Compound A production from sevoflurane is not less when KOH-free absorbent is used in a closed-circuit lung model system

In an in vitro study, less compound A was formed when a KOH-free carbon dioxide absorbent was used. To confirm this observation we used a lung model in which carbon dioxide was fed in at 160 ml min(-1) and sampling gas was taken out for analysis at 200 ml min(-1); ventilation aimed for a PE'CO2 of 5.4 kPa. The soda lime canister temperatures in the inflow and outflow ports (Tin and Tout) were recorded. In six runs of 240 min each, a standard soda lime, Sodasorb (Grace, Epernon, France) was used and in eight runs KOH-free Sofnolime (Molecular Products, Thaxted, UK) was used. Liquid sevoflurane was injected using a syringe pump to obtain 2.1% E'. Compound A was measured by capillary gas chromatography combined with mass spectrometry. Median (range) compound Ainsp increased to a maximum of 22.7 (7.9) ppm for Sodasorb and 33.1 (20) for Sofnolime at 60 min and decreased thereafter; the difference between groups was significant (P<0.05) at each time of analysis up to 240 min. The canister temperatures were similar in both groups and increased to approximately 40 degrees C at 240 min. Contrary to expectation, compound A concentrations were greater with the KOH-free absorbent despite similar canister temperatures with both absorbents.

Quantitative determination of vapor-phase compound A in sevoflurane anesthesia using gas chromatography-mass spectrometry

BACKGROUND

During low-flow or closed-circuit anesthesia with the fluorinated inhalation anesthetic sevoflurane, compound A, an olefinic degradation product with known nephrotoxicity in rats, is generated on contact with alkaline CO(2) adsorbents. To evaluate compound A formation and thus potential sevoflurane toxicity, a reliable and reproducible assay for quantitative vapor-phase compound A determination was developed.

METHODS

Compound A concentrations were measured by fully automated capillary gas chromatography-mass spectrometry with cryofocusing. Calibrators of compound A in the vapor phase were prepared from liquid volumetric dilutions of stock solutions of compound A and sevoflurane in ethyl acetate. 1,1,1-Trifluoro-2-iodoethane was chosen as an internal standard. The resulting quantitative method was fully validated.

RESULTS

A linear response over a clinically useful concentration interval (0.3-75 microL/L) was obtained. Specificity, sensitivity, and accuracy conformed with current analytical requirements. The CVs were 4.1-10%, the limit of detection was 0.1 microL/L, and the limit of quantification was 0.3 microL/L. Analytical recoveries were 100.6% +/- 10.1%, 102.5% +/- 7.3%, and 99.0% +/- 4.1% at 0.5, 10, and 75 microL/L, respectively. The method described was used to determine compound A concentrations during simulated closed-circuit conditions. Some of the resulting data are included, illustrating the practical applicability of the proposed analytical approach.

CONCLUSIONS

A simple, fully automated, and reliable quantitative analytical method for determination of compound A in air was developed. A solution was established for sampling, calibration, and chromatographic separation of volatiles in an area complicated by limited availability of sample volume and low concentrations of the analyte.

Therapeutic coma or neuroprotection by anaesthetics

Some surgical patients are at an increased risk for developing cerebral ischaemia. A subset of these patients is believed to benefit from putative cerebroprotective effects of anaesthetic agents. Therefore, in this setting these drugs could have therapeutic modalities, besides their auxiliary functions to make surgery possible. However, both animal and especially human data are very disappointing. Only the barbiturates and isoflurane have an experimental record warranting further research to delineate proper indications for their use as neuroprotective agents in surgical patients.

Hepato-venous reconstruction in orthotopic liver transplantation with preservation of the recipients' inferior vena cava and veno-venous bypass

BACKGROUND AND AIMS

The potential advantages of vena cava-preserving recipient hepatectomy in orthotopic liver transplantation are reduced hemorrhage, improved cardiovascular stability and preserved renal perfusion without the requirement of veno-venous bypass as compared with recipient hepatectomy including the vena cava. No detailed information is available on the use of veno-venous bypass during complicated vena cava preserving recipient hepatectomy and liver transplantation. In the present study, the peri- and postoperative courses of adult liver transplant recipients in whom the hepatovenous reconstruction was performed according to three different techniques with and without the use of veno-venous bypass were investigated.

