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S Piepenbrock

Publications and source records attributed to S Piepenbrock.

At least 55 records · Page 3Linked to original sources
PubMed2001

Postoperative reading speed does not indicate implicit memory in elderly cardiac patients after propofol and remifentanyl anaesthesia.

BACKGROUND: A recent study in young patients undergoing propofol-alfentanil-nitrous oxide anaesthesia demonstrated implicit memory for stories presented during operation using a postoperative reading speed task. In this study we investigated whether patients who tolerate only small amounts of anaesthetics are prone to develop implicit and explicit memories about intraoperative events. METHODS: Thirty patients with poor physical status (ASA III-IV) undergoing cardioverter defibrillator implantation were included in the study. Patients were premedicated with intravenous midazolam and anaesthesia was maintained using propofol and remifentanil infusions. During surgery one of two audio-tapes containing two short stories was played to the patients. Reading speed for the stories played during surgery and two similar stories from the other tape was tested 4 h later. Explicit memory was tested at 4 h and 24 h after audiotape presentation using a structured interview and a forced-choice recognition test pertaining to the story content. Thirty additional awake subjects served as controls. RESULTS: Although half of the patients seemed to be awake one or more times during the operation, no explicit memories of intraoperative events were reported. The forced-choice recognition of the stories was at chance level. No effect on reading speed was found in either the patients or the control subjects. CONCLUSIONS: The possible reasons for reduced explicit and implicit memory performance in elderly patients are age and poor physical status of the patients and the modality change between study and test phases. A non-anaesthetised control group of the same age and physical status should therefore be included in all studies of implicit memory.

Acoustic Stimulation↗
PubMed2001

Effects of different preparations of propofol, diazepam, and etomidate on human neutrophils in vitro.

BACKGROUND: Intravenous anaesthetics and sedatives can influence polymorphonuclear cell (PMN) functions. Some of the drugs for sedation and anaesthesia have been alternatively dissolved in lipid solutions containing medium (MCT) and/or long chain (LCT) triglycerides. The in vitro effects of two different diazepam (benzyl-alcohol, LCT/MCT), etomidate (propylene-glycol, LCT/MCT), and propofol (LCT, LCT/MCT) preparations on respiratory burst (RB) and phagocytosis of human PMNs were studied. METHODS: Diazepam (2, 20 microg ml(-1)), etomidate (0.5, 5 microg ml(-1)), and propofol (6, 60 microg ml(-1)) were investigated in clinical and 10-fold concentrations with flow cytometric assays. The RB was measured with the fluorescent dye rhodamine after induction with Escherichia coli or formyl-methionyl-leucylphenylalanine (FMLP) following priming with tumour necrosis factor alpha (TNF-alpha). Phagocytosis of PMNs was carried out in whole blood after incubation with fluorescein-labelled E. coli. RESULTS: LCT-propofol at 60 microg ml(-1) reduced the percentage of PMNs with RB activity after induction with E. coli (52.8+/-20.4) and TNF-alpha/FMLP (10.8+/-5.1)) as well as the percentage of phagocytosing PMNs (48.9+/-19.5) in contrast to LCT/MCT-propofol, which augmented all parameters (85.4+/-10.1, 50.3+/-12.7, 66.5+/-12.5). Also the higher concentrations of LCT/MCT-diluted etomidate and diazepam increased the percentage of RB positive PMNs compared to the alternative compositions. The percentage of phagocytosing PMNs was less reduced with 20 microg ml(-1) LCT/MCT-diazepam (85.2+/-6.9) than with the same concentration of benzyl-alcohol diluted diazepam (68.8+/-12.2) compared to the control. CONCLUSION: The in vitro effects of diazepam, etomidate, and propofol are dependent on the solvent applied. The tested LCT/MCT preparations reduce the inhibitory effects on the bacterial killing capacity of PMNs found after incubation with propyleneglycol, benzyl-alcohol, or LCT preparations, respectively.

Anesthetics, Intravenous↗
PubMed2001

Structural requirements for voltage-dependent block of muscle sodium channels by phenol derivatives.

