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Biomedical subjects

R Scherer

Publications and source records attributed to R Scherer.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Intraoperative heat conservation. A lot of hot air?].

Thermoregulation and its impairment by anaesthesia and surgery has recently been brought back into focus by researchers and clinicians. All volatile and IV anaesthetics, opioids, as well as spinal and epidural anaesthesia increase the inter-threshold range of thermoregulation from 0.2 degree C to 4 degrees C between vasodilation and vasoconstriction. Thermoregulatory vasoconstriction and shivering occurs in anaesthetized patients at lower core temperatures than in awake subjects. Following induction of general or spinal/epidural anaesthesia, core temperature decreases significantly due to internal redistribution of body heat from the core thermal compartment to peripheral tissues. About 1 h after induction of general anaesthesia and initial redistribution hypothermia, a real reduction in body heat occurs as heat loss exceeds metabolic heat production. Heat loss is further increased due to low operating room temperatures, evaporation from open body cavities, and cold IV fluids. Peripheral thermoregulatory vasoconstriction is triggered by core temperatures between 33 degrees C and 35 degrees C, and is able to slow heat loss. However, body heat content continues to decrease even though core temperatures remain nearly constant. During spinal or epidural anaesthesia thermoregulation remains intact in the unblocked body segments, leading to reduced real heat loss when compared to general anaesthesia. Inadvertent hypothermia markedly decreases drug metabolism. Coagulation is impaired by cold-induced defects of platelet function. Hypothermia reduces neutrophil phagocytosis and oxidative killing capacity, causing wound infections. Postoperative hypothermia represents an unnecessary stress for the circulatory system, elevating plasma catecholamines and leading to myocardial ischaemia and arrhythmias. These hypothermia-related morbidities therefore have consequences reaching fare into the postoperative period. Prevention of inadvertent hypothermia is always indicated. Forced-air warming is the most effective and safest method to prevent perioperative hypothermia.

Body Temperature↗
PubMed1997

The influence of antithrombin III (AT III) substitution to supranormal activities on systemic procoagulant turnover in patients with end-stage chronic liver disease.

OBJECTIVE: Since antithrombin III (AT III) substitution to normal activities could not be shown to have major beneficial effects in patients with end-stage chronic liver disease in a variety of clinical settings, we tested the hypothesis that substitution to supranormal activities decreases systemic procoagulant turnover better in this patient group. DESIGN: Controlled prospective clinical study. SETTING: Operating rooms at a University Hospital. PATIENTS: Twenty-four patients with histologically verified liver cirrhosis consecutively scheduled for liver transplantation. INTERVENTIONS: Nineteen patients were given an antithrombin III concentrate to achieve either 100% (n = 10) or 175% (n = 9) AT III activity. Control patients (n = 5) received saline 0.9% instead. MEASUREMENTS AND RESULTS: Molecular markers of coagulation activation, platelet count and aggregability, and global coagulation variables were measured prior to AT III infusion and 60 min thereafter. In both AT III-treated groups thrombin-antithrombin III-complex increased significantly (p < 0.005), whereas prothrombin fragment F1 + 2, soluble fibrin and D-dimer concentrations, as well as other variables, did not show major changes. CONCLUSIONS: Despite thrombin inhibition by AT III in patients with end-stage chronic liver disease, systemic procoagulant turnover was not significantly decreased 60 min after AT III application even to supranormal activities. Replenishment of the inhibitory antithrombin III pool, decreased in chronic liver disease, should not be expected to slow down the baseline consumptive component of the haemostatic disorder in this patient group.

Adult↗
PubMed1997

[Post-traumatic cerebrospinal rhinorrhea].