PATIENTS/METHODS

During primary orthotopic liver transplantation, an end-to-end (ETE) cavo-caval interposition of the donor vena cava to the recipient's vena cava was performed in 75 patients (group I). In 15 patients, a termino-terminal piggyback (PB) anastomosis was constructed to the remnant of the recipient's hepatic vein (group II), and in 72 transplantations a latero-lateral cavo-cavostomy (LLC) of donor-to-recipient's vena cava (group III) was performed. The use of bypass, operative time and cold ischemia time, perioperative blood product requirements, incidence of relaparotomy, the evolution of postoperative renal function, technical complications and the survival were analyzed and compared using multivariate statistics and actuarial techniques for statistical evaluation.

RESULTS

No differences could be found in preoperative patient conditions, donor conditions, operating time, anastomosing time or cold ischemia time. In groups I-III, the veno-venous bypass was used in 50 (67%), 8 (53%) and 6 (8%) cases respectively (P=0.02 for group III). The mean preoperative packed cells requirements were 20.4 vs 29.6 vs 10.8 units (P=0.01 for group III), while postoperative blood product requirements (first 24 h) were 2.6 vs 5.0 vs 0.20 units of packed cells (P=0.02 for group III). Relaparotomy for diffuse retroperitoneal hemorrhage was performed 14 times (19%) in group I, 3 times (20%) in group II and 7 times (8.3%) in group III (P=0.002). The incidence of posteropative early renal dysfunction (increase of > or =1.3 mg% serum creatinine) in group I vs group II vs group III was 24% vs 60% vs 16.7% (P=0.001 for group II) for patients without the use of veno-venous bypass. No significant difference was observed concerning early renal dysfunction in patients where a veno-venous bypass was used. The survival at 12 months was 81% for group I, 86% for group II and 93.0% for group III. In group III there were four complications (P=0.03) at the hepatovenous anastomosis of which two were eventually fatal.

CONCLUSION

Preservation of the recipient's vena cava and LLC can reduce, but not avoid, the requirement for veno-venous bypass. In orthotopic liver transplantation, postoperative hemorrhage, as measured by surgical revisions and requirement for blood products, is significantly reduced with LLC with and without bypass. Early renal dysfunction also occurs in the group of LLC as compared with the termino-terminal cavostomy independent of the bypass. A technical failure resulting in patient death can be associated with LLC.

The influence of sufentanil and/or clonidine on the duration of analgesia after a caudal block for hypospadias repair surgery in children

The aim of this study was to evaluate whether the addition of clonidine, or sufentanil, or both, to a bupivacaine solution for a caudal block prolonged the period of analgesia after operation in children. Sixty ASA class I or II boys, aged between 8 months and 13 years, admitted for hypospadias repair were enrolled into a prospective randomised study. After induction of general anaesthesia and endotracheal intubation the children were allocated into four groups. Group I received 0.5 mL kg(-1) bupivacaine 0.25% caudally, in addition group II received 1 microg kg(-1) clonidine, group III 0.5 microg kg(-1) sufentanil and group IV 0.5 microg kg(-1) clonidine and 0.25 microg kg(-1) sufentanil. The concentrations of clonidine and sufentanil in group IV were halved to reduce possible side-effects with higher dosages. Analgesia and side-effects were assessed 2, 4, 6, 8 and 12 h after operation. No significant differences were found among the four groups for the pain scores at 2, 4, 6, 8 and 12 h. All groups had a similar frequency of vomiting and a comparable appetite and quality of night rest during the first 24 h following the operation. There was no significant difference in the requirement for additional doses of analgesics. The addition of sufentanil, or clonidine, or both, to bupivacaine for caudal administration provides no additional clinical benefit over bupivacaine alone.

Influence of methane on infrared gas analysis of volatile anesthetics

Contemporary multigas analyzers determine anesthetic gas concentrations using (near) infrared analysis at either 3.3 or 8-9 microns. Methane also absorbs infrared light at 3.3 microns, but not at 8-9 microns. Consequently, erroneous anesthetic agent readings may result when methane is present in the circuit (e.g. during closed circuit anesthesia), potentially compromising patient safety. We have analyzed in laboratory conditions the influence of different known methane concentrations (100, 500 and 1000 ppm) on the gas-analysis readings provided by some clinical monitoring devices that use infrared absorption for the measurement of inhalation anesthetic concentration. At 3.3 microns wavelength the influence on the measurement of halothane was important, whereas the influence on that of enflurane and isoflurane was less pronounced. For desflurane and sevoflurane measurements, the influence of methane at 3.3 microns wavelength proved to be minimal. At higher wavelengths (8-9 microns) no influence of methane could be demonstrated.

