Thermal suit in preventing unintentional intraoperative hypothermia during general anaesthesia: a randomized controlled trial.

BACKGROUND: Unintentional perioperative hypothermia causes serious adverse effects to surgical patients. Thermal suit (T-Balance® ) is an option for passive warming perioperatively. We hypothesized that the thermal suit will not maintain normothermia more efficiently than conventional cotton clothes when also other preventive procedures against unintentional hypothermia are used. METHODS: One hundred patients were recruited to this prospective, randomized trial. They were allocated to the Thermal Suit group or a Control group wearing conventional hospital cotton clothes. All patients received our institution's standard treatment against unintentional hypothermia including a warming mattress, a forced-air upper body warming blanket and a warming device for intravenous fluids. Eardrum temperature was measured pre-operatively. In the operating room and post-anaesthesia care unit temperatures were measured from four locations: oesophagus, left axilla, dorsal surface of the left middle finger and dorsum of the left foot. The primary outcome measure was temperature change during robotic-assisted laparoscopic radical prostatectomy. RESULTS: The temperatures of 96 patients were analysed. There was no difference in mean core temperatures, axillary temperatures or skin temperatures on the finger between the groups. Only foot dorsum temperatures were significantly lower in the Thermal Suit group. Intraoperative temperature changes were similar in both groups. In the post-anaesthesia care unit temperature changes were minimal and they did not differ between the groups. CONCLUSION: Provided that standard preventive procedures in maintaining normothermia are effective the thermal suit does not provide any additional benefit over conventional cotton clothes during robotic-assisted laparoscopic radical prostatectomy.

Comparison of Bispectral Index and Entropy values with electroencephalogram during surgical anaesthesia with sevoflurane.

BACKGROUND: Concomitantly recorded Bispectral Index® (BIS) and Entropy™ values sometimes show discordant trends during general anaesthesia. Previously, no attempt had been made to discover which EEG characteristics cause discrepancies between BIS and Entropy. We compared BIS and Entropy values, and analysed the changes in the raw EEG signal during surgical anaesthesia with sevoflurane. METHODS: In this prospective, open-label study, 65 patients receiving general anaesthesia with sevoflurane were enrolled. BIS, Entropy and multichannel digital EEG were recorded. Concurrent BIS and State Entropy (SE) values were selected. Whenever BIS and SE values showed ≥10-unit disagreement for ≥60 s, the raw EEG signal was analysed both in time and frequency domain. RESULTS: A ≥10-unit disagreement ≥60 s was detected 428 times in 51 patients. These 428 episodes accounted for 5158 (11%) out of 45 918 analysed index pairs. During EEG burst suppression, SE was higher than BIS in 35 out of 49 episodes. During delta-theta dominance, BIS was higher than SE in 141 out of 157 episodes. During alpha or beta activity, SE was higher than BIS in all 49 episodes. During electrocautery, both BIS and SE changed, sometimes in the opposite direction, but returned to baseline values after electrocautery. Electromyography caused index disagreement four times (BIS > SE). CONCLUSIONS: Certain specific EEG patterns, and artifacts, are associated with discrepancies between BIS and SE. Time and frequency domain analyses of the original EEG improve the interpretation of studies involving BIS, Entropy and other EEG-based indices. CLINICAL TRIAL REGISTRATIONCLINICALTRIALSGOVIDENTIFIER: NCT01077674.

Can electromyographic arousal be detected visually on the Datex-Ohmeda S/5™ anesthesia monitor?

BACKGROUND: Electroencephalogram (EEG)-based depth of anaesthesia monitoring is susceptible to contaminating electromyographic (EMG) activity. Many authorities have suggested that anaesthesiologists using these monitors should interpret the raw EEG waveform seen on the anaesthesia monitor. METHODS: In 34 patients anaesthetized with propofol using two doses of rocuronium (0.6 and 1.2 mg/kg), we studied whether the EMG arousal can be detected visually on the anaesthesia monitor. The Bispectral Index (BIS) and Entropy biosignals on the monitor were recorded with a video camera, and the one-channel EEG recorded by the Entropy strip was collected on a laptop computer. The recordings and the one-channel EEG were analyzed offline by two experts (anaesthesiologist and neurophysiologist), both with a long experience on anaesthesia-related EEG. RESULTS: EMG arousal existed in 14/34 and 13/33 patients in the BIS and Entropy biosignals, respectively. The anaesthesiologist detected EMG on the monitor in 7/14 patients with BIS (sensitivity 50%) and in 4/13 patients with Entropy (31%). The clinical neurophysiologist detected EMG in 6/14 (43%) patients with BIS and in 5/13 (38%) with Entropy. The specificity of the EMG analyses was 55 and 65% with BIS, and 85 and 90% with Entropy. EMG arousal was detected in BIS biosignal in 10/17 and 4/17 patients with 0.6 and 1.2 mg/kg doses of rocuronium (P = 0.04). CONCLUSIONS: In contrast to many EEG phenomena, EMG activity cannot be accurately detected visually from the raw EEG on the anaesthesia monitor. Further development in the quality of the anaesthesia monitors is warranted.

