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Compared with the first 5 years there was a 19% increase in general anaesthetics, a 171% increase in local and (or) sedation techniques and a 9% increase in obstetric epidurals with no increase in anaesthetic staffing. In this second 5-year period, 46 patients were admitted to the Intensive Care Unit as a result of a complication of an anaesthetic technique. These patients represented 1 in 2371 anaesthetic techniques carried out in the District compared with the previous 5 years where the incidence was 1 in 1543. Seven patients died (15.2%). The complication was considered to be wholly or partially avoidable in 14 instances (30.4%). Four of these subjects died.

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Fifty-three patients were admitted in a 5-year period to the intensive care unit as a result of a complication of an anaesthetic technique. These patients represented 1 in 1543 anaesthetics carried out in the District in the period and 2.0% of all admissions to the intensive care unit. The mortality rate was 17%. The complication was considered to be wholly or partially avoidable in 14 instances (26%). Five of these subjects died and two had a residual neurological deficit.

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An expression for the splitting ratio (bypass gas/gas through vaporizing compartment) is derived formally. The factors affecting volatile agent gaseous fraction and, more importantly, partial pressure are discussed in relation to changes in temperature and barometric pressure. Low-boiling point, high saturated vapour pressure anaesthetics are more susceptible to the influence of barometric pressure variations.

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A Penlon Nuffield Series 200 Ventilator, adapted for use as a high frequency jet ventilator, was used to treat a patient with adult respiratory distress syndrome. Adequate alveolar ventilation with this method was achieved with lower mean intrapulmonary pressure (5.4 cmH2O) than with conventional intermittent positive pressure ventilation (IPPV) (6 cmH2O). An improved cardiac output was also apparent, as judged by a better systemic blood pressure [105/50 mmHg for high frequency jet ventilation (HFJV) compared to 90/40 mmHg for IPPV] and a lower central venous pressure 6 cmH2O for HFJV as compared to 9.5 cmH2O with conventional IPPV. During HFJV, the patient's need for sedatives and narcotics was reduced. This allowed an assessment to be made of any potential neurological damage caused by the cervical fracture. An assessment had not been possible during conventional ventilation due to the heavy narcotic and sedative regime required to settle the patient. This case report provides further evidence that HFJV is a useful adjunct in the management of patients requiring mechanical ventilation and also that the Penlon Nuffield Series 200 Ventilator is capable of high frequency jet ventilation.

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During cuffed intubation, damage to the trachea is least likely when the lateral wall pressure exerted by the cuff does not exceed the mean capillary perfusion pressure of the mucosa. A study was carried out of eight different types of endotracheal tubes. At the seal point the traditional red rubber tube and the armoured latex and Softway tubes exerted pressures above the mean systemic arterial pressure. Although the Portex and Mallinckrodt tubes exerted pressures close to the mean capillary perfusion pressure, much higher pressures resulted if they were overinflated. The Lanz tube, however, with its over-pressure safety balloon, maintained a lateral wall pressure below the mean capillary perfusion pressure even when inflated considerably beyond the seal point. Endotracheal cuffs are often overinflated in clinical practice. Since cuff-induced tracheal damage is most influenced by the lateral wall pressure, these results suggest that the use of Lanz-type tubes should be mandatory in intensive care units or when a cuffed tracheostomy tube is required and they should also be considered for use in more routine anaesthetic practice.

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Anxiety levels measured in patients who received preoperative reassurance about anaesthesia from a member of the hospital staff were significantly lower than those in a control group given no such support. Anxiety levels in patients who read a booklet designed to reassure about anaesthesia were less significantly reduced. Owing to the increasing work load in the operating theatre many anaesthetists can no longer afford the time to visit patients preoperatively. This study shows that either this trend should be reversed or the role of reassurer should be assumed by someone else, possibly the anaesthetic nurse. For optimal effect, the visits should be combined with use of the booklet. Unless such measures are taken, up to three million people each year may be being denied any form of reassurance before surgical treatment.

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Most difficulties with intravenous fluid charting are due to the inability to identify which bottle/bag on the balance sheet corresponds to the bottle/bag on the order sheet. These can be eliminated by allocating every bottle/bag a number in sequence and charting intravenous fluids in START and FINISH columns against a time scale. Accumulation of the Running Total minimises arithmetical errors as only two numbers are added together on any one occasion. A definitive balance form and order sheet, printed on both sides of a single sheet of A4 paper illustrates the "B Number" method with a reasonably complicated example of fluid balance.

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Gas concentrations and ventilation levels have been measured within a conventional Magill circuit when conscious volunteers breathed a non-narcotic gas mixture at varying fresh gas flows. When evidence of rebreathing of alveolar gas was detected, the fresh gas flow was kept constant until a steady state developed. All subjects showed evidence of rebreathing when the fresh gas flow approached the predicted alveolar ventilation levels. A variety of subject-circuit interactions was seen and shown to be precipitated by naturally occurring breath-to-breath variations in ventilation. A single large breath could perturb the system. This could have a temporary effect, when the fresh gas flow was sufficient to wash the increased aliquot of expired carbon dioxide from the circuit. At other times a progressive response occurred as ventilatory stimulation as a result of the increased inspired carbon dioxide concentrations caused alveolar gas to reach the reservoir bag and converted the system behaviour from that of a simple added deadspace to that of a total mixing device. Whilst marked changes occurred commonly in both ventilation and inspired gas concentrations, only slight changes in end-tidal gas concentrations occurred.

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As the physiology of deliberate hypotension has been unravelled, and as each new pharmacological agent has become available which either depresses or blocks peripheral vascular tone, depresses myocardial performance, or interferes with the conducting tissues within the myocardium, its possible incorporation into the armamentarium of the anaesthetist who offers induced hypotension has been considered. The result has been a sequence of variations in technique of characteristically recognizable vintage. No matter how the condition of induced hypotension is produced, there is usually vasodilatation, and the characteristic disturbance in physiology is of a loss of postural reactivity in the cardiovascular system. Important lessons have been learned concerning the management of shock states. Though it is difficult to evaluate the morbidity of deliberate induced hypotension, and terms such as "physiological trespass" have been used by its antagonists, it would appear that a well-considered and skilfully managed controlled hypotension is no more of a physiological trespass than anaesthesia, nor indeed than the trespass of the surgeon's knife itself.

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An evaluation of the IMI oxygen analyser is described. The accuracy was found to be adequate for clinical purposes though it was considered that this could be improved if the meter was read with greater discrimination than the existing calibrations and if the zero could be adjusted.

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