PubMed Health⌕ Search

Biomedical subjects

P Riedel

Publications and source records attributed to P Riedel.

11 recordsLinked to original sources
PubMed2006

A blinded, randomized, multicenter study of an intravenous Staphylococcus aureus immune globulin.

OBJECTIVES: Very low birth weight (VLBW) infants are vulnerable to nosocomial infections and subsequent morbidity; including infections caused by Staphylococcus aureus: 85% of nosocomial S. aureus infections are caused by capsular polysaccharide (CPS) types 5 and 8. Altastaph is a polyclonal investigational human immunoglobulin G (IgG) with high levels of opsonizing S. aureus CPS types 5 and 8 IgG. METHODS: A Phase 2 clinical trial to assess the safety and kinetics of Altastaph in VLBW infants. Neonates in this multicenter study were randomized to receive two identical 20 ml/kg i.v. infusions of either 0.45% NaCl placebo or 1000 mg Altastaph/kg. Each infant was followed for 28 days after the second infusion or until discharge. Serum S. aureus CPS types 5 and 8 IgG levels were measured preinfusion and at various times after each infusion. RESULTS: Of 206 neonates, 158 received both infusions. Adverse events were similar in the two treatment groups. Six subjects (3% in each group) discontinued owing to an adverse event. Geometric mean anti-type 5 IgG levels were 402 and 642 mcg/ml 1 day following infusion of the first (day 0) and Second (day 14) doses, respectively, in neonates < or =1000 g and slightly higher in neonates 1001 to 1500 g. Trough levels before second infusion were 188 mcg/ml. Type 8 IgG levels were similar. Geometric mean IgG levels among placebo recipients were consistently <2 and <5 mcg/ml for types 5 and 8 in both weight groups. Three episodes of S. aureus bacteremia occurred in each arm. CONCLUSIONS: Infusion of Altastaph in VLBW neonates resulted in high levels of specific S. aureus types 5 and 8 CPS IgG. The administration of this anti-staphylococcal hyperimmune globulin was well tolerated in this population.

Bacterial Capsules↗
PubMed2001

[Cavitation bubble formation during Erbium:YAG laser vitrectomy].

BACKGROUND: Clinical and experimental studies demonstrated the potential advantages of Erbium:YAG laser vitrectomy for posterior segment surgery. However, a detailed knowledge on the laser-tissue interaction is needed for an optimization of new ophthalmic applications. The aim of this experimental work was to investigate the cavitation bubble formation during Erbium:YAG laser vitrectomy and to find optimized laser parameters and the best geometry of the aspiration port of the microsurgical probe. MATERIALS AND METHODS: We investigated the formation of cavitation bubbles in water by high-speed photography. The output energy at the quartz tip reached up to 50 mJ and the laser pulse duration ranged from 50 to 300 microseconds. Various commercially available microsurgery probes were investigated regarding the extent of the cavitation bubbles. RESULTS: The threshold for laser-induced cavitation bubble formation was found to be 0.32 +/- 0.1 mJ for a laser pulse duration of 130 microseconds and a core diameter of 320 microns of the quartz fiber tip. The length of the cavitation bubbles increases with the laser pulse energy up to a length of 1.6 mm at a pulse energy of 10 mJ. In contrast, the size of the vapor bubbles decreases with an increase of the laser pulse duration. A slit-shaped aspiration port led to a 50% smaller volume of the cavitation bubble exiting the port compared with a circular aspiration port. CONCLUSIONS: The optimized laser parameters and microsurgery probe geometry may significantly decrease the risk of intraoperative ocular damages during Erbium:YAG laser vitrectomy.

Animals↗
PubMed2001

Erbium: yttrium-aluminum-garnet laser induced vapor bubbles as a function of the quartz fiber tip geometry.

