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Biomedical subjects

P Heeg

Publications and source records attributed to P Heeg.

At least 19 recordsLinked to original sources
PubMed2006

Absorbed dose to water determination with ionization chamber dosimetry and calorimetry in restricted neutron, photon, proton and heavy-ion radiation fields.

Absolute dose measurements with a transportable water calorimeter and ionization chambers were performed at a water depth of 20 mm in four different types of radiation fields, for a collimated (60)Co photon beam, for a collimated neutron beam with a fluence-averaged mean energy of 5.25 MeV, for collimated proton beams with mean energies of 36 MeV and 182 MeV at the measuring position, and for a (12)C ion beam in a scanned mode with an energy per atomic mass of 430 MeV u(-1). The ionization chambers actually used were calibrated in units of air kerma in the photon reference field of the PTB and in units of absorbed dose to water for a Farmer-type chamber at GSI. The absorbed dose to water inferred from calorimetry was compared with the dose derived from ionometry by applying the radiation-field-dependent parameters. For neutrons, the quantities of the ICRU Report 45, for protons the quantities of the ICRU Report 59 and for the (12)C ion beam, the recommended values of the International Atomic Energy Agency (IAEA) protocol (TRS 398) were applied. The mean values of the absolute absorbed dose to water obtained with these two independent methods agreed within the standard uncertainty (k = 1) of 1.8% for calorimetry and of 3.0% for ionometry for all types and energies of the radiation beams used in this comparison.

Calorimetry↗
PubMed2006

Fatal multidrug-resistant Acinetobacter baumannii sepsis in a patient with travel history and recent onset of systemic lupus erythematosus: a case report.

Severe infections are a common cause of death in patients suffering from systemic lupus erythematosus (SLE). We here report on a fatal multidrug-resistant Acinetobacter baumannii sepsis in a patient with newly diagnosed SLE, who had to be treated with immunosuppressants due to lupus nephritis. Detailed analysis of the patient's history revealed that colonisation probably had occurred during a recent hospitalisation of the patient in the Mediterranean region. E-test analysis indicated that resistance to carbapenems was mediated by a plasmid-encoded metallo-beta-lactamase. We conclude that travel history including previously visited health care facilities always should be carefully considered for decisions on anti-infective therapy, as travel activities increasingly facilitate spread of antimicrobial resistances.

Acinetobacter Infections↗
PubMed2006

Acute musculoskeletal infection: comparison of different methods for intraoperative bacterial identification.

PURPOSE OF THE STUDY: Various techniques are used for detection of pathogens in musculoskeletal infection. These methods differ with respect to reliability and ease of handling. A prospective study was performed to evaluate the efficacy of three intraoperative techniques. MATERIAL AND METHODS: In 20 cases (18 patients) with clinically confirmed acute musculoskeletal infections, intraoperative collected swab samples, tissue samples and fluid samples injected into standard blood culture vials were used for microbiological diagnosis. Identification of bacteria, time necessary for detection and ease of handling during surgery was evaluated. RESULTS: In 19 cases bacterial growth was demonstrated using either intraoperative swabs or blood culture technique (95% sensitivity), whereas 18 tissue biopsies were positive (90% sensitivity. 27 bacterial species were isolated. In 18 instances for the swab technique, 14 instances for the tissue biopsy and 4 operations for the blood culture vials, ease of handling was rated as excellent. DISCUSSION: The study demonstrated differences between the three tested methods with respect to ease of handling. With respect to the number of detected organisms and time for their detection there are no significant differences. These last findings are in contrast to of the results of other authors. The reason for this could be that during operative dissection an accurate and specific collection of specimens from the acute deep infected soft tissues and bones independent from the type of surgical procedure is possible. Therefore, even with the swab method a high amount of microorganisms can be recovered. Especially for intraarticular infections, fluid samples injected into standard blood vials is a practical method for the surgeon. In acute musculoskeletal infections other than joint infections, there is less benefit for the blood culture vials. CONCLUSION: Intraoperative swab technique yields valid results comparable to other techniques and is an accurate technique for detection of pathogens from acute musculoskeletal infections. Key words: implant, infections, bacteriological techniques, comparative study.