We have studied the effects of four different phenol derivatives, with methyl and halogen substituents, on heterologously expressed human skeletal muscle sodium channels, in order to find structural determinants of blocking potency. All compounds blocked skeletal muscle sodium channels in a concentration-dependent manner. The methylated phenol 3-methylphenol and the halogenated phenol 4-chlorophenol blocked sodium currents on depolarization from -100 mV to 0 mV with IC(50) values of 2161 and 666 microM respectively. Methylation of the halogenated compound further increased potency, reducing the IC(50) to 268 microM in 2-methyl-4-chlorophenol and to 150 microM in 3,5-dimethyl-4-chlorophenol. Membrane depolarization before the test depolarization increased sodium channel blockade. When depolarizations were started from -70 mV or when a 2.5 s prepulse was introduced before the test pulse inducing slow inactivation, the IC(50) was reduced more than 3 fold in all compounds. The values of K(D) for the fast-inactivated state derived from drug-induced shifts in steady-state availability curves were 14 microM for 3,5-dimethyl-4-chlorophenol, 19 microM for 2-methyl-4-chlorophenol, 26 microM for 4-chlorophenol and 115 microM for 3-methylphenol. All compounds accelerated the current decay during depolarization and slowed recovery from fast inactivation. No relevant frequency-dependent block after depolarizing pulses applied at 10, 50 and 100 Hz was detected for any of the compounds. All the phenol derivatives that we examined are effective blockers of skeletal muscle sodium channels, especially in conditions that are associated with membrane depolarization. Blocking potency is increased by halogenation and by methylation with increasing numbers of methyl groups.

Cell Line↗
PubMed2001

Effects of colloidal resuscitation fluids on the neutrophil respiratory burst.

BACKGROUND: Experimental studies have revealed that gelatin and HES produce increased neutrophil respiratory burst activity. It was investigated whether 3-percent gelatin (MW 35,000) and three types of 6-percent HES (MW 70,000; degree of substitution, 0.5; 200,000/0.5; 450,000/0.7) preparations can influence superoxide anion production during respiratory burst under clinical conditions. STUDY DESIGN AND METHODS: Blood samples were obtained from 40 patients before and 1 hour after the infusion, before anesthesia and surgical treatment. After stimulation with bacteria (Escherichia coli), the respiratory burst was measured by oxidation of nonfluorescent dihydrorhodamine 123 to the fluorescent rhodamine 123 by the use of flow cytometry. RESULTS: Respiratory burst activity decreased significantly (p = 0.004) from the baseline (60.0 +/- 6.5%) to 1 hour after the administration of the low-molecular-weight HES preparation (55.0 +/- 6.8%). No significant differences in respiratory burst activity could be found after the administration of gelatin or medium-molecular-weight or high- molecular-weight HES solution. CONCLUSION: The investigated administration of gelatin and medium- and high-molecular-weight HES preparations did not influence respiratory burst activity under clinical conditions. However, the neutrophil respiratory burst was impaired after the administration of low-molecular-weight HES. Neutrophil respiratory burst activity may vary according to the type of colloidal plasma substitutes administered.

Adult↗
PubMed2001

[Bilateral monitoring of cerebral oxygen saturation in aortic arch surgery].

Cerebral ischemia with consecutive neurological damage is a typical complication in aortic arch surgery. Therefore, intraoperative neuromonitoring is of increasing interest. This paper describes the role of bilateral near-infrared-spectroscopy (NIRS) in detecting cerebral ischemia. In the case of a patient with acute aortic dissection (Daily, type A), an unexpected sudden reduction of perfusion of the right carotid artery could easily be detected with the help of two instruments INVOS 3100A. The decrease in the saturation values from 74% to 54% correlated well with the drop of blood pressure in the right radial artery. Clamping of the aorta with interruption of the blood flow into the innominate artery through the false lumen was the reason for the low cerebral perfusion. After repositioning the aortic clamp NIRS in combination with invasive blood pressure monitoring sufficiently allowed to control the further course of cerebral perfusion. The NIRS is a non-invasive, easy to handle, and easy to interpret method for intraoperative monitoring of the neurological status. Therefore in our opinion it has got some relevant advantages in contrast to other neuromonitoring methods in aortic arch surgery.

Aortic Dissection↗
PubMed2001

Propofol blocks human skeletal muscle sodium channels in a voltage-dependent manner.