BACKGROUND: The use of modern erbium: yttrium-aluminum-garnet (YAG) laser systems in opthalmic microsurgery requires a precise knowledge of the size and dynamics of the laser induced vapor bubbles. The aim of this work was to clarify the possibilities of controlling the vapor bubble shape and size by using an optimized fiber tip geometry for various ophthalmic applications with the erbium: YAG laser. METHODS: The mid-infrared radiation of free-running erbium: YAG laser was coupled optically into means of different low OH(-) quartz fiber tips to investigate the vapor bubble formation in water by high-speed photography. The core diameter of four fiber tips ranged from 200 up to 940 microm. Fourteen fiber tips were polished at an angle graduated from 10 degrees to 70 degrees over the full core diameter (seven fiber tips) and over the half core diameter (seven fiber tips). Three fiber tips were produced to have a curvature at the distal end with curvature radii of 160, 230, and 420 microm. RESULTS: The shape as well as the size of erbium: YAG laser induced vapor bubbles can be controlled systematically by using adequate fiber tip geometries. In detail, the used different angles and curvatures demonstrate that the propagation direction of the vapor bubbles can be estimated by optical modeling considering Snell's law and the Fresnel laws at a quartz-air boundary. Beside this, the size of a vapor bubble can be predetermined by choosing ideal fiber tip geometries to reduce or increase the radiant exposure at the distal end of the quartz fiber tip. CONCLUSIONS: The good possibility of controlling the shape and size of vapor bubbles offers a wider range of new applications, especially in ophthalmic microsurgery such as erbium YAG laser vitrectomy.

Equipment Design↗
PubMed2000

[Ticlopidine-associated thrombotic thrombocytopenic purpura (Morbus Moschcowitz)].

ANAMNESIS AND CLINICAL FINDINGS: A 75-year-old woman with a history of recurrent ischemic cerebral events was admitted with acute unspecific neurological symptoms and fever. EXAMINATION: Intracerebral hemorrhage due to hypertension and antithrombotic therapy with ticlopidine was ruled out with cranial computed tomography. Laboratory findings on admission included thrombocytopenia (12/nl), renal insufficiency (serum creatinine 1.6 mg/dl) and LDH elevation (1,218 U/l). The hemoglobin on admission was normal. THERAPY AND CLINICAL COURSE: In the presence of rapidly declining hemoglobin values and fragmentation of red cells thrombotic-thrombocytopenic purpura (TTP) was diagnosed and the patient received fresh frozen plasma. Shortly after the plasma infusion the patient's condition deteriorated rapidly showing clinical signs of an allergic shock. In the sequel of 24 to 48 hours the patient developed renal failure, severe anemia and the thrombocyte count fell to 5/nl. The patient was mechanically ventilated during the next 48 hours and needed intravenous catecholamines. Even after restoration of spontaneous respiration and cessation of pharmacological sedation the patient remained comatose. Cranial computed tomography on the fourth day after admission showed multiple infarction syndrome. The patient died on the ninth day after admission in status epilepticus which could not be stopped with pharmacological means. CONCLUSIONS: The combination of neurological symptoms, thrombocytopenia, fever, renal failure and hemolytic anemia in a patient taking ticlopidine points to a diagnosis of TTP. The high mortality of TTP can probably only be reduced by early plasmapheresis.

Aged↗
PubMed2000

[Erbium:YAG laser vitrectomy: temperature measurements in different replacement materials].

BACKGROUND: The erbium:YAG laser has the potential of being used routinely for vitrectomy because of the excellent quality of liquefying vitreous structures and the low vacuum forces required. However, the use of silicone oil and perfluorocarbon may lead to unwanted temperature increases in the microsurgery probe. The aim of this work was to investigate this side effect. MATERIALS AND METHODS: Different replacement materials such as water, methocel, silicone oil and perfluorocarbon were used in a simple eye model. The temperature increase during laser application was measured by means of thermocouples. The maximum temperature increase and time decay were derived with and without aspiration from these time-resolved measurements. The average power at the distal end of the microsurgery probe was chosen to be 1 W. RESULTS: The temperature increase with aspiration in water was found to be significantly smaller than all other replacement materials. Interruption of aspiration leads to a critical temperature increase of approximately 14 K; however, this increase occurred very slowly (decay time 200 s). A comparable result could be observed for methocel, which was used to simulate condensed vitreous structures. In perfluorocarbon and silicone oil we measured a far higher increase in temperature of up to 130 K within a few seconds. Furthermore, small remnants of carbonized materials can be seen in the microsurgery probe after laser application. CONCLUSIONS: The temperature increase during erbium:YAG laser vitrectomy in water can be considered to be harmless for other intraocular structures. However, insufficient aspiration or increased vitreous condensation leads to increased temperature in the microsurgery probe. Our results demonstrate that the use of erbium:YAG laser vitrectomy in materials such as silicone oil or perfluorocarbons is contraindicated.