Acute Disease↗
PubMed2005

Surgical hand disinfection with a propanol-based hand rub: equivalence of shorter application times.

The aim of this study was to determine the efficacy of a propanol-based hand rub at application times shorter than 3 min. The bacterial pre-value was obtained from the finger tips (prEN 12791). Subjects treated their hands with the reference procedure (n-propanol, 60%) for 3 min or the product (crossover design). Sterillium was applied for 3, 2, 1.5 and 1 min. Four other preparations were tested for 1 min. Post-values (immediate effect) were taken from one hand, and the other hand was gloved for 3h. After the gloves were removed, the second post-value was taken (sustained effect). Sterillium was more effective than the reference procedure at 3, 2 and 1.5 min (immediate and sustained effect). The immediate effect after 1 min was significantly lower [mean log(10) reduction factor (RF): 1.91+/-0.90 vs. 2.52+/-0.95; P=0.001], whereas the sustained effect was not (mean RF: 1.81+/-1.06 vs. 2.05+/-1.14; P=0.204). All other preparations failed the efficacy requirement at 1 min for both the immediate and sustained effect. Using 2 x 3 mL Sterillium for a total of 1.5 min for surgical hand disinfection was at least as effective as the 3-min reference disinfection.

1-Propanol↗
PubMed2004

Reprocessing endoscopes: national recommendations with a special emphasis on cleaning--the German perspective.

Transmission of pathogens through endoscopes or endoscopic procedures has been documented frequently, although reliable data on the incidence of endoscope-associated infections do not exist. In order to control such infections as well as to ensure adequate quality management in endoscopy, the German Robert Koch Institute has produced recommendations for hygienic processing of flexible endoscopes and accessory devices. Reprocessing using a washer disinfector is explicitly preferred to manual procedures. Control measures are focused on microbiological sampling and limiting values have been defined for rinsing fluids taken from the channels of the scopes. Although the guideline leaves a number of questions open, e.g. test methods to control the efficacy of the cleaning process. It helps to establish quality management in the field of endoscopy and to improve the level of safety both for patients and staff.

Disinfection↗
PubMed2004

Metallo-beta-lactamase expressing multi-resistant Acinetobacter baumannii transmitted in the operation area.

Outbreaks of Acinetobacter baumannii demonstrating multiple antibiotic resistance, including meropenem resistance, have been described as severe therapeutic problems. Here we describe a monoclonal outbreak of infection and colonization with multidrug-resistant A. baumannii over a two-month period. Resistance to meropenem was mediated by expression of a metallo-beta-lactamase enzyme. Four of 14 patients showed clinical signs of infection and two died. Contamination of the environment, water, or instruments were excluded as causes of the outbreak. All patients, except one, underwent surgery in a specific operation theatre where surgery of contamination class IV (infected, dirty) was performed. Although individual surgeon error was eliminated, analyses of the patients' histories suggested that bacterial transmission had occurred during surgery. Five patients showed signs of A. baumannii infection and two of these patients suffered from large abdominal wounds infected with a high density of A. baumannii requiring repeated revisions. Presumably, these revisions favoured the transmission of A. baumannii, which is remarkably resistant to various environmental stresses including soaps, disinfectants and dry conditions. No case of meropenem-resistant A. baumannii had been observed in the hospital before the outbreak. Interestingly, the resistant bacteria appear to have been imported by a patient returning from West Africa. This indicates that, similar to MRSA, multiresistant A. baumannii may be introduced by patients from foreign hospitals. The outbreak was stopped in the following months by reinforcing standard procedures and by taking all necessary precautions such as patient isolation, and finally only one new case was detected.

Acinetobacter Infections↗
PubMed2004

Treatment planning for carbon ion radiotherapy in Germany: review of clinical trials and treatment planning studies.

