Calculation of volatile anaesthetics consumption from agent concentration and fresh gas flow.

BACKGROUND: The assessment of volatile agents' consumption can be performed by weighing vapourisers before and after use. This method is technically demanding and unavailable for retrospective analysis of anaesthesia records. Therefore, a method based on calculations from fresh gas flow and agent concentration is presented here. METHODS: The presented calculation method herein enables a precise estimation of volatile agent consumption when average fresh gas flows and volatile agent concentrations are known. A pre-condition for these calculations is the knowledge of the vapour amount deriving from 1 ml fluid volatile agent. The necessary formulas for these calculations and an example for a sevoflurane anaesthesia are presented. RESULTS: The amount of volatile agent vapour deriving from 1 ml of fluid agent are for halothane 229 ml, isoflurane 195 ml, sevoflurane 184 m, and desflurane 210 ml. The constant for sevoflurane is used in a fictitious clinical case to exemplify the calculation of its consumption in daily routine resulting in a total expenditure of 23.6 ml liquid agent. CONCLUSIONS: By application of the presented specific volatile agent constants and equations, it becomes easy to calculate volatile agent consumption if the fresh gas flows and the resulting inhaled concentration of the volatile agent are known. By this method, it is possible to extract data about volatile agent consumption both ways: (1) retrospectively from sufficiently detailed and accurate anaesthesia recordings, as well as (2) by application of this method in a prospective setting. Therefore, this method is a valuable contribution to perform pharmacoeconomical surveys.

Interrelation of peri-operative morbidity and ASA class assignment in patients undergoing gynaecological surgery.

OBJECTIVE: The aim of this study was to estimate intra- and post-operative risk using the American Society of Anaesthesiologists (ASA) classification which is an important predictor of an intervention and of the entire operating programme. STUDY DESIGN: In this retrospective study, 4435 consecutive patients undergoing elective and emergency surgery at the Gynaecological Clinic of the University Hospital of Zurich were included. The ASA classification for pre-operative risk assessment was determined by an anaesthesiologist after a thorough physical examination. We observed several pre-, intra- and post-operative parameters, such as age, body-mass-index, duration of anaesthesia, duration of surgery, blood loss, duration of post-operative stay, complicated post-operative course, morbidity and mortality. The investigation of different risk factors was achieved by a multiple linear regression model for log-transformed duration of hospitalisation. RESULTS: Age and obesity were responsible for a higher ASA classification. ASA grade correlates with the duration of anaesthesia and the duration of the surgery itself. There was a significant difference in blood loss between ASA grades I (113+/-195 ml) and III (222+/-470 ml) and between classes II (176+/-432 ml) and III. The duration of post-operative hospitalisation could also be correlated with ASA class. ASA class I=1.7+/-3.0 days, ASA class II=3.6+/-4.3 days, ASA class III=6.8+/-8.2 days, and ASA class IV=6.2+/-3.9 days. The mean post-operative in-hospital stay was 2.5+/-4.0 days without complications, and 8.7+/-6.7 days with post-operative complications. Multiple linear regression model showed that not only the ASA classification contained an important information for the duration of hospitalisation. Parameters such as age, class of diagnosis, post-operative complications, etc. also have an influence on the duration of hospitalisation. CONCLUSION: This study shows that the ASA classification can be used as a good and early available predictor for the planning of an intervention in gynaecological surgery. The ASA classification helps the surgeon to assess the peri-operative risk profile of which important information can be derived for the planning of the operation programme.

Impact of the reduction of anaesthesia turnover time on operating room efficiency.

