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Biomedical subjects

P Geiger

Publications and source records attributed to P Geiger.

At least 19 recordsLinked to original sources
PubMed2005

[Is a blockade of the lateral cutaneous nerve of the thigh an alternative to the classical femoral nerve blockade for knee joint arthroscopy? A randomised controlled study].

BACKGROUND: Gaps in the distribution area of the lateral femoral cutaneous nerve (LFCN) are assumed to be the reason for pain caused by a thigh tourniquet when performing a femoral nerve (FN) block according to Winnie. The aim of the study was to evaluate if a direct single blockade of the LFCN in patients undergoing knee surgery resulted in a better tolerance to the tourniquet with equally good analgesic quality during surgery. METHODS: A total of 40 patients undergoing knee arthroscopy received a proximal blockade of the sciatic nerve and randomly either an FN or an LFCN block. Practicability, onset time, quality of sensory and motor block, and clinical effectiveness during tourniquet and surgery were assessed. RESULTS: Stimulation time was significantly longer in the LFCN than in the FN group. Quality of sensory and motor block was worse in the LFCN than the NF group. Of the LFCN patients 65% indicated troublesome paraesthesia or pain when a tourniquet was placed, compared to 35% of the FN patients. Of the LFCN patients 50% had pain during cutaneous incision, compared to none of the FN group. During the course of surgery, 70% of the LFCN patients needed supplemental systemic analgesia, but this was required by only 30% of the FN group. CONCLUSION: An LFCN block is not a suitable alternative to an FN block for regional anaesthesia. For patients with contraindications for an FN block according to Winnie (e.g. vessel surgery in the groin) other more effective methods are available.

Adult↗
PubMed2004

Non-cross-bridge calcium-dependent stiffness in frog muscle fibers.

At the end of the force transient elicited by a fast stretch applied to an activated frog muscle fiber, the force settles to a steady level exceeding the isometric level preceding the stretch. We showed previously that this excess of tension, referred to as "static tension," is due to the elongation of some elastic sarcomere structure, outside the cross bridges. The stiffness of this structure, "static stiffness," increased upon stimulation following a time course well distinct from tension and roughly similar to intracellular Ca(2+) concentration. In the experiments reported here, we investigated the possible role of Ca(2+) in static stiffness by comparing static stiffness measurements in the presence of Ca(2+) release inhibitors (D600, Dantrolene, (2)H(2)O) and cross-bridge formation inhibitors [2,3-butanedione monoxime (BDM), hypertonicity]. Both series of agents inhibited tension; however, only D600, Dantrolene, and (2)H(2)O decreased at the same time static stiffness, whereas BDM and hypertonicity left static stiffness unaltered. These results indicate that Ca(2+), in addition to promoting cross-bridge formation, increases the stiffness of an (unidentified) elastic structure of the sarcomere. This stiffness increase may help in maintaining the sarcomere length uniformity under conditions of instability.

Animals↗
PubMed1999

Low-density lipoprotein susceptibility to oxidation and cytotoxicity to endothelium in sickle cell anemia.

Patients with sickle-cell anemia exhibit pro-oxidative metabolic perturbations. We hypothesize that because of chronic oxidative stress, plasma low-density lipoprotein (LDL) from patients with sickle-cell anemia is more susceptible to oxidation. To test this hypothesis, LDL susceptibility to copper-mediated oxidation was measured in 24 patients with sickle-cell anemia and 48 control subjects. Sickle-cell LDL was more susceptible to oxidation than control LDL, measured by a 22% shorter mean lag time between LDL exposure to CuSO4 and conjugated diene formation (97 vs 124 minutes; P = .023). LDL vitamin E, iron, heme, and cholesterol ester hydroperoxide (CEOOH) levels were also measured. LDL vitamin E levels were significantly lower in patients with sickle-cell anemia compared with control subjects (1.8 vs 2.9 mol/mol LDL; P = .025), but there was no correlation with lag time. Pro-oxidant heme and iron levels were the same in sickle-cell and control LDL. LDL CEOOHs were not significantly different in sickle and control LDL (3.1 vs 1.2 mmol/mol of LDL unesterified cholesterol, P = .15), but LDL CEOOH levels were inversely correlated with lag times in patients with sickle-cell anemia (r2 = 0.38; P = .018). The cytotoxicity of partially oxidized LDL to porcine aortic endothelial cells was inversely correlated with lag times (r2 = 0.48; P = .001). These preliminary data suggest that increased LDL susceptibility to oxidation could be a marker of oxidant stress and vasculopathy in patients with sickle-cell anemia.