PURPOSE: Since frontobasal fractures after severe head trauma may cause serious late-term complications such as meningitis, their recognition and operative treatment are essential. Therefore, we analysed the importance of rhinoliquorrhoea as an early symptom of such fractures by comparison with neuroradiological methods. MATERIAL AND METHODS: In all patients undergoing operative revision of frontobasal fractures during a 7-year period, the clinical symptoms, results of neuroradiological examinations, concomitant injuries, as well as operative results, were studied retrospectively. RESULTS: 45 patients out of 688 with severe head injury showed frontobasal fractures (6.5%). The most common cause of these injuries were traffic accidents (55%) and precipitated falls or plunges (35%). Posttraumatic rhinoliquorrhoea was seen in 41 of 45 patients (91%), and 30 showed external periorbital injuries (66%). In 8 patients (18%) the frontobasal fractures could not be visualised by facultatively performed neuroradiological methods (coronary CT-scan, CT-cisternography, subarachnoid space scintigraphy). 15 patients (33%) were secondarily transferred to our institution, two of them more than two years after the causative injury. All patients were operated on successfully within 14 days after admission. CONCLUSION: Traffic accidents and precipitated falls or plunges are the main causes of head injuries with frontobasal fractures and about 2/3 of these patients show external periorbital injuries. Rhinoliquorrhoea as an early symptom allows diagnosis of frontobasal fractures in 90% of all cases rather than neuroradiological methods which failed to demonstrate frontobasal fractures in about 20% of our patients. Therefore, recognition of rhinoliquorrhoea in patients with severe head injury is essential.

Adolescent↗
PubMed1997

Participation in the Ischemic Optic Neuropathy Decompression Trial: sex, race, and age.

BACKGROUND: The Ischemic Optic Neuropathy Decompression Trial (IONDT) is a randomized, single masked, multicenter trial designed to assess the safety and efficacy of optic nerve decompression surgery compared with careful follow-up in patients 50 years or older with non-arteritic anterior ischemic neuropathy (NAION). OBJECTIVES: To examine and evaluate the sex, race, and age distributions of the screened, and subsequently enrolled, IONDT population, especially the proportions of female, minority, and elderly patients, and demographic characteristics of clinical center investigators, the geographical location of IONDT Clinical Centers, and the referral patterns of local physicians. SETTING: Twenty-five U.S. clinical centers. PARTICIPANTS: There were 1,681 referrals to the Clinical Centers; an Eligibility Screening Form providing demographic information was completed for 1,152. FINDINGS: Forty-three percent (495/1,152) of screened cases were women. Seven percent (85/1,152) were minorities: 33 African-Americans, 34 Hispanics, 17 Asians, and 1 Native-American. The average age was 66 +/- 10 years with a range of 22-92 years of age. Of the 1,152 referred patients, 305 were eligible for randomization; 258 (85%) of these agreed to participate in the trial. The demographic makeup of the randomized IONDT patients was similar to that of the screened population. CONCLUSIONS: Women and the elderly are well represented in the IONDT. Because the number of participating minorities was low, we cannot reliably assess their level of participation. Both a low incidence of NAION in minorities and a low referral rate of minorities to clinical trials are plausible explanations for our findings.

Adult↗
PubMed1996

[Percutaneous puncture technique for portofemorosubclavicular venovenous bypass in orthotopic liver transplantation].

UNLABELLED: Portofemoro-axillary bypass systems are commonly used to treat adverse haemodynamic effects during the anhepatic phase of orthotopic liver transplantation (OLT). However, low shunt flows may reduce the efficacy of these bypass systems. In order to improve veno-venous bypass management, a percutaneous cannulation technique (PCT) was used to insert large-bore catheters (21 F) into the left femoral and subclavian veins. This study prospectively addresses the complications of the PCT in 195 adult patients undergoing 203 OLTs. METHODS: The left femoral and subclavian veins were cannulated preoperatively with 21 F single-lumen catheters (DLP, Grand Rapids, MN, USA) using a Seldinger technique. Intra-operatively, the centrifugal pump (Biopump, Biomedicus, Minnesota, USA) and the portal part of the bypass were connected with the femoral and subclavian catheters. Coagulation profiles, shunt flows, haemodynamic parameters, and complications during OLT associated with the bypass system were recorded. RESULTS: Percutaneous cannulation of the left subclavian and femoral veins was successful in 198 (97.6%) patients. Mean portofemoro-subclavian shuntflow was 4.3 (SD 1.3 l min-1). Although cardiac index (shunt 3.91 [SD 1.1] vs pre-shunt 4.42 [SD 1.0] l min-1 m-2, P < 0.05) and oxygen delivery (shunt 496 [SD 111] vs. pre-shunt 562 [SD 153] ml ml-1.m-2, P < 0.05) were not maintained at pre-shunt levels, renal perfusion pressure stayed above 50 mm Hg during the anhepatic phase. Two intra-operative air embolism (0.98%) and one myocardial infarction (0.49%) at the beginning of the anhepatic phase were observed. There were no bleeding complications. CONCLUSIONS: The portofemoro-subclavian bypass can be performed by percutaneous cannulation without additional complications in patients undergoing OLT. Although haemorrhagic complications following central venous catheterisation are reported to occur in patients with haemostatic defects, none of them was observed in this study. Two events of air embolism and one cardiac arrest could not be related to the PCT. In conclusion, femoro-subclavian percutaneous cannulation is a simple, rapid, and safe alternative to commonly used veno-venous bypass systems.