UNLABELLED: Propofol decreases muscle tone in the absence of neuromuscular blocking drugs. This effect probably cannot be attributed solely to central nervous depression. We studied the effects of propofol on heterologously expressed skeletal muscle sodium channels. Our hypothesis was that the decrease in muscle tone may partly be attributed to an interaction of propofol with sarcolemmal sodium channels. Cells were voltage clamped and whole-cell sodium inward currents were recorded in the absence and presence of propofol. When depolarizing pulses to 0 mV were started from a holding potential close to the normal resting potential of muscle (-70 mV), or when a 2.5-s prepulse inducing slow inactivation was applied before the test pulse at -100 mV, a significant reduction in the peak current amplitude was achieved by 10 and 5 microM propofol, respectively (P < 0.001). Half-maximum blocking concentrations with these protocols were 23 and 22 microM. Blocking potency increased at depolarized membrane potentials with the fraction of inactivated channels; the estimated dissociation constant K(d) from the inactivated state was 4.6 microM. These results suggest that propofol significantly blocks sarcolemmal sodium channels at clinically relevant concentrations while maintaining potentials close to the physiological resting potential. IMPLICATIONS: Voltage-gated sodium channels mediate the initiation and propagation of action potentials along the sarcolemma. Results from our study show that those channels are targeted and blocked in a concentration- and voltage-dependent manner by propofol. This mechanism may contribute to the reduction in muscle excitability.

Action Potentials↗
PubMed2001

Using intranasal midazolam spray to prevent claustrophobia induced by MR imaging.

OBJECTIVE: Up to 37% of patients undergoing MR imaging examinations experience moderate to severe levels of anxiety that necessitate the termination of the procedure in 5-10% of patients. Although the clinical use of MR imaging has increased, effective procedures to handle claustrophobia are lacking. We evaluated the effectiveness of intranasally administered midazolam spray in preventing claustrophobic responses of patients undergoing MR imaging. SUBJECTS AND METHODS: Fifty-four patients scheduled for MR imaging were included in this prospective study. Anxiety and sedation of patients were evaluated before drug administration, immediately before MR imaging, and at the end of the procedure. The Spielberger State-Trait Anxiety Inventory, the visual analogue scale of anxiety, and a five-point sedation scale were used. Half the patients received intranasal spray applications of 4 mg midazolam, whereas the other patients received a placebo, in a randomized, double-blind study design (six sprayings of 0.5% midazolam solution or NaCl 0.9%, respectively). The intensity of the sensation of burning of the nasal mucosa was rated by patients using a three-point scale (no, slight, or strong burning). The quality of scan images was evaluated by a radiologist using a five-point scale (0 = extremely poor, 5 = excellent). RESULTS: No cancellations occurred with patients who received midazolam, whereas four of 27 patients receiving placebo panicked and terminated the scanning procedure. The initial anxiety and sedation scores did not differ between the groups. Patients who received midazolam spray were more sedated and less anxious immediately before entering the MR scanner and reported a more intense slight transient burning of the nasal mucosa than those in the placebo group. The quality of the MR image was higher in the midazolam group. CONCLUSION: A sizeable reduction in MR imaging-related anxiety and improved MR image quality were seen with patients who received intranasal midazolam spray. With the exception of transient burning of the nasal mucosa, no adverse effects were reported. This simple and safe method is useful in sedating patients for MR imaging and other minor procedures.

Administration, Intranasal↗
PubMed2000

Absorption and hemodynamic effects of airway administration of adrenaline in patients with severe cardiac disease.