Adolescent↗
PubMed1997

Active form of Pseudomonas mevalonii 3-hydroxy-3-methylglutaryl coenzyme A reductase.

Based on multiple gel permeation chromatographic experiments, we report a Stokes radius of 59.7 A for Pseudomonas mevalonii 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.88) and its His381Asn, His381Gln, and His381Lys mutant enzymes. Comparison of this Stokes radius with the radius calculated from the crystal structure indicated that the active form of P. mevalonii HMG-CoA reductase was a hexamer and not a dimer as previously thought. The Stokes radius, an S26,w of 11.0, and an estimated V of 0.723 were used in the Svedberg equation to calculate an anhydrous molecular mass of 270,084 Da for P. mevalonii HMG-CoA reductase (monomer mass 45,538 Da), consistent with the enzyme being a hexamer in solution. The Stokes radii of all standard proteins examined correlated with the inverse error function complement of their partition coefficient, Kd. Kd did not correlate with logarithm of the standard protein's molecular weight. Eight nonstandard proteins had Stokes radii that matched their crystallographic radii of longest axis. This indicated that the frozen conformation of a protein in its crystal form can dictate restraints on its shape in solution.

Chromatography, Gel↗
PubMed1997

[EMLA for anesthesia of puncture sites for large lumen indwelling venous catheters for autologous plasma and erythrocyte concentrate donation].

OBJECTIVE: The analgetic effect of EMLA-Creme (Lidocaine-Prilocaine-Cream) was studied in 52 patients undergoing preoperative autologous blood and/or plasma donation. METHOD: 95 venous punctures were performed with a 18 G or 16 G cannula. Puncture pain was estimated by the patients using a visual analog painscore (VAS 0-100). The data were evaluated regarding reaction time, puncture spot and cannula diameter. RESULTS: Within 15 minutes we find a clear reduction of puncture pain. The diameter of the cannula does not correlate with the painscore. Puncture of hand-back veins seems to be more painful than cubital vein puncture. CONCLUSION: The application of EMLA-Creme results in an effective analgesia for venous puncture. 37% of our patients were punctured without any pain and 67% felt a tolerable pain (VAS: 0-10).

Anesthetics, Local↗
PubMed1996

[Preoperative risk assessment of children with Duchenne muscular dystrophy and relevance for anesthesia and intra- and postoperative course].

BACKGROUND: Patients suffering from muscle disorders have an elevated anesthetic risk, i.e. to develop malignant hyperthermia or rhabdomyolysis. In addition serious cardial and pulmonal complications are imminent during anesthesia for surgery. PATIENTS AND METHODS: We investigated retrospectively the preoperative risk factors of 81 Duchenne patients undergoing 101 anesthesia (79 for muscle releasement operations and 23 for spine surgery) and the relation to possible complications due to the anesthesia and the intra- and postoperative course. RESULTS AND DISCUSSION: 83% of the patients showed pathologic ECG, 26% cardiac insufficiency in echocardiography, 31% pathologic X-rays of the thorax and 73% serious pulmonary restriction. Consequently avoiding of anesthetic agents with a high trigger potential for developing malignant hyperthermia (i.e. halothane or muscle relaxants type succinylcholine) prevented severest complications as malignant hyperthermia, rhabdomyolysis or cardiac arrest. Nevertheless other complications (i.e. arrhythmia, cardiac insufficiency) occurred due to the cardiac and pulmonary limitations more pronounced in the older patients of the spine surgery group.

Anesthesia, General↗
PubMed1995

[Infraclavicular vertical brachial plexus blockade. A new method for anesthesia of the upper extremity. An anatomical and clinical study].