Contraindications↗
PubMed2000

[Motion artifacts in the vitreous body during vitrectomy].

BACKGROUND: Movements and vibrations of intraocular structures can be observed during vitrectomy with mechanical cutting systems. We experimentally compared these intraocular motion artifacts between mechanical and erbium:YAG laser vitrectomy. MATERIAL AND METHODS: The intraocular structures were reliably simulated by a 0.9-mm-wide foil (thickness 10 microns) in a water-filled cuvette. The movements caused by commercial mechanical cutter systems were compared with vibration induced by means of laser surgery probes (laser pulse energy 20 mJ). Laser triangulation was used to measure the movement amplitudes at various cutting rates of 2, 5, and 10 Hz and a constant suction force of 50 mmHg. RESULTS: At all cutting rates the amplitude with the laser was less than that with the mechanical system. The ratio of the maximal amplitude between laser surgery probes (AL) and mechanical cutter system (AM) was AL/AM = 0.29 at 10 Hz, AL/AM = 0.33 at 5 Hz, and AL/AM = 0.45 at 2 Hz. CONCLUSION: The reduced intraocular movements with erbium:YAG laser vitrectomy constitutes a potential advantage for the nonpulsatile vitrectomy.

Erbium↗
PubMed1987

[Decisions of the physician in a psychoanalytic interview. Patient characteristics in the initial psychodiagnostic interview].

The focus of our investigation is the question which criteria of the first psychodiagnostic dialogue are associated with the decision of a physician to make a psychoanalytic interview. 51 patients have been investigated who had contacted the out-patient department of the Psychosomatic Hospital at the Central Institute of Mental Health in Mannheim. Patients who have been provided with a psychoanalytic interview by the therapist have been estimated as having a greater motivation for psychotherapy and they seemed more likely to consider their complaints as being psychologically caused. Younger patients have been regarded as having a greater motivation for psychotherapy than older ones and they could more likely attribute their complaints to psychologic causes, especially if they are females and belong to the middle social stratum. Furthermore, those patients who had been decided by the therapist to undergo a psychoanalytic interview more than the other group of patients showed a pattern of values which was similar to that of the therapists.

Adult↗
PubMed1984

[The Mannheim Cohort Project--prevalence of psychogenic diseases in cities].

For the purpose of our research project the term 'psychogenetic disorders' covers psychoneuroses , character neuroses in a broader sense, and functional-vegetative as well as psychosomatic affections. So far information concerning basic descriptive-epidemiological data, especially the frequency of occurrence and the dependence upon demographic variables of the above mentioned disorders, is insufficient and controversial. Even less satisfactory is our information on the progress of these disorders. The specific difficulty with the diagnostic apperception of these disorders in particular requires field research within the entire population. Only by means of such a very expensive procedure can valid information on the true prevalence or incidence of the above mentioned disorders be obtained. Moreover, for a follow-up design each test subject must be examined several times by highly qualified experts, each examination requiring his personal presence. The "Mannheimer Kohortenprojekt" involves six hundred test subjects, two hundred each born in 1935, 1945, and 1955, selected at random from the 'normal' general population. They were examined with the aid of a structured interview schedule oriented on psychoanalytic principles and with other instruments (lists of complaints, inventories of life events, FPI-tests, etc.). Results from the first three-year investigation period include: Out of the total of six hundred test subjects twenty-five per cent are "cases". Women are significantly in the majority. Apparent is an obvious connection between different types of complaints and the social class of the test subject. Identified disorders show correlations with life events on the one hand and with early childhood disturbances on the other.

Adult↗