BACKGROUND AND OBJECTIVE: We investigated whether an increase in anaesthesia staffing to permit induction of anaesthesia before the previous case had ended ('overlapping') would increase overall efficiency in the operating room. Hitherto, the average duration of operating sessions was too long, thus impeding the timely commencement of physicians' ward duties. METHODS: The investigation was designed as a prospective, non-randomized, interrupted time-series analysis divided into three phases: (a) a baseline of 3.5 months, (b) a 2.5 month intervention phase, in which anaesthesia staffing was increased by one attending physician and one nurse, and (c) a further 2 months under baseline conditions. Data focussed on process management were collected from operating room staff, anaesthesia personnel and surgeons using a structured questionnaire collected daily during the entire study. RESULTS: Turnover time between consecutive operations decreased from 65 to 52 min per operation (95% CI: 9; 17; P = 0.0001). Operating room occupancy increased from 4:28 to 5:27 h day-1 (95% CI: 50; 68; P = 0.005). The surgeons began their work on the ward 35 min (95% CI: 30; 40) later than before the intervention and their overtime increased from 22:36 to 139:50 h. CONCLUSIONS: The time between surgical operations decreased significantly. Increased operating room efficiency owing to overlapping induction of anaesthesia allows more intense scheduling of operations. Thus, physicians and nurses can be released to spend more time with their patients in the ward. Improving the efficiency of the operating room alone is insufficient to improve human resource management at all levels of a surgical clinic.

[Intravenous anesthesia with propofol versus thiopental-/enflurane anesthesia. A consumption and cost analysis]. / Intravenöse Anästhesie mit Propofol versus Thiopental-/Enflurananästhesie. Eine Verbrauchs- und Kostenanalyse.

It may be possible to reduce costs in anaesthesia when there is a choice of drugs and methods. Two of the most widespread techniques are inhalation anaesthesia with enflurane following induction with thiopentone, and intravenous anaesthesia (IVA) with propofol. The aims of our study were to compare the costs, effectiveness and side effects of the anaesthetics involved in these two techniques, and to measure significant clinical parameters. METHODS. After approval by the hospital ethics committee, 40 adult patients of ASA physical status 1 and 2 who had been scheduled for elective septorhinoplasty and had given informed consent were entered in our prospective, single-blind randomized study. In 20 patients anaesthesia was induced with thiopentone (4-5 mg/kg) and suxamethonium (1-1.5 mg/kg) and maintained with enflurane. The other 20 patients received an initial i.v. bolus of propofol (2-2.5 mg/kg) followed by a propofol infusion adjusted to their individual clinical needs. Ventilation was performed in both groups with 70% nitrous oxide in oxygen, using a nonrebreathing system. Muscle relaxation was maintained with atracurium. The amounts of anaesthetics, oxygen, nitrous oxide, and muscle relaxants used were measured and a record of the costs was kept. In addition, circulatory and respiratory parameters and quantitative and qualitative aspects of recovery from anaesthesia were recorded. RESULTS. The biometric and clinical data did not differ significantly between the two groups. For induction, 382 (+/- 55.9) mg thiopentone costing 1.24 Swiss francs (SFr), or 172 (+/- 25.1) mg propofol costing 11.87 (SFr) was used. For maintenance, 28.3 (+/- 6.4) ml enflurane costing 21.96 SFr/h, or 450.7 (+/- 247) mg propofol costing 29.75 SFr/h was required. The need for muscle relaxants, oxygen, and nitrous oxide was also not significantly different in the two groups. Additional expenses were due to relaxation antagonists (1.91 SFr per patient in both groups) and to the perfusion pump system (8.60 SFr per patient in the IVA group only). Circulatory and respiratory parameters remained normal in both groups. In the propofol group, the heart rate tended to increase more at the beginning of anaesthesia, whereas later on it showed a tendency to lower values than in the thiopentone/enflurane group. Patients receiving IVA generally had a shorter awakening period, a higher degree of wellbeing during recovery, and needed less systemic analgesics (P < 0.05). CONCLUSIONS. Costs of anaesthetic drugs in the IV group totalled 54.50 SFr during the first hour, i.e. 1.65 times the costs in the thiopentone/enflurane group for the same time. However, with continuing duration of anaesthesia this ratio declines to 1.43 in anaesthesia lasting 2 h. In addition, IVA patients had a noticeably faster and far more pleasant recovery. Minute ventilation, oxygen consumption, heart rate and CO2 production indicated a less pronounced stress response and sympathetic activity during and after propofol. Quicker recovery of cognitive and psychomotor abilities, less postoperative pain and less impairment of respiratory function after IVA may lead to an earlier release from the postoperative recovery unit. This might be a cost-reducing factor that should be taken into account when these two anaesthetic regimens are concerned.