Adult↗
PubMed1996

[Anxiolysis, sedation, and stress reduction following oral premedication with midazolam in adults. A comparison with dipotassium clorazepate and placebo].

Benzodiazepines are the most commonly used anxiolytic agents. Among the benzodiazepines, midazolam has the advantage of a short elimination half-life, which is especially useful in outpatient surgery. However, in contrast to other commonly prescribed benzodiazepines, such as chlorazepate dipotassium, oral premedication with midazolam has not been thoroughly investigated. Therefore, the present study was performed to compare anxiolysis, sedation and stress reduction with midazolam and clorazepate dipotassium in adults. METHODS. After IRB approval and informed consent had been obtained, 85 patients scheduled for breast biopsy were studied. The patients were chosen at random to receive either 7.5 mg midazolam (n = 29), 20 mg clorazepate dipotassium (n = 28) or placebo (n = 28) preoperatively. Before premedication, immediately prior to surgery and postoperatively in the recovery room, the following parameters were determined with visual analogue scales (VAS): "asthenia," "depression," oral salivation, muscle tension, motoric restlessness and sweating of the palms. In addition, anxiety (STAI-G-X-1, Spielberger), heart rate and arterial blood pressure were measured. Before patients underwent surgery, the degree of sedation was evaluated by the anaesthesiologist. RESULTS. Clorazepate dipotassium and midazolam both caused a reduction in anxiety as compared with the placebo (P < 0.05). Only clorazepate dipotassium reduced anxiety postoperatively (P < 0.05). Neither midazolam nor clorazepate dipotassium caused a reduction in "asthenia" and "depression." Midazolam was more effective in preventing increased blood pressure than clorazepate dipotassium and the placebo (P < 0.05). Furthermore, after premedication with midazolam, salivation, muscle tension, motoric restlessness and sweating of the palms remained stable, in contrast to the results after premedication using clorazepate dipotassium or placebo (P < 0.05). CONCLUSIONS. The anxiolytic effects of 7.5 mg midazolam and 20 mg clorazepate dipotassium were similar after oral application. However, the anxiolytic effect of midazolam is shorter-lived than that of clorazepate dipotassium. In contrast to clorazepate dipotassium, midazolam produced no increase in arterial blood pressure and stabilized oral salivation, production in the palms, muscle tension and motoric restlessness.

Adult↗
PubMed1996

Velocity distributions in glottal models.

Velocity distributions within three models of the human larynx, namely, a rigid plexiglas model, an excised canine larynx, and a computational model are investigated with experimental and theoretical analyses. A plexiglas wind tunnel with interchangeable glottal constrictions was used as a two-dimensional steady-flow model to measure velocity and pressure for various glottal shapes. A canine excised larynx was used as a prototype pulsatile flow model to study pressure and velocity variations during phonation. Results of the plexiglas modelling indicated a parabolic laminar velocity profiles upstream of the glottal constriction and turbulent and asymmetric velocity profile downstream of the glottal constriction. The time-averaged velocities of the excised larynx had similarities with the plexiglas model results, and instabilities and asymmetries were also demonstrated by the computational method.

Animals↗
PubMed1996

[Integrated concept for implementing clinical training in emergency medicine].

