Mats Enlund

Optimal oxygen concentration during induction of general anesthesia.

Background The use of 100% oxygen during induction of anesthesia may produce atelectasis. The authors investigated how different oxygen concentrations affect the formation of atelectasis and the fall in arterial oxygen saturation during apnea. Methods Thirty-six healthy, nonsmoking women were randomized to breathe 100, 80, or 60% oxygen for 5 min during the induction of general anesthesia. Ventilation was then withheld until the oxygen saturation, assessed by pulse oximetry, decreased to 90%. Atelectasis formation was studied with computed tomography. Results Atelectasis in a transverse scan near the diaphragm after induction of anesthesia and apnea was 9.8 ± 5.2 cm2 (5.6 ± 3.4% of the total lung area; mean ± SD), 1.3 ± 1.2 cm2 (0.6 ± 0.7%), and 0.3 ± 0.3 cm2 (0.2 ± 0.2%) in the groups breathing 100, 80, and 60% oxygen, respectively (P < 0.01). The corresponding times to reach 90% oxygen saturation were 411 ± 84, 303 ± 59, and 213 ± 69 s, respectively (P < 0.01). Conclusion During routine induction of general anesthesia, 80% oxygen for oxygenation caused minimal atelectasis, but the time margin before unacceptable desaturation occurred was significantly shortened compared with 100% oxygen.

Cerebral normoxia in the rhesus monkey during isoflurane-or propofol-induced hypotension and hypocapnia, despite disparate blood-flow patterns a positron emission tomography study

Background: Due to a few reports of cerebral dysfunction in connection with isoflurane‐induced hypotension and concomitant hypocapnia, positron emission tomography (PET) was used to measure cerebral oxygenation and blood flow during similar conditions with isoflurane or propofol.

Oxygen concentration and characteristics of progressive atelectasis formation during anaesthesia.

Background: Atelectasis is a common consequence of pre‐oxygenation with 100% oxygen during induction of anaesthesia. Lowering the oxygen level during pre‐oxygenation reduces atelectasis. Whether this effect is maintained during anaesthesia is unknown.

The sevoflurane saving capacity of a new anaesthetic agent conserving device compared with a low flow circle system

Background: An anaesthetic agent conserving device (ACD) has been added to a Bain system to approach the agent‐saving capacity of a low flow circle system.

A new device to reduce the consumption of a halogenated anaesthetic agent*. apparatus

We report the first clinical application of a new anaesthetic agent‐saving device. The principles of a heat–moisture exchanger have been further developed to create a device that reduces inhalational agent consumption. Sixteen patients were randomly allocated to receive isoflurane through either a vaporiser or through the agent‐saving device. A coaxial Mapleson D system (Bain) was used in both groups. A standard ventilatory setting was used, aiming for normocapnia. Mean (SD) isoflurane consumption was 24.5 (2.8) ml.MAC‐hour−1 with the vaporiser, compared with 15.2 (3.0) ml.MAC‐hour−1 with the new device (p < 0.05). This corresponded to a 40% saving in the consumption of isoflurane. The amount of isoflurane that was scavenged to the atmosphere was reduced by an average of 55%.

Physician-led team triage based on lean principles may be superior for efficiency and quality? A comparison of three emergency departments with different triage models

BackgroundThe management of emergency departments (EDs) principally involves maintaining effective patient flow and care. Different triage models are used today to achieve these two goals. The aim of this study was to compare the performance of different triage models used in three Swedish EDs. Using efficiency and quality indicators, we compared the following triage models: physician-led team triage, nurse first/emergency physician second, and nurse first/junior physician second.MethodsAll data of patients arriving at the three EDs between 08:00- and 21:00 throughout 2008 were collected and merged into a database. The following efficiency indicators were measured: length of stay (LOS) including time to physician, time from physician to discharge, and 4-hour turnover rate. The following quality indicators were measured: rate of patients left before treatment was completed, unscheduled return within 24 and 72 hours, and mortality rate within 7 and 30 days.ResultsData from 147,579 patients were analysed. The median length of stay was 158 minutes for physician-led team triage, compared with 243 and 197 minutes for nurse/emergency physician and nurse/junior physician triage, respectively (p < 0.001). The rate of patients left before treatment was completed was 3.1% for physician-led team triage, 5.3% for nurse/emergency physician, and 9.6% for nurse/junior physician triage (p < 0.001). Further, the rates of unscheduled return within 24 hours were significantly lower for physician-led team triage, 1.0%, compared with 2.1%, and 2.5% for nurse/emergency physician, and nurse/junior physician, respectively (p < 0.001). The mortality rate within 7 days was 0.8% for physician-led team triage and 1.0% for the two other triage models (p < 0.001).ConclusionsPhysician-led team triage seemed advantageous, both expressed as efficiency and quality indicators, compared with the two other models.

