[Proceedings: The risks of anaesthesia in surgery (author's transl)]

Pure oxygen ventilation during general anaesthesia does not result in increased postoperative respiratory morbidity but decreases surgical site infection. An observational clinical study

Background. Pure oxygen ventilation during anaesthesia is debatable, as it may lead to development of atelectasis. Rationale of the study was to demonstrate the harmlessness of ventilation with pure oxygen.

Methods. This is a single-centre, one-department observational trial. Prospectively collected routine-data of 76,784 patients undergoing general, gynaecological, orthopaedic, and vascular surgery during 1995–2009 were retrospectively analysed. Postoperative hypoxia, unplanned ICU-admission, surgical site infection (SSI), postoperative nausea and vomiting (PONV), and hospital mortality were continuously recorded. During 1996 the anaesthetic ventilation for all patients was changed from 30% oxygen plus 70% nitrous oxide to 100% oxygen in low-flow mode. Therefore, in order to minimize the potential of confounding due to a variety of treatments being used, we directly compared years 1995 (30% oxygen) and 1997 (100%), whereas the period 1998 to 2009 is simply described.

Results. Comparing 1995 to 1997 pure oxygen ventilation led to a decreased incidence of postoperative hypoxic events (4.3 to 3.0%; p < 0.0001) and hospital mortality (2.1 to 1.6%; p = 0.088) as well as SSI (8.0 to 5.0%; p < 0.0001) and PONV (21.6 to 17.5%; p < 0.0001). There was no effect on unplanned ICU-admission (1.1 to 0.9; p = 0.18).

Conclusions. The observed effects may be partly due to pure oxygen ventilation, abandonment of nitrous oxide, and application of low-flow anesthesia. Pure oxygen ventilation during general anaesthesia is harmless, as long as certain standards are adhered to. It makes anaesthesia simpler and safer and may reduce clinical morbidity, such as postoperative hypoxia and surgical site infection.

[Risk score and postoperative complications in pediatric surgery]

We have developed a risk score meeting the special demands of pediatric surgery. It conveys an objective impression of the patients' preoperative condition and enables us to predict their individual intra- and postoperative behavior. This study compiles the course of 1425 operations carried out between 1986 and 1990. They were divided into low, intermediate and high risk. In addition, the patients were classified into six different age groups. We demonstrate that the number of points assigned by our risk score is highly correlated with the rate of complications that occurred, that accompanying malformations and diseases are correctly picked up and weighed by the score as far as their importance for the postoperative course is concerned, that the score is suitable for ascertaining which patients have a high probability of developing complications: the specificity is close to 100% for more than 12 points on the score, and the proportion of correctly predicted lethal courses (sensitivity) is also close to 100%. The significance of the risk score lies first in the possibility of giving patients exact data on the intra- and postoperative risk, and secondly in the provision of an objective measure of quality control--which is legally prescribed in Germany--and comparison with other hospitals. Third, the risk score gives clear starting points for research aiming at improvement in the field of surgery in sick children, and lastly it forms the basis for reliable preoperative recognition of high-risk as needed patients for modern payment methodology of the per-cose costs and thus makes it possible to charge accordingly.