Since 1993 special lectures in emergency medicine are part of curriculum in the study of medicine at German universities. To intensify practical teaching in this field an integrative concept was followed in performing emergency training, the experiences of which are described in this paper. Seminars dealing with the most important subjects of preclinical care were combined with practical training blocks such as attendance at operations of the preclinical emergency physician service, resuscitation training using computerised resuscitation models (Mega Code), and an anatomical training course for endotracheal intubation, coniotomy, thoracic drainage, or central venous catheterisation on a corpse. If supported by physicians, senior students may supervise groups of 4 to 5 students during the Mega Code training in a tutorial system, thus allowing to intensify practical education. Since the integrative concept is based on cooperation of different medical specialties, the students expect one or two physicians to be chiefly responsible for the entire course. Additional dates during the semester interfere with the students' leisure activities and require individual practical activity. This means giving up a passively receptive attitude. However, as reflected by the results of the exams and questionnaires, response to this step of improvement in Emergency Medical Education has been very positive. Future efforts are directed at including more physicians as practical supervisors, scattering of training dates, an increase in compulsory practical participation such as one-day attendance at an intensive care unit, and intensified exams on practical issues. However, the improvement of the quality of teaching is imperative in the job planning of the medical profession.

Clinical Clerkship↗
PubMed1996

Coefficient of variation: a powerful Doppler ultrasonographic parameter for detection of renal artery stenosis.

The aim of our study was to objectively compare the effectiveness of various Doppler parameters in the diagnosis of renal artery stenosis. In three sheep, variable degrees of renal artery stenosis were induced and renal segmental arteries were investigated using pulsed Doppler sonography. In each animal the standard deviation of the instantaneous peak velocity within one cardiac cycle normalized by the mean peak velocity (coefficient of variation) had significantly higher normalized regression coefficients (k* = -0.215, average of three animals) when compared to resistive index (k* = -0.090) and acceleration index (k* = -0.069). In each individual animal, coefficient of variation detected lower pressure gradients (6.3 mm Hg, average value) than did resistive index (13.4 mm Hg) or acceleration index (17.3 mm Hg). The coefficient of variation may detect the presence of pressure gradients in renal artery stenosis more accurately than acceleration index or resistive index.

Animals↗
PubMed1996

[Use of continuous veno-venous high volume hemofiltration (CVVHVH) in patients with multiple organ failure. Principle and applications].

Between 1987 and 1994 in 24 patients suffering from multiple organ failure the new method of continuous high-volume veno-venous hemofiltration (HVCVVH) was performed. Compared with the usual methods of dialysis and hemofiltration the HVCVVH has proven two advantages: at first, it was possible to obtain a high blood flow through the filter powered by a pump. Secondly the fluid withdrawal from the infracardiac body region and the controlled infusion of fluid into the supracardiac veins was possible without decreasing the cardiac preload in patients with severe disorders of volume distribution. 18 of 24 treated patients had a stable circulation without need of catecholamines after the filtration. In 14 of the 24 patients the FiO2 was reduced to 0.3 and decreased during filtration. 13 patients survived the observation time of 30 days, 2 patients died during the procedure of filtration.

Adult↗
PubMed1995

Influence of epidural analgesia on fetal and neonatal well-being.

Epidural analgesia is a frequently used method to reduce the pain of child-bearing. Concerns regarding the safety and potential hazards still persist in the medical community. This review intends to examine how epidural analgesia determines the various factors of fetal and neonatal well-being. Placental drug transfer of opiates like morphine, pethidine and fentanyl is rapid and can lead to neonatal depression. Sufentanil seems to be the safest opiate to administer epidurally. Local anaesthetics are transferred to the fetus in substantial amounts, but the reported effects are subtle and are probably inconsequential. Utero- and fetoplacental blood flow seems to be improved by epidural analgesia with local anaesthetics. Even when using stronger solutions for more extensive blockade in patients for caesarean section, no adverse effects could be demonstrated using pulsed Doppler technique as long as prolonged hypotension (> 2 min) is avoided. Hypotension is best prevented with 20-25 ml/kg crystalloid preload and prompt treatment with ephedrine or etilephrine. Addition of adrenaline to local anaesthetics is considered to be safe for the healthy mother and fetus but it should best be avoided in mothers with pregnancy induced hypertension. Fetal and neonatal acid-base balance and gas-exchange are not adversely affected by epidural analgesia. Many studies show that epidural analgesia can indeed protect the fetus if hypotension is prevented. Neonatal well-being evaluated by APGAR, BRAZELTON, SCANLON and NACS scores is not significantly influenced by local anaesthetics. Neonatal depression can occur however with epidural use of morphine, fentanyl and alfentanil. Sufentanil, again in doses up to 30 micrograms in association with bupivacaine seems to be devoid of depressive effects on the neonate. In summary, the anaesthetist has good arguments to reassure his obstetrical colleagues that providing epidural analgesia for pregnant women in labour is a justifiable intervention to support the natural process of child-bearing.