Surface modification of fiber reinforced polymer composites and their attachment to bone simulating material.

The purpose of this study was to investigate the effect of fiber orientation of a fiber-reinforced composite (FRC) made of poly-methyl-methacrylate (PMMA) and E-glass to the surface fabrication process by solvent dissolution. Intention of the dissolution process was to expose the fibers and create a macroporous surface onto the FRC to enhance bone bonding of the material. The effect of dissolution and fiber direction to the bone bonding capability of the FRC material was also tested. Three groups of FRC specimens (n = 18/group) were made of PMMA and E-glass fiber reinforcement: (a) group with continuous fibers parallel to the surface of the specimen, (b) continuous fibers oriented perpendicularly to the surface, (c) randomly oriented short (discontinuous) fibers. Fourth specimen group (n = 18) made of plain PMMA served as controls. The specimens were subjected to a solvent treatment by tetrahydrofuran (THF) of either 5, 15 or 30 min of time (n = 6/time point), and the advancement of the dissolution (front) was measured. The solvent treatment also exposed the fibers and created a surface roughness on to the specimens. The solvent treated specimens were embedded into plaster of Paris to simulate bone bonding by mechanical locking and a pull-out test was undertaken to determine the strength of the attachment. All the FRC specimens dissolved as function of time, as the control group showed no marked dissolution during the study period. The specimens with fibers along the direction of long axis of specimen began to dissolve significantly faster than specimens in other groups, but the test specimens with randomly oriented short fibers showed the greatest depth of dissolution after 30 min. The pull-out test showed that the PMMA specimens with fibers were retained better by the plaster of Paris than specimens without fibers. However, direction of the fibers considerably influenced the force of attachment. The fiber reinforcement increases significantly the dissolution speed, and the orientation of the glass fibers has great effect on the dissolving depth of the polymer matrix of the composite, and thus on the exposure of fibers. The glass fibers exposed by the solvent treatment enhanced effectively the attachment of the specimen to the bone modeling material.

Elevated BIS and Entropy values after sugammadex or neostigmine: an electroencephalographic or electromyographic phenomenon?

BACKGROUND: Sugammadex is designed to antagonize neuromuscular blockade (NMB) induced by rocuronium or vecuronium. In clinical practice, we have noticed a rise in the numerical values of bispectral index (BIS) and Entropy, two electroencephalogram (EEG) - based depth of anesthesia monitors, during the reversal of the NMB with sugammadex. The aim of this prospective, randomized, double-blind study was to test this impression and to compare the effects of sugammadex and neostigmine on the BIS and Entropy values during the reversal of the NMB. METHODS: Thirty patients undergoing gynecological operations were studied. Patients were anesthetized with target-controlled infusions of propofol and remifentanil, and rocuronium was used to induce NMB. After operation, during light propofol-remifentanil anesthesia, NMB was antagonized with sugammadex or neostigmine. During the following 5 min, the numerical values of BIS, BIS electromyographic (BIS EMG) and Entropy were recorded on a laptop computer, as well as the biosignal recorded by the Entropy strip. The Entropy biosignal was studied off-line both in time and frequency domain to see if NMB reversal causes changes in EEG. RESULTS: In some patients, administration of sugammadex or neostigmine caused a significant rise in the numerical values of BIS, BIS EMG and Entropy. This phenomenon was most likely caused by increased electromyographic (EMG) activity. The administration of sugammadex or neostigmine appeared to have only minimal effect on EEG. CONCLUSION: The EMG contamination of EEG causes BIS and Entropy values to rise during reversal of rocuronium-induced NMB in light propofol-remifentanil anesthesia.

Explaining Entropy responses after a noxious stimulus, with or without neuromuscular blocking agents, by means of the raw electroencephalographic and electromyographic characteristics.

