Effect of two cleaning processes for bone allografts on gentamicin impregnation and in vitro antibiotic release.

Bone allografts are a useful and sometimes indispensable tool for the surgeon to repair bone defects. Microbial contamination is a major reason for discarding allografts from bone banks. To improve the number of safe allografts, we suggest chemical cleaning of the grafts followed by antibiotic impregnation. Comparison of two chemical cleaning processes for bone allografts aiming for antibiotic impregnation and consequently delivery rates in vitro. Bone chips of 5-10 mm were prepared from human femoral heads. Two cleaning methods (cleaning A and cleaning B) based on solutions containing hydrogen peroxide, paracetic acid, ethanol and biological detergent were carried out and compared. After the cleaning processes, the bone chips were impregnated with gentamicin. Bacillus subtilis bioassay was used to determine the gentamicin release after intervals of 1-7 days. Differences were compared with non-parametric Mann-Whitney U tests. The zones of inhibition obtained from the bone grafts cleaned with both cleaning processes were similar between the groups. The concentration of the released antibiotic was decreasing gradually over time, following a similar pattern for both groups. The cleaning procedure A as well as the cleaning procedure B for bone allografts allowed the impregnation with gentamicin powder in the same concentrations in both groups. The delivery of gentamicin was similar for both groups. Both cleaning procedures were easy to be carried out, making them suitable for routine use at the bone banks.

Effect of storage temperature on gentamicin release from antibiotic-coated bone chips.

Freezing is the most common method for storing bones until use in skeletal reconstruction. However, the effect of freezing on antibiotic delivery from antibiotic-coated bone has not been evaluated. In this study, we compared antibiotic delivery in vitro from gentamicin-coated human bone stored at different temperatures. Bone chips obtained from human femur heads were chemically cleaned and mixed with gentamicin sulfate. Samples were stored for 4 months at -20 °C, 4 months at -80 °C, or evaluated immediately without freezing. Antibiotic release from the bone chips was measured using Bacillus subtilis as an indicator strain. Zones of inhibition and rates of gentamicin release were similar in all three groups. Storage at -20 and -80 °C for bone allografts has no effect on gentamicin release from chemically cleaned bone chips.

Staphylococcus aureus biofilm formation and antibiotic susceptibility tests on polystyrene and metal surfaces.

AIM: We compared the MBEC™-HTP assay plates made of polystyrene with metal discs composed of TMZF(®) and CrCo as substrates for biofilm formation. METHODS AND RESULTS: Staphylococcus aureus was grown on polystyrene and on metal discs made of titanium and chrome-cobalt. Antibiotic susceptibility was assessed by examining the recovery of cells after antibiotic exposure and by measuring the biofilm inhibitory concentration (BIC). The minimal inhibitory concentration (MIC) was assessed with planktonic cells. Bacterial growth was examined by scanning electron microscopy. The antibiotic concentration for biofilm inhibition (BIC) was higher than the MIC for all antibiotics. Microscopic images showed the biofilm structure characterized by groups of cells covered by a film. CONCLUSIONS: All models allowed biofilm formation and testing with several antibiotics in vitro. Gentamicin and rifampicin are the most effective inhibitors of Staph. aureus biofilm-related infections. We recommend MBEC™-HTP assay for rapid testing of multiple substances and TMZF(®) and CrCo discs for low-throughput testing of antibiotic susceptibility and for microscopic analysis. SIGNIFICANCE AND IMPACT OF THE STUDY: In vitro assays can improve the understanding of biofilms and help developing methods to eliminate biofilms from implant surfaces. One advantage of the TMZF(®) and CrCo discs as biofilm in vitro assay is that these metals are commonly used for orthopaedic implants. These models are usable for future periprosthetic joint infection studies.

Low-energy shock waves enhance the susceptibility of staphylococcal biofilms to antimicrobial agents in vitro.

Biofilm-associated infections in wounds or on implants are difficult to treat. Eradication of the bacteria is nearly always impossible, despite the use of specific antibiotics. The bactericidal effects of high-energy extracorporeal shock waves on Staphylococcus aureus have been reported, but the effect of low-energy shock waves on staphylococci and staphylococcal biofilms has not been investigated. In this study, biofilms grown on stainless steel washers were examined by electron microscopy. We tested ten experimental groups with Staph. aureus-coated washers and eight groups with Staph. epidermidis. The biofilm-cultured washers were exposed to low-energy shock waves at 0.16 mJ/mm(2) for 500 impulses. The washers were then treated with cefuroxime, rifampicin and fosfomycin, both alone and in combination. All tests were carried out in triplicate. Viable cells were counted to determine the bactericidal effect. The control groups of Staph. aureus and Staph. epidermidis revealed a cell count of 6 × 10(8) colony-forming units/ml. Complete eradication was achieved using the combination of antibiotic therapy (single antibiotic in Staph. aureus, a combination in Staph. epidermidis) and shock wave application (p < 0.01). We conclude that shock waves combined with antibiotics could be tested in an in vitro model of infection.