Analgesia, Epidural↗
PubMed1995

A clinical monitoring system for centrifugal blood pumps.

In clinical application of rotary blood pumps, flow obstruction as a result of suction of the inflow cannula, kinking of tubing, or thrombus formation occurs quite frequently. Early detection of such problems is essential to avoid hemolysis, tissue degradation, or release of thrombi to the patient. A program was developed for automatic observation of pump performance, tubing resistance, and suction effects, which requires only the measurement of already available parameters (i.e., pump speed, pump flow, aortic pressure). The software is based on Visual-C and provides a user surface formatted in Windows. Pump flow, its time derivate, and the relationship between the pulsatile component and the mean graft flow are observed to detect suction in the left atrium. Furthermore, the generated pressure head is predicted from pump speed, graft flow, and the resistance of tubing/cannula and compared with the actually measured aortic pressure. An alarm sounds if a given limit between prediction and measurement is exceeded. In a mock circulation, suction events were detected in more than 95% with a mean deviation of actual aortic pressure from its predicted value of less than 5%. For in vivo application, even incomplete suction could be detected reliably in more than 90% of events. This system improves and standardizes monitoring of pump performance; it should therefore lead to greater safety during application of such devices.

Algorithms↗
PubMed1995

Intrarenal Doppler ultrasonography: which vessel should be investigated?

The aim of our study was to determine whether the site of intrarenal Doppler measurement influences diagnosis of renal artery stenosis. In an experimental test, three sheep with variable degrees of renal artery stenosis were investigated. In each animal, the resistive index from renal segmental arteries correlated better with mean pressure gradient (r = 0.85, 0.71, 0.85) and had lower standard deviation (s = 0.02 to 0.05) than resistive index from interlobar arteries (r = 0.48, 0.54, 0.61) (s = 0.03 to 0.11). In two animals the difference was significant (correlation: P < or = 0.01, P = 0.13, P < or = 0.05; standard deviation: P < or = 0.01, P < or = 0.34, P < or = 0.05). For detecting renal artery stenosis, vessels within the renal sinus should be used for Doppler sampling.

Animals↗
PubMed1995

Extracellular matrix proteins in human bile and gallstones.

OBJECTIVE: To investigate the presence of extracellular matrix (ECM) proteins in human bile and gallstones and to determine whether they play a role in gallstone formation. METHODS: ECM components [procollagen-III-peptide (P-III-P), laminin, and hyaluronic acid] in bile from patients with (n = 22) and without (n = 6) gallstone disease were investigated by immunoassay. Bile, gallstones, and serum were assayed for extracellular matrix components in an additional 19 patients with gallstone disease and gallstones were analysed in a third set of 26 patients. The expression of hyaluronic acid synthetase in bile duct and gall bladder epithelia was investigated by immunocytochemistry. RESULTS: Hyaluronic acid levels were significantly elevated in hepatic and gall bladder bile, but not in the serum of patients with compared with those without gallstone disease (137 versus 81 micrograms/l, respectively; P < 0.05). No differences were found between hepatic and gall bladder bile. Procollagen-III-peptide and laminin were detected in the hepatic bile of patients in both groups. Laminin levels were higher in gall bladder bile than in serum in all patients and measurable amounts of hyaluronic acid were found in gallstones. The amount of hyaluronic acid was inversely correlated to the volume of the gallstone, i.e., the smallest gallstones contained the highest levels of hyaluronic acid. No procollagen-III-peptide or laminin was found in the gallstones. Immunocytochemistry of the epithelial cells of bile duct and gall bladder mucosa stained strongly for hyaluronic acid synthetase. CONCLUSIONS: Hyaluronic acid as a progenitor of ECM can be detected in bile and is significantly elevated in patients with gallstone disease. Small gallstones contain more hyaluronic acid than large stones, suggesting that hyaluronic acid may play a role in gallstone formation, particularly since it is produced by the epithelial lining of bile ducts and is found in gall bladder mucosa.

Adolescent↗
PubMed1994

Identifying relevant studies for systematic reviews.