BACKGROUND: If intravenous access cannot be attained during resuscitation of adult patients, endotracheal application of at least 2 mg of adrenaline is recommended. However, the effects of this intervention have not yet been demonstrated in adults. OBJECTIVE: To demonstrate the effects of adrenaline administered through the airways. DESIGN: Prospective clinical trial. SETTING: Operating theater at university hospital. PATIENTS: 34 patients receiving implantable cardioverter defibrillators under general anesthesia. INTERVENTION: When mean arterial pressure decreased below 80 mm Hg, 100 times the effective central intravenous dose of adrenaline (mean +/- SD, 1.3+/-0.6 mg [range, 0.7 to 3 mg]) was administered over 5 seconds into the endotracheal tube or through a bronchial catheter. Ten forced ventilations followed. MEASUREMENTS: Hemodynamic variables were recorded with a polygraph recorder. Adrenaline levels were measured in 13 patients. RESULTS: Plasma levels and arterial pressure increased in all patients (P < 0.002). Higher plasma levels (P < 0.039) and greater arterial pressure (P < 0.001) were achieved with this method than with intravenous injection. The effects of adrenaline did not differ between the two airway routes. Sustained ventricular arrhythmia did not occur. CONCLUSION: These substantial effects support the standard recommendation to consider the airways as an alternate route for at least 2 mg of adrenaline during resuscitation.

Absorption↗
PubMed2000

Influence of cold ischemia time, pretransplant anti-porcine antibodies, and donor/recipient size matching on hyperacute graft rejection after discordant porcine to cynomolgus kidney transplantation.

Organs transplanted between phylogenetically disparate species, such as from the pig into the primate, are subject to hyperacute rejection (HAR). This form of xenograft rejection is mediated by preformed natural antibodies and is believed to occur invariably in discordant xenografts thus leading to rapid destruction and complete thrombosis of the graft. Recent data, however, have shown that in the porcine to cynomolgus monkey setting, HAR is not inevitably seen after porcine kidney transplantation. The influence of preoperative antiporcine antibody levels in the recipient, cold ischemia time, and donor organ weight on the onset of HAR was investigated by using unmodified large white pigs (aged 3-12 weeks) as organ donors and adult cynomolgus monkeys (aged 1.5-3.5 years) as recipients. Porcine kidney xenotransplantation was performed in either a non-life-supporting model (n=7) or in a life-supporting model (n=8). In both models, no correlation was found between cold ischemia time and HAR. When preoperative anti-porcine antibody levels were investigated, a significant increase in incidence of HAR was observed in animals with elevated anti-porcine IgM (P<0.05) but not IgG levels (P=NS). Interestingly, although 5 of 12 grafts with an organ weight of less than 50 g underwent HAR, none of three grafts with a donor organ weight of more than 70 g showed signs of HAR. In addition, all three larger grafts showed intraoperative and postoperative urine production, although only in 1 (48 g) of the 12 grafts weighing less than 50 g primary graft function was observed. In one animal, a second porcine kidney (23 g) was successfully transplanted (without HAR) immediately after HAR and subsequent removal of a first porcine kidney (20 g). These results indicate that in the porcine to cynomolgus monkey setting anti-porcine IgM rather than IgG anti-porcine antibody levels seem to be of predominant importance for the induction of HAR. By increasing the donor organ size and weight the frequency of the onset of HAR can be at least reduced. This is most likely due to immunoabsorption of the recipients preformed antibodies in the porcine kidney without lethal damage for the graft.

Acute Disease↗
PubMed2000

Low-dose dopexamine in patients undergoing hemihepatectomy: an evaluation of effects on reduction of hepatic dysfunction and ischaemic liver injury.

BACKGROUND: Hepatic dysfunction is a common problem in patients after hemihepatectomy. Treatment with low-dose dopamine has been shown to be beneficial in hemihepatectomy patients. We hypothesized that dopexamine, a synthetic vasoactive catecholamine, due to its specific pharmocodynamic profile may be more effective in reducing hidden ischaemic episodes in the hepato-splanchnic region during and after temporary total cross-clamping of hepatic inflow in these patients. METHODS: The effects of low-dose dopexamine on hepatic venous haemoglobin oxygen saturation (ShvO2), hepatic venous lactate level, monoethylglycinxylid (MEGX) formation, hepatic synthetic function and indicators for hepatic cell damage were studied during hemihepatectomy and for 16 h postoperatively in hemihepatectomy patients and compared to those of low-dose dopamine. In a prospective, double-blind clinical study 20 patients received randomly either dopexamine (DPX) 0.5 microg kg(-1) min(-1) (n=10) or dopamine (DO) 2.5 microg kg(-1) min(-1) (n= 10). Infusions were started after induction of anaesthesia and continued 16 h postoperatively. Hepatic vein, radial and pulmonary artery were catheterized. Measurements were carried out after induction of anaesthesia, after total cross-clamping of hepatic inflow, and at 2 h and 16 h postoperatively. RESULTS: There were no differences in systemic haemodynamics, oxygenation, ShvO2, serum aminotransferases or MEGX levels between the groups. At 16 h postoperatively prothrombin and antithrombin III levels were significantly lower while hepatic venous lactate was significantly higher in the DPX group compared to the DO group. CONCLUSION: In patients undergoing hemihepatectomy, we could not reveal superior hepatoprotective effects of low-dose dopexamine compared to low-dose dopamine.