[Value of EEG monitoring in intensive care patients in plastic surgery--indications and experiences]. / EEG-Monitoring bei Intensivpatienten in der Plastischen Chirurgie--Indikationen und Erfahrungen.

EEG monitoring can be performed at the patients' bedside and it is a valuable support in therapeutic decision making providing unique information about the functional state of the brain. Due to newer technical developments, EEG monitoring can be conducted rather easily. In this article, indications for EEG monitoring in plastic surgical patients are presented: controlling the level of sedation, use in states of increased intracranial pressure, screening the cerebral state in comatose patients, diagnosis and therapy of epileptic seizures, and the search for circumscribed cerebral abnormalities. Furthermore, practical experience with the use of the new EEG monitor Narcotrend, which is provided with an automatic EEG classification, is described.

Acid-base, electrolyte and metabolite concentrations in packed red blood cells for major transfusion in infants.

METHODS: Acid-base, electrolyte and metabolite concentrations were determined in 100 U of packed red blood cells (RBC) preserved in extended-storage media to be used for major transfusion in paediatric and cardiac surgery. RESULTS: In fresh RBC, low pH, bicarbonate (cHCO3-), base excess (BE) and high glucose values were observed all outside the physiological range. With lengthening storage duration, values of pH, cHCO3-, BE, sodium and glucose decreased and carbon dioxide, potassium and lactic acid concentrations increased [mean +/- SD (range): storage duration 6.7 +/- 3.8 (1-17) days, pH 6.79 +/- 0.1 (6.53-6.99); mmol.l-1: cHCO3- 11.1 +/- 1.5 (6.2-14.5), BE - 29.2 +/- 4.1 ([-39.4] - [-20.9]), potassium 20.5 +/- 7.8 (4.2-43.6), glucose 24.1 +/- 6.1 (16.7-29.2), lactic acid 9.4 +/- 4 (4.3-21.4)]. CONCLUSION: Massive and rapid transfusion of RBC may lead to a severe burden of hydrogen ions, carbon dioxide, potassium, glucose and lactic acid and this can be avoided by cell saver blood processing, when autologous erythrocytes from the operative field are saved and substrate load and storage lesions from packed red blood cells are minimized in one step by washing.

Haemodynamic, acid-base and electrolyte changes during plasma replacement with hydroxyethyl starch or crystalloid solution in young pigs.

We investigated haemodynamic, acid-base and electrolyte changes during almost total plasma replacement with hydroxyethyl starch (HES) and physiological balanced electrolyte solution (PBE) by using a cell saver in ten young pigs. In the PBE group an additional 3550 (444) ml crystalloid solution [Mean (SD)] was infused over the course of the study in order to maintain pulmonary capillary wedge pressure. Plasma protein levels decreased in both groups and the colloid osmotic pressure increased in HES and decreased in PBE. At the end of the study, body weight [HES 10.4 (1), PBE 13.1 (1.4) kg, P < 0.01] and lactic acid concentration [HES 0.9 (0.3), PBE 2.9 (1. 3) mmol.l -1, P < 0.01] was higher and tissue oxygen delivery [HES 327 (22), PBE 89 (29) ml.min.m2, P < 0.01] was lower in the PBE group. There were only moderate acid-base changes in both groups, but at the end, anion gap was significant lower in HES. In conclusion, maintenance of colloid osmotic pressure close to the physiological range of infants seems to be advantageous during major paediatric surgery.

Septicaemia and endomyocarditis caused by Aerococcus urinae.

Aerococcus urinae, an uncommon urinary tract pathogen, was recently shown to cause septicaemia and endocarditis in a few patients in Denmark and the Netherlands. In Austria this is the first report of a fatal course of endomyocarditis by Aerococcus urinae, associated with multiple septic infarcts.

E-test for susceptibility testing of Mycobacterium tuberculosis.

