Bailliere's clinical anaesthesiology最新文献

The fluid replacement chosen for surgical applications and shock resuscitation continues to be debated. Historically, the controversy is centred on the use of colloid versus electrolyte solutions. Studies of electrolyte solutions in resuscitation often utilize a model of haemorrhagic shock, while colloid solution study models generally involve septic or ischaemic shock, with corresponding loss of plasma proteins.

Survival variables and resuscitation criteria are main factors in evaluating infusion agents in clinical practice. The colloid dose-volume-concentration relationship is crucial in extrapolating experimental studies to clinical applications, as failure to consider any variable may result in mortality.

Principles of albumin dosing, volume and concentration are related to survival variables in experimental plasma loss types of shock. The derivations of these principles have been tested clinically using renal transplantation as a unique single organ clinical shock model, evaluating the importance of colloid administration in early optimization of organ function and graft survival.

Since the first descriptions of the use of 7.5% hypertonic saline for resuscitation of haemorrhage in 1980, there has been substantial animal research and clinical evaluation of small volume resuscitation. Most interest has focused on combined hyperosmotic and hyperoncotic colloid formulations. Infused hyperosmotic NaCl rapidly expands plasma volume, while the hyperoncotic colloid sustains the volume expansion. Other contributing factors to the efficacy of these solutions are increased cardiac effectiveness and peripheral vasodilation. The most often studied solution, 7.5% NaCl/6% dextran 70, offers promise to reduce the mortality of traumatic hypotension and head injury when used as an initial treatment. Future hyperosmotic-hyperoncotic formulations with different solutes may provide specific beneficial pharmacological properties in addition to the established cardiovascular effects of hyperosmolarity. A particularly promising formulation might be a combination solution of an oxygen carrier colloid, for example, haemoglobin, and a hyperosmotic crystalloid.

Maintenance/achievement of normovolaemia, haemodynamic stability and adequate nutritive blood flow is the main objective of clinical fluid treatment. These goals are more effectively reached with the choice of artificial colloids rather than balanced salt solutions for plasma volume support. Commonly used artificial colloids are dextrans, gelatins and different hydroxyethyl starch (HES) preparations, including pentastarch and pentafractions of HES. With the choice of colloid, the plasma volume expanding efficacy, intravascular persistence, haemorheologic effectiveness and inherent specific pharmacological effects on haemostasis, red cell aggregation, platelet function, plasma viscosity and blood corpuscle-endothelial cell interactions of the colloid should be considered. In this chapter, colloid characteristics are related to the clinical efficacy of different colloidal preparations for intentional haemodilution and plasma volume support in patients with vascular disease or acute ischaemic stroke. Furthermore, the choice of colloid for perioperative fluid therapy and resuscitation of shock and trauma conditions is considered.

Regional anaesthetic techniques and the agents used for their administration have come a long way since 1986. It is now possible to perform a regional block for every surgical procedure in the paediatric repertoire and, if necessary, keep it running well into the post-operative period. We should be aware of the pitfalls of the various techniques from the audits of Dalens and Chrysostome (1991), Wilson and Lloyd-Thomas (1993), Wood et al (1994), Flandin-Bety and Barrier (1995) and Stafford et al (1995). Experts such as Berde, Eyres and Murat have shared the experience of their practice in Boston, Melbourne and Paris with us, and individual colleagues have alerted us to the unexpected problems which have arisen in their daily practice. There will still be reports of the unexpected and bizarre in years to come. Compared to adult practice, paediatric regional anaesthesia is still in its infancy and dependent on studies performed on small groups of children.

It is no disgrace to accept that regional techniques are more difficult to perform in children, and there is nothing to be gained by opting for the most difficult when a safer, adequate technique will suffice.

Safe and effective anaesthetic management of the infant or child who suffers from a chronic respiratory system disorder requires that the anaesthesiologist understand: (1) the pathophysiology of the disorder; (2) the metabolism and pulmonary development associated with the child's age; (3) the child's general medical history; (4) the history and current status of the child's respiratory disorder; and (5) the potential interaction of the respiratory disorder itself and current drug therapy with anaesthetic agents, adjuvant drugs and techniques to be considered for the perioperative care of the child. A detailed history of the child's respiratory disorder as well as prior experience with anaesthesia and operations, combined with direct personal consultation with the child's primary care physician and pulmonary specialist, will help the anaesthesiologist minimize the hazards associated with anaesthesia in these children. Finally, the anaesthesiologist needs to be especially cautious in predicting for the surgeon and the family the duration and the levels of support needed for recovery following operation and anaesthesia. The anaesthesiologist should consider warning the family and the surgeon that recovery may be slower and more complex than in completely healthy children, and may call for special therapy for a time following anaesthesia.

Post-operative vomiting still occurs at an unacceptably high rate in paediatric anaesthesia. Determinants of its incidence are a history of post-operative emesis and the surgical site (e.g. strabismus surgery, ENT procedures, orchidopexy). The choice of pre-medication and anaesthetic technique may also affect the risk of PONV, as may the use of opioids, gastric inflation by mask ventilation and the duration of surgery. To avoid, decrease the risk of, or alleviate the severity of PONV, it is important to realize that this is a multifactorial problem. Careful history-taking and the provision of well-balanced information for child and parents at the pre-operative visit are invaluable. Pre-medication and anaesthetic technique should be chosen with a view to minimizing the risk of PONV, for example, by using a non-opioid pre-medication, regional blocks whenever possible, and non-opioid analgesics both at the end of surgery and post-operatively. The anaesthetist should consider administering anti-emetics at an early stage, and also routinely prescribe appropriate anti-emetics for use in the post-operative period. Anti-emetics should be administered at any sign of post-operative nausea. If opioids are required post-operatively, anti-emetics could be administered at the same time. Post-operative pain is preferably controlled with non-opioid analgesics if possible. The post-operative period should be calm and without unnecessary disturbance of the child. Transport of the child should be performed carefully. Oral fluids should be suspended until asked for by the child.

Paediatric anaesthetists desire and feel at ease with parental presence at induction of anaesthesia. Our own experiences, after more than 25 000 cases of parental presence during induction, are excellent (Bezstarosti-van Eeden et al, 1993). For those anaesthetists who do not regularly work in a paediatric environment, however, it may still be a controversial issue. Preschool children benefit most from the presence of a well-informed and prepared parent or legal guardian.

When anaesthetizing a child one is anaesthetizing the entire family! It is important to provide detailed information regarding how you as the anaesthesiologist will provide the safest possible care for their child. Alleviating parental anxiety will alleviate patient anxiety.

During the pre-operative visit, the anaesthesiologist performs the physical examination while assessing abnormalities of the airway and the patient's level of anxiety and response to strangers. The anaesthesiologist determines the need for a pre-anaesthetic medication and whether the child might benefit from parents accompanying them to the operating room. Further preparation includes haematological evaluation for children less than 6 months of age; anaemic former preterms are particularly susceptible to apnoea. Underlying medical problems require appropriate evaluation. Review of past anaesthetic records helps determine difficulties with previous laryngoscopies as well as adequacy or inadequacy of previous pre-medication.

It is important to describe to the child that the sleep caused by anaesthesia is different than sleep at home. The sleep induced by anaesthesia is such that the child will not feel anything, will not remember anything, will not awaken during the operation but, when the anaesthetic gases are removed, they will awaken and return to their parents. Discussion regarding post-operative pain relief will comfort the child and family.