The GSI carbon ion radiotherapy facility established the first completely active beam shaping system for heavy ions, using energy variation on the synchrotron and pencil beam scanning. The introduction of an active beam shaping system for carbon ions has considerable impact on the design of the treatment planning system (TPS). The TPS has to account for the capability of the beam delivery and the biological modelling, which is needed to calculate the RBE for the resulting varying depth dose modulation. The TPS used in clinical routine with carbon ions is described and its use in treatment planning studies are outlined. A clinical trial with carbon ion therapy as primary therapy for chordoma and chondrosarcoma of the base of skull has been completed in 2001. Currently, carbon ion therapy as a boost treatment together with conventional conformal photon therapy or IMRT is under investigation in clinical trials for adenoid cystic carcinoma, chordoma and chondrosarcoma of the cervical spine and sacrococcygeal chordoma. Treatment planning studies comparing carbon ion therapy with IMRT, using optimization of combination therapy, and optimization of beam-line design have already been completed. Analysis of uncertainties in treatment planning has been started with the investigation of range uncertainties stemming from CT imaging. Uncertainties coming from the beam delivery play only a minor role. An attempt to asses the uncertainties introduced in treatment plans by the biological modelling, was done, using phantom verification of calculated cell survival levels. The clinical trials and planning studies are of special importance for the upcoming new clinical ion facility of the Heidelberg university hospital.

Carbon↗
PubMed2004

A calibration procedure for beam monitors in a scanned beam of heavy charged particles.

An international code of practice (CoP) for dosimetry based on standards of absorbed dose to water has recently been published by the IAEA [Technical Report Series No. 398, 2000] (TRS-398). This new CoP includes procedures for proton and heavy ion beams as well as all other beam qualities. In particular it defines reference conditions to which dose measurements should refer to. For proton and ion beams these conditions include dose measurements in the center of all possible modulated Bragg peaks. The recommended reference conditions in general are used also for the calibration of beam monitors. For a dynamic beam delivery system using beam scanning in combination with energy variation, like, e.g., at the German carbon ion radiotherapy facility, this calibration procedure is not appropriate. We have independently developed a different calibration procedure. Similar to the IAEA CoP this procedure is based on the measurement of absorbed dose to water. This is translated in terms of fluence which finally results in an energy-dependent calibration of the beam monitor in units of particle number per monitor unit, which is unique for all treatment fields. In contrast to the IAEA CoP, the reference depth is chosen to be very small. The procedure enables an accurate and reliable determination of calibration factors. In a second step, the calibration is verified by measurements of absorbed dose in various modulated Bragg peaks by comparing measured against calculated doses. The agreement between measured and calculated doses is usually better than 1% for homogeneous fields and the mean deviation for more inhomogeneous treatment fields, as they are used for patient treatments, is within 3%. It is proposed that the CoP in general, and in particular the IAEA TRS-398 should include explicit recommendations for the beam monitor calibration. These recommendations should then distinguish between systems using static and dynamic beams.

Algorithms↗
PubMed2002

Specific hygiene issues relating to reprocessing and reuse of single-use devices for laparoscopic surgery.

OBJECTIVE: To determine whether reprocessed single-use devices (SUD) would (1) meet regulatory standards for sterility, and (2) meet the same material standards as new devices or if they pose an infection risk to other patients. DESIGN: The study included in the first stage single-use laparoscopic dissection devices and in the second stage a variety of clinically used and reprocessed SUDs. The suitability of these devices for cleaning, disinfection, and sterilization was examined. METHODS: Testing of cleanability was conducted on devices contaminated with radioactively labeled blood. Instruments were cleaned using hospital recommended practices. Gamma counts/second were determined before and after cleaning to localize contaminants, which were additionally visualized using light and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used to quantify contamination elements on the materials tested. Residual bioburden testing on instruments contaminated with microorganisms suspended in blood prior to reprocessing was carried out to establish the efficacy of disinfection and sterilization. RESULTS: During the first stage of the study all devices remained contaminated after cleaning, but were effectively disinfected. Sterilization could not eliminate the challenge microorganisms completely. The findings during the second stage--examination of clinically used devices--were as follows: 11% of the sterile packages were damaged; 33% of the devices were incomplete and parts were missing; 54% did not meet the criteria for functionality; light microscopy, SEM, and XPS showed contamination on the outside and inside of all devices. Of the tested SUDs, 40% remained unsterile following resterilization. CONCLUSIONS: None of the reprocessed SUDs were effectively cleaned or sterilized. This may provide an opportunity for survival and growth of non-resistant or nosocomial organisms and viruses. The use of such inadequately reprocessed SUDs increases the risk for the patient, and can lead to nosocomial infection and to legal consequences for the health care facility.