SETTING: Initial isolates should be tested for drug susceptibility to confirm the anticipated effectiveness of chemotherapy. OBJECTIVE: To evaluate E-test strips for susceptibility testing of Mycobacterium tuberculosis. DESIGN: A proportion method using Lowenstein-Jensen medium and the Bactec radiometric system were compared with the E-test (isoniazid [INH], rifampicin [RMP], ethambutol [EMB] and streptomycin [SM]). RESULTS: For 73 of the 81 M. tuberculosis isolates (90.1%) the proportion and E-test methods yielded concordant susceptibility results against all four antimicrobial agents tested. Of these 73 strains, 69 were fully susceptible; the four isolates showing resistance to antimicrobial drugs by both methods were also resistant when tested by Bactec 460TB. While the proportion method indicated susceptibility for the eight remaining strains, E-test results showed mono EMB resistance in five strains, INH resistance for two isolates (including one isolate resistant to EMB plus INH), and for one strain E-test yielded resistance to EMB and SM. Using Bactec as the reference method, the E-test resulted in false resistance in eight strains and no false susceptibility. CONCLUSION: Due to a substantial rate of false resistance, this method cannot be recommended at present for practical use in clinical laboratories.

[Shortest possible muscle relaxation in children using atracurium and/or vecuronium]. / Kürzestmögliche Muskelrelaxation bei Kindern unter Verwendung von Atracurium und/oder Vecuronium.

The aim of this study was to monitor accelographically the impact of atracurium (A) and/or vecuronium (V) on intubation anaesthesia in infants and/or children for elective surgery or minor short-term surgery. An intra-individual evaluation is valid even though a very practical but less established monitoring method is used. Infants receiving a "priming"-dose of V 0.01 mg kg-1 BW or A 0.05 mg kg-1 BW followed 3 minutes later by a main dose of V 0.04 mg kg-1 BW or A 0.2 mg kg-1 BW were found to be in good or even very good intubation condition. These minimal doses afforded very short relaxation times, which are next in line to succinylcholin. A combination of V and A in the "priming"-technique did not lead to better conditions of any clinical relevance. Medium range non-depolarising muscle blockers, as they are available to the pediatric anesthetist nowadays, seem to compare favourable with the use of succinylcholin, which is to be considered an obsolete drug due to its various side effects.

Accumulation of acetone in blood during long-term anaesthesia with closed systems.

During closed system anaesthesia with isoflurane, patients with a preoperative increase in blood concentration of acetone (> 10 mg litre-1) had a significantly greater concentration of acetone than patients with an initial normal blood concentration of acetone (P < 0.01). Flushing the closed system with a high flow of fresh gas had no effect on the blood concentration of acetone. Using a large fresh gas flow, there was no increase in blood acetone concentration. Acetone concentrations of about 50 mg litre-1 cause problems such as nausea and vomiting in the postoperative period. These symptoms occurred more frequently after closed system anaesthesia.

[Humidification and heating of anesthetic gases during pediatric anesthesia using the Cicero Anesthesia Workstation]. / Klimatisierung anästhetischer Gase während Säuglingsnarkosen mit dem "Anästhesiearbeitsplatz CICERO".

A series of 52 infants underwent general or urological surgery; all were ventilated with the CICERO. Two different flows of fresh gas were used. In group I (n = 21) the fresh gas flow was set exactly at the level of the minute volume, representing a half-open, non-rebreathing system. In group II (n = 31) the fresh gas flow was adjusted to 10% of the required minute volume. Temperature and relative humidity of the inspired gas were measured continuously close to the tracheal tube. Anaesthesia was accomplished with 2 vol% isoflurane, 21-30 vol% oxygen in nitrous oxide. The results were compared with those achieved with our time-tested paediatric equipment, a SERVO 900D ventilator with a Fisher-Paykel humidifier (Group III, n = 35). Using a high fresh gas flow, no increase in relative humidity in the inspired gas could be detected. The values varied between 12% and 25% (group I). Reducing the flow of fresh gas as indicated above resulted in an increase in the relative humidity (group II). Over the evaluated period of 2 h, humidity increased slowly from an initial mean value of 20% to a maximum of something over 70%. Using the SERVO 900D ventilator combined with the Fisher-Paykel humidifier, humidity reached a value of greater 90% within 10 min after activation of the heated cascade. Humidity in the inspired gas should exceed 70% to avoid damage to infant airways. This will not be attained until after more than 2 h with unaided breathing systems, by when most operations performed on paediatric patients will already be over. Condensed water may aspirated by small infants. This potentially dangerous situation was only encountered in the CICERO circuit, and not in the system protected by the Fisher-Paykel cascade. Dry gases can result in thickened mucous and in obstruction of a small tracheal tube, which requires emergency reintubation. With artificial airways dry gases damage the ciliated epithelia of the trachea and cause loss of water and body heat. The temperature of the "cold" gases varied within a range of 21-33 degrees C and could not be adjusted by the anaesthetist. In the CICERO system, heating the gases at the valve only prevents mechanical failure caused by water condensation. In pediatric anaesthesia, variable heating and non-condensing humidity are essential. The dry and heated gases of the CICERO are not acceptable in the daily practice of paediatric anaesthesia.