BACKGROUND: Entropy™, an anaesthetic EEG monitoring method, yields two parameters: State Entropy (SE) and Response Entropy (RE). SE reflects the hypnotic level of the patient. RE covers also the EMG-dominant part of the frequency spectrum, reflecting the upper facial EMG response to noxious stimulation. We studied the EEG, EMG, and Entropy values before and after skin incision, and the effect of rocuronium on Entropy and EMG at skin incision during sevoflurane-nitrous oxide (N2O) anaesthesia. METHODS: Thirty-eight patients were anaesthetized with sevoflurane-N2O or sevoflurane-N2O-rocuronium. The biosignal was stored and analysed off-line to detect EEG patterns, EMG, and artifacts. The signal, its power spectrum, SE, RE, and RE-SE values were analysed before and after skin incision. The EEG arousal was classified as ß (increase in over 8 Hz activity and decrease in under 4 Hz activity with a typical ß pattern) or δ (increase in under 4 Hz activity with the characteristic rhythmic δ pattern and a decrease in over 8 Hz activity). RESULTS: The EEG arousal appeared in 17 of 19 and 15 of 19 patients (NS), and the EMG arousal in 0 of 19 and 13 of 19 patients (P<0.01) with and without rocuronium, respectively. Both ß (n=30) and EMG arousals increased SE and RE. The δ arousal (n=2) decreased both SE and RE. A significant increase in RE-SE values was only seen in patients without rocuronium. CONCLUSIONS: During sevoflurane-N2O anaesthesia, both EEG and EMG arousals were seen. ß and δ arousals had opposite effects on the Entropy values. The EMG arousal was abolished by rocuronium at the train of four level 0/4.

Osteoblast response to polymethyl methacrylate bioactive glass composite.

Polymethylmethacrylate (PMMA) has been used in many orthopedic and dental applications since the 1960s. Biocompatibility of newly developed surface porous fiber reinforced (SPFR) PMMA based composite has not been previously proven in cell culture environment. Analysis of rat bone marrow stromal cells grown on the different test materials showed only little difference in normalized cell activity or bone sialoprotein (BSP) production between the test materials, but the osteocalcin (OC) levels remained higher (P < 0.015-0.005) through out the test with SPFR-material when compared to tissue culture poly styrene (TCPS). The cells grown on SP-FRC material also showed highest calcium depletion from the culture medium (P < 0.026-0.001) when compared to all other test substrates. SEM images of the cultured samples confirmed that all the materials enabled cell spreading and growth on their surface, but the roughened surface remarkably enhanced this process of cell attachment, division and calcified nodule formation. This study shows that the SP-FRC composite material does not elicit harmful/toxic reactions in cell cultures more than neutral TCPS and can be considered biocompatible. The material possesses good capabilities to form new mineralized tissue onto its surface, and through that a possibility to bond directly to bone. Rough surface seems to enhance osteoblast proliferation and formation of mineralized extracellular matrix.

Effects of heat treatment of wood on hydroxylapatite type mineral precipitation and biomechanical properties in vitro.

Wood is a natural fiber reinforced composite. It structurally resembles bone tissue to some extent. Specially heat-treated birch wood has been used as a model material for further development of synthetic fiber reinforced composites (FRC) for medical and dental use. In previous studies it has been shown, that heat treatment has a positive effect on the osteoconductivity of an implanted wood. In this study the effects of two different heat treatment temperatures (140 and 200 degrees C) on wood were studied in vitro. Untreated wood was used as a control material. Heat treatment induced biomechanical changes were studied with flexural and compressive tests on dry birch wood as well as on wood after 63 days of simulated body fluid (SBF) immersion. Dimensional changes, SBF sorption and hydroxylapatite type mineral formation were also assessed. The results showed that SBF immersion decreases the biomechanical performance of wood and that the heat treatment diminishes the effect of SBF immersion on biomechanical properties. With scanning electron microscopy and energy dispersive X-ray analysis it was shown that hydroxylapatite type mineral precipitation formed on the 200 degrees C heat-treated wood. An increased weight gain of the same material during SBF immersion supported this finding. The results of this study give more detailed insight of the biologically relevant changes that heat treatment induces in wood material. Furthermore the findings in this study are in line with previous in vivo studies.

Facial muscle activity, Response Entropy, and State Entropy indices during noxious stimuli in propofol-nitrous oxide or propofol-nitrous oxide-remifentanil anaesthesia without neuromuscular block.