Blood↗
PubMed2002

Influence of acid-citrate-dextrose anticoagulant on blood quality in retransfusion systems after total knee arthroplasty.

The influence of acid-citrate-dextrose (ACD) anticoagulant on the blood quality was assessed in this prospective, randomized, controlled study. The clinical consequences with regard to retransfusion of drainage blood following total knee arthroplasty were evaluated. After total knee arthroplasty, retransfusion was performed utilizing a "SureTrans" retransfusion system in 81 patients. In 42 of them, blood was collected adding an ACD anticoagulant (group A), while in the remaining 39 patients blood was collected without any additives (group B). Blood losses were retransfused over a 6-h period after attaching the retransfusion system to the patient of either group. Blood samples of the 6-h blood collection were taken and analysed for several blood quality parameters. Significant differences were found in the platelet count (61,200+/-16,700 microl(-1) in group A versus 70,100+/-21,600 microl(-1) in group B, p=0.042), the lactate concentration (4.09+/-0.86 mmol/l vs 4.82+/-0.83 mmol/l, p<0.001), the pH (6.96+/-0.10 vs 7.18+/-0.06, p<0.001), as well as the protein content (5.44+/-0.57 g/dl vs 5.85+/-0.43 g/dl, p<0.001). These observed significant differences were, however, of no clinical relevance to the patients' treatment. Hemoglobin concentration, hematocrit, mean corpuscular volume (MCV), erythrocyte count, leukocyte count, concentration of free hemoglobin in the blood plasma (fHb), potassium concentration, lactate dehydrogenase (LDH), serotonin concentration, triglyceride concentration, free fatty acid concentration, and interleukin-6 concentration did not differ significantly. This study indicates that the blood quality in retransfusion systems is not substantially influenced by adding ACD anticoagulant.

Aged↗
PubMed2001

Time-related changes of collected shed blood in autologous retransfusion after total knee arthroplasty.

A prospective study was done to determine the changes in blood quality parameters of collected drainage blood in retransfusion systems at 6 and 12 h after surgery to verify whether the blood was still suitable for retransfusion purposes for an additional 6 postoperative hours beyond the so far accepted first 6-h time window after surgery. Eighty-one patients received retransfusion within the first 6 h immediately following total knee arthroplasty. Additionally, drainage blood was collected for another 6 h using the same retransfusion system. Samples for laboratory analysis were taken from both the first and second 6-h blood collection interval. Hemoglobin values increased from 9.6 to 10.4 g dl(-1) (p = 0.021). Platelet counts increased from 65,500 to 80,900 microl(-1) (p < 0.001). Leukocyte counts increased from 5,550 to 8,190 1(-1) (p < 0.001). Lactate dehydrogenase (672 U l(-1) during the first vs 651 U l(-1) during the second collection period) and free hemoglobin (71.7 mg dl(-1) vs 67.0 mg dl(-1)) did not change significantly. The potassium concentration decreased slightly from 4.33 to 4.20 mg dl(-1) (p = 0.002). The lactate concentration increased from 4.44 to 7.21 mg dl(-1) (p < 0.001). The pH decreased from 7.07 to 6.94 (p < 0.001). Interleukin-6 concentration increased from 6,500 to 46,500 ng l(-1) (p < 0.001). In this study, we found no relevant difference in most of the drainage blood quality parameters between the first 6-h collection period and the second 6-h collection with regard to its suitability for autologous retransfusion except higher interleukin-6 levels. Due to the higher interleukin concentration, a possible increase in febrile reactions should be taken into account during retransfusion.