Patchy analgesia and incomplete motor blockade sometimes occur during surgery of the upper limb under axillary brachial plexus blockade. To avoid these problems, we sought an alternative approach to the brachial plexus to guarantee reliable anaesthesia. Based on anatomic studies, we undertook a prospective clinical study with 175 patients. METHODS. One hundred seventy-five patients undergoing surgery of the upper limb were anaesthetised using the new technique, based on the results of the anatomic study. We divided the distance between the fossa jugularis and the ventral process of the acromium into two equal parts. An exactly vertical puncture was made using an electrical stimulation cannula and nerve stimulator set at 1.0 mA until muscle contractions were noted in the area to be operated. The current was then progressively reduced to at least 0.3 mA; 400 mg Prilocaine 1% and 50 mg bupivacaine 0.5% were applied in a single injection. RESULTS. Operability was achieved in 94.8% of patients within an average time of 13.5 min after injection (minimum 5 min, maximum 30 min). The tourniquet was tolerated in all cases. For sedation or analgesia, 32.5% required no drugs, 57.1% received low doses of hypnotics (< 5 mg midazolam) as desired, and 5.2% required systemic analgesia due to patchy anaesthesia. In 5.2% of cases the block was insufficient and general anaesthesia was administered. Except in these cases, complete blockades were found after surgery. Postoperative analgesia lasted for 3 to 20 h with an average of 8 h. All patients were satisfied with the anaesthesia and would choose this method another time. Venous puncture occurred in 18 cases without significant problems. In 12 cases we observed Horner's syndrome. No arterial or pleural injury was observed. CONCLUSIONS. Infraclavicular vertical brachial plexus blockade represents a highly successful method compared to other common techniques. Tolerance of the upper arm tourniquet for even longer periods also demonstrates the effective anaesthesia. Other important advantages include a very rapid onset of complete neural blockade and long-lasting postoperative analgesia. The method had low risks and high acceptance by both patients and anaesthesists.

Arm↗
PubMed1993

Reactivity of plasma glutathione peroxidase with hydroperoxide substrates and glutathione.

We studied enzyme kinetics parameters of plasma glutathione peroxidase (GSHPx-P) and the major cellular enzyme, GSHPx-1, for the substrates, H2O2, linoleic acid hydroperoxide (LinOOH), and glutathione (GSH). The major objectives were to determine whether the relatively slow GSHPx-P enzyme had a lower reactivity with hydroperoxides or with GSH and to identify favored hydroperoxide substrates. The rate constants describing the reactivity of human GSHPx-P and human GSHPx-1 with LinOOH and H2O2 are in the same range; GSHPx-P is more reactive with LinOOH and GSHPx-1 is more reactive with H2O2. GSHPx-P also has a low level of reducing activity toward cholesterol 7 alpha-OOH and no detectable activity with the 5 alpha-OOH isomer in contrast to phospholipid hydroperoxide glutathione peroxidase (PHGPx) which readily reduced both isomers. GSHPx-P catalytic activity toward phospholipid hydroperoxides is demonstrable in the absence of detergents, enhanced at low concentrations by deoxycholate, and strongly inhibited by Triton X-100 and incorporation into liposomes. These properties are the opposite of PHGPx. These results suggest that GSHPx-P largely lacks the membrane interfacial properties of PHGPx. GSHPx-P exhibits a smaller GSH rate constant than GSHPx-1. This property partially explains the slower turnover of GSHPx-P with several hydroperoxide substrates; the low reactivity with GSH is not consistent with efficient GSHPx function in the bulk plasma volume. GSHPx-P kinetic properties suggest that it would function best as a free fatty acid hydroperoxidase in GSH-rich microenvironments. Minimally, the secretion of reduced enzyme would permit it to scavenge free fatty acid hydroperoxides.

Animals↗
PubMed1991

Liquorpheresis (CSF-filtration): an effective treatment in acute and chronic severe autoimmune polyradiculoneuritis (Guillain-Barré syndrome).

In recent years, plasmapheresis has become a well established treatment of acute and chronic polyradiculoneuritis (Guillain-Barré syndrome, GBS). Nevertheless, there are still non-responders and there are particular risks associated with this treatment. Despite all efforts, the duration of severe forms of Guillain-Barré syndrome is still considerable. Inflammation and demyelination start intrathecally. We therefore used liquorpheresis (cerebrospinal fluid filtration) as a new effective therapeutic approach. Our first patient, severely disabled with acute GBS, artificially ventilated, had undergone plasma exchange without effect. Plasma immunoadsorption led only to transient improvement. After several liquorphereses, the patient recovered completely. In three additional patients with acute and two with chronic GBS an improvement of clinical signs in close temporal relation to liquorpheresis was observed. Twice, liquorpheresis was combined with immunoadsorption of cerebrospinal fluid. Liquorpheresis was well tolerated in all cases. This procedure may be effective by eliminating humoral or cell-bound factors responsible for the onset or/and maintenance of inflammation. Further controlled studies are necessary and are in progress.

Acute Disease↗