BACKGROUND: Entropy is an anaesthetic EEG monitoring method, calculating two numerical parameters: State Entropy (SE, range 0-91) and Response Entropy (RE, range 0-100). Low Entropy numbers indicate unconsciousness. SE uses the frequency range 0.8-32 Hz, representing predominantly the EEG activity. RE is calculated at 0.8-47 Hz, consisting of both EEG and facial EMG. RE-SE difference (RE-SE) can indicate EMG, reflecting nociception. We studied RE-SE and EMG in patients anaesthetized without neuromuscular blockers. METHODS: Thirty-one women were studied in propofol-nitrous oxide (P) or propofol-nitrous oxide-remifentanil (PR) anaesthesia. Target SE value was 40-60. RE-SE was measured before and after endotracheal intubation, and before and after the commencement of surgery. The spectral content of the signal was analysed off-line. Appearance of EMG on EEG was verified visually. RESULTS: RE, SE, and RE-SE increased during intubation in both groups. Elevated RE was followed by increased SE values in most cases. In these patients, spectral analysis of the signal revealed increased activity starting from low (<20 Hz) frequency area up to the highest measured frequencies. This was associated with appearance of EMG in raw signal. No spectral alterations or EMG were seen in patients with stable Entropy values. CONCLUSIONS: Increased RE is followed by increased SE at nociceptive stimuli in patients not receiving neuromuscular blockers. Owing to their overlapping power spectra, the contribution of EMG and EEG cannot be accurately separated with frequency analysis in the range of 10-40 Hz.

Polymethylmethacrylate composites: disturbed bone formation at the surface of bioactive glass and hydroxyapatite.

The effects of polymethylmethacrylate on bone formation were studied alone and as composites in combination with hydroxyapatite and bioactive glass in the rabbit subchondral femur. Radiographs, histology, computer assisted histomorphometry, scanning electron microscopy and energy dispersive X-ray analysis were used for evaluation. A total of 60 cones were implanted for 3, 6 and 12 weeks. The composite cones consisted of granules of bioactive glass (S56.5P4) or hydroxyapatite embedded in polymethylmethacrylate. Pure polymethylmethacrylate cones served as controls. At the interface of the cones, bone contact was observed only when bioactive glass or hydroxyapatite was present at the cone surface. Fibrous tissue was always found at the polymethylmethacrylate-tissue interface. The osteoconductive bone formation at the surface of bioactive glass and hydroxyapatite was disturbed by polymethylmethacrylate. It seemed to resist bone formation at the interface of both bioactive glass and hydroxyapatite. However, bioactive glass was better able to withstand the detrimental effect of polymethylmethacrylate than hydroxyapatite.

Determination of callus quantity in 4-week-old fractures of the rat tibia.

In clinical practice the quantity of fracture callus is usually estimated on the basis of radiographs. In experimental studies on fracture healing, more exact chemical measurements (total protein, DNA, and mineral contents) have been used to quantitate the amount of callus. It is not known, however, how these two parameters correlate with each other. In this study we used different (radiographic, histomorphometric, and chemical) methods to evaluate the quantity of fracture callus in 4-week-old tibial fractures of rats stabilized by intramedullary nailing. The wet and dry weights and the nitrogen, collagen, calcium, phosphorus, and DNA contents of the calluses showed no correlation with the radiographic size of the calluses. There was a strong correlation (p less than 0.001), however, between radiographic and histomorphometric callus sizes. The mass of callus and the chemically defined parameters of callus production thus indicate different properties of the healing bone.

Electrostimulation of rat callus cells and human lymphocytes in vitro.

Asymmetrical pulsing low voltage current was supplied via electrodes to cultured rat fracture callus cells and human peripheral blood lymphocytes. The [3H]thymidine incorporation of the callus cells and 5-[125I]iodo-2'-deoxyuridine incorporation of the lymphocytes were determined. The growth pattern of callus cells (estimated by cellular density) did not respond to electrical stimulation. However, the uptake of [3H]thymidine was increased at the early phase of cell proliferation and inhibited at later phases of proliferation. The [3H]thymidine uptake of confluent callus cell cultures did not respond to electrical stimulation. Lymphocytes reacted in a similar way; stimulated cells took up more DNA precursor than control cells at the early phase of stimulation. During cell division, induced by the mitogens phytohemagglutinin and Concanavalin-A, the uptake of DNA precursor by stimulated cells was constantly inhibited. The results suggest that electrical stimuli affect the uptake mechanisms of cell membranes. The duality of the effect seems to be dependent on the cell cycle.

Treatment results of osteogenic sarcoma. An evaluation of 36 patients treated during 30-year period in south-western Finland.