[The evolution of carboxyhemoglobin during long-term closed-circuit anesthesia]. / Die Entwicklung von Carboxyhämoglobin während Langzeitnarkosen im geschlossenen Kreissystem.

In 40 patients who underwent protracted orthodontic operations, the accumulation of carboxyhemoglobin (COHb) in the blood was studied. Mechanical ventilation during anesthesia was carried out in a closed system (group I, n = 20). Patients in a control group received mechanical ventilation with a constant fresh gas flow of 6 l/min (group II, n = 20). During closed-system ventilation, a constant rise of COHb was observed. Smokers had much higher COHb values than nonsmokers at the beginning of and during anesthesia. The relative increase of COHb in a defined time period was of the same magnitude for smokers and nonsmokers. Critical values for carbon monoxide (CO) intoxication were not measured. The mean rise was 0.05 g/100 ml COHb over 6 h. Two female patients had COHb rises of 0.29 g/100 ml and 0.18 g/100 ml over the same period. During ventilation with a high flow of fresh gas, the COHb level decreased in all patients. In nonsmokers, the value approached the physiological range of 0.4% to 0.8% COHb. A marked fall of COHb could also be observed in smokers; however, normal physiological values were not reached. Patients with low COHb tolerance (anemia, severe coronary heart disease, peripheral vascular disease) or with increased endogenous CO production (pregnancy, newborns, hemolytic disease, porphyria cutanea) should not undergo protracted ventilation in a closed circle system.

[A case of central anticholinergic syndrome in pediatric anesthesia]. / Ein Fall von Zentral-Anticholinergischem Syndrom (ZAS) in der Kinderanaesthesie.

The central cholinergic syndrome developed in a 5 1/2-year-old child after premedication with midazolam and a short volatile anesthetic. Diagnosis was made more difficult because of a history of nephrotic syndrome, convulsions, relative acetylcholinesterase deficiency and chronic medication with a corticosteroid. Successful management of such cases depends on a through differential diagnosis before the institution of physostigmine therapy. Intensive postoperative monitoring is strongly recommended.

[A new instrument for blood pressure determination in neonatal care]. / Neues Blutdruckmessgerät für den Neonatal-Bereich.

A new instrument for measuring blood pressure by oscillometry conceived for neonates was tested in 30 children between 32.6 kg and 1200 g body weight (the emphasis being on infants) using sphygmanometric and invasive arterial measurements for comparison. High accuracy and good reproducibility of the individual measurements were found, the time required for measurement being short. The authors discuss the problems governing the sphygmanometric and oscillometric method.

[Technical improvements in the 900 D anesthetic servo-ventilator]. / Technische Verbesserungen am Narkose Servo-Ventilator 900 D.

Demonstrated is a Mapleson D (Kuhn) modification integrated into a Siemens Elema Servo-Ventilator 900 D as it is used in pediatric anesthesia. The advantage seems to be the better feeling on the bag while briefly ventilating a child in critical phases of anesthesia. The disadvantage is to be seen in the lack of gas monitors (pressure, volume, content) advised by the DGAI for longer periods of manual ventilation. The scavenging system has an akward appeal and last not least the additional manual system stalls with electric power failure.

[Measurement of end-expiratory carbon dioxide values in pediatric anesthesia]. / Die Messung des endexspiratorischen Kohlendioxid-Wertes in der Kinderanaesthesie.

This study dealt with two principles of the evaluation of end-expiratory CO2 in pediatric anaesthesia: detection of CO2-influenced infrared rays with a full stream analyzer attached to the tracheal tube; CO2 measurement with a side-stream analyzer connected to the breathing and ventilating system by a small tube. The linearity of the analyzers was tested with gas mixtures containing 3.0/5.0/7.0 vol% of CO2 cycling at an increasing rate. Additional mass-spectrometry has proven that the instruments are accurate within the clinical range of pediatric anesthesia. A maximal deviation of 8% develops when cycling rates increase to 40 per min. To detect quality differences in the analyzers, tangential constructions onto the CO2 curves plotted by the capnographs provided valuable quotients. Depending on the length of the tubing that feeds samples of respiratory gas into the side-stream analyzer, the CO2 curves were subject to sinus degradation with increasing respiratory rates. Capnography with full-stream analyzers depended on inspiratory zero CO2 content for reference purposes.