Transition time: a new parameter coinciding with fair intubating conditions

With rocuronium optimal intubating conditions are earlier achieved than the adductor pollicis muscle onset time. Using the transition time we defined a better parameter for clinical relaxation. The onset of relaxation was determined in 20 patients. After a stable response was achieved with a 0.1 Hz single twitch stimulation 0.60 mg/kg rocuronium was injected. The three different stades during the onset of relaxation were determined. These are the lag time, transition time (transition between second and third phase) and onset time. Whether the transiton time corresponds with optimal intubating conditions was evaluated in 40 other patients. The median transition time was 67.4 (P25:52.5, P75:76.3) seconds with a corresponding relaxation of 76.2 (P25:81.4, P75:70.7)%. The intubating conditions were significantly better at a relaxation level corresponding with the transition time. We conclude that the transition time approximates the intubating time and corresponds with fair intubating conditions. This parameter can be preferred to define the moment with optimal intubating conditions.

Molecular cloning, expression and characterization of the human serine/threonine kinase Akt-3

Akt (also known as PKB or RAC-PK) is an intracellular serine/threonine kinase involved in regulating cell survival. Although this makes it a promising target for the discovery of drugs to treat human cancer, a complicating factor may be the role played by Akt in insulin signalling. Two human isoforms, Akt-1 and Akt-2, have been described previously and a third isoform has been identified in rats (here termed Akt-3, but also called RAC-PK-gamma or PKB-gamma). We describe the identification of the corresponding human isoform of Akt-3. The gene encoding human Akt-3 was localized to chromosome 1q43-44. The predicted protein sequence is 83% identical to human Akt-1 and 78% identical to human Akt-2, and contains a pleckstrin homology domain and a kinase domain. In contrast to the published rat Akt-3 isoform, human and mouse Akt-3 also possess a C-terminal 'tail' that contains a phosphorylation site (Ser472) thought to be involved in the activation of Akt kinases. In addition to phosphorylation of Ser472, phosphorylation of Thr305 also appears to contribute to the activation of Akt-3 because mutation of both these residues to aspartate increased the catalytic activity of Akt-3, whereas mutation to alanine inhibited activation. Akt-3 activity could be inhibited by the broad spectrum kinase inhibitor staurosporine and by the PKC inhibitor Ro 31-8220, but not by other PKC or PKA inhibitors tested. Although Akt-3 is expressed widely, it is not highly expressed in liver or skeletal muscle, suggesting that its principle function may not be in regulating insulin signalling. These observations suggest that Akt-3 is a promising target for the discovery of novel chemotherapeutic agents which do not interfere with insulin signalling.

[Liver transplantation preserving the vena cava and a temporary portocaval shunt]

The experience with laterolateral cavocavostomy for hepatovenous reconstruction in liver transplantation is reviewed with and without the use of a temporary portocaval shunt. A total of 65 liver transplantations were analyzed. In 49 transplantations a laterolateral cavocaval anastomosis was performed (group I). In group II (n = 16) the same technique was used after a temporary portal caval shunt was constructed. Mean arterial pressure (mmHg): group I 128 +/- 34; group II 109 +/- 32. Cardiac output (l/min) decrease during the anhepatic phase was 2.3 +/- 1.9 and 1.2 +/- 1.5, respectively (P < 0.05). The peroperative blood loss measured as the number of packed cells transfused was 16.4 +/- 15.8 versus 1.2 +/- 2.3 (P < 0.04) and fresh frozen plasma 19.0 +/- 14.7 versus 3.7 +/- 4.0 (P < 0.02). Course on ICU (days), liver function tests, renal function and the need for reoperation because of bleeding were not statistically significantly different between the groups. One-year patient survival was 82.7 and 85.7%, respectively. In conclusion, we found that despite preservation of the caval flow during hepatectomy, the additional use of a temporary portocaval shunt was advantageous with regard to peroperative hemorrhage and hemodynamic stability and can potentially facilitate implantation of the liver graft.