Adult↗
PubMed2000

Voltage-dependent blockade of normal and mutant muscle sodium channels by benzylalcohol.

1. We studied the effects of benzylalcohol on heterologously expressed wild type (WT), paramyotonia congenita (R1448H) and hyperkalaemic periodic paralysis (M1360V) mutant alpha-subunits of human skeletal muscle sodium channels. 2. Benzylalcohol blocked rested channels at -150 mV membrane potential, with an ECR(50) of 5.3 mM in wild type, 5.1 mM in R1448H, and 6.2 mM in M1360V. When blockade was assessed at -100 mV, the ECR(50) was reduced in R1448H (2 mM) compared with both wild type (4.3 mM; P<0.01) and M1360V (4.3 mM). 3. Membrane depolarization before the test depolarization significantly promoted benzylalcohol-induced sodium channel blockade. The values of K(D) for the fast-inactivated state derived from benzylalcohol-induced shifts in steady-state availability curves were 0.66 mM in wild type and 0.58 mM in R1448H. In the presence of slow inactivation induced by 2.5 s depolarizing prepulses, the ECI(50) for benzylalcohol-induced current inhibition was 0.59 mM in wild type and 0.53 mM in R1448H. 4. Recovery from fast inactivation was prolonged in the presence of drug in all clones. 5. Benzylalcohol induced significant frequency-dependent block at stimulating frequencies of 10, 50, and 100 Hz in all clones. 6. Our results clearly show that benzylalcohol is an effective blocker of muscle sodium channels in conditions that are associated with membrane depolarization. Mutants that enter voltage-dependent inactivation at more hyperpolarized membrane potentials compared with wild type are more sensitive to inhibitory effects at the normal resting potential.

Amino Acid Substitution↗
PubMed2000

Anaesthesia with midazolam and S-(+)-ketamine in spontaneously breathing paediatric patients during magnetic resonance imaging.

We evaluated safety and efficacy of a sedation technique based on rectal and intravenous S-(+)-ketamine and midazolam to achieve immobilization during Magnetic Resonance Imaging (MRI). Thirty-four paediatric patients were randomly assigned to undergo either the sedation protocol (study group) or general anaesthesia (control group). Imaging was successfully completed in all children. Children in the study group received a rectal bolus (0.5 mg x kg(-1) midazolam and 5 mg x kg(-1) S-(+)-ketamine) and required additional i.v. supplementation (20+/-10 microg x kg(-1) x min(-1) S-(+)-ketamine and 4+/-2 microg x kg(-1) x min(-1) midazolam), spontaneous ventilation was maintained. Transient desaturation occurred once during sedation and four times in the control group (P=0.34). PECO2 was 5.3+/-0.5 kPa (40+/-4 mm Hg) in the study group and 4.1+/-0.6 kPa (31+/-5 mm Hg) in the control group (P<0.001). Induction and discharge times were shorter in the study group (P<0.001), recovery times did not differ significantly between the groups. Our study confirms that a combination of rectal and supplemental intravenous S-(+)-ketamine plus midazolam is a safe and useful alternative to general anaesthesia for MRI in selected paediatric patients.