Aged↗
PubMed2001

Does hand care ruin hand disinfection?

Hand washing and hand disinfection put considerable stress on the skin thus requiring specific hand care. It is important however that the care products do not impair the effect of hand disinfectants. We therefore investigated the interaction of two hand care products (oil-in-water and water-in-oil emulsions) on the microbicidal efficacy of different alcoholic hand-rubs, using the contamination model described in EN 1500. The mean log10-reduction factors for three hand-rubs varied between 4.03 and 4.22 compared with 3.76 and 4.43 for six possible combinations of hand-rubs and hand care products applied immediately prior to disinfection. Differences between reduction factors achieved with hand-rubs alone and in combination with hand care were not significant. Repeated application of care products with subsequent hand disinfection also did not result in significantly lower reduction factors than achieved with hand disinfection alone. Our data suggest that administration of selected products for hand care does not necessarily impair hand disinfection and is therefore recommended for occupational health as well as for infection control reasons.

1-Propanol↗
PubMed2001

Increased interleukin-6 in collected drainage blood after total knee arthroplasty: an association with febrile reactions during retransfusion.

We determined interleukin-6 (IL-6) concentrations in collected shed drainage blood intended for retransfusion in a prospective study in 81 patients after total knee replacement. We found large increases in IL-6 levels, averaging 6.5 (SD 3.9) ng/mL, in shed blood collected in the first 6 postoperative hours. 3 patients had febrile reactions after collected blood was retransfused. The IL-6 levels in the drainage blood of these patients were very high (9.6-13.4 ng/mL). In the blood collected after 6 hours, IL-6 concentrations increased to 47 (SD 33) ng/mL (p < 0.001). These results suggest a relation between increased interleukin-6 concentrations in shed drainage blood and the occurrence of febrile reactions after retransfusion of such blood.

Aged↗
PubMed2001

Decontaminated single-use devices: an oxymoron that may be placing patients at risk for cross-contamination.

OBJECTIVE: To determine whether reprocessed single-use devices would meet regulatory standards for sterility and meet the same materials standards as a new device. DESIGN: The study included single-use and reusable biopsy forceps and papillotomes and a reusable stone retrieval basket. The suitability of these devices for cleaning and disinfection or sterilization was examined. METHODS: Testing of cleanability was conducted on devices contaminated with technetium 99-radiolabeled human blood. Instruments were cleaned using hospital recommended practices for manual cleaning. Gamma counts per second were determined before and after cleaning to localize contaminants, which were additionally visualized using light and scanning electron microscopy. X-ray photoelectron spectroscopy was used to quantify contamination elements on the materials tested. Residual bioburden testing on instruments contaminated with microorganisms suspended in coagulable sheep blood was carried out to establish the efficacy of disinfection and sterilization. RESULTS: All devices remained contaminated after cleaning, but single-use devices and the stone basket tended to be more heavily contaminated than reusable forceps and papillotomes. Cleaning procedures facilitated distribution of contaminants further into the lumens of the disposable forceps. Decreased concentrations of silicon and increased concentrations of carbon and nitrogen suggested that layers of silicon lubricant had been removed and contaminants were organic material. Reusable devices were effectively disinfected, but single-use devices were not. Sterilization could not eliminate the challenge microorganisms completely. CONCLUSIONS: None of the reprocessed single-use instruments were effectively cleaned, disinfected, or sterilized. This condition may provide an opportunity for the viability of nonresistant or nosocomial organisms and viruses. Additionally, reprocessing procedures may result in material destruction of fragile devices. Cost-saving initiatives that have inspired reprocessing of single-use devices, despite the absence of data establishing the efficacy of decontamination and the durability of materials throughout reprocessing, should be pushed into the background.