Haemodynamic and electroencephalographic response to insertion of a cuffed oropharyngeal airway: comparison with the laryngeal mask airway

We have compared the cuffed oropharyngeal airway (COPA), a modified Guedel airway device with a specially designed cuff at its distal end, with the laryngeal mask airway (LMA), on haemodynamic and electroencephalographic (EEG) responses to insertion. In addition, we examined the haemodynamic and EEG changes during initiation of the effect-compartment controlled infusion. We studied 35 female patients undergoing ambulatory gynaecological surgery allocated randomly to received an LMA or COPA to manage the airway. After premedication with midazolam 0.03 mg kg-1 i.v. and low-dose alfentanil (0.01 mg kg-1), anaesthesia was induced and maintained with propofol, using an effect-compartment controlled infusion set at an effect-site concentration of 4 micrograms ml-1. After intercompartmental equilibration, the LMA (group I) or COPA (group II) was inserted and haemodynamic (arterial pressure, heart rate) and EEG (bispectral index (BIS)) responses to insertion studied. The effect-compartment controlled infusion of propofol caused only mild haemodynamic changes during induction. Changes in arterial pressure and heart rate after insertion were similar in both groups and not significantly different from baseline values before insertion. Changes in BIS after insertion were minor and similar between groups.

Closed-loop controlled administration of propofol using bispectral analysis

Ten patients, undergoing elective orthopaedic surgery under spinal anaesthesia, were sedated with propofol using a closed-loop feedback control system. The bispectral index (BIS), a new processed EEG parameter, was used as control variable. Propofol administration was controlled by a patient individualised adaptive model-based controller incorporating target-controlled infusion technology combined with a pharmacokinetic-dynamic model. This feedback control system for propofol administration proved to be adequate and safe. BIS was found to be well suited as control variable.

Comparison of spontaneous frontal EMG, EEG power spectrum and bispectral index to monitor propofol drug effect and emergence

BACKGROUND

The aim of this study was to investigate the accuracy of frontal spontaneous electromyography (SEMG) and EEG spectral edge frequency (SEF 95%), median frequency (MF), relative delta power (RDELTA) and bispectral index (BIS) in monitoring loss of and return of consciousness and hypnotic drug effect during propofol administration at different calculated plasma target concentrations.

METHODS

Propofol was administered by using a target-controlled infusion at different propofol steady-state concentrations. All variables were measured simultaneously at specific calculated concentrations and endpoints.

RESULTS

Loss of consciousness was accurately monitored by BIS, SEMG and SEF 95%, and propofol drug effect by BIS only. Return of consciousness was predicted by BIS, MF and SEF 95%. Due to the biphasic EEG pattern of propofol and the lack of reproducible data at specific propofol concentrations, the clinical usefulness of SEF 95%, MF and RDELTA was very limited. SEMG was useful to detect loss and return of consciousness, but without predictive value.

CONCLUSIONS

The BIS might be an accurate measure to monitor depth of anaesthesia and hypnotic drug effect. Other neurophysiologic measures have limited value to monitor depth of anaesthesia and hypnotic drug effect.

Arterialization of the portal vein in pediatric liver transplantation. A report of two cases

Portal vein arterialization (PVA) is an acquired concept in shunt surgery for portal hypertension. This technique, recently described as both a temporary and permanent procedure in adult liver transplantation, is reported by the authors in two cases of pediatric transplantation. The indication was low portal blood flow after reperfusion with poor graft function due to persistence of spontaneous retroperitoneal venous shunts. In both cases described, PVA allowed for satisfactory macroscopic liver reperfusion. The increase in portal blood flow from 150 to 500 ml/min in the second patient enabled the liver to be reperfused correctly and led to successful transplantation. The graft function in both cases improved in the 1st postoperative week, but the 1st patient 2 months after transplantation. Signs of hepatic hyperarterialization occurred in the second patient and this necessitated a dearterialization of the portal vein 2 weeks later. Although the benefit of this procedure appears to be beyond doubt in the immediate post-operative period, we have no data on long-term arterialization. We do think that PVA can be performed in pediatric liver transplantation, but it may need to be done only in special, individual situations when no valid alternative can be proposed, such as in the absence of a mesenteric vein and/or the presence of spontaneous retroperitoneal venous shunts.