[Anesthetic gas consumption and costs in a closed system with the PhysioFlex anesthesia equipment]. / Anästhesiegasverbrauch und -kosten im geschlossenen System mit dem PhysioFlex-Narkosegerät.

A marked decrease in both personal and environmental pollution with anaesthetic gases as well as in costs is possible with anaesthesia machines which can be run with a low fresh gas flow (FGF) [9]. Low-flow anaesthesia can be performed with appropriately equipped circle systems, although strongly reduced FGF minimises the control of depth of anaesthesia and gas concentrations. Microprocessor-controlled feedback systems allow the utilisation of closed-circuit systems throughout the whole duration of anaesthesia, maintaining full anaesthetic control [3,5]. The aim of this investigation was to determine the costs resulting from gas consumption and clinical suitability of the recently marketed PhysioFlex anaesthesia machine. METHODS. We used a PhysioFlex (Physio, Hoofdorpp, Netherlands) in a series of 15 routine otorhinolaryngological interventions. After induction with thiopentone and suxamethonium, general anaesthesia was maintained with nitrous oxide in 30% oxygen and isoflurane and supplemented with fentanyl and atracurium. The expenditure of anaesthetic gases was recorded during a total of 61 h and 27 min and differentiated into its components. Anaesthetic gas uptake and costs were compared with different breathing systems (low-flow anaesthesia, semiclosed system and non-rebreathing system) under similar clinical conditions. RESULTS. The average minute volume was 6.84 (+/- 1.17) l and the expiratory isoflurane concentration was 0.91% (+/- 0.14%) (Table 1). These settings resulted in an oxygen expenditure of 27.9 (+/- 8.46) l/h with total costs of SFr. 0.04, nitrous oxide 11.9 (+/- 5.4) l/h and 0.27, isoflurane 3.9 ml/h and SFr. 5.42. In contrast, other breathing systems in analogous settings resulted in greater costs by a factor of 0.77 for low-flow anaesthesia (FGF 1 l/min), 2.47 for a semiclosed system (FGF 3 l/min) and 5.63 for a valve-controlled non-rebreathing system (FGF 6.84 l/min) (Table 2). DISCUSSION. The emission of anaesthetic gases can be lowered by measures that avoid unintended gas fallout, the application of filters, scavenging systems and efficient air circulation in operation and recovery rooms [8]. Above all, the use of the lowest possible FGF is advantageous for the patient insofar as better conditioned breathing gases are available, and economic and environmental effects are more significant (Table 3). With the method of quantitative anaesthesia as performed by the PhysioFlex, it is now possible to reduce gas expenditure according to the requirements of the patient as well as maintaining full control of anaesthesia depth. Simultaneously, multiple secured feedback control systems guarantee adequate monitoring and storage of respiratory and metabolic parameters. The duration of nitrous oxide wash-out can be a problem, in particular, when a changeover to O2/air is required.

A survey of patients' attitudes to their dentist.

A survey of the dentist-patient relationship, carried out in several Melbourne suburbs, found that the incidence of dentures increases with age; that females visit the dentist more regularly and are more likely to wear partial dentures than males; that the young visit more regularly than the old; and that the wearing of dentures and the expense of treatment are significant factors which deter people from visiting the dentist more regularly. It was found that "fear" and "dislike" of the dentist, "low" confidence in the dentist and a poor dentist attitude to the patient are all associated with poor attendance. "Dislike" is a stronger deterrent than "fear", although "fear" is more common. Confidence in the dentist is high, most have a high opinion of their own dentist, and only a fifth of the respondents consider their dentist to be "rude" or "indifferent". Attitude associations are also discussed.