Blood-Borne Pathogens↗
PubMed2001

A method for determining the alignment accuracy of the treatment table axis at an isocentric irradiation facility.

At an isocentric irradiation facility, the rotation axis of the treatment table has to be accurately aligned in vertical orientation to the isocentre, which is usually marked by three perpendicular laser planes. In particular, high precision radiotherapy techniques, such as radiosurgery or intensity modulated radiotherapy, require a higher alignment accuracy of the table axis than routinely specified by the manufacturers. A simple and efficient method is presented to measure the direction and the size of the displacement of the table axis from the isocentre as marked by the lasers. In addition, the inclination of the table axis against the vertical direction can be determined. The measured displacement and inclination provide the required data to correct for possible misalignments of the treatment table axis and to maintain its alignment. Measurements were performed over a period of two years for a treatment table located at the German heavy ion therapy facility. The mean radial distance between the table axis and the isocentre was found to be 0.25 +/- 0.25 mm. The mean inclination of the table axis in the XZ- and YZ-planes was measured to be -0.03 +/- 0.02 degrees and -0.04 +/- 0.01 degrees, respectively. The measurements demonstrate the good alignment of the treatment table over the analysed time period. The described method can be applied to any isocentric irradiation facility, especially including isocentric linear accelerators used for radiosurgery or other high precision irradiation techniques.

Algorithms↗
PubMed2000

[Pilot study of disinfection of optical instruments in otorhinolaryngology].

There is undoubtedly a need for a safe disinfection method of optical instruments used by ENT specialists. So far, a standard method that sufficiently covers the risk of infection for patients and medical staff alike while serving the need of practicability in daily routine has not been established. Therefore, in the ENT departments of the hospitals of Mannheim, Kaiserslautern, and Tübingen, studies on the disinfection of rigid optical instruments without working channel were performed between February 1999 and May 1999. Instruments were wiped either with an aldehyde or alcohol (ethanol 80%) and germs were detected by quantitative swab cultures. As discussed in the article, disinfection with ethanol proved to be at least equally efficient if not better than disinfection with aldehyde. Therefore, it fully serves the requirements of a safe method for disinfecting optical instruments without working channels.

Aldehydes↗
PubMed2000

Subcutaneous infusion anesthesia with diluted mixtures of prilocain and ropivacain.

BACKGROUND: Local anesthesia often suffices for surgery on the outside of the body. In recent years, it has been found that such local anesthesia can be adequately carried out using large amounts of highly diluted anesthetic solutions. METHODS: Using one or more common infusomats, we injected mixed anesthetic solutions slowly, painlessly, paravenously, and automatically via subcutaneous infusion anesthesia (SIA) into the subcutaneous layer in a large group of patients scheduled for surgery. The local anesthetics used were prilocaine and ropivacaine (Xylonest and Naropin); these were diluted with original Ringer's solution with epinephrine (1: 1,000,000) in 500-ml bottles. The concentration of the mixture varied between 0.3% and 0.08% depending on the requirements of surgery. The needles used ranged from 30-gauge to 20-gauge needles, with a length of 1.5-10 cm. The speed of injection varied between 30 ml/h and 1500 ml/h, depending on the location, the requirements of the surgery and the needle size. Volumes usually ranged from 2 ml to 600 ml depending on the concentrations used. The maximum dose was approximately 4 mg/kg prilocaine and 2 mg/kg ropivacaine. PATIENTS: We used this technique in preparing for 5020 major and minor skin operations in 3270 patients ranging in age from 0.5 years to 95 years (mean age 54 years). Microbiological tests of the infusion system were carried out. Patients were asked about their pain during anesthesia, operation, and postoperatively. RESULTS: There were no complications from local anesthesia. The technique proved safe and comfortable even for children and very sensitive patients. The median duration of postoperative anesthesia was 5 h (maximum 23 h). Choosing the concentration, the needle, the needle position, the flow rate, and the volume requires some experience.

Adult↗