Martin Bellgardt

Survival after long-term isoflurane sedation as opposed to intravenous sedation in critically ill surgical patients: Retrospective analysis.

BACKGROUND Isoflurane has shown better control of intensive care sedation than propofol or midazolam and seems to be a useful alternative. However, its effect on survival remains unclear. OBJECTIVE The objective of this study is to compare mortality after sedation with either isoflurane or propofol/midazolam. DESIGN A retrospective analysis of data in a hospital database for a cohort of consecutive patients. SETTING Sixteen-bed interdisciplinary surgical ICU of a German university hospital. PATIENTS Consecutive cohort of 369 critically ill surgical patients defined within the database of the hospital information system. All patients were continuously ventilated and sedated for more than 96 h between 1 January 2005 and 31 December 2010. After excluding 169 patients (93 >79 years old, 10 <40 years old, 46 mixed sedation, 20 lost to follow-up), 200 patients were studied, 72 after isoflurane and 128 after propofol/midazolam. INTERVENTIONS Sedation with isoflurane using the AnaConDa system compared with intravenous sedation with propofol or midazolam. MAIN OUTCOME MEASURES Hospital mortality (primary) and 365-day mortality (secondary) were compared with the Kaplan–Meier analysis and a log-rank test. Adjusted odds ratios (ORs) [with 95% confidence interval (95% CI)] were calculated by logistic regression analyses to determine the risk of death after isoflurane sedation. RESULTS After sedation with isoflurane, the in-hospital mortality and 365-day mortality were significantly lower than after propofol/midazolam sedation: 40 versus 63% (P = 0.005) and 50 versus 70% (P = 0.013), respectively. After adjustment for potential confounders (coronary heart disease, chronic obstructive pulmonary disease, acute renal failure, creatinine, age and Simplified Acute Physiology Score II), patients after isoflurane were at a lower risk of death during their hospital stay (OR 0.35; 95% CI 0.18 to 0.68, P = 0.002) and within the first 365 days (OR 0.41; 95% CI 0.21 to 0.81, P = 0.010). CONCLUSION Compared with propofol/midazolam sedation, long-term sedation with isoflurane seems to be well tolerated in this group of critically ill patients after surgery.

Technical Performance and Reflection Capacity of the Anaesthetic Conserving Device—A Bench Study with Isoflurane and Sevoflurane

ObjectiveThe anaesthetic conserving device (AnaConDa®, Sedana Medical, Sundbyberg, Sweden) facilitates administration of isoflurane or sevoflurane by liquid infusion. An anaesthetic reflector inside the device conserves exhaled anaesthetic and re-supplies it during inspiration. In this bench study, we examined the influence of infusion rates and ventilatory settings on the resulting anaesthetic concentrations on patient (Cpat) and ventilator side of the reflector (Closs) to describe its technical performance.MethodsA Puritan Bennett 840 ICU ventilator (Pleasanton, US), AnaConDa®, and a test lung (3 l-chloroprene-bag) were assembled. Infusion rates (IR, 0.2-50 ml h-), respiratory rates (RR, 5-40 breaths min-1), and tidal volumes (VT, 0.3, 0.5, and 1.0 l) were varied. Cpat was measured via a thin catheter in the middle of the 3 l-bag in steady state (online data storage and averaging over >10 min). Closs was calculated from IR (to yield the volume of vapour per unit of time), and expired minute volume (in which the vapour is diluted) on the assumption that, in the steady state, input by liquid infusion equals output through the reflector.ResultsAt lower concentrations (Cpat< 1 vol%) the ratio Closs/Cpat was constant (RC = 0.096 ±±0.012) for all combinations of IR, RR and VT, both for isoflurane and sevoflurane. The device could efficiently reflect up to 10 ml vapour per breath (e.g. 2 vol% in 0.5 l). When exceeding this capacity, surplus vapour “spilled over” and RC markedly increased indicating decreased performance.ConclusionsThe triple product minute volume times RC times Cpat describes anaesthetic losses through the reflector. It can easily be calculated as long as the 10 ml reflection capacity is not exceeded and thus RC is constant. Increased minute ventilation necessitates increasing the IR to keep Cpat constant. When using large VT and high Cpat “spill over” occurs. This effect offers some protection against an inadvertent overdose.

A novel device for target controlled administration and reflection of desflurane – the Mirus™

The Anaconda™ system is used to deliver inhalational sedation in the intensive care unit in mainland Europe. The new Mirus™ system also uses a reflector like the Anaconda; however, it also identifies end‐tidal concentrations from the gas flow, injects anaesthetics during early inspiration, controls anaesthetic concentrations automatically, and can be used with desflurane, which is not possible using the Anaconda. We tested the Mirus with desflurane in the laboratory. Compared with an external gas monitor, the bias (two standard deviations) of the end‐tidal concentration was 0.11 (0.29)% volume. In addition, automatic control was reasonable and maximum concentration delivered was 10.2%, which was deemed to be sufficient for clinical use. Efficiency was > 80% and was also deemed to be acceptable, but only when delivering a low concentration of desflurane (≤ 1.8%). By modifying the reflector, we improved efficiency up to a concentration of 3.6%. The Mirus appears to be a promising new device for long‐term sedation with desflurane on the intensive care unit, but efficiency must be improved before routine clinical use becomes affordable.

Inhaled anesthetic agent sedation in the ICU and trace gas concentrations: a review

There is a growing interest in the use of volatile anesthetics for inhalational sedation of adult critically ill patients in the ICU. Its safety and efficacy has been demonstrated in various studies and technical equipment such as the anaesthetic conserving device (AnaConDa™; Sedana Medical, Uppsala, Sweden) or the MIRUS™ system (Pall Medical, Dreieich, Germany) have significantly simplified the application of volatile anesthetics in the ICU. However, the personnel’s exposure to waste anesthetic gas during daily work is possibly disadvantageous, because there is still uncertainty about potential health risks. The fact that average threshold limit concentrations for isoflurane, sevoflurane and desflurane either differ significantly between countries or are not even defined at all, leads to raising concerns among ICU staff. In this review, benefits, risks, and technical aspects of inhalational sedation in the ICU are discussed. Further, the potential health effects of occupational long-term low-concentration agent exposure, the staffs’ exposure levels in clinical practice, and strategies to minimize the individual gas exposure are reviewed.

Mortality and recovery after inhalational compared to intravenous ICU sedation: A-809

There is a small rise in bilirubin and small fall in albumin post hepatic resection. ALT levels peak day 1 post resection and return to normal by day 9. ALP levels fall immediately post resection and then progressively rise. Conclusion: Hepatic resection results in a distinctive pattern of changes in liver function tests. References: 1 Stewart GD, et al. The extent of resection influences outcome following hepatectomy for colorectal liver metastases. Eur J Surg Oncol. 2004 May; 30(4): 370–6. 2 Rees, et al. One hundred and fifty hepatic resections. BJS 1995; 83:1526–9.

Environmental safety: Air pollution while using MIRUS™ for short-term sedation in the ICU

MIRUS™ is a device for target‐controlled inhalational sedation in the ICU in combination with use of isoflurane, or sevoflurane, or desflurane. The feasibility of this device has recently been proven; however, ICU staff exposure may restrict its application. We investigated ICU ambient room pollution during daily work to estimate ICU personnel exposure while using MIRUS™.

The child's behavior during inhalational induction and its impact on the anesthesiologist's sevoflurane exposure

Sevoflurane is commonly used for inhalational inductions in children, but the personnels exposure to it is potentially harmful. Guidance to reduce gas pollution refers mainly to technical aspects, but the impact of the childs behavior has not yet been studied.