The choice of anaesthetic—sevoflurane or propofol—and outcome from cancer surgery: A retrospective analysis

Abstract Background. Commonly used inhalational hypnotics, such as sevoflurane, are pro-inflammatory, whereas the intravenously administered hypnotic agent propofol is anti-inflammatory and anti-oxidative. A few clinical studies have indicated similar effects in patients. We examined the possible association between patient survival after radical cancer surgery and the use of sevoflurane or propofol anaesthesia. Patients and methods. Demographic, anaesthetic, and surgical data from 2,838 patients registered for surgery for breast, colon, or rectal cancers were included in a database. This was record-linked to regional clinical quality registers. Cumulative 1- and 5-year overall survival rates were assessed using the Kaplan–Meier method, and estimates were compared between patients given propofol (n = 903) or sevoflurane (n = 1,935). In a second step, Cox proportional hazard models were calculated to assess the risk of death adjusted for potential effect modifiers and confounders. Results. Differences in overall 1- and 5-year survival rates for all three sites combined were 4.7% (p = 0.004) and 5.6% (p < 0.001), respectively, in favour of propofol. The 1-year survival for patients operated for colon cancer was almost 10% higher after propofol anaesthesia. However, after adjustment for several confounders, the observed differences were not statistically significant. Conclusion. Propofol anaesthesia might be better in surgery for some cancer types, but the retrospective design of this study, with uneven distributions of several confounders, distorted the picture. These uncertainties emphasize the need for a randomized controlled trial.

Combined analysis of circulating β-endorphin with gene polymorphisms in OPRM1, CACNAD2 and ABCB1 reveals correlation with pain, opioid sensitivity and opioid-related side effects

BackgroundOpioids are associated with wide inter-individual variability in the analgesic response and a narrow therapeutic index. This may be partly explained by the presence of single nucleotide polymorphisms (SNPs) in genes encoding molecular entities involved in opioid metabolism and receptor activation. This paper describes the investigation of SNPs in three genes that have a functional impact on the opioid response: OPRM1, which codes for the μ-opioid receptor; ABCB1 for the ATP-binding cassette B1 transporter enzyme; and the calcium channel complex subunit CACNA2D2. The genotyping was combined with an analysis of plasma levels of the opioid peptide β-endorphin in 80 well-defined patients with chronic low back pain scheduled for spinal fusion surgery, and with differential sensitivity to the opioid analgesic remifentanil. This patient group was compared with 56 healthy controls.ResultsThe plasma β-endorphin levels were significantly higher in controls than in pain patients.A higher incidence of opioid-related side effects and sex differences was found in patients with the minor allele of the ABCB1 gene. Further, a correlation between increased opioid sensitivity and the major CACNA2D2 allele was confirmed. A tendency of a relationship between opioid sensitivity and the minor allele of OPRM1 was also found.ConclusionsAlthough the sample cohort in this study was limited to 80 patients it appears that it was possible to observe significant correlations between polymorphism in relevant genes and various items related to pain sensitivity and opioid response. Of particular interest is the new finding of a correlation between increased opioid sensitivity and the major CACNA2D2 allele. These observations may open for improved strategies in the clinical treatment of chronic pain with opioids.

TCI : Target Controlled Infusion, or Totally Confused Infusion? Call for an Optimised Population Based Pharmacokinetic Model for Propofol.

Different pharmacokinetic models for target controlled infusion (TCI) of propofol are available in the recently launched open TCI systems. There is also a compelling choice to work with either plasma- or effect-site targets. Knowledge about the clinical consequences of different alternatives is of importance. We aimed to illustrate the potential differences in the actual drug delivery/output between three present commercially available and clinically used pharmacokinetic models: the original Marsh model, which is also implemented in the Diprifusor®, the “modified Marsh-” and the Schnider models. Simulations were made in the TivaTrainer program (eurosiva.com). Firstly, our standard plasma target regimen was simulated, and secondly an effect-site target of 3.5 μg/mL was chosen. Thirdly, real infusors were used for measuring the time to reach defined predicted effect-site concentrations when aiming at a plasma target of 6 μg/mL. Identical patient characteristics were used in all simulations: male, 170 cm, 70 kg, 40 years of age. Resulting predicted effect-site peak concentrations, and used bolus doses were recorded, as were the resulting plasma over-shoot, and time frames. The plasma target regimen gave predicted effect-site peaks in the different models ranging from 3.6 to 7.2 μg/mL, reached after 2¾ to 4 minutes. To reach the same effect-site target, the three models used bolus doses ranging from 68 to 150 mg given during 22 to 46 seconds. The predicted plasma concentration over-shoots varied from 5.0 to 13.4 μg/mL. There were obvious differences between the models in the time taken to reach defined effect-site concentrations. We observed clinically significant different results between the models. The choice of model will make a difference for the patient. To eliminate confusion – not necessarily to improve precision – we call for an optimised population based pharmacokinetic model for propofol – a consensus model!

Improvements in logistics could increase survival after out-of-hospital cardiac arrest in Sweden.

In a review based on estimations and assumptions, to report the estimated number of survivors after out‐of‐hospital cardiac arrest (OHCA) in whom cardiopulmonary resuscitation (CPR) was started and to speculate about possible future improvements in Sweden.