Administration, Rectal↗
PubMed2000

[In Process Citation]

Early post-operative infections remain the most important cause of morbidity and mortality in patients following orthotopic liver transplantation (OLTx). Since polymorphonuclear neutrophils (PMNs) are one of the major determinants of antimicrobial defence, the alteration of their functions may influence the outcome of infection in these patients. Ciclosporin predominantly used as immunosuppressive drug following organ transplantation inhibits superoxide anion production during respiratory burst (RB) of PMNs. Growth factors have been shown to modulate the RB of PMNs in healthy volunteers. It has been examined whether PMNs from patients under immunosuppression following OLTx can be primed by in vitro administration of interleukin-3 (IL-3), granulocyte-macrophage colony stimulating factor (GM-CSF), and granulocyte colony stimulating factor (G-CSF). For flow-cytometric evaluation, leukocytes were obtained as supernatant following sedimentation and were incubated with IL-3 (500 U ml-1), IL-3 and GM-CSF (500 U ml-1), or IL-3 and G-CSF (500 U ml-1). The RB was measured by intracellular oxidation of non-fluorescent dihydrorhodamine to green fluorescent rhodamine after induction of phorbol 12-myristate 13-acetate (PMA) or a combination of tumour necrosis factor alpha (TNF-alpha) and N-formyl-methionyl-leucyl-phenylalanine (FMLP). Following stimulation with PMA, the RB of patients following OLTx could be increased significantly after priming with the combination of IL-3/G-CSF (p < 0.03); following stimulation with TNF-alpha/FMLP the RB could be increased significantly by IL-3 (p < 0.01), IL-3/G-CSF (p < 0.002), and IL-3/GM-CSF (p < 0.002). Regarding the clinical administration of IL-3, GM-CSF and G-CSF following OLTx, the role of these cytokines for prophylaxis or treatment of early postoperative infections should be further investigated.

Journal Article↗
PubMed2000

Anaesthesiological and criterial care aspects regarding the treatment of patients with arteriovenous malformations in interventional neuroradiology.

In recent years, the neuroradiological treatment of cerebral and spinal arteriovenous malformations (AVMs) has undergone significant evolution and improvement. Endovascular embolisation procedures of AVMs are mainly performed under general anaesthesia. Different pathophysiological characteristics of patients with AMVs must be considered for the choice of the anaesthetic procedures. Anaesthesiological management must aim at maintaining stable intracranial haemodynamics; thus, the drugs used must be evaluated according to their effects on brain perfusion, brain metabolism, and intracranial pressure. Rapid recovery to normal central nervous functions should be obtained postoperatively. Close-meshed neurological surveillance should be exercised in order to detect immediately any alteration of neurological state. In summary, anaesthesiological management of interventional neuroradiology is based on the same well-established principles as anaesthesia in neurosurgery.

Anesthesia, General↗
PubMed2000

Anaesthesia with propofol decreases FMLP-induced neutrophil respiratory burst but not phagocytosis compared with isoflurane.

Propofol has been reported to produce a dose-dependent inhibition of phagocytosis and superoxide anion production during the respiratory burst (RB) of polymorphonuclear cells (PMNs) in vitro. In this randomized, blinded study, these two parameters were compared during propofol or isoflurane anaesthesia in patients undergoing elective interventional embolization of cerebral arterio-venous malformations. Anaesthesia was performed with continuous intravenous propofol 6-8 mg kg-1 h-1 (n = 15) or isoflurane 0.8-1.0% end tidal (n = 15). Heparinized blood was drawn before, and 2 and 4 h after induction of anaesthesia. The RB in isolated leucocytes was measured with the fluorescent dye rhodamine after ex vivo induction by Escherichia coli or tumour necrosis factor alpha/N-formyl-methionyl-leucylphenylalanine (TNF-alpha/FMLP). Phagocytosis was carried out in whole blood after incubation with fluorescein isothiocyanate (FITC)-labelled, opsonized E. coli and also measured with a flow cytometer. The two groups were similar in terms of biometric data and haemodynamic responsiveness. After 4 h of propofol or isoflurane anesthesia, the mean (SD) phagocytosis of E. coli was 93.2% (7.0%) and 94.3% (9.2%), respectively, of that before anaesthesia. The percentage of PMN with RB activity following TNF-alpha/FMLP stimulation was significantly reduced after 2 h (80.9% (24.2%); P < 0.05) and 4 h (53.7% (27.3); P < 0.05) of anaesthesia with propofol compared with the values before induction. This effect of propofol anaesthesia was significantly different from the effect of isoflurane anaesthesia. In contrast to published in vitro results, 4 h of anaesthesia with propofol did not reduce the phagocytotic capacity of human blood PMN more than isoflurane anaesthesia.

Adolescent↗