Methane influences infrared technique anesthetic agent monitors

OBJECTIVE

During closed-circuit anesthesia, anesthetic vapor analysis by infrared absorption at 3.3 microm can be influenced by the concentration of accumulated methane, resulting in inaccurate readings of anesthetic concentrations. The current study examined the influence of different known methane concentrations on the analysis of halothane or isoflurane concentrations by the infrared absorption technique.

METHODS

Three different gas mixtures containing 100, 500 and 1000 ppm methane were given through an experimental sampling bar. Four infrared technique anesthetic agent monitors were examined: (1) the Ultima (Datex), (2) the Andros analyzer (Cato anesthesia machine, Driger), (3) the anesthetic gas monitor 1304 (Brüel & Kjaer) and (4) the mainstream analyzer Irina (Drager). All devices, except the Brüel & Kjaer anesthetic gas monitor, function at 3.3 microm wavelength. The Brüel & Kjaer apparatus functions at 10.3-13 microm wavelength. The readings were recorded with and without addition of halothane (or isoflurane) at a halothane (or an isoflurane) dedicated sensitivity after application of methane.

RESULTS

At the two highest methane concentrations (500 and 1000 ppm) all studied devices except the Brüel & Kjaer anesthetic gas monitor 1304 displayed inaccurate anesthetic concentrations. This was more pronounced at halothane than at isoflurane sensitivity. Introduction of halothane (0.8%) or isoflurane (0.8%) vapor into the experimental sampling bar resulted in values that were additive to the falsely recorded ones.

CONCLUSIONS

In closed circuit or low-flow anesthesia, in which methane can accumulate, infrared measuring techniques for potent inhalation anesthetics that do not use the 3.3 microm wavelength appear to be preferable.

Clinical usefulness of the bispectral index for titrating propofol target effect-site concentration

The bispectral index, a new processed electroencephalographic parameter which may give information on depth of anaesthesia, was used in 58 patients undergoing outpatient gynaecological surgery in order to study if the addition of bispectral index monitoring to standard clinical monitoring could improve the titration of target propofol concentration when using effect-site target-controlled propofol infusion for sedation. In Group 1 (n = 30), the bispectral index was recorded but the anaesthetist was unaware of the readings and therefore only classical signs of depth of anaesthesia were used to guide the anaesthetist in controlling the effect-site concentration. In Group 2 (n = 28), bispectral index readings were available to the anaesthetist and effect-site concentration was adjusted to ensure that bispectral index was maintained between 40 and 60. Similar propofol induction and maintenance doses, blood and effect-site concentrations and mean bispectral index were found in the two groups. A greater percentage of bispectral index readings lying outside the target range (i.e. < 40 or > 60) and more movement at incision and during maintenance were found in Group 1. There was a trend towards more implicit awareness in patients in Group 1. Bispectral index was found to be useful for measuring depth of sedation when using propofol target-controlled infusion. Propofol dosage could not be decreased but a more consistent level of sedation could be maintained due to a more satisfactory titration of target effect-site concentration.

In vitro evaluation of the effect of profound haemodilution with hydroxyethyl starch 6%, modified fluid gelatin 4% and dextran 40 10% on coagulation profile measured by thromboelastography

Synthetic colloids have been implicated as a cause of coagulopathy when administered in large quantities. The effect of profound haemodilution (50%) on coagulation profile was measured in vitro by thromboelastography. Blood samples were taken from 11 ASA grade 1 patients prior to induction of anaesthesia for elective surgery. Each sample was simultaneously tested in four different preparations: undiluted blood (control sample); blood diluted with hydroxyethyl starch 6%; blood diluted with modified fluid gelatin 4%; blood diluted with dextran 40 10%. There was a significant decrease in reaction time in the preparations treated with hydroxyethyl starch 6% and modified fluid gelatin 4%, reflecting activation of initial fibrin formation. A significant increase in clot formation time was noted in the hydroxyethyl starch 6%-treated preparations. There was also a significant decrease in clot formation rate and maximum amplitude in the hydroxyethyl starch 6% group. Clot formation time, clot formation rate and maximum amplitude did not change in the modified fluid gelatin 4% group. Profound haemodilution with dextran 40 10% exerted extreme effects on the measured variables, very often resulting in a straight line on the thromboelastography profile.