Does sevoflurane preserve regional cerebral oxygen saturation measured by near-infrared spectroscopy better than propofol?

OBJECTIVE: The aim of this study was to compare the effect of sevoflurane and propofol on cerebral oxygenation, using regional cerebral oxygen saturation (SrO2) measured by near-infrared spectroscopy (NIRS). STUDY DESIGN: Prospective, randomized, controlled study. PATIENTS AND METHODS: Fifty-four patients aged between 18 and 65 years who underwent elective minor surgery (tumorectomy for breast cancer or inguinal hernia repair) were randomly assigned to receive sevoflurane or propofol anaesthesia. Exclusion criteria included pre-existing cerebrovascular diseases, anaemia, ASA >III, blood loss ≥200 mL, arterial hypotension, baseline pulse oximetry <97%, sign of sensor low quality of SrO2 or bispectral index, and patients with a forehead area <6.5cm. SrO2, bispectral index, haemodynamic data and anaesthetic doses were recorded during surgery. RESULTS: A total of 48 patients were included in the final analysis (24 in each group). There were no significant differences in mean, minimum and maximum SrO2 between sevoflurane and propofol groups. The relative maximum decrease was higher in propofol anaesthesia than sevoflurane anaesthesia (9.6±10.7 versus 4.2±7.2%; P=0.048). Cerebral desaturation (20% reduction from SrO2 baseline during 15 seconds) occurred in 4 patients in propofol group exclusively (P=0.109). SrO2 adjusted for baseline was higher in the sevoflurane group than in the propofol group (67.3±1.8% versus 64.2±1.7%; P=0.018). There were no significant differences in haemodynamic parameters between the two groups. CONCLUSIONS: Cerebral cortical oxygenation measured by NIRS may be better preserved with sevoflurane than with propofol. These findings suggest that sevoflurane anaesthesia could be a good option in patients with compromised cerebral oxygenation, given the absence of intracranial hypertension. Further studies with larger sample sizes are required to support our results.

Which patients are more likely to benefit from postoperative shed blood salvage after unilateral total knee replacement? An analysis of 581 consecutive procedures.

INTRODUCTION: Requirements for allogeneic blood transfusion (ABT) after total knee replacement (TKR) are still high (30-50%), and salvage of unwashed filtered postoperative shed blood (USB) may represent an alternative to ABT. We evaluated that patients are more likely to benefit of USB reinfusion after TKR. PATIENTS AND METHODS: Data from 581 consecutive primary TKR, managed with (reinfusion group, n = 382) or without (control group, n= 199) reinfusion of USB, were retrospectively reviewed. RESULTS: Patients from reinfusion group received 119 +/- 88 ml of red blood cells from USB, without clinically relevant incidents, and showed a lower ABT rate (30.6% vs. 8.4%, for control and reinfusion groups, respectively; P = 0.001) (transfusion trigger, haemoglobin [Hb] < 9 g/dl). Differences in ABT rate between groups were significant for all preoperative Hb levels, except for Hb < or = 12 g/dl. A lower transfusion threshold (Hb < 8 g/dl) might have further decreased ABT rate (14.6% vs. 5.2%, respectively; P < 0.001), with differences being significant for preoperative Hb between 12 and 15 g/dl. There were no differences with respect to postoperative infection rate, but patients from reinfusion group had a shorter length of hospital stay (11 +/- 4 vs. 13 +/- 4 days, respectively; P= 0.001). CONCLUSIONS: Return of USB after TKR seems to reduce the need for ABT, especially in patients with preoperative Hb between 12 and 15 g/dl. There is little benefit of USB reinfusion for patients with preoperative Hb > 15 g/dl, whereas patients with preoperative Hb < 12 g/dl would probably benefit from the combination of USB with some other blood-saving method.

Tetrabrachion: a filamentous archaebacterial surface protein assembly of unusual structure and extreme stability.

The surface (S-) layer of the hyperthermophilic archaebacterium Staphylothermus marinus was isolated, dissected into separate domains by chemical and proteolytic methods, and analyzed by spectroscopic, electron microscopic and biochemical techniques. The S-layer is formed by a poorly ordered meshwork of branched, filiform morphological subunits resembling dandelion seed-heads. A morphological subunit (christened by us tetrabrachion) consists of a 70 nm long, almost perfectly straight stalk ending in four straight arms of 24 nm length that provide lateral connectivity by end-to-end contacts. At 32 nm from the branching point, tetrabrachion carries two globular particles of 10 nm diameter that have both tryptic and chymotryptic protease activity. Tetrabrachion is built by a tetramer of M(r) 92,000 polypeptides that form a parallel, four-stranded alpha-helical rod and separate at one end into four strands. These strands interact in a 1:1 stoichiometry with polypeptides of M(r) 85,000 to form the arms. The arms are composed entirely of beta-sheets. All S-layer components contain bound carbohydrates (glucose, mannose, and glucosamine) at a ratio of 38 g/100 g protein for the complete tetrabrachion-protease complex. The unique structure of tetrabrachion is reflected in an extreme thermal stability in the presence of strong denaturants (1% (w/v) SDS of 6M guanidine): the arms, which are stabilized by intramolecular disulphide bridges, melt around 115 degrees C under non-reducing conditions, whereas the stalk sustains heating up to about 130 degrees C. Complete denaturation of the stalk domain requires treatment with 70% (v/v) sulfuric acid or with fuming trifluoromethanesulfonic acid. The globular protease can be heated to 90 degrees C in 6M guanidine and to 120 degrees C in 1% SDS and represents one of the most stable proteases characterized to date.

An approach to the interpretation of the communicative meaning of visual signals in agonistic behavior of squirrel monkeys.

The repertoire of the visually recognizable agonistice signals of the squirrel monkey can be divided up into classes in such a manner that elements of the same class have a similar, and elements of different classes a different communicative meaning. The differences between these classes are described using quantitative values. An attempt is made to derive clues from these differences for an interpretation of the communicative meaning of the individual classes. The admissibility of the criteria used and the question of the general validity of the quantitative values are discussed.