Bailliere's clinical anaesthesiology最新文献

Arterial hypertension is common. It is well established that such hypertension is associated with cardiovascular complications, and that the risk of these complications can be reduced by anti-hypertensive treatment. The pathophysiology of hypertension is complex and not fully elucidated. Many physiological systems influence blood pressure, and the responses of some of these are reset. Changes have been observed both in well-known mechanisms, such as the baroreflex control of blood pressure, and in more recently described systems, such as the production of nitric oxide by the endothelium. Physical changes known as remodelling occur in the intimal and medial layers of blood vessel walls. Target organ damage may be seen in many organs, most notably the heart, the kidneys and the cerebral circulation.

It is the experience of most anaesthetists that hypertensives display cardiovascular lability and that this is less marked if the blood pressure is controlled by treatment. There is also considerable evidence for an association between hypertension and major perioperative cardiovascular complications.

Patients with hypertension should be carefully assessed prior to anaesthesia. An estimate of the severity of the hypertension should be based, if possible, on several blood pressure readings. Target organ damage should be sought. It is widely accepted that, where possible, surgery should be deferred in patients with poorly controlled or uncontrolled hypertension, and treatment given to lower the blood pressure. There is no evidence to support any particular level of blood pressure as a cut-off for treatment. We suggest that, in patients with a systolic pressure greater than 210 mmHg, a diastolic pressure greater than 115 mmHg, or target organ damage and a diastolic pressure greater than 100 mmHg, anaesthesia and surgery should be deferred if possible. In all patients on anti-hypertensive medication, this should be continued throughout the peri-operative period.

Respiratory tract injury makes a significant contribution to the morbidity and mortality of burned patients. Injury may be thermal damage to the upper airway, leading to potential airway obstruction, or damage to the lower airway from smoke inhalation, leading to increased capillary permeability. The burned patient may also develop sepsis and respiratory infection. The combination of insults also leads to respiratory failure, which is the leading cause of death in burns patients. The use of sophisticated diagnostic and management techniques does not appear to have reduced the associated mortality rate. The improved knowledge of the pathophysiology of smoke inhalation and the use of experimental therapies in animals allows a more rational approach to the management of smoke inhalation.

Pain following a burn is unpredictable, can be severe and may persist even after the burn has healed. Burn pain can be divided into the pain associated with procedures and continual background pain. Opioid analgesics and general anaesthesia are the main therapies for severe pain, but a variety of other drugs including analgesics, local anaesthetics, anti-depressants and anxiolytics also have a role. Psychological morbidity is increased when the pain is severe and a variety of methods may be used to reduce this, Reducing mortality and functional impairment is the aim of current burn management, but the relief of pain and suffering must receive equal attention.

The complete care of the thermally injured child requires the co-ordinated services of many medical and para-medical specialists. This has been referred to as the burns team, of which the anaesthetist is a vital member at all stages of treatment. The anaesthetist's skills in resuscitation, airway management, intravascular volume management, sedation and pain relief are required from the outset. The practice of early excision of the cutaneous lesion requires that the anaesthetist is familiar with the changing metabolic picture of the developing burns process. The effects of the injury and the surgical management demands modification to anaesthetic practice. The altered pharmacodynamics and pharmacokinetics are particularly relevant, as are the responses to the rapid haemodynamic and coagulation changes associated with major blood and fluid loss. If not directly responsible for the intensive care of the child, a complete knowledge of the pulmonary and cerebral changes associated with the unique injuries sustained in a house fire is essential for successful anaesthesia during surgical management.

Hospital nutrition continues to be a major problem in contemporary medicine. All too often the importance of feeding critically ill and injured patients is overlooked as emergency medical procedures take priority. Malnutrition in hospital is common but preventable. The importance of feeding the critically injured patient is discussed. A critical assessment of energy and protein requirements in burn-injured adults and children is given in the light of the many changes in treatment over the last 10 years. The mechanisms of burn-induced immunosuppression and the nutrition/infection interactions are described. The route and timing of feeding, and its importance in protecting the gut organ, are considered. Finally, there is now hope for the future in an emerging branch of nutrition. Nutritional immunomodulation of the diet of burn patients may provide the means to improve immune function and ultimately improve resistance to infection. Early enteral nutrition appropriate to the patients' requirements is the preferred method of nutrition for burns patients.

Thermal injury causes a prolonged, complex pathophysiological response which involves major changes in cardiovascular, renal and hepatic function. These changes, in addition to alterations in plasma protein concentrations, are responsible for significant changes in the disposition and action of many drugs in patients. Changes in drug absorption, plasma protein binding, hepatic blood flow and drug biotransformation, and renal blood flow, drug filtration and secretion have been demonstrated for many classes of drugs in burned patients. These pharmacokinetic factors often mean that standard therapeutic regimens may be inappropriate for such patients. In addition, burn injury may also cause a disruption of the functioning of drug receptors, causing altered pharmacological responses to plasma drug concentrations that are usually effective in non-burned patients. Such pharmacokinetic and pharmacodynamic changes have been observed in several classes of drugs used commonly in anaesthetic practice, these classes including the muscle relaxants, opioid analgesics, aminoglycoside antibiotics, benzodiazepines, exogenous catecholamines and H₂-receptor antagonists. Careful attention to the use of these agents in burned patients is required, with close monitoring of drug effect being particularly important.

The systemic sequelae of burn injury preclude isolated treatment of the burn wound. A multidisciplinary approach is essential for optimal burn patient care. Early surgical debridement and closure of the burn wound can reduce mortality and improve outcome. The patient's age, co-morbid state, burn type and site make each injury unique, requiring a judicious application of all therapeutic options. The ultimate aim of surgical intervention is not only to reduce mortality but also morbidity by improving the functional and aesthetic outcome of burn wound healing. The aetiology and nature of the burn wound are described and the common treatment modalities discussed.

Burns are a common accidental, and occasionally non-accidental injury. They may be devastating both in terms of morbidity and mortality and often produce life-long disfigurement and functional disability in survivors. Any doctor who comes into contact with burn victims must have a good working knowledge of emergency management of thermal injury and all anaesthetists must know the basics of airway management and resuscitation of such patients.

Appropriate pre-hospital assessment and initial treatment at the scene of accident may be life-saving. Following removal of the casualty to a place of safety, the focus will be upon respiratory system management and the restoration of circulation. Steps should be taken to keep burns clean and to make the patient as comfortable as possible. On arrival at hospital a thorough reassessment should take place. Management of the respiratory system may be complicated by associated trauma or smoke inhalation. Initial fluid requirements can only be gauged once an assessment of the nature and extent of the burn injury has been undertaken.

Fluid resuscitation of burn victims has been, and continues to be, the subject of much research. In the UK most fluid resuscitation regimens are colloid based, but crystalloid protocols using lactated Ringer's solution are much more common on a world-wide basis. The monitoring of resuscitation is also the subject of continued research, in particular regarding the use of indwelling central venous catheters.

Whilst aggressive resuscitation undoubtedly saves lives the mortality associated with severe burns remains depressingly high. In future immunotherapy may offer the opportunity to modulate the whole body response to thermal injury but it is still too early to establish what impact this will have on burn mortality.