Effect of ventilation with positive end-expiratory pressure on the development of lung damage in experimental acid aspiration pneumonia in the rabbit.

Sixteen anaesthetized rabbits were subjected to tracheostomy and lung damage produced by the instillation of 4.5 ml/kg hydrochloric acid (pH 1.5) into the trachea. Half of the animals were ventilated with a positive end-expiratory pressure (PEEP) of 3 cmH2O and half with a PEEP of 10 cmH2O for 5 h, the mean airway pressure being kept at 12 cmH2O by adjustment of the end-inspiratory pause time. Pressure-volume curves were recorded every hour. Although the arterial PO2 values and compliance above the inflection point on the pressure-volume curve were greater in the group submitted to 10 cmH2O PEEP, there were no significant differences between the groups in terms of survival and histological findings.

Effects of cardiac oscillations and lung volume on acinar gas mixing during apnea.

We evaluated the importance of cardiogenic gas mixing in the acini of 13 dogs during 2 min of apnea. 133Xe (1-2 mCi in 4 ml of saline) was injected into an alveolar region through an occluded pulmonary artery branch, and washout was measured by gamma scintillation scanning during continued occlusion or with blood flow reinstated. The monoexponential rate constant for Xe washout (XeW) was -0.4 +/- 0.08 (SE) min-1 at functional residual capacity (FRC) with no blood flow in the injected region. It decreased by more than half at lung volumes 500 ml above and 392 ml below FRC. With intact pulmonary blood flow, XeW was -1.0 +/- 0.08 (SE) min-1 at FRC, and it increased with decreasing lung volume. However, if calculated Xe uptake by the blood was subtracted from the XeW measured with blood flow intact, resulting values at FRC and at FRC + 500 ml were not different from XeW with no blood flow. Reasonable calculation of Xe blood uptake at 392 ml below FRC was not possible because airway closure, increased shunt, and other factors affect XeW. After death, no significant XeW could be measured, which suggests that XeW caused by molecular diffusion was small. We conclude that 1) the effect of heart motion on the lung parenchyma increases acinar gas mixing during apnea, 2) this effect diminishes above or below FRC, and 3) there is probably no direct effect of pulmonary vascular pulsatility on acinar gas mixing.

Double-blind crossover study of the efficacy and acceptability of oxazepam Expidet tablets compared to placebo in patients undergoing gynaecological surgery.

In a double-blind crossover trial, the hypnotic efficacy and acceptability of oxazepam Expidet, a fast-dissolving tablet, was compared to placebo in patients undergoing minor gynaecological surgery. Patients received 30 mg oxazepam Expidet or placebo the night before their operation and the alternate medication the night after. A sleep questionnaire was completed the morning after both nights and acceptability was assessed the morning after the second night. Data were available for analysis on seventy-two patients aged 18-50 years. There was a significant improvement in sleep onset and quality and less awakenings after oxazepam compared to placebo (p less than or equal to 0.01). There was no significant difference in the occurrence or type of dreams, or morning-after symptoms. There was a significant preference for oxazepam compared to placebo and for the fast-dissolving Expidet form compared to conventional tablets or capsules (p less than or equal to 0.01). There were no adverse reactions in the oxazepam group. It was concluded that oxazepam Expidet was an effective and acceptable hypnotic in this group of patients.

Using helicopters for secondary transfer--does the patient benefit?

In common with many expensive, high-technology devices, helicopters have been introduced into medical practice without the systematic assessment of benefit (if any). The civilian use of helicopters has evolved from a military role in evacuating casualties and is now increasingly directed towards secondary transfer of patients between hospitals as well as primary retrieval from the community. Whilst cost restraints have delayed the development of such services in the UK they have become increasingly available in the last decade. Helicopters are fast, once airborne, have a high profile and generate considerable enthusiasm, but they carry the disadvantages of increased response time, increased time at scene, space restriction, noise, lower safety margins, weather and daylight dependence, and high cost. When considering secondary transfer, it is highly unlikely that the advantage of speed in the air outweighs these disadvantages. Although studies are limited, none has shown any advantage for helicopter against road transport in either primary or secondary transport. The money required to run a helicopter service would be far better spent on establishing properly-equipped and trained road-based retrieval teams who can stabilise the patient on site and then continue treatment in transit, particularly as it has actually been shown that this approach can be used to transfer critically-ill patients without significant deterioration.

Acute viral myocarditis. A death associated with anaesthesia.

The death of a 35-year-old woman in the immediate postoperative period as a result of undiagnosed acute viral myocarditis is described. The presentation, diagnosis and course of the disease is discussed. It is recommended that wider use to be made of routine electrocardiographs as a screening test.

Arterial to end-tidal carbon dioxide tension difference during laparoscopy. Magnitude and effect of anaesthetic technique.

The relationship between arterial carbon dioxide tension and end-tidal carbon dioxide tension was studied in 25 patients during laparoscopy. Thirteen patients received general anaesthesia and 12 epidural anaesthesia. The overall mean difference between arterial and end-tidal carbon dioxide tensions was 0.44 kPa (95% confidence intervals 0.28-0.60 kPa) which was significantly less than that reported in studies during other procedures. The reasons for this difference are probably associated with the physiological changes induced by CO2 pneumoperitoneum and steep Trendelenburg positioning. The choice of anaesthetic technique did not affect the arterial to end-tidal carbon dioxide tension difference significantly (p greater than 0.9).

Inhaled nitric oxide in acute respiratory failure in adults.

We have assessed the acute effects of inhaled nitric oxide 8, 32 and 128 volumes per million (vpm) on pulmonary haemodynamics and arterial oxygenation in patients with severe acute respiratory failure. Fourteen patients requiring artificial ventilation with mean pulmonary artery pressures greater than 30 mm Hg were given inhaled nitric oxide; haemodynamic values and blood-gas tensions were measured before and after 10 min of inhalation of nitric oxide. Nitric oxide inhaled at 8, 32 and 128 vpm decreased mean pulmonary artery pressure by 1.7 (SD 2.2), 3.2 (2.6) and 3.3 (3.3) mm Hg, pulmonary vascular resistance by 20 (64), 53 (57) and 66 (54) dyn s cm-5 and increased arterial oxygen tension by 2.5 (3.6), 3.0 (5.1) and 2.9 (3.9) kPa, respectively. All changes were significant (P < 0.05 or less) except for changes in pulmonary vascular resistance at 8 vpm. The improvement in arterial oxygenation with 128 vpm was related to pulmonary vascular resistance before commencing nitric oxide. The major beneficial effect of nitric oxide in acute respiratory failure would appear to be improvement in oxygenation rather than reduction in pulmonary artery pressure. The degree of improvement in arterial oxygenation with nitric oxide was related directly to pulmonary vascular resistance before treatment.