Histological re-evaluation revealed 36 osteogenic sarcoma (OS) patients for analysis in South-Western Finland treated between 1958 and 1987. In 21 cases (58%) the tumour was located in the knee region. The mean age at diagnosis was 28 years (range: 5-62 years) and the follow-up time of the patients was at least 5 years or until death. In 29 patients without metastases at the time of diagnosis, the extent of the primary tumour was T2 in 37% and T3 in 63% of the patients. There were no differences regarding the extent of the primary tumour, delay of the diagnosis, mean age of the patients, or duration of the symptoms while comparing the three decades of the study. Before the 1970s the treatment consisted of surgery with or without radiotherapy in most cases. Since the 1970s the combination of surgical treatment (amputation or wide excision) and adjuvant chemotherapy was the most common treatment modality. Since the late 1970s limb-salvage surgery has been applied in selected cases, and it seems to be justified. None of the patients treated before 1970 survived for 5 years. The 5- and 10-year survival of all 36 patients was 44.4% and 33.6%, respectively. In non-metastatic patients both the 5- and 10-year disease-free survival was 46.7%. A certain group exhibiting a good prognosis was found; the 10-year survival of the 10 patients with OS in extremities, treated with combined chemotherapy and surgery, was 70%. The median survival time was significantly longer for the patients with an intracompartmental tumour extent of T2 (112 months) compared with an extracompartmental extent of T3 (23 months), and for the patients with the primary tumour in the knee region (112 months) compared with other locations (18 months). The long-term survival of the OS patients has improved concomitantly with the multimodality of the treatment.

Ultrastructure of human osteosarcoma. Malignant transformation of a multipotential connective tissue cell.

Ten cases of osteosarcoma were studied by electron microscopy. The tumors consisted of six cell types: fibroblastic, myofibroblastic, chondroblastic, osteoblastic, unclassified and histiocytic cells. Disturbed structure of dilated endoplasmic reticulum was a common feature. The neoplastic character of myofibroblastic and histiocytic cells is controversial. Myofibroblastic differentiation was most abundant in parosteal osteosarcoma and in fibrosarcomatous intraosseal osteosarcoma. The malignant cells sometimes formed giant cells and many aggregates of these cells were seen. Osteoclasts and other reactive cells were encountered and this may indicate host reaction against the tumor cells. Formation of collagenous and cartilaginous ground substance was poor, and the capacity of collagen to mineralize was decreased. It is concluded that osteosarcoma is the malignancy of a multipotential connective tissue cell which forms callus in normal osteogenesis.

Cystic osteolysis induced by silicone rubber prosthesis.

Synovitic symptoms and radiologically documented cystic lesions in several carpal bones and distal radius developed two years after the implantation of silicone rubber scaphoid prosthesis for pseudoarthrosis. Open biopsy revealed granulomatous synovitis and osteitis and foreign material in carpal tissues. Ultrastructurally dense material was found in the cytoplasm of histiocytic, often multinucleated cells. Electron-probe analysis of the material showed a definite peak for silicon, proving the causal relationship of symptoms and signs to the silicone rubber prosthesis.

Effect of heat treatment of wood on the morphology, surface roughness and penetration of simulated and human blood.

BACKGROUND: Wood has been used as a model material for the development of novel fiber-reinforced composite bone substitute biomaterials. In previous studies heat treatment of wood was perceived to significantly increase the osteoconductivity of implanted wood material. AIM: The objective of this study was to examine some of the changing attributes of wood materials that may contribute to improved biological responses gained with heat treatment. METHODS: Untreated and 140°C and 200°C heat-treated downy birch (Betula pubescens Ehrh.) were used as the wood materials. Surface roughness and the effect of pre-measurement grinding were measured with contact and non-contact profilometry. Liquid interaction was assessed with a dipping test using two manufactured liquids (simulated blood) as well as human blood. SEM was used to visualize possible heat treatment-induced changes in the hierarchical structure of wood. RESULTS: The surface roughness was observed to significantly decrease with heat treatment. Grinding methods had more influence on the surface contour and roughness than heat treatment. The penetration of the human blood in the 200°C heat-treated exceeded that in the untreated and 140°C heat-treated materials. SEM showed no significant change due to heat treatment in the dry-state morphology of the wood. DISCUSSION: The results of the liquid penetration test support previous findings in literature concerning the effects of heat treatment on the biological response to implanted wood. Heat-treatment has only a marginal effect on the surface contour of wood. The highly specialized liquid conveyance system of wood may serve as a biomimetic model for the further development of tailored fiber-composite materials.