by avoidance of opiates for premedication and the use of continuous low-dose infusions of opiates and neural blockade for postoperative analgesia.

Infants and children, like adults, undergo a metabolic response to surgery including catabolic and anabolic phases. Although less profound, increased metabolism, fluid retention and wasting still occur. The infant in the first two years of life has a markedly reduced respiratory reserve. Immaturity, structural defects of the respiratory and other systems, and postoperative pain and abdominal distension may precipitate respiratory failure. The infant is also prone to airways obstruction, largely as a result of the small calibre of the airways in absolute terms. Facilities for paediatrically orientated intensive care must be available for hospitals contemplating neonatal and infant surgery. On most occasions, the need for postoperative cardiorespiratory support and intensive observation can be anticipated, although rarely it may be required as a result of unexpected complications.

This chapter describes the essential monitoring which should be practised on all paediatric patients having anaesthesia for routine surgical procedures. The requirements for respiratory, cardiovascular, temperature, neuromuscular and biochemical monitoring and the necessary relationship of these with clinical monitoring are discussed. The differences between adult and infant patients are emphasized. Some of the more complex newer techniques which have not yet found their way into everyday clinical practice are not considered. Monitoring assists the anaesthetist in fulfilling two essential requirements, the return of the patient from the operative period in the optimum condition and the prevention of those technological hazards inherent in any general anaesthetic that can result in the death of the patient, or serious damage before full recovery has occurred. There is no evidence to suggest that the more complex monitoring prevents the latter. The requirement is relatively simple monitoring conscientiously applied, and continuing attention and vigilance on the part of the anaesthetist.

Psychological preparation is probably more important than drug medication when preparing children before anaesthesia and operation.

At the preoperative visit, information should be addressed to the child in the presence of one or both of his parents. The anaesthetist should sit down and listen carefully, being prepared to explain over again serious matters already told but blocked by anxious parents.

Questions regarding parental presence during the induction should be answered in a straightforward manner carrying the conviction that whatever the decision, it will be taken aiming at what is best for the child.

Parental requests to be present during the recovery should always be granted in a paediatric anaesthetic department, and also, if possible, in adult recovery areas receiving the occasional child.

Pharmacological preparation should include a vagolytic drug, preferably atropine, probably best given intravenously at the induction to avoid embarrassing dryness of the mouth. Pain relief, preferably with morphine given slowly intravenously, should always be given if the child suffers from pain preoperatively. Ifhe does not, careful consideration should be given as to what anaesthetic technique will be used and whether spontaneous or controlled ventilation will be preferred, before choosing between morphine or a purely sedative drug or no drug at all besides atropine.