OBJECTIVE: To examine the sensitivity and precision of Medline searching for randomised clinical trials. DESIGN: Comparison of results of Medline searches to a "gold standard" of known randomised clinical trials in ophthalmology published in 1988; systematic review (meta-analysis) of results of similar, but separate, studies from many fields of medicine. POPULATIONS: Randomised clinical trials published in 1988 in journals indexed in Medline, and those not indexed in Medline and identified by hand search, comprised the gold standard. Gold standards for the other studies combined in the meta-analysis were based on: randomised clinical trials published in any journal, whether indexed in Medline or not; those published in any journal indexed in Medline; or those published in a selected group of journals indexed in Medline. MAIN OUTCOME MEASURE: Sensitivity (proportion of the total number of known randomised clinical trials identified by the search) and precision (proportion of publications retrieved by Medline that were actually randomised clinical trials) were calculated for each study and combined to obtain weighted means. Searches producing the "best" sensitivity were used for sensitivity and precision estimates when multiple searches were performed. RESULTS: The sensitivity of searching for ophthalmology randomised clinical trials published in 1988 was 82%, when the gold standard was for any journal, 87% for any journal indexed in Medline, and 88% for selected journals indexed in Medline. Weighted means for sensitivity across all studies were 51%, 77%, and 63%, respectively. The weighted mean for precision was 8% (median 32.5%). Most searchers seemed not to use freetext subject terms and truncation of those terms. CONCLUSION: Although the indexing terms available for searching Medline for randomised clinical trials have improved, sensitivity still remains unsatisfactory. A mechanism is needed to "'register" known trials, preferably by retrospective tagging of Medline entries, and incorporating trials published before 1966 and in journals not indexed by Medline into the system.

Abstracting and Indexing↗
PubMed1994

[The value of duplex sonography after orthotopic liver transplantation. Experience with 44 patients].

In a prospective study, 44 patients (11 women, 33 men) who had received orthotopic liver transplants underwent a total of 196 consecutive duplex Doppler ultrasound examinations. The aim of the study was to evaluate the correlation between the pulsatile flow index (PFI) and the damping index (DI) as far as complications as rejection or cholangitis were concerned. The patients were examined five times each on average. The PFI and DI were measured in the hepatic artery, the portal vein and the hepatic veins. The findings were compared with the clinical course (cholangitis, rejection) and the histomorphological diagnosis as determined in biopsy specimens. In biopsy-proven rejection episodes, the sensitivity of the PFI in the hepatic artery was 69.4%, the specificity 72.2%. The sensitivity of the DI in the hepatic vein was 89.4%, the specificity 89.1%. Combining the two, specificity was more than 90%. PFI and DI in the portal vein bore no apparent relation to clinical course or histomorphological diagnosis. We found duplex Doppler ultrasound extremely beneficial in determining the timing and indication for liver biopsy. In addition, this simple examination, which can be performed as often as desired, accurately shows the transplanted liver's response to measures taken to counter rejection.

Adult↗
PubMed1994

Comparison of histidine-tryptophan-ketoglutarate (HTK) solution versus University of Wisconsin (UW) solution for organ preservation in human liver transplantation. A prospective, randomized study.

Over a 30-month period, 60 patients (30 in each group) suffering from end-stage liver disease or primary hepatic malignancy and scheduled for liver transplantation were enrolled in a prospective, randomized study to compare two methods of liver preservation: histidine-tryptophan-ketoglutarate (HTK) solution versus University of Wisconsin (UW) solution. Entry criteria for both groups were: age (18-65 years), elective surgery (transplantable or urgent category of the recipients), first transplantations and harvesting procedure performed by the same team. The parameters under investigation were the clinical and laboratory data pre- and post-transplantation, as well as follow-up data such as complications and survival. There were no significant differences in the two groups as far as the evaluation criteria were concerned, even when cold ischemia time was more than 15 h (n = 7). A slight, yet not significant, increase in late complications of the biliary anastomoses could be seen in the UW group. Hepatocellular injury (SGOT, SGPT, GLDH, lactate) appeared to be more marked in the HTK group. These results suggest that both HTK and UW solutions are appropriate for clinical use in liver transplantation, even if cold ischemia time is more than 15 h.

Adenosine↗